Keros Therapeutics (KROS) 10-Q 22 May 20 2020 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2020	May 15, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-39264
Entity Registrant Name	KEROS THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-1173868
Entity Address, Address Line One	99 Hayden Avenue
Entity Address, Address Line Two	Suite 120
Entity Address, Address Line Three	Building E
Entity Address, City or Town	Lexington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02421
City Area Code	617
Local Phone Number	314-6297
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	KROS
Security Exchange Name	NASDAQ
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		20,148,663
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001664710

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 54,518	$ 7,020
Prepaid expenses and other current assets	1,197	381
Deferred IPO costs	2,019	604
Research and development incentive receivable	805	922
Total current assets	58,539	8,927
Operating lease right-of-use assets	1,116	1,205
Property and equipment, net	822	708
Restricted cash	115	115
TOTAL ASSETS	60,592	10,955
CURRENT LIABILITIES:
Accounts payable	2,426	2,088
Current portion of operating lease liabilities	388	376
Accrued expenses and other current liabilities	6,022	2,022
Total current liabilities	8,836	4,486
Operating lease liabilities, net of current portion	797	899
Preferred stock tranche liability	0	4,956
Other liabilities	104	119
Total liabilities	9,737	10,460
COMMITMENTS AND CONTINGENCIES
Convertible preferred stock, carrying amount	75,722	19,941
STOCKHOLDERS' DEFICIT:
Common stock, par value of $0.0001 per share; 35,000,000 and 27,000,000 shares authorized as of March 31, 2020 and December 31, 2019, respectively; 2,491,670 and 2,429,705 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	1	1
Additional paid-in capital	6,674	203
Accumulated deficit	(31,542)	(19,650)
Total stockholders' deficit	(24,867)	(19,446)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT	60,592	10,955
Series A Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	9,891	9,891
Series A-1 Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	944	944
Series B-1 Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	9,106	9,106
Series C Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	$ 55,781	$ 0

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Shares authorized (in shares)	26,339,678	17,289,895
PREFERRED STOCK ISSUED (in shares)	10,725,129	6,555,307
PREFERRED STOCK OUTSTANDING (in shares)	10,725,129	6,555,307
LIQUIDATION VALUE	$ 82,844	$ 26,038
Common stock, par value (USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	35,000,000	27,000,000
Common stock, shares issued (in shares)	2,491,670	2,429,705
Common stock, shares outstanding (in shares)	2,491,670	2,429,705
Series A Preferred Stock
Par value (USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	10,000,000	10,000,000
PREFERRED STOCK ISSUED (in shares)	4,607,652	4,607,652
PREFERRED STOCK OUTSTANDING (in shares)	4,607,652	4,607,652
LIQUIDATION VALUE	$ 12,471	$ 12,271
Series A-1 Preferred Stock
Par value (USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	800,000	800,000
PREFERRED STOCK ISSUED (in shares)	368,612	368,612
PREFERRED STOCK OUTSTANDING (in shares)	368,612	368,612
LIQUIDATION VALUE	$ 1,191	$ 1,171
Series B-1 Preferred Stock
Par value (USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	3,427,004	3,427,004
PREFERRED STOCK ISSUED (in shares)	1,579,043	1,579,043
PREFERRED STOCK OUTSTANDING (in shares)	1,579,043	1,579,043
LIQUIDATION VALUE	$ 12,826	$ 12,596
Series C Preferred Stock
Par value (USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	9,049,783	0
PREFERRED STOCK ISSUED (in shares)	4,169,822	0
PREFERRED STOCK OUTSTANDING (in shares)	4,169,822	0
LIQUIDATION VALUE	$ 56,356

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
REVENUE:
Research collaboration revenue	$ 0	$ 2,500
OPERATING EXPENSES:
Research and development	(8,527)	(4,867)
General and administrative	(1,977)	(491)
Total operating expenses	(10,504)	(5,358)
Operating Income (Loss), Total	(10,504)	(2,858)
OTHER EXPENSE, NET:
Interest expense, net	(2)	(2)
Research and development incentive income	0	180
Change in fair value of preferred stock tranche obligation	(1,490)	(604)
Other (expense) income, net	(68)	101
Total other expense, net	(1,560)	(325)
Loss before income taxes	(12,064)	(3,183)
Income tax benefit	172	0
Net loss	(11,892)	(3,183)
Net loss attributable to common stockholders—basic and diluted (Note 10)	$ (12,698)	$ (3,633)
Net loss per share attributable to common stockholders - basic and diluted (USD per share)	$ (5.11)	$ (1.61)
Weighted-average common stock outstanding - basic and diluted (in shares)	2,484,057	2,258,335

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders’ Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Series A Preferred Stock	Series A-1 Preferred Stock	Series B-1 Preferred Stock	Series C Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance (in shares)		2,243,648
Ending balance	$ (7,183)	$ 1	$ 130	$ (7,314)
Beginning balance (in shares) at Dec. 31, 2018					4,607,652	368,612	1,579,043	0
Beginning balance at Dec. 31, 2018					$ 9,891	$ 944	$ 9,106	$ 0
Ending balance (in shares) at Mar. 31, 2019					4,607,652	368,612	1,579,043	0
Ending balance at Mar. 31, 2019					$ 9,891	$ 944	$ 9,106	$ 0
Beginning balance (in shares) at Dec. 31, 2018		2,243,648
Beginning balance at Dec. 31, 2018	(7,183)	$ 1	130	(7,314)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)		25,918
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	11		11
Net Income (Loss) Attributable to Parent	(3,183)			(3,183)
Ending balance (in shares)		2,243,648
Ending balance	(7,183)	$ 1	130	(7,314)
Ending balance (in shares)		2,269,566
Ending balance	(10,355)	$ 1	141	(10,497)
Ending balance (in shares)		2,429,705
Ending balance	$ (19,446)	$ 1	203	(19,650)
Beginning balance (in shares) at Dec. 31, 2019	6,555,307				4,607,652	368,612	1,579,043	0
Beginning balance at Dec. 31, 2019	$ 19,941				$ 9,891	$ 944	$ 9,106	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Preferred stock, net of issuance costs of $219 (in shares)								4,169,822
preferred stock, net of issuance costs of $219								$ 55,781
Ending balance (in shares) at Mar. 31, 2020	10,725,129				4,607,652	368,612	1,579,043	4,169,822
Ending balance at Mar. 31, 2020	$ 75,722				$ 9,891	$ 944	$ 9,106	$ 55,781
Beginning balance (in shares) at Dec. 31, 2019		2,429,705
Beginning balance at Dec. 31, 2019	$ (19,446)	$ 1	203	(19,650)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)	44,686	44,686
Exercise of common stock options	$ 13		13
Vesting of restricted stock (in shares)		17,279
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	12		12
Settlement of preferred stock tranche liability	6,446		6,446
Net Income (Loss) Attributable to Parent	(11,892)			(11,892)
Ending balance (in shares)		2,429,705
Ending balance	(19,446)	$ 1	203	(19,650)
Ending balance (in shares)		2,491,670
Ending balance	$ (24,867)	$ 1	$ 6,674	$ (31,542)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) - USD ($) $ in Thousands	Mar. 02, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Common stock, par value (USD per share)		$ 0.0001	$ 0.0001	$ 0.0001
Issuance costs		$ 219	$ 0
Series A Preferred Stock
Par value (USD per share)		$ 0.0001	$ 0.0001	0.0001
Series C Preferred Stock
Par value (USD per share)	$ 0.0001	0.0001	0.0001	0.0001
Issuance costs	$ 200
Series B-1 Preferred Stock
Par value (USD per share)		0.0001	0.0001	0.0001
Series A-1 Preferred Stock
Par value (USD per share)		$ 0.0001	$ 0.0001	$ 0.0001

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income (Loss) Attributable to Parent	$ (11,892)	$ (3,183)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation expense	63	45
Stock-based compensation expense	12	11
Non-cash lease expense	89	49
Changes in fair value of preferred stock tranche obligation	1,490	604
Changes in operating assets and liabilities:
Research and development incentive receivable	117	(182)
Prepaid expenses and other current assets	(816)	1,715
Deferred IPO costs	(156)	0
Accounts payable	(193)	813
Operating lease liabilities	(90)	(50)
Deferred revenue	0	(2,500)
Accrued expenses and other current liabilities	3,271	177
Other liabilities	(15)	(12)
Net cash used in operating activities	(8,120)	(2,513)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(176)	0
Net cash used in investing activities	(176)	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of Series C preferred stock	56,000	0
Payment of issuance costs	(219)	0
Proceeds from exercise of stock options	13	0
Net cash provided by financing activities	55,794	0
NET INCREASE/(DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	47,498	(2,513)
Cash, cash equivalents and restricted cash at beginning of period	7,135	23,390	$ 23,390
Cash, cash equivalents and restricted cash at end of period	54,633	20,877	7,135
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Deferred IPO costs in accounts payable and accrued expenses	1,259	0
Settlement of preferred stock tranche obligation	6,446	0
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents				$ 54,518	$ 7,020	$ 20,746
Restricted cash				115		131
Total cash, cash equivalents and restricted cash	$ 54,633	$ 20,877	$ 23,390	$ 54,633	$ 7,135	$ 20,877

Nature of Business and Basis of

Nature of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	NATURE OF BUSINESS AND BASIS OF PRESENTATION Keros Therapeutics, Inc. (“Keros” or the “Company”) was incorporated in 2015 as a Delaware corporation. Its principal offices are in Lexington, Massachusetts. The Company is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel treatments for patients suffering from hematological and musculoskeletal disorders with high unmet medical need. The accompanying unaudited interim condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned Australian subsidiary, Keros Therapeutics Australia Pty Ltd (“Keros Australia”). All significant intercompany transactions and accounts have been eliminated in consolidation. Since its inception in 2015, the Company has devoted the majority of its resources on business planning, research and development of its product candidates, including by conducting clinical trials and preclinical studies, raising capital and recruiting management and technical staff to support these operations. To date, the Company has not generated any revenue from product sales as none of its product candidates have been approved for commercialization. As of March 31, 2020, the Company has funded its operations primarily with proceeds from the sale of convertible preferred stock (see Note 6) and its research collaboration and exclusive license agreement with Novo Nordisk A/S. On April 13, 2020, the Company completed an initial public offering (“IPO”) in which the Company issued and sold 6,900,000 shares of its common stock, which includes 900,000 shares issued and sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $16.00 per share, for aggregate gross proceeds of $110.4 million. The Company received approximately $99.8 million in net proceeds after deducting underwriting discounts and commissions and offering costs. In connection with the IPO, the Company's board of directors (the "Board") and stockholders approved an amended and restated certificate of incorporation to, among other things, effect a one-for-2.1703 reverse stock split of its issued and outstanding shares of common stock and convertible preferred stock, as well as to effect a proportional adjustment to the existing conversion ratios for the Company’s convertible preferred stock. The reverse stock split was effected on March 31, 2020. Accordingly, all share and per share amounts of common stock for all periods presented in the accompanying unaudited interim condensed consolidated financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect this reverse stock split and adjustment of preferred stock conversion ratios. Upon the closing of the IPO, all of the then-outstanding shares of convertible preferred stock automatically converted into 10,725,129 shares of common stock at the applicable conversion ratio then in effect. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. The unaudited interim condensed consolidated financial statements as of March 31, 2020, including share and per share amounts, do not give effect to the IPO, as it closed subsequent to March 31, 2020. The Company’s condensed consolidated financial statements have been prepared on the basis of the Company continuing as a going concern for the next 12 months. Management believes that the Company’s existing cash and cash equivalents, together with the net proceeds from the IPO, will allow the Company to continue its operations for at least the next 12 months. In the absence of a significant source of recurring revenue, the continued viability of the Company beyond that point is dependent on its ability to continue to raise additional capital to finance its operations. If the Company is unable to obtain additional funding, the Company may 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, or the Company may be unable to continue operations. The accompanying unaudited interim condensed consolidated financial statements as of March 31, 2020 and for the three months ended March 31, 2020 and 2019 have been prepared by the Company in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and, pursuant to the rules and regulations of Article 10 of Regulation S-X of the Securities Act published by the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes the disclosures are adequate. These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and notes thereto for the year ended December 31, 2019 included in the Company’s final prospectus that forms part of the Company’s Registration Statement on Form S-1 (Reg. No. 333-237212), filed with the SEC pursuant to Rule 424(b)(4) on April 8, 2020 (the “Prospectus”). The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair presentation of the Company’s condensed consolidated balance sheets as of March 31, 2020 and December 31, 2019, condensed consolidated statements of operations for the three months ended March 31, 2020 and 2019 and condensed consolidated cash flows for the three months ended March 31, 2020 and 2019. Such adjustments are of a normal and recurring nature. The results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies The significant accounting policies and estimates used in preparation of the unaudited interim condensed consolidated financial statements are described in the Company’s audited consolidated financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Prospectus. Except as detailed below, there have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2020. Risks and Uncertainties With the global spread of the ongoing COVID-19 pandemic in the first quarter of 2020, the Company’s management team has met frequently to discuss the implementation of business continuity plans to address and mitigate the impact of the COVID-19 pandemic on its business. Additionally, in response to the spread of COVID-19, the Company closed its principal executive office in March 2020, with its administrative employees continuing their work outside of the office, and limited the number of staff in any given research laboratory. The Company anticipates that the COVID-19 pandemic will have an impact on the clinical development timelines for several of its clinical programs. The extent to which the COVID-19 pandemic impacts the Company’s business, its clinical development and regulatory efforts, its corporate development objectives and the value of and market for its common stock will depend on future developments which are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements in the United States, Australia and other countries and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. Actual results could differ from those estimates, and any such differences may be material to the Company’s financial statements. In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its business plan and strategy, as well as risks and uncertainties common to companies in the biopharmaceutical industry with research and development operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of its product candidates; delays or problems in obtaining clinical supply, loss of single source suppliers or failure to comply with manufacturing regulations; product development and the inherent uncertainty of clinical success; the challenges of protecting and enhancing its intellectual property rights; the challenges of complying with applicable regulatory requirements; and identifying, acquiring or in-licensing additional products or product candidates. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above. Deferred Offering Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the condensed consolidated statement of operations. The Company recorded deferred offering costs, related to the IPO, of approximately $2.0 million as of March 31, 2020. Upon closing the IPO in April 2020, deferred offering costs were derecognized and recorded against the IPO proceeds as a debit to additional paid-in capital. Recently Issued Accounting Pronouncements The new accounting pronouncements recently adopted by the Company and issued by the Financial Accounting Standards Board ("FASB") that are applicable to the Company are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Prospectus filed with the SEC on April 8, 2020. There have been no new accounting pronouncements issued in the three months ended March 31, 2020 that are applicable to the Company.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): DESCRIPTION MARCH 31, 2020 QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS SIGNIFICANT OTHER OBSERVABLE INPUTS SIGNIFICANT OTHER OBSERVABLE INPUTS Asset Money market funds $ 50,543 $ 50,543 $ — $ — Total financial assets $ 50,543 $ 50,543 $ — $ — DESCRIPTION DECEMBER 31, 2019 QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3) Asset Money market funds $ 4,972 $ 4,972 $ — $ — Total financial assets $ 4,972 $ 4,972 $ — $ — Liability Preferred stock tranche obligation $ (4,956) $ — $ — $ (4,956) Total financial liabilities $ (4,956) $ — $ — $ (4,956) There have been no transfers between fair value levels during the three months ended March 31, 2020. The Company’s Preferred Stock Tranche Obligation (defined below) is carried at fair value determined according to Level 3 inputs in the fair value hierarchy as described below. The carrying values of other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities. Preferred Stock Tranche Obligation The Company determined that its obligation to issue, and the Company’s investors’ obligation to purchase additional shares of convertible preferred stock at a fixed price (i.e. the issuance price) in subsequent tranches following the initial closings of the series A, series A-1, and series B-1 convertible preferred stock (respectively, the “Series A Preferred Stock,” “Series A-1 Preferred Stock,” and “Series B-1 Preferred Stock”, which are referred to collectively with the series B-2 convertible preferred stock (the “Series B-2 Preferred Stock”) and the series C convertible preferred stock (the “Series C Preferred Stock”) as the “Preferred Stock”) financings represented a freestanding financial instrument (the “Preferred Stock Tranche Obligation”). The freestanding financial instrument was classified as a liability on the Company’s condensed consolidated balance sheets and initially recorded at fair value, with changes in fair value for each reporting period recognized in other expense, net in the condensed consolidated statement of operations. The Board determined it was probable that the milestone would be met, and then the stockholders and the Board subsequently waived the Series B-2 Preferred Stock milestone and the issuance of the Series B-2 Preferred Stock on March 2, 2020. Instead of issuing the Series B-2 Preferred Stock upon this waiver, the Company instead closed its convertible Series C Preferred Stock financing (“Series C financing”). The associated Preferred Stock Tranche Obligation was remeasured prior to settlement, with the associated $1.5 million increase in fair value recorded in the Company’s condensed consolidated statement of operations as other expense, net. As the Series C financing was executed with related parties, the Company recognized the settlement of the Preferred Stock Tranche Obligation of $6.4 million as a capital contribution in additional paid-in capital in the Company’s condensed consolidated balance sheets. The following reflects the significant quantitative inputs used in the valuation of the Preferred Stock Tranche Obligation: MARCH 2, 2020 DECEMBER 31, 2019 Stand-alone Series B-1 Preferred Stock price (spot price) $ 3.3557 $ 3.3557 Estimated future value of Series B-2 Preferred Stock $ 3.7546 $ 3.7546 Discount rate 15.50 % 15.50 % Time to liquidity (years) 0.00 0.16 Probability of tranche closing 100 % 80 % A change in the assumptions related to the valuation of the Preferred Stock Tranche Obligation could have a significant impact on the value of the obligation. The purchase price of the Preferred Stock at initial issuance, and all subsequent issuances was higher than the fair value of the Company’s common stock. The following table sets forth a summary of changes in the fair value and settlement of the Company’s Preferred Stock Tranche Obligation for which fair value is determined by Level 3 inputs (in thousands): PREFERRED STOCK TRANCHE OBLIGATION Balance as of January 1, 2019 $ 2,392 Change in fair value 2,564 Balance as of December 31, 2019 4,956 Change in fair value 1,490 Settlement of tranche obligation (6,446) Balance as of March 31, 2020 $ — Fluctuations in the fair value of the Company’s Preferred Stock is the primary cause for the significant changes in fair value of the Preferred Stock Tranche Obligation. In 2020 and 2019, the enterprise value of the Company was determined using the Market Approach, specifically the Subject Company Transaction Method, which considers all share class rights and preferences, as of the date of the most recent financing. As part of the Company’s strategy, during 2019, the Company began considering the pursuit of longer-term liquidity options including a potential initial public offering, which caused an increase in the value of the Series B-1 Preferred Stock while reducing the value of the Preferred Stock Tranche Obligation. Subsequently, in March 2020, the Company determined it was probable that the milestone criteria necessary to close the subsequent tranche would be met; as such, the value of the Preferred Stock Tranche Obligation increased. The Board then waived the milestone in favor of issuing the Series C Preferred Stock in March 2020

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	3 Months Ended
	Mar. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	PREPAID EXPENSES AND OTHER CURRENT ASSETS Prepaid expenses and other current assets consisted of the following (in thousands): MARCH 31, DECEMBER 31, Prepaid service contracts $ 459 $ 21 Income tax credit receivable 172 — Prepaid sales tax 135 65 Prepaid rent — 64 R&D payroll tax credit 96 — Other 335 231 Total prepaid expenses and other current assets $ 1,197 $ 381

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consisted of the following (in thousands): MARCH 31, DECEMBER 31, Accrued external R&D costs $ 1,336 $ 645 Accrued external manufacturing costs 2,987 282 Accrued compensation and benefits 396 749 Accrued tax 43 43 Accrued professional fees 1,034 34 Other 226 269 Total accrued expenses and other current liabilities $ 6,022 $ 2,022

Convertible Preferred Stock

Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2020
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	CONVERTIBLE PREFERRED STOCK On March 2, 2020, the Company authorized the sale and issuance of up to 9,049,783 shares of Series C Preferred Stock, par value $0.0001 per share, of which 4,169,822 shares were sold at a purchase price of $13.43 per share for gross proceeds of $56.0 million. Issuance costs were approximately $0.2 million. As part of the Company's Series C Preferred Stock issuance, 3,078,968 of the shares were issued to affiliates of members of the Board including entities affiliated with OrbiMed, entities affiliated with Pontifax, Arkin Bio Ventures Limited Partnership, entities affiliated with Partners Innovation Fund and Jasbir Seehra, Ph. D,. All issued shares reflect the reverse stock split effected March 31, 2020 while the Board authorized shares reflect the original number of shares authorized pre-split. As of March 31, 2020 and December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data): MARCH 31, 2020 PREFERRED PREFERRED STOCK ISSUED AND OUTSTANDING CARRYING LIQUIDATION COMMON STOCK ISSUABLE UPON CONVERSION Series A Preferred Stock 10,000,000 4,607,652 $ 9,891 $ 12,471 4,607,652 Series A-1 Preferred Stock 800,000 368,612 944 1,191 368,612 Series B-1 Preferred Stock 3,427,004 1,579,043 9,106 12,826 1,579,043 Series B-2 Preferred Stock 3,062,891 — — — — Series C Preferred Stock 9,049,783 4,169,822 55,781 56,356 4,169,822 26,339,678 10,725,129 $ 75,722 $ 82,844 10,725,129 DECEMBER 31, 2019 PREFERRED PREFERRED STOCK ISSUED AND OUTSTANDING CARRYING LIQUIDATION COMMON STOCK ISSUABLE UPON CONVERSION Series A Preferred Stock 10,000,000 4,607,652 $ 9,891 $ 12,271 4,607,652 Series A-1 Preferred Stock 800,000 368,612 944 1,171 368,612 Series B-1 Preferred Stock 3,427,004 1,579,043 9,106 12,596 1,579,043 Series B-2 Preferred Stock 3,062,891 — — — — 17,289,895 6,555,307 $ 19,941 $ 26,038 6,555,307 The following is a summary of the rights and privileges of the Preferred Stockholders as of March 31, 2020. Conversion: Shares of Preferred Stock are convertible, at the option of the holder, at any time, into shares of common stock. The number of shares is determined by dividing the original issuance price by the conversion price. As such, the shares of Preferred Stock effectively convert on a one-for-one basis. These rights terminate in the event of a liquidation or winding up of the Company. No fractional shares will be issued. Liquidation Preference: While the Preferred Stock is not redeemable, the shares are redeemable for cash in certain change of control events that are beyond the control of the Company. In the event of any liquidation or Deemed Liquidation Event (as defined in the Company’s articles of incorporation), the Preferred Stockholders are entitled to the greater of (i) the original issue price of the Preferred Stock plus any accrued dividends not yet paid plus any other dividends declared and unpaid or ii) the amount payable had all classes of shares been converted to common stock. In the event of a Deemed Liquidation Event, if the assets of the Company available for distribution are insufficient to pay the Preferred Stockholders in the full amount to which they are entitled, the Preferred Stockholders shall share ratably in any distribution of the assets available for distribution in proportion to the number of shares of Preferred Stock that they hold. Note that in relation to the above, the holders of Series C Preferred Stock are entitled to be paid out prior to the holders of common stock, Series A Preferred Stock, Series A-1 Preferred Stock and Series B-1 Preferred Stock. Dividends: Dividends accrue at a rate of $0.17, $0.22, $0.58263 and $1.07439 per share, per year on the anniversary of the issuance date for Series A Preferred Stock, Series A-1 Preferred Stock, Series B-1 Preferred Stock and Series C Preferred Stock, respectively. Dividends are cumulative; however, accrued dividends will be payable only if and when declared by the Board. Dividends on other classes of the Company’s stock may not be declared or paid unless the Preferred Stockholders are first paid (i) all dividends accrued and not yet paid plus (ii) the product of (a) dividends declared on an as converted basis and (b) Preferred Stock on an as converted basis. That is, if the Company declared dividends on outstanding common stock, Preferred Stockholders would receive both the dividends owed for the Preferred Stock plus that which would be owed if the Preferred Stock were converted to common stock. No dividends have been declared through March 31, 2020.

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Common Stock	COMMON STOCK As of March 31, 2020, the Company’s certificate of incorporation authorized the Company to issue 35,000,000 shares of common stock, par value $0.0001 per share. The voting, dividend and liquidation rights of the holders of the Company’s common stock are subject to and qualified by the rights, powers and preference of the holders of the Preferred Stock set forth above. Each share of common stock entitles the holder to one vote, together with the holders of Preferred Stock, on all matters submitted to the stockholders for a vote. As of March 31, 2020, no cash dividends have been declared or paid. As of March 31, 2020 and December 31, 2019, the Company has reserved the following shares of common stock for potential conversion of outstanding Preferred Stock, the vesting of restricted stock and exercise of stock options: MARCH 31, DECEMBER 31, Preferred Stock 10,725,129 6,555,307 Unvested restricted stock 17,278 34,557 Options to purchase common stock 1,116,301 1,164,017 Total 11,858,708 7,753,881

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION On March 2, 2020, the 2017 Stock Incentive Plan, as amended (the “2017 Plan”), was further amended to increase the number of shares of common stock reserved and available to be issued by 921,531 shares. As of March 31, 2020, there were an aggregate of 1,116,301 shares of common stock issuable upon the exercise of outstanding options under the 2017 Plan and an aggregate of 988,649 shares reserved for future issuance under the 2017 Plan. A summary of option activity under the 2017 Plan during the three months ended March 31, 2020 is as follows (in thousands except share and per share data): NUMBER OF OPTIONS WEIGHTED-AVERAGE EXERCISE PRICE WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS) AGGREGATE INTRINSIC VALUE Outstanding as of December 31, 2019 1,164,017 $ 0.35 8.64 $ 144 Granted — Exercised (44,686) 0.28 $ 321 Expired (3,030) 0.16 Outstanding as of March 31, 2020 1,116,301 $ 0.36 8.44 $ 7,935 Options exercisable as of December 31, 2019 608,156 $ 0.29 8.17 $ 112 Options exercisable as of March 31, 2020 602,434 $ 0.30 7.98 $ 4,319 There were no options granted in the three months ended March 31, 2020. As of March 31, 2020 and 2019, respectively, there was $0.1 million of unrecognized stock-based compensation expense related to unvested stock options, which is being recognized over a period of 2.8 years as of March 31, 2020. Shares of Restricted Common Stock The Company has granted shares of restricted common stock with time-based vesting conditions. A summary of restricted stock activity during the three months ended March 31, 2020 is as follows: THREE MONTHS ENDED MARCH 31, 2020 Unvested at the beginning of the period 34,557 Vested or released (17,279) Unvested at the end of the period 17,278 During each of the three months ended March 31, 2020 and 2019, there was less than $1,000 of unrecognized stock-based compensation expense related to unvested restricted stock. The unrecognized stock-based compensation expense is estimated to be recognized over a period of 0.04 years as of March 31, 2020. Stock-Based Compensation Expense Total stock-based compensation expense recorded for employees, directors and non-employees during the three months ended March 31, 2020 and 2019 was as follows (in thousands): THREE MONTHS ENDED MARCH 31, 2020 2019 Research and development $ 8 $ 6 General and administrative 4 5 Total stock-based compensation expense $ 12 $ 11

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXESOn March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was signed into law in the United States. The CARES Act provides numerous tax provisions and other stimulus measures, including temporary changes regarding the prior and future utilization of net operating losses and technical corrections from prior tax legislation for tax depreciation of certain qualified improvement property. The Company evaluated the provisions of the CARES Act and as a result recorded an income tax receivable of approximately $0.2 million related to the potential carryback of our 2019 net operating loss to claim a refund for prior federal tax liabilities.

Loss Per Share

Loss Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Loss Per Share	LOSS PER SHARE Basic and diluted loss per share is computed by dividing net loss attributable to common stockholders by the weighted-average common shares outstanding (in thousands, except share and per share data): THREE MONTHS ENDED MARCH 31, 2020 2019 Numerator: Net loss $ (11,892) $ (3,183) Less: Accruals of dividends of preferred stock (806) (450) Net loss attributable to common stockholders - basic and diluted $ (12,698) $ (3,633) Denominator: Weighted-average common stock outstanding - basic and diluted 2,484,057 2,258,335 Net loss per share attributable to common stockholders - basic and diluted $ (5.11) $ (1.61) The Company’s potentially dilutive securities, which include Preferred Stock, restricted stock, and stock options, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. 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 from the computation of diluted net loss per share attributable to common stockholders at March 31, 2020 and 2019 because including them would have had an anti-dilutive effect: MARCH 31, MARCH 31, Preferred Stock 10,725,129 6,555,307 Unvested restricted stock 17,278 112,309 Options to purchase common stock 1,116,301 849,039 11,858,708 7,516,655

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	REVENUE FROM CONTRACTS WITH CUSTOMERS The Company adopted FASB Accounting Standards Codification Subtopic 606, Revenue from Contracts with Customers ("ASC 606") on January 1, 2018 applying the full retrospective method to all contracts that were not completed as of January 1, 2018. While the timing of future revenue under ASC 606 may differ from the Company’s historical accounting practices under FASB Accounting Standards Codification Subtopic 605, Revenue Recognition ("ASC 605"), the cumulative effect recognized in the condensed consolidated statement of stockholder’s deficit was $0 because there was no change in timing or measurement of revenue for open contracts at January 1, 2018. Novo Nordisk On December 14, 2017, the Company entered into a research collaboration and exclusive license agreement with Novo Nordisk A/S (“Novo,” agreement referred to as the “Novo Agreement”). The Novo Agreement stipulates that the two parties will work together on the discovery and development of new ligand traps for two years. Under the Novo Agreement, Keros granted Novo an exclusive license to develop and commercialize the licensed products listed as part of Keros’ intellectual property and Novo granted Keros a non-exclusive license to Novo’s intellectual property so that Keros could perform the activities for which it is responsible under the Novo Agreement. The Company does not share in the rights to the results of the Novo Agreement. As consideration, the Company received an initial license payment in 2018 from Novo in the amount of $16.0 million. Novo has also paid the Company research collaboration budget funding payments of $2.0 million per each collaboration year, for $4.0 million total. Both of these research collaboration budget funding payments were received in 2018. Additionally, there are performance-based and sales-based milestone payments and sales-based royalties that have been determined to be variable consideration and constrained due to uncertainty of achievement. The sales-based royalties will be included in the transaction price and recognized as revenue once a sale occurs, and performance-based and sales-based milestone payments will be included in the transaction price and recognized as revenue if and when the cumulative revenue associated with the consideration is no longer probable of significant reversal. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Novo, is a customer. The Company identified the following material promises at the outset of the Novo Agreement: (1) an exclusive license to use the Company’s intellectual property to conduct research activities; (2) research and development (“R&D”) services for activities under the research plan; (3) an option to extend the Novo Agreement; (4) participation on the joint steering committee (“JSC”); and (5) technology transfer associated with the research and development outputs. The Company determined that these promises were not capable of being distinct from one another and were not distinct in the context of the contract, as the license has no true value without the performance of the R&D activities and the technology transfer and JSC participation depend on these activities. Novo would not be able to use the license without the performance of R&D activities by the Company, as the research is novel in nature and could not be performed by another company. Additionally, the technology transfer is inherently dependent on the outcome of the Company’s R&D activities, and as such is not capable of being distinct. As indicated in number (3) above, Novo may elect to extend the term of the Novo Agreement to a third year on similar terms and conditions, subject to mutual written agreement of Novo and the Company. The Company assessed this option as a potential material right and determined that the additional work would be performed based on negotiated rates at the standalone selling price, and as such these services would not be provided at a significant or incremental discount and the option does not provide Novo with a material right. In accordance with the Company’s ASC 606 assessment, the Novo Agreement was determined to contain a single combined performance obligation made up of the promises above, which does not require further allocation as the entire transaction price is allocated to this performance obligation. The Company determined the contract term of the Novo Agreement to be two years. The Company identified an appropriate measure of progress for the recognition of revenue and determined it would recognize the revenue over the term of the Novo Agreement using an input method based on full-time employee costs incurred, as this appropriately depicts the Company’s performance in satisfaction of the performance obligation. As such, the Company is recognizing the transaction price for its single performance obligation as Novo uses the license and research and development services performed by the Company and as the Company participates on the JSC. The Company recognized $0 and $2.5 million of revenue in its condensed consolidated statements of operations for the three months ended March 31, 2020 and 2019, respectively, related to the Novo Agreement. As of

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Accounting	The accompanying unaudited interim condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned Australian subsidiary, Keros Therapeutics Australia Pty Ltd (“Keros Australia”). All significant intercompany transactions and accounts have been eliminated in consolidation.
Deferred Offering Costs	Deferred Offering CostsThe Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the condensed consolidated statement of operations.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements The new accounting pronouncements recently adopted by the Company and issued by the Financial Accounting Standards Board ("FASB") that are applicable to the Company are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Prospectus filed with the SEC on April 8, 2020. There have been no new accounting pronouncements issued in the three months ended March 31, 2020 that are applicable to the Company.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): DESCRIPTION MARCH 31, 2020 QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS SIGNIFICANT OTHER OBSERVABLE INPUTS SIGNIFICANT OTHER OBSERVABLE INPUTS Asset Money market funds $ 50,543 $ 50,543 $ — $ — Total financial assets $ 50,543 $ 50,543 $ — $ — DESCRIPTION DECEMBER 31, 2019 QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3) Asset Money market funds $ 4,972 $ 4,972 $ — $ — Total financial assets $ 4,972 $ 4,972 $ — $ — Liability Preferred stock tranche obligation $ (4,956) $ — $ — $ (4,956) Total financial liabilities $ (4,956) $ — $ — $ (4,956)
Fair Value Measurement Inputs and Valuation Techniques	The following reflects the significant quantitative inputs used in the valuation of the Preferred Stock Tranche Obligation: MARCH 2, 2020 DECEMBER 31, 2019 Stand-alone Series B-1 Preferred Stock price (spot price) $ 3.3557 $ 3.3557 Estimated future value of Series B-2 Preferred Stock $ 3.7546 $ 3.7546 Discount rate 15.50 % 15.50 % Time to liquidity (years) 0.00 0.16 Probability of tranche closing 100 % 80 %
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following table sets forth a summary of changes in the fair value and settlement of the Company’s Preferred Stock Tranche Obligation for which fair value is determined by Level 3 inputs (in thousands): PREFERRED STOCK TRANCHE OBLIGATION Balance as of January 1, 2019 $ 2,392 Change in fair value 2,564 Balance as of December 31, 2019 4,956 Change in fair value 1,490 Settlement of tranche obligation (6,446) Balance as of March 31, 2020 $ —

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	3 Months Ended
	Mar. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): MARCH 31, DECEMBER 31, Prepaid service contracts $ 459 $ 21 Income tax credit receivable 172 — Prepaid sales tax 135 65 Prepaid rent — 64 R&D payroll tax credit 96 — Other 335 231 Total prepaid expenses and other current assets $ 1,197 $ 381

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
Payables and Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): MARCH 31, DECEMBER 31, Accrued external R&D costs $ 1,336 $ 645 Accrued external manufacturing costs 2,987 282 Accrued compensation and benefits 396 749 Accrued tax 43 43 Accrued professional fees 1,034 34 Other 226 269 Total accrued expenses and other current liabilities $ 6,022 $ 2,022

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	3 Months Ended
	Mar. 31, 2020
Temporary Equity Disclosure [Abstract]
Summary of Preferred Stock	As of March 31, 2020 and December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data): MARCH 31, 2020 PREFERRED PREFERRED STOCK ISSUED AND OUTSTANDING CARRYING LIQUIDATION COMMON STOCK ISSUABLE UPON CONVERSION Series A Preferred Stock 10,000,000 4,607,652 $ 9,891 $ 12,471 4,607,652 Series A-1 Preferred Stock 800,000 368,612 944 1,191 368,612 Series B-1 Preferred Stock 3,427,004 1,579,043 9,106 12,826 1,579,043 Series B-2 Preferred Stock 3,062,891 — — — — Series C Preferred Stock 9,049,783 4,169,822 55,781 56,356 4,169,822 26,339,678 10,725,129 $ 75,722 $ 82,844 10,725,129 DECEMBER 31, 2019 PREFERRED PREFERRED STOCK ISSUED AND OUTSTANDING CARRYING LIQUIDATION COMMON STOCK ISSUABLE UPON CONVERSION Series A Preferred Stock 10,000,000 4,607,652 $ 9,891 $ 12,271 4,607,652 Series A-1 Preferred Stock 800,000 368,612 944 1,171 368,612 Series B-1 Preferred Stock 3,427,004 1,579,043 9,106 12,596 1,579,043 Series B-2 Preferred Stock 3,062,891 — — — — 17,289,895 6,555,307 $ 19,941 $ 26,038 6,555,307 As of March 31, 2020 and December 31, 2019, the Company has reserved the following shares of common stock for potential conversion of outstanding Preferred Stock, the vesting of restricted stock and exercise of stock options: MARCH 31, DECEMBER 31, Preferred Stock 10,725,129 6,555,307 Unvested restricted stock 17,278 34,557 Options to purchase common stock 1,116,301 1,164,017 Total 11,858,708 7,753,881

Common Stock (Tables)

Common Stock (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Summary of Common Stock Reserved for Potential Conversion of Outstanding Preferred Stock and Vesting of Restricted Stock and Exercise of Stock Options	As of March 31, 2020 and December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data): MARCH 31, 2020 PREFERRED PREFERRED STOCK ISSUED AND OUTSTANDING CARRYING LIQUIDATION COMMON STOCK ISSUABLE UPON CONVERSION Series A Preferred Stock 10,000,000 4,607,652 $ 9,891 $ 12,471 4,607,652 Series A-1 Preferred Stock 800,000 368,612 944 1,191 368,612 Series B-1 Preferred Stock 3,427,004 1,579,043 9,106 12,826 1,579,043 Series B-2 Preferred Stock 3,062,891 — — — — Series C Preferred Stock 9,049,783 4,169,822 55,781 56,356 4,169,822 26,339,678 10,725,129 $ 75,722 $ 82,844 10,725,129 DECEMBER 31, 2019 PREFERRED PREFERRED STOCK ISSUED AND OUTSTANDING CARRYING LIQUIDATION COMMON STOCK ISSUABLE UPON CONVERSION Series A Preferred Stock 10,000,000 4,607,652 $ 9,891 $ 12,271 4,607,652 Series A-1 Preferred Stock 800,000 368,612 944 1,171 368,612 Series B-1 Preferred Stock 3,427,004 1,579,043 9,106 12,596 1,579,043 Series B-2 Preferred Stock 3,062,891 — — — — 17,289,895 6,555,307 $ 19,941 $ 26,038 6,555,307 As of March 31, 2020 and December 31, 2019, the Company has reserved the following shares of common stock for potential conversion of outstanding Preferred Stock, the vesting of restricted stock and exercise of stock options: MARCH 31, DECEMBER 31, Preferred Stock 10,725,129 6,555,307 Unvested restricted stock 17,278 34,557 Options to purchase common stock 1,116,301 1,164,017 Total 11,858,708 7,753,881

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Option Activity	A summary of option activity under the 2017 Plan during the three months ended March 31, 2020 is as follows (in thousands except share and per share data): NUMBER OF OPTIONS WEIGHTED-AVERAGE EXERCISE PRICE WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS) AGGREGATE INTRINSIC VALUE Outstanding as of December 31, 2019 1,164,017 $ 0.35 8.64 $ 144 Granted — Exercised (44,686) 0.28 $ 321 Expired (3,030) 0.16 Outstanding as of March 31, 2020 1,116,301 $ 0.36 8.44 $ 7,935 Options exercisable as of December 31, 2019 608,156 $ 0.29 8.17 $ 112 Options exercisable as of March 31, 2020 602,434 $ 0.30 7.98 $ 4,319
Summary of Restricted Stock Activity	A summary of restricted stock activity during the three months ended March 31, 2020 is as follows: THREE MONTHS ENDED MARCH 31, 2020 Unvested at the beginning of the period 34,557 Vested or released (17,279) Unvested at the end of the period 17,278
Schedule of Stock-based Compensation Expense	Total stock-based compensation expense recorded for employees, directors and non-employees during the three months ended March 31, 2020 and 2019 was as follows (in thousands): THREE MONTHS ENDED MARCH 31, 2020 2019 Research and development $ 8 $ 6 General and administrative 4 5 Total stock-based compensation expense $ 12 $ 11

Loss Per Share (Tables)

Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Basic and Diluted Loss Per Share Calculation	Basic and diluted loss per share is computed by dividing net loss attributable to common stockholders by the weighted-average common shares outstanding (in thousands, except share and per share data): THREE MONTHS ENDED MARCH 31, 2020 2019 Numerator: Net loss $ (11,892) $ (3,183) Less: Accruals of dividends of preferred stock (806) (450) Net loss attributable to common stockholders - basic and diluted $ (12,698) $ (3,633) Denominator: Weighted-average common stock outstanding - basic and diluted 2,484,057 2,258,335 Net loss per share attributable to common stockholders - basic and diluted $ (5.11) $ (1.61)
Schedule of Antidilutive Securities Excluded From Computation of Diluted Net Loss Per Share	The Company excluded the following from the computation of diluted net loss per share attributable to common stockholders at March 31, 2020 and 2019 because including them would have had an anti-dilutive effect: MARCH 31, MARCH 31, Preferred Stock 10,725,129 6,555,307 Unvested restricted stock 17,278 112,309 Options to purchase common stock 1,116,301 849,039 11,858,708 7,516,655

Nature of Business and Basis _2

Nature of Business and Basis of Presentation (Details) - Subsequent Event $ / shares in Units, $ in Millions	Apr. 13, 2020USD ($)$ / sharesshares
Class of Stock [Line Items]
Proceeds from initial public offering | $	$ 110.4
Proceeds from initial public offering, net of discounts and offering costs | $	$ 99.8
Common Stock
Class of Stock [Line Items]
Number of shares issued upon conversion of convertible preferred stock (in shares)	10,725,129
IPO
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	6,900,000
Sale of stock, price per share (in dollars per share) | $ / shares	$ 16
Over-Allotment Option
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	900,000

Summary of Significant Accoun_3

Summary of Significant Accounting Polices (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Deferred offering costs	$ 2,019	$ 604

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Liability
Preferred stock tranche obligation	$ 0	$ (4,956)
Fair Value, Recurring
Asset
Money market funds	50,543	4,972
Total financial assets	50,543	4,972
Liability
Preferred stock tranche obligation		(4,956)
Total financial liabilities		(4,956)
Fair Value, Recurring | QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset
Money market funds	50,543	4,972
Total financial assets	50,543	4,972
Liability
Preferred stock tranche obligation		0
Total financial liabilities		0
Fair Value, Recurring | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset
Money market funds	0	0
Total financial assets	0	0
Liability
Preferred stock tranche obligation		0
Total financial liabilities		0
Fair Value, Recurring | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	0	0
Total financial assets	$ 0	0
Liability
Preferred stock tranche obligation		(4,956)
Total financial liabilities		$ (4,956)

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in fair value of preferred stock tranche obligation	$ 1,490	$ 604
Preferred Stock Tranche Obligation
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in fair value of preferred stock tranche obligation	1,490		$ 2,564
Settlement of tranche obligation	6,446
Preferred stock tranche obligation	$ 0		$ 4,956	$ 2,392

Fair Value Measurements - Signi

Fair Value Measurements - Significant Quantitative Inputs (Details)	Mar. 02, 2020$ / shares	Dec. 31, 2019$ / shares
Stand-alone Series B-1 Preferred Stock price (spot price) | Series B-1 Preferred Stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input (USD per share)	$ 3.3557	$ 3.3557
Estimated future value of Series B-2 Preferred Stock | Series B-2 Preferred Stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input (USD per share)	$ 3.7546	$ 3.7546
Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input, percent	0.1550	0.1550
Time to liquidity (years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input, term	0 years	1 month 28 days
Probability of tranche closing
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input, percent	1	0.80

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Fair Value Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes in fair value of preferred stock tranche obligation	$ 1,490	$ 604
Preferred Stock Tranche Obligation
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	4,956	$ 2,392	$ 2,392
Changes in fair value of preferred stock tranche obligation	1,490		2,564
Settlement of tranche obligation	(6,446)
Ending balance	$ 0		$ 4,956

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid service contracts	$ 459	$ 21
Income tax credit receivable	172	0
Prepaid sales tax	135	65
Prepaid rent	0	64
R&D payroll tax credit	96	0
Other	335	231
Total prepaid expenses and other current assets	$ 1,197	$ 381

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued external R&D costs	$ 1,336	$ 645
Accrued external manufacturing costs	2,987	282
Accrued compensation and benefits	396	749
Accrued tax	43	43
Accrued professional fees	1,034	34
Other	226	269
Total accrued expenses and other current liabilities	$ 6,022	$ 2,022

Convertible Preferred Stock - N

Convertible Preferred Stock - Narrative (Details) - USD ($)	Mar. 02, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Temporary Equity [Line Items]
Shares authorized (in shares)		26,339,678		17,289,895
Issuance costs		$ 219,000	$ 0
Series C Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)	9,049,783	9,049,783		0
Par value (USD per share)	$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Sale of stock, number of shares issued in transaction (in shares)	4,169,822
Sale of stock, price per share (in dollars per share)	$ 13.43
Gross proceeds from issuance of convertible preferred stock	$ 56,000,000
Issuance costs	$ 200,000
Preferred stock, dividend rate (in USD per share)		$ 1.07439
Series C Preferred Stock | Affiliates of the Board
Temporary Equity [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,078,968
Series A Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		10,000,000		10,000,000
Par value (USD per share)		$ 0.0001	0.0001	$ 0.0001
Preferred stock, dividend rate (in USD per share)		$ 0.17
Series A-1 Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		800,000		800,000
Par value (USD per share)		$ 0.0001	0.0001	$ 0.0001
Preferred stock, dividend rate (in USD per share)		$ 0.22
Series B-1 Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)		3,427,004		3,427,004
Par value (USD per share)		$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, dividend rate (in USD per share)		$ 0.58263
Convertible Preferred Stock | Dividend Declared
Temporary Equity [Line Items]
Dividends payable		$ 0

Convertible Preferred Stock - S

Convertible Preferred Stock - Summary of Preferred Stock (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 02, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	26,339,678		17,289,895
PREFERRED STOCK ISSUED (in shares)	10,725,129		6,555,307
PREFERRED STOCK OUTSTANDING (in shares)	10,725,129		6,555,307
CARRYING VALUE	$ 75,722		$ 19,941
LIQUIDATION VALUE	$ 82,844		$ 26,038
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)	10,725,129		6,555,307
Series A Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	10,000,000		10,000,000
PREFERRED STOCK ISSUED (in shares)	4,607,652		4,607,652
PREFERRED STOCK OUTSTANDING (in shares)	4,607,652		4,607,652	4,607,652	4,607,652
CARRYING VALUE	$ 9,891		$ 9,891	$ 9,891	$ 9,891
LIQUIDATION VALUE	$ 12,471		$ 12,271
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)	4,607,652		4,607,652
Series A-1 Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	800,000		800,000
PREFERRED STOCK ISSUED (in shares)	368,612		368,612
PREFERRED STOCK OUTSTANDING (in shares)	368,612		368,612	368,612	368,612
CARRYING VALUE	$ 944		$ 944	$ 944	$ 944
LIQUIDATION VALUE	$ 1,191		$ 1,171
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)	368,612		368,612
Series B-1 Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	3,427,004		3,427,004
PREFERRED STOCK ISSUED (in shares)	1,579,043		1,579,043
PREFERRED STOCK OUTSTANDING (in shares)	1,579,043		1,579,043	1,579,043	1,579,043
CARRYING VALUE	$ 9,106		$ 9,106	$ 9,106	$ 9,106
LIQUIDATION VALUE	$ 12,826		$ 12,596
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)	1,579,043		1,579,043
Series B-2 Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	3,062,891		3,062,891
PREFERRED STOCK ISSUED (in shares)	0		0
PREFERRED STOCK OUTSTANDING (in shares)	0		0
CARRYING VALUE	$ 0		$ 0
LIQUIDATION VALUE	$ 0		$ 0
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)	0		0
Series C Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	9,049,783	9,049,783	0
PREFERRED STOCK ISSUED (in shares)	4,169,822		0
PREFERRED STOCK OUTSTANDING (in shares)	4,169,822		0	0	0
CARRYING VALUE	$ 55,781		$ 0	$ 0	$ 0
LIQUIDATION VALUE	$ 56,356
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)	4,169,822

Common Stock - Narrative (Detai

Common Stock - Narrative (Details)	3 Months Ended
	Mar. 31, 2020USD ($)vote$ / sharesshares	Dec. 31, 2019$ / sharesshares	Mar. 31, 2019$ / shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares) | shares	35,000,000	27,000,000
Common stock, par value (USD per share) | $ / shares	$ 0.0001	$ 0.0001	$ 0.0001
Number of votes per common share held | vote	1
Dividend Declared | Common Stock
Class of Stock [Line Items]
Dividends payable | $	$ 0

Common Stock - Summary of Commo

Common Stock - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	11,858,708	7,753,881
Unvested restricted stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	17,278	34,557
Options to purchase common stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	1,116,301	1,164,017
Preferred Stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	10,725,129	6,555,307

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	Mar. 02, 2020	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of option shares granted (in shares)		0
Unrecognized stock-based compensation expense related to unvested stock options		$ 100	$ 100
Unrecognized stock-based compensation expense related to unvested restricted stock (less than)		$ 1	$ 1
Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested award, period for recognition		2 years 9 months 18 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested award, period for recognition		14 days
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (in shares)	921,531
Number of shares authorized (in shares)		1,116,301
Number of shares available for future grants (in shares)		988,649

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
NUMBER OF OPTIONS
Outstanding as of beginning of period (in shares)	1,164,017
Granted (in shares)	0
Exercised (in shares)	(44,686)
Expired (in shares)	(3,030)
Outstanding as of end of period (in shares)	1,116,301	1,164,017
Exercisable (in shares)	602,434	608,156
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding as of beginning of period (USD per share)	$ 0.35
Exercised (USD per share)	0.28
Expired (USD per share)	0.16
Outstanding as of end of period (USD per share)	0.36	$ 0.35
Exercisable (USD per share)	$ 0.30	$ 0.29
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)
Outstanding	8 years 5 months 8 days	8 years 7 months 20 days
Exercisable	7 years 11 months 23 days	8 years 2 months 1 day
AGGREGATE INTRINSIC VALUE
Outstanding	$ 7,935	$ 144
Exercised	321
Exercisable	$ 4,319	$ 112

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock	3 Months Ended
	Mar. 31, 2020shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested at the beginning of the period (in shares)	34,557
Vested or released (in shares)	(17,279)
Unvested at the end of the period (in shares)	17,278

Stock-Based Compensation - Allo

Stock-Based Compensation - Allocation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 12	$ 11
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	8	6
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 4	$ 5

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax credit receivable	$ 172	$ 0

Loss Per Share - Calculation (D

Loss Per Share - Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net Income (Loss) Attributable to Parent	$ (11,892)	$ (3,183)
Less: Accruals of dividends of preferred stock	(806)	(450)
Net loss attributable to common stockholders—basic and diluted (Note 10)	$ (12,698)	$ (3,633)
Denominator:
Weighted-average common stock outstanding - basic and diluted (in shares)	2,484,057	2,258,335
Net loss per share attributable to common stockholders - basic and diluted (USD per share)	$ (5.11)	$ (1.61)

Loss Per Share - Antidilutive S

Loss Per Share - Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	11,858,708	7,516,655
Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	10,725,129	6,555,307
Unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	17,278	112,309
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,116,301	849,039

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Details) - USD ($)	Dec. 14, 2017	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit		$ (31,542,000)			$ (19,650,000)
Research collaboration revenue		$ 0	$ 2,500,000
Deferred revenue					0
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit						$ 0
License Agreement | Novo Nordisk A/S
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
License agreement proceeds received				$ 16,000,000
Annual collaboration budget funding	$ 2,000,000
Cumulative proceeds received from collaboration budget funding					$ 4,000,000