AlloVir (ALVR) 10-Q 3 Nov 22 2022 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2022	Oct. 28, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Trading Symbol	ALVR
Entity Registrant Name	ALLOVIR, INC.
Entity Central Index Key	0001754068
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		93,162,961
Security12b Title	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39409
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	83-1971007
Entity Address Address Line1	1100 Winter Street
Entity Address City Or Town	Waltham
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02451
City Area Code	617
Local Phone Number	433-2605
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 123,834	$ 201,661
Short-term investments	140,273	46,459
Interest receivable	261	50
Prepaid expenses and other current assets	5,568	5,178
Prepaid expenses to related party	2,106
Total current assets	272,042	253,348
Restricted cash	852	852
Other assets	734	1,102
Property and equipment, net	943	1,549
Operating lease right-of-use assets	19,127	29,743
Total assets	293,698	286,594
Current liabilities:
Accounts payable	4,889	8,361
Accrued expenses	13,677	20,152
Income tax payable	154	1,007
Operating lease liability, current	1,918	6,591
Amount due to related party	81	1,742
Total current liabilities	20,719	37,853
Operating lease liability, long term	19,753	23,475
Total liabilities	40,472	61,328
Stockholders’ equity:
Preferred stock, $0.0001 par value: 10,000,000 shares authorized at September 30, 2022 and December 31, 2021, respectively; 0 shares issued and outstanding at September 30, 2022 and December 31, 2021, respectively
Common stock, $0.0001 par value: 150,000,000 shares authorized at September 30, 2022 and December 31, 2021, respectively; 93,119,302 and 65,170,332 shares issued at September 30, 2022 and December 31, 2021, respectively; and 92,640,109 and 63,565,886 shares outstanding at September 30, 2022 and December 31, 2021, respectively	9	7
Additional paid-in capital	681,419	522,479
Accumulated other comprehensive loss	(563)	(155)
Accumulated deficit	(427,639)	(297,065)
Total stockholders’ equity	253,226	225,266
Total liabilities and stockholders’ equity	$ 293,698	$ 286,594

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par or stated value per share	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	93,119,302	65,170,332
Common stock, shares outstanding	92,640,109	63,565,886

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development	$ 30,004	$ 33,062	$ 90,450	$ 79,132
General and administrative	12,946	12,442	40,318	34,890
Total operating expenses	42,950	45,504	130,768	114,022
Loss from operations	(42,950)	(45,504)	(130,768)	(114,022)
Total other income (loss), net:
Interest income	668	253	978	1,233
Other income, (loss), net	210	(259)	(634)	(1,232)
Loss before income taxes	(42,072)	(45,510)	(130,424)	(114,021)
Income tax expense			150
Net loss	$ (42,072)	$ (45,510)	$ (130,574)	$ (114,021)
Net loss per share - basic	$ (0.50)	$ (0.72)	$ (1.83)	$ (1.82)
Net loss per share - diluted	$ (0.50)	$ (0.72)	$ (1.83)	$ (1.82)
Weighted-average common shares outstanding - basic	84,948,837	62,962,434	71,213,219	62,588,898
Weighted-average common shares outstanding - diluted	84,948,837	62,962,434	71,213,219	62,588,898
Comprehensive loss:
Net loss	$ (42,072)	$ (45,510)	$ (130,574)	$ (114,021)
Other comprehensive income (loss), net of tax:
Unrealized (loss) gain on available-for-sale securities	(119)	(3)	(408)	23
Foreign currency translation adjustment		(105)		(44)
Total other comprehensive loss	(119)	(108)	(408)	(21)
Comprehensive loss	$ (42,191)	$ (45,618)	$ (130,982)	$ (114,042)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Balance at Dec. 31, 2020	$ 353,064	$ 7	$ 478,272	$ (112)	$ (125,103)
Balance, Shares at Dec. 31, 2020		61,931,255
Stock-based compensation	8,103		8,103
Issuance of common stock, upon vesting of restricted stock, Shares		519,839
Unrealized (loss) gain on available-for-sale securities	42			42
Foreign currency translation adjustment	83			83
Net loss	(30,923)				(30,923)
Balance at Mar. 31, 2021	330,369	$ 7	486,375	13	(156,026)
Balance, Shares at Mar. 31, 2021		62,451,094
Balance at Dec. 31, 2020	353,064	$ 7	478,272	(112)	(125,103)
Balance, Shares at Dec. 31, 2020		61,931,255
Unrealized (loss) gain on available-for-sale securities	23
Foreign currency translation adjustment	(44)
Net loss	(114,021)
Balance at Sep. 30, 2021	267,304	$ 7	506,554	(133)	(239,124)
Balance, Shares at Sep. 30, 2021		63,177,928
Balance at Mar. 31, 2021	330,369	$ 7	486,375	13	(156,026)
Balance, Shares at Mar. 31, 2021		62,451,094
Stock-based compensation	9,726		9,726
Issuance of common stock, upon vesting of restricted stock, Shares		340,949
Unrealized (loss) gain on available-for-sale securities	(16)			(16)
Foreign currency translation adjustment	(22)			(22)
Net loss	(37,588)				(37,588)
Balance at Jun. 30, 2021	302,469	$ 7	496,101	(25)	(193,614)
Balance, Shares at Jun. 30, 2021		62,792,043
Stock-based compensation	10,286		10,286
Issuance of common stock, upon vesting of restricted stock, Shares		376,460
Issuance of common stock, upon exercise of stock options	167		167
Issuance of common stock, upon exercise of stock options, Shares		9,425
Unrealized (loss) gain on available-for-sale securities	(3)			(3)
Foreign currency translation adjustment	(105)			(105)
Net loss	(45,510)				(45,510)
Balance at Sep. 30, 2021	267,304	$ 7	506,554	(133)	(239,124)
Balance, Shares at Sep. 30, 2021		63,177,928
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	10,467		10,467
Issuance of common stock, upon vesting of restricted stock, Shares		698,241
Unrealized (loss) gain on available-for-sale securities	(195)			(195)
Net loss	(43,863)				(43,863)
Balance at Mar. 31, 2022	191,675	$ 7	532,946	(350)	(340,928)
Balance, Shares at Mar. 31, 2022		64,264,127
Balance at Dec. 31, 2021	225,266	$ 7	522,479	(155)	(297,065)
Balance, Shares at Dec. 31, 2021		63,565,886
Unrealized (loss) gain on available-for-sale securities	(408)
Net loss	(130,574)
Balance at Sep. 30, 2022	253,226	$ 9	681,419	(563)	(427,639)
Balance, Shares at Sep. 30, 2022		92,640,109
Balance at Mar. 31, 2022	191,675	$ 7	532,946	(350)	(340,928)
Balance, Shares at Mar. 31, 2022		64,264,127
Stock-based compensation	10,951		10,951
Issuance of common stock, upon vesting of restricted stock, Shares		450,619
Purchase of common stock under the 2020 employee stock purchase plan	244		244
Purchase of common stock under the 2020 employee stock purchase plan, Shares		73,357
Unrealized (loss) gain on available-for-sale securities	(94)			(94)
Net loss	(44,639)				(44,639)
Balance at Jun. 30, 2022	158,137	$ 7	544,141	(444)	(385,567)
Balance, Shares at Jun. 30, 2022		64,788,103
Stock-based compensation	10,855		10,855
Issuance of common stock, upon vesting of restricted stock, Shares		393,911
Issuance of common stock in registered direct offering, net of issuance costs	126,425	$ 2	126,423
Issuance of common stock in registered direct offering, net of issuance costs, Shares		27,458,095
Unrealized (loss) gain on available-for-sale securities	(119)			(119)
Net loss	(42,072)				(42,072)
Balance at Sep. 30, 2022	$ 253,226	$ 9	$ 681,419	$ (563)	$ (427,639)
Balance, Shares at Sep. 30, 2022		92,640,109

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) (Parenthetical) $ in Millions	3 Months Ended
	Sep. 30, 2022 USD ($)
Issuance costs	$ 0.2

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities
Net loss	$ (130,574)	$ (114,021)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	637	95
Non-cash lease expense	834	468
Accretion (amortization) of short-term investment premiums (discounts)	(206)	1,130
Stock compensation expense	32,273	28,115
Changes in operating assets and liabilities:
Interest receivable	(211)	299
Prepaid expenses and other current assets and prepaid expenses to related party	(1,862)	(1,943)
Other assets	367	(1,206)
Income tax payable	(853)
Accounts payable, accrued expenses and amount due to related party	(10,886)	8,812
Net cash used in operating activities	(110,481)	(78,251)
Cash flows from investing activities
Purchase of property and equipment		(396)
Purchase of short-term investments	(191,340)	(30,098)
Maturities of short-term investments	97,325	230,000
Net cash (used in) provided by investing activities	(94,015)	199,506
Cash flows from financing activities
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	244
Proceeds from exercise of stock options		167
Net cash provided by financing activities	126,669	167
Effect of exchange rate changes on cash, cash equivalents, and restricted cash		(44)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(77,827)	121,378
Cash, cash equivalents, and restricted cash at beginning of period	202,513	122,661
Cash, cash equivalents, and restricted cash at end of period	124,686	244,039
Non-cash investing and financing activities
Unrealized (loss) gain on available-for-sale securities	(408)	23
Right-of-use assets obtained in exchange for operating lease liability		26,386
Reduction of right-of-use asset due to modification	(5,506)
Purchase of property and equipment included in accounts payable and accrued expenses	32
Supplemental disclosure of cash flows
Cash paid for income taxes	1,003
Cash and cash equivalents	123,834	243,187
Restricted cash	852	852
Total cash, cash equivalents, and restricted cash	$ 124,686	$ 244,039

Nature of the Business

Nature of the Business	9 Months Ended
	Sep. 30, 2022
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 leading late clinical-stage 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 is developing four innovative, allogeneic, off-the-shelf VST therapy candidates targeting 12 different devastating viruses. The Company's lead product, 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. The Company believes that posoleucel has the potential to fundamentally transform the treatment landscape for transplant patients by substantially reducing or preventing disease morbidity and mortality, thereby dramatically improving patient outcomes. To fully explore the clinical benefit of posoleucel, the Company is conducting three Phase 3 pivotal and two Phase 2 proof-of-concept (“POC”) trials in 2022 for the treatment and prevention of life-threatening viral diseases in pediatric and/or adult allogeneic hematopoietic cell transplant, or HCT, patients, each representing a potential meaningful commercial opportunity. The three ongoing pivotal trials evaluate the efficacy and safety of posoleucel for the treatment of virus-associated hemorrhagic cystitis, or HC, for the treatment of AdV infections and for the prevention of infections and disease caused by posoleucel’s six target viruses, respectively. A Phase 2 clinical trial for multi-virus prevention in HCT has completed enrollment and final data is expected by year-end. A second Phase 2 trial evaluating posoleucel for BKV treatment in kidney transplant patients has completed enrollment and final data is expected in the first quarter of 2023. The BKV trial is the first posoleucel study in solid organ transplant patients. 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 initiated at the end of 2021. In the preclinical space, the Company is advancing ALVR107 designed to target hepatitis B, or HBV, infected cells and with the aim of curing chronic HBV infection. Preclinical and IND-enabling studies of ALVR107 to treat and cure HBV are expected to be completed in 2022 to support advancement into a POC study. ALVR109 is an allogeneic, off-the-shelf, single virus-targeted cell therapy designed to target SARS-CoV-2, the virus that causes the severe and life-threatening viral disease, COVID-19. Data from the POC clinical trial of ALVR109 were reported in 2021, and the Company continues to make ALVR109 available to physicians in response to appropriate compassionate use requests. The Company was formed on August 16, 2013 as a Delaware limited liability company (“LLC”) , under the name AdCyte LLC and on July 29, 2014 the Company changed its name to ViraCyte LLC. On September 17, 2018, the Company converted from a Delaware LLC to a Delaware corporation (“LLC Conversion”) and changed its name to ViraCyte, Inc. On May 22, 2019, the Company changed its name to AlloVir, Inc. The Company has principal offices in Waltham, Massachusetts and Houston, Texas. On August 8, 2019, AlloVir formed AlloVir International Designated Activity Company (“AlloVir International”), a wholly-owned subsidiary established in Ireland. On October 9, 2019, AlloVir Securities Corporation was incorporated as a Massachusetts Security Corporation, a wholly-owned subsidiary of AlloVir. On November 10, 2019, AlloVir International formed AlloVir Italia S.R.L., a wholly-owned subsidiary in Italy. On July 20, 2021, AlloVir Inc. formed AlloVir U.S., Inc., a wholly-owned subsidiary of AlloVir. On August 3, 2020, the Company completed an initial public offering (“IPO”) in which the Company issued and sold 18,687,500 shares of its common stock, at a public offering price of $ 17.00 per share, resulting in gross proceeds of $ 317.7 million. The Company received $ 292.0 million in net proceeds after deducting underwriting discounts and commissions and offering costs. Upon the closing of the IPO, all of the then-outstanding shares of convertible preferred stock automatically converted into 39,859,139 shares of common stock at the applicable conversion ratio then in effect. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. On July 26, 2022, the Company entered into a Securities Purchase Agreement (the "Securities Purchase Agreement") with certain investors for the issuance and sale of 27,458,095 shares of its common stock for aggregate net proceeds of $ 126.4 million. ElevateBio, LLC On September 17, 2018, the Company executed a Series A2 Preferred Stock Purchase Agreement (“Series A2 Agreement”) with ElevateBio, LLC, a Delaware LLC (“ElevateBio”) concurrent with the LLC Conversion. ElevateBio was formed on November 29, 2017 and is headquartered in Waltham, Massachusetts with a focus on the development of a portfolio of novel cell therapy programs acquired through business development activities with biotechnology companies. ElevateBio is structured as a holding company, comprised of asset-specific subsidiaries focused on the development of pipeline assets, as well as a manufacturing subsidiary with the expertise to provide drug development and manufacturing services. As a result of the purchase of the Company’s Series A2 Preferred Stock, ElevateBio acquired an ownership interest in the Company. The Chief Executive Officer, Chief Financial Officer, and other executives of ElevateBio have previously or currently serve in similar management roles 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 and principal executive officer. 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. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, 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. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. Through September 30, 2022, 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 $ 42.1 million and $ 45.5 million for the three months ended September 30, 2022 and 2021, respectively, and $ 130.6 million and $ 114.0 million for the nine months ended September 30, 2022 and 2021, respectively. In addition, at September 30, 2022, the Company had an accumulated deficit of $ 427.6 million. The Company expects to continue to generate operating losses for the foreseeable future. The Company believes that its $ 264.1 million of cash, cash equivalents and short-term investments held at September 30, 2022 is sufficient to fund planned operations for at least twelve months from the date that these condensed consolidated financial statements are available to be issued. COVID-19 Considerations The development of product candidates could be disrupted and materially adversely affected in the future by a pandemic, epidemic or outbreak of an infectious disease, such as the recent COVID-19 pandemic. The spread of COVID-19 has impacted the global economy and has impacted the Company’s operations, including the interruption of preclinical and clinical trial activities and potential interruption to the Company’s supply chain. For example, the COVID-19 pandemic has delayed clinical trials. If the disruption due to the COVID-19 pandemic continues, planned pivotal clinical trials also could be delayed due to government orders and site policies on account of the pandemic, and some patients may be unwilling or unable to travel to study sites, enroll in trials or be unable to comply with clinical trial protocols if quarantines impede patient movement or interrupt healthcare services, which would delay the Company’s ability to conduct preclinical studies and clinical trials or release clinical trial results and could delay the Company’s ability to obtain regulatory approval and commercialize product candidates. Furthermore, COVID-19 could affect the Company’s employees or the employees of research sites and service providers on whom the Company relies on as well as those of companies with which the Company does business, including suppliers and contract manufacturing organizations (“CMOs”), thereby disrupting business operations. Quarantines and travel restrictions imposed by governments in the jurisdictions in which the Company and the companies with which it does business operate could materially impact the ability of employees to access preclinical and clinical sites, laboratories, manufacturing sites and offices. For the health and safety of our employees, the Company has implemented work-at-home policies and we have generally restricted on site staff to only those employees who are fully vaccinated or essential to the development and research of product candidates; accordingly, the Company may experience limitations in employee resources. The outbreak and any other preventative or protective actions that the Company, its suppliers or other third parties with which it has business relationships, or governments may take in respect of the COVID-19 pandemic, could disrupt, delay or otherwise adversely impact the business. The Company is still assessing business plans and the impact the COVID-19 pandemic may have on its ability to advance the testing, development and manufacturing of drug candidates, including as a result of adverse impacts on the research sites, service providers, vendors, or suppliers on whom the Company relies on, or to raise financing to support the development of our drug candidates. No assurances can be given that this analysis will enable the Company to avoid part or all of any impact from the spread of COVID-19 or its consequences, including downturns in business sentiment generally or this sector in particular. The Company cannot presently predict the scope and severity of any potential business shutdowns or disruptions, but if the Company or any of the third parties on whom it relies on or with whom it conducts business, were to experience shutdowns or other business disruptions, the Company’s ability to conduct business in the manner and on the timelines presently planned could be materially and adversely impacted.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Interim Financial Information The accompanying condensed consolidated balance sheet at September 30, 2022, 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, 2022 and 2021 and condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 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, 2022 and the results of its operations for the three and nine months ended September 30, 2022 and 2021 and its cash flows for the nine months ended September 30, 2022 and 2021. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2022 and 2021 are also unaudited. The results for the three and nine months ended September 30, 2022 are not necessarily indicative of results to be expected for the year ending December 31, 2022 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 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, 2021 , 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 June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 significantly changes the impairment model for most financial assets and certain other instruments. ASU 2016-13 will require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, which will generally result in earlier recognition of allowances for credit losses on loans and other financial instruments. ASU 2016-13 is effective for the Company’s fiscal year beginning after December 15, 2022 and subsequent interim periods. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

Short-Term Investments

Short-Term Investments	9 Months Ended
	Sep. 30, 2022
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 were included in short-term investments on the condensed consolidated balance sheets: September 30, 2022 (in thousands) Amortized Unrealized Unrealized Fair U.S. government treasury securities $ 120,738 $ 2 $ ( 366 ) $ 120,374 Marketable securities: Corporate and agency bonds 19,963 3 ( 67 ) 19,899 Totals $ 140,701 $ 5 $ ( 433 ) $ 140,273 December 31, 2021 (in thousands) Amortized Unrealized Unrealized Fair U.S. government treasury securities $ 25,092 $ — $ ( 20 ) $ 25,072 Marketable securities: Commercial paper 11,568 1 — 11,569 Corporate and agency bonds 9,821 — ( 3 ) 9,818 Totals $ 46,481 $ 1 $ ( 23 ) $ 46,459 Certain short-term debt securities with original maturities of less than three months are included in cash and cash equivalents on the condensed consolidated balance sheets and are not included in the tables above. At September 30, 2022 and December 31, 2021 , all investments had contractual maturities within one year.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2022
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, 2022 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market fund $ 78,255 $ 78,255 Totals $ 78,255 $ — $ — $ 78,255 Short-term investments: U.S. government treasury securities $ 120,374 $ — $ — $ 120,374 Marketable securities: Corporate and agency bonds — 19,899 — 19,899 Totals $ 120,374 $ 19,899 $ — $ 140,273 December 31, 2021 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market fund $ 141,378 $ — $ — $ 141,378 Marketable securities: Commercial paper — 7,998 — 7,998 Corporate and agency bonds — 753 — 753 Totals $ 141,378 $ 8,751 $ — $ 150,129 Short-term investments: U.S. government treasury securities $ 25,072 $ — $ — $ 25,072 Marketable securities: Commercial paper — 11,569 $ — 11,569 Corporate and agency bonds — 9,818 — 9,818 Totals $ 25,072 $ 21,387 $ — $ 46,459 During the nine months ended September 30, 2022 and the year ended December 31, 2021, 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 (corporate and agency bonds and commercial paper) 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. The carrying amounts of prepaid expenses and other current assets, 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.

Leases

Leases	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Leases	5. Leases Operating leases Operating lease liabilities and their corresponding right-of-use (“ROU”) assets are recorded based on the present value of future lease payments over the expected remaining lease term. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term. The Company uses an incremental borrowing rate based on information available at the commencement date in determining the present value of lease payments. The incremental borrowing rate represents the rate of interest that a lessee would have to pay to borrow on a collateralized basis over a similar term at an amount equal to the lease payments in a similar economic environment. The Company estimates this rate based on prevailing market conditions, comparable company and credit analysis, the impact of collateralization, and the term of each of the Company’s lease agreements. In March 2019, the Company entered into an interim services agreement which ultimately led to the DMS Agreement with a third-party supplier in July 2019. The DMS Agreement specifies a dedicated manufacturing suite for the manufacture of AlloVir’s products at the facility. The DMS Agreement will expire upon the later of: 1) two years from the Effective Date, or July 2021 , and 2) the completion of services under all statements of work, (“SOWs”). The term may be extended by agreement of the parties for additional two-year periods upon written notice to the supplier at least 30 days prior to expiration of the then-current term. The DMS Agreement (or any individual SOW) may be terminated earlier by AlloVir at any time by providing 190 days’ notice. The total estimated lease term of approximately 4.25 years expires in July 2023 . In March 2019, at the inception of this lease, the Company recorded a ROU asset and lease liability of $ 6.9 million. In September 2019, the Company executed a SOW for another dedicated manufacturing suite under the DMS Agreement with substantially the same terms as the original SOW. In September 2019, at the inception of this lease, the Company recorded a ROU asset and lease liability of $ 6.3 million. The SOW calls for a fixed monthly payment through July 2023 , with additional two-year renewal options. The total estimated lease term of approximately 3.75 years expires in July 2023 . The use of these manufacturing suites qualifies as a lease under ASC 842, as it includes an identified asset for exclusive use by the Company at its direction. In February 2022, the Company entered into amendments to both SOWs under the DMS Agreement. The original SOW (beginning March 2019) was modified to add a new termination clause whereby the Company can terminate the lease upon entering into a contract for another suite at the facility. Management concluded that the SOW amendment constituted a lease modification under ASC 842 and recorded a $ 1.4 million reduction to the related ROU asset and lease liability in February 2022. On September 30, 2022, the lease ended for accounting purposes and the ROU asset and lease liability was fully amortized. The existing lease will be amortized on a monthly basis until the new lease is executed. The second SOW under the DMS agreement (beginning September 2019) was terminated as of the effective date in February 2022 . As a result of the amendment, which also represented a lease modification under ASC 842, the Company recorded a $ 2.6 million reduction to the related ROU asset and lease liability. In May 2020, the Company entered into a new Development and Manufacturing Services Agreement (“2020 DMS Agreement”) with ElevateBio BaseCamp, Inc. ("BaseCamp") and signed a SOW in November 2020. The 2020 DMS Agreement and related SOW 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, and other related fixed costs, totaling $ 3.2 million over the two-year lease term ( one year lease with a one-year renewal option), that covers costs associated with reserving capacity for AlloVir, as well as cleaning services, utilities, handling and maintenance of the manufacturing suite. At inception of the lease, the Company estimated that the exercise of the one-year renewal option was reasonably certain to occur, and the Company was reasonably certain that it would not exercise its early termination right, providing for a total estimated lease term of two years expiring in January 2023 . As part of the arrangement, there were also variable costs for materials, non-fixed batch payments, storage, knowledge and tech transfer and other common area maintenance fees that were not included in the measurement of the lease. The lease of the facility was determined to be classified as an operating lease and commenced in February 2021, the point at which the new facility area was substantially complete and available for use by the Company. Accordingly, at inception, the Company recorded a ROU asset of $ 3.1 million and a lease liability of $ 2.5 million. The Company prepaid $ 0.6 million of the suite utilization fee, which was reclassified from prepaid expense to the ROU asset upon lease commencement . In February 2022, the Company decided not to exercise the one-year renewal option and subsequently executed a Change Order to modify the terms of the SOW under the 2020 DMS Agreement. Management concluded that the amendments laid out in the change order collectively constituted a lease modification under ASC 842 and recorded a $ 1.3 million reduction to the related lease liability and a $ 1.5 million reduction to the related ROU asset. In September 2021, the Company entered into a new 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 have been classified as operating leases and commenced in September 2021 . At the inception date, the Company has recorded an 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. The agreement also provides a $ 3.1 million tenant improvement allowance which is to be reimbursed by the landlord over the duration of the first two years of the Waltham leases. At September 30, 2022 , $ 0.7 million of the tenant improvement allowance has been used. 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. At September 30, 2022 , the Company has no reasonable certainty that this option to extend will be exercised. Maturities of operating lease liabilities at September 30, 2022 are as follows (in thousands): 2022 (remaining 3 months) $ 689 2023 3,049 2024 3,151 2025 3,229 2026 3,308 Thereafter 13,068 Total lease payments 26,494 Less: interest 4,823 Total lease liability $ 21,671 Lease liability – current $ 1,918 Lease liability – long-term $ 19,753 Total lease costs were $ 1.2 million and $ 2.0 million for the three months ended September 30, 2022 and 2021 , respectively, and $ 4.1 million and $ 4.4 million for the nine months ended September 30, 2022 and 2021 , respectively. Cash paid for operating leases was $ 1.1 million and $ 1.3 million for the three months ended September 30, 2022 and 2021 , respectively, and $ 3.2 million an d $ 3.6 million for the nine months ended September 30, 2022 and 2021 , respectively. The Company’s total variable lease costs, such as materials, batch payments, storage, knowledge and tech transfer, and other common area maintenance fees, related to the operating leases was $ 1.5 million and $ 5.3 million for the three months ended September 30, 2022 and 2021 , respectively, and $ 3.6 million and $ 9.1 million for the nine months ended September 30, 2022 and 2021 , respectively. The weighted average remaining lease term is 7.83 years at September 30, 2022 . The weighted average discount rate is 5.00 % at September 30, 2022 .

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2022
Payables and Accruals [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consisted of the following: (in thousands) September 30, December 31, Employee compensation and benefits $ 5,652 $ 6,867 Professional fees 746 738 Research and development 5,270 3,573 Process development and manufacturing costs 1,282 7,685 Other 727 1,289 Total accrued expenses $ 13,677 $ 20,152

Stockholder's Equity

Stockholder's Equity	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Stockholder's Equity	7. Stockholder’s Equity On August 3, 2020, in connection with the closing of the Company’s IPO, the Company filed its amended and restated certificate of incorporation, which authorizes the Company to issue up to 10,000,000 shares of preferred stock, $ 0.0001 par value per share. There were no shares of preferred stock issued or outstanding at September 30, 2022 and December 31, 2021. At September 30, 2022 and December 31, 2021 , the Company’s amended and restated certificate of incorporation authorized the Company to issue 150,000,000 shares of common stock at a par value of $ 0.0001 per share. 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 Company has reserved shares of common stock for issuance as follows: September 30, December 31, Options to purchase common stock 8,499,509 6,155,055 Unvested restricted stock 2,746,971 2,866,909 Stock available for grant under the 2020 Stock Option and Grant Plan 3,550,703 3,812,396 Stock available for issuance under the 2020 Employee Stock Purchase Plan 537,997 611,354 Total 15,335,180 13,445,714

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2022
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 Nine Months Ended (in thousands) 2022 2021 2022 2021 Research and development $ 3,890 $ 4,010 $ 11,122 $ 11,274 General and administrative 6,965 6,276 21,151 16,841 Total stock-based compensation expense $ 10,855 $ 10,286 $ 32,273 $ 28,115 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 September 30, 2022 , the Company had granted 6,715,415 shares of common stock under the 2018 Plan. At September 30, 2022 , 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. Accordingly, on January 1, 2022, 3,528,817 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 September 30, 2022 , there was an aggregate of 8,435,467 shares of common stock issuable upon the exercise of outstanding options under the 2020 Plan and 3,003,241 shares of restricted common stock granted under the 2020 Plan. There is an aggregate of 3,550,703 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, 2022: Shares Weighted Unvested at January 1, 2022 2,866,909 $ 15.45 Granted 1,559,721 7.70 Forfeited ( 136,888 ) 20.67 Vested ( 1,542,771 ) 11.03 Unvested at September 30, 2022 2,746,971 $ 13.27 At September 30, 2022 , there was $ 33.2 million of unrecognized stock-based compensation cost related to the restricted stock, which is expected to be recognized over a weighted average period of 2.71 years. Stock Options The following table summarizes stock option activity (in thousands, except share and per share data): Shares Weighted Weighted Aggregate Options outstanding at January 1, 2022 6,155,055 $ 23.42 8.80 $ 480 Granted 2,974,481 7.49 — — Exercised — — — — Forfeited ( 630,027 ) 23.34 — — Options outstanding at September 30, 2022 8,499,509 $ 17.85 8.56 $ 3,677 Options vested and exercisable at September 30, 2022 2,636,881 $ 21.99 8.05 $ 189 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. The weighted-average grant date fair value of stock options granted during the nine months ended September 30, 2022 was $ 5.62 . At September 30, 2022 , there was $ 63.9 million of unrecognized stock-based compensation expense related to unvested stock options, which is being recognized over a period of 2.38 years. The fair value was estimated on the date of grant using the Black-Scholes option-pricing model, with the following weighted-average assumptions: Three Months Ended Nine Months Ended Expected term (in years) 6.11 6.07 Expected volatility 90.78 % 90.35 % Risk-free interest rate 2.89 % 2.16 % Expected dividend yield — — Fair value of common stock $ 4.19 $ 7.49 2020 Employee Stock Purchase Plan In July 2020, the 2020 Employee Stock Purchase Plan (the “ESPP”) was adopted by the Board of Directors and approved by the stockholders. The purpose of the 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. The Board of Directors elected not to increase the number of available shares as of January 1, 2021 and 2022. At September 30, 2022 , there was an aggregate of 537,997 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. The first ESPP offering period was shortened in duration to three months and commenced on April 1, 2022 and ended on June 30, 2022. New six-month offering periods will commence each January 1 and July 1 thereafter 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 did no t issue common shares under the ESPP during the three months ended September 30, 2022 . The Company recognized $ 0.1 million of compensation expense for the ESPP during the three months ended September 30, 2022. The Company issued 73,357 common shares under the ESPP during the nine months ended September 30, 2022 , at an average price per share of $ 3.32 . Cash received from purchases under the ESPP for the nine months ended September 30, 2022 was $ 0.2 million. The Company recognized $ 0.2 million of compensation expense for the ESPP during the nine months ended September 30, 2022 .

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2022
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, 2022 and 2021 , the Company did no t record a current and deferred income tax expense. For the nine months ended September 30, 2022 and 2021 , the Company recorded a current and deferred income tax expense of $ 0.2 million and $ 0 , respectively. 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 not recognized deferred tax assets.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2022
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 Nine Months Ended (in thousands, except share and per share data) 2022 2021 2022 2021 Numerator: Net loss – basic and diluted $ ( 42,072 ) $ ( 45,510 ) $ ( 130,574 ) $ ( 114,021 ) Denominator: Weighted-average common shares outstanding – basic and diluted 84,948,837 62,962,434 71,213,219 62,588,898 Net loss per share – basic and diluted $ ( 0.50 ) $ ( 0.72 ) $ ( 1.83 ) $ ( 1.82 ) Based on the amounts outstanding at September 30, 2022 and 2021, 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, 2022 and 2021, 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, 2022 2021 Options to purchase common stock 8,499,509 6,028,476 Unvested restricted stock 2,746,971 3,126,635

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2022
Related Party Transactions [Abstract]
Related Party Transactions	11. 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. In May 2020, the Company entered into the 2020 DMS Agreement with 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 - Leases"). In August 2022, the Company made a $ 2 million prepayment to BaseCamp for future services. The Company incurred $ 0.6 million and $ 0.6 million during the three months ended September 30, 2022 and 2021 , respectively, and $ 2.7 million and $ 4.1 million duri ng the nine months ended September 30, 2022 and 2021, respectively, related to services provided to the Company by ElevateBio and affiliates. At September 30, 2022 and December 31, 2021 , the Company owed ElevateBio and affiliates $ 0.1 million and $ 1.7 million, respectively and had prepaid expenses with ElevateBio and affiliates of $ 2.1 million and $ 0 , respectively. Members of the Company’s management and board of directors received consulting fees totaling $ 0.1 million and $ 0.1 million during the three months ended September 30, 2022 and 2021 , respectively, and $ 0.4 million and $ 0.3 million during the nine months ended September 30, 2022 and 2021 , respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Interim Financial Information	Interim Financial Information The accompanying condensed consolidated balance sheet at September 30, 2022, 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, 2022 and 2021 and condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 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, 2022 and the results of its operations for the three and nine months ended September 30, 2022 and 2021 and its cash flows for the nine months ended September 30, 2022 and 2021. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2022 and 2021 are also unaudited. The results for the three and nine months ended September 30, 2022 are not necessarily indicative of results to be expected for the year ending December 31, 2022 or for any other subsequent interim period.
Recent Accounting Pronouncements	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. Since December 31, 2021 , 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	Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 significantly changes the impairment model for most financial assets and certain other instruments. ASU 2016-13 will require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, which will generally result in earlier recognition of allowances for credit losses on loans and other financial instruments. ASU 2016-13 is effective for the Company’s fiscal year beginning after December 15, 2022 and subsequent interim periods. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

Short-Term Investments (Tables)

Short-Term Investments (Tables)	9 Months Ended
	Sep. 30, 2022
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 were included in short-term investments on the condensed consolidated balance sheets: September 30, 2022 (in thousands) Amortized Unrealized Unrealized Fair U.S. government treasury securities $ 120,738 $ 2 $ ( 366 ) $ 120,374 Marketable securities: Corporate and agency bonds 19,963 3 ( 67 ) 19,899 Totals $ 140,701 $ 5 $ ( 433 ) $ 140,273 December 31, 2021 (in thousands) Amortized Unrealized Unrealized Fair U.S. government treasury securities $ 25,092 $ — $ ( 20 ) $ 25,072 Marketable securities: Commercial paper 11,568 1 — 11,569 Corporate and agency bonds 9,821 — ( 3 ) 9,818 Totals $ 46,481 $ 1 $ ( 23 ) $ 46,459

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2022
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, 2022 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market fund $ 78,255 $ 78,255 Totals $ 78,255 $ — $ — $ 78,255 Short-term investments: U.S. government treasury securities $ 120,374 $ — $ — $ 120,374 Marketable securities: Corporate and agency bonds — 19,899 — 19,899 Totals $ 120,374 $ 19,899 $ — $ 140,273 December 31, 2021 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market fund $ 141,378 $ — $ — $ 141,378 Marketable securities: Commercial paper — 7,998 — 7,998 Corporate and agency bonds — 753 — 753 Totals $ 141,378 $ 8,751 $ — $ 150,129 Short-term investments: U.S. government treasury securities $ 25,072 $ — $ — $ 25,072 Marketable securities: Commercial paper — 11,569 $ — 11,569 Corporate and agency bonds — 9,818 — 9,818 Totals $ 25,072 $ 21,387 $ — $ 46,459

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Summary of Maturities Operating Leases Liabilities	Maturities of operating lease liabilities at September 30, 2022 are as follows (in thousands): 2022 (remaining 3 months) $ 689 2023 3,049 2024 3,151 2025 3,229 2026 3,308 Thereafter 13,068 Total lease payments 26,494 Less: interest 4,823 Total lease liability $ 21,671 Lease liability – current $ 1,918 Lease liability – long-term $ 19,753

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2022
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following: (in thousands) September 30, December 31, Employee compensation and benefits $ 5,652 $ 6,867 Professional fees 746 738 Research and development 5,270 3,573 Process development and manufacturing costs 1,282 7,685 Other 727 1,289 Total accrued expenses $ 13,677 $ 20,152

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	9 Months Ended
	Sep. 30, 2022
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, Options to purchase common stock 8,499,509 6,155,055 Unvested restricted stock 2,746,971 2,866,909 Stock available for grant under the 2020 Stock Option and Grant Plan 3,550,703 3,812,396 Stock available for issuance under the 2020 Employee Stock Purchase Plan 537,997 611,354 Total 15,335,180 13,445,714

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Schedule of Stock-based Compensation Expense	Stock-based compensation expense was as follows: Three Months Ended Nine Months Ended (in thousands) 2022 2021 2022 2021 Research and development $ 3,890 $ 4,010 $ 11,122 $ 11,274 General and administrative 6,965 6,276 21,151 16,841 Total stock-based compensation expense $ 10,855 $ 10,286 $ 32,273 $ 28,115
Summary of Restricted Common Stock Activity	The following table summarizes restricted common stock activity for the nine months ended September 30, 2022: Shares Weighted Unvested at January 1, 2022 2,866,909 $ 15.45 Granted 1,559,721 7.70 Forfeited ( 136,888 ) 20.67 Vested ( 1,542,771 ) 11.03 Unvested at September 30, 2022 2,746,971 $ 13.27
Summary of Stock Option Activity	The following table summarizes stock option activity (in thousands, except share and per share data): Shares Weighted Weighted Aggregate Options outstanding at January 1, 2022 6,155,055 $ 23.42 8.80 $ 480 Granted 2,974,481 7.49 — — Exercised — — — — Forfeited ( 630,027 ) 23.34 — — Options outstanding at September 30, 2022 8,499,509 $ 17.85 8.56 $ 3,677 Options vested and exercisable at September 30, 2022 2,636,881 $ 21.99 8.05 $ 189
Schedule of Estimated Fair Value 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: Three Months Ended Nine Months Ended Expected term (in years) 6.11 6.07 Expected volatility 90.78 % 90.35 % Risk-free interest rate 2.89 % 2.16 % Expected dividend yield — — Fair value of common stock $ 4.19 $ 7.49

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2022
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 Nine Months Ended (in thousands, except share and per share data) 2022 2021 2022 2021 Numerator: Net loss – basic and diluted $ ( 42,072 ) $ ( 45,510 ) $ ( 130,574 ) $ ( 114,021 ) Denominator: Weighted-average common shares outstanding – basic and diluted 84,948,837 62,962,434 71,213,219 62,588,898 Net loss per share – basic and diluted $ ( 0.50 ) $ ( 0.72 ) $ ( 1.83 ) $ ( 1.82 )
Potential Dilutive Securities Excluded From Computation Of Diluted Net Loss Per Share Attributable To Common Stockholders	Based on the amounts outstanding at September 30, 2022 and 2021, 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, 2022 and 2021, 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, 2022 2021 Options to purchase common stock 8,499,509 6,028,476 Unvested restricted stock 2,746,971 3,126,635

Nature of the Business - Additi

Nature of the Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended						9 Months Ended
	Jul. 26, 2022	Aug. 03, 2020	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Aug. 04, 2020
Net proceeds from issuance initial public offering		$ 292,000
Net losses attributable to common stockholders			$ (42,072)	$ (44,639)	$ (43,863)	$ (45,510)	$ (37,588)	$ (30,923)	$ (130,574)	$ (114,021)
Accumulated deficit			(427,639)						(427,639)		$ (297,065)
Cash, cash equivalents and short-term investments			$ 264,100						$ 264,100
Convertible Preferred Stock
Preferred stock, shares outstanding												0
Common Stock
Common stock issued and sold			27,458,095
IPO
Common stock issued and sold		18,687,500
Public offering price per share		$ 17
Gross proceeds from issuance of common stock		$ 317,700
IPO | Common Stock
Stock issued upon conversion of preferred stock		39,859,139
Securities Purchase Agreement
Public offering price per share	$ 4.61
Share issued to investors	27,458,095
Net proceeds with certain investors	$ 126,400

Short-Term Investments - Summar

Short-Term Investments - Summary of Amortized Cost and Estimated Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 140,701	$ 46,481
Unrealized Gains	5	1
Unrealized Losses	(433)	(23)
Fair Value	140,273	46,459
U.S. Government Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	120,738	25,092
Unrealized Gains	2
Unrealized Losses	(366)	(20)
Fair Value	120,374	25,072
Corporate and agency bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	19,963	9,821
Unrealized Gains	3
Unrealized Losses	(67)	(3)
Fair Value	$ 19,899	9,818
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		11,568
Unrealized Gains		1
Fair Value		$ 11,569

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value On Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Cash equivalents:
Cash equivalents	$ 78,255	$ 150,129
Short-term investments:
Short-term investments	140,273	46,459
Money Market Fund
Cash equivalents:
Cash equivalents	78,255	141,378
U.S. Government Treasury Securities
Short-term investments:
Short-term investments	120,374	25,072
Corporate and agency bonds
Cash equivalents:
Cash equivalents		753
Short-term investments:
Short-term investments	19,899	9,818
Commercial Paper
Cash equivalents:
Cash equivalents		7,998
Short-term investments:
Short-term investments		11,569
Level 1
Cash equivalents:
Cash equivalents	78,255	141,378
Short-term investments:
Short-term investments	120,374	25,072
Level 1 | Money Market Fund
Cash equivalents:
Cash equivalents	78,255	141,378
Level 1 | U.S. Government Treasury Securities
Short-term investments:
Short-term investments	120,374	25,072
Level 2
Cash equivalents:
Cash equivalents		8,751
Short-term investments:
Short-term investments	19,899	21,387
Level 2 | Corporate and agency bonds
Cash equivalents:
Cash equivalents		753
Short-term investments:
Short-term investments	$ 19,899	9,818
Level 2 | Commercial Paper
Cash equivalents:
Cash equivalents		7,998
Short-term investments:
Short-term investments		$ 11,569

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended					3 Months Ended		9 Months Ended
	Feb. 28, 2022	Sep. 30, 2021	Feb. 28, 2021	Sep. 30, 2019	Jul. 31, 2019	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Mar. 31, 2019
Leases [Line Items]
ROU asset						$ 19,127		$ 19,127		$ 29,743
Lease liability						21,671		21,671
Operating lease costs						1,200	$ 2,000	4,100	$ 4,400
Cash paid for operating lease						1,100	1,300	3,200	3,600
Variable lease costs						$ 1,500	5,300	$ 3,600	9,100
Operating lease, weighted average remaining lease term						7 years 9 months 29 days		7 years 9 months 29 days
Operating lease, weighted average discount rate, percent						5%		5%
DMS Agreement
Leases [Line Items]
Lease expiration month and year					2021-07
Term of agreement					2 years
Lease, option to extend								The term may be extended by agreement of the parties for additional two-year periods upon written notice to the supplier at least 30 days prior to expiration of the then-current term. The DMS Agreement (or any individual SOW) may be terminated earlier by AlloVir at any time by providing 190 days’ notice.
Operating lease, existence of option to terminate					true
Lease, option to terminate								The DMS Agreement (or any individual SOW) may be terminated earlier by AlloVir at any time by providing 190 days’ notice.
Lease renewal term				2 years
Estimated lease term				3 years 9 months	4 years 3 months
Estimated lease expiring month and year				2023-07	2023-07
ROU asset				$ 6,300							$ 6,900
Lease liability				$ 6,300							$ 6,900
2020 DMS Agreement
Leases [Line Items]
Term of agreement			1 year
Lease renewal term			1 year
Estimated lease term			2 years
Estimated lease expiring month and year			2023-01
ROU asset			$ 3,100
Lease liability			2,500
Utilization fee			$ 3,200
Lessee operating lease, lease term including renewal option			2 years
Prepaid utilization fee			$ 600
Waltham Leases
Leases [Line Items]
Expiration date		Jul. 30, 2030
Operating lease, existence of option to extend		true
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. At September 30, 2022, the Company has no reasonable certainty that this option to extend will be exercised.
Tenant improvement allowance to be reimbursed		$ 3,100					3,100		3,100
Tenant improvement allowance, reimbursement period		2 years
Tenant improvement allowance						$ 700		$ 700
Lease commencement month and year		2021-09
Additional one time lease period		5 years
New Lease Agreement with BP Bay Colony LLC
Leases [Line Items]
ROU asset		$ 6,000					6,000		6,000
Lease liability		6,000					6,000		6,000
Sublease with AMAG Pharmaceuticals
Leases [Line Items]
ROU asset		17,300					17,300		17,300
Lease liability		$ 17,300					$ 17,300		$ 17,300
Original SOW Amendment under DMS Agreement | Lease Modification under ASC 842
Leases [Line Items]
ROU asset	$ (1,400)
Lease liability	$ (1,400)
Second SOW Amendment under DMS Agreement
Leases [Line Items]
Lease expiration month and year	2022-02
Second SOW Amendment under DMS Agreement | Lease Modification under ASC 842
Leases [Line Items]
ROU asset	$ (2,600)
Lease liability	(2,600)
Change Order to Modify Terms of SOW under 2020 DMS Agreement | Lease Modification under ASC 842
Leases [Line Items]
ROU asset	(1,500)
Lease liability	$ (1,300)

Leases - Summary of Operating L

Leases - Summary of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Leases [Abstract]
2022 (remaining 3 months)	$ 689
2023	3,049
2024	3,151
2025	3,229
2026	3,308
Thereafter	13,068
Total lease payments	26,494
Less: interest (5.00%)	4,823
Total lease liability	21,671
Lease liability - current	1,918	$ 6,591
Lease liability - long-term	$ 19,753	$ 23,475

Leases - Summary of Operating_2

Leases - Summary of Operating Lease Liabilities (Details) (Parenthetical)	Sep. 30, 2022
Leases [Abstract]
Operating lease interest percentage	5%

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Employee compensation and benefits	$ 5,652	$ 6,867
Professional fees	746	738
Research and development	5,270	3,573
Process development and manufacturing costs	1,282	7,685
Other	727	1,289
Total accrued expenses	$ 13,677	$ 20,152

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 26, 2022	Sep. 30, 2022	Dec. 31, 2021	Aug. 03, 2020
Class Of Stock [Line Items]
Preferred stock, par or stated value per share		$ 0.0001	$ 0.0001
Preferred stock, shares authorized		10,000,000	10,000,000
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Common stock, shares authorized		150,000,000	150,000,000
Common stock, par value		$ 0.0001	$ 0.0001
IPO
Class Of Stock [Line Items]
Preferred stock, par or stated value per share				$ 0.0001
Preferred stock, shares authorized				10,000,000
Offering price per share				$ 17
Securities Purchase Agreement
Class Of Stock [Line Items]
Common stock, par value	$ 0.0001
Net proceeds with certain investors	$ 126,400
Offering costs	$ 200
Share issued to investors	27,458,095
Offering price per share	$ 4.61
Underwriting Discounts Commissions	$ 0

Stockholders Equity - Schedule

Stockholders Equity - Schedule of Reserved Shares of Common Stock for Issuance (Details) - shares	Sep. 30, 2022	Dec. 31, 2021	Jul. 31, 2020
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	15,335,180	13,445,714
2020 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	537,997		611,354
Option To Purchase Common Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	8,499,509	6,155,055
Unvested Restricted Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	2,746,971	2,866,909
Stock Available For Grant | 2020 Stock Option and Grant Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	3,550,703	3,812,396
Stock Available For Issuance | 2020 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	537,997	611,354

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 10,855	$ 10,286	$ 32,273	$ 28,115
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,890	4,010	11,122	11,274
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 6,965	$ 6,276	$ 21,151	$ 16,841

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 01, 2022	Jul. 02, 2020	Jul. 31, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reserved shares of common stock for issuance				15,335,180		15,335,180		13,445,714
Weighted average grant-date fair value of stock options granted						$ 5.62
Common stock, par value				$ 0.0001		$ 0.0001		$ 0.0001
Share based compensation expense				$ 10,855,000	$ 10,286,000	$ 32,273,000	$ 28,115,000
Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares granted						1,559,721
Unrecognized stock-based compensation cost				33,200,000		$ 33,200,000
Weighted average period of cost expected to be recognized						2 years 8 months 15 days
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period of cost expected to be recognized						2 years 4 months 17 days
Unrecognized stock-based compensation expenses				$ 63,900,000		$ 63,900,000
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
Common stock shares granted				6,715,415		6,715,415
Number of shares of common stock issuable upon exercise of outstanding options				64,042		64,042
Reserved shares of common stock for issuance				0		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%
Shares added to number of available shares under plan	3,528,817
Common stock issuable upon exercise of outstanding options						8,435,467
2020 Stock Option and Grant Plan | Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares granted						3,003,241
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				3,550,703		3,550,703		3,812,396
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	537,997		537,997
Cumulative increase in number shares reserved for issuance, percentage			1%
Common stock, par value			$ 0.0001
Annual increase in number of shares reserved for issuance			1,222,707
Percentage of payroll deductions of base salary or wages			15%
Percentage of maximum discount on purchase of shares of common stock			15%
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. The first ESPP offering period was shortened in duration to three months and commenced on April 1, 2022 and ended on June 30, 2022. New six-month offering periods will commence each January 1 and July 1 thereafter during the term of the plan, with the administrator having the right to establish different offering periods.
Purchase of common stock under the employee stock purchase plan				0		73,357
Share based compensation expense				$ 100,000		$ 200,000
Cash received from purchases under the ESPP						$ 200,000
Share issued, average price per share				$ 3.32		$ 3.32
2020 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Base salary or wages			$ 25,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Common Stock Activity (Details) - Restricted Common Stock	9 Months Ended
	Sep. 30, 2022 $ / shares shares
Number of Shares
Number of Shares, Unvested at January 1, 2022 | shares	2,866,909
Number of Shares, Granted | shares	1,559,721
Number of Shares, Forfeited | shares	(136,888)
Number of Shares, Vested | shares	(1,542,771)
Number of Shares, Unvested at September 30, 2022 | shares	2,746,971
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Unvested at January 1, 2022 | $ / shares	$ 15.45
Weighted Average Grant Date Fair Value, Granted | $ / shares	7.70
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	20.67
Weighted Average Grant Date Fair Value, Vested | $ / shares	11.03
Weighted Average Grant Date Fair Value, Unvested at September 30, 2022 | $ / shares	$ 13.27

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Number of Options Outstanding, Beginning Balance	6,155,055
Number of Options, Granted	2,974,481
Number of Options, Forfeited	(630,027)
Number of Options Outstanding, Ending Balance	8,499,509	6,155,055
Options vested and exercisable at September 30, 2022	2,636,881
Weighted Average Exercise Price, Options outstanding as of January 1, 2022	$ 23.42
Weighted Average Exercise Price, Granted	7.49
Weighted Average Exercise Price, Forfeited	23.34
Weighted Average Exercise Price, Options outstanding at September 30, 2022	17.85	$ 23.42
Weighted Average Exercise Price, Options vested and exercisable at September 30, 2022	$ 21.99
Weighted Average Contractual Life, Options outstanding	8 years 6 months 21 days	8 years 9 months 18 days
Weighted Average Contractual Life, Options vested and exercisable at September 30, 2022	8 years 18 days
Aggregate Intrinsic Value, Options outstanding at January 1, 2022	$ 480
Aggregate Intrinsic Value, Options outstanding at September 30, 2022	3,677	$ 480
Aggregate Intrinsic Value, Options vested and exercisable at September 30, 2022	$ 189

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Estimated Fair Value Assumptions Using Black Scholes Option-Pricing Model (Details) - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Expected term (in years)	6 years 1 month 9 days	6 years 25 days
Expected volatility	90.78%	90.35%
Risk-free interest rate	2.89%	2.16%
Fair value of common stock	$ 4.19	$ 7.49

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 0	$ 0	$ 200,000	$ 0
Deferred income tax expense (benefit)	$ 0	$ 0	$ 200,000	$ 0

Net Loss per Share - Computatio

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
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Net loss – basic and diluted	$ (42,072)	$ (45,510)	$ (130,574)	$ (114,021)
Denominator:
Weighted-average common shares outstanding - basic	84,948,837	62,962,434	71,213,219	62,588,898
Weighted-average common shares outstanding - diluted	84,948,837	62,962,434	71,213,219	62,588,898
Net loss per share - basic	$ (0.50)	$ (0.72)	$ (1.83)	$ (1.82)
Net loss per share - diluted	$ (0.50)	$ (0.72)	$ (1.83)	$ (1.82)

Net Loss per Share - Potential

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
	Sep. 30, 2022	Sep. 30, 2021
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	8,499,509	6,028,476
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,746,971	3,126,635

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Aug. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Amount due to related party	$ 81,000		$ 81,000			$ 1,742,000
Consulting fees to members of management and board of directors	100,000	$ 100,000	400,000	$ 300,000
BaseCamp
Related Party Transaction [Line Items]
Prepaid expenses					$ 2,000,000
ElevateBio and Affiliates
Related Party Transaction [Line Items]
Prepaid expenses	2,100,000		2,100,000			0
Expenses related to services with related party	600,000	$ 600,000	2,700,000	$ 4,100,000
Amount due to related party	$ 100,000		$ 100,000			$ 1,700,000