Scholar Rock Holding (SRRK) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 04, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-38501
Entity Registrant Name	SCHOLAR ROCK HOLDING CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-3750435
Entity Address, Address Line One	620 Memorial Drive, 2nd Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	259 3860
Title of 12(b) Security	Common Stock
Trading Symbol	SRRK
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,638,829
Entity Central Index Key	0001727196
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 56,227	$ 36,308
Marketable securities	60,037	121,140
Accounts receivable		25,000
Prepaid expenses and other current assets	3,117	2,719
Total current assets	119,381	185,167
Property and equipment, net	5,550	4,171
Operating lease right-of-use asset	34,942	4,447
Restricted cash	2,498	2,498
Other long-term assets	1,050	98
Total assets	163,421	196,381
Current liabilities:
Accounts payable	1,106	1,130
Accrued expenses	10,968	9,610
Operating lease liability	4,072	1,135
Deferred revenue	16,706	20,923
Other current liabilities	17	16
Total current liabilities	32,869	32,814
Long-term portion of operating lease liability	28,830	4,168
Other long-term liabilities	6	9
Long-term portion of deferred revenue	38,739	46,489
Total liabilities	100,444	83,480
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2020 and December 31, 2019; no shares issued and outstanding at September 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 150,000,000 shares authorized and 29,917,907 shares issued and outstanding as of September 30, 2020; 150,000,000 shares authorized and 29,792,922 shares issued and outstanding as of December 31, 2019	30	30
Additional paid-in capital	280,704	270,682
Accumulated other comprehensive income	3	37
Accumulated deficit	(217,760)	(157,848)
Total stockholders' equity	62,977	112,901
Total liabilities and stockholders' equity	$ 163,421	$ 196,381

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENT OF FINANCIAL POSITION
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	29,917,907	29,792,922
Common stock, shares outstanding	29,917,907	29,792,922

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
CONSOLIDATED STATEMENT OF COMPREHENSIVE LOSS
Revenue	$ 3,037	$ 4,774	$ 11,967	$ 12,919
Operating expenses:
Research and development	18,383	15,699	52,282	40,153
General and administrative	8,272	6,181	20,459	14,961
Total operating expenses	26,655	21,880	72,741	55,114
Loss from operations	(23,618)	(17,106)	(60,774)	(42,195)
Other income (expense), net	57	959	862	2,768
Net loss	$ (23,561)	$ (16,147)	$ (59,912)	$ (39,427)
Net loss per share, basic and diluted (in dollars per share)	$ (0.79)	$ (0.55)	$ (2.02)	$ (1.46)
Weighted average common shares outstanding, basic and diluted (in shares)	29,779,114	29,232,158	29,665,995	26,929,215
Comprehensive loss:
Net loss	$ (23,561)	$ (16,147)	$ (59,912)	$ (39,427)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	(46)	(32)	(34)	34
Total other comprehensive income (loss)	(46)	(32)	(34)	34
Comprehensive loss	$ (23,607)	$ (16,179)	$ (59,946)	$ (39,393)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Total
Balance at beginning at Dec. 31, 2018	$ 26	$ 213,453	$ (8)	$ (106,848)	$ 106,623
Balance at beginning (in shares) at Dec. 31, 2018	26,217,701
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			24		24
Restricted shares forfeited during the period (in shares)	(2,237)
Exercise of stock options		13			13
Exercise of stock options (in shares)	1,983
Equity-based compensation expense		1,618			1,618
Net Loss				(10,755)	(10,755)
Balance at end at Mar. 31, 2019	$ 26	215,084	16	(117,603)	97,523
Balance at end (in shares) at Mar. 31, 2019	26,217,447
Balance at beginning at Dec. 31, 2018	$ 26	213,453	(8)	(106,848)	106,623
Balance at beginning (in shares) at Dec. 31, 2018	26,217,701
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities					34
Net Loss					(39,427)
Balance at end at Sep. 30, 2019	$ 30	268,009	26	(146,275)	121,790
Balance at end (in shares) at Sep. 30, 2019	29,678,422
Balance at beginning at Mar. 31, 2019	$ 26	215,084	16	(117,603)	97,523
Balance at beginning (in shares) at Mar. 31, 2019	26,217,447
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			42		42
Sale of common shares sold in IPO, net of offering costs	$ 3	42,019			42,022
Sale of common shares sold in IPO, net of offering costs (in shares)	3,000,000
Exercise of stock options		79			79
Exercise of stock options (in shares)	12,883
Equity-based compensation expense		1,814			1,814
Net Loss				(12,525)	(12,525)
Balance at end at Jun. 30, 2019	$ 29	258,996	58	(130,128)	128,955
Balance at end (in shares) at Jun. 30, 2019	29,230,330
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			(32)		(32)
Restricted shares forfeited during the period (in shares)	(1,973)
Sale of common shares, net of issuance costs	$ 1	6,325			6,326
Sale of common shares, net of issuance costs (in shares)	450,000
Exercise of stock options (in shares)	65
Equity-based compensation expense		2,688			2,688
Net Loss				(16,147)	(16,147)
Balance at end at Sep. 30, 2019	$ 30	268,009	26	(146,275)	121,790
Balance at end (in shares) at Sep. 30, 2019	29,678,422
Balance at beginning at Dec. 31, 2019	$ 30	270,682	37	(157,848)	112,901
Balance at beginning (in shares) at Dec. 31, 2019	29,792,922
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			197		197
Exercise of stock options		405			405
Exercise of stock options (in shares)	40,252
Equity-based compensation expense		2,214			2,214
Net Loss				(17,070)	(17,070)
Balance at end at Mar. 31, 2020	$ 30	273,301	234	(174,918)	98,647
Balance at end (in shares) at Mar. 31, 2020	29,833,174
Balance at beginning at Dec. 31, 2019	$ 30	270,682	37	(157,848)	112,901
Balance at beginning (in shares) at Dec. 31, 2019	29,792,922
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities					(34)
Net Loss					(59,912)
Balance at end at Sep. 30, 2020	$ 30	280,704	3	(217,760)	62,977
Balance at end (in shares) at Sep. 30, 2020	29,917,907
Balance at beginning at Mar. 31, 2020	$ 30	273,301	234	(174,918)	98,647
Balance at beginning (in shares) at Mar. 31, 2020	29,833,174
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			(185)		(185)
Restricted shares forfeited during the period (in shares)	(42,010)
Exercise of stock options		598			598
Exercise of stock options (in shares)	83,523
Equity-based compensation expense		2,395			2,395
Net Loss				(19,281)	(19,281)
Balance at end at Jun. 30, 2020	$ 30	276,294	49	(194,199)	82,174
Balance at end (in shares) at Jun. 30, 2020	29,874,687
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			(46)		(46)
Exercise of stock options		374			374
Exercise of stock options (in shares)	43,220
Equity-based compensation expense		4,036			4,036
Net Loss				(23,561)	(23,561)
Balance at end at Sep. 30, 2020	$ 30	$ 280,704	$ 3	$ (217,760)	$ 62,977
Balance at end (in shares) at Sep. 30, 2020	29,917,907

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (59,912)	$ (39,427)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,172	917
Gain or loss on sale of property and equipment		(8)
Equity-based compensation	8,645	6,120
Amortization/accretion of investment securities	(188)	(1,023)
Non-cash operating lease expense	791	742
Change in operating assets and liabilities:
Accounts receivable	25,000
Prepaid expenses and other current assets	(4,197)	(1,001)
Other assets	(952)	(85)
Accounts payable	(24)	(664)
Accrued expenses	1,864	984
Operating lease liabilities	(818)	(625)
Deferred revenue	(11,967)	(12,919)
Other liabilities		(59)
Net cash used in operating activities	(40,586)	(47,048)
Cash flows from investing activities:
Purchases of property and equipment	(2,114)	(1,645)
Purchases of marketable securities	(79,443)	(194,608)
Sales and maturities of marketable securities	140,700	112,800
Proceeds from sale of property and equipment		8
Net cash provided by (used in) investing activities	59,143	(83,445)
Cash flows from financing activities:
Principal payments on loan payable		(365)
Proceeds from sale of common stock, net of issuance costs		48,348
Proceeds from stock option exercises	1,377	92
Other	(15)	(10)
Net cash provided by financing activities	1,362	48,065
Net increase (decrease) in cash and cash equivalents and restricted cash	19,919	(82,428)
Cash and cash equivalents and restricted cash, beginning of period	38,806	115,274
Cash and cash equivalents and restricted cash, end of period	58,725	32,846
Supplemental disclosure of non-cash items:
Property and equipment purchases in accounts payable and accrued expenses	424	832
Operating lease right-of-use asset obtained in exchange for operating lease obligation	$ 31,286	$ 5,444

Nature of the Business

Nature of the Business	9 Months Ended
	Sep. 30, 2020
Nature of the Business
Nature of the Business	1. Nature of the Business Scholar Rock Holding Corporation and its subsidiaries (collectively, the “Company”) is a biopharmaceutical company focused on the discovery and development of innovative medicines for the treatment of serious diseases in which signaling by protein growth factors plays a fundamental role. The Company’s novel understanding of the molecular mechanisms of growth factor activation enabled the development of a proprietary platform for the discovery and development of monoclonal antibodies that locally and selectively target these signaling proteins at the cellular level. The Company’s first product candidate, apitegromab (previously referred to as SRK-015), is a highly selective fully human, monoclonal antibody, with a unique mechanism of action that results in the inhibition of the activation of the growth factor, myostatin, in skeletal muscle. Apitegromab is being developed as a potential first muscle-directed therapy for the treatment of spinal muscular atrophy (“SMA”). Apitegromab is being evaluated in the Company’s TOPAZ Phase 2 proof-of-concept trial for the treatment of patients with Type 2 and Type 3 SMA. In October 2020, the Company announced positive proof-of-concept data from the six-month interim analysis in the TOPAZ clinical trial. The Company’s second product candidate, SRK-181, is being developed for the treatment of cancers that are resistant to checkpoint inhibitor (“CPI”) therapies, such as anti-PD-1 or anti-PD-(L)1 antibody therapies. SRK-181 is a potent and highly selective inhibitor of the activation of latent transforming growth factor beta-1 (“TGFβ1”). The Company initiated the DRAGON Phase 1 proof-of-concept clinical trial of SRK-181 in patients with locally advanced or metastatic solid tumors that do not respond to anti-PD-(L)1 antibodies in the first quarter of 2020 and patient dosing commenced in April 2020. Additionally, the Company continues to create a pipeline of novel product candidates with the potential to transform the lives of patients suffering from a wide range of serious diseases, including neuromuscular disorders, cancer, fibrosis and anemia. The Company was originally formed in May 2012. Its principal offices are in Cambridge, Massachusetts. Since its inception, the Company’s operations have focused on research and development of monoclonal antibodies that selectively inhibit activation of growth factors for therapeutic effect, as well as establishing the Company’s intellectual property portfolio and performing research and development activities. The Company has primarily financed its operations through various equity financings, including the initial public offering of its common stock (the “IPO”) in May 2018, a secondary offering of common stock in June 2019, and a follow-on offering of common stock and pre-funded warrants completed in November 2020 (Note 11), as well as research and development collaboration agreements. Revenue generation activities have been limited to two collaborations, both containing research services and the issuance of a license. The first agreement, executed in 2013, was with Janssen Biotech, Inc. (“Janssen”), a subsidiary of Johnson & Johnson. The second agreement (the “Gilead Collaboration Agreement”), executed in December 2018, was with Gilead Sciences, Inc. (“Gilead”). The Company began recognizing revenue on the Gilead Collaboration Agreement in 2019. No revenues have been recorded from the sale of any commercial product. The Company is subject to a number of risks similar to other life science companies, including, but not limited to, successful discovery and development of its drug candidates, raising additional capital, development by its competitors of new technological innovations, protection of proprietary technology and regulatory approval and market acceptance of the Company’s product candidates. The Company anticipates that it will continue to incur significant operating losses for the next several years as it continues to develop its product candidates. The Company believes that its existing cash, cash equivalents, and marketable securities at September 30, 2020 will be sufficient to allow the Company to fund its current operations through at least a period of one year after the date the financial statements are issued.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Summary of Significant Accounting Policies The significant accounting policies used in preparation of the unaudited 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 Annual Report on Form 10-K. There have been no material changes to the significant accounting policies previously disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. ​ Cash and Cash Equivalents and Restricted Cash ​ The following table reconciles cash and cash equivalents and restricted cash per the balance sheet to the statement of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, ​ 2020 2019 Cash and cash equivalents ​ $ 56,227 ​ $ 32,641 Restricted cash ​ 2,498 ​ 205 ​ ​ $ 58,725 ​ $ 32,846 ​ Unaudited Interim Financial Information The consolidated financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The unaudited consolidated financial statements include the accounts of Scholar Rock Holding Corporation and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and judgments that may affect the reported amounts of assets and liabilities and related disclosures of contingent assets and liabilities at the date of the financial statements and the related reporting of revenues and expenses during the reporting period. Management bases its estimates on historical experience and on various assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract Recently Issued Accounting Pronouncements The Company has reviewed all recently issued accounting pronouncements and has determined that such standards do not currently apply to its operations.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	9 Months Ended
	Sep. 30, 2020
Fair Value of Financial Assets and Liabilities
Fair Value of Financial Assets and Liabilities	3. Fair Value of Financial Assets and Liabilities The following tables summarize the assets and liabilities measured at fair value on a recurring basis at September 30, 2020 and December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at September 30, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 52,668 ​ $ 52,668 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ ​ 60,037 ​ ​ 60,037 ​ ​ — ​ ​ — Total assets ​ $ 112,705 ​ $ 112,705 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2019 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 34,896 ​ $ 34,896 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ 121,140 ​ 121,140 ​ — ​ — Total assets ​ $ 156,036 ​ $ 156,036 ​ $ — ​ $ — ​ Cash and cash equivalents and marketable securities include investments in money market funds and U.S. government securities that are valued using quoted market prices. Accordingly, money market funds and government funds are categorized as Level 1 as of September 30, 2020 and December 31, 2019. There were no transfers of assets between fair value measurement levels during the three and nine months ended September 30, 2020 or 2019. The carrying amounts reflected in the balance sheets for accounts receivable, prepaid expenses and other current assets, accounts payable, and accrued expenses approximate their fair values at September 30, 2020 and December 31, 2019, due to their short-term nature.

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2020
Marketable Securities
Marketable Securities	4. Marketable Securities The following table summarizes the Company’s investments as of September 30, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 60,034 ​ $ 3 ​ $ — ​ $ 60,037 Total available-for-sale securities ​ $ 60,034 ​ $ 3 ​ $ — ​ $ 60,037 ​ The following table summarizes the Company’s investments as of December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 121,103 ​ $ 39 ​ $ (2) ​ $ 121,140 Total available-for-sale securities ​ $ 121,103 ​ $ 39 ​ $ (2) ​ $ 121,140 ​

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Accrued Expenses
Accrued Expenses	5. Accrued Expenses As of September 30, 2020 and December 31, 2019, accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, December 31, ​ 2020 ​ 2019 Accrued payroll and related expenses ​ $ 5,014 ​ $ 4,088 Accrued external research and development expense ​ ​ 4,398 ​ ​ 4,380 Accrued professional and consulting expense ​ ​ 1,003 ​ ​ 929 Accrued other ​ 553 ​ 213 ​ ​ $ 10,968 ​ $ 9,610 ​

Equity-Based Compensation

Equity-Based Compensation	9 Months Ended
	Sep. 30, 2020
Equity-Based Compensation
Equity-Based Compensation	6. Equity-Based Compensation The Company recorded equity-based compensation expense related to all equity-based awards, which was allocated as follows in the consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2020 2019 2020 2019 Research and development expense ​ $ 900 ​ $ 577 ​ $ 2,602 ​ $ 1,794 General and administrative expense ​ 3,136 ​ 2,111 ​ 6,043 ​ 4,326 ​ ​ $ 4,036 ​ $ 2,688 ​ $ 8,645 ​ $ 6,120 ​ Equity-based compensation during the three and nine months ended September 30, 2020 includes $1.5 million related to the modification of certain equity awards. Equity-based compensation during the three and nine months ended September 30, 2019 includes $0.6 million and $0.1 million related to the acceleration and modification, respectively, of certain equity awards. ​ Restricted Stock The following table summarizes the Company’s restricted common stock activity for the current year: ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Fair ​ ​ ​ ​ Value per Share ​ Number of Shares at Issuance Restricted common stock as of December 31, 2019 302,360 ​ $ 5.77 Granted — ​ $ — Vested (174,234) ​ $ 5.77 Forfeited (42,010) ​ $ 5.77 Restricted common stock as of September 30, 2020 86,116 ​ $ 5.77 ​ As of September 30, 2020, the Company had unrecognized equity-based compensation expense of $0.4 million related to restricted stock which is expected to be recognized over a period of 0.8 years. Stock Options The following table summarizes the Company’s stock option activity for the current year: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ Number of ​ Average ​ Remaining ​ Aggregate ​ Shares Exercise Price Contractual Term Intrinsic Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ (in thousands) Outstanding as of December 31, 2019 2,401,382 ​ $ 12.63 ​ 8.36 ​ $ 6,523 Granted 2,223,315 ​ $ 14.25 ​ ​ ​ ​ ​ Exercised ​ (166,995) ​ $ 8.24 ​ ​ ​ ​ ​ Cancelled (318,463) ​ $ 13.57 ​ ​ ​ ​ ​ Outstanding as of September 30, 2020 4,139,239 ​ $ 13.60 ​ 7.65 ​ $ 18,874 Options exercisable as of September 30, 2020 1,208,910 ​ $ 12.92 ​ 6.38 ​ $ 6,850 ​ Using the Black-Scholes option pricing model, the weighted average fair value of options granted during the nine months ended September 30, 2020 was $9.96. The following weighted average assumptions were used in determining the fair value of options granted in the nine months ended September 30, 2020: ​ ​ ​ ​ Risk-free interest rate 0.95 % Expected dividend yield 0.0 % Expected term (years to liquidity) 6.21 ​ Expected volatility 81.65 % ​ As of September 30, 2020, the Company has unrecognized equity-based compensation expense related to its stock options of $23.6 million which the Company expects to recognize over the remaining weighted average vesting period of 2.8 years.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies
Commitments and Contingencies	7. Commitments and Contingencies Operating Leases 620 Memorial Facility Lease ​ In March 2015, the Company entered into a 5-year ​ 301 Binney Facility Lease ​ In November 2019, the Company entered into a facility lease at 301 Binney Street in Cambridge, Massachusetts to be used as its new corporate headquarters. The expiration date of the lease is in August 2025 and the Company has the option to extend connection with the facility lease, the Company has secured a letter of credit for $2.3 million which renews automatically each year. The lease commencement date, for accounting purposes, was reached during the three months ended September 30, 2020, and accordingly, the Company recognized the operating lease right-of-use asset and associated operating lease liability. ​ Other information related to the Company’s Leases is as follows (in thousands, except lease term and discount rate): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For Three Months Ended ​ For Nine Months Ended ​ September 30, September 30, ​ ​ 2020 ​ 2020 Lease Cost: ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 344 ​ $ 1,031 Variable lease cost ​ ​ 189 ​ ​ 567 Total lease cost ​ $ 533 ​ $ 1,598 ​ ​ ​ ​ ​ ​ For Nine Months Ended ​ ​ September 30, ​ ​ 2020 ​ Other information: ​ ​ ​ Operating cash flows used for operating leases $ 1,059 ​ Weighted average remaining lease term ​ 4.6 years ​ Weighted average incremental borrowing rate ​ 7.40 % ​ The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of September 30, 2020 (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, ​ ​ 2020 (excluding the nine months ended September 30, 2020) (1) ​ $ 350 2021 (1) ​ 8,360 2022 ​ 9,196 2023 ​ 9,070 2024 ​ ​ 8,064 2025 ​ ​ 4,498 Total lease payments ​ ​ 39,538 Less imputed interest ​ ​ (6,636) Total operating lease liabilities ​ $ 32,902 ​ (1) ​ Specifica Antibody Library ​ On December 20, 2019 (the “Effective Date”), the Company entered into a Library Development and Transfer Agreement with Specifica Inc. (“Specifica”), whereby Specifica is responsible for developing and delivering a customized antibody display library (the “Library”) for the Company to use to identify antibodies for further research, development, and commercialization. The Company expects to pay $3.7 million in fees through 2023 related to the Library. ​ Legal Proceedings ​ The Company, from time to time, may be party to litigation arising in the ordinary course of its business. The Company was not subject to any material legal proceedings during the nine months ended September 30, 2020 and 2019.

Loan Payable

Loan Payable	9 Months Ended
	Sep. 30, 2020
Loan Payable
Loan Payable	8. Loan Payable In August 2015, the Company entered into a Loan and Security Agreement with Silicon Valley Bank, which provided the Company an equipment line of credit of up to $2.0 million to finance the purchase of eligible equipment. The Company made the final payments on the loan in June 2019.

Agreements

Agreements	9 Months Ended
	Sep. 30, 2020
Agreements
Agreements	9. Agreements Collaboration with Gilead On December 19, 2018 (the “Effective Date”), the Company entered into a Master Collaboration Agreement (the “Gilead Collaboration Agreement”) with Gilead to discover and develop specific inhibitors of TGFβ activation focused on the treatment of fibrotic diseases. Under the collaboration, Gilead has exclusive options to license worldwide rights to product candidates that emerge from three of the Company’s TGFβ programs (each a “Gilead Program”). Pursuant to the Gilead Collaboration Agreement, the Company is responsible for antibody discovery and preclinical research through product candidate nomination, after which, upon exercising the option for a Gilead Program, Gilead will be responsible for the program’s preclinical and clinical development and commercialization. Such option may be exercised by Gilead at any time from the Effective Date through a date that is 90 days following the expiration of the Research Collaboration Term for a given Gilead Program, or until termination of the Gilead Program, whichever is earlier (the “Option Exercise Period”). Prior to Gilead’s exercise of an option, the Company has the lead responsibility for drug discovery and pre-clinical development of all Gilead Programs through to Development Candidate Nomination. Within a certain period of time after receiving a data package for a Development Candidate Nomination, Gilead may exercise its option to enter into a Form of License Agreement for exclusive rights to develop, manufacture and commercialize the licensed antibodies and licensed products of such Gilead Program. Revenue associated with the research and development and license performance obligations relating to the Gilead Programs is recognized as revenue as the research and development services are provided using an input method, according to the costs incurred on each Gilead Program and the costs expected to be incurred in the future to satisfy the performance obligation. The transfer of control occurs over time. In management’s judgment, this input method is the best measure of progress towards satisfying the performance obligation. The amounts allocated to the three material rights will be recognized when Gilead exercises each respective option and delivers the underlying license and transfer of know-how, or immediately as each option expires unexercised. The amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet. None of the performance obligations have been fully satisfied as of September 30, 2020. A $25.0 million preclinical milestone was achieved in December 2019 for the successful demonstration of efficacy in preclinical in vivo proof-of-concept studies. As a result, the associated $25.0 million was included in the consideration transferred and proportionally allocated to the performance obligations, as it was probable that a future material reversal will not occur. In the three and nine months ended September 30, 2020, the Company recognized $3.0 million and $12.0 million, respectively, in revenue in the Company’s consolidated statements of operations and comprehensive loss under the Gilead Collaboration Agreement. The aggregate amount of the transaction price allocated to the Company’s unsatisfied performance obligations and recorded in deferred revenue at September 30, 2020 is $55.4 million. The Company will recognize the deferred revenue related to the research and development services based on a cost input method, over the remaining research term for each respective Gilead Program, which is a maximum of 1.3 years as of September 30, 2020; each research term is dependent on the timing of Gilead either exercising its options for the Gilead Programs or terminating further development on the Gilead Programs prior to the expiration date of the research term. The deferred revenue related to the material rights will be recognized as options are exercised by Gilead or at the conclusion of the Option Exercise Period. ​

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2020
Net Loss per Share
Net Loss per Share	10. Net Loss per Share The Company calculates basic net loss per share by dividing net loss by the weighted average number of common shares outstanding, excluding restricted common stock. The Company has generated a net loss in all periods presented, so the basic and diluted net loss per share are the same, as the inclusion of the potentially dilutive securities would be anti-dilutive. The following table sets forth the outstanding common stock equivalents, presented based on amounts outstanding at each period end, that have been excluded from the calculation of diluted net loss per share for the periods indicated because their inclusion would have been anti-dilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ 2020 2019 Restricted common stock ​ 86,116 ​ 388,902 ​ Warrant ​ 7,614 ​ 7,614 ​ Stock options ​ 4,139,239 ​ 2,470,470 ​ ​ ​ 4,232,969 ​ 2,866,986 ​ ​

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events
Subsequent Events	11. Subsequent Events Sublease of 620 Memorial Drive On October 5, 2020, the Company entered into a Sublease Agreement (the “Sublease”) with Orna Therapeutics, Inc. (the “Subtenant”) to sublease approximately 20,751 square feet of office and laboratory space located at 620 Memorial Drive, Cambridge, Massachusetts. The Sublease term will commence on a date to be determined between January 1 and March 15, 2021, and ends on August 31, 2023, unless terminated earlier. The Sublease provides for initial annual base rent of approximately $1.9 million. The Subtenant will also be obligated to pay for certain costs, taxes and operating expenses, subject to certain exclusions. The Sublease is subordinate to that certain Indenture of Lease, dated March 5, 2015, by and between 620 Memorial Leasehold LLC and Scholar Rock, Inc., as amended. ​ Debt Facility ​ On October 16, 2020 (the “Closing Date”) the Company entered into a Loan and Security Agreement with Oxford Finance LLC and Silicon Valley Bank for $50.0 million (the “Loan and Security Agreement”). The first tranche of $25.0 million was funded on the Closing Date. The second $25.0 million tranche is available through December 31, 2021 upon dosing of the first patient in a Phase 3 trial for apitegromab and dosing of the first patient in Part B of the DRAGON Phase 1 trial for SRK-181. The Loan and Security Agreement will mature on May 1, 2025 and requires interest only payments for the first two years. The interest rate on the unpaid principal will be the greater of the Wall Street Journal prime rate plus 4.60% or 7.85% per annum. Prepayment is permitted and may include either a 2% or 3% fee (of the principal amount being prepaid), depending on when the prepayment is made. The Company is also required to make a final payment equal to 4% of the original principal amount. ​ Follow-On Financing ​ On October 28, 2020, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC, Jefferies LLC and Credit Suisse Securities (USA) LLC, as representatives of the several underwriters named therein (the “Underwriters”), relating to the issuance and sale of an aggregate of 3,717,948 shares of its common stock at $39.00 per share and pre-funded warrants to purchase 2,179,487 shares of its common stock. The price of each pre-funded warrant was $38.9999 , which The shares of common stock sold include 769,230 shares pursuant to the option granted by the Company to the underwriters, which option was exercised in full. Total gross proceeds of the transaction was $230.0 million, including the proceeds from the option granted to the underwriters. The offering was made pursuant to the Company’s effective shelf registration on Form S-3. The offering closed on November 2, 2020 and the Company received approximately $215.8 million in net proceeds, after deducting underwriting discounts and commissions and estimated offering expenses.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Summary of Significant Accounting Policies
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash ​ The following table reconciles cash and cash equivalents and restricted cash per the balance sheet to the statement of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, ​ 2020 2019 Cash and cash equivalents ​ $ 56,227 ​ $ 32,641 Restricted cash ​ 2,498 ​ 205 ​ ​ $ 58,725 ​ $ 32,846
Unaudited Interim Financial Information	Unaudited Interim Financial Information The consolidated financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The unaudited consolidated financial statements include the accounts of Scholar Rock Holding Corporation and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and judgments that may affect the reported amounts of assets and liabilities and related disclosures of contingent assets and liabilities at the date of the financial statements and the related reporting of revenues and expenses during the reporting period. Management bases its estimates on historical experience and on various assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates.
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract Recently Issued Accounting Pronouncements The Company has reviewed all recently issued accounting pronouncements and has determined that such standards do not currently apply to its operations.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2020
Summary of Significant Accounting Policies
Schedule of reconciles of cash and cash equivalents and restricted cash	​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, ​ 2020 2019 Cash and cash equivalents ​ $ 56,227 ​ $ 32,641 Restricted cash ​ 2,498 ​ 205 ​ ​ $ 58,725 ​ $ 32,846

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value of Financial Assets and Liabilities
Schedule of summary of the assets and liabilities measured at fair value on a recurring basis	The following tables summarize the assets and liabilities measured at fair value on a recurring basis at September 30, 2020 and December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at September 30, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 52,668 ​ $ 52,668 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ ​ 60,037 ​ ​ 60,037 ​ ​ — ​ ​ — Total assets ​ $ 112,705 ​ $ 112,705 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2019 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 34,896 ​ $ 34,896 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ 121,140 ​ 121,140 ​ — ​ — Total assets ​ $ 156,036 ​ $ 156,036 ​ $ — ​ $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2020
Marketable Securities
Summary of investments	The following table summarizes the Company’s investments as of September 30, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 60,034 ​ $ 3 ​ $ — ​ $ 60,037 Total available-for-sale securities ​ $ 60,034 ​ $ 3 ​ $ — ​ $ 60,037 ​ The following table summarizes the Company’s investments as of December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 121,103 ​ $ 39 ​ $ (2) ​ $ 121,140 Total available-for-sale securities ​ $ 121,103 ​ $ 39 ​ $ (2) ​ $ 121,140

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Accrued Expenses
Summary of accrued expenses	As of September 30, 2020 and December 31, 2019, accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, December 31, ​ 2020 ​ 2019 Accrued payroll and related expenses ​ $ 5,014 ​ $ 4,088 Accrued external research and development expense ​ ​ 4,398 ​ ​ 4,380 Accrued professional and consulting expense ​ ​ 1,003 ​ ​ 929 Accrued other ​ 553 ​ 213 ​ ​ $ 10,968 ​ $ 9,610

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Equity-Based Compensation
Summary of allocation of equity-based compensation	The Company recorded equity-based compensation expense related to all equity-based awards, which was allocated as follows in the consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2020 2019 2020 2019 Research and development expense ​ $ 900 ​ $ 577 ​ $ 2,602 ​ $ 1,794 General and administrative expense ​ 3,136 ​ 2,111 ​ 6,043 ​ 4,326 ​ ​ $ 4,036 ​ $ 2,688 ​ $ 8,645 ​ $ 6,120
Summary of restricted common stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Fair ​ ​ ​ ​ Value per Share ​ Number of Shares at Issuance Restricted common stock as of December 31, 2019 302,360 ​ $ 5.77 Granted — ​ $ — Vested (174,234) ​ $ 5.77 Forfeited (42,010) ​ $ 5.77 Restricted common stock as of September 30, 2020 86,116 ​ $ 5.77
Summary of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ Number of ​ Average ​ Remaining ​ Aggregate ​ Shares Exercise Price Contractual Term Intrinsic Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ (in thousands) Outstanding as of December 31, 2019 2,401,382 ​ $ 12.63 ​ 8.36 ​ $ 6,523 Granted 2,223,315 ​ $ 14.25 ​ ​ ​ ​ ​ Exercised ​ (166,995) ​ $ 8.24 ​ ​ ​ ​ ​ Cancelled (318,463) ​ $ 13.57 ​ ​ ​ ​ ​ Outstanding as of September 30, 2020 4,139,239 ​ $ 13.60 ​ 7.65 ​ $ 18,874 Options exercisable as of September 30, 2020 1,208,910 ​ $ 12.92 ​ 6.38 ​ $ 6,850
Schedule of fair value assumptions	​ ​ ​ ​ Risk-free interest rate 0.95 % Expected dividend yield 0.0 % Expected term (years to liquidity) 6.21 ​ Expected volatility 81.65 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies
Summary of lease costs	Other information related to the Company’s Leases is as follows (in thousands, except lease term and discount rate): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For Three Months Ended ​ For Nine Months Ended ​ September 30, September 30, ​ ​ 2020 ​ 2020 Lease Cost: ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 344 ​ $ 1,031 Variable lease cost ​ ​ 189 ​ ​ 567 Total lease cost ​ $ 533 ​ $ 1,598 ​ ​ ​ ​ ​ ​ For Nine Months Ended ​ ​ September 30, ​ ​ 2020 ​ Other information: ​ ​ ​ Operating cash flows used for operating leases $ 1,059 ​ Weighted average remaining lease term ​ 4.6 years ​ Weighted average incremental borrowing rate ​ 7.40 %
Summary of minimum lease payments	The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of September 30, 2020 (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, ​ ​ 2020 (excluding the nine months ended September 30, 2020) (1) ​ $ 350 2021 (1) ​ 8,360 2022 ​ 9,196 2023 ​ 9,070 2024 ​ ​ 8,064 2025 ​ ​ 4,498 Total lease payments ​ ​ 39,538 Less imputed interest ​ ​ (6,636) Total operating lease liabilities ​ $ 32,902 ​ (1)

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Net Loss per Share
Summary of anti-dilutive securities	​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ 2020 2019 Restricted common stock ​ 86,116 ​ 388,902 ​ Warrant ​ 7,614 ​ 7,614 ​ Stock options ​ 4,139,239 ​ 2,470,470 ​ ​ ​ 4,232,969 ​ 2,866,986 ​

Nature of the Business (Details

Nature of the Business (Details)	9 Months Ended
	Sep. 30, 2020item
Nature of the Business
Number of collaborations	2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash and cash equivalents and restricted cash
Cash and cash equivalents	$ 56,227	$ 36,308	$ 32,641
Restricted cash	2,498		205
Total	$ 58,725	$ 38,806	$ 32,846	$ 115,274

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Money market funds, included in cash and cash equivalents	$ 52,668	$ 34,896
Marketable securities:
U.S. Treasury obligations	60,037	121,140
Total assets	112,705	156,036
Level 1
Assets:
Money market funds, included in cash and cash equivalents	52,668	34,896
Marketable securities:
U.S. Treasury obligations	60,037	121,140
Total assets	$ 112,705	$ 156,036

Marketable Securities - Summary

Marketable Securities - Summary of Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Marketable securities available-for-sale
Amortization Cost	$ 60,034	$ 121,103
Gross Unrealized Gains	3	39
Gross Unrealized Losses		(2)
Estimated Fair Value	60,037	121,140
U.S. Treasury obligations
Marketable securities available-for-sale
Amortization Cost	60,034	121,103
Gross Unrealized Gains	3	39
Gross Unrealized Losses		(2)
Estimated Fair Value	$ 60,037	$ 121,140

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Expenses
Accrued payroll and related expenses	$ 5,014	$ 4,088
Accrued external research and development expense	4,398	4,380
Accrued professional and consulting expense	1,003	929
Accrued other	553	213
Accrued expenses	$ 10,968	$ 9,610

Equity-Based Compensation - Exp

Equity-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Equity-based compensation
Equity-based compensation expense	$ 4,036	$ 2,688	$ 8,645	$ 6,120
Acceleration of equity awards expense		600		600
Modification of equity awards expense	1,500	100	1,500	100
Research and development expense
Equity-based compensation
Equity-based compensation expense	900	577	2,602	1,794
General and administrative expense
Equity-based compensation
Equity-based compensation expense	$ 3,136	$ 2,111	$ 6,043	$ 4,326

Equity-Based Compensation - Res

Equity-Based Compensation - Restricted stock (Details) - Restricted common stock $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares
Number of unvested awards
Outstanding, beginning (in shares) | shares	302,360
Vested (in shares) | shares	(174,234)
Forfeited (in shares) | shares	(42,010)
Outstanding, end (in shares) | shares	86,116
Weighted Average Fair Value
Outstanding, beginning (in dollars per share) | $ / shares	$ 5.77
Vested (in dollars per share) | $ / shares	5.77
Forfeited (in dollars per share) | $ / shares	5.77
Outstanding, end (in dollars per share) | $ / shares	$ 5.77
Unrecognized equity based compensation expense | $	$ 0.4
Period for recognition	9 months 18 days

Equity-Based Compensation - Sto

Equity-Based Compensation - Stock Options (Details) - Stock options $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Number of Units
Outstanding, beginning (in shares) | shares	2,401,382
Granted (in shares) | shares	2,223,315
Exercised (in shares) | shares	(166,995)
Cancelled (in shares) | shares	(318,463)
Outstanding, end (in shares) | shares	4,139,239	2,401,382
Options exercisable, end (in shares) | shares	1,208,910
Weighted Average Exercise Price
Outstanding, beginning (in dollars per share)	$ 12.63
Granted (in dollars per share)	14.25
Exercised (in dollars per share)	8.24
Cancelled (in dollars per share)	13.57
Outstanding, end (in dollars per share)	13.60	$ 12.63
Options exercisable, end (in dollars per share)	$ 12.92
Stock options
Weighted average remaining contractual term	7 years 7 months 24 days	8 years 4 months 9 days
Weighted average remaining contractual term, exercisable	6 years 4 months 17 days
Aggregate intrinsic value, beginning | $	$ 6,523
Aggregate intrinsic value, end | $	18,874	$ 6,523
Aggregate intrinsic value, exercisable | $	$ 6,850
Weighted average grant date fair value (in dollars per share)	$ 9.96

Equity-Based Compensation - Ass

Equity-Based Compensation - Assumptions (Details) - Stock options $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Assumptions used in determining the fair value of options
Risk-free interest rate	0.95%
Expected dividend yield	0.00%
Expected term (years to liquidity)	6 years 2 months 15 days
Expected volatility	81.65%
Unrecognized equity-based compensation expense	$ 23.6
Period for recognition	2 years 9 months 18 days

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Thousands	1 Months Ended		3 Months Ended	9 Months Ended
	Nov. 30, 2019USD ($)	Feb. 28, 2018USD ($)item	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Mar. 31, 2015
Lease Cost:
Operating lease cost			$ 344	$ 1,031
Variable lease cost			189	567
Total lease cost			$ 533	1,598
Operating cash flows used for operating leases				$ 1,059
Weighted average remaining lease term			4 years 7 months 6 days	4 years 7 months 6 days
Weighted average incremental borrowing rate			7.40%	7.40%
620 Memorial Drive, Cambridge MA
Leased assets
Term of lease					5 years
Option to extend the term		true
Number of renewal options | item		1
Renewal term		5 years
620 Memorial Drive, Cambridge MA | Minimum
Leased assets
Rent for facility lease		$ 1,400
620 Memorial Drive, Cambridge MA | Maximum
Leased assets
Rent for facility lease		$ 1,700
301 Binney St, Cambridge MA
Leased assets
Lease not yet commenced, option to extend the term	true
Lease not yet commenced, renewal term	2 years
Base rent	$ 6,900
Annual upward adjustment (as a percent)	3.50%
Incentive to lease	$ 14,100
Letter of credit	$ 2,300

Commitments and Contingencies -

Commitments and Contingencies - Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 20, 2019
Maturity analysis of the annual undiscounted cash flows
2020 (excluding the nine months ended September 30, 2020)	$ 350
2021	8,360
2022	9,196
2023	9,070
2024	8,064
2025	4,498
Total lease payments	39,538
Less imputed interest	(6,636)
Total operating lease liabilities	$ 32,902
Payment commitment		$ 3,700

Loan Payable (Details)

Loan Payable (Details) $ in Millions	Aug. 31, 2015USD ($)
SVB
Loan Payable
Line of credit maximum	$ 2

Agreements - Gilead (Details)

Agreements - Gilead (Details) $ in Thousands	Dec. 19, 2018item	Dec. 31, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)
Agreements
Revenue earned			$ 3,037	$ 4,774	$ 11,967	$ 12,919
Gilead
Agreements
Number of programs | item	3
Option exercise period	90 days
Revenue proceeds		$ 25,000
Revenue earned			$ 3,000		$ 12,000

Agreements - Gilead obligation

Agreements - Gilead obligation period (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01 - Gilead $ in Millions	Sep. 30, 2020USD ($)
Agreements
Contract liability	$ 55.4
Expected to recognize remaining deferred revenue	1 year 3 months 18 days

Net Loss per Share - Anti-dilut

Net Loss per Share - Anti-dilutive (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	4,232,969	2,866,986
Restricted common stock
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	86,116	388,902
Warrant
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	7,614	7,614
Stock options
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	4,139,239	2,470,470

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Thousands	Nov. 02, 2020USD ($)	Oct. 28, 2020USD ($)$ / sharesshares	Oct. 16, 2020USD ($)	Oct. 05, 2020USD ($)ft²	Sep. 30, 2019USD ($)
Subsequent Events
Proceeds from sale of common stock, net of issuance costs					$ 48,348
Subsequent Event
Subsequent Events
Sale of common shares, net of issuance costs (in shares) | shares		3,717,948
Sales price (in dollars per share) | $ / shares		$ 39
Warrant to purchase | shares		2,179,487
Pre-funded warrants (in dollars per share) | $ / shares		$ 38.9999
Warrant purchase price (in dollars per share) | $ / shares		$ 0.0001
Proceeds from stock before issuance costs		$ 230,000
Proceeds from sale of common stock, net of issuance costs	$ 215,800
Subsequent Event | Over-Allotment Option
Subsequent Events
Sale of common shares, net of issuance costs (in shares) | shares		769,230
Subsequent Event | Loan and Security Agreement
Subsequent Events
Line of credit maximum			$ 50,000
Interest only period			2 years
Debt instrument, effective interest rate (as a percent)			7.85%
Final payment fee (as a percent)			4.00%
Subsequent Event | Loan and Security Agreement | Minimum
Subsequent Events
Prepayment penalty (as a percent)			2.00%
Subsequent Event | Loan and Security Agreement | Maximum
Subsequent Events
Prepayment penalty (as a percent)			3.00%
Subsequent Event | Loan and Security Agreement | Wall Street Journal prime rate
Subsequent Events
Variable rate (as a percent)			4.60%
Subsequent Event | Loan and Security Agreement | Tranche One [Member]
Subsequent Events
Proceeds from credit facility			$ 25,000
Subsequent Event | Loan and Security Agreement | Tranche Two [Member]
Subsequent Events
Line of credit maximum			$ 25,000
Subsequent Event | 620 Memorial Drive, Cambridge MA
Subsequent Events
Area of property subleased | ft²				20,751
Sublease annual base rent				$ 1,900