0001564590-21-015250 | 10-K | XBRL Viewer

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2020	Mar. 19, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	Inozyme Pharma, Inc.
Entity Central Index Key	0001693011
Entity Incorporation, State or Country Code	DE
Entity File Number	001-39397
Entity Tax Identification Number	38-4024528
Entity Address, Address Line One	321 Summer Street
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02210
City Area Code	857
Local Phone Number	330-4340
Title of 12(b) Security	Common stock, par value $0.0001 per share
Trading Symbol	INZY
Security Exchange Name	NASDAQ
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		23,464,130
Entity Public Float			$ 0
Documents Incorporated by Reference	The registrant intends to file a definitive proxy statement pursuant to Regulation 14A within 120 days of the end of the fiscal year ended December 31, 2020. Portions of such definitive proxy statement are incorporated by reference into Part III of this Annual Report on Form 10-K.

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 28,040,000	$ 31,605,000
Short-term investments	119,657,000	15,527,000
Prepaid expenses and other current assets	3,282,000	328,000
Total current assets	150,979,000	47,460,000
Property and equipment, net	2,648,000	298,000
Restricted cash	354,000	130,000
Long-term investments	12,199,000	0
Prepaid expenses - noncurrent	3,183,000
Deferred issuance costs		56,000
Total assets	169,363,000	47,944,000
Current liabilities:
Accounts payable	3,069,000	901,000
Accrued expenses	6,904,000	2,335,000
Total current liabilities	9,973,000	3,236,000
Deferred lease obligations	1,287,000
Total liabilities	11,260,000	3,236,000
Commitments (Note 7)
Convertible preferred stock		77,927,000
Stockholders’ equity (deficit):
Preferred Stock, $0.0001 par value - 5,000,000 shares authorized at December 31, 2020 and no shares authorized at December 31, 2019; No shares issued and outstanding at December 31, 2020 or December 31, 2019
Common Stock, $0.0001 par value – 200,000,000 shares authorized at December 31, 2020 and 129,000,000 shares authorized at December 31, 2019; 23,384,969 shares issued and outstanding at December 31, 2020 and 1,204,630 shares issued and outstanding at December 31, 2019	2,000
Additional paid in-capital	249,175,000	1,428,000
Accumulated other comprehensive income	2,000	5,000
Accumulated deficit	(91,076,000)	(34,652,000)
Total stockholders’ equity (deficit)	158,103,000	(33,219,000)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 169,363,000	47,944,000
Series A Convertible Preferred Stock
Current liabilities:
Convertible preferred stock		44,657,000
Series A-2 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock		$ 33,270,000

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Convertible preferred stock, shares authorized		95,982,862
Convertible preferred stock, shares issued		72,416,431
Convertible preferred stock, shares outstanding		72,416,431
Convertible preferred stock, liquidation preference		$ 82,550
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	129,000,000
Common stock, shares issued	23,384,969	1,204,630
Common stock, shares outstanding	23,384,969	1,204,630
Series A Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	0	48,850,000
Convertible preferred stock, shares issued	0	48,850,000
Convertible preferred stock, shares outstanding	0	48,850,000
Convertible preferred stock, liquidation preference	$ 0	$ 48,850
Series A-2 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	0	47,132,862
Convertible preferred stock, shares issued	0	23,566,431
Convertible preferred stock, shares outstanding	0	23,566,431
Convertible preferred stock, liquidation preference	$ 0	$ 33,700

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 46,493	$ 16,220
General and administrative	10,548	4,586
Total operating expenses	57,041	20,806
Loss from operations	(57,041)	(20,806)
Other income (expense):
Interest income	370	1,106
Other income (expense), net	247	(24)
Other income (expense), net	617	1,082
Net loss	(56,424)	(19,724)
Other comprehensive (loss) income:
Unrealized (losses) gains on available-for-sale securities	(3)	7
Total other comprehensive (loss) income	(3)	7
Comprehensive loss	(56,427)	(19,717)
Net loss attributable to common stockholders—basic and diluted	$ (56,424)	$ (19,724)
Net loss per share attributable to common stockholders—basic and diluted	$ (5.11)	$ (16.67)
Weighted-average common shares outstanding—basic and diluted	11,036,500	1,183,147

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2018	$ (13,875)				$ 1,055	$ (2)	$ (14,928)
Temporary equity, shares at Dec. 31, 2018		48,850,000	7,482,515
Temporary equity, balance at Dec. 31, 2018		$ 44,657	$ 10,372
Balance, shares at Dec. 31, 2018				1,135,015
Issuance of Convertible Preferred Stock,net of issuance costs			$ 22,898
Issuance of Series A-2 Convertible Preferred Stock,net of issuance costs, shares			16,083,916
Stock-based compensation	301				301
Exercise of stock options	72				72
Exercise of stock options, shares				69,615
Comprehensive income:
Unrealized gain (loss) on investments	7					7
Net loss	(19,724)						(19,724)
Balance at Dec. 31, 2019	$ (33,219)				1,428	5	(34,652)
Temporary equity, shares at Dec. 31, 2019	72,416,431	48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019	$ 77,927	$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
Issuance of Convertible Preferred Stock,net of issuance costs			$ 33,638
Issuance of Series A-2 Convertible Preferred Stock,net of issuance costs, shares			23,566,431
Issuance of shares to acquire in-process research and development			$ 17,759
Issuance of shares to acquire in-process, shares			8,294,360
Initial public offering, net of issuance costs	115,915			$ 1	115,914
Initial public offering, net of issuance costs, shares				8,050,000
Conversion of convertible preferred stock into common stock	129,324	$ (44,657)	$ (84,667)	$ 1	129,323
Conversion of convertible preferred stock into common stock, shares		(48,850,000)	(55,427,222)	13,953,850
Stock-based compensation	2,308				2,308
Exercise of stock options	$ 202				202
Exercise of stock options, shares	176,489			176,489
Comprehensive income:
Unrealized gain (loss) on investments	$ (3)					(3)
Net loss	(56,424)						(56,424)
Balance at Dec. 31, 2020	$ 158,103			$ 2	$ 249,175	$ 2	$ (91,076)
Temporary equity, shares at Dec. 31, 2020		0	0
Balance, shares at Dec. 31, 2020				23,384,969

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Issuance costs	$ 3.9
Series A-2 Convertible Preferred Stock
Issuance costs	$ 0.1	$ 0.1

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net loss	$ (56,424)	$ (19,724)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	217	83
Write-off of acquired in-process research and development	17,759
Stock-based compensation expense	2,308	301
Amortization of premiums and discounts on marketable securities	277	(71)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,954)	(224)
Accounts payable	2,098	(83)
Accrued expenses	3,928	930
Other assets	(3,183)	(22)
Net cash used in operating activities	(35,974)	(18,810)
Investing activities
Purchases of marketable securities	(177,922)	(24,662)
Maturities of marketable securities	61,311	16,410
Purchases of property and equipment	(568)	(139)
Net cash used in investing activities	(117,179)	(8,391)
Financing activities
Proceeds from issuance of Series A-2 Convertible Preferred Stock, net of issuance costs	33,638	22,898
Proceeds from exercise of stock options	202	72
Proceeds from initial public offering, net of offering costs	115,972
Net cash provided by financing activities	149,812	22,970
Net decrease in cash, cash equivalents and restricted cash	(3,341)	(4,231)
Cash, cash equivalents and restricted cash at beginning of period	31,735	35,966
Cash, cash equivalents and restricted cash at end of period	28,394	31,735
Supplemental cash flow information:
Cash and cash equivalents	28,040	31,605
Restricted cash	354	130
Cash, cash equivalents and restricted cash at end of period	28,394	$ 31,735
Issuance of shares to acquire in-process research and development	17,759
Property and equipment unpaid at end of period	605
Deferred offering costs in accrued expenses	57
Deferred lease obligations - non-cash	$ 1,394

Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Basis of Presentation

1. Organization and Basis of Presentation

Inozyme Pharma, Inc. (the “Company”) is a clinical-stage rare disease biopharmaceutical company developing novel therapeutics for the treatment of diseases of abnormal mineralization impacting the vasculature, soft tissue and skeleton.

The Company is pursuing the development of therapeutics to address the underlying causes of these debilitating diseases. It is well established that two genes, ENPP1 and ABCC6, play key roles in a critical mineralization pathway and that defects in these genes lead to abnormal mineralization. The Company is initially focused on developing a novel therapy to treat rare genetic diseases of ENPP1 and ABCC6 deficiencies.

The Company’s lead product candidate, INZ-701, is a soluble, recombinant, or genetically engineered, fusion protein that is designed to correct a defect in the mineralization pathway caused by ENPP1 and ABCC6 deficiencies. This pathway is central to the regulation of calcium deposition throughout the body and is further associated with neointimal proliferation, or the overgrowth of smooth muscle cells inside blood vessels.

On July 17, 2020, the Company effected a one-for-7.4730 reverse stock split of the Company’s common stock. All share and per share amounts in the consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. Shares of common stock underlying outstanding stock options and other equity instruments were proportionately reduced and the respective exercise prices, if applicable, were proportionately increased in accordance with the terms of the appropriate securities agreements. Shares of common stock reserved for issuance upon the conversion of the Company’s convertible preferred stock were proportionately reduced and the respective conversion prices were proportionately increased. Stockholders entitled to fractional shares as a result of the reverse stock split received a cash payment in lieu of receiving fractional shares.

On July 28, 2020, the Company completed its initial public offering (“IPO”) pursuant to which it issued 7,000,000 shares of its common stock at a public offering price of $16.00 per share, and on July 30, 2020, the Company sold an additional 1,050,000 shares pursuant to the exercise by the underwriters of their option to purchase additional shares. The Company received net proceeds from its IPO, inclusive of the exercise by the underwriters of their option to purchase additional shares, of $115.9 million, after deducting underwriting discounts and commissions and offering expenses. Upon the closing of the IPO, all 104,277,222 shares of the then outstanding preferred stock automatically converted into 13,953,850 shares of common stock.

Basis of Presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Liquidity, Capital Resources, and Going Concern

Since the Company’s incorporation in 2017 and through December 31, 2020, the Company has devoted substantially all of its efforts to raising capital, building infrastructure, developing intellectual property and conducting research and development. The Company incurred net losses of $56.4 million and $19.7 million in the years ended December 31, 2020 and 2019, respectively, and had an accumulated deficit of $91.1 million as of December 31, 2020. The Company had cash, cash equivalents, and short-term and long-term investments of $159.9 million and $47.1 million as of December 31, 2020 and 2019, respectively.

The accompanying 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. The Company has incurred recurring losses and negative cash flows from operations since inception and has primarily funded its operations with proceeds from the issuance of convertible preferred stock, and the Company’s IPO completed on July 28, 2020. The Company expects its operating losses and negative operating cash flows to continue into the foreseeable future as it continues to expand its research and development efforts.

The Company believes that its cash, cash equivalents, and short-term and long-term investments as of December 31, 2020 will be sufficient to fund its operating expenses and capital expenditure requirements for at least twelve months from the date of filing this Annual Report on Form 10-K. The Company will need additional funding to support its planned operating activities. If the Company is unable to obtain additional funding, it would be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion, or commercialization efforts, which could adversely affect its business prospects.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Inozyme Securities Corp., which is a Massachusetts subsidiary created to buy, sell, and hold securities, Inozyme Ireland Limited, and Inozyme Pharma Switzerland GmbH. All intercompany transactions and balances have been eliminated.

Use of Estimates

The preparation of the Company’s financial statements 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. Estimates and judgments are based on historical information and other market-specific or various relevant assumptions, including, in certain circumstances, future projections that management believes to be reasonable under the circumstances. Actual results could differ materially from estimates. Significant estimates and assumptions are used for, but not limited to the accruals for research and development expenses, the fair value of equity instruments issued prior to the IPO, and the grant date fair value of stock-based awards. For equity instruments issued prior to the completion of the Company’s IPO, the Company utilized various valuation methodologies in accordance with the framework of the 2013 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its equity instruments. The Company evaluates its estimates and assumptions on an ongoing basis. All revisions to accounting estimates are recognized in the period in which the estimates are revised and in any future periods affected.

Concentration of Credit Risk and Off-Balance Sheet Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and short-term and long-term investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits and limits its exposure to credit risk by placing its cash with high credit quality financial institutions. The Company’s investments are comprised of U.S. Treasury and U.S. government agency debt securities and commercial paper of corporations. The Company mitigates credit risk by maintaining a diversified portfolio and limiting the amount of investment exposure as to institution, maturity and investment type.

The Company has no significant off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents include cash in readily available checking accounts, money market accounts and certain marketable securities. Cash is carried at cost, which approximates its fair value. Cash equivalents are carried at fair market value.

Restricted Cash

Restricted cash is composed of amounts held to collateralize the letter of credit related to the Company’s lease arrangements. Restricted cash is classified as either current or non-current based on the terms of the underlying lease arrangement.

Short-Term and Long-Term Investments

The Company classifies its investments as available-for-sale and records such assets at estimated fair value on the balance sheet, with unrealized gains and losses on marketable securities, if any, reported as a component of accumulated other comprehensive income (loss). Realized gains and losses are calculated based on the specific-identification method and are recorded as a component of interest income. There have been no realized gains and losses for the years ended December 31, 2020 and 2019. The Company periodically reviews available-for-sale securities for other-than-temporary declines in fair value below the cost basis whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Marketable securities with a maturity date of one year or less from the balance sheet date are classified by the Company as short-term investments. Marketable securities with a maturity date of greater than one year from the balance sheet date are classified as long-term investments and are available to fund operations as needed. In accordance with the Company’s investment policy, at the time of purchase, the final maturity of each security within the portfolio shall not exceed 18 months and the weighted average maturity of the portfolio will be no greater than 12 months.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. The estimated useful lives of the Company’s property and equipment are as follows:

	Estimated Useful Life (In Years)
Laboratory equipment and manufacturing equipment		5
Furniture and fixtures		5
Computer equipment and software		3
Leasehold improvements	Lesser of asset life or lease term

Impairment of Long-lived Assets

As required under the applicable accounting guidance, the Company periodically reevaluates the original assumptions and rationale used in the establishment of the carrying value and estimated lives of all of its long-lived assets, including property and equipment. The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. An impairment loss is recognized when the total of estimated future undiscounted cash flows, expected to result from the use of the asset and its eventual disposition, are less than its carrying amount. Impairment, if any, would be assessed using discounted cash flows or other appropriate measures of fair value. There were no impairments for the years ended December 31, 2020 and 2019.

Accrued Research and Development Costs

The Company records accrued liabilities for estimated costs of research and development activities conducted by service providers for sponsored research, preclinical studies, clinical operations, and contract manufacturing activities.

The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued expenses in the accompanying consolidated balance sheets and within research and development expense in the accompanying consolidated statements of operations and comprehensive loss.

The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with service providers. The Company makes significant judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred since its inception.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs consist of direct and indirect internal costs related to specific projects as well as fees paid to other entities that conduct certain research and development activities on the Company’s behalf. Research and development costs also include the write-off of acquired in-process research and development assets with no future use.

Patent Costs

The Company expenses all costs as incurred in connection with patent applications, including direct application fees, and the legal and consulting expenses related to making such applications, and such costs are included in general and administrative expenses within the Company’s consolidated statements of operations and comprehensive loss.

Stock-Based Compensation

Stock-based compensation expense represents the cost of the grant date fair value of employee and non-employee stock option grants and restricted stock awards recognized over the requisite service period of the awards on a straight-line basis. For service-based awards that are subject to graded vesting, companies have the option to recognize compensation expense either on a straight-line or accelerated basis. The Company has elected to recognize compensation expense for these awards on a straight-line basis. The Company has elected to recognize forfeitures as they occur upon adoption of guidance per ASU No. 2016-09, Compensation – Stock Compensation.

The Company’s equity incentive plan allows for the issuance of restricted stock awards to employees and non-employees that may be subject to vesting. The unvested shares of any restricted stock awards are held in escrow as the stock award vests or until award holder termination, whichever occurs first. In the event of a termination, the Company has the right of repurchase, at its option, the portion of unvested stock awards from the terminated award holder.

Convertible Preferred Stock

The Company’s convertible preferred stock was classified as temporary equity and excluded from stockholders’ (deficit) equity as the potential redemption of such stock was outside the Company’s control. The carrying value of the convertible preferred stock was not adjusted to the redemption value until the contingent redemption events were considered to be probable of occurring.

Income Taxes

Income taxes have been accounted for using the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates applicable to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. A valuation allowance against deferred tax assets is recorded if, based upon the weight of all available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for income taxes in accordance with authoritative accounting guidance which states the impact of an uncertain income tax position is recognized at the largest amount that is “more likely than not” to be sustained upon audit by the relevant taxing authority. There are no unrecognized tax benefits included in the Company’s consolidated balance sheets at December 31, 2020 or 2019. The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. The Company has not recognized any interest or penalties in its consolidated statements of operations and comprehensive loss since inception.

Leases

The Company categorizes leases at their inception as either operating or capital leases. On certain lease arrangements, the Company may receive rent holidays or other incentives. The Company recognizes lease costs on a straight-line basis once control of the space is obtained, without regard to deferred payment terms, such as rent holidays, that defer the commencement date of required payments or escalating payment amounts. The difference between required lease payments and rent expense has been recorded in accrued expenses in the accompanying consolidated balance sheets. Additionally, incentives received are treated as a reduction of costs over the term of the agreement, as they are considered an inseparable part of the lease agreement. At December 31, 2020 and 2019, no capital leases were recorded in the consolidated balance sheets.

Deferred Issuance Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings, including the Company’s IPO, as deferred issuance costs until such financings are consummated. After consummation of such an equity financing, these costs are recorded as a reduction of the proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred issuance costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. The Company recorded deferred issuance costs at December 31, 2020 and 2019 of $0 and $0.1 million, respectively.

Net Loss Per Share

The Company follows the two-class method when computing net loss allocable to common securities per share as the Company has issued shares that meet the definition of participating securities, which include shares of: (i) Series A Convertible Preferred Stock; and (ii) Series A-2 Convertible Preferred Stock. The two-class method requires a portion of net income to be allocated to the participating securities to determine net income allocable to the common securities. During periods of loss, there is no allocation required under the two-class method since the participating securities do not have a contractual obligation to fund the losses of the Company.

Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock and potentially dilutive securities outstanding during the period determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share calculation, diluted net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding after giving consideration to the dilutive effect of convertible preferred stock, restricted common stock, and stock options that are outstanding during the period. The Company has generated a net loss in all periods presented, therefore the basic and diluted net loss per share attributable to common stockholders are the same as the inclusion of the potentially dilutive securities would be anti-dilutive.

Segments

Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its Chief Executive Officer. The Company has determined it operates in a single operating segment and has one reportable segment. All long-lived assets of the Company reside in the United States.

Comprehensive Loss

The Company is required to report all components of comprehensive loss, including net loss, in the financial statements in the period in which they are recognized. Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss is comprised of the Company’s net loss and unrealized gains and losses on the Company’s investments and is presented within the consolidated statements of operations and comprehensive loss.

Foreign Currency Transactions

The Company maintains foreign bank accounts denominated in euros and Swiss francs. Foreign currency transactions are initially recorded by the Company using the exchange rates prevailing at the date of the transaction. At the balance sheet date, cash denominated in foreign currencies is translated at the period-end rates of exchange. Exchange gains and losses arising from the translation of foreign currency items are included in other income (expense), net in the consolidated statements of operations and comprehensive loss. The Company recognized a net foreign exchange gain of $247 thousand and a net foreign exchange loss of $24 thousand for the years ended December 31, 2020 and 2019, respectively.

Fair Value Measurements

The Company categorizes its assets and liabilities measured at fair value in accordance with the authoritative accounting guidance that establishes a consistent framework for measuring fair value, and expands disclosures for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as the 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 such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

•

Level 1- Unadjusted quoted prices in active markets that are accessible at the measurement date for identical assets or liabilities;

•

Level 2- Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; or

•

Level 3- Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

Emerging Growth Company Status

The Company is an “emerging growth company” (“EGC”) as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”), and the Company may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not EGCs. As an EGC, the Company can elect to take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards, and as a result of this election, the Company’s consolidated financial statements may not be comparable to companies that comply with public company FASB standards’ effective dates. The Company will remain an EGC until December 31, 2025, although if the market value of the Company’s common stock that is held by non-affiliates exceeds $700 million as of any June 30 before that time or if the Company has annual gross revenues of $1.07 billion or more in any fiscal year, the Company would cease to be an EGC as of December 31 of the applicable year. The Company would also cease to be an EGC if it issued more than $1 billion of non-convertible debt over a three-year period.

Recent Accounting Pronouncements

12 Months Ended

Dec. 31, 2020

Accounting Changes And Error Corrections [Abstract]

Recent Accounting Pronouncements

3. Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

Recently Issued and Adopted Accounting Standards

In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which modifies certain disclosure requirements on fair value measurements. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019. The Company adopted ASU 2018-13 on January 1, 2020 and the adoption did not have a material impact on its consolidated financial statements.

Recently Issued Accounting Standards Adopted in 2021

In February 2016, the FASB issued ASU 2016-02, Leases (“Topic 842”). The new standard, as amended, establishes a right-of-use model and requires a lessee to recognize on the balance sheet a right-of-use asset and corresponding lease liability for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the consolidated statements of operations and comprehensive loss. As a result of the FASB’s issuance of ASU No. 2020-05, “Revenue From Contracts With Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities”, the new standard is effective for annual periods beginning after December 15, 2021 for nonpublic entities, with early adoption permitted. On January 1, 2021, the Company adopted Topic 842 using the modified retrospective approach. The Company recorded operating lease assets (right-of-use assets) of $2.4 million and operating lease liabilities of $4.0 million and reversed a lease liability of $1.6 million related to straight-line rent and incentives. There was no impact to accumulated deficit upon adoption of Topic 842. The underlying assets of the Company’s leases are primarily office and laboratory space.

Recently Issued Accounting Standards Not Yet Adopted

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (“Topic 326”): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 and its subsequent related updates establish a new forward-looking “expected loss model” that requires entities to estimate current expected credit losses on accounts receivable and financial instruments by using all practical and relevant information. The new standard and its subsequent related updates are effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, with early adoption permitted. The Company is currently assessing the impact that adopting this standard will have on its consolidated financial statements but does not expect it to be material.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The accounting for the service element of a hosting arrangement that is a service contract is not affected by these amendments. ASU 2018-15 is effective for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021 for all non-public entities, with early adoption permitted. The Company is currently assessing the impact that adopting this standard will have on its consolidated financial statements.

In December 2019, the FASB issued ASU 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes. The new guidance simplifies the accounting for income taxes by removing several exceptions in the current standard and adding guidance to reduce complexity in certain areas, such as requiring that an entity reflect the effect of an enacted change in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date. The new standard is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022 for all non-public entities, with early adoption permitted. The Company is currently assessing the impact that adopting this standard will have on its consolidated financial statements.

Balance Sheet Details

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Details

4. Balance Sheet Details

Short-term investments consisted of the following (dollar amounts in thousands):

	December 31, 2020
Description	Maturity	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Commercial paper	1 year or less	$	94,873	$	5	$	(6	)	$	94,872
U.S. Treasury securities	1 year or less		11,614		2		(1	)		11,615
U.S. government agency debt securities	1 year or less		13,169		1		—			13,170
		$	119,656	$	8	$	(7	)	$	119,657

	December 31, 2019
Description	Maturity	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Commercial paper	1 year or less	$	10,903	$	3	$	—	$	10,906
Corporate debt securities	1 year or less		3,370		1		—		3,371
U.S. Treasury securities	1 year or less		1,249		1		—		1,250
		$	15,522	$	5	$	—	$	15,527

Long-term investments consisted of the following (dollar amounts in thousands):

	December 31, 2020
Description	Maturity	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
U.S. Treasury securities	After 1 year through 5 years	$	5,126	$	—	$	—	$	5,126
U.S. government agency debt securities	After 1 year through 5 years		7,072		1		—		7,073
		$	12,198	$	1	$	—	$	12,199

The Company did not have any long-term investments at December 31, 2019.

The Company concluded that the declines in market value of available-for-sale securities were temporary in nature and did not consider any of the investments to be other-than-temporarily impaired. In accordance with its investment policy, the Company invests in investment grade securities with high credit quality issuers, and generally limits the amount of credit exposure to any one issuer. The Company evaluates securities for other-than-temporary impairment at the end of each reporting period. Impairment is evaluated considering numerous factors, and their relative significance varies depending on the situation. Factors considered include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the issuer, and the Company’s intent and ability to hold the investment to allow for an anticipated recovery in fair value. Furthermore, the aggregate of individual unrealized losses that had been outstanding for 12 months or less was not significant as of December 31, 2020 and December 31, 2019. The Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell the investments before a recovery of their amortized cost bases, which may be maturity. The Company also believes that it will be able to collect both principal and interest amounts due at maturity.

Prepaid expenses and other current assets consisted of the following (dollar amounts in thousands):

	At December 31, 2020		At December 31, 2019
Interest receivable	$	155	$	104
Prepaid insurance		1,723		47
Prepaid research studies		804		—
Prepaid other		600		177
Total	$	3,282	$	328

Noncurrent prepaid expenses consisted of the following (dollar amounts in thousands):

At December 31,

2020

At December 31,

2019

Prepaid clinical trial and other

3,183

—

3,183

—

Property and equipment consisted of the following (dollar amounts in thousands):

	At December 31, 2020			At December 31, 2019
Laboratory equipment and manufacturing equipment	$	339		$	308
Furniture and fixtures		254			—
Computer equipment and software		287			53
Leasehold improvements		2,095			47
		2,975			408
Less accumulated depreciation		(327	)		(110	)
Total	$	2,648		$	298

Depreciation expense for the years ended December 31, 2020 and 2019 totaled $217 thousand and $83 thousand, respectively.

Accrued expenses consisted of the following (dollar amounts in thousands):

	At December 31, 2020		At December 31, 2019
Payroll and related liabilities	$	2,296	$	861
Professional fees		454		268
Research and development costs		2,997		1,086
Deferred rent		279		—
Other		878		120
Total	$	6,904	$	2,335

Fair Value Measurement

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurement

5. Fair Value Measurement

The following table represents the Company’s financial assets measured at fair value on a recurring basis and indicate the level of fair value hierarchy utilized to determine such fair values (in thousands):

			Fair Value Measurements at Reporting Date Using
Description	December 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (included in cash and cash equivalents)		15,739	$	15,739	$	—	$	—
Commercial paper		94,872		—		94,872		—
U.S. Treasury securities		16,741		16,741		—		—
U.S. government agency debt securities		20,243		—		20,243		—
Total assets	$	147,595	$	32,480	$	115,115	$	—

			Fair Value Measurements at Reporting Date Using
Description	December 31, 2019		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (included in cash and cash equivalents)	$	11,709	$	11,709	$	—	$	—
Commercial paper (included in cash and cash equivalents)		1,992		—		1,992		—
Corporate debt securities (included in cash and cash equivalents)		2,189		—		2,189		—
Commercial paper		10,906		—		10,906		—
Corporate debt securities		3,371		—		3,371		—
U.S. Treasury securities		1,250		1,250		—		—
Total assets	$	31,417	$	12,959	$	18,458	$	—

There have been no transfers between fair value levels during the years ended December 31, 2020 and December 31, 2019.

- 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 + Details

License and Sponsored Research Agreements

12 Months Ended

Dec. 31, 2020

Research And Development [Abstract]

License and Sponsored Research Agreements

6. License and Sponsored Research Agreements

In January 2017, the Company entered into a license agreement with Yale University (“Yale”), which was amended in May 2020 and July 2020, under which the Company licensed certain intellectual property related to ectonucleotide pyrophosphatase/phosphodiesterase enzymes, that is the basis for the Company’s INZ-701 development program. Pursuant to the license agreement, as partial upfront consideration, the Company made a payment of approximately $60,000 to Yale, which amount reflected unreimbursed patent expenses incurred by Yale prior to the date of the license agreement. The Company is responsible for paying Yale an annual license maintenance fee in varying amounts throughout the term ranging from the low tens of thousands of dollars to the high tens of thousands of dollars. For the years ended December 31, 2020 and 2019, the Company incurred a total of $44,000 and $10,000, respectively, in license maintenance fees to Yale. The Company is required to pay Yale $3.0 million, based on the achievement of a specified net product sales milestone or specified development and commercialization milestones, for each therapeutic and prophylactic licensed product developed. In addition, the Company is required to pay Yale an amount in the several hundreds of thousands of dollars, based on the achievement of a specified net product sales milestone or specified development and commercialization milestones, for each diagnostic licensed product developed. While the agreement remains in effect, the Company is required to pay Yale low single-digit percentage royalties on aggregate worldwide net sales of certain licensed products. Yale is guaranteed a minimum royalty payment amount (ranging in dollar amounts from the mid six figures to low seven figures) for each year after the first sale of a therapeutic or prophylactic licensed product that results in net sales. Yale is guaranteed a minimum royalty payment amount (ranging from the low tens of thousands of dollars to the mid tens of thousands of dollars) for each year after the first sale of a diagnostic licensed product that results in net sales. The Company must also pay Yale a percentage in the twenties of certain types of income it receives from sublicensees. The Company is also responsible for costs relating to the prosecution and maintenance of the licensed patents. Finally, subject to certain conditions, all payments due by the Company to Yale will be tripled following any patent challenge or challenge to a claim by Yale that a product is a licensed product under the agreement made by the Company against Yale if Yale prevails in such challenge.

In January 2017, the Company also entered into a corporate sponsored research agreement with Yale (the “Sponsored Research Agreement”), which was amended in February 2019, under which the Company agreed to provide research support funding in the aggregate amount of $2.4 million over the five year period from contract inception through 2021. The Company recorded research and development expenses associated with this arrangement of $0.4 million and $0.5 million in the years ended December 31, 2020 and 2019, respectively.

The Company did not record any research and development expense associated with other arrangements with Yale in the year ended December 31, 2020. The Company recorded research and development expense associated with other arrangements with Yale of $0.3 million in the year ended December 31, 2019.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

Leases

In March 2018, the Company entered into a non-cancelable agreement to lease 2,605 square feet of office space in Boston, Massachusetts. The lease term for this office space began in June 2018 and ended in April 2020. Additionally, in July 2018, the Company entered into an agreement to lease 3,560 square feet of laboratory space in Boston, Massachusetts. The lease term for this laboratory space began in July 2018 and ended in November 2020. The Company provided security deposits to the landlords totaling $34 thousand, of which $4 thousand and $34 thousand is included in prepaid expenses and other current assets in the accompanying balance sheet as of December 31, 2020 and 2019, respectively.

In December 2019, the Company entered into a non-cancelable agreement to lease 8,499 square feet of office space in Boston, Massachusetts. The lease term for this office space began in May 2020 and ends in October 2025. The lease is subject to yearly rent escalations. The Company has the option to extend the term of this lease for a term of five years. The Company provided a security deposit to the landlord in the form of a letter of credit totaling $130 thousand. The cash collateralizing the letter of credit is included in restricted cash in the accompanying balance sheets as of December 31, 2020 and 2019. As part of the lease, the Company received tenant allowances related to construction of the leased space. These allowances are used to offset the overall cost of the lease and are treated as a reduction in rent expense over the lease term.

In May 2020, the Company entered into a non-cancelable agreement to lease 6,244 square feet of laboratory space in Boston, Massachusetts. The lease term for the laboratory space began in October 2020 following the substantial completion of construction work and ends in December 2025. The lease is subject to yearly rent escalations. As part of the lease, the Company received tenant allowances related to construction of the leased space. These allowances are used to offset the overall cost of the lease and are treated as a reduction in rent expense over the lease term.

Total future minimum commitments under non-cancellable leases as of December 31, 2020 are as follows (dollar amounts in thousands):

Year Ending December 31,
2021		979
2022		968
2023		992
2024		1,016
2025		944
Thereafter		-
	$	4,899

Rent expense recognized on a straight-line basis over the terms of the leases for the years ended December 31, 2020 and 2019 was $654 thousand and $449 thousand, respectively.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters arising out of the relationship between such parties and the Company. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations as of December 31, 2020 or December 31, 2019.

Legal Proceedings

The Company is not currently a party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses the costs related to its legal proceedings as they are incurred. No such costs have been incurred during the years ended December 31, 2020 and 2019.

Convertible Preferred Stock and Stockholders' Equity

12 Months Ended

Dec. 31, 2020

Convertible Preferred Stock And Stockholders Equity [Abstract]

Convertible Preferred Stock and Stockholders' Equity

8. Convertible Preferred Stock and Stockholders’ Equity

Convertible Preferred Stock

Series A Convertible Preferred Stock

In January 2017, the Company converted from a Delaware limited liability company to a Delaware corporation. In connection with the conversion to a corporation, 100,000 shares of Series A Convertible Preferred Stock of the Company were issued to stockholders upon conversion of all outstanding shares of Series A-1 Convertible Preferred Stock of the limited liability company.

In January 2017, the Company entered into a Series A Convertible Preferred Stock Purchase Agreement, which was amended and restated in April 2017 (as amended and restated, the “Series A Agreement”) under which it agreed to issue up to 48,750,000 shares of Series A Convertible Preferred Stock in two tranches. Under the Series A Agreement, the Company initially issued 27,083,333 shares at a price of $1.00 per share for net cash proceeds of $26.7 million from January 2017 through May 2017. The Series A Agreement provided for a second tranche closing based on the achievement of a defined milestone (the “Tranche Right”), pursuant to which the investors were required to purchase, and the Company to sell, an additional 21,666,667 shares of Series A Convertible Preferred Stock at a price of $1.00 per share upon the achievement of the defined milestone or waiver of the milestone. In November 2018, the Company sold 21,666,667 shares of Series A Convertible Preferred Stock at a price of $1.00 per share for proceeds of $21.6 million.

The Company concluded that the Tranche Right met the definition of a freestanding financial instrument, as the Tranche Right was legally detachable and separately exercisable from the Series A Convertible Preferred Stock. Therefore, the Company allocated the net proceeds between the Tranche Right and the Series A Convertible Preferred Stock. Since the Series A Convertible Preferred Stock was contingently redeemable upon the occurrence of a deemed liquidation event, the Tranche Right was classified as a liability under ASC Topic 480 Distinguishing Liabilities from Equity and was initially recorded at fair value. The estimated fair value of the Tranche Right was determined using a Black-Scholes option-pricing model. The Tranche Right was remeasured at fair value at each reporting period prior to settlement in November 2018, with changes in fair value recorded as a component of other income (expense) in the consolidated statements of operations and comprehensive loss. The fair value of the Tranche Right was reclassified to Series A Convertible Preferred Stock at settlement.

Series A-2 Convertible Preferred Stock

In November 2018, the Company entered into a Series A-2 Convertible Preferred Stock Purchase Agreement, which was amended in March 2019 (as so amended, the “Series A-2 Agreement”) under which it agreed to issue up to 47,132,862 shares of Series A-2 Convertible Preferred Stock. Under the Series A-2 Agreement, the Company initially issued 7,482,515 shares at a price of $1.43 per share for net proceeds of $10.4 million in November 2018 and 16,083,916 shares at a price of $1.43 per share for net proceeds of $22.9 million in March 2019. The Series A-2 Agreement provided for a second tranche closing, pursuant to which the investors were required to purchase, and the Company to sell, an additional 23,566,431 shares of Series A-2 Convertible Preferred Stock at $1.43 per share upon the achievement of the defined milestone, or earlier upon board of directors and requisite stockholder approval to waive such requirement. The Company concluded that the second tranche did not meet the definition of a freestanding financial instrument and therefore did not require separate accounting. In June 2020, the board of directors and requisite stockholders approved such waiver and the Company issued 23,566,431 shares of Series A-2 Convertible Preferred Stock at a price of $1.43 per share for net proceeds of $33.6 million.

In July 2020, the Company increased the number of authorized shares of Series A-2 Convertible Preferred Stock from 47,132,862 to 55,427,222. In July 2020, the Company issued 8,294,360 shares of Series A-2 Convertible Preferred Stock to Alexion Pharmaceuticals, Inc. (“Alexion”) in consideration for the sale and assignment to the Company of specified patent rights and other specified assets related to ENPP1.

In July 2020, the Company eliminated the per share and gross proceeds thresholds for a firm-commitment underwritten public offering that triggers the automatic conversion of all outstanding shares of preferred stock into common stock. On July 28, 2020, upon the closing of the Company’s IPO, all 104,277,222 shares of then outstanding preferred stock automatically converted into 13,953,850 shares of common stock.

In addition, on July 28, 2020, the Company amended and restated its certificate of incorporation to authorize 200,000,000 shares of common stock and 5,000,000 shares of preferred stock, which shares of preferred stock are currently undesignated. The Company does not have any outstanding preferred stock as of December 31, 2020.

The preferred stock authorized and outstanding, associated carrying values and liquidation preferences as of December 31, 2019 were as follows (dollar amounts in thousands):

	December 31, 2019
Description	Preferred stock authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Convertible Preferred Stock		48,850,000		48,850,000	$	44,657	$	48,850		6,536,856
Series A-2 Convertible Preferred Stock		47,132,862		23,566,431		33,270		33,700		3,153,537
		95,982,862		72,416,431	$	77,927	$	82,550		9,690,393

There have been no dividends declared on preferred stock or common stock by the Company’s board of directors as of December 31, 2020.

Equity Incentive Plans

In January 2017, the Company’s board of directors and stockholders adopted the 2017 Equity Incentive Plan, which was amended and restated in July 2017, (as so amended and restated, the “2017 Plan”), which provided for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock awards. The maximum number of shares of common stock that were authorized for issuance under the 2017 Plan was 2,730,496.

On July 17, 2020, the Company’s stockholders approved the 2020 Stock Incentive Plan (the “2020 Plan”), which became effective on July 23, 2020. The 2020 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The number of shares of the Company’s common stock reserved for issuance under the 2020 Plan is 1,588,315 shares, plus the 426,065 shares of common stock remaining available for issuance under the 2017 Plan as of July 23, 2020. The number of shares reserved under the 2020 Plan shall be annually increased on January 1, 2021 and each January 1 thereafter through January 1, 2030 by the lower of (i) 4% of the number of shares of common stock outstanding on the first day of such fiscal year and (ii) an amount determined by the Company’s board of directors.

As of the effective date of the 2020 Plan, no further awards will be made under the 2017 Plan. Any options or awards outstanding under the 2017 Plan remain outstanding and effective and are governed by their existing terms. The shares of the Company’s common stock subject to outstanding awards under the 2017 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right will be added back to the shares of common stock available for issuance under the 2020 Plan. No more than 1,588,315 shares of the Company’s common stock may be granted subject to incentive stock options under the 2020 Plan. As of December 31, 2020, 568,235 shares of common stock remain available for future issuance under the 2020 Plan. On January 1, 2021, the number of shares of common stock reserved under the 2020 Plan was increased by 935,398 shares.

For financial reporting purposes, the Company performed common stock valuations with the assistance of a third-party valuation specialist as of March 31, 2020, May 31, 2019, November 30, 2018, December 31, 2017 and April 30, 2017 to determine stock-based compensation expense for the stock options issued under the 2017 Plan prior to the IPO. Following the completion of the IPO, the fair value of the common stock underlying option grants is determined based on the closing price of the Company’s common stock on the Nasdaq Global Select Market on the date of grant.

The following table summarizes stock option activity under the Company’s equity incentive plans since December 31, 2019:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value (1)
						(in years)		(in thousands)
Outstanding at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Granted		1,628,265			12.23
Exercised		(176,489	)		1.12
Forfeited		(22,746	)		1.95
Outstanding at December 31, 2020		3,064,457		$	7.28		8.76	$	41,680
Exercisable at December 31, 2020		835,769		$	2.61		7.62	$	15,070
Vested and expected to vest at December 31, 2020		3,064,457		$	7.28		8.76	$	41,680

(1) The aggregate intrinsic value of stock 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 Company’s common stock.

During the year ended December 31, 2020 and December 31, 2019, the Company granted 1,628,265 and 1,009,125 stock options, respectively, at a weighted-average exercise price of $12.23 and $2.02, respectively. The weighted average grant date fair value of stock options granted in the years ended December 31, 2020 and 2019 was $9.15 per share and $1.51 per share, respectively. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2020 was $0.7 million. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2019 was $0.1 million.

For purposes of calculating stock-based compensation, the Company estimates the fair value of stock options using the Black-Scholes option-pricing model. This model incorporates various assumptions, including the expected volatility, expected term, and interest rates. The underlying assumptions used to value stock options granted to participants using the Black-Scholes option-pricing were as follows:

	Years Ended December 31,
	2020			2019
Risk-free interest rate range	0.36% to 0.55%			1.63 to 2.51%
Dividend yield		0	%		0	%
Expected term of options (years)	6.08 to 6.78			6.78
Volatility rate range	86.54% to 99.85%			85.02% to 103.76%

Expected Term—The expected term of stock options represents the weighted average period the stock options are expected to be outstanding. The Company uses the simplified method for estimating the expected term, which calculates the expected term as the average time-to-vesting and the contractual life of the options for stock options issued to participants.

Expected Volatility—Due to the Company’s limited operating history and lack of company-specific historical or implied volatility, the expected volatility assumption was determined by examining the historical volatilities of a group of industry peers whose share prices are publicly available. The Company expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price.

Risk-Free Interest Rate—The risk-free rate assumption is based on U.S. Treasury instruments, the terms of which were consistent with the expected term of the Company’s stock options.

Expected Dividend—The expected dividend assumption is based on the Company’s history and expectation of dividend payouts. The Company has not paid and does not intend to pay dividends.

Fair Value of Common Stock —Historically, the fair value of the shares of common stock underlying the stock options has been the responsibility of and is determined by the Company’s board of directors. Because there was no public market for the Company’s common stock prior to the Company’s IPO, the board of directors determined fair value of common stock at the time of grant of the option by considering a number of objective and subjective factors including independent third-party valuations of the Company’s common stock, sales of convertible preferred stock to unrelated third parties, operating and financial performance, the lack of liquidity of capital stock and the general and industry specific economic outlook, among other factors. Following the Company’s IPO, the fair value of the Company’s common stock has been determined based on the closing price of the Company’s common stock on the Nasdaq Global Select Market.

For the year ended December 31, 2020, the Company recognized employee-related stock-based compensation expense of $1.8 million and nonemployee stock-based compensation expense of $0.5 million. For the year ended December 31, 2019, the Company recognized employee-related stock-based compensation expense of $0.3 million and an immaterial amount of non-employee stock-based compensation expense.

The fair value of shares vested for the years ended December 31, 2020 and 2019 was $1.3 million and $0.3 million, respectively.

The total unrecognized compensation cost related to outstanding employee awards as of December 31, 2020 was $13.9 million and is expected to be recognized over a weighted average period of 2.6 years.

Employee Stock Purchase Plan

On July 17, 2020, the Company’s stockholders approved the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective on July 23, 2020. The ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 198,539 shares of the Company’s common stock. The number of shares of common stock reserved for issuance under the ESPP will automatically increase on January 1, 2021 and each January 1 thereafter through January 1, 2031, in an amount equal to the lowest of (1) 397,079 shares of the Company’s common stock, (2) 1% of the number of shares of the Company’s common stock outstanding on the first day of such fiscal year and (3) an amount determined by the Company’s board of directors. As of December 31, 2020, no shares have been purchased by employees under the ESPP. On January 1, 2021, the number of shares of common stock reserved under the ESPP was increased by 233,849 shares.

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

9. Income Taxes

During the years ended December 31, 2020 and 2019, the Company recorded net losses of $56.4 million and $19.7 million, respectively. Since it maintains a full valuation allowance on its deferred tax assets, the Company did not record an income tax benefit for the years ended December 31, 2020 and 2019.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	Year Ended December 31,
	2020				2019
Federal income tax at statutory rate		21.0		%		21.0		%
Permanent differences		(0.5	)			(0.9	)
State income tax, net of federal benefit		5.0				4.8
Federal and state research and development tax credits		0.9				0.7
Valuation allowance		(26.4	)			(24.6	)
Other		—				(1.0	)
Effective income tax rate		—		%		—		%

Deferred taxes are recognized for temporary differences between the bases of assets and liabilities for financial statement and income tax purposes. The significant components of the Company’s deferred tax assets as of December 31, 2020 and 2019 are comprised of the following (dollar amounts in thousands):

	December 31,
	2020			2019
Deferred tax assets:
Net operating losses	$	17,712		$	8,584
Research and development credits		1,007			429
Stock options		157			20
Accrued expenses		594			222
Deferred rent		408			—
Amortization		4,520			—
Other		173			77
Gross deferred tax assets		24,571			9,332
Less: Valuation allowance		(24,199	)		(9,320	)
Net deferred tax assets		372			12
Deferred tax liabilities:
Depreciation of fixed assets		(372	)		(12	)
Gross deferred tax liabilities		(372	)		(12	)
Non-current net deferred tax assets (liabilities)	$	—		$	—

As of December 31, 2020, the Company had gross federal operating loss carryforwards of $69.6 million, which may be available to offset future taxable income. Of the federal operating loss carryforwards, $5.6 million begin to expire in 2037 and $64.0 million do not expire. As of December 31, 2020, the Company had gross state operating loss carryforwards of $50.4 million, which may be available to offset future taxable income and which begin to expire in 2037.

As required by FASB ASC Topic 740, Income Taxes, management of the Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of net operating loss carryforwards and research and development credits. Under the applicable accounting standards, management has considered the Company’s history of losses and concluded that it is more likely than not that the Company will not recognize the benefits of federal and state deferred tax assets. Accordingly, a full valuation allowance of $24.2 million and $9.3 million has been established at December 31, 2020 and December 31, 2019, respectively. The increase in the valuation allowance of $14.9 million during 2020 was primarily due to the increase in net operating loss generated by the Company.

The Company also has federal and state research and development credit carryforwards totaling $1.0 million as of December 31, 2020. The federal research and development credit carryforwards will begin to expire in 2037, unless previously utilized. The state research and development credit carryforwards will begin to expire in 2040, unless previously utilized. The Company has generated research credits, but has not conducted a study to document the qualified activity. This study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development credit carryforwards and the valuation allowance.

The Company’s ability to use its net operating loss carryforwards (“NOLs”) and tax credit carryforwards to offset taxable income is subject to restrictions under Sections 382 and 383 of the United States Internal Revenue Code (the “Internal Revenue Code”). Under the Internal Revenue Code provisions, certain substantial changes in the Company’s ownership, including the sale of the Company or significant changes in ownership due to sales of equity, have limited and may limit in the future, the amount of NOLs which could be used annually to offset future taxable income. The Company has not yet completed an analysis of ownership changes. The Company may also experience ownership changes in the future as a result of subsequent shifts in its stock ownership, some of which may be outside the Company’s control. As a result, the Company’s ability to use its pre-change NOLs to offset U.S. federal taxable income may be subject to limitations, which could potentially result in increased future tax liability to the Company. In addition, at the state level, there may be periods during which the use of NOLs is suspended or otherwise limited, which could accelerate or permanently increase state taxes owed. Under the TCJA, the use of federal NOLs arising in taxable years beginning after December 31, 2017 is limited to 80% of current year taxable income and NOLs arising in taxable years ending after December 31, 2017 may not be carried back (though any such NOLs may be carried forward indefinitely). The Coronavirus Aid, Relief, and Economic Security (CARES) Act, enacted on March 27, 2020, retroactively and temporarily (for taxable years beginning before January 1, 2021) suspended application of the 80%-of-income limitation on the use of NOLs and provides that NOLs arising in any taxable year beginning after December 31, 2017, and before January 1, 2021 are generally eligible to be carried back up to five years.

The Company establishes reserves for uncertain tax positions based on management’s assessment of exposures associated with tax positions taken on tax return filings. The tax reserves are analyzed periodically and adjustments are made as events occur to warrant adjustment to the reserve. The Company does not have any reserves for uncertain tax positions as of December 31, 2020 and any change in position would result in a change in the valuation allowance maintained against its net deferred tax assets.

Interest and penalty charges, if any, related to unrecognized tax benefits would be classified as income tax expense in the accompanying consolidated statements of operations and comprehensive loss. As of December 31, 2020, the Company had no accrued interest related to uncertain tax positions. Since the Company is in a loss carryforward position, the Company is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available.

The tax law changes in the CARES Act did not have a material impact on the Company’s income tax provision.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Net Loss per Share

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Net Loss per Share

10. Net Loss per Share

Net Loss per Share Attributable to Common Stockholders

For purposes of the diluted net loss per share calculation, stock options, unvested restricted stock, and convertible preferred stock are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented. 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.

The Company excluded the following potential dilutive securities, presented based on amounts outstanding at December 31, 2020 and 2019, from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect:

	Year Ended December 31,
	2020		2019
Series A Convertible Preferred Stock (as converted to common stock)		—		6,536,856
Series A-2 Convertible Preferred Stock (as converted to common stock)		—		3,153,537
Options to purchase common stock		3,064,457		1,635,427
		3,064,457		11,325,820

Employee Benefit Plans

12 Months Ended

Dec. 31, 2020

Compensation And Retirement Disclosure [Abstract]

Employee Benefit Plans

11. Employee Benefit Plans

The Company established a defined contribution savings plan in 2018 for all eligible U.S. employees under Section 401(k) of the Internal Revenue Code. During the years ended December 31, 2020 and 2019, the Company did not make any employer contributions to the plan. Employees can designate the investment of their 401(k) accounts into several mutual funds. Administrative costs of the plan for each of the years ended December 31, 2020 and 2019, were immaterial.

Related Party Transactions

12 Months Ended

Dec. 31, 2020

Related Party Transactions

12. Related Party Transactions

For the year ended December 31, 2019, the Company made payments of $0.1 million to one of its directors for scientific consulting and other expenses. In addition, in connection with his service as a consultant, the Company granted this director an option to purchase 66,907 shares at an exercise price per share of $2.02 in 2019. This individual resigned from the board of directors in May 2020, and as such, the scientific consulting services he provides to the Company going forward are no longer considered a related party transaction. During 2020, until the date of his resignation, the Company made payments to this individual totaling $56 thousand. As of December 30, 2020, no amount was due to this individual in connection with services rendered in his former capacity as a director.

See Note 6 for a description of the Company’s License and Sponsored Research Agreement with Yale.

Acquisition of Assets

12 Months Ended

Dec. 31, 2020

Business Combinations [Abstract]

Acquisition of Assets

13. Acquisition of Assets

In July 2020, the Company entered into an intellectual property asset purchase agreement with Alexion pursuant to which Alexion sold and assigned to the Company its right, title and interest in and to specified patent rights and other specified assets solely related to ENPP1. The Company issued 8,294,360 shares of its Series A-2 Convertible Preferred Stock to Alexion in consideration for the sale and assignment to the Company of such assets, with an estimated fair value of $17.8 million. The Company does not have any future payment obligations, contingent or otherwise, to Alexion in connection with this transaction. In addition, subject to certain specified qualifications set forth in the intellectual property asset purchase agreement, Alexion is obligated to assign to the Company its rights with respect to any other assets owned by it that are solely related to ENPP1.

The Company concluded that this transaction constituted a purchase of intellectual property assets and not a business combination. The Company will use these assets in research and development activities and believes they have no alternative future uses. Accordingly, the Company recognized expense of $17.9 million as a component of research and development expense in the year ended December 31, 2020, representing the value of the intellectual property assets acquired from Alexion and related acquisition costs as of the acquisition date.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation

Principles of Consolidation

Use of Estimates

Concentration of Credit Risk and Off-Balance Sheet Risk

The Company has no significant off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.

Cash and Cash Equivalents

Restricted Cash

Short-Term and Long-Term Investments

Property and Equipment

	Estimated Useful Life (In Years)
Laboratory equipment and manufacturing equipment		5
Furniture and fixtures		5
Computer equipment and software		3
Leasehold improvements	Lesser of asset life or lease term

Impairment Long-lived Assets

Impairment of Long-lived Assets

Accrued Research and Development Costs

Research and Development Costs

Patent Costs

Stock-Based Compensation

Convertible Preferred Stock

Income Taxes

Leases

Deferred Issuance Costs

Net Loss Per Share

Segments

Comprehensive Loss

Foreign Currency Transactions

Fair Value Measurements

•

Level 1- Unadjusted quoted prices in active markets that are accessible at the measurement date for identical assets or liabilities;

•

Level 3- Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

Emerging Growth Company Status

Recently Issued and Adopted Accounting Standards

Recently Issued Accounting Standards Adopted in 2021

Recently Issued Accounting Standards Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives of Property and Equipment

The estimated useful lives of the Company’s property and equipment are as follows:

	Estimated Useful Life (In Years)
Laboratory equipment and manufacturing equipment		5
Furniture and fixtures		5
Computer equipment and software		3
Leasehold improvements	Lesser of asset life or lease term

Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Short-Term Investments

Short-term investments consisted of the following (dollar amounts in thousands):

	December 31, 2020
Description	Maturity	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Commercial paper	1 year or less	$	94,873	$	5	$	(6	)	$	94,872
U.S. Treasury securities	1 year or less		11,614		2		(1	)		11,615
U.S. government agency debt securities	1 year or less		13,169		1		—			13,170
		$	119,656	$	8	$	(7	)	$	119,657

	December 31, 2019
Description	Maturity	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Commercial paper	1 year or less	$	10,903	$	3	$	—	$	10,906
Corporate debt securities	1 year or less		3,370		1		—		3,371
U.S. Treasury securities	1 year or less		1,249		1		—		1,250
		$	15,522	$	5	$	—	$	15,527

Schedule of Long Term Investments

Long-term investments consisted of the following (dollar amounts in thousands):

	December 31, 2020
Description	Maturity	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
U.S. Treasury securities	After 1 year through 5 years	$	5,126	$	—	$	—	$	5,126
U.S. government agency debt securities	After 1 year through 5 years		7,072		1		—		7,073
		$	12,198	$	1	$	—	$	12,199

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (dollar amounts in thousands):

	At December 31, 2020		At December 31, 2019
Interest receivable	$	155	$	104
Prepaid insurance		1,723		47
Prepaid research studies		804		—
Prepaid other		600		177
Total	$	3,282	$	328

Schedule of Non Current Prepaid Expenses

Noncurrent prepaid expenses consisted of the following (dollar amounts in thousands):

At December 31,

2020

At December 31,

2019

Prepaid clinical trial and other

3,183

—

3,183

—

Schedule of Property and Equipment

Property and equipment consisted of the following (dollar amounts in thousands):

	At December 31, 2020			At December 31, 2019
Laboratory equipment and manufacturing equipment	$	339		$	308
Furniture and fixtures		254			—
Computer equipment and software		287			53
Leasehold improvements		2,095			47
		2,975			408
Less accumulated depreciation		(327	)		(110	)
Total	$	2,648		$	298

Schedule of Accrued Expenses

Accrued expenses consisted of the following (dollar amounts in thousands):

	At December 31, 2020		At December 31, 2019
Payroll and related liabilities	$	2,296	$	861
Professional fees		454		268
Research and development costs		2,997		1,086
Deferred rent		279		—
Other		878		120
Total	$	6,904	$	2,335

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value

			Fair Value Measurements at Reporting Date Using
Description	December 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (included in cash and cash equivalents)		15,739	$	15,739	$	—	$	—
Commercial paper		94,872		—		94,872		—
U.S. Treasury securities		16,741		16,741		—		—
U.S. government agency debt securities		20,243		—		20,243		—
Total assets	$	147,595	$	32,480	$	115,115	$	—

			Fair Value Measurements at Reporting Date Using
Description	December 31, 2019		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (included in cash and cash equivalents)	$	11,709	$	11,709	$	—	$	—
Commercial paper (included in cash and cash equivalents)		1,992		—		1,992		—
Corporate debt securities (included in cash and cash equivalents)		2,189		—		2,189		—
Commercial paper		10,906		—		10,906		—
Corporate debt securities		3,371		—		3,371		—
U.S. Treasury securities		1,250		1,250		—		—
Total assets	$	31,417	$	12,959	$	18,458	$	—

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Commitments Under Non-Cancellable Leases

Total future minimum commitments under non-cancellable leases as of December 31, 2020 are as follows (dollar amounts in thousands):

Year Ending December 31,
2021		979
2022		968
2023		992
2024		1,016
2025		944
Thereafter		-
	$	4,899

Convertible Preferred Stock and Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Authorized, Issued, Outstanding and Preferences of Convertible Preferred Stock

The preferred stock authorized and outstanding, associated carrying values and liquidation preferences as of December 31, 2019 were as follows (dollar amounts in thousands):

	December 31, 2019
Description	Preferred stock authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Convertible Preferred Stock		48,850,000		48,850,000	$	44,657	$	48,850		6,536,856
Series A-2 Convertible Preferred Stock		47,132,862		23,566,431		33,270		33,700		3,153,537
		95,982,862		72,416,431	$	77,927	$	82,550		9,690,393

Summary of Stock Option Activity Under Equity Incentive Plans

The following table summarizes stock option activity under the Company’s equity incentive plans since December 31, 2019:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value (1)
						(in years)		(in thousands)
Outstanding at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Granted		1,628,265			12.23
Exercised		(176,489	)		1.12
Forfeited		(22,746	)		1.95
Outstanding at December 31, 2020		3,064,457		$	7.28		8.76	$	41,680
Exercisable at December 31, 2020		835,769		$	2.61		7.62	$	15,070
Vested and expected to vest at December 31, 2020		3,064,457		$	7.28		8.76	$	41,680

Employees

Summary of Assumptions Used to Value Stock Options Granted Using Black-Scholes Option-Pricing

	Years Ended December 31,
	2020			2019
Risk-free interest rate range	0.36% to 0.55%			1.63 to 2.51%
Dividend yield		0	%		0	%
Expected term of options (years)	6.08 to 6.78			6.78
Volatility rate range	86.54% to 99.85%			85.02% to 103.76%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	Year Ended December 31,
	2020				2019
Federal income tax at statutory rate		21.0		%		21.0		%
Permanent differences		(0.5	)			(0.9	)
State income tax, net of federal benefit		5.0				4.8
Federal and state research and development tax credits		0.9				0.7
Valuation allowance		(26.4	)			(24.6	)
Other		—				(1.0	)
Effective income tax rate		—		%		—		%

Significant Components of Deferred Tax Assets

The significant components of the Company’s deferred tax assets as of December 31, 2020 and 2019 are comprised of the following (dollar amounts in thousands):

	December 31,
	2020			2019
Deferred tax assets:
Net operating losses	$	17,712		$	8,584
Research and development credits		1,007			429
Stock options		157			20
Accrued expenses		594			222
Deferred rent		408			—
Amortization		4,520			—
Other		173			77
Gross deferred tax assets		24,571			9,332
Less: Valuation allowance		(24,199	)		(9,320	)
Net deferred tax assets		372			12
Deferred tax liabilities:
Depreciation of fixed assets		(372	)		(12	)
Gross deferred tax liabilities		(372	)		(12	)
Non-current net deferred tax assets (liabilities)	$	—		$	—

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Schedule of Potential Dilutive Securities from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders

	Year Ended December 31,
	2020		2019
Series A Convertible Preferred Stock (as converted to common stock)		—		6,536,856
Series A-2 Convertible Preferred Stock (as converted to common stock)		—		3,153,537
Options to purchase common stock		3,064,457		1,635,427
		3,064,457		11,325,820

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Jul. 30, 2020 USD ($) shares	Jul. 28, 2020 $ / shares shares	Jul. 17, 2020	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) shares
Organization And Basis Of Presentation [Line Items]
Reverse stock split of common stock			0.1338
Stockholders' equity, reverse stock split			one-for-7.4730 reverse stock split
Net proceeds issuance of common stock, deducting underwriting discounts and commissions \| $	$ 115,900
Number of outstanding preferred stock converted \| shares		104,277,222
Number of common stock issued upon conversion \| shares		13,953,850			9,690,393
Net loss \| $				$ 56,424	$ 19,724
Accumulated deficit \| $				91,076	34,652
Cash and cash equivalents and short term and long term investments \| $				$ 159,900	$ 47,100
IPO
Organization And Basis Of Presentation [Line Items]
Shares issued \| shares		7,000,000
Shares issued, price per share \| $ / shares		$ 16.00
Underwriters
Organization And Basis Of Presentation [Line Items]
Shares issued \| shares	1,050,000

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended		48 Months Ended
	Dec. 31, 2020 USD ($) Segment	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Off-balance sheet concentrations of credit risk description	The Company has no significant off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.
Off-balance sheet concentrations of credit risk	$ 0		$ 0
Realized gain and losses on investments as available-for-sale	0	$ 0
Impairments of long-lived assets	0	0
Unrecognized tax benefits	0	0	0
Interest or penalties			0
Deferred issuance costs	$ 0	100,000	$ 0
Number of operating segments \| Segment	1
Number of reportable segments \| Segment	1
Net foreign exchange gain (loss)	$ 247,000	$ (24,000)
Issuance period of non-convertible debt cease to be EGC	3 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Market value of common stock held by non-affiliates cease to be EGC				$ 700,000,000
Annual gross revenues cease to be EGC	$ 1,070,000,000
Issuance of non-convertible debt cease to be EGC	$ 1,000,000,000

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Laboratory Equipment and Manufacturing Equipment
Property Plant And Equipment [Line Items]
Estimated Useful Life (In Years)	5 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Estimated Useful Life (In Years)	5 years
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Estimated Useful Life (In Years)	3 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated Useful Life (In Years)	Lesser of asset life or lease term

Recent Accounting Pronouncements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2021	Dec. 31, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, immaterial effect	true
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201813Member
Accumulated deficit	$ (91,076,000)		$ (34,652,000)
Subsequent Event \| ASU 2016-02
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adoption date		Jan. 01, 2021
Change in accounting principle, accounting standards update, adopted		true
Operating lease, right of use assets		$ 2,400,000
Operating lease liabilities		4,000,000
Operating lease, reversed lease liability		1,600,000
Subsequent Event \| Revision of Prior Period, Accounting Standards Update, Adjustment \| ASU 2016-02
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated deficit		$ 0

Balance Sheet Details - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 119,656	$ 15,522
Gross Unrealized Gains	8	5
Gross Unrealized Losses	(7)
Estimated Fair Value	$ 119,657	$ 15,527
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Cost	$ 94,873	$ 10,903
Gross Unrealized Gains	5	3
Gross Unrealized Losses	(6)
Estimated Fair Value	$ 94,872	$ 10,906
U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Cost	$ 11,614	$ 1,249
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(1)
Estimated Fair Value	$ 11,615	$ 1,250
U S Government Agency Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less
Amortized Cost	$ 13,169
Gross Unrealized Gains	1
Estimated Fair Value	$ 13,170
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity		1 year or less
Amortized Cost		$ 3,370
Gross Unrealized Gains		1
Estimated Fair Value		$ 3,371

Balance Sheet Details - Schedule of Long-Term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 119,656	$ 15,522
Gross Unrealized Gains	8	5
Gross Unrealized Losses	(7)
Estimated Fair Value	$ 119,657	$ 15,527
U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Cost	$ 11,614	$ 1,249
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(1)
Estimated Fair Value	$ 11,615	$ 1,250
U S Government Agency Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less
Amortized Cost	$ 13,169
Gross Unrealized Gains	1
Estimated Fair Value	13,170
Long Term Investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	12,198
Gross Unrealized Gains	1
Estimated Fair Value	$ 12,199
Long Term Investments \| U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	After 1 year through 5 years
Amortized Cost	$ 5,126
Estimated Fair Value	$ 5,126
Long Term Investments \| U S Government Agency Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	After 1 year through 5 years
Amortized Cost	$ 7,072
Gross Unrealized Gains	1
Estimated Fair Value	$ 7,073

Balance Sheet Details - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Long-term investments	$ 12,199,000	$ 0
Depreciation expense	$ 217,000	$ 83,000

Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Interest receivable	$ 155	$ 104
Prepaid insurance	1,723	47
Prepaid research studies	804
Prepaid other	600	177
Total	$ 3,282	$ 328

Balance Sheet Details - Schedule of Noncurrent Prepaid Expenses (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Payables And Accruals [Abstract]
Prepaid clinical trial and other	$ 3,183
Prepaid expenses - noncurrent	$ 3,183

Balance Sheet Details - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,975	$ 408
Less accumulated depreciation	(327)	(110)
Total	2,648	298
Laboratory Equipment and Manufacturing Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	339	308
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	254
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	287	53
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,095	$ 47

Balance Sheet Details - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Payroll and related liabilities	$ 2,296	$ 861
Professional fees	454	268
Research and development costs	2,997	1,086
Deferred rent	279
Other	878	120
Total	$ 6,904	$ 2,335

Fair Value Measurement - Summary of Financial Assets Measured at Fair Value (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	$ 147,595	$ 31,417
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure	15,739	11,709
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure		1,992
Assets fair value disclosure	94,872	10,906
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	32,480	12,959
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure	15,739	11,709
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	115,115	18,458
Significant Other Observable Inputs (Level 2) \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure		1,992
Assets fair value disclosure	94,872	10,906
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure		2,189
Assets fair value disclosure		3,371
Corporate Debt Securities \| Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure		2,189
Assets fair value disclosure		3,371
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	16,741	1,250
U.S. Treasury Securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	16,741	$ 1,250
U.S. Government Agency Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	20,243
U.S. Government Agency Debt Securities \| Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	$ 20,243

Fair Value Measurement - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair value assets level 1 to level 2 transfers amount	$ 0	$ 0
Fair value assets level 2 to level 1 transfers amount	0	0
Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers into level 3	0	0
Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers out of level 3	$ 0	$ 0

License and Sponsored Research Agreements - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2019	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 46,493,000	$ 16,220,000
Yale
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Partial upfront consideration payment under license agreement		60,000
Milestone payment upon achievement of certain milestones		3,000,000
Yale \| Sponsored Research Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research support funding amount	$ 2,400,000
Research support funding period	5 years
Research support funding expiration year	2021
Research and development expenses		400,000	400,000
Yale \| Other Arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expenses		0	300,000
Yale \| License
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maintenance fees		$ 44,000	$ 10,000

Commitments and Contingencies - Additional Information (Details)	1 Months Ended				12 Months Ended
	May 31, 2020 ft²	Dec. 31, 2019 USD ($) ft²	Jul. 31, 2018 ft²	Mar. 31, 2018 ft²	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) ft²
Lessee Lease Description [Line Items]
Security deposits					$ 34,000
Rent expense					654,000	$ 449,000
Costs related to legal proceedings					0	0
Prepaid Expenses and Other Current Assets
Lessee Lease Description [Line Items]
Security deposits		$ 34,000			4,000	34,000
Restricted Cash \| Letter of Credit
Lessee Lease Description [Line Items]
Security deposits		$ 130,000			$ 130,000	$ 130,000
Office Space \| Boston, Massachusetts
Lessee Lease Description [Line Items]
Area of leased space \| ft²		8,499		2,605		8,499
Lessee operating lease commenced month and year		2020-05		2018-06
Lessee operating lease expiration month and year		2025-10		2020-04
Lessee, Operating Lease, Existence of Option to Extend [true false]		true
Lessee operating lease option to extend description					The Company has the option to extend the term of this lease for a term of five years.
Operating lease renewal term		5 years				5 years
Laboratory Space \| Boston, Massachusetts
Lessee Lease Description [Line Items]
Area of leased space \| ft²			3,560
Lessee operating lease commenced month and year	2020-10		2018-07
Lessee operating lease expiration month and year	2025-12		2020-11
Square feet under lease \| ft²	6,244

Commitments and Contingencies - Schedule of Future Minimum Commitments Under Non-Cancellable Leases (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2021	$ 979
2022	968
2023	992
2024	1,016
2025	944
Operating lease liability	$ 4,899

Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details)		1 Months Ended				5 Months Ended	12 Months Ended
	Jul. 23, 2020 shares	Jun. 30, 2020 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Nov. 30, 2018 USD ($) $ / shares shares	Jan. 31, 2017 Tranche shares	May 31, 2017 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Jan. 01, 2021 shares	Jul. 31, 2020 shares	Jul. 28, 2020 shares	Apr. 30, 2017 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued								72,416,431
Proceeds from issuance of Series A-2 Convertible Preferred Stock, net of issuance costs \| $							$ 33,638,000	$ 22,898,000
Convertible preferred stock, shares authorized								95,982,862
Preferred stock, shares outstanding							0	0
Number of common stock issued upon conversion								9,690,393			13,953,850
Common stock, shares authorized							200,000,000	129,000,000			200,000,000
Preferred stock, shares authorized							5,000,000	0			5,000,000
Dividends declared on preferred stock or common stock \| $							$ 0
Plan description	On July 17, 2020, the Company’s stockholders approved the 2020 Stock Incentive Plan (the “2020 Plan”), which became effective on July 23, 2020. The 2020 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The number of shares of the Company’s common stock reserved for issuance under the 2020 Plan is 1,588,315 shares, plus the 426,065 shares of common stock remaining available for issuance under the 2017 Plan as of July 23, 2020. The number of shares reserved under the 2020 Plan shall be annually increased on January 1, 2021 and each January 1 thereafter through January 1, 2030 by the lower of (i) 4% of the number of shares of common stock outstanding on the first day of such fiscal year and (ii) an amount determined by the Company’s board of directors.As of the effective date of the 2020 Plan, no further awards will be made under the 2017 Plan. Any options or awards outstanding under the 2017 Plan remain outstanding and effective and are governed by their existing terms. The shares of the Company’s common stock subject to outstanding awards under the 2017 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right will be added back to the shares of common stock available for issuance under the 2020 Plan. No more than 1,588,315 shares of the Company’s common stock may be granted subject to incentive stock options under the 2020 Plan. As of December 31, 2020, 568,235 shares of common stock remain available for future issuance under the 2020 Plan. On January 1, 2021, the number of shares of common stock reserved under the 2020 Plan was increased by 935,398 shares.
Options Outstanding, Granted							1,628,265	1,009,125
Weighted-average exercise price of options granted \| $ / shares							$ 12.23	$ 2.02
Weighted-average grant date fair value of options granted \| $ / shares							$ 9.15	$ 1.51
Aggregate intrinsic value of stock options exercised \| $							$ 700,000	$ 100,000
Fair value of shares vested \| $							1,300,000	$ 300,000
Total unrecognized compensation cost related to outstanding employee awards \| $							$ 13,900
Total unrecognized compensation cost related to outstanding employee awards, expected to be recognized over a weighted-average period							2 years 7 months 6 days
Share based compensation options to purchase number of common stock							3,064,457	1,635,427
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense \| $							$ 1,800,000	$ 300,000
Share-based Payment Arrangement, Nonemployee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense \| $							$ 500,000
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance										2,730,496
Two Thousand Twenty Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	1,588,315						568,235
Number of common stock reserved for issuance increase percentage on stock outstanding	4.00%
Two Thousand Twenty Stock Incentive Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance									935,398
Two Thousand Seventeen Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	426,065
Two Thousand Twenty Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance increase percentage on stock outstanding	1.00%
Plan description	The number of shares of common stock reserved for issuance under the ESPP will automatically increase on January 1, 2021 and each January 1 thereafter through January 1, 2031, in an amount equal to the lowest of (1) 397,079 shares of the Company’s common stock, (2) 1% of the number of shares of the Company’s common stock outstanding on the first day of such fiscal year and (3) an amount determined by the Company’s board of directors
Share based compensation options to purchase number of common stock	198,539
Increase in additional number of shares to be issued	397,079
Number of shares purchased							0
Two Thousand Twenty Employee Stock Purchase Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance									233,849
IPO
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock, shares outstanding											104,277,222
Maximum [Member] \| Two Thousand Twenty Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock granted, under 2020 plan							1,588,315
Series A Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued					100,000		0	48,850,000
Convertible preferred stock, shares authorized							0	48,850,000
Number of common stock issued upon conversion								6,536,856
Series A Convertible Preferred Stock \| Series A Convertible Preferred Stock Purchase Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued				21,666,667		27,083,333
Number of tranches \| Tranche					2
Shares issued, price per share \| $ / shares				$ 1.00		$ 1.00						$ 1.00
Proceeds from issuance of Series A-2 Convertible Preferred Stock, net of issuance costs \| $				$ 21,600,000		$ 26,700,000
Additional shares issued												21,666,667
Series A Convertible Preferred Stock \| Maximum [Member] \| Series A Convertible Preferred Stock Purchase Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued					48,750,000
Series A-2 Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued			16,083,916	7,482,515			0	23,566,431
Shares issued, price per share \| $ / shares		$ 1.43	$ 1.43	$ 1.43
Proceeds from issuance of Series A-2 Convertible Preferred Stock, net of issuance costs \| $		$ 33,600,000	$ 22,900,000	$ 10,400,000
Additional shares issued		23,566,431
Shares available for issuance to investors			23,566,431
Shares available for issuance, price per share \| $ / shares			$ 1.43
Convertible preferred stock, shares authorized							0	47,132,862
Number of common stock issued upon conversion								3,153,537
Series A-2 Convertible Preferred Stock \| Alexion Pharmaceuticals Inc
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued										8,294,360
Series A-2 Convertible Preferred Stock \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued				47,132,862
Convertible preferred stock, shares authorized										55,427,222
Series A-2 Convertible Preferred Stock \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Convertible preferred stock, shares authorized				47,132,862

Convertible Preferred Stock and Stockholders' Equity - Summary of Authorized, Issued, Outstanding and Preferences of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jul. 28, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Nov. 30, 2018	Jan. 31, 2017
Temporary Equity [Line Items]
Preferred stock authorized			95,982,862
Shares issued			72,416,431
Preferred stock outstanding			72,416,431
Carrying value			$ 77,927
Liquidation preference			$ 82,550
Common stock issuable upon conversion		13,953,850	9,690,393
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized	0		48,850,000
Shares issued	0		48,850,000				100,000
Preferred stock outstanding	0		48,850,000		48,850,000
Carrying value			$ 44,657		$ 44,657
Liquidation preference	$ 0		$ 48,850
Common stock issuable upon conversion			6,536,856
Series A-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized	0		47,132,862
Shares issued	0		23,566,431	16,083,916		7,482,515
Preferred stock outstanding	0		23,566,431		7,482,515
Carrying value			$ 33,270		$ 10,372
Liquidation preference	$ 0		$ 33,700
Common stock issuable upon conversion			3,153,537

Convertible Preferred Stock and Stockholders' Equity - Summary of Stock Option Activity Under Equity Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Convertible Preferred Stock And Stockholders Equity [Abstract]
Options Outstanding, Beginning Balance	1,635,427
Options Outstanding, Granted	1,628,265	1,009,125
Options Outstanding, Exercised	(176,489)
Options Outstanding, Forfeited	(22,746)
Options Outstanding, Ending Balance	3,064,457	1,635,427
Options Outstanding, Exercisable	835,769
Options Outstanding, Vested and expected to vest	3,064,457
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 1.64
Weighted Average Exercise Price, Granted	12.23	$ 2.02
Weighted Average Exercise Price, Exercised	1.12
Weighted Average Exercise Price, Forfeited	1.95
Weighted Average Exercise Price, Outstanding, Ending Balance	7.28	$ 1.64
Weighted Average Exercise Price, Exercisable	2.61
Weighted Average Exercise Price, Vested and expected to vest	$ 7.28
Weighted Average Remaining Contractual Term (in years), Outstanding	8 years 9 months 3 days	8 years 9 months 21 days
Weighted Average Remaining Contractual Term (in years), Exercisable	7 years 7 months 13 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	8 years 9 months 3 days
Aggregate Intrinsic Value, Outstanding	$ 41,680	$ 668
Aggregate Intrinsic Value, Exercisable	15,070
Aggregate Intrinsic Value, Vested and expected to vest	$ 41,680

Convertible Preferred Stock and Stockholders' Equity - Summary of Assumptions Used to Value Stock Options Granted to Employees using Black-Scholes Option-Pricing (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate range, minimum	0.36%	1.63%
Risk-free interest rate range, maximum	0.55%	2.51%
Dividend yield	0.00%	0.00%
Volatility rate range, minimum	86.54%	85.02%
Volatility rate range, maximum	99.85%	103.76%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term of options (years)	6 years 29 days	6 years 9 months 10 days
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term of options (years)	6 years 9 months 10 days

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Mar. 27, 2020	Jan. 01, 2018
Income Taxes Disclosure [Line Items]
Net loss	$ 56,424,000	$ 19,724,000
Income tax benefit	0	0
Deferred tax assets, valuation allowance	24,199,000	$ 9,320,000
Deferred tax assets, increase in valuation allowance	14,900,000
Tax cuts and jobs act federal net operating loss				80.00%
Suspend of tax cuts and jobs act federal net operating loss due to cares act			80.00%
Federal
Income Taxes Disclosure [Line Items]
Gross operating loss carryforwards	69,600,000
Operating loss carryforwards with expiration period	5,600,000
Operating loss carryforwards with no expiration period	$ 64,000,000
Operating loss carryforwards expiration year	2037
Federal \| Research and Development
Income Taxes Disclosure [Line Items]
Credit carryforward, expiration year	2037
State
Income Taxes Disclosure [Line Items]
Gross operating loss carryforwards	$ 50,400,000
Operating loss carryforwards expiration year	2037
State \| Research and Development
Income Taxes Disclosure [Line Items]
Credit carryforward, expiration year	2040
Federal and State \| Research and Development
Income Taxes Disclosure [Line Items]
Credit carryforwards	$ 1,000,000

Income Taxes - Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income tax at statutory rate	21.00%	21.00%
Permanent differences	(0.50%)	(0.90%)
State income tax, net of federal benefit	5.00%	4.80%
Federal and state research and development tax credits	0.90%	0.70%
Valuation allowance	(26.40%)	(24.60%)
Other		(1.00%)

Income Taxes - Significant Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating losses	$ 17,712	$ 8,584
Research and development credits	1,007	429
Stock options	157	20
Accrued expenses	594	222
Deferred rent	408
Amortization	4,520
Other	173	77
Gross deferred tax assets	24,571	9,332
Less: Valuation allowance	(24,199)	(9,320)
Net deferred tax assets	372	12
Deferred tax liabilities:
Depreciation of fixed assets	(372)	(12)
Gross deferred tax liabilities	$ (372)	$ (12)

Net Loss per Share - Schedule of Potential Dilutive Securities from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	3,064,457	11,325,820
Series A Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share		6,536,856
Series A-2 Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share		3,153,537
Options to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	3,064,457	1,635,427

Related Party Transactions - Additional Information (Details) - USD ($)	5 Months Ended	12 Months Ended
	May 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Number of shares granted, option to purchase		1,628,265	1,009,125
Weighted-average exercise price of options granted		$ 12.23	$ 2.02
Director
Related Party Transaction [Line Items]
Scientific consulting and other expenses	$ 56,000		$ 100,000
Number of shares granted, option to purchase			66,907
Weighted-average exercise price of options granted			$ 2.02
Due to related party		$ 0

Acquisition of Assets - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Nov. 30, 2018
Business Acquisition [Line Items]
Shares issued			72,416,431
Series A-2 Convertible Preferred Stock
Business Acquisition [Line Items]
Shares issued		0	23,566,431	16,083,916	7,482,515
Alexion Pharmaceuticals Inc
Business Acquisition [Line Items]
Acquired intellectual property, research and development expenses		$ 17.9
Alexion Pharmaceuticals Inc \| Intellectual Property
Business Acquisition [Line Items]
Acquisition of intellectual property, estimated fair value	$ 17.8
Alexion Pharmaceuticals Inc \| Series A-2 Convertible Preferred Stock
Business Acquisition [Line Items]
Shares issued	8,294,360