0001558370-21-011162 | 10-Q | XBRL Viewer | Scholar Rock Holding Corp

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2021	Aug. 04, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 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		34,460,597
Entity Central Index Key	0001727196
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 206,919	$ 160,358
Marketable securities	75,298	180,673
Prepaid expenses and other current assets	8,149	3,373
Total current assets	290,366	344,404
Property and equipment, net	9,433	8,121
Operating lease right-of-use asset	28,733	32,261
Restricted cash	2,498	2,498
Other long-term assets	1,021	1,021
Total assets	332,051	388,305
Current liabilities:
Accounts payable	1,627	3,409
Accrued expenses	15,454	14,958
Operating lease liability	6,999	5,366
Deferred revenue	42,706	18,816
Other current liabilities	236	15
Total current liabilities	67,022	42,564
Long-term portion of operating lease liability	23,523	27,093
Long-term debt	24,847	24,680
Other long-term liabilities	3	5
Long-term portion of deferred revenue		33,193
Total liabilities	115,395	127,535
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2021 and December 31, 2020; no shares issued and outstanding at June 30, 2021 and December 31, 2020
Common stock, $0.001 par value; 150,000,000 shares authorized; 34,459,787 and 34,152,470 shares issued and outstanding as of June 30, 2021 and December 31, 2020, respectively	34	34
Additional paid-in capital	519,322	505,069
Accumulated other comprehensive income (loss)	9	(2)
Accumulated deficit	(302,709)	(244,331)
Total stockholders' equity	216,656	260,770
Total liabilities and stockholders' equity	$ 332,051	$ 388,305

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 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	34,459,787	34,152,470
Common stock, shares outstanding	34,459,787	34,152,470

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue	$ 4,595	$ 3,900	$ 9,303	$ 8,930
Operating expenses:
Research and development	25,603	16,997	48,152	33,899
General and administrative	9,265	6,365	18,631	12,187
Total operating expenses	34,868	23,362	66,783	46,086
Loss from operations	(30,273)	(19,462)	(57,480)	(37,156)
Other income (expense), net	(434)	181	(898)	805
Net loss	$ (30,707)	$ (19,281)	$ (58,378)	$ (36,351)
Net loss per share, basic and diluted	$ (0.84)	$ (0.65)	$ (1.60)	$ (1.23)
Weighted average common shares outstanding, basic and diluted	36,582,708	29,690,280	36,482,132	29,608,814
Comprehensive loss:
Net loss	$ (30,707)	$ (19,281)	$ (58,378)	$ (36,351)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	(14)	(185)	11	12
Total other comprehensive income (loss)	(14)	(185)	11	12
Comprehensive loss	$ (30,721)	$ (19,466)	$ (58,367)	$ (36,339)

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	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					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
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					11
Net Loss					(58,378)
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
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

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22595-107794

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669625-108580

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22583-107794

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22658-107794

+ Details

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References + Details

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss	$ (58,378)	$ (36,351)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,227	784
Amortization of debt discount and debt issuance costs	167
Loss on sale of property and equipment	24
Equity-based compensation	10,899	4,609
Amortization/accretion of investment securities	517	(196)
Non-cash operating lease expense	3,107	523
Change in operating assets and liabilities:
Accounts receivable		25,000
Prepaid expenses and other current assets	(4,355)	(1,292)
Other assets		(963)
Accounts payable	(1,779)	1,543
Accrued expenses	1,227	(1,377)
Operating lease liabilities	(1,937)	(541)
Deferred revenue	(9,303)	(8,930)
Other liabilities	227
Net cash used in operating activities	(58,357)	(17,191)
Cash flows from investing activities:
Purchases of property and equipment	(3,295)	(283)
Purchases of marketable securities	(30,131)	(19,400)
Maturities of marketable securities	135,000	114,700
Net cash provided by investing activities	101,574	95,017
Cash flows from financing activities:
Proceeds from stock option exercises	3,354	1,003
Other	(10)	(9)
Net cash provided by financing activities	3,344	994
Net increase in cash and cash equivalents and restricted cash	46,561	78,820
Cash and cash equivalents and restricted cash, beginning of period	162,856	38,806
Cash and cash equivalents and restricted cash, end of period	209,417	117,626
Supplemental disclosure of non-cash items:
Property and equipment purchases in accounts payable and accrued expenses	635	$ 7
Supplemental cash flow information:
Cash paid for interest	$ 992

Nature of the Business

6 Months Ended

Jun. 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 is progressing the Part A dose escalation portion of the DRAGON trial and plans to advance to Part B dose expansion in mid-2021. 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 June 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 the financial statements are issued.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 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 June 30,
	2021		2020
Cash and cash equivalents	$	206,919	$	115,128
Restricted cash		2,498		2,498
	$	209,417	$	117,626

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. The standard requires that a financial asset or a group of financial assets measured at amortized cost basis to be presented at the net amount expected to be collected. Under current GAAP, a company only considered past events and current conditions in measuring an incurred loss. Under ASU 2016-13, the information that a company must consider is broadened in developing an expected credit loss estimate for assets measured either collectively or individually. The use of forecasted information incorporates more timely information in the estimate of expected credit loss. The guidance is applied using a modified retrospective, or prospective approach, depending on a specific amendment. In November 2019, the FASB deferred the effective date for smaller reporting companies to fiscal years beginning after December 15, 2022. The Company does not anticipate a material impact to its net financial position or disclosures as a result of the adoption of ASU 2016-13.

Fair Value of Financial Assets and Liabilities

6 Months Ended

Jun. 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 June 30, 2021 and December 31, 2020 (in thousands):


	Fair Value Measurements at June 30, 2021
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds, included in cash and cash equivalents	$	199,238	$	199,238	$	—	$	—
Marketable securities:
U.S. Treasury obligations		75,298		75,298		—		—
Total assets	$	274,536	$	274,536	$	—	$	—


	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 June 30, 2021 and December 31, 2020. There were no transfers of assets between fair value measurement levels during the three and six months ended June 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 June 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.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Marketable Securities

6 Months Ended

Jun. 30, 2021

Marketable Securities

Marketable Securities

4. Marketable Securities

The following table summarizes the Company’s investments as of June 30, 2021 (in thousands):


			Gross
	Amortized		Unrealized				Estimated
	Cost		Gains		Losses		Fair Value
Marketable securities available-for-sale:
U.S. Treasury obligations	$	75,289	$	9	$	—	$	75,298
Total available-for-sale securities	$	75,289	$	9	$	—	$	75,298

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

6 Months Ended

Jun. 30, 2021

Accrued Expenses

Accrued Expenses

5. Accrued Expenses

As of June 30, 2021 and December 31, 2020, accrued expenses consist of the following (in thousands):


	As of
	June 30,		December 31,
	2021		2020
Accrued external research and development expense	$	9,059	$	5,387
Accrued payroll and related expenses		4,231		6,663
Accrued professional and consulting expense		1,154		1,141
Accrued other		552		476
Accrued payable for property and equipment		458		1,291
	$	15,454	$	14,958

Equity-Based Compensation

6 Months Ended

Jun. 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 six months ended June 30, 2021 and 2020 (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
Research and development expense	$	2,847	$	887	$	4,958	$	1,702
General and administrative expense		3,379		1,508		5,941		2,907
	$	6,226	$	2,395	$	10,899	$	4,609

The following table summarizes the Company’s unrecognized equity-based compensation expense as of June 30, 2021:



	As of June 30, 2021
		Unrecognized Expense (in thousands)	Weighted Average Remaining Period of Recognition (years)
Restricted Stock Awards	$	28	0.3
Restricted Stock Units		13,783	3.6
Stock Options		57,333	2.7
	$	71,144

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	(48,582)	$	5.77
Restricted stock awards as of June 30, 2021	9,387	$	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	281,786	$	57.28
Forfeited	(14,305)	$	59.44
Restricted stock units as of June 30, 2021	267,481	$	57.17

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	1,093,355	$	55.85
Exercised	(307,317)	$	10.91
Cancelled	(142,959)	$	28.47
Outstanding as of June 30, 2021	4,323,010	$	25.14	8.10	$	46,787
Options exercisable as of June 30, 2021	1,148,376	$	16.87	7.47	$	15,525

Using the Black-Scholes option pricing model, the weighted average fair value of options granted during the six months ended June 30, 2021 was $40.93.

The following weighted average assumptions were used in determining the fair value of options granted in the six months ended June 30, 2021 and 2020:


	Six Months Ended
	June 30,
	2021		2020
Risk-free interest rate	0.74	%	1.24	%
Expected dividend yield	0.0	%	0.0	%
Expected term (years to liquidity)	6.21		6.19
Expected volatility	87.89	%	81.86	%

Commitments and Contingencies

6 Months Ended

Jun. 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. Under this lease, the Company will receive lease incentives of $14.1 million in the form of an allowance for tenant improvements related to the design and build out of the space, of which the Company has received $14.0 million as of June 30, 2021. In connection with the lease, the Company has secured a letter of credit for $2.3 million which renews automatically each year. The lease commencement date, for accounting purposes, was reached in September 2020.

Other information related to the Company’s leases (excluding the Company’s sublease income of $0.7 million and $1.0 million for the three and six months ended June 30, 2021, respectively) is as follows (in thousands, except lease term and discount rate):


	For Three Months Ended		For Six Months Ended
	June 30,		June 30,
	2021		2021
Lease Cost:
Operating lease cost	$	2,158	$	4,312
Variable lease cost		545		1,153
Total lease cost	$	2,703	$	5,465


	For Six Months Ended
	June 30,
	2021
Other information:
Operating cash flows used for operating leases	$	4,378
Weighted average remaining lease term		3.9 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 June 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 six months ended June 30, 2021 and 2020.

Debt

6 Months Ended

Jun. 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

6 Months Ended

Jun. 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 June 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 six months ended June 30, 2021, the Company recognized $4.6 million and $9.3 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, 2021 is $42.7 million. The Company will recognize the $9.5 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 is a maximum of six months as of June 30, 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 as options are exercised by Gilead or at the conclusion of the Option Exercise Period.

Net Loss per Share

6 Months Ended

Jun. 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 June 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:


	Six Months Ended June 30,
	2021	2020
Restricted stock awards	9,387	126,646
Restricted stock units	267,481	—
Warrant	—	7,614
Stock options	4,323,010	3,491,671
	4,599,878	3,625,931

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2021

Summary of Significant Accounting Policies

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 June 30,
	2021		2020
Cash and cash equivalents	$	206,919	$	115,128
Restricted cash		2,498		2,498
	$	209,417	$	117,626

Unaudited Interim Financial Information

Use of Estimates

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2021

Summary of Significant Accounting Policies

Schedule of reconciles of cash, cash equivalents and restricted cash


	As of June 30,
	2021		2020
Cash and cash equivalents	$	206,919	$	115,128
Restricted cash		2,498		2,498
	$	209,417	$	117,626

Fair Value of Financial Assets and Liabilities (Tables)

6 Months Ended

Jun. 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 June 30, 2021 and December 31, 2020 (in thousands):


	Fair Value Measurements at June 30, 2021
	Total		Level 1		Level 2		Level 3
Assets:
Money market funds, included in cash and cash equivalents	$	199,238	$	199,238	$	—	$	—
Marketable securities:
U.S. Treasury obligations		75,298		75,298		—		—
Total assets	$	274,536	$	274,536	$	—	$	—


	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)

6 Months Ended

Jun. 30, 2021

Marketable Securities

Summary of investments

The following table summarizes the Company’s investments as of June 30, 2021 (in thousands):


			Gross
	Amortized		Unrealized				Estimated
	Cost		Gains		Losses		Fair Value
Marketable securities available-for-sale:
U.S. Treasury obligations	$	75,289	$	9	$	—	$	75,298
Total available-for-sale securities	$	75,289	$	9	$	—	$	75,298

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)

6 Months Ended

Jun. 30, 2021

Accrued Expenses

Summary of accrued expenses

As of June 30, 2021 and December 31, 2020, accrued expenses consist of the following (in thousands):


	As of
	June 30,		December 31,
	2021		2020
Accrued external research and development expense	$	9,059	$	5,387
Accrued payroll and related expenses		4,231		6,663
Accrued professional and consulting expense		1,154		1,141
Accrued other		552		476
Accrued payable for property and equipment		458		1,291
	$	15,454	$	14,958

Equity-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Equity-Based Compensation

Summary of allocation of equity-based compensation


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
Research and development expense	$	2,847	$	887	$	4,958	$	1,702
General and administrative expense		3,379		1,508		5,941		2,907
	$	6,226	$	2,395	$	10,899	$	4,609

Summary of unrecognized equity-based compensation expense



	As of June 30, 2021
		Unrecognized Expense (in thousands)	Weighted Average Remaining Period of Recognition (years)
Restricted Stock Awards	$	28	0.3
Restricted Stock Units		13,783	3.6
Stock Options		57,333	2.7
	$	71,144

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	1,093,355	$	55.85
Exercised	(307,317)	$	10.91
Cancelled	(142,959)	$	28.47
Outstanding as of June 30, 2021	4,323,010	$	25.14	8.10	$	46,787
Options exercisable as of June 30, 2021	1,148,376	$	16.87	7.47	$	15,525

Schedule of fair value assumptions


	Six Months Ended
	June 30,
	2021		2020
Risk-free interest rate	0.74	%	1.24	%
Expected dividend yield	0.0	%	0.0	%
Expected term (years to liquidity)	6.21		6.19
Expected volatility	87.89	%	81.86	%

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	(48,582)	$	5.77
Restricted stock awards as of June 30, 2021	9,387	$	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	281,786	$	57.28
Forfeited	(14,305)	$	59.44
Restricted stock units as of June 30, 2021	267,481	$	57.17

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2021

Commitments and Contingencies

Summary of lease costs


	For Three Months Ended		For Six Months Ended
	June 30,		June 30,
	2021		2021
Lease Cost:
Operating lease cost	$	2,158	$	4,312
Variable lease cost		545		1,153
Total lease cost	$	2,703	$	5,465


	For Six Months Ended
	June 30,
	2021
Other information:
Operating cash flows used for operating leases	$	4,378
Weighted average remaining lease term		3.9 years
Weighted average incremental borrowing rate		7.5	%

Net Loss per Share (Tables)

6 Months Ended

Jun. 30, 2021

Net Loss per Share

Summary of anti-dilutive securities


	Six Months Ended June 30,
	2021	2020
Restricted stock awards	9,387	126,646
Restricted stock units	267,481	—
Warrant	—	7,614
Stock options	4,323,010	3,491,671
	4,599,878	3,625,931

Nature of the Business (Details)	6 Months Ended
Nature of the Business (Details)	Jun. 30, 2021 item
Nature of the Business
Number of collaborations	2

Summary of Significant Accounting Policies - Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Cash and cash equivalents and restricted cash
Cash and cash equivalents	$ 206,919	$ 160,358	$ 115,128
Restricted cash	2,498		2,498
Total	$ 209,417	$ 162,856	$ 117,626	$ 38,806

Fair Value of Financial Assets and Liabilities - (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Marketable securities:
U.S. Treasury obligations	$ 75,298	$ 180,673
Total assets	274,536	310,512
Money market funds
Assets:
Cash and cash equivalents	199,238	119,841
U.S. Treasury obligations
Assets:
Cash and cash equivalents		9,998
Level 1
Marketable securities:
U.S. Treasury obligations	75,298	180,673
Total assets	274,536	310,512
Level 1 \| Money market funds
Assets:
Cash and cash equivalents	$ 199,238	119,841
Level 1 \| U.S. Treasury obligations
Assets:
Cash and cash equivalents		$ 9,998

Marketable Securities - Summary of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Marketable securities available-for-sale
Amortization Cost	$ 75,289	$ 180,675
Gross Unrealized Gains	9	7
Gross Unrealized Losses		(9)
Estimated Fair Value	75,298	180,673
U.S. Treasury obligations
Marketable securities available-for-sale
Amortization Cost	75,289	180,675
Gross Unrealized Gains	9	7
Gross Unrealized Losses		(9)
Estimated Fair Value	$ 75,298	$ 180,673

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Expenses
Accrued external research and development expense	$ 9,059	$ 5,387
Accrued payroll and related expenses	4,231	6,663
Accrued professional and consulting expense	1,154	1,141
Accrued other	552	476
Accrued payable for property and equipment	458	1,291
Accrued expenses	$ 15,454	$ 14,958

Equity-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Equity-based compensation
Equity-based compensation expense	$ 6,226	$ 2,395	$ 10,899	$ 4,609
Research and development expense
Equity-based compensation
Equity-based compensation expense	2,847	887	4,958	1,702
General and administrative expense
Equity-based compensation
Equity-based compensation expense	$ 3,379	$ 1,508	$ 5,941	$ 2,907

Equity-Based Compensation - Unrecognized Expense (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
Equity-based compensation
Unrecognized Expense	$ 71,144
Restricted stock awards
Equity-based compensation
Unrecognized Expense	$ 28
Weighted Average Remaining Period of Recognition	3 months 18 days
Restricted stock units
Equity-based compensation
Unrecognized Expense	$ 13,783
Weighted Average Remaining Period of Recognition	3 years 7 months 6 days
Stock options
Equity-based compensation
Unrecognized Expense	$ 57,333
Weighted Average Remaining Period of Recognition	2 years 8 months 12 days

Equity-Based Compensation - Restricted stock (Details)	6 Months Ended
Equity-Based Compensation - Restricted stock (Details)	Jun. 30, 2021 $ / shares shares
Restricted stock awards
Number of Shares/Units
Outstanding, beginning (in shares) \| shares	57,969
Vested (in shares) \| shares	(48,582)
Outstanding, end (in shares) \| shares	9,387
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	3 months 18 days
Restricted stock units
Number of Shares/Units
Granted (in shares) \| shares	281,786
Forfeited (in shares) \| shares	(14,305)
Outstanding, end (in shares) \| shares	267,481
Weighted Average Fair Value
Granted (in dollars per share) \| $ / shares	$ 57.28
Forfeited (in dollars per share) \| $ / shares	59.44
Outstanding, end (in dollars per share) \| $ / shares	$ 57.17
Weighted Average Remaining Period of Recognition	3 years 7 months 6 days

Equity-Based Compensation - Stock Options (Details) - Stock options $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Number of Units
Outstanding, beginning (in shares) \| shares	3,679,931
Granted (in shares) \| shares	1,093,355
Exercised (in shares) \| shares	(307,317)
Cancelled (in shares) \| shares	(142,959)
Outstanding, end (in shares) \| shares	4,323,010	3,679,931
Options exercisable, end (in shares) \| shares	1,148,376
Weighted Average Exercise Price
Outstanding, beginning (in dollars per share)	$ 14.96
Granted (in dollars per share)	55.85
Exercised (in dollars per share)	10.91
Cancelled (in dollars per share)	28.47
Outstanding, end (in dollars per share)	25.14	$ 14.96
Options exercisable, end (in dollars per share)	$ 16.87
Stock options
Weighted average remaining contractual term	8 years 1 month 6 days	8 years 3 days
Weighted average remaining contractual term, exercisable	7 years 5 months 19 days
Aggregate intrinsic value, beginning \| $	$ 123,600
Aggregate intrinsic value, end \| $	46,787	$ 123,600
Aggregate intrinsic value, exercisable \| $	$ 15,525
Weighted average grant date fair value (in dollars per share)	$ 40.93

Equity-Based Compensation - Assumptions (Details) - Stock options	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Assumptions used in determining the fair value of options
Risk-free interest rate	0.74%	1.24%
Expected dividend yield	0.00%	0.00%
Expected term (years to liquidity)	6 years 2 months 15 days	6 years 2 months 8 days
Expected volatility	87.89%	81.86%
Weighted Average Remaining Period of Recognition	2 years 8 months 12 days

Commitments and Contingencies (Details) $ in Thousands			1 Months Ended		3 Months Ended	6 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Oct. 05, 2020 USD ($)	Dec. 20, 2019 USD ($)	Nov. 30, 2019 USD ($)	Feb. 28, 2018 USD ($) ft²	Jun. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Jan. 31, 2018 USD ($)	Mar. 31, 2015
Leased assets
Sublease income					$ 700	$ 1,000
Lease Cost:
Operating lease cost					2,158	4,312
Variable lease cost					545	1,153
Total lease cost					$ 2,703	5,465
Operating cash flows used for operating leases						$ 4,378
Weighted average remaining lease term					3 years 10 months 24 days	3 years 10 months 24 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
Allowance received						$ 14,000
Letter of credit			$ 2,300

Debt (Details) - Loan and Security Agreement $ in Millions	Oct. 16, 2020 USD ($)
Debt
Line of credit maximum	$ 50.0
Proceeds from credit facility	25.0
Remaining borrowing capacity	$ 25.0
Interest only period	2 years
Variable rate (as a percent)	7.85%
Final payment fee (as a percent)	4.00%
Minimum
Debt
Prepayment penalty (as a percent)	2.00%
Maximum
Debt
Prepayment penalty (as a percent)	3.00%
Wall Street Journal prime rate
Debt
Variable rate (as a percent)	4.60%

Agreements - Gilead (Details) $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
Agreements - Gilead (Details) $ in Thousands	Dec. 19, 2018 item	Dec. 31, 2019 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)
Agreements
Revenue earned			$ 4,595	$ 3,900	$ 9,303	$ 8,930
Gilead
Agreements
Number of programs \| item	3
Option exercise period	90 days
Revenue proceeds		$ 25,000
Revenue earned			4,600
Transaction price			$ 42,700		$ 42,700

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Agreements - Gilead obligation period (Details) - Gilead $ in Millions	Jun. 30, 2021 USD ($)
Agreements
Revenue remaining performance obligation amount	$ 42.7
Research and development services
Agreements
Revenue remaining performance obligation amount	9.5
Material rights
Agreements
Revenue remaining performance obligation amount	$ 33.2

Net Loss per Share (Details) - shares	6 Months Ended
Net Loss per Share (Details) - shares	Jun. 30, 2021	Jun. 30, 2020
Anti-dilutive securities
Outstanding warrants	2,179,487
Anti-dilutive securities excluded from the calculation of net loss per share	4,599,878	3,625,931
Restricted stock awards
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	9,387	126,646
Restricted stock units
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of net loss per share	267,481
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	4,323,010	3,491,671