0001564590-20-042521 | 10-Q | XBRL Viewer

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2020	Aug. 31, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
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	No
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		23,364,851

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 50,863	$ 31,605
Short-term investments	13,004	15,527
Prepaid expenses and other current assets	793	328
Total current assets	64,660	47,460
Property and equipment, net	846	298
Restricted cash	355	130
Deferred issuance costs	2,650	56
Total assets	68,511	47,944
Current liabilities:
Accounts payable	1,399	901
Accrued expenses	5,328	2,335
Total current liabilities	6,727	3,236
Deferred lease incentive	238
Total liabilities	6,965	3,236
Commitments (Note 7)
Convertible preferred stock	111,565	77,927
Stockholders’ (deficit) equity:
Additional paid in-capital	1,831	1,428
Accumulated other comprehensive income	13	5
Accumulated deficit	(51,863)	(34,652)
Total stockholders’ (deficit) equity	(50,019)	(33,219)
Total liabilities, convertible preferred stock and stockholders’ (deficit) equity	68,511	47,944
Series A Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	44,657	44,657
Series A-2 Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	$ 66,908	$ 33,270

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Convertible preferred stock, shares authorized	95,982,862	95,982,862
Convertible preferred stock, shares issued	95,982,862	72,416,431
Convertible preferred stock, shares outstanding	95,982,862	72,416,431
Convertible preferred stock, liquidation preference	$ 116,250	$ 82,550
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	129,000,000	129,000,000
Common stock, shares issued	1,344,704	1,204,630
Common stock, shares outstanding	1,344,704	1,204,630
Series A Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	48,850,000	48,850,000
Convertible preferred stock, shares issued	48,850,000	48,850,000
Convertible preferred stock, shares outstanding	48,850,000	48,850,000
Convertible preferred stock, liquidation preference	$ 48,850	$ 48,850
Series A-2 Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	47,132,862	47,132,862
Convertible preferred stock, shares issued	47,132,862	23,566,431
Convertible preferred stock, shares outstanding	47,132,862	23,566,431
Convertible preferred stock, liquidation preference	$ 67,400	$ 33,700

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 7,877	$ 3,489	$ 14,283	$ 7,623
General and administrative	1,671	1,064	3,171	2,094
Total operating expenses	9,548	4,553	17,454	9,717
Loss from operations	(9,548)	(4,553)	(17,454)	(9,717)
Other income (expense):
Interest income	71	394	242	604
Other income (expense), net	4	(14)	1	(31)
Other income (expense), net	75	380	243	573
Net loss	(9,473)	(4,173)	(17,211)	(9,144)
Other comprehensive (loss) income:
Unrealized (losses) gains on available-for-sale securities	(15)	10	8	12
Total other comprehensive (loss) income	(15)	10	8	12
Comprehensive loss	(9,488)	(4,163)	(17,203)	(9,132)
Net loss attributable to common stockholders—basic and diluted	$ (9,473)	$ (4,173)	$ (17,211)	$ (9,144)
Net loss per share attributable to common stockholders—basic and diluted	$ (7.57)	$ (3.57)	$ (14.01)	$ (7.83)
Weighted-average common shares outstanding—basic and diluted	1,251,244	1,170,480	1,228,296	1,167,346

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' (DEFICIT) EQUITY (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	(9,144)
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
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	72,416,431	48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019	$ 77,927	$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
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
Balance at Dec. 31, 2019	$ (33,219)				1,428	5	(34,652)
Temporary equity, shares at Dec. 31, 2019	72,416,431	48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019	$ 77,927	$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
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	72,416,431	48,850,000	23,566,431
Temporary equity, balance at Dec. 31, 2019	$ 77,927	$ 44,657	$ 33,270
Balance, shares at Dec. 31, 2019				1,204,630
Exercise of stock options, shares	140,073
Comprehensive income:
Net loss	$ (17,211)
Balance at Jun. 30, 2020	$ (50,019)				1,831	13	(51,863)
Temporary equity, shares at Jun. 30, 2020	95,982,862	48,850,000	47,132,862
Temporary equity, balance at Jun. 30, 2020	$ 111,565	$ 44,657	$ 66,908
Balance, shares at Jun. 30, 2020				1,344,704
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	95,982,862	48,850,000	47,132,862
Temporary equity, balance at Jun. 30, 2020	$ 111,565	$ 44,657	$ 66,908
Balance, shares at Jun. 30, 2020				1,344,704

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net loss		$ (17,211)	$ (9,144)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	$ 26	51	38
Stock-based compensation expense		249	81
Accretion on marketable securities		(81)	(22)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(465)	(337)
Accounts payable		454	(393)
Accrued expenses		2,105	(396)
Net cash used in operating activities		(14,898)	(10,173)
Investing activities
Purchases of marketable securities		(18,908)	(12,771)
Maturities of marketable securities		21,520	9,225
Purchases of property and equipment		(168)	(43)
Net cash provided by (used in) investing activities		2,444	(3,589)
Financing activities
Proceeds from issuance of Series A-2 Convertible Preferred Stock, net of issuance costs		33,638	22,898
Payment of initial public offering costs		(1,855)
Proceeds from exercise of stock options		154	34
Net cash provided by financing activities		31,937	22,932
Net increase in cash, cash equivalents and restricted cash		19,483	9,170
Cash, cash equivalents and restricted cash at beginning of period		31,735	35,966
Cash, cash equivalents and restricted cash at end of period	51,218	51,218	45,136
Supplemental cash flow information:
Cash and cash equivalents	50,863	50,863	45,136
Restricted cash	355	355
Cash, cash equivalents and restricted cash at end of period	$ 51,218	51,218	$ 45,136
Property and equipment unpaid at end of period		431
Deferred offering costs unpaid at end of period		738
Deferred lease incentive - non-cash		$ 238

Organization and Basis of Presentation

6 Months Ended

Jun. 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 will receive 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 $116.5 million, after deducting underwriting discounts and commissions and estimated 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 June 30, 2020 and the results of its operations and its cash flows for the three and six months ended June 30, 2020 and 2019. The results for the three and six months ended June 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 June 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 $17.2 million in the six months ended June 30, 2020 and $19.7 million in the year ended December 31, 2019 and had an accumulated deficit of $51.9 million as of June 30, 2020 and $34.7 million as of December 31, 2019. The Company had cash and cash equivalents of $50.9 million and $31.6 million, and short-term investments of $13.0 million and $15.5 million as of June 30, 2020 and December 31, 2019, respectively.

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 most recently, with proceeds from the 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 and cash equivalents as of June 30, 2020, together with the net proceeds of approximately $116.5 million from the IPO of the Company’s common stock completed in July 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

6 Months Ended

Jun. 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 June 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 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.

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. The Company recorded deferred issuance costs at June 30, 2020 and December 31, 2019 of $2.7 million 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, restricted stock units 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 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 short-term investments are comprised of corporate debt securities, U.S. Treasury and agency 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.

Balance Sheet Details

6 Months Ended

Jun. 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):

	June 30, 2020
Description	Maturity	Amortized Costs		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Commercial paper	1 year or less	$	9,100	$	11	$	(1	)	$	9,110
Corporate debt securities	1 year or less		2,888		—		—			2,888
U.S. Treasury securities	1 year or less		1,003		3		—			1,006
		$	12,991	$	14	$	(1	)	$	13,004

	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

Total short-term investments at June 30, 2020 with unrealized losses were as follows (dollar amounts in thousands):

	June 30, 2020
Description	Maturity	Fair Value		Unrealized Losses
Commercial paper	1 year or less	$	2,611	$	(1	)
		$	2,611	$	(1	)

The Company did not have any short-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 June 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 June 30, 2020		At December 31, 2019
Interest receivable	$	82	$	104
Prepaid research studies		285		—
Prepaid seminars		122		—
Prepaid insurance		9		47
Prepaid taxes		39		42
Prepaid other		256		135
Total	$	793	$	328

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

	At June 30, 2020			At December 31, 2019
Laboratory equipment and manufacturing equipment	$	312		$	308
Furniture and fixtures		98			—
Computer equipment		92			53
Leasehold improvements		505			47
		1,007			408
Less accumulated depreciation		(161	)		(110	)
Total	$	846		$	298

Depreciation expense for the three months ended June 30, 2020 and 2019 was $26 thousand and $19 thousand, respectively. Depreciation expense for the six months ended June 30, 2020 and 2019 was $51 thousand and $38 thousand, respectively.

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

	At June 30, 2020		At December 31, 2019
Payroll and related liabilities	$	736	$	861
Professional fees		1,110		268
Research and development costs		2,697		1,086
Other		785		120
Total	$	5,328	$	2,335

Fair Value Measurement

6 Months Ended

Jun. 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	June 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)	$	30,305	$	30,305	$	—	$	—
Commercial paper (included in cash and cash equivalents)		4,498		—		4,498		—
Corporate debt securities (included in cash and cash equivalents)		4,800		—		4,800		—
Commercial paper		9,110				9,110
Corporate debt securities		2,888				2,888
U.S. Treasury securities		1,006		1,006
Total assets	$	52,607	$	31,311	$	21,296	$	—

			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 six months ended June 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

Commitments and Contingencies

6 Months Ended

Jun. 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 lease term for this laboratory space began in July 2018 and ends in August 2020. 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 June 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 sheet as of June 30, 2020 and December 31, 2019.

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 will begin following the substantial completion of the construction work which is anticipated in late 2020 and ends in late 2025.

Total future minimum commitments under non-cancellable leases as of June 30, 2020 are as follows (dollar amounts in thousands):

Year Ending December 31,
2020 (remaining 6 months)	$	258
2021		950
2022		973
2023		997
2024		1,022
Thereafter		786
	$	4,986

Rent expense recognized on a straight-line basis over the terms of the leases for the three months ended June 30, 2020 and 2019 was $117 thousand and $101 thousand, respectively. Rent expense recognized on a straight-line basis over the terms of the leases for the six months ended June 30, 2020 and 2019 was $255 thousand and $202 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 June 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 six months ended June 30, 2020 and 2019.

Convertible Preferred Stock and Stockholders' Equity

6 Months Ended

Jun. 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

The authorized, issued, outstanding and preferences of the Company’s Series A Convertible Preferred Stock and Series A-2 Convertible Preferred Stock as of June 30, 2020 and December 31, 2019 were as follows (dollar amounts in thousands):

	June 30, 2020
Description	Preferred stock authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Convertible Preferred Stock		48,850,000		48,850,000	$	44,657	$	48,850		6,536,856
Series A-2 Convertible Preferred Stock		47,132,862		47,132,862		66,908		67,400		6,307,084
		95,982,862		95,982,862	$	111,565	$	116,250		12,843,940

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

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.

There have been no dividends declared by the Company’s board of directors as of June 30, 2020.

2017 Equity Incentive Plan

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 allows 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.

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 stock options.

As of June 30, 2020 and December 31, 2019, the maximum number of shares of common stock reserved for issuance under the 2017 Plan was 2,730,496. As of June 30, 2020 and December 31, 2019, 426,065 and 1,025,425 shares of common stock remain available for future issuance under the 2017 Plan, respectively.

The following table summarizes stock option activity under the 2017 Plan since December 31, 2018:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(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		608,185			2.77
Exercised		(140,073	)		1.11
Forfeited		(20,321	)		1.95
Outstanding at June 30, 2020		2,083,218		$	1.98		8.81	$	1,641
Exercisable at December 31, 2019		521,327		$	1.15		7.91	$	452
Vested and expected to vest at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Exercisable at June 30, 2020		544,379		$	1.29		7.62	$	806
Vested and expected to vest at June 30, 2020		2,083,218		$	1.98		8.81	$	1,641

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 six-month period ended June 30, 2019, the Company granted 681,950 options, at a weighted-average exercise price of $2.02. The weighted-average grant date fair values of options granted during each of the three and six months ended June 30, 2020 were $2.25 per share. The weighted-average grant date fair values of options granted during each of the three and six months ended June 30, 2019 were $1.50 per share. The aggregate intrinsic value of stock options exercised during each of the three and six months ended June 30, 2020 was $0.2 million. The aggregate intrinsic value of stock options exercised during each of the three and six months ended June 30, 2019 was $0.1 million.

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

	Three Months Ended June 30.		Six Months Ended June 30,
	2020	2019	2020	2019
Risk-free interest rate range	0.46%	1.84%	0.46%	1.84% 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	99.85%	85.02%	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 June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	62	$	26	$	127	$	53
General and administrative		58		14		122		28
Total	$	120	$	40	$	249	$	81

The total unrecognized compensation cost related to outstanding employee awards as of June 30, 2020 was $2.5 million, and is expected to be recognized over a weighted-average period of 2.8 years.

Subsequent Events

6 Months Ended

Jun. 30, 2020

Subsequent Events [Abstract]

Subsequent Events

12. Subsequent Events

(a) Acquisition of intellectual property

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 Alexion’s 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 will expense the assets acquired from Alexion as of the acquisition date because the Company will use them in research and development activities and believes they have no alternative future uses.

(b) Increase in Authorized Series A-2 Convertible Preferred Stock

On July 17, 2020, the Company increased the number of authorized shares of Series A-2 Convertible Preferred Stock from 47,132,862 to 55,427,222.

On July 17, 2020, the Company increased the number of authorized shares of common stock from 129,000,000 to 138,000,000.

(d) 2020 Stock Incentive Plan

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, nonstatutory 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 shares of common stock remaining available for issuance under the 2017 Plan as of July 23, 2020. The number of shares reserved 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.

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.

(e) 2020 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.

(f) Automatic Conversion Waiver and Reverse Stock Split

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

(g) Initial Public Offering

On July 28, 2020, the Company completed an 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 approximately $116.5 million, after deducting underwriting discounts and commissions and estimated 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.

(h) Changes to Authorized Common Stock and Preferred Stock

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.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 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

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 (Tables)

6 Months Ended

Jun. 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):

	June 30, 2020
Description	Maturity	Amortized Costs		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Commercial paper	1 year or less	$	9,100	$	11	$	(1	)	$	9,110
Corporate debt securities	1 year or less		2,888		—		—			2,888
U.S. Treasury securities	1 year or less		1,003		3		—			1,006
		$	12,991	$	14	$	(1	)	$	13,004

	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 Short-Term Investments with Unrealized Losses

Total short-term investments at June 30, 2020 with unrealized losses were as follows (dollar amounts in thousands):

	June 30, 2020
Description	Maturity	Fair Value		Unrealized Losses
Commercial paper	1 year or less	$	2,611	$	(1	)
		$	2,611	$	(1	)

Schedule of Prepaid Expenses and Other Current Assets

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

	At June 30, 2020		At December 31, 2019
Interest receivable	$	82	$	104
Prepaid research studies		285		—
Prepaid seminars		122		—
Prepaid insurance		9		47
Prepaid taxes		39		42
Prepaid other		256		135
Total	$	793	$	328

Schedule of Property and Equipment

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

	At June 30, 2020			At December 31, 2019
Laboratory equipment and manufacturing equipment	$	312		$	308
Furniture and fixtures		98			—
Computer equipment		92			53
Leasehold improvements		505			47
		1,007			408
Less accumulated depreciation		(161	)		(110	)
Total	$	846		$	298

Schedule of Accrued Expenses

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

	At June 30, 2020		At December 31, 2019
Payroll and related liabilities	$	736	$	861
Professional fees		1,110		268
Research and development costs		2,697		1,086
Other		785		120
Total	$	5,328	$	2,335

Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value

			Fair Value Measurements at Reporting Date Using
Description	June 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)	$	30,305	$	30,305	$	—	$	—
Commercial paper (included in cash and cash equivalents)		4,498		—		4,498		—
Corporate debt securities (included in cash and cash equivalents)		4,800		—		4,800		—
Commercial paper		9,110				9,110
Corporate debt securities		2,888				2,888
U.S. Treasury securities		1,006		1,006
Total assets	$	52,607	$	31,311	$	21,296	$	—

			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	$	—

Convertible Preferred Stock and Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2020

Convertible Preferred Stock And Stockholders Equity [Abstract]

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

	June 30, 2020
Description	Preferred stock authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Convertible Preferred Stock		48,850,000		48,850,000	$	44,657	$	48,850		6,536,856
Series A-2 Convertible Preferred Stock		47,132,862		47,132,862		66,908		67,400		6,307,084
		95,982,862		95,982,862	$	111,565	$	116,250		12,843,940

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

Summary of Stock Option Activity Under 2017 Plan

The following table summarizes stock option activity under the 2017 Plan since December 31, 2018:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(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		608,185			2.77
Exercised		(140,073	)		1.11
Forfeited		(20,321	)		1.95
Outstanding at June 30, 2020		2,083,218		$	1.98		8.81	$	1,641
Exercisable at December 31, 2019		521,327		$	1.15		7.91	$	452
Vested and expected to vest at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Exercisable at June 30, 2020		544,379		$	1.29		7.62	$	806
Vested and expected to vest at June 30, 2020		2,083,218		$	1.98		8.81	$	1,641

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

	Three Months Ended June 30.		Six Months Ended June 30,
	2020	2019	2020	2019
Risk-free interest rate range	0.46%	1.84%	0.46%	1.84% 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	99.85%	85.02%	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 June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	62	$	26	$	127	$	53
General and administrative		58		14		122		28
Total	$	120	$	40	$	249	$	81

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands				3 Months Ended				6 Months Ended		12 Months Ended
	Jul. 30, 2020 USD ($) shares	Jul. 28, 2020 $ / shares shares	Jul. 17, 2020	Jun. 30, 2020 USD ($) shares	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) shares
Organization And Basis Of Presentation [Line Items]
Number of common stock issued upon conversion \| shares				12,843,940				12,843,940		9,690,393
Net loss \| $				$ 9,473	$ 7,738	$ 4,173	$ 4,971	$ 17,211	$ 9,144	$ 19,700
Accumulated deficit \| $				51,863				51,863		34,652
Cash and cash equivalents \| $				50,863		$ 45,136		50,863	$ 45,136	31,605
Short-term investments \| $				$ 13,004				$ 13,004		$ 15,527
Subsequent Event
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 \| $	$ 116,500
Number of outstanding preferred stock converted \| shares		104,277,222
Number of common stock issued upon conversion \| shares		13,953,850
Subsequent Event \| IPO
Organization And Basis Of Presentation [Line Items]
Shares issued \| shares		7,000,000
Shares issued, price per share \| $ / shares		$ 16.00
Subsequent Event \| Underwriters
Organization And Basis Of Presentation [Line Items]
Shares issued \| shares	1,050,000

Commitments and Contingencies - Additional Information (Details)	1 Months Ended				3 Months Ended		6 Months Ended		12 Months Ended
	May 31, 2020 ft²	Dec. 31, 2019 USD ($) ft²	Jul. 31, 2018 ft²	Mar. 31, 2018 ft²	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018
Lessee Lease Description [Line Items]
Rent expense					$ 117,000	$ 101,000	$ 255,000	$ 202,000
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			2018-07
Lessee operating lease expiration month and year			2020-08
Square feet under lease \| ft²	6,244
Lessee operating lease lease not yet commenced commencement year	2020
Lessee operating lease lease not yet commenced expiration year	2025

Convertible Preferred Stock and Stockholders' Equity - Summary of Authorized, Issued, Outstanding and Preferences of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Nov. 30, 2018
Temporary Equity [Line Items]
Preferred stock authorized	95,982,862		95,982,862
Preferred stock issued	95,982,862		72,416,431
Preferred stock outstanding	95,982,862		72,416,431
Carrying value	$ 111,565		$ 77,927
Liquidation preference	$ 116,250		$ 82,550
Common stock issuable upon conversion	12,843,940		9,690,393
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized	48,850,000		48,850,000
Preferred stock issued	48,850,000		48,850,000
Preferred stock outstanding	48,850,000	48,850,000	48,850,000	48,850,000	48,850,000	48,850,000
Carrying value	$ 44,657	$ 44,657	$ 44,657	$ 44,657	$ 44,657	$ 44,657
Liquidation preference	$ 48,850		$ 48,850
Common stock issuable upon conversion	6,536,856		6,536,856
Series A-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized	47,132,862		47,132,862
Preferred stock issued	47,132,862		23,566,431		16,083,916		7,482,515
Preferred stock outstanding	47,132,862	23,566,431	23,566,431	23,566,431	23,566,431	7,482,515
Carrying value	$ 66,908	$ 33,270	$ 33,270	$ 33,270	$ 33,270	$ 10,372
Liquidation preference	$ 67,400		$ 33,700
Common stock issuable upon conversion	6,307,084		3,153,537

Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2019	Nov. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock issued	95,982,862			95,982,862		95,982,862		72,416,431
Net proceeds from issuance of shares						$ 33,638,000	$ 22,898,000
Dividends declared	$ 0
Granted options						608,185	681,950	1,009,125
Weighted Average Exercise Price, Exercised						$ 1.11	$ 2.02	$ 1.04
Weighted-average grant date fair values of options granted				$ 2.25	$ 1.50	$ 2.25	$ 1.50
Aggregate intrinsic value of stock options exercised				$ 200,000	$ 100,000	$ 200,000	$ 100,000
Total unrecognized compensation cost related to outstanding employee awards	$ 2,500,000			$ 2,500,000		$ 2,500,000
Total unrecognized compensation cost related to outstanding employee awards, expected to be recognized over a weighted-average period						2 years 9 months 18 days
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock remain available for future issuance	426,065			426,065		426,065		1,025,425
Maximum \| 2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock reserved for issuance	2,730,496			2,730,496		2,730,496		2,730,496
Series A-2 Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock issued	47,132,862	16,083,916	7,482,515	47,132,862		47,132,862		23,566,431
Shares issued, price per share	$ 1.43	$ 1.43	$ 1.43	$ 1.43		$ 1.43
Net proceeds from issuance of shares	$ 33,600,000	$ 22,900,000	$ 10,400,000
Shares available for issuance to investors		23,566,431
Shares available for issuance, price per share		$ 1.43
Additional shares issued	23,566,431			23,566,431		23,566,431
Series A-2 Convertible Preferred Stock \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock issued			47,132,862

Convertible Preferred Stock and Stockholders' Equity - Summary of Stock Option Activity Under 2017 Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 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	608,185	681,950	1,009,125
Options Outstanding, Exercised	(140,073)		(69,615)
Options Outstanding, Forfeited	(20,321)		(126,640)
Options Outstanding, Ending Balance	2,083,218		1,635,427	822,557
Options Outstanding, Exercisable	544,379		521,327
Options Outstanding, Vested and expected to vest	2,083,218		1,635,427
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 1.64	$ 1.05	$ 1.05
Weighted Average Exercise Price, Granted	2.77		2.02
Weighted Average Exercise Price, Exercised	1.11	$ 2.02	1.04
Weighted Average Exercise Price, Forfeited	1.95		1.51
Weighted Average Exercise Price, Outstanding, Ending Balance	1.98		1.64	$ 1.05
Weighted Average Exercise Price, Exercisable	1.29		1.15
Weighted Average Exercise Price, Vested and expected to vest	$ 1.98		$ 1.64
Weighted Average Remaining Contractual Term (in years), Outstanding	8 years 9 months 21 days		8 years 9 months 21 days	8 years 5 months 4 days
Weighted Average Remaining Contractual Term (in years), Exercisable	7 years 7 months 13 days		7 years 10 months 28 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	8 years 9 months 21 days		8 years 9 months 21 days
Aggregate Intrinsic Value, Outstanding	$ 1,641		$ 668	$ 678
Aggregate Intrinsic Value, Exercisable	806		452
Aggregate Intrinsic Value, Vested and expected to vest	$ 1,641		$ 668

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions					1 Months Ended	6 Months Ended
	Jul. 30, 2020 USD ($) shares	Jul. 28, 2020 $ / shares shares	Jul. 23, 2020 shares	Jul. 17, 2020 shares	Jul. 31, 2020 USD ($) shares	Jun. 30, 2020 shares	Jul. 16, 2020 shares	Mar. 31, 2020 shares	Dec. 31, 2019 shares	Jun. 30, 2019 shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Subsequent Event [Line Items]
Number of authorized shares of common stock						129,000,000			129,000,000
Share based compensation options to purchase number of common stock						2,083,218			1,635,427			822,557
Convertible preferred stock, shares outstanding						95,982,862			72,416,431
Number of common stock issued upon conversion						12,843,940			9,690,393
Common Stock
Subsequent Event [Line Items]
Reverse stock split, description						one-for-7.4730
2020 Stock Incentive Plan
Subsequent Event [Line Items]
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, nonstatutory 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 shares of common stock remaining available for issuance under the 2017 Plan as of July 23, 2020. The number of shares reserved 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. 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.
2020 Employee Stock Purchase Plan
Subsequent Event [Line Items]
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.
Series A-2 Convertible Preferred Stock
Subsequent Event [Line Items]
Convertible preferred stock, shares outstanding						47,132,862		23,566,431	23,566,431	23,566,431	23,566,431	7,482,515
Number of common stock issued upon conversion						6,307,084			3,153,537
Subsequent Event
Subsequent Event [Line Items]
Number of preferred stock authorized		5,000,000
Number of authorized shares of common stock		200,000,000		138,000,000			129,000,000
Reverse stock split				0.1338
Proceeds from issuance of shares \| $	$ 116.5
Convertible preferred stock, shares outstanding		104,277,222
Number of common stock issued upon conversion		13,953,850
Subsequent Event \| IPO
Subsequent Event [Line Items]
Shares issued		7,000,000
Shares issued, price per share \| $ / shares		$ 16.00
Subsequent Event \| Underwriters
Subsequent Event [Line Items]
Shares issued	1,050,000
Subsequent Event \| Common Stock
Subsequent Event [Line Items]
Reverse stock split				0.1338
Subsequent Event \| 2020 Stock Incentive Plan
Subsequent Event [Line Items]
Common stock reserved for issuance			1,588,315
Number of common stock reserved for issuance increase percentage on stock outstanding			4.00%
Subsequent Event \| 2020 Stock Incentive Plan \| Maximum
Subsequent Event [Line Items]
Maximum common stock granted, under 2020 plan			1,588,315
Subsequent Event \| 2020 Employee Stock Purchase Plan
Subsequent Event [Line Items]
Number of common stock reserved for issuance increase percentage on stock outstanding			1.00%
Share based compensation options to purchase number of common stock			198,539
Increase in additional number of shares to be issued			397,079
Subsequent Event \| Series A-2 Convertible Preferred Stock
Subsequent Event [Line Items]
Number of preferred stock authorized				55,427,222			47,132,862
Alexion Pharmaceuticals, Inc \| Subsequent Event \| Intellectual Property
Subsequent Event [Line Items]
Acquisition of intellectual property, estimated fair value \| $					$ 17.8
Alexion Pharmaceuticals, Inc \| Subsequent Event \| Series A-2 Convertible Preferred Stock
Subsequent Event [Line Items]
Preferred stock, issued					8,294,360

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

Balance Sheet Details - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,007	$ 408
Less accumulated depreciation	(161)	(110)
Total	846	298
Laboratory Equipment and Manufacturing Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	312	308
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	98
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	92	53
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 505	$ 47

Fair Value Measurement - Summary of Financial Assets Measured at Fair Value (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	$ 52,607	$ 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	30,305	11,709
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure	4,498	1,992
Assets fair value disclosure	9,110	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	31,311	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	30,305	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	21,296	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	4,498	1,992
Assets fair value disclosure	9,110	10,906
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents fair value disclosure	4,800	2,189
Assets fair value disclosure	2,888	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	4,800	2,189
Assets fair value disclosure	2,888	3,371
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	1,006	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	$ 1,006	$ 1,250

License and Sponsored Research Agreements - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 7,877,000	$ 3,489,000	$ 14,283,000	$ 7,623,000
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	200,000	200,000	200,000
Yale \| Other Arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expenses		$ 0	$ 300,000	0	$ 300,000
Yale \| License
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maintenance fees				$ 60,000

Balance Sheet Details - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Costs	$ 12,991	$ 15,522
Gross Unrealized Gains	14	5
Gross Unrealized Losses	(1)
Estimated Fair Value	$ 13,004	$ 15,527
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Costs	$ 9,100	$ 10,903
Gross Unrealized Gains	11	3
Gross Unrealized Losses	(1)
Estimated Fair Value	$ 9,110	$ 10,906
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Amortized Costs	$ 2,888	$ 3,370
Gross Unrealized Gains		1
Estimated Fair Value	$ 2,888	$ 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	$ 1,003	$ 1,249
Gross Unrealized Gains	3	1
Estimated Fair Value	$ 1,006	$ 1,250

Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Interest receivable	$ 82	$ 104
Prepaid research studies	285
Prepaid seminars	122
Prepaid insurance	9	47
Prepaid taxes	39	42
Prepaid other	256	135
Total	$ 793	$ 328

Balance Sheet Details - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Payroll and related liabilities	$ 736	$ 861
Professional fees	1,110	268
Research and development costs	2,697	1,086
Other	785	120
Total	$ 5,328	$ 2,335

Commitments and Contingencies - Schedule of Future Minimum Commitments Under Non-Cancellable Leases (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020 (remaining 6 months)	$ 258
2021	950
2022	973
2023	997
2024	1,022
Thereafter	786
Operating lease liability	$ 4,986

Employee Benefit Plans - Additional Information (Details)	6 Months Ended
	Jun. 30, 2020 USD ($)
Compensation And Retirement Disclosure [Abstract]
Employer contribution amount	$ 0