Scholar Rock Holding (SRRK) 10-Q 7 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 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		29,874,687
Entity Central Index Key	0001727196
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 115,128	$ 36,308
Marketable securities	26,048	121,140
Accounts receivable		25,000
Prepaid expenses and other current assets	4,011	2,719
Total current assets	145,187	185,167
Property and equipment, net	3,690	4,171
Operating lease right-of-use asset	3,924	4,447
Restricted cash	2,498	2,498
Other long-term assets	1,061	98
Total assets	156,360	196,381
Current liabilities:
Accounts payable	2,680	1,130
Accrued expenses	8,233	9,610
Operating lease liability	1,272	1,135
Deferred revenue	20,362	20,923
Other current liabilities	20	16
Total current liabilities	32,567	32,814
Long-term portion of operating lease liability	3,490	4,168
Other long-term liabilities	9	9
Long-term portion of deferred revenue	38,120	46,489
Total liabilities	74,186	83,480
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2020 and December 31, 2019; no shares issued and outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 150,000,000 shares authorized and 29,874,687 shares issued and outstanding as of June 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	276,294	270,682
Accumulated other comprehensive income	49	37
Accumulated deficit	(194,199)	(157,848)
Total stockholders' equity	82,174	112,901
Total liabilities and stockholders' equity	$ 156,360	$ 196,381

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 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	29,874,687	29,792,922
Common stock, shares outstanding	29,874,687	29,792,922

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
CONSOLIDATED STATEMENT OF COMPREHENSIVE LOSS
Revenue	$ 3,900	$ 5,039	$ 8,930	$ 8,145
Operating expenses:
Research and development	16,997	13,715	33,899	24,454
General and administrative	6,365	4,710	12,187	8,780
Total operating expenses	23,362	18,425	46,086	33,234
Loss from operations	(19,462)	(13,386)	(37,156)	(25,089)
Other income (expense), net	181	861	805	1,809
Net loss	$ (19,281)	$ (12,525)	$ (36,351)	$ (23,280)
Net loss per share, basic and diluted (in dollars per share)	$ (0.65)	$ (0.48)	$ (1.23)	$ (0.90)
Weighted average common shares outstanding, basic and diluted (in shares)	29,690,280	25,922,833	29,608,814	25,758,658
Comprehensive loss:
Net loss	$ (19,281)	$ (12,525)	$ (36,351)	$ (23,280)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	(185)	42	12	66
Total other comprehensive income (loss)	(185)	42	12	66
Comprehensive loss	$ (19,466)	$ (12,483)	$ (36,339)	$ (23,214)

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					66
Net Loss					(23,280)
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
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, net of issuance costs	$ 3	42,019			42,022
Sale of common shares, net of issuance 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
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					12
Net Loss					(36,351)
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
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

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (36,351)	$ (23,280)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	784	586
Equity-based compensation	4,609	3,432
Amortization/accretion of investment securities	(196)	(694)
Non-cash operating lease expense	523	492
Change in operating assets and liabilities:
Accounts receivable	25,000
Prepaid expenses and other current assets	(1,292)	(1,091)
Other assets	(963)
Accounts payable	1,543	(1,028)
Accrued expenses	(1,377)	(1,771)
Operating lease liabilities	(541)	(378)
Deferred revenue	(8,930)	(8,145)
Other liabilities		(59)
Net cash used in operating activities	(17,191)	(31,936)
Cash flows from investing activities:
Purchases of property and equipment	(283)	(1,279)
Purchases of marketable securities	(19,400)	(77,297)
Maturities of marketable securities	114,700	67,300
Net cash provided by (used in) investing activities	95,017	(11,276)
Cash flows from financing activities:
Principal payments on loan payable		(365)
Proceeds from sale of common stock, net of issuance costs		42,220
Proceeds from stock option exercises	1,003	92
Other	(9)	(6)
Net cash provided by financing activities	994	41,941
Net increase (decrease) in cash and cash equivalents and restricted cash	78,820	(1,271)
Cash and cash equivalents and restricted cash, beginning of period	38,806	115,274
Cash and cash equivalents and restricted cash, end of period	117,626	114,003
Supplemental disclosure of non-cash items:
Property and equipment purchases in accounts payable and accrued expenses	$ 7	27
Offering costs in accounts payable and accrued expenses		198
Operating lease right-of-use asset obtained in exchange for operating lease obligation		$ 5,349

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2020
Nature of the Business and Basis of Presentation
Nature of the Business and Basis of Presentation	1. Nature of the Business Scholar Rock Holding Corporation (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, 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. SRK-015 is being developed as a potential first muscle-directed therapy for the treatment of spinal muscular atrophy (“SMA”). SRK-015 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. 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 and a secondary offering of common stock in June 2019, 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 and cash equivalents, and marketable securities at June 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	6 Months Ended
	Jun. 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 June 30, ​ 2020 2019 Cash and cash equivalents ​ $ 115,128 ​ $ 113,798 Restricted cash ​ 2,498 ​ 205 ​ ​ $ 117,626 ​ $ 114,003 ​ 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	6 Months Ended
	Jun. 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 June 30, 2020 and December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at June 30, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 109,012 ​ $ 109,012 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ ​ 26,048 ​ ​ 26,048 ​ ​ — ​ ​ — Total assets ​ $ 135,060 ​ $ 135,060 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 June 30, 2020 and December 31, 2019. There were no transfers of assets between fair value measurement levels during the three and six months ended June 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 June 30, 2020 and December 31, 2019, due to their short-term nature.

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2020
Marketable Securities
Marketable Securities	4. Marketable Securities The following table summarizes the Company’s investments as of June 30, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 25,999 ​ $ 49 ​ $ — ​ $ 26,048 Total available-for-sale securities ​ $ 25,999 ​ $ 49 ​ $ — ​ $ 26,048 ​ 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	6 Months Ended
	Jun. 30, 2020
Accrued Expenses
Accrued Expenses	5. Accrued Expenses As of June 30, 2020 and December 31, 2019, accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ June 30, December 31, ​ 2020 ​ 2019 Accrued payroll and related expenses ​ $ 3,580 ​ $ 4,380 Accrued external research and development expense ​ ​ 3,277 ​ ​ 4,088 Accrued professional and consulting expense ​ ​ 1,233 ​ ​ 929 Accrued other ​ 143 ​ 213 ​ ​ $ 8,233 ​ $ 9,610 ​

Equity-Based Compensation

Equity-Based Compensation	6 Months Ended
	Jun. 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 for employees and non-employees, which was allocated as follows in the consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2020 2019 2020 2019 Research and development expense ​ $ 887 ​ $ 638 ​ $ 1,702 ​ $ 1,217 General and administrative expense ​ 1,508 ​ 1,176 ​ 2,907 ​ 2,215 ​ ​ $ 2,395 ​ $ 1,814 ​ $ 4,609 ​ $ 3,432 ​ 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 (133,704) ​ $ 5.77 Forfeited (42,010) ​ $ 5.77 Restricted common stock as of June 30, 2020 126,646 ​ $ 5.77 ​ As of June 30, 2020, the Company had unrecognized equity-based compensation expense of $0.6 million related to restricted stock issued to employees and directors, which is expected to be recognized over a period of 1.0 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 1,466,051 ​ $ 14.39 ​ ​ ​ ​ ​ Exercised ​ (123,775) ​ $ 8.10 ​ ​ ​ ​ ​ Cancelled (251,987) ​ $ 13.22 ​ ​ ​ ​ ​ Outstanding as of June 30, 2020 3,491,671 ​ $ 13.49 ​ 8.62 ​ $ 18,205 Options exercisable as of June 30, 2020 1,064,356 ​ $ 12.77 ​ 7.64 ​ $ 6,629 ​ Using the Black-Scholes option pricing model, the weighted average fair value of options granted during the six months ended June 30, 2020 was $10.10. The following weighted average assumptions were used in determining the fair value of options granted in the six months ended June 30, 2020: ​ ​ ​ ​ Risk-free interest rate 1.24 % Expected dividend yield 0.0 % Expected term (years to liquidity) 6.19 ​ Expected volatility 81.86 % ​ As of June 30, 2020, the Company has unrecognized equity-based compensation expense related to its employee stock options of $22.3 million which the Company expects to recognize over the remaining weighted average vesting period of 2.7 years.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
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 facility lease for its corporate headquarters (the “Lease”) at 620 Memorial Drive in Cambridge, Massachusetts. The Lease was amended in February 2018, to add an additional space (the “Expansion Space”) at the current location and to extend the Lease term (the “Amended Lease”). The Amended Lease expires in September 2023. Rent for the facility Lease, including the Expansion Space, increases from $1.4 million a year to $1.7 million a year over the term of the Lease. Variable Lease payments include the Company’s allocated share of costs incurred and expenditures made by the landlord in the operation and management of the building. The Company has the option to extend the term of the Amended Lease for one additional term of 5 years commencing after the Amended Lease expires. ​ Other information related to the Company’s Lease is as follows (in thousands, except lease term and discount rate): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For Three Months Ended ​ For Six Months Ended ​ June 30, June 30, ​ ​ 2020 ​ 2020 Lease Cost: ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 344 ​ $ 687 Variable lease cost ​ ​ 210 ​ ​ 377 Total lease cost ​ $ 554 ​ $ 1,064 ​ ​ ​ ​ ​ ​ For Six Months Ended ​ ​ June 30, ​ ​ 2020 ​ Other information: ​ ​ ​ Operating cash flows used for operating leases $ 706 ​ Weighted average remaining lease term ​ 3.25 years ​ Weighted average incremental borrowing rate ​ 6.47 % ​ The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of June 30, 2020 (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, ​ ​ 2020 (excluding the six months ended June 30, 2020) ​ $ 740 2021 ​ 1,619 2022 ​ 1,668 2023 ​ 1,279 Total lease payments ​ ​ 5,306 Less imputed interest ​ ​ (544) Total operating lease liabilities ​ $ 4,762 ​ 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 the term by two years . The base rent is $6.9 million per year, subject to an increase of 3.5% , and the Company is subject to a free-rent period through mid-August 2020. Variable lease payments include the Company’s allocated share of costs incurred and expenditures made by the landlord in the operation and management of the building. The Company is involved in the construction and design of the space and anticipates that it will incur construction costs of which $14.1 million will be reimbursed through an allowance for tenant improvements. In 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 not reached as of June 30, 2020 and therefore the lease is not included in the Company’s operating lease right-of-use asset or operating lease liabilities as of June 30, 2020. 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 six months ended June 30, 2020 and 2019.

Loan Payable

Loan Payable	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 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 June 30, 2020. A $25 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 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 six months ended June 30, 2020, the Company recognized $3.9 million and $8.9 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 June 30, 2020 is $58.5 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 1.5 years as of June 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	6 Months Ended
	Jun. 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, ​ ​ 2020 2019 Restricted common stock ​ 126,646 ​ 480,663 ​ Warrant ​ 7,614 ​ 7,614 ​ Stock options ​ 3,491,671 ​ 2,423,561 ​ ​ ​ 3,625,931 ​ 2,911,838 ​ ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 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 June 30, ​ 2020 2019 Cash and cash equivalents ​ $ 115,128 ​ $ 113,798 Restricted cash ​ 2,498 ​ 205 ​ ​ $ 117,626 ​ $ 114,003
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)	6 Months Ended
	Jun. 30, 2020
Summary of Significant Accounting Policies
Schedule of reconciles of cash and cash equivalents and restricted cash	​ ​ ​ ​ ​ ​ ​ ​ ​ As of June 30, ​ 2020 2019 Cash and cash equivalents ​ $ 115,128 ​ $ 113,798 Restricted cash ​ 2,498 ​ 205 ​ ​ $ 117,626 ​ $ 114,003

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	6 Months Ended
	Jun. 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 June 30, 2020 and December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at June 30, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 109,012 ​ $ 109,012 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ ​ 26,048 ​ ​ 26,048 ​ ​ — ​ ​ — Total assets ​ $ 135,060 ​ $ 135,060 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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)	6 Months Ended
	Jun. 30, 2020
Marketable Securities
Summary of investments	The following table summarizes the Company’s investments as of June 30, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 25,999 ​ $ 49 ​ $ — ​ $ 26,048 Total available-for-sale securities ​ $ 25,999 ​ $ 49 ​ $ — ​ $ 26,048 ​ 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)	6 Months Ended
	Jun. 30, 2020
Accrued Expenses
Summary of accrued expenses	As of June 30, 2020 and December 31, 2019, accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ June 30, December 31, ​ 2020 ​ 2019 Accrued payroll and related expenses ​ $ 3,580 ​ $ 4,380 Accrued external research and development expense ​ ​ 3,277 ​ ​ 4,088 Accrued professional and consulting expense ​ ​ 1,233 ​ ​ 929 Accrued other ​ 143 ​ 213 ​ ​ $ 8,233 ​ $ 9,610

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	6 Months Ended
	Jun. 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 for employees and non-employees, which was allocated as follows in the consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2020 2019 2020 2019 Research and development expense ​ $ 887 ​ $ 638 ​ $ 1,702 ​ $ 1,217 General and administrative expense ​ 1,508 ​ 1,176 ​ 2,907 ​ 2,215 ​ ​ $ 2,395 ​ $ 1,814 ​ $ 4,609 ​ $ 3,432
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 (133,704) ​ $ 5.77 Forfeited (42,010) ​ $ 5.77 Restricted common stock as of June 30, 2020 126,646 ​ $ 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 1,466,051 ​ $ 14.39 ​ ​ ​ ​ ​ Exercised ​ (123,775) ​ $ 8.10 ​ ​ ​ ​ ​ Cancelled (251,987) ​ $ 13.22 ​ ​ ​ ​ ​ Outstanding as of June 30, 2020 3,491,671 ​ $ 13.49 ​ 8.62 ​ $ 18,205 Options exercisable as of June 30, 2020 1,064,356 ​ $ 12.77 ​ 7.64 ​ $ 6,629
Schedule of fair value assumptions	​ ​ ​ ​ Risk-free interest rate 1.24 % Expected dividend yield 0.0 % Expected term (years to liquidity) 6.19 ​ Expected volatility 81.86 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies
Summary of lease costs	​ Other information related to the Company’s Lease is as follows (in thousands, except lease term and discount rate): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For Three Months Ended ​ For Six Months Ended ​ June 30, June 30, ​ ​ 2020 ​ 2020 Lease Cost: ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 344 ​ $ 687 Variable lease cost ​ ​ 210 ​ ​ 377 Total lease cost ​ $ 554 ​ $ 1,064 ​ ​ ​ ​ ​ ​ For Six Months Ended ​ ​ June 30, ​ ​ 2020 ​ Other information: ​ ​ ​ Operating cash flows used for operating leases $ 706 ​ Weighted average remaining lease term ​ 3.25 years ​ Weighted average incremental borrowing rate ​ 6.47 %
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 June 30, 2020 (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, ​ ​ 2020 (excluding the six months ended June 30, 2020) ​ $ 740 2021 ​ 1,619 2022 ​ 1,668 2023 ​ 1,279 Total lease payments ​ ​ 5,306 Less imputed interest ​ ​ (544) Total operating lease liabilities ​ $ 4,762

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Net Loss per Share
Summary of anti-dilutive securities	​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, ​ ​ 2020 2019 Restricted common stock ​ 126,646 ​ 480,663 ​ Warrant ​ 7,614 ​ 7,614 ​ Stock options ​ 3,491,671 ​ 2,423,561 ​ ​ ​ 3,625,931 ​ 2,911,838 ​

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation (Details)	6 Months Ended
	Jun. 30, 2020item
Nature of the Business and Basis of Presentation
Number of collaborations	2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Cash and cash equivalents and restricted cash
Cash and cash equivalents	$ 115,128	$ 36,308	$ 113,798
Restricted cash	2,498		205
Total	$ 117,626	$ 38,806	$ 114,003	$ 115,274

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Money market funds, included in cash and cash equivalents	$ 109,012	$ 34,896
Marketable securities:
U.S. Treasury obligations	26,048	121,140
Total assets	135,060	156,036
Level 1
Assets:
Money market funds, included in cash and cash equivalents	109,012	34,896
Marketable securities:
U.S. Treasury obligations	26,048	121,140
Total assets	$ 135,060	$ 156,036

Marketable Securities - Summary

Marketable Securities - Summary of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Marketable securities available-for-sale
Amortization Cost	$ 25,999	$ 121,103
Gross Unrealized Gains	49	39
Gross Unrealized Losses		(2)
Estimated Fair Value	26,048	121,140
U.S. Treasury obligations
Marketable securities available-for-sale
Amortization Cost	25,999	121,103
Gross Unrealized Gains	49	39
Gross Unrealized Losses		(2)
Estimated Fair Value	$ 26,048	$ 121,140

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Expenses
Accrued payroll and related expenses	$ 3,580	$ 4,380
Accrued external research and development expense	3,277	4,088
Accrued professional and consulting expense	1,233	929
Accrued other	143	213
Accrued expenses	$ 8,233	$ 9,610

Equity-Based Compensation - Exp

Equity-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity-based compensation
Equity-based compensation expense	$ 2,395	$ 1,814	$ 4,609	$ 3,432
Research and development expense
Equity-based compensation
Equity-based compensation expense	887	638	1,702	1,217
General and administrative expense
Equity-based compensation
Equity-based compensation expense	$ 1,508	$ 1,176	$ 2,907	$ 2,215

Equity-Based Compensation - Res

Equity-Based Compensation - Restricted stock (Details) - Restricted common stock $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares
Number of unvested awards
Outstanding, beginning (in shares) | shares	302,360
Vested (in shares) | shares	(133,704)
Forfeited (in shares) | shares	(42,010)
Outstanding, end (in shares) | shares	126,646
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 | $	$ 0.6
Period for recognition	1 year

Equity-Based Compensation - Sto

Equity-Based Compensation - Stock Options (Details) - Stock options $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Number of Units
Outstanding, beginning (in shares) | shares	2,401,382
Granted (in shares) | shares	1,466,051
Exercised (in shares) | shares	(123,775)
Cancelled (in shares) | shares	(251,987)
Outstanding, end (in shares) | shares	3,491,671	2,401,382
Options exercisable, end (in shares) | shares	1,064,356
Weighted Average Exercise Price
Outstanding, beginning (in dollars per share)	$ 12.63
Granted (in dollars per share)	14.39
Exercised (in dollars per share)	8.10
Cancelled (in dollars per share)	13.22
Outstanding, end (in dollars per share)	13.49	$ 12.63
Options exercisable, end (in dollars per share)	$ 12.77
Stock options
Weighted average remaining contractual term	8 years 7 months 13 days	8 years 4 months 9 days
Weighted average remaining contractual term, exercisable	7 years 7 months 20 days
Aggregate intrinsic value, beginning | $	$ 6,523
Aggregate intrinsic value, end | $	18,205	$ 6,523
Aggregate intrinsic value, exercisable | $	$ 6,629
Weighted average grant date fair value (in dollars per share)	$ 10.10

Equity-Based Compensation - Ass

Equity-Based Compensation - Assumptions (Details) - Stock options $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)
Assumptions used in determining the fair value of options
Risk-free interest rate	1.24%
Expected dividend yield	0.00%
Expected term (years to liquidity)	6 years 2 months 8 days
Expected volatility	81.86%
Unrecognized equity-based compensation expense	$ 22.3
Period for recognition	2 years 8 months 12 days

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Feb. 28, 2018USD ($)item	Jun. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2015
Lease Cost:
Operating lease cost		$ 344	$ 687
Variable lease cost		210	377
Total lease cost		$ 554	1,064
Operating cash flows used for operating leases			$ 706
Weighted average remaining lease term		3 years 3 months	3 years 3 months
Weighted average incremental borrowing rate		6.47%	6.47%
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

Commitments and Contingencies -

Commitments and Contingencies - Maturities (Details) - USD ($) $ in Thousands	1 Months Ended
	Nov. 30, 2019	Jun. 30, 2020	Dec. 20, 2019
Maturity analysis of the annual undiscounted cash flows
2020 (excluding the six months ended June 30, 2020)		$ 740
2021		1,619
2022		1,668
2023		1,279
Total lease payments		5,306
Less imputed interest		(544)
Total operating lease liabilities		$ 4,762
Payment commitment			$ 3,700
301 Binney St, Cambridge MA
Maturity analysis of the annual undiscounted cash flows
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

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 ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)
Agreements
Revenue earned			$ 3,900	$ 5,039	$ 8,930	$ 8,145
Gilead
Agreements
Number of programs | item	3
Option exercise period	90 days
Revenue proceeds		$ 25,000
Revenue earned			$ 3,900		$ 8,900

Agreements - Gilead obligation

Agreements - Gilead obligation period (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01 - Gilead $ in Millions	Jun. 30, 2020USD ($)
Agreements
Contract liability	$ 58.5
Expected to recognize remaining deferred revenue	1 year 6 months

Net Loss per Share - Anti-dilut

Net Loss per Share - Anti-dilutive (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	3,625,931	2,911,838
Restricted common stock
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	126,646	480,663
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	3,491,671	2,423,561