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Income Taxes - Summary of Income (Loss) Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal	$ (376,152)	$ (113,389)
Foreign	185,608	(55,586)
Loss before income taxes	$ (190,544)	$ (168,975)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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-Name Accounting Standards Codification
-Section 55
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-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 270
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-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 7: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
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Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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-Name Accounting Standards Codification
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-Paragraph 31
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
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-Paragraph 1
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Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
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-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

Fair Value Measurements (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis:


	September 30, 2024
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	113,794	$	—	$	—	$	113,794

Totals	$	113,794	$	—	$	—	$	113,794

Short-term investments:
U.S. government treasury securities	$	4,995	$	—	$	—	$	4,995

Totals	$	4,995	$	—	$	—	$	4,995


	December 31, 2023
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	23,854	$	—	$	—	$	23,854

Totals	$	23,854	$	—	$	—	$	23,854

Short-term investments:
U.S. government treasury securities		93,822		—		—	$	93,822

Totals	$	93,822	$	—	$	—	$	93,822

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis:


	December 31, 2023
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	23,854	$	—	$	—	$	23,854

Totals	$	23,854	$	—	$	—	$	23,854

Short-term investments:
U.S. government treasury securities	$	93,822	$	—	$	—	$	93,822

Totals	$	93,822	$	—	$	—	$	93,822


	December 31, 2022
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	32,641	$	—	$	—	$	32,641

Totals	$	32,641	$	—	$	—	$	32,641

Short-term investments:
U.S. government treasury securities	$	99,036	$	—	$	—	$	99,036
Marketable securities:
Corporate and agency bonds		—		28,667		—		28,667

Totals	$	99,036	$	28,667	$	—	$	127,703

Subsequent Events - Additional Information (Details) - USD ($)		1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
	Nov. 07, 2024	Feb. 29, 2024	Jan. 31, 2024	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	May 15, 2023
Subsequent Event [Line Items]
Percentage of workforce reduction			95.00%
Lease obligations remaining				$ 0		$ 2,600,000	$ 600,000	$ 7,700,000	$ 9,700,000	$ 6,600,000
Common stock, par value				$ 0.0001			$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, par value				$ 0.0001			$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001
2024 SOW under the DMS Agreement \| Forecast
Subsequent Event [Line Items]
Lease obligations remaining					$ 2,900,000
Subsequent Event
Subsequent Event [Line Items]
Percentage of workforce reduction			95.00%
Personnel-related restructuring charges			$ 10,000,000
Decrease in lease payments		$ 5,700,000
Subsequent Event \| Merger Agreement
Subsequent Event [Line Items]
Merger agreement date	Nov. 07, 2024
Common stock, par value	$ 0.0001
Stock option exercise price per share	4
Subsequent Event \| Kalaris Therapeutics, Inc. \| Merger Agreement
Subsequent Event [Line Items]
Common stock, par value	0.00001
Preferred stock, par value	$ 0.00001
Termination fee required to pay	$ 3,480,000
Termination fee required to receive	$ 10,410,000
Subsequent Event \| Restricted Stock Units
Subsequent Event [Line Items]
Awards vesting period			4 years

Income Taxes - Schedule of Income Tax (Benefit) Expense Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Benefit at the federal rate			$ (40,015)	$ (35,472)
Foreign tax rate differential			(15,783)	2,177
State taxes, net of federal benefit			(9,514)	(1,603)
Change in valuation allowance			98,714	35,406
Intercompany note impairment			(34,615)
Tax credits			(5,928)	(6,992)
Officer's compensation			177	695
Stock compensation			4,564	4,637
Impairment of intellectual property			3,003
Permanent differences			79	(182)
Change in state tax law			384
Other			(1,192)	1,069
Total income tax benefit	$ 0	$ 0	$ (126)	$ (265)
Benefit at the federal rate			21.00%	21.00%
Foreign tax rate differential			8.30%	(1.30%)
State taxes, net of federal benefit			5.00%	0.90%
Change in valuation allowance			(51.80%)	(21.00%)
Intercompany note impairment			18.20%
Tax credits			3.10%	4.10%
Officer's compensation			(0.10%)	(0.40%)
Stock compensation			(2.40%)	(2.70%)
Impairment of intellectual property			(1.60%)
Permanent differences			0.00%	0.10%
Change in state tax law			(0.20%)
Other			0.60%	(0.60%)
Total income tax (benefit) expense			0.10%	0.10%

Employee Benefit Plans - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Matching contributions by employer	$ 0.9	$ 0.8

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of Maturities Operating Leases Liabilities

Maturities of operating lease liabilities at December 31, 2023 are as follows (in thousands):


2024		11,842
2025		3,219
2026		3,298
2027		3,376
2028		3,455
Thereafter		5,824

Total lease payments		31,014
Less: interest		3,585

Total lease liability	$	27,429

Lease liability – current	$	10,781
Lease liability – long-term	$	16,648

Sponsored Research, Collaboration and License Agreements - Additional Information (Details) - USD ($)	1 Months Ended			12 Months Ended
	Nov. 30, 2020	Sep. 30, 2018	Jun. 30, 2017	Dec. 31, 2023	Dec. 31, 2022
CPRIT \| License agreement terms
Sponsored Research, Collaboration and License Agreements [Line Items]
Maximum paid percentage of grant award proceeds until which revenue share is payable				400.00%
Royalty payments				$ 0	$ 0
A&R License Agreement \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Non-refundable license fee payments			$ 250,000
Milestone payments				$ 40,000,000
Minimum percentage of eligible to receive tiered royalties				1.00%
Second License Agreement \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Non-refundable license fee payments	$ 125,000
Milestone payments				$ 30,000,000
Minimum percentage of eligible to receive tiered royalties				1.00%
Non-refundable license fee payments, first year through fourth anniversary of effective date				$ 20,000
Non-refundable license fee payments fifth anniversary of effective date and continuing thereafter				40,000
Research Agreement \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Agreement for research activities, term	3 years
Total research activities performing fees, over the term	$ 6,000,000
Collective Agreements \| BCM
Sponsored Research, Collaboration and License Agreements [Line Items]
Research and development expense				$ 2,000,000	$ 2,500,000
Redumption Agreement
Sponsored Research, Collaboration and License Agreements [Line Items]
Earnout payment as percentage of net sales		10.00%
Earnout payment obligation for number of years from first commercial sale		20 years
Minimum earnout payments received by investors for reduction of earnout payment		$ 50,000,000
Period for reduction of earnout payment after first commercial sale		3 years

Stock-Based Compensation (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Research and development	$	312	$	3,254	$	232	$	10,191
General and administrative		4,635		7,214		15,657		20,594

Total stock-based compensation expense	$	4,947	$	10,468	$	15,889	$	30,785

Stock-based compensation expense was as follows:


	Years Ended December 31,
(in thousands)	2023		2022
Research and development	$	13,167	$	14,014
General and administrative		27,612		27,301

Total stock-based compensation expense	$	40,779	$	41,315

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the nine months ended September 30, 2024:


	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2024		3,254,863		$	8.73
Granted		245,000			0.77
Forfeited		(1,126,973	)		8.34
Vested		(1,252,791	)		8.65

Unvested at September 30, 2024		1,120,099		$	7.45

The following table summarizes restricted common stock activity for the year ended December 31, 2023:


	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2023		2,239,106		$	13.75
Granted		2,279,994			6.02
Forfeited		(342,732	)		11.46
Vested		(921,505	)		13.24

Unvested at December 31, 2023		3,254,863		$	8.73

Summary of Stock Option Activity

The following table summarizes stock option activity (in thousands, except share and per share data):


	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life (in years)		Aggregate Intrinsic Value
Options outstanding at January 1, 2024		10,439,751		$	13.81		7.95	$	—
Granted		—			—		—		—
Exercised		—			—		—		—
Forfeited		(4,367,732	)		11.32		—		—

Options outstanding at September 30, 2024		6,072,019		$	15.60		6.88	$	—

Options vested and exercisable at September 30, 2024		4,579,700		$	17.51		6.56	$	—

The following table summarizes stock option activity (in thousands, except share and per share data):


	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life		Aggregate Intrinsic Value
Options outstanding at January 1, 2023		7,922,797		$	17.81		8.3	$	786
Granted		3,779,342			6.24		—		57
Exercised		—			—		—		—
Forfeited		(1,262,388	)		16.25		—		82

Options outstanding at December 31, 2023		10,439,751		$	13.81		7.9	$	—

Options vested and exercisable at December 31, 2023		4,534,147		$	18.86		7.2	$	—

Schedule of Estimated Fair Value Weighted-Average Assumptions Using Black-Scholes Option-Pricing Model

The fair value was estimated on the date of grant using the Black-Scholes option-pricing model, with the following weighted-average assumptions:


	Years Ended December 31,
	2023			2022
Expected term (in years)		6.11			6.07
Expected volatility		94	%		90	%
Risk-free interest rate		3.52	%		2.00	%
Expected dividend yield		—			—
Fair value of common stock	$	6.24		$	7.48

Commitments and Contingencies	9 Months Ended	12 Months Ended
Commitments and Contingencies	Sep. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Legal Proceedings From time to time, in the ordinary course of business, the Company is subject to litigation and regulatory examinations as well as information gathering requests, inquiries and investigations. On January 19, 2024, a purported stockholder of the Company filed a lawsuit, captioned Zerbato v. AlloVir, Inc. et al., No. 1:24-cv-10152 (D. Mass.) (the “Securities Class Action”), in the U.S. District Court for the District of Massachusetts against the Company and two of its officers purportedly on behalf of a putative class of stockholders. On April 16, 2024, the Court appointed stockholders Harry Levin and Julio Maurice Bueno as lead plaintiffs and their counsel as lead counsel in the action. On June 17, 2024, lead plaintiffs filed their amended complaint. In the amended complaint, lead plaintiffs assert claims purportedly on behalf of a putative class of stockholders consisting of persons who purchased or otherwise acquired Company securities between January 11, 2023 and December 21, 2023, inclusive. The amended complaint asserts claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, and the related regulations, alleging that the defendants made false and misleading statements and omissions to investors relating to the Company’s three Phase 3 studies of posoleucel. The complaint seeks, among other things, damages, prejudgment and post-judgment interest, and attorneys’ fees, expert fees and other costs. Defendants filed their motion to dismiss the amended complaint on August 16, 2024. The lead plaintiffs’ opposition to Defendants’ motion to dismiss is due on November 12, 2024. On July 3, 2024, a purported stockholder of the Company filed a derivative lawsuit, captioned Steffens v. Brainard et al., No. 1:24-cv-11721 (D. Mass.), in the U.S. District Court for the District of Massachusetts against certain of the Company’s officers and directors and naming the Company as a nominal defendant. The derivative complaint alleges, purportedly on behalf of the Company, violations of Section 10(b) of the Securities Exchange Act of 1934 and Rule 10b-5 thereunder, breach of fiduciary duty, aiding and abetting breach of fiduciary duty, unjust enrichment, and waste of corporate assets against the individual defendants. These claims are based on substantially identical allegations as the complaint in the above-listed Securities Class Action. The lawsuit seeks, among other things, an award of damages and restitution in favor of the Company, certain changes to the Company’s corporate governance, punitive damages, and attorneys’ fees and costs. On October 21, 2024, the court ordered plaintiff to file timely proof of service or show cause why the case should not be dismissed for failure to effect timely service by November 4, 2024. On October 21, 2024, a purported stockholder of the Company filed a derivative lawsuit, captioned Lister v. Brainard et al., No. 1:24-cv-12658 (D. Mass.), in the U.S. District Court for the District of Massachusetts against certain of the Company’s officers and directors and naming the Company as a nominal defendant. The derivative complaint alleges, purportedly on behalf of the Company, violations of Section 14(a) of the Securities Exchange Act of 1934, breach of fiduciary duties, unjust enrichment, waste of corporate assets, gross mismanagement, and abuse of control against the individual defendants and contribution under Sections 10(b) and 21D of the Securities Exchange Act of 1934 against Ms. Brainard and Mr. Sinha. These claims are based on substantially identical allegations as the complaint in the above-listed Securities Class Action. The lawsuit seeks, among other things, an award of damages and restitution in favor of the Company, certain changes to the Company’s corporate governance, and attorneys’ fees and costs. The Company intends to vigorously defend against the lawsuits. As the outcome is not presently determinable, any loss is neither probable nor reasonably estimable. Other Obligations We may incur potential contingent payments upon our achievement of clinical, regulatory and commercial milestones, as applicable, or we may be required to make royalty payments under license and grant agreements we have entered into with various entities pursuant to which we have in-licensed certain intellectual property. Due to the uncertainty of the achievement and timing of the events requiring payment under these agreements, the amounts to be paid by us are not fixed or determinable at this time (see Note 8 in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 15, 2024).	13. Commitments and Contingencies Leases The Company entered into a lease agreement and a sublease agreement for the lease of property in Waltham, Massachusetts (see Note 5 and Note 16). Legal Proceedings From time to time, in the ordinary course of business, the Company is subject to litigation and regulatory examinations as well as information gathering requests, inquiries and investigations. On January 19, 2024, a purported stockholder of the Company filed a lawsuit, captioned Zerbato v. AlloVir, Inc. et al., No. 1:24-cv-10152 (D. Mass.), in Massachusetts federal court against the Company and two of its officers purportedly on behalf of a putative class of stockholders consisting of persons who purchased or otherwise acquired Company securities between March 22, 2022 and December 21, 2023, inclusive. The complaint purports to assert claims under Section 10(b) and 20(a) of the Securities Act of 1934, as amended, and the related regulations, alleging that the defendants made false and misleading statements and omissions to investors relating to the Company’s three Phase 3 studies of posoleucel. The complaint seeks, among other things, damages, prejudgment and post-judgment interest, and attorneys’ fees, expert fees and other costs. The Company intends to vigorously defend against the lawsuit. As the outcome is not presently determinable, any loss is neither probable nor reasonably estimable. Purchase and Other Obligations We enter into contracts in the normal course of business with CROs and other third-party vendors for clinical trials and testing and manufacturing services, which can contain purchase commitments or other noncancelable obligations. Most contracts do not contain minimum purchase commitments and are cancellable by us upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including non-cancelable obligations of services provided up to one year after the date of cancellation. The amount and timing of such payments are not known. We may incur potential contingent payments upon our achievement of clinical, regulatory and commercial milestones, as applicable, or we may be required to make royalty payments under license and grant agreements we have entered into with various entities pursuant to which we have in-licensed certain intellectual property. Due to the uncertainty of the achievement and timing of the events requiring payment under these agreements, the amounts to be paid by us are not fixed or determinable at this time (see Note 8).

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,918	$ 1,934
Less: accumulated depreciation and impairment	(1,918)	(1,004)
Property and equipment, net		930
Laboratory equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,483	1,395
Computer equipment
Property Plant And Equipment [Line Items]
Total property and equipment	$ 435	435
Construction-in-Progress
Property Plant And Equipment [Line Items]
Total property and equipment		$ 104

Summary of Significant Accounting Policies - Schedule of Estimated Useful Life (Details)	Dec. 31, 2023
Computer Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Laboratory Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	5 years

Short-Term Investments

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Short-Term Investments

3. Short-Term Investments

The following tables summarize the amortized cost and estimated fair value of the Company’s U.S. government treasury securities and marketable securities, which are considered to be

available-for-sale

investments and are included in short-term investments on the consolidated balance sheets:


	September 30, 2024
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. government treasury securities	$	4,994	$	1	$	—	$	4,995

Totals	$	4,994	$	1	$	—	$	4,995


	December 31, 2023
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. government treasury securities		93,749		73		—	$	93,822

Totals	$	93,749	$	73	$	—	$	93,822

Certain short-term debt securities with original maturities of less than three months are included in cash and cash equivalents on the consolidated balance sheets and are not included in the tables above. The Company holds debt securities of companies with high credit quality and has determined that there was no material change in the credit risk of any of its debt securities. At September 30, 2024 and December 31, 2023, all investments had contractual maturities within one year.

3. Short-Term Investments

The following tables summarize the amortized cost and estimated fair value of the Company’s U.S. government treasury securities and marketable securities, which are considered to be

available-for-sale

investments and are included in short-term investments on the consolidated balance sheets:


	December 31, 2023
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government treasury securities	$	93,749	$	73	$	—		$	93,822

Totals	$	93,749	$	73	$	—		$	93,822


	December 31, 2022
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government treasury securities	$	99,288	$	1	$	(253	)	$	99,036
Marketable securities:
Corporate and agency bonds		28,748		3		(84	)		28,667

Totals	$	128,036	$	4	$	(337	)	$	127,703

Certain short-term debt securities with original maturities of less than three months are included in cash and cash equivalents on the consolidated balance sheets and are not included in the tables above. The Company holds debt securities of companies with high credit quality and has determined that there was no material change in the credit risk of any of its debt securities. At December 31, 2023 and 2022, all investments had contractual maturities within one year.

Net Loss per Share (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Earnings Per Share [Abstract]

Computation Of Basic And Diluted Net Loss Per Share Attributable To Common Stockholders

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:


	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except share and per share data)	2024			2023			2024			2023
Numerator:
Net loss – basic and diluted	$	(4,126	)	$	(44,272	)	$	(40,501	)	$	(130,722	)
Denominator:
Weighted-average common shares outstanding – basic and diluted		115,399,516			113,894,188			115,073,622			100,683,322

Net loss per share – basic and diluted	$	(0.04	)	$	(0.39	)	$	(0.35	)	$	(1.30	)

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:


	Years Ended December 31,
(in thousands, except share and per share data)	2023			2022
Numerator:
Net loss – basic and diluted	$	(190,418	)	$	(168,710	)
Denominator:
Weighted-average common shares outstanding – basic and diluted		104,057,220			76,654,856

Net loss per share – basic and diluted	$	(1.83	)	$	(2.20	)

Potential Dilutive Securities Excluded From Computation Of Diluted Net Loss Per Share Attributable To Common Stockholders

Based on the amounts outstanding at September 30, 2024 and 2023, the Company excluded the following potential shares of common stock from the computation of diluted net loss per share attributable to common stockholders for the three and nine months ended September 30, 2024 and 2023, because including them would have had an anti-dilutive effect. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same.


	September 30,
	2024		2023
Options to purchase common stock		6,072,019		10,445,312
Unvested restricted stock		1,120,099		3,410,391

Based on the amounts outstanding at December 31, 2023 and 2022, the Company excluded the following potential shares of common stock from the computation of diluted net loss per share attributable to common stockholders for the years ended December 31, 2023 and 2022, because including them would have had an anti-dilutive effect. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same.


	Years Ended December 31,
	2023		2022
Options to purchase common stock		10,439,751		7,922,797
Unvested restricted stock		3,254,863		2,239,106

Leases

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Leases [Abstract]

Leases

5. Leases

Operating leases

Development and Manufacturing Services Agreement (“DMS Agreement”) with Third-Party Supplier

In October 2022, the Company entered into a Statement of Work (“SOW”) under the DMS Agreement (“2022 SOW under the DMS Agreement”) with a third-party supplier. The 2022 SOW under the DMS Agreement contained an embedded lease for a dedicated manufacturing suite for the manufacture of AlloVir’s products at the facility because the Company directs how and for what purpose the suite is used and obtains substantially all of the economic benefit of the suite. At inception of the lease, it was determined that, in exchange for this dedicated manufacturing suite, AlloVir will pay the supplier a monthly fixed suite utilization fee, fixed batch payments and other related fixed costs, totaling $16.3 million over the 2.25 year lease term ending in December 2024. As part of the arrangement, there were also variable costs for materials,

non-fixed

batch payments, testing, storage, knowledge and tech transfer and other common area maintenance fees that were not included in the measurement of the lease liability. The lease of the facility was determined to be classified as an operating lease and commenced in October 2022, the point at which the suite was substantially complete and available for use by the Company. Accordingly, at inception, the Company recorded a

right-of-use

asset and lease liability of $14.7 million.

In December 2023, the Company issued a notice of termination of the DMS Agreement effective June 2024, or 190 days from the third-party supplier’s receipt of the notice. Management concluded that the notice of termination constituted a lease reassessment under ASC 842 as the Company was granted the option of such termination at the onset of the DMS Agreement and it was previously determined to be reasonably certain of not being exercised. As a result, the remaining lease term was shortened and the Company recorded a $4.9 million reduction to the

right-of-use

asset and lease liability in December 2023.

In February 2024, the Company entered into a new SOW (“2024 SOW under the DMS Agreement”) that terminated the 2022 SOW under the DMS Agreement with a third-party supplier, resulting in a lease remeasurement under ASC 842. The

right-of-use

asset was previously impaired and thus as a result of the liability remeasurement, the Company recorded a $5.6 million gain to reduce the lease liability in February 2024. As of June 30, 2024, the Company had paid all remaining lease obligations under the DMS Agreement.

Waltham Leases

In September 2021, the Company entered into a lease agreement with BP Bay Colony LLC and a sublease agreement with AMAG Pharmaceuticals Inc. for the lease of property in Waltham, Massachusetts (collectively, the “Waltham leases”). The space identified under the Waltham leases was intended for general office space, research and development, laboratory use, and light manufacturing. The Waltham leases are classified as operating leases and commenced in September 2021. At the inception date, the Company recorded a ROU asset and lease liability of $6.0 million for the lease and a ROU asset and lease liability of $17.3 million for the sublease based on a July 30, 2030 end date for the Waltham leases. As part of the arrangement, there were also variable costs for common area maintenance fees that were not included in the measurement of the lease liability.

In June 2024, the Company entered into a Termination of Sublease Agreement with AMAG Pharmaceuticals Inc. which terminated the sublease agreement effective June 30, 2024. In consideration of the early termination, the

Company paid a $5.7 million termination fee. The Company concluded that this early termination constituted a lease modification under ASC 842 as the Company still had access to the premises for a period of time after the execution date of the agreement. As a result of this modification, the Company included the termination fee in the remeasurement of the lease liability and ROU asset, resulting in a $1.8 million gain on lease remeasurement.

In July 2024, the Company entered into a Termination Agreement with BP Bay Colony LLC which terminates with immediate effect, the existing lease. In consideration of the termination, the Company paid a $7.0 million termination fee. As a result of this termination, the Company recorded a $1.5 million gain on lease termination.

As of September 30, 2024, the Waltham leases have terminated and the Company has paid all remaining lease obligations.

Impairment of Lease

Right-of-Use

Assets

As a result of the December 2023 announcement of the discontinuation of the Company’s three Phase 3 registrational trials, a comprehensive review of strategic alternatives, and the December 2023 notice of termination of the DMS Agreement, the Company determined that there was a triggering event for impairment. The Company determined that the operating lease

right-of-use

assets were not recoverable as the carrying value exceeded the anticipated future cash flows on an undiscounted basis. To measure the impairment, the Company determined the fair value of the operating lease

right-of-use

assets based on estimated subleasing scenarios, which represent the highest and best use of the

right-of-use

assets. This fair value assessment utilized market participant assumptions, including the anticipated amount and timing of potential sublease payments using current real estate trends and market conditions. As a result, an impairment charge was calculated by reducing the carrying amount of the operating lease

right-of-use

assets to their estimated fair value, which was determined by discounting the estimated future cash flows by applying a rate that a market participant would require in assuming the risks associated with those cash flows. In December 2023, the Company recorded an impairment loss of $16.6 million to the operating lease

right-of-use

assets. No impairment losses were recorded during the three and nine months ended September 30, 2024 and 2023, respectively.

Total lease costs were $0.0 million and $2.6 million for the three months ended September 30, 2024 and 2023, respectively, and $0.6 million and $7.7 million for the nine months ended September 30, 2024 and 2023, respectively. Cash paid for operating leases was $7.0 million and $0.8 million for the three months ended September 30, 2024 and 2023, respectively, and $17.0 million and $3.9 million for the nine months ended September 30, 2024 and 2023, respectively. The Company’s total variable lease costs, such as materials,

non-fixed

batch payments, testing, storage, knowledge and tech transfer, and other common area maintenance fees, related to the operating leases was $0.0 million and $0.2 million for the three months ended September 30, 2024 and 2023, respectively, and $0.1 million and $0.9 million for the nine months ended September 30, 2024 and 2023, respectively.

5. Leases

Operating leases

Development and Manufacturing Services Agreement (“DMS Agreement”) with Third-Party Supplier

In October 2022, the Company entered into a Statement of Work (“SOW”) under the DMS Agreement (the “2022 SOW under the DMS Agreement”) with a third-party supplier. The 2022 SOW under the DMS Agreement contained an embedded lease for a dedicated manufacturing suite for the manufacture of AlloVir’s products at the facility because the Company directs how and for what purpose the suite is used and obtains substantially all of the economic benefit of the suite. At inception of the lease, it was determined that, in exchange for this dedicated manufacturing suite, AlloVir will pay the supplier a monthly fixed suite utilization fee, fixed batch payments and other related fixed costs, totaling $16.3 million over the 2.25 year lease term ending in December 2024. As part of the arrangement, there were also variable costs for materials,

non-fixed

right-of-use

asset and lease liability of $14.7 million.

reduction to the

right-of-use

asset and lease liability in December 2023. In February 2024, the Company entered into a new SOW that terminated the 2022 SOW under the DMS Agreement (see Note 16).

Waltham Leases

In September 2021, the Company entered into a lease agreement with BP Bay Colony LLC and a sublease with AMAG Pharmaceuticals Inc. for the lease of property in Waltham, Massachusetts (collectively, the “Waltham leases”). The space identified under the Waltham leases is intended for general office space, research and development, laboratory use, and light manufacturing. The Waltham leases are classified as operating leases and commenced in September 2021. At the inception date, the Company recorded a ROU asset and lease liability of $6.0 million for the lease and a ROU asset and lease liability of $17.3 million for the sublease based on a July 30, 2030 end date for the Waltham leases. As part of the arrangement, there were also variable costs for common area maintenance fees that were not included in the measurement of the lease liability. The agreement also provided a $3.1 million tenant improvement allowance. The Company utilized $0.9 million of the tenant improvement allowance. The Company has the option to renew the leased space for an additional one time period of five years with written notice from the Company. As of December 31, 2023, the Company has no reasonable certainty that this option to extend will be exercised.

Impairment of Lease

Right-of-Use

Assets

right-of-use

assets based on estimated subleasing scenarios, which represent the highest and best use of the

right-of-use

assets to their estimated fair value, which was determined by discounting the estimated future cash flows by applying a rate that a market participant would require in assuming the risks associated with those cash flows. During the year ended December 31, 2023, the Company recorded an impairment loss of $16.6 million to the operating lease

right-of-use

assets. As of December 31, 2023, the remaining

right-of-use

asset balance is $2.2 million, which relates to the Waltham leases.

Maturities of operating lease liabilities at December 31, 2023 are as follows (in thousands):


2024		11,842
2025		3,219
2026		3,298
2027		3,376
2028		3,455
Thereafter		5,824

Total lease payments		31,014
Less: interest		3,585

Total lease liability	$	27,429

Lease liability – current	$	10,781
Lease liability – long-term	$	16,648

Total lease costs were $9.7 million and $6.6 million for the years ended December 31, 2023 and 2022, respectively. Cash paid for operating leases was $4.8 million and $4.8 million for the year ended December 31, 2023 and 2022, respectively. The Company’s total variable lease costs, such as materials,

non-fixed

batch payments, testing, storage, knowledge and tech transfer, and other common area maintenance fees, related to the operating leases was $0.9 million and $3.7 million for the years ended December 31, 2023 and 2022, respectively. The weighted average remaining lease term is 4.70 years and 6.93 years at December 31, 2023 and 2022, respectively. The weighted average discount rate is 5.95% and 6.23% at December 31, 2023 and 2022, respectively.

Restructuring Costs (Tables)

9 Months Ended

Sep. 30, 2024

Restructuring and Related Activities [Abstract]

Details of Restructuring Liability Included in Accrued Expenses

The following table presents the details of the Company’s restructuring liability, which is included in accrued expenses on the consolidated balance sheet at September 30, 2024 as follows:


(in thousands)	Restructuring Liability
Balance at December 31, 2023	$	—
Restructuring charges		10,059
Cash payments		9,939

Balance at September 30, 2024	$	120

Stock-Based Compensation - Schedule of Estimated Fair Value Weighted-Average Assumptions Using Black-Scholes Option-Pricing Model (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Expected term (in years)	6 years 1 month 9 days	6 years 25 days
Expected volatility	94.00%	90.00%
Risk-free interest rate	3.52%	2.00%
Expected dividend yield	0.00%	0.00%
Fair value of common stock	$ 6.24	$ 7.48

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) SEGMENT	Dec. 31, 2022 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segment \| SEGMENT	1
Cash and cash equivalents maturity period	3 months
Short-term investments maturity period	1 year
Property, plant and equipment, valuation basis	cost
Property, plant and equipment, depreciation methods	Useful Life, Lease Term [Member]
Deferred offering costs	$ 0	$ 0
Amortization expense for cloud computing arrangements	$ 500,000	$ 500,000
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges
Expected dividend yield	0.00%	0.00%
Off-balance sheet risk description	At December 31, 2023 and 2022, the Company had no off-balance sheet risk.
ASU 2016-13
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2023
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
Internal-use Software
Summary Of Significant Accounting Policies [Line Items]
Expected useful life	3 years
Impairment loss implementation costs	$ 1,400,000

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Number of Options Outstanding, Beginning Balance	10,439,751	7,922,797
Number of options, granted		3,779,342
Number of Options, Forfeited	(4,367,732)	(1,262,388)
Number of Options Outstanding, Ending Balance	6,072,019	10,439,751	7,922,797
Options vested and exercisable at September 30, 2024	4,579,700	4,534,147
Weighted Average Exercise Price, Options outstanding as of January 1, 2024	$ 13.81	$ 17.81
Weighted Average Exercise Price, Granted		6.24
Weighted Average Exercise Price, Forfeited	11.32	16.25
Weighted Average Exercise Price, Options outstanding at September 30, 2024	15.6	13.81	$ 17.81
Weighted Average Exercise Price, Options vested and exercisable at September 30, 2024	$ 17.51	$ 18.86
Weighted Average Contractual Life (in years), Options outstanding	6 years 10 months 17 days	7 years 11 months 12 days	8 years 3 months 18 days
Weighted Average Contractual Life (in years), Options vested and exercisable at September 30, 2024	6 years 6 months 21 days	7 years 2 months 12 days
Aggregate Intrinsic Value, Options outstanding at January 1, 2023		$ 786
Aggregate Intrinsic Value, Granted		57
Aggregate Intrinsic Value, Forfeited		$ 82

Fair Value Measurements

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis:


	September 30, 2024
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	113,794	$	—	$	—	$	113,794

Totals	$	113,794	$	—	$	—	$	113,794

Short-term investments:
U.S. government treasury securities	$	4,995	$	—	$	—	$	4,995

Totals	$	4,995	$	—	$	—	$	4,995


	December 31, 2023
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	23,854	$	—	$	—	$	23,854

Totals	$	23,854	$	—	$	—	$	23,854

Short-term investments:
U.S. government treasury securities		93,822		—		—	$	93,822

Totals	$	93,822	$	—	$	—	$	93,822

During the nine months ended September 30, 2024 and the year ended December 31, 2023, there were no transfers between levels. The Company classifies its money market fund and U.S. government treasury securities as Level 1 assets under the fair value hierarchy, as these assets have been valued using quoted market prices in active markets without any valuation adjustment.

The carrying amounts of prepaid expenses and other current assets, prepaid expenses to related party, accounts payable, amount due to related party and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities.

4. Fair Value Measurements

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis:


	December 31, 2023
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	23,854	$	—	$	—	$	23,854

Totals	$	23,854	$	—	$	—	$	23,854

Short-term investments:
U.S. government treasury securities	$	93,822	$	—	$	—	$	93,822

Totals	$	93,822	$	—	$	—	$	93,822


	December 31, 2022
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market fund	$	32,641	$	—	$	—	$	32,641

Totals	$	32,641	$	—	$	—	$	32,641

Short-term investments:
U.S. government treasury securities	$	99,036	$	—	$	—	$	99,036
Marketable securities:
Corporate and agency bonds		—		28,667		—		28,667

Totals	$	99,036	$	28,667	$	—	$	127,703

During the years ended December 31, 2023 and 2022, there were no transfers between levels. The Company classifies its money market fund and U.S. government treasury securities as Level 1 assets under the fair value hierarchy, as these assets have been valued using quoted market prices in active markets without any valuation adjustment. The Company classifies its marketable securities as Level 2 assets under the fair value hierarchy, as these assets have pricing inputs that are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined using models or other valuation methodologies.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
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-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

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+ Details

Restructuring Costs

9 Months Ended

Sep. 30, 2024

Restructuring and Related Activities [Abstract]

Restructuring Costs

13. Restructuring Costs

In January 2024, the Company’s board of directors approved a RIF of approximately 95% of the Company’s employee base in order to reduce costs and preserve capital in light of the announcement on December 22, 2023 that the Company is discontinuing its three global Phase 3 posoleucel studies. The Company communicated the RIF to affected employees in January 2024.

The RIF was primarily completed during the first quarter of 2024 and was substantially completed by April 15, 2024. As a result of these actions, the Company recorded restructuring costs of $0.1 million and

$10.1 million for the three and nine months ended September 30, 2024, respectively, consisting primarily of employee severance, continuing healthcare benefits and other employee-related costs. Restructuring costs associated with

one-time

termination benefits were recorded pursuant to ASC 420. Cash payments related to the restructuring costs are substantially complete as of September 30, 2024 with remaining cash payments anticipated to be completed by the first half of 2025.

The following table presents the details of the Company’s restructuring liability, which is included in accrued expenses on the consolidated balance sheet at September 30, 2024 as follows:


(in thousands)	Restructuring Liability
Balance at December 31, 2023	$	—
Restructuring charges		10,059
Cash payments		9,939

Balance at September 30, 2024	$	120

Stockholders Equity - Schedule of Reserved Shares of Common Stock for Issuance (Details) - shares	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022	Jul. 31, 2020
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	23,868,676	18,357,134	14,869,885
2020 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	1,585,257	480,059		611,354
Option To Purchase Common Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	6,072,019	10,439,751	7,922,797
Unvested Restricted Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	1,120,099	3,254,863	2,239,106
Stock Available For Grant \| 2020 Stock Option and Grant Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	15,091,301	4,182,461	4,253,680
Stock Available For Issuance \| 2020 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	1,585,257	480,059	454,302

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2003/role/exampleRef
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+ Details

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Operating expenses:
Research and development	$ (246)	$ 34,156	$ 12,020	$ 99,698	$ 133,070	$ 118,870
General and administrative	5,883	12,805	23,712	37,797	48,261	52,332
Impairment costs					18,570
Restructuring costs	83		10,059
Total operating expenses	5,720	46,961	45,791	137,495	199,901	171,202
Loss from operations	(5,720)	(46,961)	(45,791)	(137,495)	(199,901)	(171,202)
Total other income (loss), net:
Interest income	1,494	1,522	4,100	4,362	5,734	1,876
Other income (loss), net	100	1,167	1,190	2,411	3,623	351
Loss before income taxes					(190,544)	(168,975)
Income tax benefit	0	0			(126)	(265)
Net loss	$ (4,126)	$ (44,272)	$ (40,501)	$ (130,722)	$ (190,418)	$ (168,710)
Net loss per share — basic	$ (0.04)	$ (0.39)	$ (0.35)	$ (1.3)	$ (1.83)	$ (2.2)
Net loss per share — diluted	$ (0.04)	$ (0.39)	$ (0.35)	$ (1.3)	$ (1.83)	$ (2.2)
Weighted-average common shares outstanding — basic	115,399,516	113,894,188	115,073,622	100,683,322	104,057,220	76,654,856
Weighted-average common shares outstanding — diluted	115,399,516	113,894,188	115,073,622	100,683,322	104,057,220	76,654,856
Comprehensive loss:
Net loss	$ (4,126)	$ (44,272)	$ (40,501)	$ (130,722)	$ (190,418)	$ (168,710)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on available-for-sale securities	5	25	(72)	268	406	(313)
Total other comprehensive income (loss)	5	25	(72)	268	406	(313)
Comprehensive loss	$ (4,121)	$ (44,247)	$ (40,573)	$ (130,454)	$ (190,012)	$ (169,023)

Summary of Significant Accounting Policies

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2023, and notes thereto, which are included in the Company’s Annual Report on Form

10-K

that was filed with the Securities and Exchange Commission (the “SEC”) on March 15, 2024. Since the date of those financial statements, there have been no material changes to the Company’s significant accounting policies except as described below.

Restructuring Costs

The Company records costs and liabilities associated with exit and disposal activities in accordance with ASC 420,

Exit or Disposal Cost

Obligations

(ASC 420). Such costs are based on estimates of fair value in the period liabilities are incurred. Given the short duration of when the liability is

incurred to when it is paid, there is no significant difference between fair value and the amount paid. Costs are expensed at the date the entity notifies the employee, unless the employee must provide future service, in which case the benefits are expensed ratably over the future service period. The Company evaluates and adjusts these costs as appropriate for changes in circumstances as additional information becomes available. Refer to Note 13 for further information regarding restructuring costs.

Interim Financial Information

The accompanying condensed consolidated balance sheet at September 30, 2024, and the condensed consolidated statements of operations and comprehensive loss, statements of changes in stockholders’ equity for the three and nine months ended September 30, 2024 and 2023 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2024 and 2023 are unaudited. The condensed consolidated interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the fair presentation of the Company’s financial position at September 30, 2024 and the results of its operations for the three and nine months ended September 30, 2024 and 2023 and its cash flows for the nine months ended September 30, 2024 and 2023. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2024 and 2023 are also unaudited. The results for the three and nine months ended September 30, 2024 are not necessarily indicative of results to be expected for the year ending December 31, 2024 or for any other subsequent interim period.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with certain new or revised accounting standards pursuant to Section 107(b) of the JOBS Act.

Since December 31, 2023, there have been no new accounting pronouncements adopted by the Company or issued by FASB that are applicable to the Company, except as noted below.

Recently Issued Accounting Pronouncements Not Yet Adopted

In November 2023, the FASB issued ASU

2023-07,

Segment Reporting

(Topic 280):

Improvements to Reportable Segment Disclosures

, which requires disclosure of incremental segment information on an interim and annual basis. This ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal periods beginning after December 15, 2024, and requires retrospective application to all prior periods presented in the financial statements. The Company expects to enhance annual segment reporting disclosures based on the new requirements.

In December 2023, the FASB issued ASU

2023-09,

Income Taxes (Topic 740):

Improvements to Income Tax Disclosures

, which requires public companies, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. This ASU is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the Company’s condensed consolidated financial statements and related disclosures.

2. Summary of Significant Accounting Policies

Basis of Presentation and Consolidation

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). The consolidated financial statements include the Company’s accounts and those of its wholly-owned subsidiaries. All intercompany accounts, transactions and balances have been eliminated in consolidation.

Segment Information

Operating segments are defined as components of an enterprise for which separate and discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company has one operating segment. The Company’s singular focus is the research, development and commercialization of

off-the-shelf

VST therapies to prevent and treat severe viral-associated diseases. The Company’s chief operating decision maker, its Chief Executive Officer, manages the Company’s operations on a consolidated basis for the purpose of allocating resources. All of the Company’s long-lived assets are held in the United States.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Changes in estimates and assumptions are reflected in reported results in the period in which they become known. Actual results could differ from those estimates.

Cash and Cash Equivalents

Cash and cash equivalents are short-term, highly liquid investments with original maturities of three months or less at the date of purchase. Investments qualifying as cash equivalents primarily consist of money market funds, corporate bonds and commercial paper.

Short-Term Investments

Short-term investments consist of U.S. treasury securities and corporate bonds classified as

available-for-sale

that have maturities of less than one year.

Available-for-sale

securities are carried at fair value, with the unrealized gains and losses reported in other comprehensive income (loss) until realized. The amortized cost of debt securities

in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization or accretion is included in “other income (loss), net”. Realized gains and losses are determined using the specific identification method and are included in “other income (loss), net”.

Restricted Cash

Cash accounts with any type of restriction are classified as restricted cash. The Company has restricted cash deposits with a bank, which serve as collateral for a letter of credit issued to the landlord of the Company’s leased Waltham facility for a security deposit. The Company classified this amount as

non-current

restricted cash in the accompanying consolidated balance sheet at December 31, 2023 and 2022.

Property and Equipment, Net

The Company records property and equipment at cost and

recognizes depreciation using the straight-line method over the estimated useful lives of the respective assets

, as follows:


Asset category		Estimated useful life
Computer equipment		3 years
Laboratory equipment		5 years

The Company periodically evaluates whether events and circumstances have occurred that may warrant revision of the estimated useful life of property and equipment. Expenditures for repairs and maintenance of assets are expensed as incurred. Upon retirement or sale, the cost of assets disposed and the corresponding accumulated depreciation are removed from the related accounts and any resulting gain or loss is reflected in the results of operations. Construction in progress is not depreciated until it is placed in service. Property and equipment to be disposed of are carried at fair value less costs to sell.

Impairment of Long-Lived Assets

The Company accounts for long-lived assets in accordance with ASC Topic 360,

Property, Plant, and Equipment

(“ASC 360”). ASC 360 requires companies to: (i) recognize an impairment loss only if the carrying amount of a long-lived asset is not recoverable based on its undiscounted future cash flows and (ii) measure an impairment loss as the difference between the carrying amount and the fair value of the asset.

The Company tests long-lived assets to be held and used, including

right-of-use

assets and property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of assets or asset groups may not be fully recoverable. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their fair values. See Note 5 and Note 6 for impairment costs recognized during the years ended December 31, 2023 and 2022.

Fair Value Measurements

ASC Topic 820,

Fair Value Measurement

(“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances.

ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes among the following:

•

Level 1 – Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access.

•

Level 2 – Valuations based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active and models for which all significant inputs are observable, either directly or indirectly.

•

Level 3 – Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

The Company’s financial instruments include cash equivalents, short-term investments, prepaid expenses and other current assets, prepaid expenses to related party, accounts payable, amount due to related party and accrued expenses. Certain of the Company’s financial assets, including cash equivalents and short-term investments, have been initially valued at the transaction price, and subsequently revalued at the end of each reporting period, utilizing third-party pricing services or other observable market data. The pricing services utilize industry standard valuation models and observable market inputs to determine value.

Other financial instruments, including prepaid expenses and other current assets, prepaid expenses to related party, accounts payable, amount due to related party and accrued expenses, are carried at cost, which approximate fair value due to the short duration and term to maturity.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with

in-process

equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the respective equity instrument issued. Should an

in-process

equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. At December 31, 2023 and 2022, the Company had no deferred offering costs.

Cloud Computing Arrangements

The Company capitalizes certain implementation costs for

internal-use

software incurred in a cloud computing agreement that is a service contract. Eligible costs associated with cloud computing arrangements, such as the implementation costs incurred to develop or obtain software business applications used in the normal course of business, are capitalized in accordance with ASC 350. Capitalization ceases at the point the software is substantially complete and ready for its intended use, and after all substantial testing is completed. Amortization is recorded on a straight-line basis over the expected useful life of three years of the

internal-use

software cost in

the same line item in the statement of operations and comprehensive loss as the expense for fees for the associated cloud computing arrangement. Amortization expense associated with the Company’s cloud computing arrangements has been recognized in the amount of $0.5 million during the years ended December 31, 2023 and 2022. As a result of the December 2023 announcement of the discontinuation of the Company’s three Phase 3 registrational trials and a comprehensive review of strategic alternatives, an

impairment loss

of $1.4 million was recognized during the year ended December 31, 2023 for implementation costs associated with cloud computing arrangements that are no longer probable of being implemented.

Other Income (Loss), Net

The Company records interest expense, investment amortization and accretion of discounts and premiums on short-term investments and foreign exchange gains and losses in “other income (loss), net” when incurred.

Research and Development Costs

Research and development costs are charged to expense as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including personnel-related costs, stock-based compensation, facilities, research-related overhead, clinical trial costs, contracted services, research-related manufacturing, license fees and other external costs. The Company accounts for nonrefundable advance payments for goods and services that will be used in future research and development activities as expenses when the services have been performed or when the goods have been received.

Accrued Research and Development Expenses

The Company has entered into various research and development contracts. The payments under these contracts are recorded as research and development expenses as incurred. The Company records accrued liabilities for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Judgements and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Stock-Based Compensation Expense

The Company grants restricted stock and stock options to employees, consultants and directors. The Company recognizes stock-based compensation cost for awards with performance conditions if and when it concludes that it is probable that the performance conditions will be achieved. For awards with only a service condition, the Company expenses stock-based compensation on a straight-line basis over the requisite employee service period or for grants issued with performance conditions, on a graded-vesting basis over the requisite employee service period. Awards for employees and

non-employees

are accounted for similarly. The Company records stock-based compensation expense associated with grants of restricted stock and stock options in the consolidated statements of operations and comprehensive loss based on their estimated fair value at the date of the grant. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the grantee’s payroll costs are classified or in which the grantee’s service payments are classified. Forfeitures are accounted for as they occur.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The fair value of the Company’s common stock is determined based on the quoted market price of common stock. The Company also lacks company-specific historical and implied volatility information for its

stock. The Company estimates its expected stock price volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method. The “simplified” method estimates the expected term of stock options as the mid-point between the weighted average time to vesting and the contractual maturity. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. There is no expected dividend yield since the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future.

Net Loss per Share

Basic and diluted net loss per share is determined by dividing net loss by the weighted-average common stock outstanding during the period. Since we have incurred operating losses for all periods presented, outstanding stock options and unvested restricted common stock have been excluded from the calculation because their effects would be anti-dilutive. Therefore, the weighted-average shares used to calculate both basic and diluted loss per share are the same.

Income Taxes

The Company accounts for income taxes under the asset and liability method in accordance with ASC 740,

Income Taxes

. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted rates in effect for the year in which these temporary differences are expected to be recovered or settled. Valuation allowances are provided if based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. Management believes that it is more likely than not that all deferred tax assets will not be realized.

The Company recognizes liabilities for potential tax payments to various tax authorities related to uncertain tax positions. The liabilities are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filing is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit. Potential interest and penalties associated with such uncertain tax positions, if any, are recorded as components of income tax expense.

The Company assesses its income tax positions and records tax benefits for all years subject to examination based upon management’s evaluation of the facts, circumstances and information available as of the reporting date. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50 percent likelihood of being realized upon ultimate settlement with a taxing authority having full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, the Company does not recognize a tax benefit in the consolidated financial statements.

Concentration of Credit Risk and

Off-Balance

Sheet Risk

Financial instruments that subject the Company to credit risk consist primarily of cash, cash equivalents, restricted cash and short-term investments. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company deposits its cash in financial institutions that it believes have high credit quality and have not experienced any losses on such accounts and does not believe it is

exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships. Such deposits have and will continue to exceed federally insured limits. The Company has not experienced any losses on its cash deposits.

At December 31, 2023 and 2022, the Company had no

off-balance

sheet risk.

Foreign Exchange

The functional currency for all subsidiaries is the U.S. Dollar (“USD”). Transactions in foreign currencies are remeasured into the functional currency of the relevant subsidiaries at the exchange rate in effect at the date of the transaction. Any monetary assets and liabilities arising from these transactions are translated into the functional currency at exchange rates in effect at the balance sheet date or on settlement. Resulting gains and losses are recorded in “other income (loss), net” within the consolidated statements of operations and comprehensive loss.

Comprehensive Loss

Comprehensive loss is defined as a change in equity of a business enterprise during a period, resulting from transactions from

non-owner

sources. Comprehensive loss includes net loss and certain changes in stockholder’s deficit that are excluded from net loss. The Company’s comprehensive loss includes unrealized gains (losses) on

available-for-sale

securities during the year ended December 31, 2023 and 2022.

Leases

In accordance with ASC Topic 842,

Lease Accounting

, at the inception of an arrangement, the Company determines whether the arrangement is or contains a lease. Leases with a term greater than one year are recognized on the consolidated balance sheet as a

right-of-use

(“ROU”) asset and current and

non-current

lease liabilities, as applicable. The Company has made an accounting policy election, known as the short-term lease recognition exemption, which allows the Company to not recognize ROU assets and lease liabilities that arise from short-term leases (12 months or less) for any class of underlying asset. Options to renew or options to cancel a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew or will not cancel, respectively.

Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected remaining lease term. Lease cost for operating leases is recognized on a straight-line basis over the lease term as an operating expense. Certain adjustments to the ROU asset may be required for items such as lease prepayments or incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment.

The Company has elected to account for the lease and

non-lease

components together for all existing classes of underlying assets.

Subsequent Events

The Company evaluates events occurring after the date of our accompanying consolidated balance sheets for potential recognition or disclosure in our consolidated financial statements. The Company did not identify any material subsequent events requiring adjustment to our accompanying consolidated financial statements

(recognized subsequent events). Those items requiring disclosure (unrecognized subsequent events) in the consolidated financial statements have been disclosed accordingly. Refer to Note 16 for further details.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with certain new or revised accounting standards pursuant to Section 107(b) of the JOBS Act.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU

No. 2016-13,

Financial Instruments—Credit Losses

(Topic 326):

Measurement of Credit Losses on Financial

Instruments

, or ASU

2016-13,

which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU

2016-13

replaces the existing incurred loss impairment model with an expected loss model. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to

available-for-sale

debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. These changes may result in earlier recognition of credit losses. The Company adopted ASU

2016-13

on January 1, 2023. The adoption of ASU

2016-13

did not have a material impact on the Company’s consolidated financial statements and related disclosures.

Recently Issued Accounting Pronouncements Not Yet Adopted

In November 2023, the FASB issued ASU

2023-07,

Segment Reporting

(Topic 280):

Improvements to Reportable Segment Disclosures

, which requires disclosure of incremental segment information on an interim and annual basis. This ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal periods beginning after December 15, 2024, and requires retrospective application to all prior periods presented in the financial statements. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU

2023-09,

Income Taxes (Topic 740):

Improvements to Income Tax Disclosures

, which requires public entities, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. This ASU is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

Cover Page	9 Months Ended
Cover Page	Sep. 30, 2024
Document Information [Line Items]
Document Type	S-4
Amendment Flag	false
Entity Registrant Name	ALLOVIR, INC.
Entity Central Index Key	0001754068
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	83-1971007
Entity Address Address Line1	PO Box 44, 1661 Massachusetts Avenue
Entity Address City Or Town	Lexington
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02420
City Area Code	617
Local Phone Number	443-2400
Entity Primary SIC Number	2834
Business Contact
Document Information [Line Items]
Entity Address Address Line1	PO Box 44, 1661 Massachusetts Avenue
Entity Address City Or Town	Lexington
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02420
City Area Code	617
Local Phone Number	443-2605
Contact Personnel Name	Diana Brainard, M.D.

Stock-Based Compensation

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

Stock-Based Compensation Expense

Stock-based compensation expense was as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Research and development	$	312	$	3,254	$	232	$	10,191
General and administrative		4,635		7,214		15,657		20,594

Total stock-based compensation expense	$	4,947	$	10,468	$	15,889	$	30,785

Stock Modification

In connection with the reduction in the Company’s workforce (“RIF”) (see Note 13), the Company accelerated certain unvested stock options and restricted common stock scheduled to vest in the three month period following the employees’ separation date. The Company determined that the acceleration of the unvested units constituted a Type III modification in accordance with ASC 718, resulting in a new measurement of compensation cost. As of September 30, 2024, 664,248 units were accelerated. For the nine months ended

September 30, 2024, the acceleration resulted in the recognition of $0.1 million of stock-based compensation expense using the reassessed fair value on the modification date and a reversal of $4.0 million in stock-based compensation expense for previously recognized expense using the original grant date fair value, of which $2.4 million was related to research and development expense and $1.6 million was related to general and administrative expense. There were no units accelerated during the three months ended September 30, 2024.

2020 Stock Option and Grant Plan

At September 30, 2024, there is an aggregate of 15,091,301 shares reserved for future issuance under the 2020 Plan.

Restricted Common Stock

The following table summarizes restricted common stock activity for the nine months ended September 30, 2024:


	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2024		3,254,863		$	8.73
Granted		245,000			0.77
Forfeited		(1,126,973	)		8.34
Vested		(1,252,791	)		8.65

Unvested at September 30, 2024		1,120,099		$	7.45

At September 30, 2024, there was $7.0 million of unrecognized stock-based compensation expense related to restricted stock, which is expected to be recognized over a weighted average period of 1.60 years. The total fair value of restricted stock vested was $0.9 million and $3.0 million for the nine months ended September 30, 2024 and 2023, respectively.

Stock Options

The following table summarizes stock option activity (in thousands, except share and per share data):


	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life (in years)		Aggregate Intrinsic Value
Options outstanding at January 1, 2024		10,439,751		$	13.81		7.95	$	—
Granted		—			—		—		—
Exercised		—			—		—		—
Forfeited		(4,367,732	)		11.32		—		—

Options outstanding at September 30, 2024		6,072,019		$	15.60		6.88	$	—

Options vested and exercisable at September 30, 2024		4,579,700		$	17.51		6.56	$	—

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the common stock as of the end of the period.

There were no options granted during the nine months ended September 30, 2024. The weighted-average grant date fair value of stock options granted during the nine months ended September 30, 2023 was $4.92 per share. At September 30, 2024, there was $8.9 million of unrecognized stock-based compensation expense related to unvested stock options, which is being recognized over a period of 1.52 years.

2020 Employee Stock Purchase Plan

The Company issued 36,337 common shares under the Employee Stock Purchase Plan (the “ESPP”) during the nine months ended September 30, 2024 at an average price per share of $0.58. Cash received from purchases under the ESPP for the nine months ended September 30, 2024 and 2023 were $0.0 million and $0.3 million, respectively. The Company recognized $0.0 and $0.3 million of compensation expense for the ESPP during the nine months ended September 30, 2024 and 2023, respectively.

At September 30, 2024, there was an aggregate of 1,585,257 shares reserved for future issuance under the ESPP.

10. Stock-Based Compensation

Stock-Based Compensation Expense

Stock-based compensation expense was as follows:


	Years Ended December 31,
(in thousands)	2023		2022
Research and development	$	13,167	$	14,014
General and administrative		27,612		27,301

Total stock-based compensation expense	$	40,779	$	41,315

2018 Equity Incentive Plan

The Company’s 2018 Plan provided for the Company to issue restricted stock, restricted stock units, incentive stock options, and

non-statutory

stock options and other stock-based awards to employees, officers, members of the Board, consultants and advisors of the Company. The 2018 Plan was most recently amended in July 2020. The awards granted under this plan generally vest over a four-year period and have a

10-year

contractual term.

At December 31, 2023, there was an aggregate of 64,042 shares of common stock issuable upon the exercise of outstanding options under the 2018 Plan and 6,616,772 shares of restricted common stock granted under the 2018 plan. No shares remain available for future issuance under the 2018 Plan. Any options or awards outstanding under the 2018 Plan remain outstanding and effective.

2020 Stock Option and Grant Plan

On July 2, 2020, the Company’s Board of Directors adopted and in July 2020 the stockholders approved the 2020 Stock Option and Grant Plan (the “2020 Plan”) which became effective on July 28, 2020, the date immediately prior to the date on which the registration statement related to the IPO was declared effective, and as a result no further awards were made under the 2018 Plan thereafter. Initially, the aggregate number of shares of our common stock that may be issued pursuant to stock awards under the 2020 Plan was 8,008,734 shares. The number of shares of our common stock reserved for issuance under the 2020 Plan shall be cumulatively increased on January 1, 2021 and each January 1 thereafter by 5% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year or a lesser number of shares determined by our board of directors. Unless our board of directors elects not to increase the number of shares available for future grant each year, our stockholders may experience additional dilution, which could cause our stock price to fall. On January 1, 2023, 4,663,403 shares were added to the number of available shares under the 2020 Plan. The awards granted under this plan generally vest over a four-year period and have a

10-year

contractual term.

At December 31, 2023, there were an aggregate of 10,375,709 shares of common stock issuable upon the exercise of outstanding options under the 2020 Plan and 5,356,510 shares of restricted common stock granted under the 2020 Plan. There is an aggregate of 4,182,461 shares reserved for future issuance under the 2020 Plan.

Restricted Common Stock

The following table summarizes restricted common stock activity for the year ended December 31, 2023:


	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2023		2,239,106		$	13.75
Granted		2,279,994			6.02
Forfeited		(342,732	)		11.46
Vested		(921,505	)		13.24

Unvested at December 31, 2023		3,254,863		$	8.73

At December 31, 2023, there was $23.6 million of unrecognized stock-based compensation cost related to the restricted stock, which is expected to be recognized over a weighted average period of 2.20 years. The total fair value of restricted stock vested was $3.6 million and $14.2 million for the year ended December 31, 2023 and 2022, respectively.

Stock Options

The following table summarizes stock option activity (in thousands, except share and per share data):


	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life		Aggregate Intrinsic Value
Options outstanding at January 1, 2023		7,922,797		$	17.81		8.3	$	786
Granted		3,779,342			6.24		—		57
Exercised		—			—		—		—
Forfeited		(1,262,388	)		16.25		—		82

Options outstanding at December 31, 2023		10,439,751		$	13.81		7.9	$	—

Options vested and exercisable at December 31, 2023		4,534,147		$	18.86		7.2	$	—

The weighted average grant-date fair value of stock options granted during the year ended December 31, 2023 and 2022 was $4.88 per share and $5.61 per share, respectively. At December 31, 2023, there was $36.9 million of unrecognized stock-based compensation expense related to unvested stock options, which is being recognized over a period of 1.92 years.

The fair value was estimated on the date of grant using the Black-Scholes option-pricing model, with the following weighted-average assumptions:


	Years Ended December 31,
	2023			2022
Expected term (in years)		6.11			6.07
Expected volatility		94	%		90	%
Risk-free interest rate		3.52	%		2.00	%
Expected dividend yield		—			—
Fair value of common stock	$	6.24		$	7.48

2020 Employee Stock Purchase Plan

In July 2020, the 2020 Employee Stock Purchase Plan (the “2020 ESPP”) was adopted by the Board of Directors and approved by the stockholders. The purpose of the 2020 ESPP is to provide eligible employees of the Company and other designated companies, with opportunities to purchase shares of the Company’s common stock, par value $0.0001 per share.

Initially, 611,354 shares of common stock in the aggregate were approved and reserved for this purpose. The number of shares of common stock reserved and available for issuance under the 2020 ESPP shall be cumulatively increased on January 1, 2021 and each January 1 thereafter by the least of (i) 1,222,707 shares of common stock, (ii) 1% of the number of shares of common stock issued and outstanding on the immediately preceding December 31, and (iii) such number of shares of common stock as determined by the Administrator. On January 1, 2023, 160,000 shares were added to the number of available shares under the ESPP. At December 31, 2023, there was an aggregate of 480,059 shares reserved for future issuance under the ESPP.

The ESPP allows eligible employees to authorize payroll deductions of up to 15% of their base salary or wages up to $25,000 annually to be applied toward the purchase of shares of the Company’s common stock on the last trading day of the offering period. Participating employees will purchase shares of the Company’s common stock at a discount of up to 15% on the lesser of the closing price of the Company’s common stock on the NASDAQ Global Market (i) on the first trading day of the offering period or (ii) the last day of any offering period. The Company utilizes the Black Scholes option pricing model to compute the fair market value of the shares and compensation expense is recognized over the offering period.

Six-month

offering periods commence each January 1 and July 1 during the term of the plan, with the administrator having the right to establish different offering periods.

Participation in the ESPP is voluntary. Eligible employees become participants in the ESPP by enrolling in the plan and authorizing payroll deductions. At the end of each offering period, accumulated payroll deductions are used to purchase the Company’s shares at the discounted price. The Company makes no contributions to the ESPP. A participant may withdraw from the ESPP or suspend contributions to the ESPP. If the participant elects to withdraw during an offering period, all contributions are refunded as soon as administratively practicable. If a participant elects to withdraw or suspend contributions, they will not be able to

re-enroll

in the current offering but may elect to participate in future offerings. The ESPP purchases only whole shares of the Company’s common stock.

The Company issued 134,243 common shares under the ESPP during the year ended December 31, 2023, at an average price per share of $2.43. Cash received from purchases under the ESPP for the year ended December 31, 2023 and 2022 was $0.3 million and $0.5 million, respectively. The Company recognized $0.3 million and $0.2 million of compensation expense for the ESPP during the year ended December 31, 2023 and 2022, respectively.

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)
Issuance costs	$ 0.2

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Benefit Plans	15. Employee Benefit Plans Effective January 1, 2019, the Company adopted a 401(k) Plan for its employees, which is designed to be qualified under Section 401(k) of the Internal Revenue Code. Eligible employees are permitted to contribute to the 401(k) Plan within statutory and 401(k) Plan limits. The Company made matching contributions of $0.9 million and $0.8 million for the years ended December 31, 2023 and 2022, respectively.

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following:


	December 31,
(in thousands)	2023			2022
Laboratory equipment	$	1,483		$	1,395
Computer equipment		435			435
Construction-in-progress		—			104

Total property and equipment		1,918			1,934
Less: accumulated depreciation and impairment		(1,918	)		(1,004	)

Property and equipment, net	$	—		$	930

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (40,501)	$ (130,722)	$ (190,418)	$ (168,710)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		257	398	723
Non-cash lease expense	145	3,790	7,893	1,842
Non-cash gain on lease termination and remeasurement	(8,872)
Impairment costs			18,570
Accretion of short-term investment discounts	(1,245)	(2,486)	(3,698)	(1,076)
Stock-based compensation expense	15,889	30,785	40,779	41,315
Changes in operating assets and liabilities:
Interest receivable	153	(77)	(49)	(107)
Prepaid expenses and other current assets and prepaid expenses to related party	2,858	2,633	5,614	(3,028)
Other assets	122	(813)	(900)	490
Income tax payable		(128)	(128)	(879)
Accounts payable, accrued expenses, other liabilities and amount due to related party	(32,687)	3,045	(2,512)	(12,622)
Net cash used in operating activities	(64,138)	(93,716)	(124,451)	(142,052)
Cash flows from investing activities
Purchase of short-term investments		(116,046)	(125,827)	(228,806)
Maturities of short-term investments	90,000	128,813	163,812	148,328
Net cash provided by (used in) investing activities	90,000	12,767	37,985	(80,478)
Cash flows from financing activities
Proceeds from issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs		70,169	70,169
Proceeds from issuance of common stock in registered direct offering, net of issuance costs				126,425
Proceeds from issuance of stock under the 2020 Employee Stock Purchase Plan	21	315	326	536
Net cash provided by financing activities	21	70,484	70,495	126,961
Net increase (decrease) in cash, cash equivalents, and restricted cash	25,883	(10,465)	(15,971)	(95,569)
Cash, cash equivalents, and restricted cash at beginning of period	90,973	106,944	106,944	202,513
Cash, cash equivalents, and restricted cash at end of period	116,856	96,479	90,973	106,944
Non-cash investing and financing activities
Unrealized (loss) gain on available-for-sale securities	(72)	268	406	(313)
Right-of-use assets obtained in exchange for operating lease liability				14,717
Reduction of right-of-use asset due to modification and remeasurement	2,044		(4,904)	(5,506)
Purchase of property and equipment included in AP and accrued expenses				104
Deferred offering costs included in accounts payable and accrued expenses		46
Supplemental disclosure of cash flows
Income taxes paid, net of refunds		351	220	613
Cash and cash equivalents	116,856	95,627	90,121	106,092
Restricted cash		852	852	852
Total cash, cash equivalents, and restricted cash	$ 116,856	$ 96,479	$ 90,973	$ 106,944

Related Party Transactions	9 Months Ended	12 Months Ended
Related Party Transactions	Sep. 30, 2024	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	12. Related Party Transactions In March 2020, the Company entered into a Management and Administrative Services Agreement with ElevateBio Technologies, Inc. that provides for ongoing services to the Company in areas such as information technology, human resources and administration management, and facilities. The Company is billed monthly for such services at cost, with mark-up for profit on specific services, but including reasonable allocations of employee benefits, facilities and other direct or fairly allocated indirect costs that relate to the associates providing the services. The agreement has an initial term of five years and will automatically renew for successive one year terms, unless earlier terminated under the terms of the agreement. In April 2024, the agreement was terminated effective May 1, 2024. In May 2020, the Company entered into a Development and Manufacturing Services Agreement with ElevateBio BaseCamp, Inc. (“BaseCamp”) pursuant to which BaseCamp provides products and services that are used in the Company’s laboratory operations, including consulting services, project management services, quality control services and cGMP drug product manufacturing. The agreement will expire upon the later of (a) five years from the effective date of January 1, 2019 or (b) the completion of services under all work orders executed prior to the fifth anniversary of the effective date, unless earlier terminated under the terms of the agreement. All services under all work orders have been completed and the agreement expired on January 1, 2024. The Company incurred $0.0 and $1.0 million during the three months ended September 30, 2024 and 2023, respectively, and $0.1 million and $1.6 million during the nine months ended September 30, 2024 and 2023, respectively, related to services provided to the Company by ElevateBio and affiliates and sold $0.1 million of equipment to ElevateBio and affiliates during the three and nine months ended September 30, 2024. At September 30, 2024 and December 31, 2023, the Company owed ElevateBio and affiliates $0.0 million and $0.3 million, respectively, and had no prepaid expenses with ElevateBio and affiliates. In March 2023, the Company entered into a services agreement with Marker Therapeutics, Inc. (“Marker”) pursuant to which Marker provides development services to the Company. Juan Vera, a current director and former executive officer of the Company, is co-founder, director and chief executive officer of Marker. In June 2023, CellReady LLC (“CellReady”) acquired certain manufacturing assets previously owned by Marker, and inherited the service agreement that AlloVir previously maintained with Marker. The Company incurred $0.0 and $0.2 million during the three months ended September 30, 2024 and 2023, respectively, and $0.0 and $0.2 million during the nine months ended September 30, 2024 and 2023, respectively, under the agreement. At September 30, 2024 and December 31, 2023, the Company owed CellReady $0.0 and $0.5 million, respectively. Members of the Company’s management and board of directors received consulting fees totaling $0.0 million and $0.1 million during the three months ended September 30, 2024 and 2023, respectively, and $0.1 million and $0.3 million during the nine months ended September 30, 2024 and 2023, respectively.	14. Related Party Transactions In March 2020, the Company entered into a Management and Administrative Services Agreement with ElevateBio Technologies, Inc. that provides for ongoing services to the Company in areas such as information technology, human resources and administration management, and facilities. The Company is billed monthly for such services at cost, with mark-up for profit on specific services, but including reasonable allocations of employee benefits, facilities and other direct or fairly allocated indirect costs that relate to the associates providing the services. The agreement has an initial term of five years and will automatically renew for successive one year terms, unless earlier terminated under the terms of the agreement. In May 2020, the Company entered into a Development and Manufacturing Services Agreement with ElevateBio BaseCamp, Inc. (“BaseCamp”) pursuant to which BaseCamp provides products and services that are used in the Company’s laboratory operations, including consulting services, project management services, quality control services and cGMP drug product manufacturing (see Note 5). The agreement will expire upon the later of (a) five years from the effective date of January 1, 2019 or (b) the completion of services under all work orders executed prior to the fifth anniversary of the effective date, unless earlier terminated under the terms of the agreement. In August 2022, the Company made a $2.0 million prepayment to BaseCamp for future services. The Company incurred $2.6 million and $3.5 million during the year ended December 31, 2023 and 2022, respectively, related to services provided to the Company by ElevateBio and affiliates. At December 31, 2023 and 2022, the Company owed ElevateBio and affiliates $0.3 million and $0.1 million, respectively and had prepaid expenses with ElevateBio and affiliates of $0 and $2.0 million, respectively. In March 2023, the Company entered into a services agreement with Marker Therapeutics, Inc. (“Marker”) pursuant to which Marker provides development services to the Company. Juan Vera, a current director and former executive officer of the Company, is co-founder, director and chief executive officer of Marker. In June 2023, CellReady LLC (“CellReady”) acquired certain manufacturing assets previously owned by Marker, and inherited the service agreement that Allovir previously maintained with Marker. The Company incurred $0.5 million during the year ended December 31, 2023, under the agreement. At December 31, 2023, the Company owed CellReady $0.5 million. Members of the Company’s management and board of directors received consulting fees totaling $0.4 million and $0.5 million during the years ended December 31, 2023 and 2022, respectively.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
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-Paragraph 1
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-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Sponsored Research, Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2023
Research and Development [Abstract]
Sponsored Research, Collaboration and License Agreements	8. Sponsored Research, Collaboration and License Agreements Amended and Restated Exclusive License Agreement with BCM In June 2017, the Company signed a License Agreement (the “License Agreement”) with BCM, whereby the Company acquired a royalty-bearing, worldwide, exclusive license to BCM’s rights in Subject Technology and related patent rights in the field of viral infection. In May 2020, the Company amended and restated the License Agreement (the “A&R License Agreement”), pursuant to which the Company obtained (a) an exclusive worldwide license, with the right to sublicense, under certain patent rights and other intellectual property rights of BCM, to make, have made, use, market, sell, offer to sell, lease, import and export products in a particular field, except that such license is non-exclusive within a particular subfield, and in addition with respect to certain patent rights such license is limited to two particular subfields, and (b) an exclusive, worldwide sublicense, with the right to further sublicense, under all patent rights and other intellectual property rights that are exclusively licensed to BCM by a certain third party licensor, to make, have made, use, market, sell, offer to sell, lease, import and export products in the same field. The Company’s rights are subject to the rights of the U.S. government and certain rights retained by BCM. Unless earlier terminated, the A&R License Agreement will expire on a country-by-country basis with respect to a product upon the later of (a) the expiration of the last to expire valid claim of a patent or patent application covering such product in such country or (b) 10 years after the first commercial sale of such product in such country. The Company may terminate the A&R License Agreement in its entirety at any time for convenience upon a certain number of days’ written notice. BCM may terminate the A&R License Agreement in its entirety for the Company’s uncured material default. BCM maintains control of all filing, prosecution and maintenance of its patent rights licensed by the Company, and the Company is responsible for all related costs and expenses during the term of the agreement. The Company also reimbursed BCM for costs and expenses (including reasonable legal fees and expenses) incurred prior to the effective date of the agreement with respect to the filing, prosecution and maintenance of the patent rights licensed by the Company. If BCM licenses the patent rights licensed by the Company to third parties for additional fields of use, the Company’s responsibility for patent related costs and expenses will be reduced on a pro-rata basis. Under the A&R License Agreement, the Company must use commercially reasonable efforts to develop and commercialize one or more products in certain countries. As partial consideration for the rights conveyed by BCM under the original agreement executed in June 2017, the Company paid BCM a non-refundable license fee of $250,000. During the term of the A&R License Agreement, the Company is obligated to pay BCM a non-refundable annual license maintenance fee, but beginning with the fifth year after the original agreement date, license maintenance fees are fully creditable against royalty revenue due in the applicable year. The Company is required to pay certain milestone payments upon the achievement of specified clinical, regulatory, and sales milestones. In the event that the Company is able to successfully develop, launch and commercialize a product under the A&R License Agreement, total milestone payments could exceed $40.0 million. BCM is also eligible to receive tiered royalties at percentage rates ranging from less than 1% to the low single-digits, on net sales of any products that are commercialized by the Company or its sublicensees that incorporate, utilize or are made with the use of, the intellectual property licensed by the Company. To the extent the Company sublicenses its license rights under the A&R License Agreement, BCM would be eligible to receive tiered sublicense income at percentage rates in the mid-single to low double-digits. In November 2020, the Company also entered into the First Amendment (the “License Amendment”) to the A&R License Agreement. Under the License Amendment, the Company assumed responsibility from BCM for the filing, prosecution and maintenance of the patent rights licensed by the Company from BCM under the A&R License Agreement that are in common with the License Agreement. Further, BCM also transferred to the Company the right of enforcement against third parties for any suspected infringement of any claims in such patent rights or misuse, misappropriation, theft or breach of confidence of other proprietary rights. Exclusive License Agreement with BCM In November 2020, the Company signed a second License Agreement (the “Second License Agreement) with BCM, whereby the Company acquired a royalty-bearing, worldwide, exclusive license to BCM’s rights in Subject Technology and related patent rights outside the field of viral infection (all fields other than those covered by the A&R License Agreement). Unless earlier terminated, the Second License Agreement will expire on a country-by-country basis with respect to a product upon the later of (a) the expiration of the last to expire valid claim of a patent or patent application covering such product in such country or (b) 10 years after the first commercial sale of such product in such country, provided that the Second License Agreement shall not expire later than March 25, 2040. The Company may terminate the Second License Agreement in its entirety at any time for convenience upon a certain number of days’ written notice. BCM may terminate the Second License Agreement in its entirety for the Company’s uncured material default. Under the Second License Agreement, BCM transferred to the Company control of all filing, prosecution and maintenance of the patent rights licensed by the Company, and the Company is responsible for all related costs and expenses during the term of the Second License Agreement. BCM also transferred to the Company the right of enforcement against third parties for any suspected infringement of any claims in the patent rights or misuse, misappropriation, theft or breach of confidence of other proprietary rights. The Company also reimbursed BCM for costs and expenses (including reasonable legal fees and expenses) incurred prior to the effective date of the Second License Agreement with respect to the filing, prosecution and maintenance of the patent rights licensed by the Company, to the extent not already paid by the Company under the A&R License Agreement. Under the Second License Agreement, the Company must use commercially reasonable efforts to develop and commercialize one or more products in certain countries. As partial consideration for the rights conveyed by BCM under the Second License Agreement, the Company paid BCM a non-refundable license fee of $125,000. During the term of the Second License Agreement, the Company is obligated to pay BCM a non-refundable annual license maintenance fee of (a) $20,000 for the first through fourth anniversary of the effective date of the Second License Agreement, and (b) $40,000 for the fifth anniversary of the effective date and continuing thereafter, but beginning with the fifth year, license maintenance fees are fully creditable against royalty revenue due in the applicable year. The Company is required to pay certain milestone payments upon the achievement of specified clinical, regulatory, and sales milestones. In the event that the Company is able to successfully develop, launch and commercialize multiple products under the Second License Agreement, total milestone payments could exceed $30.0 million. BCM is also eligible to receive tiered royalties at percentage rates ranging from less than 1% to the low single-digits, on net sales of any products that are commercialized by the Company or its sublicensees that incorporate, utilize or are made with the use of, the intellectual property licensed by the Company. To the extent the Company sublicenses its license rights under the Second License Agreement, BCM would be eligible to receive tiered sublicense income at percentage rates in the mid-single to low double-digits. Collaboration Agreement with BCM In November 2020, the Company entered into a Research Collaboration Agreement (the “Research Agreement”) with BCM, under which the Company agreed to pay BCM for performing certain research activities under the direction of Dr. Ann Leen commencing on January 1, 2021 and continuing for a three-year period thereafter. The Research Agreement requires the Company to make payments to BCM totaling approximately $6.0 million over the term of the Research Agreement. In August 2023, the Research Agreement was extended for an additional year, expiring December 31, 2024. Collectively under the agreements above and for services provided by BCM the Company paid $2.0 million and $2.5 million during the years ended December 31, 2023 and 2022, respectively, and the payments were classified in research and development expense in the consolidated statements of operations and comprehensive loss. CPRIT Grant In August 2017, the Company was awarded a grant (the “CPRIT Grant”) from the Cancer Prevention and Research Institute of Texas (“CPRIT”). The CPRIT Grant required that the Company grant CPRIT a non-commercial license to technology developed under the grant and pay CPRIT a share of revenue on sales of commercial products developed using CPRIT funds equal to low single digits of revenue until such time as CPRIT has been paid an aggregate amount equal to 400% of the grant award proceeds. No royalty payments were made under this license agreement during the years ended December 31, 2023 and 2022, respectively. Redeemable Preferred Stock Redemption Agreement In September 2018, the Company entered into a redeemable preferred stock redemption agreement, or Redemption Agreement, to redeem shares of our Series A1 convertible preferred stock held by certain investors, including executive officer Ann Leen, director and former executive officer Juan Vera and entities affiliated with director, Malcolm Brenner and former director, John Wilson (or their affiliates). Pursuant to the Redemption Agreement, for a period of 20 years from the date of the first commercial sale of Viralym-M (now posoleucel), the Company is obligated to make earnout payments to such investors on at least an annual basis. The earnout payments will be 10% of net sales of Viralym-M, which number will be reduced to a high single-digit percentage if certain events occur. Specifically, royalties due to third parties for the sale of Viralym-M are subtracted from the earnout payments due to the investors. Further, if the investors receive at least $50,000,000 in earnout payments from AlloVir during the three-year period after the first commercial sale of Viralym-M, the earnout payment percentage will be reduced.

Accrued Expenses (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Employee compensation and benefits	$	739	$	3,809
Professional fees		547		435
Research and development		—		2,442
Process development and manufacturing costs		—		2,367
Other		75		1,033

Total accrued expenses	$	1,361	$	10,086

Accrued expenses consisted of the following:


	December 31,
(in thousands)	2023		2022
Employee compensation and benefits	$	3,809	$	6,416
Professional fees		435		559
Research and development		2,442		5,678
Process development and manufacturing costs		2,367		504
Other		1,033		828

Total accrued expenses	$	10,086	$	13,985

Stockholders Equity - Additional Information (Details)			12 Months Ended
Stockholders Equity - Additional Information (Details)	Jun. 21, 2023 USD ($) $ / shares shares	Jul. 26, 2022 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) Vote $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Sep. 30, 2024 $ / shares shares	May 15, 2023 $ / shares shares
Class Of Stock [Line Items]
Preferred stock, par or stated value per share \| $ / shares			$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized \| shares			10,000,000	10,000,000	10,000,000	10,000,000
Preferred stock, shares issued \| shares			0	0	0
Preferred stock, shares outstanding \| shares			0	0	0
Common stock, shares authorized \| shares			300,000,000	150,000,000	300,000,000	300,000,000
Common stock, par value \| $ / shares			$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Proceeds from issuance of common stock				$ 126,425,000
Number of votes per share \| Vote			1
Common stock, voting rights			The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders (and written actions in lieu of meetings), and there are not any cumulative voting rights. The number of authorized shares of common stock may be increased or decreased by the affirmative vote of the holders of shares of capital stock of the Company; however, the issuance of common stock may be subject to the vote of the holders of one or more series of preferred stock that may be required by terms of the Third Amended and Restated Certificate of Incorporation.
Cash dividends declared or paid			$ 0
Underwriter \| J.P. Morgan Securities LLC
Class Of Stock [Line Items]
Stock issued \| shares	20,000,000
Offering price per share \| $ / shares	$ 3.75
Proceeds from issuance of common stock	$ 70,200,000
Offering costs	$ 300,000
Option to purchase additional number of shares \| shares	3,000,000
Expiration of option to purchase additional number of shares	Jul. 21, 2023
Underwriting discounts commissions	$ 4,500,000
Securities Purchase Agreement
Class Of Stock [Line Items]
Common stock, par value \| $ / shares		$ 0.0001
Net proceeds with certain investors		$ 126,400,000
Offering costs		$ 200,000
Share issued to investors \| shares		27,458,095
Underwriting discounts commissions		$ 0
Offering price per share \| $ / shares		$ 4.61

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par or stated value per share	$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000
Preferred stock, shares issued	0	0	0
Preferred stock, shares outstanding	0	0	0
Common stock, par value	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000	150,000,000
Common stock, shares issued	115,438,119	114,153,538	93,268,069
Common stock, shares outstanding	115,438,119	114,148,991	93,093,243

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 116,856	$ 90,121	$ 106,092
Short-term investments	4,995	93,822	127,703
Interest receivable	53	206	157
Prepaid expenses and other current assets	626	3,486	7,100
Prepaid expenses to related party			2,000
Total current assets	122,530	187,635	243,052
Restricted cash		852	852
Other assets		122	612
Property and equipment, net			930
Operating lease right-of-use assets		2,187	31,633
Total assets	122,530	190,796	277,079
Current liabilities:
Accounts payable	51	6,761	3,004
Accrued expenses	1,361	10,086	13,985
Income tax payable			128
Operating lease liability, current		10,781	7,165
Total current liabilities	1,412	28,367	24,338
Operating lease liability, long term		16,648	28,222
Total liabilities	1,412	45,015	52,560
Stockholders' equity:
Preferred stock
Common stock	11	11	9
Additional paid-in capital	817,935	802,025	690,753
Accumulated other comprehensive loss	(134)	(62)	(468)
Accumulated deficit	(696,694)	(656,193)	(465,775)
Total stockholders' equity	121,118	145,781	224,519
Total liabilities and stockholders' equity	$ 122,530	190,796	277,079
Related Party
Current liabilities:
Amount due to related party		$ 739	$ 56

Income Taxes

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

9. Income Taxes

The Company’s income tax provision is computed based on the federal statutory rate, the average state statutory rates, net of the related federal benefit, and foreign statutory rates. For the three months ended September 30, 2024 and 2023, the Company did not record income tax expense due to the generation of net operating losses, the benefits of which have been fully reserved.

The Company’s estimate of the realizability of the deferred tax asset is dependent on estimates of projected future levels of taxable income. In consideration of historical losses and in analyzing future taxable income levels, the Company considered all evidence currently available, both positive and negative, and has

t recognized deferred tax assets.

11. Income Taxes

Income (loss) before provision for income taxes consisted of the following:


	Years Ended December 31,
(in thousands)	2023			2022
Federal		(376,152	)		(113,389	)
Foreign		185,608			(55,586	)

Loss before provision for income taxes		$(190,544)		$	(168,975	)

The provision for income taxes for the years ended December 31, 2023 and 2022 consisted of the following:


	Years Ended December 31,
(in thousands)	2023			2022
Current income tax (benefit) expense:
Federal	$	(136	)		(246	)
State		10			(19	)
Foreign		—			—

Total current income tax benefit		(126)			(265	)

Deferred income tax (benefit) expense:
Federal		—			—
State		—			—
Foreign		—			—

Total deferred income tax benefit		—			—

Total income tax benefit	$	(126	)	$	(265	)

The Company’s income tax benefit for the years ended December 31, 2023 and 2022 relating to federal, state and foreign tax jurisdictions differs from the amounts determined by applying the statutory federal income tax rate based on the following:


	Years Ended December 31,
(in thousands)	2023					2022
Benefit at the federal rate	$	(40,015	)	21.0	%	$	(35,472	)	21.0	%
Increase (decrease) resulting from:
Foreign tax rate differential		(15,783	)	8.3	%		2,177		(1.3	)%
State taxes, net of federal benefit		(9,514	)	5.0	%		(1,603	)	0.9	%
Change in valuation allowance		98,714		(51.8	)%		35,406		(21.0	)%
Intercompany note impairment		(34,615	)	18.2	%		—		—
Tax credits		(5,928	)	3.1	%		(6,992	)	4.1	%
Officer's compensation		177		(0.1	)%		695		(0.4	)%
Stock compensation		4,564		(2.4	)%		4,637		(2.7	)%
Impairment of intellectual property		3,003		(1.6	)%		—		—
Permanent differences		79		0.0	%		(182	)	0.1	%
Change in state tax law		384		(0.2	)%		—		—
Other		(1,192	)	0.6	%		1,069		(0.6	)%

Total income tax benefit	$	(126	)	0.1	%	$	(265	)	0.1	%

In 2021, the Company transferred intellectual property rights between tax jurisdictions, resulting in a deferred tax asset on the basis difference in the intangible assets. In addition, in connection with the transfer of the intellectual property the Company recorded intercompany notes between the parties. In December 2023, the Company determined that the intellectual property intangible assets and intercompany notes were impaired resulting in the recognition of income or loss in the respective jurisdiction.

Components of deferred income taxes consist of the following:


	December 31,
(in thousands)	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	54,081		$	9,374
Tax credit carryforwards		19,378			12,374
Intangible assets		—			25,537
Intercompany note impairment		64,087
Operating lease liabilities		6,348			8,074
Non-qualified stock compensation		15,435			12,017
Restricted stock compensation		680			235
Capitalization of R&D expenses		20,758			20,375
Other		676			1,661

Total deferred tax assets		181,443			89,647

Valuation allowance		(180,943	)		(82,228	)

Net deferred tax assets	$	500		$	7,419

Deferred tax liabilities:
Operating lease right-of-use assets		(506	)		(7,218	)
Depreciation		4			(186	)
Other		2			(15	)

Total deferred tax liabilities		(500	)		(7,419	)

Net deferred tax asset (liability)	$	—		$	—

The Company’s accounting for deferred taxes involves the evaluation of a number of factors concerning the realizability of its net deferred tax assets. The Company primarily considered such factors as its history of operating losses, the nature of the Company’s deferred tax assets, and the timing, likelihood and amount, if any, of future taxable income during the periods in which those temporary differences and carryforwards become deductible. At December 31, 2023 and 2022, the Company does not believe that it is more likely than not that the deferred tax assets will be realized; accordingly, a full valuation allowance has been established and no deferred tax asset is shown in the accompanying consolidated balance sheets. For the year ended December 31, 2023, the valuation allowance for deferred tax assets increased by $98.7 million, which was principally due to increased deffered taxes for net operating losses and intercompany note impairment. For the year ended December 31, 2022, the valuation allowance for deferred tax assets increased by $35.4 million, which was principally due to net operating losses, tax credits, tax basis generated from the intellectual property transfer, and U.S. research and development expense capitalization.

At December 31, 2023 and 2022, the Company had unused federal net operating loss carryforwards of $38.9 million and $0, respectively. The federal net operating loss carryforwards have no expiration, and are limited in utilization to 80% of taxable income. The CARES Act temporarily allows the Company to carryback net operating losses arising in 2018, 2019 and 2020 to the

five

prior tax years. In addition, net operating losses

generated in these years could fully offset prior year taxable income without the 80% of the taxable income limitation under the TCJA which was enacted on December 22, 2017. The Company has been generating losses since its inception, as such the net operating loss carryback provision under the CARES Act is not applicable to the Company.

At December 31, 2023 and 2022, the Company had unused state net operating loss carryforwards of $26.4 million and $3.6 million, respectively. The state net operating loss carryforwards expire in 2035.

At December 31, 2023 and 2022, the Company had unused foreign net operating loss carryforwards of $354.8 million and $72.9 million, respectively. The foreign net operating loss carryforwards have no expiration.

At December 31, 2023 and 2022, the Company had $11.7 million and $6.6 million of federal research and development tax credit carryforwards that may be available to offset future federal income taxes through 2040. Additionally, at December 31, 2023, the Company had a federal orphan drug credit (ODC) carryforward related to qualifying research of $6.0 million that will begin to expire in 2041. At December 31, 2023 and 2022, the Company also had $2.1 million and $1.3 million of research and development tax credit carryforwards that may be available to offset future state income taxes in the state of Massachusetts through 2035.

Utilization of net operating loss and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended, due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss and research and development tax credit carryforwards that can be utilized annually to offset future taxable income and tax expense, respectively. The Company has completed several financings since its inception which may result in a change of control as defined in Section 382 of the Internal Revenue Code or could result in a change in control in the future.

The Company complies with the provisions of ASC 740 in accounting for its uncertain tax positions. ASC 740 addresses the determination of whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the consolidated financial statements. Under ASC 740, the Company may recognize the tax benefit from an uncertain tax position only if it is more likely that not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. At December 31, 2023 and 2022, the Company had no uncertain tax positions.

The Company recognizes interest accrued related to unrecognized tax benefits and penalties in income tax expense. The Company had no accruals for interest and penalties at December 31, 2023 and 2022.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. The statute of limitations for assessment by the Internal Revenue Service and state tax authorities remains open for the tax years

December 31, 2020 through December 31, 2023

as the Company was incorporated in September 2018. There are currently no federal, state or foreign income tax audits in progress. The resolution of tax matters is not expected to have a material effect on the Company’s consolidated financial statements.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2003/role/exampleRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
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-Paragraph 12C
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 12B
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Section S99
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 17
-Subparagraph (b)
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
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-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Stock-Based Compensation - Additional Information (Details) - USD ($)				1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 01, 2023	Jan. 01, 2022	Jul. 02, 2020	Jul. 31, 2020	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	May 15, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved shares of common stock for issuance					23,868,676		23,868,676		18,357,134	14,869,885
Common stock, par value					$ 0.0001		$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001
Stock-based compensation expense					$ 4,947,000	$ 10,468,000	$ 15,889,000	$ 30,785,000	$ 40,779,000	$ 41,315,000
Accelerated units					0		664,248
Accelerating recognition cost							$ 100,000
Reversal of stock-based compensation expense							4,000,000
Number of options, granted									3,779,342
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense					$ 312,000	3,254,000	232,000	10,191,000	$ 13,167,000	14,014,000
Reversal of stock-based compensation expense							2,400,000
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense					4,635,000	$ 7,214,000	15,657,000	20,594,000	$ 27,612,000	27,301,000
Reversal of stock-based compensation expense							$ 1,600,000
Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares granted							245,000		2,279,994
Unrecognized stock-based compensation cost					7,000,000		$ 7,000,000		$ 23,600,000
Weighted average period of cost expected to be recognized							1 year 7 months 6 days		2 years 2 months 12 days
Total fair value of restricted stock vested							$ 900,000	$ 3,000,000	$ 3,600,000	$ 14,200,000
EmployeeStockOptionMember
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period of cost expected to be recognized							1 year 6 months 7 days		1 year 11 months 1 day
Weighted average grant-date fair value of stock options granted								$ 4.92	$ 4.88	$ 5.61
Unrecognized stock-based compensation expenses					$ 8,900,000		$ 8,900,000		$ 36,900,000
Number of options, granted							0
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards vesting period									4 years
Awards contractual term									10 years
Number of shares of common stock issuable upon exercise of outstanding options									64,042
Reserved shares of common stock for issuance									0
2018 Equity Incentive Plan \| Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares granted									6,616,772
2020 Stock Option and Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards vesting period			4 years
Awards contractual term			10 years
Common stock authorized for issuance			8,008,734
Cumulative increase in number shares reserved for issuance, percentage			5.00%
Shares added to number of available shares under plan	4,663,403	160,000
Common stock issuable upon exercise of outstanding options									10,375,709
2020 Stock Option and Grant Plan \| Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares granted									5,356,510
2020 Stock Option and Grant Plan \| Stock Available For Grant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved shares of common stock for issuance					15,091,301		15,091,301		4,182,461	4,253,680
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved shares of common stock for issuance				611,354	1,585,257		1,585,257		480,059
Percentage of payroll deductions of base salary or wages				15.00%
Percentage of maximum discount on purchase of shares of common stock				15.00%
Offering period, description									(i) on the first trading day of the offering period or (ii) the last day of any offering period. The Company utilizes the Black Scholes option pricing model to compute the fair market value of the shares and compensation expense is recognized over the offering period. Six-month offering periods commence each January 1 and July 1 during the term of the plan, with the administrator having the right to establish different offering periods.
Cumulative increase in number shares reserved for issuance, percentage				1.00%
Common stock, par value				$ 0.0001
Annual increase in number of shares reserved for issuance				1,222,707
Purchase of common stock under the employee stock purchase plan							36,337		134,243
Share issued, average price per share					$ 0.58		$ 0.58		$ 2.43
Cash received from purchases under the ESPP							$ 0	$ 300,000	$ 300,000	$ 500,000
Stock-based compensation expense							$ 0	$ 300,000	$ 300,000	$ 200,000
2020 Employee Stock Purchase Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Base salary or wages				$ 25,000

Short-Term Investments (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Estimated Fair Value of Marketable Securities

The following tables summarize the amortized cost and estimated fair value of the Company’s U.S. government treasury securities and marketable securities, which are considered to be

available-for-sale

investments and are included in short-term investments on the consolidated balance sheets:


	September 30, 2024
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. government treasury securities	$	4,994	$	1	$	—	$	4,995

Totals	$	4,994	$	1	$	—	$	4,995


	December 31, 2023
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. government treasury securities		93,749		73		—	$	93,822

Totals	$	93,749	$	73	$	—	$	93,822

The following tables summarize the amortized cost and estimated fair value of the Company’s U.S. government treasury securities and marketable securities, which are considered to be

available-for-sale

investments and are included in short-term investments on the consolidated balance sheets:


	December 31, 2023
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government treasury securities	$	93,749	$	73	$	—		$	93,822

Totals	$	93,749	$	73	$	—		$	93,822


	December 31, 2022
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government treasury securities	$	99,288	$	1	$	(253	)	$	99,036
Marketable securities:
Corporate and agency bonds		28,748		3		(84	)		28,667

Totals	$	128,036	$	4	$	(337	)	$	127,703

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value On Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash equivalents:
Cash equivalents	$ 113,794	$ 23,854	$ 32,641
Short-term investments:
Short-term investments	4,995	93,822	127,703
Corporate and Agency Bonds
Short-term investments:
Short-term investments			28,667
Money Market Fund
Cash equivalents:
Cash equivalents	113,794	23,854	32,641
U.S. Government Treasury Securities
Short-term investments:
Short-term investments	4,995	93,822	99,036
Level 1
Cash equivalents:
Cash equivalents	113,794	23,854	32,641
Short-term investments:
Short-term investments	4,995	93,822	99,036
Level 1 \| Money Market Fund
Cash equivalents:
Cash equivalents	113,794	23,854	32,641
Level 1 \| U.S. Government Treasury Securities
Short-term investments:
Short-term investments	$ 4,995	$ 93,822	99,036
Level 2
Short-term investments:
Short-term investments			28,667
Level 2 \| Corporate and Agency Bonds
Short-term investments:
Short-term investments			$ 28,667

Summary of Significant Accounting Policies (Policies)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation and Consolidation

Segment Information

off-the-shelf

Use of Estimates

Cash and Cash Equivalents

Short-Term Investments

Short-term investments consist of U.S. treasury securities and corporate bonds classified as

available-for-sale

that have maturities of less than one year.

Available-for-sale

securities are carried at fair value, with the unrealized gains and losses reported in other comprehensive income (loss) until realized. The amortized cost of debt securities

Restricted Cash

non-current

restricted cash in the accompanying consolidated balance sheet at December 31, 2023 and 2022.

Property and Equipment, Net

The Company records property and equipment at cost and

recognizes depreciation using the straight-line method over the estimated useful lives of the respective assets

, as follows:


Asset category		Estimated useful life
Computer equipment		3 years
Laboratory equipment		5 years

Impairment of Long-Lived Assets

The Company accounts for long-lived assets in accordance with ASC Topic 360,

Property, Plant, and Equipment

The Company tests long-lived assets to be held and used, including

right-of-use

Fair Value Measurements

ASC Topic 820,

Fair Value Measurement

•

Level 1 – Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access.

•

Level 3 – Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with

in-process

Cloud Computing Arrangements

The Company capitalizes certain implementation costs for

internal-use

software cost in

impairment loss

of $1.4 million was recognized during the year ended December 31, 2023 for implementation costs associated with cloud computing arrangements that are no longer probable of being implemented.

Other Income (Loss), Net

Research and Development Costs

Accrued Research and Development Expenses

Stock-Based Compensation Expense

non-employees

Net Loss Per Share

Net Loss per Share

Income Taxes

The Company accounts for income taxes under the asset and liability method in accordance with ASC 740,

Income Taxes

Concentration of Credit Risk and Off-Balance Sheet Risk

Concentration of Credit Risk and

Off-Balance

Sheet Risk

At December 31, 2023 and 2022, the Company had no

off-balance

sheet risk.

Foreign Exchange

Comprehensive Loss

Comprehensive loss is defined as a change in equity of a business enterprise during a period, resulting from transactions from

non-owner

sources. Comprehensive loss includes net loss and certain changes in stockholder’s deficit that are excluded from net loss. The Company’s comprehensive loss includes unrealized gains (losses) on

available-for-sale

securities during the year ended December 31, 2023 and 2022.

Leases

In accordance with ASC Topic 842,

Lease Accounting

right-of-use

(“ROU”) asset and current and

non-current

The Company has elected to account for the lease and

non-lease

components together for all existing classes of underlying assets.

Subsequent Events

Recent Accounting Pronouncements

Since December 31, 2023, there have been no new accounting pronouncements adopted by the Company or issued by FASB that are applicable to the Company, except as noted below.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with certain new or revised accounting standards pursuant to Section 107(b) of the JOBS Act.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU

No. 2016-13,

Financial Instruments—Credit Losses

(Topic 326):

Measurement of Credit Losses on Financial

Instruments

, or ASU

2016-13,

which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU

2016-13

replaces the existing incurred loss impairment model with an expected loss model. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to

available-for-sale

2016-13

on January 1, 2023. The adoption of ASU

2016-13

did not have a material impact on the Company’s consolidated financial statements and related disclosures.

Recently Issued Accounting Pronouncements Not Yet Adopted

In November 2023, the FASB issued ASU

2023-07,

Segment Reporting

(Topic 280):

Improvements to Reportable Segment Disclosures

In December 2023, the FASB issued ASU

2023-09,

Income Taxes (Topic 740):

Improvements to Income Tax Disclosures

Recently Issued Accounting Pronouncements Not Yet Adopted

In November 2023, the FASB issued ASU

2023-07,

Segment Reporting

(Topic 280):

Improvements to Reportable Segment Disclosures

, which requires disclosure of incremental segment information on an interim and annual basis. This ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal periods beginning after December 15, 2024, and requires retrospective application to all prior periods presented in the financial statements. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU

2023-09,

Income Taxes (Topic 740):

Improvements to Income Tax Disclosures

Restructuring Costs

The Company records costs and liabilities associated with exit and disposal activities in accordance with ASC 420,

Exit or Disposal Cost

Obligations

(ASC 420). Such costs are based on estimates of fair value in the period liabilities are incurred. Given the short duration of when the liability is

Interim Financial Information

Stock-Based Compensation - Summary of Restricted Common Stock Activity (Details) - Restricted Common Stock - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Number of Shares
Number of Shares, Unvested at January 1, 2024	3,254,863	2,239,106
Number of Shares, Granted	245,000	2,279,994
Number of Shares, Forfeited	(1,126,973)	(342,732)
Number of Shares, Vested	(1,252,791)	(921,505)
Number of Shares, Unvested at September 30, 2024	1,120,099	3,254,863
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Unvested at January 1, 2024	$ 8.73	$ 13.75
Weighted Average Grant Date Fair Value, Granted	0.77	6.02
Weighted Average Grant Date Fair Value, Forfeited	8.34	11.46
Weighted Average Grant Date Fair Value, Vested	8.65	13.24
Weighted Average Grant Date Fair Value, Unvested at September 30, 2024	$ 7.45	$ 8.73

Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Current income tax (benefit) expense:
Federal			$ (136)	$ (246)
State			10	(19)
Total current income tax (benefit) expense			(126)	(265)
Total income tax benefit	$ 0	$ 0	$ (126)	$ (265)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-10

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (a)
-SubTopic 20
-Topic 740
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482659/740-20-45-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-SubTopic 10
-Topic 235
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

Net Loss per Share

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss per Share

10. Net Loss per Share

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:


	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except share and per share data)	2024			2023			2024			2023
Numerator:
Net loss – basic and diluted	$	(4,126	)	$	(44,272	)	$	(40,501	)	$	(130,722	)
Denominator:
Weighted-average common shares outstanding – basic and diluted		115,399,516			113,894,188			115,073,622			100,683,322

Net loss per share – basic and diluted	$	(0.04	)	$	(0.39	)	$	(0.35	)	$	(1.30	)


	September 30,
	2024		2023
Options to purchase common stock		6,072,019		10,445,312
Unvested restricted stock		1,120,099		3,410,391

12. Net Loss per Share

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:


	Years Ended December 31,
(in thousands, except share and per share data)	2023			2022
Numerator:
Net loss – basic and diluted	$	(190,418	)	$	(168,710	)
Denominator:
Weighted-average common shares outstanding – basic and diluted		104,057,220			76,654,856

Net loss per share – basic and diluted	$	(1.83	)	$	(2.20	)


	Years Ended December 31,
	2023		2022
Options to purchase common stock		10,439,751		7,922,797
Unvested restricted stock		3,254,863		2,239,106

Restructuring Costs - Details of Restructuring Liability Included in Accrued Expenses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
Restructuring and Related Activities [Abstract]
Balance		$ 0
Restructuring charges	$ 100	10,059
Cash payments		9,939
Balance	$ 120	$ 120

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Employee compensation and benefits	$ 739	$ 3,809	$ 6,416
Professional fees	547	435	559
Research and development		2,442	5,678
Process development and manufacturing costs		2,367	504
Other	75	1,033	828
Total accrued expenses	$ 1,361	$ 10,086	$ 13,985

Income Taxes - Summary of Components of Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 54,081	$ 9,374
Tax credit carryforwards	19,378	12,374
Intangible Assets		25,537
Intercompany note impairment	64,087
Operating lease liabilities	6,348	8,074
Non-qualified stock compensation	15,435	12,017
Restricted stock compensation	680	235
Capitalization of R&D expenses	20,758	20,375
Other	676	1,661
Total deferred tax assets	181,443	89,647
Valuation allowance	(180,943)	(82,228)
Net deferred tax assets	500	7,419
Deferred tax liabilities:
Operating lease right-of-use assets	(506)	(7,218)
Depreciation	4	(186)
Other	2	(15)
Total deferred tax liabilities	$ (500)	$ (7,419)

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Estimated Useful Life

The Company records property and equipment at cost and

recognizes depreciation using the straight-line method over the estimated useful lives of the respective assets

, as follows:


Asset category		Estimated useful life
Computer equipment		3 years
Laboratory equipment		5 years

Net Loss per Share - Computation Of Basic And Diluted Net Loss Per Share Attributable To Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Numerator:
Net loss – basic and diluted	$ (4,126)	$ (44,272)	$ (40,501)	$ (130,722)	$ (190,418)	$ (168,710)
Denominator:
Weighted-average common shares outstanding – basic	115,399,516	113,894,188	115,073,622	100,683,322	104,057,220	76,654,856
Weighted-average common shares outstanding – diluted	115,399,516	113,894,188	115,073,622	100,683,322	104,057,220	76,654,856
Net loss per share – basic	$ (0.04)	$ (0.39)	$ (0.35)	$ (1.3)	$ (1.83)	$ (2.2)
Net loss per share – diluted	$ (0.04)	$ (0.39)	$ (0.35)	$ (1.3)	$ (1.83)	$ (2.2)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

+ References + Details

Net Loss per Share - Potential Dilutive Securities Excluded From Computation Of Diluted Net Loss Per Share Attributable To Common Stockholders (Details) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Options To Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	6,072,019	10,445,312	10,439,751	7,922,797
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1,120,099	3,410,391	3,254,863	2,239,106

Accrued Expenses - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Restructuring liability	$ 120	$ 0

Stockholder's Equity (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Equity [Abstract]

Schedule of Reserved Shares of Common Stock for Issuance

The Company has reserved shares of common stock for issuance as follows:


	September 30,		December 31,
	2024		2023
Options to purchase common stock		6,072,019		10,439,751
Unvested restricted stock		1,120,099		3,254,863
Stock available for grant under the 2020 Stock Option and Grant Plan		15,091,301		4,182,461
Stock available for issuance under the 2020 Employee Stock Purchase Plan		1,585,257		480,059

Total		23,868,676		18,357,134

The Company has reserved shares of common stock for issuance as follows:


	December 31,
	2023		2022
Unvested restricted stock		3,254,863		2,239,106
Options to purchase common stock		10,439,751		7,922,797
Stock available for grant under the 2020 Stock Option and Grant Plan		4,182,461		4,253,680
Stock available for issuance under the 2020 Employee Stock Purchase Plan		480,059		454,302

Total		18,357,134		14,869,885

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 31, 2021	$ 225,266	$ 7	$ 522,479	$ (155)	$ (297,065)
Balance, Shares at Dec. 31, 2021		63,565,886
Stock-based compensation	41,315		41,315
Issuance of common stock, upon vesting of restricted stock, Shares		1,912,210
Purchase of common stock under the 2020 Employee Stock Purchase Plan	536		536
Purchase of common stock under the 2020 employee stock purchase plan, Shares		157,052
Issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs	126,425	$ 2	126,423
Issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs, Shares		27,458,095
Unrealized gain (loss) on available-for-sale securities	(313)			(313)
Net loss	(168,710)				(168,710)
Balance at Dec. 31, 2022	224,519	$ 9	690,753	(468)	(465,775)
Balance, Shares at Dec. 31, 2022		93,093,243
Stock-based compensation	10,029		10,029
Issuance of common stock, upon vesting of restricted stock, Shares		334,747
Unrealized gain (loss) on available-for-sale securities	167			167
Net loss	(41,183)				(41,183)
Balance at Mar. 31, 2023	193,532	$ 9	700,782	(301)	(506,958)
Balance, Shares at Mar. 31, 2023		93,427,990
Balance at Dec. 31, 2022	224,519	$ 9	690,753	(468)	(465,775)
Balance, Shares at Dec. 31, 2022		93,093,243
Unrealized gain (loss) on available-for-sale securities	268
Net loss	(130,722)
Balance at Sep. 30, 2023	195,334	$ 11	792,020	(200)	(596,497)
Balance, Shares at Sep. 30, 2023		113,966,594
Balance at Dec. 31, 2022	224,519	$ 9	690,753	(468)	(465,775)
Balance, Shares at Dec. 31, 2022		93,093,243
Stock-based compensation	40,779		40,779
Issuance of common stock, upon vesting of restricted stock, Shares		921,505
Purchase of common stock under the 2020 Employee Stock Purchase Plan	326		326
Purchase of common stock under the 2020 employee stock purchase plan, Shares		134,243
Issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs	70,169	$ 2	70,167
Issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs, Shares		20,000,000
Unrealized gain (loss) on available-for-sale securities	406			406
Net loss	(190,418)				(190,418)
Balance at Dec. 31, 2023	145,781	$ 11	802,025	(62)	(656,193)
Balance, Shares at Dec. 31, 2023		114,148,991
Balance at Mar. 31, 2023	193,532	$ 9	700,782	(301)	(506,958)
Balance, Shares at Mar. 31, 2023		93,427,990
Stock-based compensation	10,288		10,288
Issuance of common stock, upon vesting of restricted stock, Shares		179,092
Purchase of common stock under the 2020 Employee Stock Purchase Plan	315		315
Purchase of common stock under the 2020 employee stock purchase plan, Shares		108,936
Issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs	70,169	$ 2	70,167
Issuance of common stock in public offering, net of underwriting discounts, commissions and offering costs, Shares		20,000,000
Unrealized gain (loss) on available-for-sale securities	76			76
Net loss	(45,267)				(45,267)
Balance at Jun. 30, 2023	229,113	$ 11	781,552	(225)	(552,225)
Balance, Shares at Jun. 30, 2023		113,716,018
Stock-based compensation	10,468		10,468
Issuance of common stock, upon vesting of restricted stock, Shares		250,576
Unrealized gain (loss) on available-for-sale securities	25			25
Net loss	(44,272)				(44,272)
Balance at Sep. 30, 2023	195,334	$ 11	792,020	(200)	(596,497)
Balance, Shares at Sep. 30, 2023		113,966,594
Balance at Dec. 31, 2023	145,781	$ 11	802,025	(62)	(656,193)
Balance, Shares at Dec. 31, 2023		114,148,991
Stock-based compensation	5,034		5,034
Issuance of common stock, upon vesting of restricted stock, Shares		732,774
Unrealized gain (loss) on available-for-sale securities	(76)			(76)
Net loss	(30,299)				(30,299)
Balance at Mar. 31, 2024	120,440	$ 11	807,059	(138)	(686,492)
Balance, Shares at Mar. 31, 2024		114,881,765
Balance at Dec. 31, 2023	145,781	$ 11	802,025	(62)	(656,193)
Balance, Shares at Dec. 31, 2023		114,148,991
Unrealized gain (loss) on available-for-sale securities	(72)
Net loss	(40,501)
Balance at Sep. 30, 2024	121,118	$ 11	817,935	(134)	(696,694)
Balance, Shares at Sep. 30, 2024		115,438,119
Balance at Mar. 31, 2024	120,440	$ 11	807,059	(138)	(686,492)
Balance, Shares at Mar. 31, 2024		114,881,765
Stock-based compensation	5,908		5,908
Issuance of common stock, upon vesting of restricted stock, Shares		394,309
Purchase of common stock under the 2020 Employee Stock Purchase Plan	21		21
Purchase of common stock under the 2020 employee stock purchase plan, Shares		36,337
Unrealized gain (loss) on available-for-sale securities	(1)			(1)
Net loss	(6,076)				(6,076)
Balance at Jun. 30, 2024	120,292	$ 11	812,988	(139)	(692,568)
Balance, Shares at Jun. 30, 2024		115,312,411
Stock-based compensation	4,947		4,947
Issuance of common stock, upon vesting of restricted stock, Shares		125,708
Unrealized gain (loss) on available-for-sale securities	5			5
Net loss	(4,126)				(4,126)
Balance at Sep. 30, 2024	$ 121,118	$ 11	$ 817,935	$ (134)	$ (696,694)
Balance, Shares at Sep. 30, 2024		115,438,119

Leases - Additional Information (Details) - USD ($)	1 Months Ended						3 Months Ended		9 Months Ended		12 Months Ended
Leases - Additional Information (Details) - USD ($)	Jul. 31, 2024	Jun. 30, 2024	Feb. 29, 2024	Dec. 31, 2023	Oct. 31, 2022	Sep. 30, 2021	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Leases [Line Items]
ROU asset				$ 2,187,000							$ 2,187,000	$ 31,633,000
Lease liability				27,429,000							27,429,000
Remaining right-of-use asset balance				$ 2,200,000							2,200,000
Operating lease costs							$ 0	$ 2,600,000	$ 600,000	$ 7,700,000	9,700,000	6,600,000
Cash paid for operating lease							7,000,000	800,000	17,000,000	3,900,000	4,800,000	4,800,000
Variable lease costs							0	200,000	100,000	900,000	$ 900,000	$ 3,700,000
Operating lease, weighted average remaining lease term				4 years 8 months 12 days							4 years 8 months 12 days	6 years 11 months 4 days
Operating lease, weighted average discount rate, percent				5.95%							5.95%	6.23%
Impairment loss to operating lease right-of-use assets				$ 16,600,000			$ 0	$ 0	$ 0	$ 0	$ 16,600,000
Waltham Leases
Leases [Line Items]
Expiration date						Jul. 30, 2030
Lease, option to extend											The Company has the option to renew the leased space for an additional one time period of five years with written notice from the Company. As of December 31, 2023, the Company has no reasonable certainty that this option to extend will be exercised.
Lease commencement month and year						2021-09
Additional one time lease period						5 years
Tenant improvement allowance to be reimbursed				900,000		$ 3,100,000					$ 900,000
New Lease Agreement with BP Bay Colony LLC
Leases [Line Items]
ROU asset						6,000,000
Lease liability						6,000,000
Sublease with AMAG Pharmaceuticals
Leases [Line Items]
ROU asset						17,300,000
Lease liability						$ 17,300,000
2022 SOW Under the DMS Agreement
Leases [Line Items]
Lease expiration month and year					2024-12
ROU asset					$ 14,700,000
Lease liability					14,700,000
Reduction to right-of-use asset and lease liability				$ 4,900,000
Utilization fee					$ 16,300,000
Lessee operating lease, lease term including renewal option					2 years 3 months
Sublease Agreement with AMAG Pharmaceuticals Inc.
Leases [Line Items]
Gain on termination of lease		$ 1,800,000
Lease, termination date		Jun. 30, 2024
Termination fee paid		$ 5,700,000
2024 SOW Under the DMS Agreement
Leases [Line Items]
Gain on termination of lease			$ 5,600,000
Termination Agreement with BP Bay Colony LLC
Leases [Line Items]
Gain on termination of lease	$ 1,500,000
Termination fee paid	$ 7,000,000

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Increase in deferred tax assets valuation allowance			$ 98,714,000	$ 35,406,000
Operating loss carryforwards carryback period			5 years
Percentage of TCJA limitations on net operating loss carryforwards to taxable income			80.00%
Uncertain tax positions			$ 0	0
Unrecognized tax benefits, interest and penalties accrued			$ 0	0
Open tax year			2020 2023
Income tax expense	$ 0	$ 0	$ (126,000)	(265,000)
Net Operating Losses, Tax Credits
Income Taxes [Line Items]
Increase in deferred tax assets valuation allowance				35,400,000
Federal
Income Taxes [Line Items]
Operating loss carryforwards			38,900,000	0
Federal \| Research and Development
Income Taxes [Line Items]
Tax credit carryforwards			$ 11,700,000	6,600,000
Tax credit carryforwards expiration year			2040
Federal \| Orphan Drug Credit (ODC)
Income Taxes [Line Items]
Tax credit carryforwards			$ 6,000,000
Tax credit carryforwards expiration year			2041
State
Income Taxes [Line Items]
Operating loss carryforwards			$ 26,400,000	3,600,000
State \| Research and Development
Income Taxes [Line Items]
Tax credit carryforwards			$ 2,100,000	1,300,000
Tax credit carryforwards expiration year			2035
Foreign
Income Taxes [Line Items]
Operating loss carryforwards			$ 354,800,000	$ 72,900,000

Short-Term Investments - Summary of Amortized Cost and Estimated Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 4,994	$ 93,749	$ 128,036
Unrealized Gains	1	73	4
Unrealized Losses			(337)
Fair Value	4,995	93,822	127,703
U.S. Government Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	4,994	93,749	99,288
Unrealized Gains	1	73	1
Unrealized Losses			(253)
Fair Value	$ 4,995	$ 93,822	99,036
Corporate and Agency Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost			28,748
Unrealized Gains			3
Unrealized Losses			(84)
Fair Value			$ 28,667

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Summary of Income (Loss) Before Provision for Income Taxes

Income (loss) before provision for income taxes consisted of the following:


	Years Ended December 31,
(in thousands)	2023			2022
Federal		(376,152	)		(113,389	)
Foreign		185,608			(55,586	)

Loss before provision for income taxes		$(190,544)		$	(168,975	)

Schedule of Provision for Income Taxes

The provision for income taxes for the years ended December 31, 2023 and 2022 consisted of the following:


	Years Ended December 31,
(in thousands)	2023			2022
Current income tax (benefit) expense:
Federal	$	(136	)		(246	)
State		10			(19	)
Foreign		—			—

Total current income tax benefit		(126)			(265	)

Deferred income tax (benefit) expense:
Federal		—			—
State		—			—
Foreign		—			—

Total deferred income tax benefit		—			—

Total income tax benefit	$	(126	)	$	(265	)

Schedule of Income Tax (Benefit) Expense Reconciliation


	Years Ended December 31,
(in thousands)	2023					2022
Benefit at the federal rate	$	(40,015	)	21.0	%	$	(35,472	)	21.0	%
Increase (decrease) resulting from:
Foreign tax rate differential		(15,783	)	8.3	%		2,177		(1.3	)%
State taxes, net of federal benefit		(9,514	)	5.0	%		(1,603	)	0.9	%
Change in valuation allowance		98,714		(51.8	)%		35,406		(21.0	)%
Intercompany note impairment		(34,615	)	18.2	%		—		—
Tax credits		(5,928	)	3.1	%		(6,992	)	4.1	%
Officer's compensation		177		(0.1	)%		695		(0.4	)%
Stock compensation		4,564		(2.4	)%		4,637		(2.7	)%
Impairment of intellectual property		3,003		(1.6	)%		—		—
Permanent differences		79		0.0	%		(182	)	0.1	%
Change in state tax law		384		(0.2	)%		—		—
Other		(1,192	)	0.6	%		1,069		(0.6	)%

Total income tax benefit	$	(126	)	0.1	%	$	(265	)	0.1	%

Summary of Components of Deferred Income Taxes

Components of deferred income taxes consist of the following:


	December 31,
(in thousands)	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	54,081		$	9,374
Tax credit carryforwards		19,378			12,374
Intangible assets		—			25,537
Intercompany note impairment		64,087
Operating lease liabilities		6,348			8,074
Non-qualified stock compensation		15,435			12,017
Restricted stock compensation		680			235
Capitalization of R&D expenses		20,758			20,375
Other		676			1,661

Total deferred tax assets		181,443			89,647

Valuation allowance		(180,943	)		(82,228	)

Net deferred tax assets	$	500		$	7,419

Deferred tax liabilities:
Operating lease right-of-use assets		(506	)		(7,218	)
Depreciation		4			(186	)
Other		2			(15	)

Total deferred tax liabilities		(500	)		(7,419	)

Net deferred tax asset (liability)	$	—		$	—

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation expenses	$ 0.4	$ 0.7
Impairment loss	$ 0.5
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,947	$ 10,468	$ 15,889	$ 30,785	$ 40,779	$ 41,315
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	312	3,254	232	10,191	13,167	14,014
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,635	$ 7,214	$ 15,657	$ 20,594	$ 27,612	$ 27,301

Property and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

6. Property and Equipment, Net

Property and equipment, net consisted of the following:


	December 31,
(in thousands)	2023			2022
Laboratory equipment	$	1,483		$	1,395
Computer equipment		435			435
Construction-in-progress		—			104

Total property and equipment		1,918			1,934
Less: accumulated depreciation and impairment		(1,918	)		(1,004	)

Property and equipment, net	$	—		$	930

Depreciation expense was $0.4 million and $0.7 million for the years ended December 31, 2023 and 2022, respectively. As a result of the December 2023 announcement of the discontinuation of the Company’s three Phase 3 registrational trials and a comprehensive review of strategic alternatives, an impairment loss of $0.5 million was recognized on

property and equipment

during the year ended December 31, 2023.

Restructuring Costs - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2024
Restructuring and Related Activities [Abstract]
Percentage of workforce reduction	95.00%
Restructuring charges		$ 100	$ 10,059

Stockholder's Equity

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Equity [Abstract]

Stockholder's Equity

7. Stockholder’s Equity

On May 15, 2023, the Company filed a certificate of amendment to its amended and restated certificate of incorporation authorizing the Company to issue up to 300,000,000 shares of common stock at a par value of $0.0001 per share and 10,000,000 shares of preferred stock at a par value of $0.0001 per share. There were no shares of preferred stock issued or outstanding at September 30, 2024 and December 31, 2023.

On June 21, 2023, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC, Morgan Stanley & Co. LLC and BoFA Securities, Inc., as the representatives of the several underwriters (the “Underwriters”) relating to an underwritten public offering of 20,000,000 shares of its common stock at a public offering price of $3.75 per share, resulting in net proceeds of $70.2 million after deducting underwriting discounts and commissions of $4.5 million and offering costs of $0.3 million. Under the terms of the underwriting agreement, the Company granted the Underwriters an option, exercisable for 30 days, to purchase up to an additional 3,000,000 shares of its common stock at the same price per share as the shares, less underwriting discounts and commissions. On July 21, 2023, the Underwriters option expired.

The Company has reserved shares of common stock for issuance as follows:


	September 30,		December 31,
	2024		2023
Options to purchase common stock		6,072,019		10,439,751
Unvested restricted stock		1,120,099		3,254,863
Stock available for grant under the 2020 Stock Option and Grant Plan		15,091,301		4,182,461
Stock available for issuance under the 2020 Employee Stock Purchase Plan		1,585,257		480,059

Total		23,868,676		18,357,134

9. Stockholder’s Equity

On July 26, 2022, the Company entered into the Securities Purchase Agreement with certain investors for aggregate net proceeds of $126.4 million after deducting issuance costs of $0.2 million. Pursuant to the terms of the Securities Purchase Agreement, the Company agreed to issue and sell to the investors in a registered direct offering an aggregate of 27,458,095 shares of the Company’s common stock, par value $0.0001 per share (the “Shares”) at a purchase price of $4.61 per Share (the “Offering”). The Offering was made without an underwriter or a placement agent, and therefore, there were no underwriting discounts or commissions in connection with the offering.

The following is a summary of the rights and privileges of the holders of the Company’s common stock at December 31, 2023 and 2022:

Voting Rights

The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders (and written actions in lieu of meetings), and there are not any cumulative voting rights. The number of authorized shares of common stock may be increased or decreased by the affirmative vote of the holders of shares of capital stock of the Company; however, the issuance of common stock may be subject to the vote of the holders of one or more series of preferred stock that may be required by terms of the Third Amended and Restated Certificate of Incorporation.

Dividends

Subject to preferences that may be applicable to any then-outstanding preferred stock, holders of common stock are entitled to receive ratably those dividends, if any, as may be declared from time to time by the Board out of legally available funds. At December 31, 2023, no cash dividends have been declared or paid.

Liquidation Preference

In the event of a liquidation, dissolution or winding up, holders of common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all debts and other liabilities and the satisfaction of any liquidation preference granted to the then-outstanding shares of preferred stock.

Rights and Preferences

Holders of common stock have no preemptive, conversion or subscription rights and there are no redemption or sinking fund provisions applicable to the common stock. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that the Company may designate in the future.

The Company has reserved shares of common stock for issuance as follows:


	December 31,
	2023		2022
Unvested restricted stock		3,254,863		2,239,106
Options to purchase common stock		10,439,751		7,922,797
Stock available for grant under the 2020 Stock Option and Grant Plan		4,182,461		4,253,680
Stock available for issuance under the 2020 Employee Stock Purchase Plan		480,059		454,302

Total		18,357,134		14,869,885

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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+ Details

Accrued Expenses

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued Expenses

6. Accrued Expenses

Accrued expenses consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Employee compensation and benefits	$	739	$	3,809
Professional fees		547		435
Research and development		—		2,442
Process development and manufacturing costs		—		2,367
Other		75		1,033

Total accrued expenses	$	1,361	$	10,086

Employee compensation and benefits includes $0.1 million of restructuring liability at September 30, 2024 (see Note 13).

7. Accrued Expenses

Accrued expenses consisted of the following:


	December 31,
(in thousands)	2023		2022
Employee compensation and benefits	$	3,809	$	6,416
Professional fees		435		559
Research and development		2,442		5,678
Process development and manufacturing costs		2,367		504
Other		1,033		828

Total accrued expenses	$	10,086	$	13,985

Nature of the Business - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended						9 Months Ended		12 Months Ended
	Jan. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Percentage of workforce reduction	95.00%
Net losses attributable to common stockholders		$ (4,126)	$ (6,076)	$ (30,299)	$ (44,272)	$ (45,267)	$ (41,183)	$ (40,501)	$ (130,722)	$ (190,418)	$ (168,710)
Accumulated deficit		(696,694)						(696,694)		(656,193)	$ (465,775)
Cash, cash equivalents and short-term investments		$ 121,900						$ 121,900		$ 183,900
Subsequent Event
Percentage of workforce reduction	95.00%

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Leases - Summary of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2024	$ 11,842
2025	3,219
2026	3,298
2027	3,376
2028	3,455
Thereafter	5,824
Total lease payments	31,014
Less: interest	3,585
Total lease liability	27,429
Lease liability – current	10,781	$ 7,165
Lease liability – long-term	$ 16,648	$ 28,222

Subsequent Events	9 Months Ended	12 Months Ended
Subsequent Events	Sep. 30, 2024	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events Merger Agreement On November 7, 2024, the Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Kalaris Therapeutics, Inc. (“Kalaris”) and Aurora Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of the Company (“Merger Sub”), pursuant to which, among other matters, and subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, Merger Sub will merge with and into Kalaris (the “Merger”), with Kalaris continuing as a wholly owned subsidiary of the Company and the surviving corporation of the Merger. The Company’s board of directors has unanimously approved the Merger Agreement and, subject to certain exceptions set forth in the Merger Agreement, resolved to recommend that our stockholders adopt the Merger Agreement. Subject to the terms and conditions of the Merger Agreement, at the effective time of the Merger (the “Effective Time”), (a) each share of Kalaris common stock, par value $0.00001 per share (“Kalaris Common Stock”), issued and outstanding (after giving effect to the Kalaris Preferred Stock Conversion (as defined below)) (other than shares of Kalaris Common Stock (or any security convertible into Kalaris Common Stock) (i) held as treasury stock, (ii) owned, directly or indirectly, by the Company or Merger Sub immediately prior to the Effective Time or (iii) as to which appraisal rights have been properly exercised in accordance with Delaware law) will be converted into and become exchangeable for the right to receive a number of shares of the Company’s common stock, par value $0.0001 per share (“Company Common Stock”), based on a ratio calculated in accordance with the Merger Agreement (the “Exchange Ratio”) and (b) all of Kalaris’s preferred stock, par value $0.00001 per share, will be converted into Company Common Stock in accordance with, and pursuant to the terms and conditions of the organizational documents of Kalaris (the “Kalaris Preferred Stock Conversion”). At the Effective Time, subject to the terms and conditions of the Merger Agreement, (a) each award of restricted shares of Kalaris Common Stock that is unvested and outstanding will be converted into and become exchangeable for the right to receive a number of restricted shares of Company Common Stock based on the Exchange Ratio and (b) each outstanding option to purchase shares of Kalaris Common Stock granted by Kalaris under its 2019 Equity Incentive Plan, as amended, will be converted into an option to acquire a number of shares of Company Common Stock based on the Exchange Ratio. Subject to the terms of the Merger Agreement, each unexercised and outstanding Company stock option with an exercise price per share equal to or greater than $4.00 will be cancelled for no consideration and all other unexpired, unexercised and unvested Company stock options will accelerate in full as of immediately prior to the Effective Time. Further, the vesting of each outstanding and unvested Company restricted stock unit will accelerate in full as of immediately prior to the Effective Time and each outstanding and unsettled Company restricted stock unit will be settled in shares of Company Common Stock. Each of the Company and Kalaris has agreed to customary representations, warranties and covenants in the Merger Agreement, including, among others, covenants relating to (1) obtaining the requisite approval of their respective stockholders, (2) non-solicitation of alternative acquisition proposals, (3) the conduct of their respective businesses during the period between the date of signing the Merger Agreement and the closing, (4) the Company maintaining the existing listing of the Company Common Stock on Nasdaq and causing the shares of Company Common Stock to be issued in connection with the Merger to be approved for listing on Nasdaq prior to the closing and (5) the Company filing with the U.S. Securities and Exchange Commission and causing to become effective a registration statement on Form S-4 to register the shares of Company Common Stock to be issued in connection with the Merger. The Merger Agreement contains certain termination rights of each of the Company and Kalaris. Upon termination of the Merger Agreement under specified circumstances, the Company may be required to pay Kalaris a termination fee of $3,480,000, and in certain other circumstances, Kalaris may be required to pay the Company a termination fee of $10,410,000. The completion of the Merger is subject to customary closing conditions, including, among others, the adoption of the Merger Agreement by the Company’s stockholders.	16. Subsequent Events In January 2024, the board of directors approved a reduction in the Company’s workforce by approximately 95% of the Company’s current employee base in order to reduce costs and preserve capital in light of the announcement on December 22, 2023 that the Company is discontinuing its three global Phase 3 posoleucel studies. This workforce reduction will take place primarily during the first quarter of 2024 and expected to be substantially completed by April 15, 2024. As a result of these actions, the Company expects to incur personnel-related restructuring charges, excluding bonuses accrued as of December 31, 2023, of approximately $10 million in connection with one-time employee termination cash expenditures, including severance and other benefits. The Company had previously granted certain of the terminated employees restricted stock units (“RSUs”) that vest in annual installments based on continued service to the Company, as well as options to purchase shares of the Company’s common stock that typically vest over a period of four years. In connection with the reduction in workforce, the Company agreed to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates. In February 2024, the Company entered into a new SOW (“2024 SOW under the DMS Agreement”) that terminated the 2022 SOW under the DMS Agreement with a third-party supplier (see Note 5), resulting in a decrease in lease payments of $5.7 million in 2024. In Q1 2024, the Company paid all remaining lease obligations of $2.9 million.

Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Aug. 31, 2022
Related Party Transaction [Line Items]
Consulting fees to members of management and board of directors	$ 0	$ 100,000	$ 100,000	$ 300,000	$ 400,000	$ 500,000
ElevateBio Technologies, Inc \| Management and Administrative Services Agreement
Related Party Transaction [Line Items]
Lease expiration term			The agreement has an initial term of five years and will automatically renew for successive one year terms, unless earlier terminated under the terms of the agreement.		The agreement has an initial term of five years and will automatically renew for successive one year terms, unless earlier terminated under the terms of the agreement.
BaseCamp
Related Party Transaction [Line Items]
Prepaid expenses							$ 2,000,000
BaseCamp \| DMS Agreement
Related Party Transaction [Line Items]
Lease expiration term			The agreement will expire upon the later of (a) five years from the effective date of January 1, 2019 or (b) the completion of services under all work orders executed prior to the fifth anniversary of the effective date, unless earlier terminated under the terms of the agreement.		The agreement will expire upon the later of (a) five years from the effective date of January 1, 2019 or (b) the completion of services under all work orders executed prior to the fifth anniversary of the effective date, unless earlier terminated under the terms of the agreement.
ElevateBio and Affiliates
Related Party Transaction [Line Items]
Prepaid expenses	0		$ 0		$ 0	2,000,000
Expenses related to services with related party	0	1,000,000	100,000	1,600,000	2,600,000	3,500,000
Sale of equipment	100,000		100,000
Amount due to related party	0		0		300,000	$ 100,000
Marker Therapeutics, Inc.
Related Party Transaction [Line Items]
Amount due to related party	0		0		500,000
Costs incurred under agreement	$ 0	$ 200,000	$ 0	$ 200,000	$ 500,000
Cost of Revenue, Related Party [Extensible Enumeration]	Related Party [Member]	Related Party [Member]	Related Party [Member]	Related Party [Member]	Related Party [Member]

Nature of the Business

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of the Business

1. Nature of the Business

AlloVir, Inc. (“AlloVir” or “the Company”, formerly known as ViraCyte, Inc.) is a cell therapy company developing highly innovative allogeneic T cell therapies to treat and prevent devastating viral diseases. The Company’s innovative and proprietary virus-specific T cell, or VST, therapy platform allows AlloVir to generate

off-the-shelf

VSTs designed to restore immunity in patients with T cell deficiencies who are at risk from the life-threatening consequences of viral diseases. There is an urgent medical need for therapies to treat a large number of patients suffering from viral diseases who currently have limited or no treatment options. The Company’s platform includes three innovative, allogeneic,

off-the-shelf

VST therapy candidates targeting 11 different devastating viruses. The Company’s lead product candidate, posoleucel (previously referred to as

Viralym-M

or ALVR105), is a

multi-VST

therapy that targets six viruses: adenovirus (“AdV”), BK virus (“BKV”), cytomegalovirus (“CMV”), Epstein-Barr virus (“EBV”), human herpesvirus 6

(“HHV-6”)

and JC virus (“JCV”).

In December 2023, the Company announced the discontinuation of three Phase 3 registrational trials of posoleucel following separate,

pre-planned

Data Safety Monitoring Board (“DSMB”), futility analyses that concluded the studies were unlikely to meet their primary endpoints. Specifically, the Company discontinued a multicenter, randomized, double-blind, placebo-controlled Phase 3 trial comparing posoleucel to placebo for the prevention of infection or disease due to AdV, BKV, CMV, EBV,

HHV-6,

or JCV in high-risk adult and pediatric patients after undergoing an allogeneic hematopoietic stem cell transplant. The Company also discontinued two multicenter, randomized, double-blind, placebo-controlled Phase 3 trials of posoleucel – one for the treatment of virus-associated hemorrhagic cystitis and the second for the treatment of adenovirus infection – both after allogeneic he

matopoi

etic cell transplant.

After a comprehensive review of strategic alternatives, on November 7, 2024, the Company entered into an agreement and plan of merger (the “Merger Agreement”) with Kalaris Therapeutics, Inc. (“Kalaris”). Pursuant to the Merger Agreement, and subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, at the effective time of the Merger, Aurora Merger Sub, Inc., a wholly-owned subsidiary of the Company, will merge with and into Kalaris (the “Merger”), with Kalaris continuing as a wholly-owned subsidiary of the Company and the surviving corporation of the Merger.

The Company expects to devote significant time and resources to the completion of the Merger. If the Merger is not completed, the Company will reconsider its strategic alternatives and may pursue one of the following courses of action, which the Company currently believes are the most likely alternatives if the Merger is not completed:

•

Pursue another strategic transaction similar to the Merger

. The Company may resume its process of evaluating other candidate companies

interested in pursuing a strategic transaction and, if a candidate is identified, focus its attention on negotiating and completing such strategic transaction with such candidate.

•

Continue to operate its business

. The Company could elect to continue to operate its business and pursue licensing or partnering transactions.

To continue to operate its business, the Company would

require a significant amount of time and financial resources, and the Company would be subject to all the risks and uncertainties involved in the development of product candidates. There is no assurance that the Company could raise sufficient capital to support these efforts, that its development efforts would be successful or that it could successfully obtain the regulatory approvals required to market any product candidate it pursued.

•

Dissolve and liquidate its assets

. If the Company is unable, or does not believe that it is able, to find a suitable candidate for another strategic

transaction, the Company may dissolve and liquidate its assets. In that event, the Company would be required to pay all of its debts and contractual obligations and to set aside certain reserves for commitments and contingent liabilities. If the Company dissolves and liquidates its assets, there can be no assurance as to the amount or timing of available cash that will remain for distribution to the Company’s stockholders after paying the Company’s debts and other obligations and setting aside funds for commitments and contingent liabilities.

The Company’s pipeline includes additional investigational VST therapies that may benefit high-risk individuals. ALVR106 is the Company’s second

off-the-shelf,

multi-VST

product candidate targeting devastating respiratory diseases caused by human metapneumovirus (“hMPV”), influenza, parainfluenza virus (“PIV”) and respiratory syncytial virus (“RSV”). A Phase 1b/2 proof of concept (“POC”) clinical study of ALVR106 has completed enrollment of patients in Part A of the trial. The Company has paused development of ALVR106, including discontinuing the trial pending the outcome of the Company’s review of strategic alternatives. Preclinical and

IND-enabling

studies of ALVR107 to treat and cure hepatitis B were completed in 2022 to support advancement into a POC study. Clinical development of ALVR107 has been paused pending the outcome of the Company’s review of strategic alternatives.

Going Concern

In accordance with Accounting Standards Update (“ASU”)

2014-15,

Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going

Concern (Subtopic

205-40)

, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt

about the Company’s ability to continue as a going concern within one year after the date the condensed consolidated financial statements are issued.

Since its inception and until recently, the Company devoted substantially all of its resources to recruiting personnel, developing its technology platform and advancing its pipeline of product candidates through discovery, preclinical and clinical trials, acquiring and manufacturing clinical trial materials and maintaining and building its intellectual property portfolio. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, success of clinical trials, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Should the Company resume development of its product candidates, the product candidates will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization.

Through September 30, 2024, the Company has funded its operations primarily with proceeds received from the sale of common stock, research grants, and from the sale of preferred stock. The Company has incurred recurring losses since its inception, including net losses attributable to common stockholders of $40.5 million and $130.7 million for the nine months ended September 30, 2024 and 2023, respectively. In addition, at September 30, 2024, the Company had an accumulated deficit of $696.7 million. The Company expects to continue to generate operating losses for the foreseeable future.

able to successfully consummate any particular strategic transaction. The process of evaluating strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges.

Based on current projections, the Company believes that its $121.9 million of cash, cash equivalents and short-term investments held at September 30, 2024 will be sufficient to fund planned operations for at least twelve months from the date that these condensed consolidated financial statements are available to be issued. However, due to the consideration of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as the Company’s workforce reduction plan, management has concluded there is substantial doubt regarding the Company’s ability to continue as a going concern for more than twelve months from the date that the condensed consolidated financial statements are available to be issued. These financial statements do not include any adjustments that might result from the outcome of this uncertainty. Should the Company resume the development of product candidates, it would need to obtain substantial additional funding in connection with continuing operations, particularly as the Company resumes its preclinical activities and clinical trials for its product candidates. There can be no assurance that the Company will be able to obtain sufficient capital to cover its costs on acceptable terms, if at all.

ElevateBio, LLC – Related Party

On September 17, 2018, the Company executed a Series A2 Preferred Stock Purchase Agreement (“Series A2 Agreement”) with ElevateBio, LLC (“ElevateBio”) and ElevateBio was a purchaser in our registered direct offering in July 2022. ElevateBio, through its diverse platform of technologies to support cell and gene therapy products and expertise, provides drug development and manufacturing services. As a result of ElevateBio’s purchase of our Series A2 Preferred Stock, which converted to common stock upon completion of our IPO, and as a result of ElevateBio’s participation in the July 2022 registered direct offering, ElevateBio acquired an ownership interest in the Company. The Chief Financial Officer of ElevateBio currently serves in a similar management role with AlloVir. In May 2021, Diana M. Brainard, M.D. succeeded David Hallal, ElevateBio’s Chief Executive Officer, as the Company’s Chief Executive Officer. Mr. Hallal currently serves as Executive Chairman of the Company’s board of directors. Vikas Sinha, our President and Chief Financial Officer, also serves as the Chief Financial Officer of ElevateBio. In addition to Mr. Hallal and Mr. Sinha, Morana Jovan-Embiricos, a director of the Company’s board of directors, also serves as a director of the board of directors of ElevateBio.

1. Nature of the Business

off-the-shelf

VST therapy candidates targeting 11 different devastating viruses. The Company’s lead product candidate, posoleucel (previously referred to as

Viralym-M

or ALVR105), is a

multi-VST

therapy that targets six viruses: adenovirus, or AdV, BK virus, or BKV, cytomegalovirus, or CMV, Epstein-Barr virus, or EBV, human herpesvirus 6, or

HHV-6

and JC virus, or JCV.

In December 2023, the Company announced the discontinuation of three Phase 3 registrational trials of posoleucel following separate,

pre-planned

Data Safety Monitoring Board, or DSMB, futility analyses that concluded the studies were unlikely to meet their primary endpoints. Specifically, the Company discontinued a multicenter, randomized, double-blind, placebo-controlled Phase 3 trial comparing posoleucel to placebo for the prevention of infection or disease due to AdV, BKV, CMV, EBV,

HHV-6,

In December 2023, the Company also announced that it would review the detailed datasets from those Phase 3 trials and launch a comprehensive review of strategic alternatives focused on maximizing stockholder value, including, but not limited to, a merger, sale, divestiture of assets, licensing, or other strategic transaction. The Company expects to devote substantial time and resources to exploring strategic alternatives that the board of directors believes will maximize stockholder value. Despite devoting significant efforts to identify and evaluate potential strategic alternatives, there can be no assurance that this strategic review process will result in us pursuing any transaction or that any transaction, if pursued, will be completed on attractive terms or at all. The Company has not set a timetable for completion of this strategic review process, and the board of directors has not approved a definitive course of action. Additionally, there can be no assurances that any particular course of action, business arrangement or transaction, or series of transactions, will be pursued, successfully consummated or lead to increased stockholder value, or that the Company will make any cash distributions to our stockholders. In connection with the evaluation of strategic alternatives and in order maximize capital preservation, the Company has implemented a plan to reduce our workforce by approximately 95%. This workforce reduction plan was approved in January 2024, and will take place primarily during the first quarter of 2024 and is expected to be substantially completed by April 15, 2024.

The Company’s pipeline includes additional investigational VST therapies that may benefit high-risk individuals. ALVR106 is the Company’s second

off-the-shelf,

multi-VST

product candidate targeting devastating respiratory diseases caused by human metapneumovirus, or hMPV, influenza, parainfluenza virus, or PIV and respiratory syncytial virus, or RSV. A Phase 1b/2 POC clinical study of ALVR106 has completed enrollment of patients in Part A of the trial. The Company has paused development of ALVR106, including discontinuing the trial pending the outcome of the Company’s review of strategic alternatives. In the preclinical space, preclinical and

IND-enabling

studies of ALVR107 to treat and cure HBV were completed in 2022 to support advancement into a POC study. Clinical development of ALVR107 has been paused pending the outcome of the Company’s review of strategic alternatives.

Going Concern

In accordance with Accounting Standards Update (“ASU”)

2014-15,

Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going

Concern (Subtopic

205-40)

, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt

about the Company’s ability to continue as a going concern within one year after the date the consolidated financial statements are issued.

Through December 31, 2023, the Company has funded its operations primarily with proceeds received from the sale of common stock, research grants, and from the sale of preferred stock. The Company has incurred recurring losses since its inception, including net losses attributable to common stockholders of $190.4 million for the year ended December 31, 2023 and $168.7 million for the year ended December 31, 2022. In addition, at December 31, 2023, the Company had an accumulated deficit of $656.2 million. The Company expects to continue to generate operating losses for the foreseeable future.

The Company has incurred and expects to continue to incur costs and expenditures in connection with the process of evaluating strategic alternatives. There can be no assurance, however, that the Company will be able to successfully consummate any particular strategic transaction. The process of evaluating strategic options has been and may continue to be costly, time-consuming and complex and the Company may incur significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges.

Based on current projections, the Company believes that its $183.9 million of cash, cash equivalents and short-term investments held at December 31, 2023 will be sufficient to fund planned operations for at least twelve months from the date that these consolidated financial statements are available to be issued. However, due to the consideration of certain qualitative factors, including the discontinuation of all clinical trials and research activities, as well as the Company’s workforce reduction plan, management has concluded there is substantial doubt regarding the Company’s ability to continue as a going concern for more than twelve months from the date that the consolidated financial statements are available to be issued. These consolidated financial statements do not include any adjustments that might result from the outcome of this uncertainty. Should the Company resume the development of product candidates, it would need to obtain substantial additional funding in connection with continuing operations, particularly as the Company resumes its preclinical activities and clinical trials for its product candidates. There can be no assurance that the Company will be able to obtain sufficient capital to cover its costs on acceptable terms, if at all.

ElevateBio, LLC - Related Party

On September 17, 2018, the Company executed a Series A2 Preferred Stock Purchase Agreement (“Series A2 Agreement”), with ElevateBio, LLC (“ElevateBio”) and ElevateBio was a purchaser in our registered direct

offering in July 2022. ElevateBio, through its diverse platform of technologies to support cell and gene therapy products and expertise, provides drug development and manufacturing services. As a result of ElevateBio’s purchase of our Series A2 Preferred Stock, which converted to common stock upon completion of our IPO, and as a result of ElevateBio’s participation in the July 2022 registered direct offering, ElevateBio acquired an ownership interest in the Company. The Chief Financial Officer of ElevateBio currently serves in a similar management role with AlloVir. In May 2021, Diana M. Brainard, M.D. succeeded David Hallal, ElevateBio’s Chief Executive Officer, as the Company’s Chief Executive Officer. Mr. Hallal currently serves as Executive Chairman of the Company’s board of directors. In addition to Mr. Hallal and Mr. Sinha, Morana Jovan-Embiricos, a director of the Company’s board of directors, also serves as a director of the board of directors of ElevateBio.