Scholar Rock Holding (SRRK) 10-Q 9 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 04, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
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	301 Binney Street, 3rd Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
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	Non-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		35,108,133
Entity Central Index Key	0001727196
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 176,131	$ 160,358
Marketable securities	70,304	180,673
Prepaid expenses and other current assets	11,721	3,373
Total current assets	258,156	344,404
Property and equipment, net	9,546	8,121
Operating lease right-of-use asset	27,084	32,261
Restricted cash	2,498	2,498
Other long-term assets	1,105	1,021
Total assets	298,389	388,305
Current liabilities:
Accounts payable	2,037	3,409
Accrued expenses	17,898	14,958
Operating lease liability	7,196	5,366
Deferred revenue	37,242	18,816
Other current liabilities	228	15
Total current liabilities	64,601	42,564
Long-term portion of operating lease liability	21,600	27,093
Long-term debt	24,928	24,680
Other long-term liabilities		5
Long-term portion of deferred revenue		33,193
Total liabilities	111,129	127,535
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2021 and December 31, 2020; no shares issued and outstanding at September 30, 2021 and December 31, 2020
Common stock, $0.001 par value; 150,000,000 shares authorized; 34,599,538 and 34,152,470 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	35	34
Additional paid-in capital	527,441	505,069
Accumulated other comprehensive income (loss)		(2)
Accumulated deficit	(340,216)	(244,331)
Total stockholders' equity	187,260	260,770
Total liabilities and stockholders' equity	$ 298,389	$ 388,305

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
CONSOLIDATED BALANCE SHEETS
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	34,599,538	34,152,470
Common stock, shares outstanding	34,599,538	34,152,470

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue	$ 5,464	$ 3,037	$ 14,767	$ 11,967
Operating expenses:
Research and development	31,265	18,383	79,417	52,282
General and administrative	11,276	8,272	29,907	20,459
Total operating expenses	42,541	26,655	109,324	72,741
Loss from operations	(37,077)	(23,618)	(94,557)	(60,774)
Other income (expense), net	(430)	57	(1,328)	862
Net loss	$ (37,507)	$ (23,561)	$ (95,885)	$ (59,912)
Net loss per share, basic (in dollars per share)	$ (1.02)	$ (0.79)	$ (2.62)	$ (2.02)
Net loss per share, diluted (in dollars per share)	$ (1.02)	$ (0.79)	$ (2.62)	$ (2.02)
Weighted average common shares outstanding, basic (in shares)	36,683,026	29,779,114	36,549,833	29,665,995
Weighted average common shares outstanding, diluted (in shares)	36,683,026	29,779,114	36,549,833	29,665,995
Comprehensive loss:
Net loss	$ (37,507)	$ (23,561)	$ (95,885)	$ (59,912)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	(9)	(46)	2	(34)
Total other comprehensive income (loss)	(9)	(46)	2	(34)
Comprehensive loss	$ (37,516)	$ (23,607)	$ (95,883)	$ (59,946)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income/(Loss)	Retained Earnings	Total
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
Balance at beginning at Dec. 31, 2020	$ 34	505,069	(2)	(244,331)	260,770
Balance at beginning (in shares) at Dec. 31, 2020	34,152,470
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			25		25
Exercise of stock options		2,743			2,743
Exercise of stock options (in shares)	245,920
Equity-based compensation expense		4,673			4,673
Net Loss				(27,671)	(27,671)
Balance at end at Mar. 31, 2021	$ 34	512,485	23	(272,002)	240,540
Balance at end (in shares) at Mar. 31, 2021	34,398,390
Balance at beginning at Dec. 31, 2020	$ 34	505,069	(2)	(244,331)	260,770
Balance at beginning (in shares) at Dec. 31, 2020	34,152,470
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities					2
Net Loss					(95,885)
Balance at end at Sep. 30, 2021	$ 35	527,441		(340,216)	187,260
Balance at end (in shares) at Sep. 30, 2021	34,599,538
Balance at beginning at Mar. 31, 2021	$ 34	512,485	23	(272,002)	240,540
Balance at beginning (in shares) at Mar. 31, 2021	34,398,390
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			(14)		(14)
Exercise of stock options		611			611
Exercise of stock options (in shares)	61,397
Equity-based compensation expense		6,226			6,226
Net Loss				(30,707)	(30,707)
Balance at end at Jun. 30, 2021	$ 34	519,322	9	(302,709)	216,656
Balance at end (in shares) at Jun. 30, 2021	34,459,787
Increase (decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities			$ (9)		(9)
Exercise of stock options	$ 1	1,965			1,966
Exercise of stock options (in shares)	139,751
Equity-based compensation expense		6,154			6,154
Net Loss				(37,507)	(37,507)
Balance at end at Sep. 30, 2021	$ 35	$ 527,441		$ (340,216)	$ 187,260
Balance at end (in shares) at Sep. 30, 2021	34,599,538

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (95,885)	$ (59,912)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,900	1,172
Amortization of debt discount and debt issuance costs	248
Loss on sale of property and equipment	24
Equity-based compensation	17,053	8,645
Amortization/accretion of investment securities	808	(188)
Non-cash operating lease expense	4,755	791
Change in operating assets and liabilities:
Accounts receivable		25,000
Prepaid expenses and other current assets	(7,876)	(4,197)
Other assets	(84)	(952)
Accounts payable	(1,194)	(24)
Accrued expenses	4,120	1,864
Operating lease liabilities	(3,663)	(818)
Deferred revenue	(14,767)	(11,967)
Other liabilities	227
Net cash used in operating activities	(94,334)	(40,586)
Cash flows from investing activities:
Purchases of property and equipment	(4,706)	(2,114)
Purchases of marketable securities	(60,437)	(79,443)
Maturities of marketable securities	170,000	140,700
Net cash provided by investing activities	104,857	59,143
Cash flows from financing activities:
Proceeds from stock option exercises	5,269	1,377
Other	(19)	(15)
Net cash provided by financing activities	5,250	1,362
Net increase in cash and cash equivalents and restricted cash	15,773	19,919
Cash and cash equivalents and restricted cash, beginning of period	162,856	38,806
Cash and cash equivalents and restricted cash, end of period	178,629	58,725
Supplemental disclosure of non-cash items:
Property and equipment purchases in accounts payable and accrued expenses	10	424
Operating lease right-of-use asset obtained in exchange for operating lease obligation		$ 31,286
Supplemental cash flow information:
Cash paid for interest	$ 1,494

Nature of the Business

Nature of the Business	9 Months Ended
	Sep. 30, 2021
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 (formerly SRK-015), is a 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 was evaluated in the Company’s TOPAZ Phase 2 proof-of-concept trial for the treatment of patients with Type 2 and Type 3 SMA and positive 12-month top-line results were announced in April 2021 demonstrating apitegromab’s transformative potential. A randomized, double-blind, placebo-controlled Phase 3 trial in patients with non-ambulatory Type 2 and 3 SMA is anticipated to initiate by year-end 2021. 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-L1 antibody therapies. SRK-181 is a selective inhibitor of the activation of latent transforming growth factor beta-1 (“TGFβ1”) that is being investigated in the DRAGON Phase 1 proof-of-concept trial in patients with locally advanced or metastatic solid tumors that exhibit primary resistance to anti-PD-(L)1 antibodies. The Company continues to progress the Part A dose escalation portion of the DRAGON trial and has initiated the Part B dose expansion portion of the trial to evaluate SRK-181 in combination with approved anti-PD-(L)1 therapies in multiple solid tumors, including non-small cell lung cancer, urothelial carcinoma, and cutaneous melanoma. 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, and fibrosis. 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, 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”). 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, 2021 will be sufficient to allow the Company to fund its current operations through at least a period of one year after the date these financial statements are issued.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
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, 2020, 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, 2020. ​ Cash, Cash Equivalents and Restricted Cash ​ The following table reconciles cash, cash equivalents and restricted cash per the balance sheet to the statement of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, ​ 2021 2020 Cash and cash equivalents ​ $ 176,131 ​ $ 56,227 Restricted cash ​ 2,498 ​ 2,498 ​ ​ $ 178,629 ​ $ 58,725 ​ 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 Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	9 Months Ended
	Sep. 30, 2021
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, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at September 30, 2021 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 158,177 ​ $ 158,177 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ ​ 70,304 ​ ​ 70,304 ​ ​ — ​ ​ — Total assets ​ $ 228,481 ​ $ 228,481 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 119,841 ​ $ 119,841 ​ $ — ​ $ — U.S. Treasury obligations, included in cash and cash equivalents ​ ​ 9,998 ​ ​ 9,998 ​ ​ — ​ ​ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ 180,673 ​ 180,673 ​ — ​ — Total assets ​ $ 310,512 ​ $ 310,512 ​ $ — ​ $ — ​ Cash, cash equivalents and marketable securities are Level 1 assets and 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, 2021 and December 31, 2020. There were no transfers of assets between fair value measurement levels during the three and nine months ended September 30, 2021 or 2020. The carrying amounts reflected in the balance sheets for prepaid expenses and other current assets, accounts payable, and accrued expenses approximate their fair values at September 30, 2021 and December 31, 2020, due to their short-term nature. The Company believes the terms of its debt reflect current market conditions for an instrument with similar terms and maturity, therefore the carrying value of the Company's debt approximates its fair value based on Level 3 of the fair value hierarchy.

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2021
Marketable Securities
Marketable Securities	4. Marketable Securities The following table summarizes the Company’s investments as of September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 70,304 ​ $ 3 ​ $ (3) ​ $ 70,304 Total available-for-sale securities ​ $ 70,304 ​ $ 3 ​ $ (3) ​ $ 70,304 ​ The following table summarizes the Company’s investments as of December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 180,675 ​ $ 7 ​ $ (9) ​ $ 180,673 Total available-for-sale securities ​ $ 180,675 ​ $ 7 ​ $ (9) ​ $ 180,673 ​

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2021
Accrued Expenses
Accrued Expenses	5. Accrued Expenses As of September 30, 2021 and December 31, 2020, accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, December 31, ​ 2021 ​ 2020 Accrued external research and development expense ​ $ 9,024 ​ $ 5,387 Accrued payroll and related expenses ​ ​ 6,959 ​ ​ 6,663 Accrued professional and consulting expense ​ ​ 1,524 ​ ​ 1,141 Accrued other ​ ​ 381 ​ ​ 476 Accrued payable for property and equipment ​ 10 ​ 1,291 ​ ​ $ 17,898 ​ $ 14,958 ​

Equity-Based Compensation

Equity-Based Compensation	9 Months Ended
	Sep. 30, 2021
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, 2021 and 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2021 2020 2021 2020 Research and development expense ​ $ 2,482 ​ $ 900 ​ $ 7,440 ​ $ 2,602 General and administrative expense ​ 3,672 ​ 3,136 ​ 9,613 ​ 6,043 ​ ​ $ 6,154 ​ $ 4,036 ​ $ 17,053 ​ $ 8,645 ​ 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. ​ The following table summarizes the Company’s unrecognized equity-based compensation expense as of September 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2021 ​ ​ Unrecognized Expense (in thousands) Weighted Average Remaining Period of Recognition (years) Restricted Stock Awards $ 4 ​ 0.1 Restricted Stock Units ​ 11,652 ​ 3.4 Stock Options ​ 48,032 ​ 2.5 ​ $ 59,688 ​ ​ ​ Restricted Stock Awards The following table summarizes the Company’s restricted stock award activity for the current year: ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Fair ​ ​ ​ ​ Value per Share ​ Number of Shares at Issuance Restricted stock awards as of December 31, 2020 57,969 ​ $ 5.77 Vested (53,584) ​ $ 5.77 Restricted stock awards as of September 30, 2021 4,385 ​ $ 5.77 ​ Restricted Stock Units The following table summarizes the Company’s restricted stock unit activity for the current year: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Grant ​ Number of Units Date Fair Value Restricted stock units as of December 31, 2020 — ​ $ — Granted 316,416 ​ $ 54.91 Forfeited (62,260) ​ $ 58.95 Restricted stock units as of September 30, 2021 254,156 ​ $ 53.92 ​ 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, 2020 3,679,931 ​ $ 14.96 ​ 8.01 ​ $ 123,600 Granted 1,208,780 ​ $ 53.91 ​ ​ ​ ​ ​ Exercised ​ (447,068) ​ $ 11.90 ​ ​ ​ ​ ​ Cancelled (705,014) ​ $ 28.38 ​ ​ ​ ​ ​ Outstanding as of September 30, 2021 3,736,629 ​ $ 25.40 ​ 8.04 ​ $ 50,608 Options exercisable as of September 30, 2021 1,427,696 ​ $ 17.87 ​ 7.33 ​ $ 24,530 ​ Using the Black-Scholes option pricing model, the weighted average fair value of options granted during the nine months ended September 30, 2021 was $39.51. The following weighted average assumptions were used in determining the fair value of options granted in the nine months ended September 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ ​ 2021 2020 ​ Risk-free interest rate 0.77 % 0.95 % Expected dividend yield 0.0 % 0.0 % Expected term (years to liquidity) 6.21 ​ 6.21 ​ Expected volatility 87.79 % 81.65 % ​

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
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 lease of office and laboratory space 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 covers approximately 20,751 square feet and expires in September 2023. Annual rent payments, including the Expansion Space, increase from $1.4 million to $1.7 million over the term of the Amended 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. ​ On October 5, 2020, the Company entered into a Sublease Agreement (the “Sublease”) with Orna Therapeutics, Inc. (the “Subtenant”) to sublease the space covered by the Amended Lease at 620 Memorial Drive, Cambridge, Massachusetts. The Sublease term commenced on February 1, 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 is 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. 301 Binney Facility Lease ​ In November 2019, the Company entered into a lease of office and laboratory space 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 annual increase of 3.5%, and the Company was 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 lease included incentives of $14.1 million in the form of an allowance for tenant improvements related to the design and build out of the space, all of which the Company received as of September 30, 2021. In connection with the lease, the Company has secured a letter of credit for ​ Other information related to the Company’s leases (excluding the Company’s sublease income of $0.7 million and $1.6 million for the three and nine months ended September 30, 2021, respectively) is as follows (in thousands, except lease term and discount rate): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For Three Months Ended ​ For Nine Months Ended ​ September 30, September 30, ​ ​ 2021 ​ 2021 Lease Cost: ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 2,161 ​ $ 6,473 Variable lease cost ​ ​ 516 ​ ​ 1,669 Total lease cost ​ $ 2,677 ​ $ 8,142 ​ ​ ​ ​ ​ ​ For Nine Months Ended ​ ​ September 30, ​ ​ 2021 ​ Other information: ​ ​ ​ Operating cash flows used for operating leases $ 6,617 ​ Weighted average remaining lease term ​ 3.7 years ​ Weighted average incremental borrowing rate ​ 7.5 % ​ 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. As of September 30, 2021 the Company has paid $2.0 million of the total $3.7 million in fees expected to be paid through 2023 related to the Library. As the return right has lapsed, all $3.7 million in fees have been recognized as expense to date. ​ 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, 2021 and 2020.

Debt

Debt	9 Months Ended
	Sep. 30, 2021
Debt
Debt	8. Debt 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. ​

Agreements

Agreements	9 Months Ended
	Sep. 30, 2021
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 transforming growth factor beta (“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 (no later than March 19, 2022), 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 Sepember 30, 2021. 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, 2021, the Company recognized $5.5 million and $14.8 million, respectively, in revenue in the Company’s consolidated statements of operations and comprehensive loss under the Gilead Collaboration Agreement, and all of which was included in deferred revenue at the beginning of the respective periods. A significant portion of the revenue in the three months ended September 30, 2021 is the result of a decrease in the total estimated costs expected to be incurred primarily due to the extent of research and development services remaining to be provided which were impacted by COVID-19 supply chain limitations. The aggregate amount of the transaction price allocated to the Company’s unsatisfied performance obligations and recorded in deferred revenue at September 30, 2021 is $37.2 million. The Company will recognize the remaining $4.0 million of 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 ends in the fourth quarter of 2021; 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 $33.2 million of deferred revenue related to the material rights will be recognized if and when 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, 2021
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 weighted average number of common shares used in the basic and diluted net loss per share calculation include the pre-funded warrants issued in connection with the Company’s November 2, 2020 follow-on offering as the warrants are exercisable at any time for nominal cash consideration. As of September 30, 2021 no pre-funded warrants have been exercised and 2,179,487 pre-funded warrants are outstanding. 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, ​ 2021 2020 Restricted stock awards ​ 4,385 ​ 86,116 Restricted stock units ​ 254,156 ​ — Warrant ​ — ​ 7,614 Stock options ​ 3,736,629 ​ 4,139,239 ​ ​ 3,995,170 ​ 4,232,969 ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Summary of Significant Accounting Policies
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash ​ The following table reconciles cash, cash equivalents and restricted cash per the balance sheet to the statement of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, ​ 2021 2020 Cash and cash equivalents ​ $ 176,131 ​ $ 56,227 Restricted cash ​ 2,498 ​ 2,498 ​ ​ $ 178,629 ​ $ 58,725
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 Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Summary of Significant Accounting Policies
Schedule of reconciles of cash, cash equivalents and restricted cash	​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, ​ 2021 2020 Cash and cash equivalents ​ $ 176,131 ​ $ 56,227 Restricted cash ​ 2,498 ​ 2,498 ​ ​ $ 178,629 ​ $ 58,725

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
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, 2021 and December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at September 30, 2021 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 158,177 ​ $ 158,177 ​ $ — ​ $ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ ​ 70,304 ​ ​ 70,304 ​ ​ — ​ ​ — Total assets ​ $ 228,481 ​ $ 228,481 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at December 31, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, included in cash and cash equivalents ​ $ 119,841 ​ $ 119,841 ​ $ — ​ $ — U.S. Treasury obligations, included in cash and cash equivalents ​ ​ 9,998 ​ ​ 9,998 ​ ​ — ​ ​ — Marketable securities: ​ ​ ​ ​ U.S. Treasury obligations ​ 180,673 ​ 180,673 ​ — ​ — Total assets ​ $ 310,512 ​ $ 310,512 ​ $ — ​ $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Marketable Securities
Summary of investments	The following table summarizes the Company’s investments as of September 30, 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 70,304 ​ $ 3 ​ $ (3) ​ $ 70,304 Total available-for-sale securities ​ $ 70,304 ​ $ 3 ​ $ (3) ​ $ 70,304 ​ The following table summarizes the Company’s investments as of December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Estimated ​ Cost Gains Losses Fair Value Marketable securities available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury obligations ​ $ 180,675 ​ $ 7 ​ $ (9) ​ $ 180,673 Total available-for-sale securities ​ $ 180,675 ​ $ 7 ​ $ (9) ​ $ 180,673

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2021
Accrued Expenses
Summary of accrued expenses	As of September 30, 2021 and December 31, 2020, accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ September 30, December 31, ​ 2021 ​ 2020 Accrued external research and development expense ​ $ 9,024 ​ $ 5,387 Accrued payroll and related expenses ​ ​ 6,959 ​ ​ 6,663 Accrued professional and consulting expense ​ ​ 1,524 ​ ​ 1,141 Accrued other ​ ​ 381 ​ ​ 476 Accrued payable for property and equipment ​ 10 ​ 1,291 ​ ​ $ 17,898 ​ $ 14,958

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
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, 2021 and 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2021 2020 2021 2020 Research and development expense ​ $ 2,482 ​ $ 900 ​ $ 7,440 ​ $ 2,602 General and administrative expense ​ 3,672 ​ 3,136 ​ 9,613 ​ 6,043 ​ ​ $ 6,154 ​ $ 4,036 ​ $ 17,053 ​ $ 8,645
Summary of unrecognized equity-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2021 ​ ​ Unrecognized Expense (in thousands) Weighted Average Remaining Period of Recognition (years) Restricted Stock Awards $ 4 ​ 0.1 Restricted Stock Units ​ 11,652 ​ 3.4 Stock Options ​ 48,032 ​ 2.5 ​ $ 59,688 ​ ​
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, 2020 3,679,931 ​ $ 14.96 ​ 8.01 ​ $ 123,600 Granted 1,208,780 ​ $ 53.91 ​ ​ ​ ​ ​ Exercised ​ (447,068) ​ $ 11.90 ​ ​ ​ ​ ​ Cancelled (705,014) ​ $ 28.38 ​ ​ ​ ​ ​ Outstanding as of September 30, 2021 3,736,629 ​ $ 25.40 ​ 8.04 ​ $ 50,608 Options exercisable as of September 30, 2021 1,427,696 ​ $ 17.87 ​ 7.33 ​ $ 24,530
Schedule of fair value assumptions	​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ ​ 2021 2020 ​ Risk-free interest rate 0.77 % 0.95 % Expected dividend yield 0.0 % 0.0 % Expected term (years to liquidity) 6.21 ​ 6.21 ​ Expected volatility 87.79 % 81.65 %
Restricted stock awards
Equity-Based Compensation
Summary of restricted common stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Fair ​ ​ ​ ​ Value per Share ​ Number of Shares at Issuance Restricted stock awards as of December 31, 2020 57,969 ​ $ 5.77 Vested (53,584) ​ $ 5.77 Restricted stock awards as of September 30, 2021 4,385 ​ $ 5.77
Restricted Stock Units
Equity-Based Compensation
Summary of restricted common stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Grant ​ Number of Units Date Fair Value Restricted stock units as of December 31, 2020 — ​ $ — Granted 316,416 ​ $ 54.91 Forfeited (62,260) ​ $ 58.95 Restricted stock units as of September 30, 2021 254,156 ​ $ 53.92

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies
Summary of lease costs	Other information related to the Company’s leases (excluding the Company’s sublease income of $0.7 million and $1.6 million for the three and nine months ended September 30, 2021, respectively) is as follows (in thousands, except lease term and discount rate): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For Three Months Ended ​ For Nine Months Ended ​ September 30, September 30, ​ ​ 2021 ​ 2021 Lease Cost: ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 2,161 ​ $ 6,473 Variable lease cost ​ ​ 516 ​ ​ 1,669 Total lease cost ​ $ 2,677 ​ $ 8,142 ​ ​ ​ ​ ​ ​ For Nine Months Ended ​ ​ September 30, ​ ​ 2021 ​ Other information: ​ ​ ​ Operating cash flows used for operating leases $ 6,617 ​ Weighted average remaining lease term ​ 3.7 years ​ Weighted average incremental borrowing rate ​ 7.5 % ​

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Net Loss per Share
Summary of anti-dilutive securities	​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ 2021 2020 Restricted stock awards ​ 4,385 ​ 86,116 Restricted stock units ​ 254,156 ​ — Warrant ​ — ​ 7,614 Stock options ​ 3,736,629 ​ 4,139,239 ​ ​ 3,995,170 ​ 4,232,969

Nature of the Business (Details

Nature of the Business (Details)	9 Months Ended
	Sep. 30, 2021item
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, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cash and cash equivalents and restricted cash
Cash and cash equivalents	$ 176,131	$ 160,358	$ 56,227
Restricted cash	2,498		2,498
Total	$ 178,629	$ 162,856	$ 58,725	$ 38,806

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Marketable securities:
U.S. Treasury obligations	$ 70,304	$ 180,673
Total assets	228,481	310,512
Money market funds
Assets:
Cash and cash equivalents	158,177	119,841
U.S. Treasury obligations
Assets:
Cash and cash equivalents		9,998
Level 1
Marketable securities:
U.S. Treasury obligations	70,304	180,673
Total assets	228,481	310,512
Level 1 | Money market funds
Assets:
Cash and cash equivalents	$ 158,177	119,841
Level 1 | U.S. Treasury obligations
Assets:
Cash and cash equivalents		$ 9,998

Marketable Securities - Summary

Marketable Securities - Summary of Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Marketable securities available-for-sale
Amortization Cost	$ 70,304	$ 180,675
Gross Unrealized Gains	3	7
Gross Unrealized Losses	(3)	(9)
Estimated Fair Value	70,304	180,673
U.S. Treasury obligations
Marketable securities available-for-sale
Amortization Cost	70,304	180,675
Gross Unrealized Gains	3	7
Gross Unrealized Losses	(3)	(9)
Estimated Fair Value	$ 70,304	$ 180,673

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued Expenses
Accrued external research and development expense	$ 9,024	$ 5,387
Accrued payroll and related expenses	6,959	6,663
Accrued professional and consulting expense	1,524	1,141
Accrued other	381	476
Accrued payable for property and equipment	10	1,291
Accrued expenses	$ 17,898	$ 14,958

Equity-Based Compensation - Exp

Equity-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Equity-based compensation
Equity-based compensation expense	$ 6,154	$ 4,036	$ 17,053	$ 8,645
Modification of equity awards expense		1,500		1,500
Research, development and engineering
Equity-based compensation
Equity-based compensation expense	2,482	900	7,440	2,602
General and administrative expense
Equity-based compensation
Equity-based compensation expense	$ 3,672	$ 3,136	$ 9,613	$ 6,043

Equity-Based Compensation - Unr

Equity-Based Compensation - Unrecognized Expense (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Equity-based compensation
Unrecognized Expense	$ 59,688
Restricted stock awards
Equity-based compensation
Unrecognized Expense	$ 4
Weighted Average Remaining Period of Recognition	1 month 6 days
Restricted Stock Units
Equity-based compensation
Unrecognized Expense	$ 11,652
Weighted Average Remaining Period of Recognition	3 years 4 months 24 days
Stock Options
Equity-based compensation
Unrecognized Expense	$ 48,032
Weighted Average Remaining Period of Recognition	2 years 6 months

Equity-Based Compensation - Res

Equity-Based Compensation - Restricted stock (Details)	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Restricted stock awards
Number of Shares/Units
Outstanding, beginning (in shares) | shares	57,969
Vested (in shares) | shares	(53,584)
Outstanding, end (in shares) | shares	4,385
Weighted Average Fair Value
Outstanding, beginning (in dollars per share) | $ / shares	$ 5.77
Vested (in dollars per share) | $ / shares	5.77
Outstanding, end (in dollars per share) | $ / shares	$ 5.77
Weighted Average Remaining Period of Recognition	1 month 6 days
Restricted Stock Units
Number of Shares/Units
Granted (in shares) | shares	316,416
Forfeited (in shares) | shares	(62,260)
Outstanding, end (in shares) | shares	254,156
Weighted Average Fair Value
Granted (in dollars per share) | $ / shares	$ 54.91
Forfeited (in dollars per share) | $ / shares	58.95
Outstanding, end (in dollars per share) | $ / shares	$ 53.92
Weighted Average Remaining Period of Recognition	3 years 4 months 24 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, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Number of Units
Outstanding, beginning (in shares) | shares	3,679,931
Granted (in shares) | shares	1,208,780
Exercised (in shares) | shares	(447,068)
Cancelled (in shares) | shares	(705,014)
Outstanding, end (in shares) | shares	3,736,629	3,679,931
Options exercisable, end (in shares) | shares	1,427,696
Weighted Average Exercise Price
Outstanding, beginning (in dollars per share)	$ 14.96
Granted (in dollars per share)	53.91
Exercised (in dollars per share)	11.90
Cancelled (in dollars per share)	28.38
Outstanding, end (in dollars per share)	25.40	$ 14.96
Options exercisable, end (in dollars per share)	$ 17.87
Stock options
Weighted average remaining contractual term	8 years 14 days	8 years 3 days
Weighted average remaining contractual term, exercisable	7 years 3 months 29 days
Aggregate intrinsic value, beginning | $	$ 123,600
Aggregate intrinsic value, end | $	50,608	$ 123,600
Aggregate intrinsic value, exercisable | $	$ 24,530
Weighted average grant date fair value (in dollars per share)	$ 39.51

Equity-Based Compensation - Ass

Equity-Based Compensation - Assumptions (Details) - Stock Options	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Assumptions used in determining the fair value of options
Risk-free interest rate	0.77%	0.95%
Expected dividend yield	0.00%	0.00%
Expected term (years to liquidity)	6 years 2 months 15 days	6 years 2 months 15 days
Expected volatility	87.79%	81.65%
Weighted Average Remaining Period of Recognition	2 years 6 months

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Thousands	Oct. 05, 2020USD ($)	Dec. 20, 2019USD ($)	Nov. 30, 2019USD ($)	Feb. 28, 2018USD ($)ft²	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)	Jan. 31, 2018USD ($)	Mar. 31, 2015
Leased assets
Sublease income					$ 700	$ 1,600
Lease Cost:
Operating lease cost					2,161	6,473
Variable lease cost					516	1,669
Total lease cost					$ 2,677	8,142
Operating cash flows used for operating leases						$ 6,617
Weighted average remaining lease term					3 years 8 months 12 days	3 years 8 months 12 days
Weighted average incremental borrowing rate					7.50%	7.50%
Payment made on commitment						$ 2,000
Payment commitment		$ 3,700
Antibody library expense		$ 3,700
620 Memorial Drive, Cambridge MA
Leased assets
Term of lease								5 years
Option to extend the term				true
Area of lease space | ft²				20,751
Annual rent payments				$ 1,700			$ 1,400
Renewal term				5 years
Sublease annual base rent	$ 1,900
301 Binney St, Cambridge MA
Leased assets
Option to extend the term			true
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

Debt (Details)

Debt (Details) - Loan and Security Agreement $ in Millions	Oct. 16, 2020USD ($)
Debt
Line of credit maximum	$ 50
Proceeds from credit facility	25
Remaining borrowing capacity	$ 25
Interest only period	2 years
Variable rate (as a percent)	7.85%
Final payment fee (as a percent)	4.00%
Financing receivable, lower range of payment terms
Debt
Prepayment penalty (as a percent)	2.00%
Financing receivable, upper range of payment terms
Debt
Prepayment penalty (as a percent)	3.00%
Wall Street Journal prime rate
Debt
Variable rate (as a percent)	4.60%

Agreements - Gilead (Details)

Agreements - Gilead (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Agreements
Revenue earned		$ 5,464	$ 3,037	$ 14,767	$ 11,967
Gilead
Agreements
Revenue proceeds	$ 25,000
Revenue earned		5,500
Transaction price		$ 37,200		$ 37,200

Agreements - Gilead obligation

Agreements - Gilead obligation period (Details) - Gilead $ in Millions	Sep. 30, 2021USD ($)
Agreements
Revenue remaining performance obligation amount	$ 37.2
Research and development services
Agreements
Revenue remaining performance obligation amount	4
Material rights
Agreements
Revenue remaining performance obligation amount	$ 33.2

Net Loss per Share (Details)

Net Loss per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Anti-dilutive securities
Outstanding warrants	2,179,487
Anti-dilutive securities excluded from the calculation of net loss per share	3,995,170	4,232,969
Restricted stock awards
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	4,385	86,116
Restricted Stock Units
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	254,156
Warrant
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share		7,614
Stock Options
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	3,736,629	4,139,239