0001564590-20-053211 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2020	Nov. 06, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
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 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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		23,372,844

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 59,858,000	$ 31,605,000
Short-term investments	99,644,000	15,527,000
Prepaid expenses and other current assets	4,475,000	328,000
Total current assets	163,977,000	47,460,000
Property and equipment, net	2,455,000	298,000
Restricted cash	354,000	130,000
Long-term investments	12,207,000	0
Deferred issuance costs		56,000
Total assets	178,993,000	47,944,000
Current liabilities:
Accounts payable	3,665,000	901,000
Accrued expenses	6,149,000	2,335,000
Total current liabilities	9,814,000	3,236,000
Deferred lease obligations	1,263,000
Total liabilities	11,077,000	3,236,000
Commitments (Note 7)
Stockholders’ equity (deficit):
Preferred Stock, $0.0001 par value - 5,000,000 shares authorized at September 30, 2020 and no shares authorized at December 31, 2019; No shares issued and outstanding at September 30, 2020 or December 31, 2019
Common Stock, $0.0001 par value – 200,000,000 shares authorized at September 30, 2020 and 129,000,000 shares authorized at December 31, 2019; 23,364,851 shares issued and outstanding at September 30, 2020 and 1,204,630 shares issued and outstanding at December 31, 2019	2,000
Additional paid in-capital	247,872,000	1,428,000
Accumulated other comprehensive income		5,000
Accumulated deficit	(79,958,000)	(34,652,000)
Total stockholders’ equity (deficit)	167,916,000	(33,219,000)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 178,993,000	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

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (Unaudited) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
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	23,364,851	1,204,630
Common stock, shares outstanding	23,364,851	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	$ 0.0	$ 48.9
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	$ 0.0	$ 33.7

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development	$ 25,174	$ 3,317	$ 39,457	$ 10,941
General and administrative	3,142	1,003	6,313	3,097
Total operating expenses	28,316	4,320	45,770	14,038
Loss from operations	(28,316)	(4,320)	(45,770)	(14,038)
Other income (expense):
Interest income	64	288	306	892
Other income (expense), net	157	(3)	158	(34)
Other income (expense), net	221	285	464	858
Net loss	(28,095)	(4,035)	(45,306)	(13,180)
Other comprehensive (loss) income:
Unrealized (losses) gains on available-for-sale securities	(13)	(2)	(5)	8
Total other comprehensive (loss) income	(13)	(2)	(5)	8
Comprehensive loss	(28,108)	(4,037)	(45,311)	(13,172)
Net loss attributable to common stockholders—basic and diluted	$ (28,095)	$ (4,035)	$ (45,306)	$ (13,180)
Net loss per share attributable to common stockholders—basic and diluted	$ (1.55)	$ (3.38)	$ (6.57)	$ (11.20)
Weighted-average common shares outstanding—basic and diluted	18,101,496	1,195,309	6,893,745	1,176,769

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - 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 Series A-2 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	41				41
Exercise of stock options	34				34
Exercise of stock options, shares				35,460
Comprehensive income:
Unrealized gain (loss) on investments	2					2
Net loss	(4,971)						(4,971)
Balance at Mar. 31, 2019	(18,769)				1,130		(19,899)
Temporary equity, shares at Mar. 31, 2019		48,850,000	23,566,431
Temporary equity, balance at Mar. 31, 2019		$ 44,657	$ 33,270
Balance, shares at Mar. 31, 2019				1,170,475
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
Comprehensive income:
Net loss	(13,180)
Balance at Sep. 30, 2019	(26,795)				1,306	6	(28,107)
Temporary equity, shares at Sep. 30, 2019		48,850,000	23,566,431
Temporary equity, balance at Sep. 30, 2019		$ 44,657	$ 33,270
Balance, shares at Sep. 30, 2019				1,199,726
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
Exercise of stock options, shares	69,615
Comprehensive income:
Net loss	$ (19,700)
Balance at Dec. 31, 2019	(33,219)				1,428	5	(34,652)
Temporary equity, shares at Dec. 31, 2019		48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019		$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
Balance at Mar. 31, 2019	(18,769)				1,130		(19,899)
Temporary equity, shares at Mar. 31, 2019		48,850,000	23,566,431
Temporary equity, balance at Mar. 31, 2019		$ 44,657	$ 33,270
Balance, shares at Mar. 31, 2019				1,170,475
Stock-based compensation	40				40
Comprehensive income:
Unrealized gain (loss) on investments	8					8
Net loss	(4,173)						(4,173)
Balance at Jun. 30, 2019	(22,894)				1,170	8	(24,072)
Temporary equity, shares at Jun. 30, 2019		48,850,000	23,566,431
Temporary equity, balance at Jun. 30, 2019		$ 44,657	$ 33,270
Balance, shares at Jun. 30, 2019				1,170,475
Stock-based compensation	107				107
Exercise of stock options	29				29
Exercise of stock options, shares				29,251
Comprehensive income:
Unrealized gain (loss) on investments	(2)					(2)
Net loss	(4,035)						(4,035)
Balance at Sep. 30, 2019	(26,795)				1,306	6	(28,107)
Temporary equity, shares at Sep. 30, 2019		48,850,000	23,566,431
Temporary equity, balance at Sep. 30, 2019		$ 44,657	$ 33,270
Balance, shares at Sep. 30, 2019				1,199,726
Balance at Dec. 31, 2019	(33,219)				1,428	5	(34,652)
Temporary equity, shares at Dec. 31, 2019		48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019		$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
Stock-based compensation	129				129
Exercise of stock options	5				5
Exercise of stock options, shares				2,677
Comprehensive income:
Unrealized gain (loss) on investments	23					23
Net loss	(7,738)						(7,738)
Balance at Mar. 31, 2020	(40,800)				1,562	28	(42,390)
Temporary equity, shares at Mar. 31, 2020		48,850,000	23,566,431
Temporary equity, balance at Mar. 31, 2020		$ 44,657	$ 33,270
Balance, shares at Mar. 31, 2020				1,207,307
Balance at Dec. 31, 2019	$ (33,219)				1,428	5	(34,652)
Temporary equity, shares at Dec. 31, 2019		48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019		$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
Exercise of stock options, shares	156,370
Comprehensive income:
Net loss	$ (45,306)
Balance at Sep. 30, 2020	167,916			$ 2	247,872		(79,958)
Temporary equity, shares at Sep. 30, 2020		0	0
Balance, shares at Sep. 30, 2020				23,364,851
Balance at Mar. 31, 2020	(40,800)				1,562	28	(42,390)
Temporary equity, shares at Mar. 31, 2020		48,850,000	23,566,431
Temporary equity, balance at Mar. 31, 2020		$ 44,657	$ 33,270
Balance, shares at Mar. 31, 2020				1,207,307
Issuance of Series A-2 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
Stock-based compensation	120				120
Exercise of stock options	149				149
Exercise of stock options, shares				137,397
Comprehensive income:
Unrealized gain (loss) on investments	(15)					(15)
Net loss	(9,473)						(9,473)
Balance at Jun. 30, 2020	(50,019)				1,831	13	(51,863)
Temporary equity, shares at Jun. 30, 2020		48,850,000	47,132,862
Temporary equity, balance at Jun. 30, 2020		$ 44,657	$ 66,908
Balance, shares at Jun. 30, 2020				1,344,704
Issuance of shares to acquire in-process research and development			$ 17,759
Issuance of shares to acquire in-process research and development, 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			$ 1	129,323
Temporary equity, Conversion of convertible preferred stock into common stock, shares		(48,850,000)	(55,427,222)
Temporary equity, Conversion of convertible preferred stock into common stock		$ (44,657)	$ (84,667)
Conversion of convertible preferred stock into common stock, shares				13,953,850
Stock-based compensation	786				786
Exercise of stock options	18				18
Exercise of stock options, shares				16,297
Comprehensive income:
Unrealized gain (loss) on investments	(13)					$ (13)
Net loss	(28,095)						(28,095)
Balance at Sep. 30, 2020	$ 167,916			$ 2	$ 247,872		$ (79,958)
Temporary equity, shares at Sep. 30, 2020		0	0
Balance, shares at Sep. 30, 2020				23,364,851

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2019
Statement Of Stockholders Equity [Abstract]
Issuance costs	$ 3.9	$ 0.1	$ 0.1

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Operating activities
Net loss		$ (45,306)	$ (13,180)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	$ 42	94	58
Write-off of acquired in-process research and development		17,759
Stock-based compensation expense		1,035	188
Amortization of premiums and discounts on marketable securities		140	(41)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(4,147)	(310)
Accounts payable		1,744	(441)
Accrued expenses		3,582	236
Net cash used in operating activities		(25,099)	(13,490)
Investing activities
Purchases of marketable securities		(125,490)	(16,009)
Maturities of marketable securities		29,021	13,410
Purchases of property and equipment		(753)	(122)
Net cash used in investing activities		(97,222)	(2,721)
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		172	63
Proceeds from initial public offering, net of offering costs		116,988
Net cash provided by financing activities		150,798	22,961
Net increase in cash, cash equivalents and restricted cash		28,477	6,750
Cash, cash equivalents and restricted cash at beginning of period		31,735	35,966
Cash, cash equivalents and restricted cash at end of period	60,212	60,212	42,716
Supplemental cash flow information:
Cash and cash equivalents	59,858	59,858	42,716
Restricted cash	354	354
Cash, cash equivalents and restricted cash at end of period	$ 60,212	60,212	$ 42,716
Issuance of shares to acquire in-process research and development		17,759
Property and equipment unpaid at end of period		1,498
Deferred offering costs unpaid at end of period		1,073
Deferred lease obligations - non-cash		$ 1,263

Organization and Basis of Presentation

9 Months Ended

Sep. 30, 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 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 condensed 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 ofering 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 Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). All adjustments considered necessary for a fair presentation have been included.

The accompanying consolidated financial statements and footnotes to the financial statements have been prepared on the same basis as the most recently audited annual financial statements and, in the opinion of management, reflect all normal recurring adjustments necessary for the fair presentation of the Company’s financial position as of September 30, 2020 and the results of its operations and its cash flows for the three and nine months ended September 30, 2020 and 2019. The results for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s final prospectus for its IPO filed pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Securities Act”), with the Securities and Exchange Commission (the “SEC”) on July 24, 2020.

Liquidity

Since the Company’s incorporation in 2017 and through September 30, 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 $45.3 million in the nine months ended September 30, 2020 and $19.7 million in the year ended December 31, 2019 and had an accumulated deficit of $80.0 million as of September 30, 2020. The Company had cash, cash equivalents, and short-term and long-term investments of $171.7 million as of September 30, 2020 and $47.1 million as of December 31, 2019.

The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets, and the satisfaction of liabilities and commitments in the ordinary course of business. 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 September 30, 2020 will be sufficient to fund its operating expenses and capital expenditure requirements for at least twelve months from the date of filing this Quarterly Report on Form 10-Q. 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

9 Months Ended

Sep. 30, 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, and Inozyme Ireland Limited. All intercompany transactions and balances have been eliminated.

Summary of Significant Accounting Policies

The significant accounting policies and estimates used in the preparation of the accompanying consolidated financial statements are described in the Company’s audited consolidated financial statements for the year ended December 31, 2019 included in the Company’s final prospectus for its IPO filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on July 24, 2020. There have been no material changes in the Company’s significant accounting policies during the three months ended September 30, 2020.

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 and, for equity instruments issued prior to the completion of the Company’s IPO, stock-based compensation expense, inclusive of the measurement of fair value of equity instruments. 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.

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 trials, 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 alternative future use.

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. At the consummation of the Company’s IPO, the Company recorded $3.9 million in deferred issuance costs, which were charged against the proceeds of the IPO in the third quarter of 2020. Deferred issuance costs recorded at September 30, 2020 and December 31, 2019 were $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 loss 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.

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).

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 corporate debt securities, 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.

Recent Accounting Pronouncements

9 Months Ended

Sep. 30, 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 Accounting Standards Not Yet Adopted

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 the Company on January 1, 2022, with early adoption permitted. The Company is currently assessing the impact that adopting this standard will have on its consolidated financial statements.

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, 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, 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

9 Months Ended

Sep. 30, 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):

	September 30, 2020
Description	Maturity	Amortized Costs		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Commercial paper	1 year or less	$	69,961	$	3	$	(3	)	$	69,961
Corporate debt securities	1 year or less		3,881		—		—			3,881
U.S. Treasury securities	1 year or less		14,613		—		—			14,613
U.S. government agency debt securities	1 year or less		11,189		—		—			11,189
		$	99,644	$	3	$	(3	)	$	99,644

	December 31, 2019
Description	Maturity	Amortized Costs		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):

	September 30, 2020
Description	Maturity	Amortized Costs		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. Treasury securities	After 1 year through 5 years	$	5,093	$	—	$	—		$	5,093
U.S. government agency debt securities	After 1 year through 5 years		7,114		1		(1	)		7,114
		$	12,207	$	1	$	(1	)	$	12,207

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

Unrealized losses on long-term and short-term investments were immaterial at September 30, 2020. The Company did not have any short-term or long-term investments with unrealized losses at December 31, 2019.

The Company concluded that the net 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 September 30, 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 September 30, 2020		At December 31, 2019
Interest receivable	$	252	$	104
Prepaid insurance		2,448		47
Prepaid research studies		1,028		—
Prepaid seminars		72		—
Prepaid taxes		39		42
Prepaid other		636		135
Total	$	4,475	$	328

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

	At September 30, 2020			At December 31, 2019
Laboratory equipment and manufacturing equipment	$	334		$	308
Furniture and fixtures		155			—
Computer equipment		155			53
Leasehold improvements		2,014			47
		2,658			408
Less accumulated depreciation		(203	)		(110	)
Total	$	2,455		$	298

Depreciation expense for the three months ended September 30, 2020 and 2019 was $42 thousand and $20 thousand, respectively. Depreciation expense for the nine months ended September 30, 2020 and 2019 was $94 thousand and $58 thousand, respectively.

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

	At September 30, 2020		At December 31, 2019
Payroll and related liabilities	$	1,356	$	861
Professional fees		480		268
Research and development costs		3,271		1,086
Deferred rent		257		—
Other		785		120
Total	$	6,149	$	2,335

Fair Value Measurement

9 Months Ended

Sep. 30, 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	September 30, 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)	$	20,608	$	20,608	$	—	$	—
Commercial paper (included in cash and cash equivalents)		24,996		—		24,996		—
U.S. government agency debt securities (included in cash and cash equivalents)		5,011		—		5,011		—
Commercial paper		69,961		—		69,961		—
Corporate debt securities		3,881		—		3,881		—
U.S. Treasury securities		19,706		19,706		—		—
U.S. government agency debt securities		18,303		—		18,303		—
Total assets	$	162,466	$	40,314	$	122,152	$	—

			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 three or nine months ended September 30, 2020 or 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

9 Months Ended

Sep. 30, 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. As of September 30, 2020, the Company incurred a total of $67,500 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. The Company is not aware of any currently ongoing patent challenges.

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 $0.1 million and $0.3 million in the three and nine months ended September 30, 2020, respectively, and $0.1 million and $0.4 million in the three and nine months ended September 30, 2019, respectively.

The Company did not record any research and development expense associated with other arrangements with Yale in the three and nine months ended September 30, 2020 or in the three months ended September 30, 2019, but did record such expenses of $0.3 million in the nine months ended September 30, 2019.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

Operating 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 original lease term for this laboratory space began in July 2018 and ended in August 2020. The lease term was extended through December 2020 to facilitate the transition to the Company’s new laboratory space as described below. The Company provided security deposits to the landlords totaling $34 thousand, which is included in prepaid expenses and other current assets in the accompanying balance sheet as of September 30, 2020 and December 31, 2019.

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 July 2020 and is expected to end in the second half of 2025. 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 September 30, 2020 and December 31, 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 late 2025. 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 September 30, 2020 are as follows (dollar amounts in thousands):

Year Ending December 31,
2020 (remaining 3 months)	$	190
2021		947
2022		970
2023		994
2024		1,018
Thereafter		941
	$	5,060

Rent expense recognized on a straight-line basis over the terms of the leases for the three months ended September 30, 2020 and 2019 was $180 thousand and $110 thousand, respectively. Rent expense recognized on a straight-line basis over the terms of the leases for the nine months ended September 30, 2020 and 2019 was $436 thousand and $312 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 September 30, 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 three or nine months ended September 30, 2020 and 2019.

Convertible Preferred Stock and Stockholders' Equity

9 Months Ended

Sep. 30, 2020

Convertible Preferred Stock And Stockholders Equity [Abstract]

Convertible Preferred Stock and Stockholders' Equity

8. Convertible Preferred Stock and Stockholders’ Equity

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. 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. See Note 12 for further information about this acquisition from Alexion.

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 September 30, 2020.

There have been no dividends declared by the Company’s board of directors as of September 30, 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 September 30, 2020, 740,935 shares of common stock remain available for future issuance under the 2020 Plan.

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 grant¹.

The following table summarizes stock option activity under the Company’s equity incentive plans since December 31, 2018:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value (1)
						(in years)		(in thousands)
Outstanding at December 31, 2018		822,557		$	1.05		8.43	$	678
Granted		1,009,125			2.02
Exercised		(69,615	)		1.04
Forfeited		(126,640	)		1.51
Outstanding at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Granted		1,455,565			10.99
Exercised		(156,370	)		1.10
Forfeited		(22,747	)		1.95
Outstanding at September 30, 2020		2,911,875		$	6.32		8.94	$	58,140
Exercisable at September 30, 2020		698,826		$	1.96		7.68	$	17,006
Vested and expected to vest at September 30, 2020		2,911,875		$	6.32		8.94	$	58,140

(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 nine months ended September 30, 2020 and September 30, 2019, the Company granted 1,455,565 and 918,132 options, respectively, at a weighted-average exercise price of $10.99 and $2.02, respectively. The weighted-average grant date fair value of options granted during the nine months ended September 30, 2020 was $8.26 per share. The weighted-average grant date fair value of options granted during the nine months ended September 30, 2019 was $1.51 per share. The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2020 was $0.3 million. The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2019 was $0.1 million.

For purposes of calculating stock-based compensation expense, 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 employees using the Black-Scholes option-pricing were as follows:

	For the Three Months Ended September 30,		For the Nine Months Ended September 30,
	2020	2019	2020	2019
Risk-free interest rate range	0.38% to 0.43%	1.63% to 1.66%	0.38% to 0.47%	1.63% to 2.51%
Dividend yield	0%	0%	0%	0%
Expected term of options (years)	6.78	6.78	6.78	6.78
Volatility rate range	86.54% to 86.88%	85.02%	86.54% to 99.85%	85.02%

The total compensation cost recognized in the statements of operations associated with all the stock-based compensation awards granted by the Company is as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development	$	295	$	57	$	422	$	110
General and administrative		491		50		613		78
Total	$	786	$	107	$	1,035	$	188

The total unrecognized compensation cost related to outstanding employee awards as of September 30, 2020 was $12.6 million, and is expected to be recognized over a weighted-average period of 2.7 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 September 30, 2020, no shares have been purchased by employees under the ESPP.

Net Loss per Share

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

Earnings per Share

9. Net Loss per Share

Net Loss per Share Attributable to Common Stockholders

For purposes of the diluted net loss per share calculation, stock options, 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 from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Series A Convertible Preferred Stock (as converted to common stock)		—		6,536,856		—		6,536,856
Series A-2 Convertible Preferred Stock (as converted to common stock)		—		3,153,537		—		3,153,537
Options to purchase common stock		2,911,875		1,549,338		2,911,875		1,549,338
		2,911,875		11,239,731		2,911,875		11,239,731

Employee Benefit Plans

9 Months Ended

Sep. 30, 2020

Compensation And Retirement Disclosure [Abstract]

Employee Benefit Plans

10. 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. Employees can designate the investment of their 401(k) accounts into several mutual funds. To date, the Company has not made any employer contributions to the plan.

Related Party Transactions

9 Months Ended

Sep. 30, 2020

Related Party Transactions

11. Related Party Transactions

For the three and nine months ended September 30, 2019, the Company made payments of $34 thousand and $101 thousand 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 September 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.

Acquisitions

9 Months Ended

Sep. 30, 2020

Business Combinations [Abstract]

Acquisitions

12. Acquisitions

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 as the Company will use these assets in research and development activities and believes they have no alternative future uses. Accordingly, the Company expensed the entire value of the assets acquired from Alexion and related acquisition costs as of the acquisition date as a component of research and development expenses in the three and nine months ended September 30, 2020.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Basis of Presentation

Principles of Consolidation

Summary of Significant Accounting Policies

Use of Estimates

Accrued Research and Development Costs

Research and Development Costs

Deferred Issuance Costs

Net Loss Per Share

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).

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.

Recently Issued Accounting Standards Not Yet Adopted

Balance Sheet Details (Tables)

9 Months Ended

Sep. 30, 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):

	September 30, 2020
Description	Maturity	Amortized Costs		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Commercial paper	1 year or less	$	69,961	$	3	$	(3	)	$	69,961
Corporate debt securities	1 year or less		3,881		—		—			3,881
U.S. Treasury securities	1 year or less		14,613		—		—			14,613
U.S. government agency debt securities	1 year or less		11,189		—		—			11,189
		$	99,644	$	3	$	(3	)	$	99,644

	December 31, 2019
Description	Maturity	Amortized Costs		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):

	September 30, 2020
Description	Maturity	Amortized Costs		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. Treasury securities	After 1 year through 5 years	$	5,093	$	—	$	—		$	5,093
U.S. government agency debt securities	After 1 year through 5 years		7,114		1		(1	)		7,114
		$	12,207	$	1	$	(1	)	$	12,207

Schedule of Prepaid Expenses and Other Current Assets

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

	At September 30, 2020		At December 31, 2019
Interest receivable	$	252	$	104
Prepaid insurance		2,448		47
Prepaid research studies		1,028		—
Prepaid seminars		72		—
Prepaid taxes		39		42
Prepaid other		636		135
Total	$	4,475	$	328

Schedule of Property and Equipment

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

	At September 30, 2020			At December 31, 2019
Laboratory equipment and manufacturing equipment	$	334		$	308
Furniture and fixtures		155			—
Computer equipment		155			53
Leasehold improvements		2,014			47
		2,658			408
Less accumulated depreciation		(203	)		(110	)
Total	$	2,455		$	298

Schedule of Accrued Expenses

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

	At September 30, 2020		At December 31, 2019
Payroll and related liabilities	$	1,356	$	861
Professional fees		480		268
Research and development costs		3,271		1,086
Deferred rent		257		—
Other		785		120
Total	$	6,149	$	2,335

Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value

			Fair Value Measurements at Reporting Date Using
Description	September 30, 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)	$	20,608	$	20,608	$	—	$	—
Commercial paper (included in cash and cash equivalents)		24,996		—		24,996		—
U.S. government agency debt securities (included in cash and cash equivalents)		5,011		—		5,011		—
Commercial paper		69,961		—		69,961		—
Corporate debt securities		3,881		—		3,881		—
U.S. Treasury securities		19,706		19,706		—		—
U.S. government agency debt securities		18,303		—		18,303		—
Total assets	$	162,466	$	40,314	$	122,152	$	—

			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)

9 Months Ended

Sep. 30, 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 September 30, 2020 are as follows (dollar amounts in thousands):

Year Ending December 31,
2020 (remaining 3 months)	$	190
2021		947
2022		970
2023		994
2024		1,018
Thereafter		941
	$	5,060

Convertible Preferred Stock and Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2020

Convertible Preferred Stock And Stockholders Equity [Abstract]

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, 2018:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value (1)
						(in years)		(in thousands)
Outstanding at December 31, 2018		822,557		$	1.05		8.43	$	678
Granted		1,009,125			2.02
Exercised		(69,615	)		1.04
Forfeited		(126,640	)		1.51
Outstanding at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Granted		1,455,565			10.99
Exercised		(156,370	)		1.10
Forfeited		(22,747	)		1.95
Outstanding at September 30, 2020		2,911,875		$	6.32		8.94	$	58,140
Exercisable at September 30, 2020		698,826		$	1.96		7.68	$	17,006
Vested and expected to vest at September 30, 2020		2,911,875		$	6.32		8.94	$	58,140

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

	For the Three Months Ended September 30,		For the Nine Months Ended September 30,
	2020	2019	2020	2019
Risk-free interest rate range	0.38% to 0.43%	1.63% to 1.66%	0.38% to 0.47%	1.63% to 2.51%
Dividend yield	0%	0%	0%	0%
Expected term of options (years)	6.78	6.78	6.78	6.78
Volatility rate range	86.54% to 86.88%	85.02%	86.54% to 99.85%	85.02%

Summary of Total Compensation Cost Recognized in Statements of Operations

The total compensation cost recognized in the statements of operations associated with all the stock-based compensation awards granted by the Company is as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development	$	295	$	57	$	422	$	110
General and administrative		491		50		613		78
Total	$	786	$	107	$	1,035	$	188

Net Loss per Share (Tables)

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Series A Convertible Preferred Stock (as converted to common stock)		—		6,536,856		—		6,536,856
Series A-2 Convertible Preferred Stock (as converted to common stock)		—		3,153,537		—		3,153,537
Options to purchase common stock		2,911,875		1,549,338		2,911,875		1,549,338
		2,911,875		11,239,731		2,911,875		11,239,731

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands				3 Months Ended						9 Months Ended		12 Months Ended
	Jul. 30, 2020 USD ($) shares	Jul. 28, 2020 $ / shares shares	Jul. 17, 2020	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
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
Net loss \| $				$ 28,095	$ 9,473	$ 7,738	$ 4,035	$ 4,173	$ 4,971	$ 45,306	$ 13,180	$ 19,700
Accumulated deficit \| $				79,958						79,958		34,652
Cash and cash equivalents and short term and long term investments \| $				$ 171,700						$ 171,700		$ 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) - USD ($)	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Deferred issuance costs	$ 0	$ 100,000
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
IPO
Summary Of Significant Accounting Policies [Line Items]
Deferred issuance costs	$ 3,900,000

Balance Sheet - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Costs	$ 99,644	$ 15,522
Gross Unrealized Gains	3	5
Gross Unrealized Losses	(3)
Estimated Fair Value	$ 99,644	$ 15,527
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Costs	$ 69,961	$ 10,903
Gross Unrealized Gains	3	3
Gross Unrealized Losses	(3)
Estimated Fair Value	$ 69,961	$ 10,906
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Costs	$ 3,881	$ 3,370
Gross Unrealized Gains		1
Estimated Fair Value	$ 3,881	$ 3,371
U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Costs	$ 14,613	$ 1,249
Gross Unrealized Gains		1
Estimated Fair Value	$ 14,613	$ 1,250
U.S. Government Agency Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less
Amortized Costs	$ 11,189
Estimated Fair Value	$ 11,189

Balance Sheet - Schedule of Long-Term Investments (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Costs	$ 99,644	$ 15,522
Gross Unrealized Gains	3	5
Gross Unrealized Losses	(3)
Estimated Fair Value	$ 99,644	$ 15,527
U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Costs	$ 14,613	$ 1,249
Gross Unrealized Gains		1
Estimated Fair Value	$ 14,613	$ 1,250
U.S. Government Agency Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less
Amortized Costs	$ 11,189
Estimated Fair Value	11,189
Long Term Investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Costs	12,207
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)
Estimated Fair Value	$ 12,207
Long Term Investments \| U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	After 1 year through 5 years
Amortized Costs	$ 5,093
Estimated Fair Value	$ 5,093
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 Costs	$ 7,114
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)
Estimated Fair Value	$ 7,114

Balance Sheet Details - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Long-term investments	$ 12,207,000		$ 12,207,000		$ 0
Short-term or long term investments with unrealized losses					$ 0
Depreciation expense	$ 42,000	$ 20,000	$ 94,000	$ 58,000

Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Interest receivable	$ 252	$ 104
Prepaid insurance	2,448	47
Prepaid research studies	1,028
Prepaid seminars	72
Prepaid taxes	39	42
Prepaid other	636	135
Total	$ 4,475	$ 328

Balance Sheet Details - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,658	$ 408
Less accumulated depreciation	(203)	(110)
Total	2,455	298
Laboratory Equipment and Manufacturing Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	334	308
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	155
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	155	53
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,014	$ 47

Balance Sheet Details - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Payroll and related liabilities	$ 1,356	$ 861
Professional fees	480	268
Research and development costs	3,271	1,086
Deferred rent	257
Other	785	120
Total	$ 6,149	$ 2,335

Fair Value Measurement - Summary of Financial Assets Measured at Fair Value (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	$ 162,466	$ 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	20,608	11,709
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure	24,996	1,992
Assets fair value disclosure	69,961	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	40,314	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	20,608	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	122,152	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	24,996	1,992
Assets fair value disclosure	69,961	10,906
U.S. Government Agency Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure	5,011
Assets fair value disclosure	18,303
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]
Cash and cash equivalents fair value disclosure	5,011
Assets fair value disclosure	18,303
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	3,881	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	3,881	3,371
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	19,706	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	$ 19,706	$ 1,250

Fair Value Measurement - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair value assets level 1 to level 2 transfers amount	$ 0	$ 0	$ 0	$ 0
Fair value assets level 2 to level 1 transfers amount	0	0	0	0
Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers into level 3	0	0	0	0
Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers out of level 3	$ 0	$ 0	$ 0	$ 0

License and Sponsored Research Agreements - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 25,174,000	$ 3,317,000	$ 39,457,000	$ 10,941,000
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		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		100,000	100,000	300,000	400,000
Yale \| Other Arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 0	$ 0	0	$ 300,000
Yale \| License
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maintenance fees				$ 67,500

Commitments and Contingencies - Additional Information (Details)	1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2020 ft²	Dec. 31, 2019 USD ($) ft²	Jul. 31, 2018 ft²	Mar. 31, 2018 ft²	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2018
Lessee Lease Description [Line Items]
Rent expense					$ 180,000	$ 110,000	$ 436,000	$ 312,000
Costs related to legal proceedings					0	$ 0	0	$ 0
Prepaid Expenses and Other Current Assets
Lessee Lease Description [Line Items]
Security deposits		$ 34,000			34,000		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
Lessee operating lease commenced month and year		2020-07		2018-06
Lessee operating lease expiration month and year				2020-04
Lessee operating lease expiration year									2025
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
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			2020-08
Lessee operating lease extension month and year			2020-12
Lessee operating lease expiration year	2025
Square feet under lease \| ft²	6,244

Commitments and Contingencies - Schedule of Future Minimum Commitments Under Non-Cancellable Leases (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020 (remaining 3 months)	$ 190
2021	947
2022	970
2023	994
2024	1,018
Thereafter	941
Operating lease liability	$ 5,060

Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details) - USD ($)		1 Months Ended			9 Months Ended		12 Months Ended
	Jul. 23, 2020	Jun. 30, 2020	Mar. 31, 2019	Nov. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jul. 31, 2020	Jul. 28, 2020	Jul. 17, 2020	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued			16,083,916	7,482,515
Shares issued, price per share		$ 1.43	$ 1.43	$ 1.43
Net proceeds from issuance of shares		$ 33,600,000	$ 22,900,000	$ 10,400,000	$ 33,638,000	$ 22,898,000
Shares available for issuance to investors			23,566,431
Shares available for issuance, price per share			$ 1.43
Additional shares issued		23,566,431
Preferred stock, shares outstanding					0		0		0
Number of common stock issued upon conversion									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					$ 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 September 30, 2020, 740,935 shares of common stock remain available for future issuance under the 2020 Plan.
Granted options					1,455,565	918,132	1,009,125
Weighted-average exercise price of options granted					$ 10.99	$ 2.02	$ 2.02
Weighted-average grant date fair value of options granted					$ 8.26	$ 1.51
Aggregate intrinsic value of stock options exercised					$ 300,000	$ 100,000
Total unrecognized compensation cost related to outstanding employee awards					$ 12,600,000
Total unrecognized compensation cost related to outstanding employee awards, expected to be recognized over a weighted-average period					2 years 8 months 12 days
Share based compensation options to purchase number of common stock					2,911,875		1,635,427				822,557
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance								2,730,496
Number of awards available for issuance										0
Maximum common stock granted, under 2020 plan										0
2020 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	1,588,315				740,935
Number of common stock reserved for issuance increase percentage on stock outstanding	4.00%
2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	426,065
2020 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
IPO
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock, shares outstanding									104,277,222
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued				47,132,862
Maximum \| 2020 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of awards available for issuance					1,588,315
Maximum common stock granted, under 2020 plan					1,588,315
Series A-2 Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued					0		23,566,431
Convertible preferred stock, shares authorized					0		47,132,862
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
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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 Stock Option Activity Under Equity Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Convertible Preferred Stock And Stockholders Equity [Abstract]
Options Outstanding, Beginning Balance	1,635,427	822,557	822,557
Options Outstanding, Granted	1,455,565	918,132	1,009,125
Options Outstanding, Exercised	(156,370)		(69,615)
Options Outstanding, Forfeited	(22,747)		(126,640)
Options Outstanding, Ending Balance	2,911,875		1,635,427	822,557
Options Outstanding, Exercisable	698,826
Options Outstanding, Vested and expected to vest	2,911,875
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 1.64	$ 1.05	$ 1.05
Weighted Average Exercise Price, Granted	10.99	$ 2.02	2.02
Weighted Average Exercise Price, Exercised	1.10		1.04
Weighted Average Exercise Price, Forfeited	1.95		1.51
Weighted Average Exercise Price, Outstanding, Ending Balance	6.32		$ 1.64	$ 1.05
Weighted Average Exercise Price, Exercisable	1.96
Weighted Average Exercise Price, Vested and expected to vest	$ 6.32
Weighted Average Remaining Contractual Term (in years), Outstanding	8 years 11 months 8 days		8 years 9 months 21 days	8 years 5 months 4 days
Weighted Average Remaining Contractual Term (in years), Exercisable	7 years 8 months 4 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	8 years 11 months 8 days
Aggregate Intrinsic Value, Outstanding	$ 58,140		$ 668	$ 678
Aggregate Intrinsic Value, Exercisable	17,006
Aggregate Intrinsic Value, Vested and expected to vest	$ 58,140

Convertible Preferred Stock and Stockholders' Equity - Summary of Assumptions Used to Value Stock Options Granted to Employees using Black-Scholes Option-Pricing (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Convertible Preferred Stock And Stockholders Equity [Abstract]
Risk-free interest rate range, minimum	0.38%	1.63%	0.38%	1.63%
Risk-free interest rate range, maximum	0.43%	1.66%	0.47%	2.51%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term of options (years)	6 years 9 months 10 days	6 years 9 months 10 days	6 years 9 months 10 days	6 years 9 months 10 days
Volatility rate range		85.02%		85.02%
Volatility rate range, minimum	86.54%		86.54%
Volatility rate range, maximum	86.88%		99.85%

Convertible Preferred Stock and Stockholders' Equity - Summary of Total Compensation Cost Recognized in Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total	$ 786	$ 107	$ 1,035	$ 188
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total	295	57	422	110
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total	$ 491	$ 50	$ 613	$ 78

Net Loss per Share - Schedule of Potential Dilutive Securities from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	2,911,875	11,239,731	2,911,875	11,239,731
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		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		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	2,911,875	1,549,338	2,911,875	1,549,338

Employee Benefit Plans - Additional Information (Details)	9 Months Ended
	Sep. 30, 2020 USD ($)
Compensation And Retirement Disclosure [Abstract]
Employer contribution amount	$ 0

Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended	5 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2019	May 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Number of shares granted, option to purchase			1,455,565	918,132	1,009,125
Weighted-average exercise price of options granted			$ 10.99	$ 2.02	$ 2.02
Director
Related Party Transaction [Line Items]
Scientific consulting and other expenses	$ 34,000	$ 56,000		$ 101,000
Number of shares granted, option to purchase				66,907
Weighted-average exercise price of options granted				$ 2.02
Due to related party			$ 0

Acquisitions - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Preferred stock, issued		0	0
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]
Preferred stock, issued	8,294,360