Cyteir Therapeutics (CYT) 10-Q 9 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 04, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	Cyteir Therapeutics, Inc.
Entity Central Index Key	0001662244
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		35,369,726
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Security12b Title	Common Stock, par value $0.001 per share
Trading Symbol	CYT
Security Exchange Name	NASDAQ
Entity File Number	001-40499
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	45-5429901
Entity Address Address Line One	128 Spring St, Building A
Entity Address, Address Line Two	Suite 510
Entity Address City Or Town	Lexington
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02421
City Area Code	857
Local Phone Number	285-4140
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 198,637	$ 10,938
Prepaid expenses and other current assets	1,668	1,193
Total current assets	200,305	12,131
Property and equipment, net	1,492	1,287
Other assets	256	317
Total assets	202,053	13,735
Current liabilities:
Accounts payable	3,512	1,689
Accrued expenses and other current liabilities	3,932	1,448
Total current liabilities	7,444	3,137
Deferred rent, net of current portion	334	452
Other long term liabilities	420	766
Total liabilities	8,198	4,355
Commitments and Contingencies (Note 11)
Stockholders' equity (deficit):
Preferred stock, $0.001 par value: 40,000,000 and 77,017,995 shares authorized as of June 30, 2021 and December 31, 2020, respectively; no shares issued and outstanding as of June 30, 2021 and December 31, 2020
Common stock, $0.001 par value: 114,000,000 and 100,000,000 shares authorized as of June 30, 2021 and December 31, 2020, respectively; 34,474,323 and 2,719,721 shares issued as of June 30, 2021 and December 31, 2020, respectively; 34,104,882 and 2,044,284 shares outstanding as of June 30, 2021 and December 31, 2020, respectively	34	2
Additional paid-in capital	262,355	1,894
Accumulated deficit	(68,534)	(49,927)
Total stockholders' equity (deficit)	193,855	(48,031)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	202,053	13,735
Series A Redeemable Convertible Preferred Stock
Current liabilities:
Redeemable convertible preferred stock		5,696
Series B Redeemable Convertible Preferred Stock
Current liabilities:
Redeemable convertible preferred stock		51,715
Series C Redeemable Convertible Preferred Stock
Current liabilities:
Redeemable convertible preferred stock

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	40,000,000	77,017,995
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	320,000,000	100,000,000
Common stock, shares issued	34,474,323	2,719,721
Common stock, shares outstanding	34,104,882	2,044,284
Series A Redeemable Convertible Preferred Stock
Convertible preferred stock, shares authorized	0	5,817,996
Convertible preferred stock, shares issued	0	5,817,996
Convertible preferred stock, shares outstanding	0	5,817,996
Series B Redeemable Convertible Preferred Stock
Convertible preferred stock, shares authorized	0	71,199,999
Convertible preferred stock, shares issued	0	55,200,000
Convertible preferred stock, shares outstanding	0	55,200,000
Series C Redeemable Convertible Preferred Stock
Convertible preferred stock, shares authorized	0	0
Convertible preferred stock, shares issued	0	0
Convertible preferred stock, shares outstanding	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development	$ 8,886	$ 3,633	$ 14,499	$ 8,634
General and administrative	2,422	875	4,146	1,884
Total operating expenses	11,308	4,508	18,645	10,518
Loss from operations	(11,308)	(4,508)	(18,645)	(10,518)
Other income (expense):
Other income (expense)	13	10	38	91
Total other income (expense)	13	10	38	91
Net loss	$ (11,295)	$ (4,498)	$ (18,607)	$ (10,427)
Net loss per share-basic and diluted	$ (4.83)	$ (3.18)	$ (8.29)	$ (7.38)
Weighted-average common stock outstanding-basic and diluted	2,337,947	1,414,009	2,245,243	1,413,554

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series C Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2019	$ (28,336)				$ 1	$ 767	$ (29,104)
Redeemable convertible preferred stock, Shares at Dec. 31, 2019		5,817,996	55,200,000
Redeemable convertible preferred stock at Dec. 31, 2019		$ 5,696	$ 51,715
Balance, Shares at Dec. 31, 2019					1,412,954
Exercise of common stock options, Shares					488
Stock-based compensation expense	89					89
Net loss	(5,929)						(5,929)
Balance at Mar. 31, 2020	(34,176)				$ 1	856	(35,033)
Redeemable convertible preferred stock, Shares at Mar. 31, 2020		5,817,996	55,200,000
Redeemable convertible preferred stock at Mar. 31, 2020		$ 5,696	$ 51,715
Balance, Shares at Mar. 31, 2020					1,413,442
Balance at Dec. 31, 2019	(28,336)				$ 1	767	(29,104)
Redeemable convertible preferred stock, Shares at Dec. 31, 2019		5,817,996	55,200,000
Redeemable convertible preferred stock at Dec. 31, 2019		$ 5,696	$ 51,715
Balance, Shares at Dec. 31, 2019					1,412,954
Net loss	(10,427)
Balance at Jun. 30, 2020	(38,566)				$ 1	964	(39,531)
Redeemable convertible preferred stock, Shares at Jun. 30, 2020		5,817,996	55,200,000
Redeemable convertible preferred stock at Jun. 30, 2020		$ 5,696	$ 51,715
Balance, Shares at Jun. 30, 2020					1,414,037
Balance at Mar. 31, 2020	(34,176)				$ 1	856	(35,033)
Redeemable convertible preferred stock, Shares at Mar. 31, 2020		5,817,996	55,200,000
Redeemable convertible preferred stock at Mar. 31, 2020		$ 5,696	$ 51,715
Balance, Shares at Mar. 31, 2020					1,413,442
Exercise of common stock options	1					1
Exercise of common stock options, Shares					595
Stock-based compensation expense	107					107
Net loss	(4,498)						(4,498)
Balance at Jun. 30, 2020	(38,566)				$ 1	964	(39,531)
Redeemable convertible preferred stock, Shares at Jun. 30, 2020		5,817,996	55,200,000
Redeemable convertible preferred stock at Jun. 30, 2020		$ 5,696	$ 51,715
Balance, Shares at Jun. 30, 2020					1,414,037
Balance at Dec. 31, 2020	(48,031)				$ 2	1,894	(49,927)
Redeemable convertible preferred stock, Shares at Dec. 31, 2020		5,817,996	55,200,000	0
Redeemable convertible preferred stock at Dec. 31, 2020		$ 5,696	$ 51,715
Balance, Shares at Dec. 31, 2020					2,044,284
Exercise of common stock options	154					154
Exercise of common stock options, Shares					49,235
Issuance of Series C redeemable convertible preferred stock, net of issuance costs of $345				$ 79,655
Issuance of Series C redeemable convertible preferred stock, net of issuance costs of $345, Shares				21,784,885
Vesting of early exercised options	196					196
Vesting of early exercised options, Shares					172,640
Stock-based compensation expense	488					488
Net loss	(7,312)						(7,312)
Balance at Mar. 31, 2021	(54,505)				$ 2	2,732	(57,239)
Redeemable convertible preferred stock, Shares at Mar. 31, 2021		5,817,996	55,200,000	21,784,885
Redeemable convertible preferred stock at Mar. 31, 2021		$ 5,696	$ 51,715	$ 79,655
Balance, Shares at Mar. 31, 2021					2,266,159
Balance at Dec. 31, 2020	$ (48,031)				$ 2	1,894	(49,927)
Redeemable convertible preferred stock, Shares at Dec. 31, 2020		5,817,996	55,200,000	0
Redeemable convertible preferred stock at Dec. 31, 2020		$ 5,696	$ 51,715
Balance, Shares at Dec. 31, 2020					2,044,284
Exercise of common stock options, Shares	65,228
Net loss	$ (18,607)
Balance at Jun. 30, 2021	193,855				$ 34	262,355	(68,534)
Redeemable convertible preferred stock, Shares at Jun. 30, 2021		0	0	0
Redeemable convertible preferred stock at Jun. 30, 2021
Balance, Shares at Jun. 30, 2021					34,104,882
Balance at Mar. 31, 2021	(54,505)				$ 2	2,732	(57,239)
Redeemable convertible preferred stock, Shares at Mar. 31, 2021		5,817,996	55,200,000	21,784,885
Redeemable convertible preferred stock at Mar. 31, 2021		$ 5,696	$ 51,715	$ 79,655
Balance, Shares at Mar. 31, 2021					2,266,159
Exercise of common stock options	40					40
Exercise of common stock options, Shares					15,987
Vesting of early exercised options	150					150
Vesting of early exercised options, Shares					131,861
Initial public offering, net of underwriting discounts, commissions and offering costs	121,627				$ 7	121,620
Initial public offering, net of underwriting discounts, commissions and offering costs, Shares					7,400,000
Conversion of convertible preferred stock into common stock upon initial public offering	137,066				$ 25	137,041
Redeemable convertible preferred stock, Conversion of convertible preferred stock into common stock upon initial public offering, Shares		(5,817,996)	(55,200,000)	(21,784,885)
Redeemable convertible preferred stock, Conversion of convertible preferred stock into common stock upon initial public offering		$ (5,696)	$ (51,715)	$ (79,655)
Conversion of convertible preferred stock into common stock upon initial public offering, Shares					24,290,875
Stock-based compensation expense	772					772
Net loss	(11,295)						(11,295)
Balance at Jun. 30, 2021	$ 193,855				$ 34	$ 262,355	$ (68,534)
Redeemable convertible preferred stock, Shares at Jun. 30, 2021		0	0	0
Redeemable convertible preferred stock at Jun. 30, 2021
Balance, Shares at Jun. 30, 2021					34,104,882

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Series C Redeemable Convertible Preferred Stock
Stock issuance costs	$ 345

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss			$ (18,607)	$ (10,427)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization expense	$ 100	$ 100	214	149
Stock-based compensation	772	107	1,260	196
Changes in operating assets and liabilities
Prepaid expenses and other current assets			(475)	144
Other assets			61
Accounts payable			1,696	367
Accrued expenses and other current liabilities			2,484	537
Deferred rent			(118)	241
Net cash used in operating activities			(13,485)	(8,793)
Cash flows from investing activities:
Purchases of property and equipment			(292)	(554)
Net cash used in investing activities			(292)	(554)
Cash flows from financing activities:
Proceeds from issuance of preferred stock, net of issuance costs			79,655
Proceeds from issuance of common stock upon initial public offering, net of underwriting discounts, commissions and offering costs of $10,398			121,627
Proceeds from exercise of stock options			194	1
Net cash provided by financing activities			201,476	1
Net (decrease) increase in cash, cash equivalents, and restricted cash			187,699	(9,346)
Cash, cash equivalents and restricted cash at beginning of period			11,194	29,156
Cash, cash equivalents and restricted cash at end of period	198,893	19,810	198,893	19,810
Supplemental disclosure of cash flows
Property and equipment purchases in accounts payable			127	14
Supplemental disclosure of noncash financing activities
Vesting of early exercised options			346
Initial public offering costs included in accounts payable and accrued expenses			1,175
Conversion of preferred stock to common stock upon initial public offering			137,066
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	198,637	19,554	198,637	19,554
Restricted cash (included in other assets)	$ 256	$ 256	$ 256	$ 256
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent
Total cash, cash equivalents, and restricted cash	$ 198,893	$ 19,810	$ 198,893	$ 19,810

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Statement Of Cash Flows [Abstract]
Underwriting discounts, commissions and offering costs	$ 10,398

Nature Of the Business

Nature Of the Business	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Nature Of the Business	1. Nature of the business Cyteir Therapeutics, Inc., (the “Company”) is a clinical-stage biotechnology company focused on developing and commercializing the next generation of precision oncology medicines that inhibit DNA damage repair and cause cancer cell death through a therapeutic strategy known as synthetic lethality. The Company’s lead program, CYT-0851, as well as its next generation drug candidate, CYT-1853, exploit a novel gain-of-function synthetically lethal relationship between overexpression of a family of DNA damaging genes called cytidine deaminases, and functional inhibition of homologous recombination, a DNA repair pathway critical for the survival of some cancers. The Company is using its expertise in DNA Damage Response biology and a disciplined approach to select targets for other novel, differentiated programs with the aim of building a patient-centric portfolio of effective cancer therapies. The Company was formed as a Delaware corporation on June 4, 2012, pursuant to the General Corporation Law of the State of Delaware. The Company has a principal office in Lexington, Massachusetts. Initial Public Offering On June 22, 2021, the Company completed an initial public offering ("IPO") in which the Company issued and sold 7,400,000 of its common stock, at a public offering price of $ 18.00 per share, resulting in gross proceeds of $ 133.2 million. The Company received $ 121.6 million in net proceeds after deducting underwriting discounts, commissions and offering costs. Upon closing of the IPO, all of the then-outstanding shares of convertible preferred stock automatically converted into 24,290,875 shares of common stock at the applicable conversion ratio then in effect. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. Reverse Stock Split On June 11, 2021, the Company effected a 1-for- 3.4088 reverse stock split of the Company’s common stock and adjusted the ratio at which the Company’s preferred stock is convertible into common stock, as well as the number of shares under the 2012 Stock Incentive Plan and the Company’s Amended and Restated Certificate of Incorporation, as well as the share amounts of restricted stock grants under the plan and the number of options and exercise prices of options under the plan as a result of the 1-for-3.4088 reverse stock split. All common shares, stock options, and per share information presented in the accompanying consolidated financial statements and notes thereto have been adjusted, where applicable, to reflect the reverse stock split on a retroactive basis for all periods presented. The per share par value and authorized number of shares of the Company’s common stock were not adjusted as a result of the split. Liquidity The Company has incurred net operating losses since inception and has funded its operations primarily with proceeds from the sale of redeemable convertible preferred stock and from United States government grants. As of June 30, 2021 , the Company had cash and cash equivalents of $ 198.6 million and an accumulated deficit of $ 68.5 million. The Company expects its operating losses and negative operating cash flows to continue into the foreseeable future as it continues to expand its research and development efforts. The Company expects that its cash and cash equivalents as of June 30, 2021 will be sufficient to fund its operating expenses and capital expenditure requirements for at least twelve months from the date these condensed consolidated financial statements are available to be issued. The Company will need additional funding to support its planned operating activities. There can be no assurances, however, that the current operating plan will be achieved or that additional funding will be available on terms acceptable to the Company, or at all. If the Company is unable to obtain sufficient funding, it could be required to delay its development efforts, limit activities and reduce research and development costs, which could adversely affect its business prospects. COVID-19 considerations The development of the Company’s product candidates could be disrupted and materially adversely affected by a pandemic, epidemic or outbreak of an infectious disease, such as the ongoing COVID-19 pandemic. The ongoing COVID-19 pandemic and the measures taken by the governments of countries affected by it could disrupt the supply chain and the manufacture or shipment of both drug substance and finished drug product for the Company’s product candidates for preclinical testing or clinical trials, cause diversion of healthcare resources away from the conduct of preclinical and clinical trial matters to focus on pandemic concerns, limit travel in a manner that interrupts key trial activities, such as trial site initiations and monitoring, delay regulatory filings with regulatory agencies in affected areas or adversely affect the Company’s ability to obtain regulatory approvals. These disruptions could also affect other facets of the Company’s business, including, but not limited to, the Company’s ability to recruit employees from outside of the United States, the ability of the Company’s CROs to conduct clinical trials and preclinical studies in countries outside of the United States, the Company’s ability to import materials from outside of the United States, including raw materials required to manufacture its drug candidates, the Company’s ability to export materials to its CROs and other third-parties located outside of the United States, the Company’s ability to identify suitable clinical sites or open those sites for enrollment due to competing business needs, the Company’s ability to enroll patients due to their fear of coming into medical facilities and their perceived risk of becoming infected at such facilities, and the Company’s ability to monitor the clinical data generated at its clinical sites, required for completion of clinical trials. The COVID-19 pandemic and mitigation measures also may have an adverse impact on global economic conditions, which could adversely impact the Company’s business, financial condition or results of operations. Additionally, the COVID-19 pandemic has resulted in significant financial market volatility and uncertainty. A continuation or worsening of the levels of market disruption and volatility as a result of the COVID-19 pandemic could have an adverse effect on the Company’s ability to access capital and on the market price of its common stock. The Company cannot presently predict the scope and severity of any potential business shutdowns or disruptions, but if the Company or any of the third parties on whom it relies or with whom it conducts business, were to experience shutdowns or other business disruptions, the Company’s ability to conduct business in the manner and on the timelines presently planned could be materially and adversely impacted.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of significant accounting policies Basis of Presentation and Consolidation The Company's significant accounting policies are disclosed in the audited consolidated financial statements for the years ended December 31, 2020 and 2019 ("audited financial statements"), included in the Company's final prospectus that forms part of the Company's Registration Statement on Form S-1, dated June 14, 2021 and filed with the SEC pursuant to Rule 424(b)(4) on June 21, 2021 (the "Final Prospectus") except as noted below. Interim Financial Information The accompanying condensed consolidated balance sheet at June 30, 2021, and the condensed consolidated statements of operations, statements of redeemable convertible preferred stock and changes in stockholders’ equity (deficit) for the three and six months ended June 30, 2021 and 2020 and statements of cash flows for the six months ended June 30, 2021 and 2020 are unaudited. The condensed consolidated interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the fair presentation of the Company’s financial position at June 30, 2021 and the results of its operations for the three and six months ended June 30, 2021and 2020 and its cash flows for the six months ended June 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2021 and 2020 are also unaudited. The results for the three and six months ended June 30, 2021 are not necessarily indicative of results to be expected for the full year or for any other subsequent interim period. Deferred Financing Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred financing costs until such financings are consummated. After consummation of the equity financing, these costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the respective equity instrument issued. Should an in-process equity financing be abandoned, the deferred financing costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations. Upon closing the IPO in June 2021, deferred financing costs were derecognized and recorded against the IPO proceeds as a debit to additional paid-in capital. No amounts were recorded as of June 30, 2021. As of December 31, 2020, the Company recorded deferred financing costs of $ 0.1 million, presented within other assets on the consolidated balance sheets. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13 , Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement , which modifies certain disclosure requirements on fair value measurements. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU 2018-13 is effective for fiscal years beginning after December 15, 2020 for nonpublic entities. The Company adopted this ASU on January 1, 2021 and the impact was no t material to its disclosures.

Fair Value Measurement

Fair Value Measurement	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement	3. Fair value measurement The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis (in thousands): June 30, 2021 Description Total Quoted prices in Significant Significant Assets: Cash equivalents $ 198,637 $ 198,637 $ — $ — Total assets $ 198,637 $ 198,637 $ $ December 31, 2020 Description Total Quoted prices in Significant Significant Assets: Cash equivalents $ 10,938 $ 10,938 $ — $ — Total assets $ 10,938 $ 10,938 $ — $ — During the six months ended June 30, 2021 and the year ended December 31, 2020 , there were no transfers between levels. The fair values of the Company’s cash equivalents, consisting of its standard checking accounts and money market funds, are based on quoted market prices in active markets without any valuation adjustment. The Company uses the carrying amounts of its restricted cash, prepaid expenses and other current assets, accounts payable and accrued expenses and other current liabilities to approximate their fair value due to the short-term nature of these amounts.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	6 Months Ended
	Jun. 30, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses and other current assets	4. Prepaid expenses and other current assets Prepaid expenses and other current assets consisted of the following (in thousands): June 30, December 31, Prepaid research and development expenses $ 1,345 $ 871 Prepaid other 323 322 Total $ 1,668 $ 1,193

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	5. Property and equipment, net Property and equipment, net consisted of the following (in thousands): June 30, December 31, Laboratory and computer equipment $ 1,115 $ 694 Leasehold improvements 1,266 1,268 Total property and equipment 2,381 1,962 Less: accumulated depreciation and amortization ( 889 ) ( 675 ) Property and equipment, net $ 1,492 $ 1,287 For both the three months ended June 30, 2021 and 2020 , depreciation and amortization expense related to property and equipment was $ 0.1 million. For the six months ended June 30, 2021 and 2020 , depreciation and amortization expense related to property and equipment was $ 0.2 and $ 0.1 million, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): June 30, December 31, Accrued research and development expenses $ 2,364 $ 193 Accrued bonuses 760 854 Accrued other 808 401 Total accrued expenses and other current liabilities $ 3,932 $ 1,448

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	6 Months Ended
	Jun. 30, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	7. Redeemable convertible preferred stock Cyteir issued Series A redeemable convertible preferred stock (“Series A Preferred Stock”), Series B redeemable convertible preferred stock ("Series B Preferred Stock), and Series C redeemable preferred stock ("Series C Preferred Stock). Upon issuance of each class of convertible preferred stock, the Company assessed the embedded conversion and liquidation features of the shares and determined that such features did not require the Company to separately account for these features. The Company also concluded that no beneficial conversion feature existed on the issuance date of each class of convertible preferred stock. On June 22, 2021, upon closing of the Company's IPO, all of the then-outstanding shares of preferred stock automatically converted into 24,290,875 shares of common stock. There were no outstanding shares of preferred stock at June 30, 2021. At December 31, 2020, preferred stock consisted of the following (in thousands, except share amounts): Preferred Preferred stock Carrying Liquidation Common stock Series A Preferred Stock 5,817,996 5,817,996 $ 5,696 $ 5,696 1,706,998 Series B Preferred Stock 71,199,999 55,200,000 51,715 51,715 16,195,656 Total 77,017,995 61,017,996 $ 57,411 $ 57,411 17,902,654 Significant terms of the Series A Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock (collectively, “Preferred Stock”) are as follows: Voting The holder of each share of Preferred Stock was entitled to one vote for each share of common stock into which it would convert and to vote with the common stock on all matters. As long as a minimum number of shares of Series A Preferred Stock, Series B Preferred Stock, and Series C Preferred Stock were outstanding, the holders of the Preferred Stock were entitled to elect four directors and the approval of certain actions requires a majority of the Preferred Stockholders. Conversion As of December 31, 2020, the shares of Preferred Stock were convertible into shares of common stock, at the conversion price in effect at the time of such conversion, which was initially one -for-one subject to adjustment for certain potential non-dilutive transactions. The conversion could be initiated by the holder at any time or was mandatory (a) at any time upon the written consent of the holders of a majority of the outstanding shares of the Preferred Stock or (b) immediately upon the closing of a qualified public offering of gross proceeds to the Company of at least $ 50,000,000 . In the event that any holder of shares of Series B Preferred Stock did not purchase the full amount of such holder’s preferred stock tranche obligation, then each share of Series B Preferred Stock held by such holder automatically converted into shares of common stock at a ratio of 1 /10th of the applicable conversion ratio. As all tranche obligations were completed as of July 2019, this conversion feature expired unexercised. Dividends The holders of the Preferred Stock were entitled to receive dividends at the rate of 8 % of the applicable original issue price per annum, as potentially adjusted for certain non-dilutive transactions. Dividends shall accrue whether or not declared, shall not be cumulative or compounded and shall be payable only when, as and if declared by the Board of Directors (the “Board”) and in preference and in priority to any dividends on common stock. There have been no dividends declared by the Board as of June 30, 2021. Liquidation preference In the event of any liquidation, dissolution, or winding up of the Company (“Liquidation Event”), the holders of Preferred Stock were entitled to receive prior and in preference to the holders of common stock, an amount equal to an amount per share equal to the greater of the original issue price, as potentially adjusted for certain non-dilutive transactions, plus all declared and unpaid dividends on the Preferred Stock or the price per share that would be received if the Preferred Stock were converted to common stock. If the assets and funds available to be distributed to all holders of Preferred Stock were insufficient to permit the payment, in full, of any of the liquidation preferences, then the entire assets and funds legally available for distribution to holders of the Preferred Stock would be distributed ratably among the holders of Preferred Stock, acting as a single class, at the time outstanding, ratably in proportion to the full amounts to which they would otherwise be respectively entitled. After the payment of the full liquidation preference of the Preferred Stock as set forth above, the remaining assets of the Company legally available for distribution in such Liquidation event shall be distributed ratably to the holders of shares of common stock. Redemption The Company has determined that all series of preferred stock are redeemable, based on the Certificate of Incorporation that states upon the occurrence of a deemed liquidation event, the holders of preferred stock are entitled to receive cash or other assets.

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Common Stock	8. Common stock The voting, dividend and liquidation rights of the holders of the Company’s common stock are subject to and qualified by the rights, powers and preferences of the holders of the preferred stock as set forth above. The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders (and written actions in lieu of meetings), and there are not any cumulative voting rights. The number of authorized shares of common stock may be increased or decreased by the affirmative vote of the holders of shares of capital stock of the Company; however, the issuance of common stock may be subject to the vote of the holders of one or more series of preferred stock that may be required by terms of the Certificate of Incorporation. As of June 30, 2021 and December 31, 2020, the Company has reserved the following shares of common stock for the potential conversion of outstanding preferred stock and exercise of stock options: June 30, December 31, Preferred Stock - 17,902,654 Options to purchase common stock 2,619,744 1,293,212 Remaining shares reserved for future issuance 5,859,231 148,035 Total 8,478,975 19,343,901

Stock-based Compensation

Stock-based Compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	9. Stock-based compensation 2012 Stock Incentive Plan The Company adopted the 2012 Stock Incentive Plan (the “2012 Plan”) in February 2016 pursuant to which the Company can issue incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock awards. Recipients of stock options or stock appreciate rights shall be eligible to purchase shares of the Company’s common stock at an exercise price equal to the estimated fair market value of such stock on the date of grant. The exercise price may be less than fair market value if the stock award is granted pursuant to an assumption or substitution for another stock award in the event of a merger or sale of the Company. The maximum term of options granted under the 2012 Plan is ten years , and stock options typically vest over a four-year period. The Board may assign vesting terms to the stock option grants as deemed appropriate. The Company also has the right of refusal to purchase any proposed disposition of shares issued under the 2012 Plan. The 2012 Plan allows for early exercise of all stock option grants if authorized by the Board at the time of grant. The shares of common stock issued from the early exercise of stock options are restricted and vest over time. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. At the discretion of the Board, unvested shares held by employees may accelerate vesting in the event of a change of control of the Company unless assumed or substituted by the acquirer or surviving entity. The 2012 Plan has been subsequently amended and provides for the issuance of up to 6,941,421 shares of common stock as of June 30, 2021 , of which 2,732,632 shares of common stock remain available for future grant under the 2012 Plan as of June 11, 2021. On June 11, 2021, the Company’s board of directors adopted, and in June 2021 the Company’s stockholders approved, the 2021 Equity Incentive Plan (the “2021 Plan”), which became effective immediately prior to the effectiveness of the registration statement for the initial public offering. The 2,732,632 shares of common stock available for future issuance under the 2012 Plan were made available for future issuance under the 2021 Plan upon the effectiveness of the 2021 Plan. 2021 Equity Incentive Plan In June 2021 the Company’s board of directors adopted, and in June 2021 the Company’s stockholders approved, the 2021 Plan, which became effective immediately prior to the effectiveness of the registration statement for the initial public offering. The 2021 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. Upon effectiveness of the 2021 Plan, the number of shares of common stock reserved for issuance under the 2021 Plan was 5,932,632 , which represents 3,200,000 shares along with 2,732,632 shares of common stock reserved for issuance under the 2012 Plan that remained available for grant under the 2012 Plan immediately prior to the effectiveness of the 2021 Plan. Shares of our common stock subject to outstanding awards granted under the 2012 Plan that expire unexercised or are terminated, surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right will become available for issuance under the 2021 Plan. The 2021 Plan includes an "evergreen" provision, which provides for an annual increase to be added on January 1st of each year beginning in 2022 and continuing through and including 2031 by the lesser of (i) 5 % of the number of shares of Stock outstanding as of such date and (ii) an amount determined by the board of directors. Upon adoption of the 2021 Plan, the Company ceased the grant of additional awards under the 2012 Plan. At June 30, 2021 , there were 5,932,632 shares of common stock issuable upon the exercise of outstanding options of which 5,859,231 shares of common stock remain available for future grant under the 2021 Plan. 2021 Employee Stock Purchase Plan In June 2021, the Company’s board of directors adopted, and the Company’s stockholders approved, the 2021 Employee Stock Purchase Plan (the “ESPP”), which became effective immediately prior to the effectiveness of the registration statement for the initial public offering. The ESPP is administered by the Company’s board of directors or by a committee appointed by the board of directors. The ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 300,000 shares of common stock. The number of shares of common stock reserved for issuance under the ESPP will automatically increase on January 1st of each year beginning in 2022 and continuing through and including 2031 by the least of (i) 1 % of the number of shares of Stock outstanding as of such date, (ii) 600,000 shares of Stock and (iii) the number of shares of Stock determined by the Board on or prior to such date for such year, up to a maximum of 6,300,000 shares in the aggregate. Early exercise of unvested stock options Shares purchased by employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be outstanding shares until those shares vest according to their respective vesting schedules. Cash received from employee exercises of unvested options is included in long-term liabilities on the condensed consolidated balance sheets. Amounts recorded are reclassified to common stock and additional paid-in capital as the shares vest. As of June 30, 2021 and December 31, 2020 , there were 369,411 and 675,070 unvested shares related to early exercises of stock options, respectively. Stock option valuation The assumptions that the Company used in the Black Scholes option-pricing model to determine the grant date fair value of stock options granted were as follows: June 30, December 31, Risk-free interest rate range 0.75 %- 1.09 % 0.4 %- 1.2 % Dividend yield 0.0 % 0.0 % Expected life of options (years) 5.5 - 6.1 5.5 - 6.5 Volatility rate range 95.6 %- 97.2 % 88.8 %- 94.6 % The following table summarizes the Company’s stock option activity during the six months ended June 30, 2021: Number of Weighted average Weighted average Aggregate intrinsic Outstanding as of December 31, 2020 1,293,021 $ 1.23 9.03 $ 567 Granted 1,447,699 $ 7.93 9.65 14,580 Exercised ( 65,228 ) $ 2.97 4.68 980 Forfeited or cancelled ( 55,748 ) $ 1.79 — 906 Outstanding as of June 30, 2021 2,619,744 $ 4.88 9.14 $ 34,373 Options vested and exercisable as of June 30, 2021 279,614 $ 2.87 7.94 $ 4,230 As of June 30, 2021 , there was $ 8.9 million of unrecognized stock-based compensation expense related to the share-based compensation arrangements under the 2012 Plan. The Company expects to recognize this amount over a weighted-average period of 1.4 years. The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the common stock as of the end of the reporting period. The weighted-average grant date fair value of the Company’s stock options granted during the three months ended June 30, 2021 and 2020 was $ 9.36 and $ 0.87 , respectively. The total fair value of options vested during the three months ended June 30, 2021 and 2020 was $ 0.7 million and $ 0.1 million, respectively. Stock-based compensation expense Stock-based compensation expense included in the Company’s condensed consolidated statements of operations is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Research and development $ 256 $ 31 $ 426 $ 64 General and administrative 516 76 834 132 Total stock-based compensation expense $ 772 $ 107 $ 1,260 $ 196

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	10. Net loss per share The Company’s potentially dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following shares from the computation of diluted net loss per share attributable to common stockholders as of June 30, 2021 and June 30, 2020 because including them would have had an anti-dilutive effect: Six Months Ended June 30, 2021 2020 Series A Preferred Stock - 1,706,998 Series B Preferred Stock - 16,195,656 Series C Preferred Stock - - Options to purchase common stock 2,619,744 2,011,720 Unvested shares from early exercises 369,441 -

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and contingencies Lease commitments On November 1, 2018, the Company entered into a lease agreement (the “Lease”) for office space for a term of 5 years and the Company has the option to extend the term for one additional 3-year period. The Company received a tenant improvement allowance of $ 70 per square foot, which is being amortized as a reduction in rent expense over the lease term. The Company was also required to provide an initial security deposit in the form of a letter of credit, which is secured by cash on deposit of $ 0.1 million, which is recorded as restricted cash on the condensed consolidated balance sheets. Rent expense, recognized on a straight-line basis over the term of the lease, for both the three months ended June 30, 2021 and June 30, 2020 was $ 0.2 million. On October 15, 2019, the Company entered into the First Amendment to the Lease (the “1st Amendment”) for additional office space at 128 Spring Street in Lexington, Massachusetts. The term of the 1st Amendment began on February 16, 2020 and runs co-terminus with the existing lease through October 31, 2023 . The Company also has the same option to extend the term of the 1st Amendment for one additional 3-year period. The Company received a tenant improvement allowance of $ 60 per square foot. which is being amortized as a reduction in rent expense over the lease term. The Company was required to increase its total security deposit to $ 0.3 million as of the commencement date of the 1st Amendment. The future minimum payments required under the lease as of June 30, 2021 are as follows (in thousands): Year Ending June 30, 2021 (6 months) $ 359 2022 735 2023 627 $ 1,721 Legal proceedings From time to time, in the ordinary course of business, the Company is subject to litigation and regulatory examinations as well as information gathering requests, inquiries and investigations. As of June 30, 2021 , there were no matters which would have a material impact on the Company’s financial results.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent events Lease Amendment On July 1, 2021, the Company entered into a Second Amendment (the “2nd Amendment”) to the Lease with 99 Hayden LLC, successor-in-interest to 128 Spring Street Lexington, which covers certain laboratory and office space at Ledgemont Technology Center at 99 Hayden Avenue, Lexington, Massachusetts (the “Premises”). The 2nd Amendment expands the space leased by the Company at the Premises by approximately 5,531 square feet to a total of 20,167 rentable square feet for an additional two years and two months, commencing on October 31, 2023 and expiring on December 31, 2025. Underwriters' Option On July 1, 2021, the underwriters of our IPO partially exercised their over-allotment option by purchasing an additional 885,644 shares of our common stock at a public offering price of $ 18.00 per share for gross proceeds of $ 15.9 million prior to deducting underwriting discounts, commissions, and other offering expenses, from the partial exercise of the over-allotment of the IPO by the underwriters. The remainder of the underwriters' over-allotment option expired unexercised.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The Company's significant accounting policies are disclosed in the audited consolidated financial statements for the years ended December 31, 2020 and 2019 ("audited financial statements"), included in the Company's final prospectus that forms part of the Company's Registration Statement on Form S-1, dated June 14, 2021 and filed with the SEC pursuant to Rule 424(b)(4) on June 21, 2021 (the "Final Prospectus") except as noted below.
Interim Financial Information	Interim Financial Information The accompanying condensed consolidated balance sheet at June 30, 2021, and the condensed consolidated statements of operations, statements of redeemable convertible preferred stock and changes in stockholders’ equity (deficit) for the three and six months ended June 30, 2021 and 2020 and statements of cash flows for the six months ended June 30, 2021 and 2020 are unaudited. The condensed consolidated interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the fair presentation of the Company’s financial position at June 30, 2021 and the results of its operations for the three and six months ended June 30, 2021and 2020 and its cash flows for the six months ended June 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2021 and 2020 are also unaudited. The results for the three and six months ended June 30, 2021 are not necessarily indicative of results to be expected for the full year or for any other subsequent interim period.
Deferred Financing Costs	Deferred Financing Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred financing costs until such financings are consummated. After consummation of the equity financing, these costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the respective equity instrument issued. Should an in-process equity financing be abandoned, the deferred financing costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations. Upon closing the IPO in June 2021, deferred financing costs were derecognized and recorded against the IPO proceeds as a debit to additional paid-in capital. No amounts were recorded as of June 30, 2021. As of December 31, 2020, the Company recorded deferred financing costs of $ 0.1 million, presented within other assets on the consolidated balance sheets.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13 , Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement , which modifies certain disclosure requirements on fair value measurements. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU 2018-13 is effective for fiscal years beginning after December 15, 2020 for nonpublic entities. The Company adopted this ASU on January 1, 2021 and the impact was no t material to its disclosures.

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value On Recurring Basis	The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis (in thousands): June 30, 2021 Description Total Quoted prices in Significant Significant Assets: Cash equivalents $ 198,637 $ 198,637 $ — $ — Total assets $ 198,637 $ 198,637 $ $ December 31, 2020 Description Total Quoted prices in Significant Significant Assets: Cash equivalents $ 10,938 $ 10,938 $ — $ — Total assets $ 10,938 $ 10,938 $ — $ —

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): June 30, December 31, Prepaid research and development expenses $ 1,345 $ 871 Prepaid other 323 322 Total $ 1,668 $ 1,193

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): June 30, December 31, Laboratory and computer equipment $ 1,115 $ 694 Leasehold improvements 1,266 1,268 Total property and equipment 2,381 1,962 Less: accumulated depreciation and amortization ( 889 ) ( 675 ) Property and equipment, net $ 1,492 $ 1,287

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): June 30, December 31, Accrued research and development expenses $ 2,364 $ 193 Accrued bonuses 760 854 Accrued other 808 401 Total accrued expenses and other current liabilities $ 3,932 $ 1,448

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Temporary Equity Disclosure [Abstract]
Schedule of Redeemable Convertible Preferred Stock	At December 31, 2020, preferred stock consisted of the following (in thousands, except share amounts): Preferred Preferred stock Carrying Liquidation Common stock Series A Preferred Stock 5,817,996 5,817,996 $ 5,696 $ 5,696 1,706,998 Series B Preferred Stock 71,199,999 55,200,000 51,715 51,715 16,195,656 Total 77,017,995 61,017,996 $ 57,411 $ 57,411 17,902,654

Common Stock (Tables)

Common Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Schedule of Common Stock for Potential Conversion of Outstanding Preferred Stock and Exercise of Stock Options	As of June 30, 2021 and December 31, 2020, the Company has reserved the following shares of common stock for the potential conversion of outstanding preferred stock and exercise of stock options: June 30, December 31, Preferred Stock - 17,902,654 Options to purchase common stock 2,619,744 1,293,212 Remaining shares reserved for future issuance 5,859,231 148,035 Total 8,478,975 19,343,901

Stock-based Compensation (Table

Stock-based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Assumptions Used in Black Scholes Option-Pricing Model to Determine Grant Fair Value of Stock Option	The assumptions that the Company used in the Black Scholes option-pricing model to determine the grant date fair value of stock options granted were as follows: June 30, December 31, Risk-free interest rate range 0.75 %- 1.09 % 0.4 %- 1.2 % Dividend yield 0.0 % 0.0 % Expected life of options (years) 5.5 - 6.1 5.5 - 6.5 Volatility rate range 95.6 %- 97.2 % 88.8 %- 94.6 %
Schedule of Stock Option Activity	The following table summarizes the Company’s stock option activity during the six months ended June 30, 2021: Number of Weighted average Weighted average Aggregate intrinsic Outstanding as of December 31, 2020 1,293,021 $ 1.23 9.03 $ 567 Granted 1,447,699 $ 7.93 9.65 14,580 Exercised ( 65,228 ) $ 2.97 4.68 980 Forfeited or cancelled ( 55,748 ) $ 1.79 — 906 Outstanding as of June 30, 2021 2,619,744 $ 4.88 9.14 $ 34,373 Options vested and exercisable as of June 30, 2021 279,614 $ 2.87 7.94 $ 4,230
Schedule of Stock Based Compensation Expense	Stock-based compensation expense included in the Company’s condensed consolidated statements of operations is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Research and development $ 256 $ 31 $ 426 $ 64 General and administrative 516 76 834 132 Total stock-based compensation expense $ 772 $ 107 $ 1,260 $ 196

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Computation of Diluted Net Loss per Share Attributable to Common Stockholders	The Company excluded the following shares from the computation of diluted net loss per share attributable to common stockholders as of June 30, 2021 and June 30, 2020 because including them would have had an anti-dilutive effect: Six Months Ended June 30, 2021 2020 Series A Preferred Stock - 1,706,998 Series B Preferred Stock - 16,195,656 Series C Preferred Stock - - Options to purchase common stock 2,619,744 2,011,720 Unvested shares from early exercises 369,441 -

Commitments and contingencies (

Commitments and contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Payments Required Under Lease	The future minimum payments required under the lease as of June 30, 2021 are as follows (in thousands): Year Ending June 30, 2021 (6 months) $ 359 2022 735 2023 627 $ 1,721

Nature Of the Business - Additi

Nature Of the Business - Additional Information (Details) $ / shares in Units, $ in Thousands	Jun. 22, 2021USD ($)$ / sharesshares	Jun. 11, 2021	Jun. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2020USD ($)
Subsidiary Or Equity Method Investee [Line Items]
Stockholders' equity, reverse stock split			1-for-3.4088
Stockholders' equity note, stock split, conversion ratio		0.2934
Accumulated deficit			$ (68,534)	$ (49,927)
Cash and cash equivalents			$ 198,637	$ 10,938	$ 19,554
IPO [Member]
Subsidiary Or Equity Method Investee [Line Items]
Shares issued in IPO | shares	7,400,000
Public offering price | $ / shares	$ 18
Gross proceeds from issuance of common stock	$ 133,200
Net proceeds from issuance of common stock after deducting underwriting discounts, commissions and offering costs	$ 121,600
Convertible preferred stock converted to common stock | shares	24,290,875
Convertible preferred stock, shares outstanding | shares	0

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Deferred financing costs	$ 0	$ 100,000
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]	true
Accounting standards update [extensible list]	us-gaap:AccountingStandardsUpdate201813Member

Fair Value Measurement - Schedu

Fair Value Measurement - Schedule of Financial Assets and Liabilities Measured at Fair Value On Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Cash equivalents	$ 198,637	$ 10,938
Total assets	198,637	10,938
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	198,637	10,938
Total assets	$ 198,637	$ 10,938

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair value of assets, Level 1 to Level 2 transfers, amount	$ 0	$ 0
Fair value of assets, Level 2 to Level 1 transfers, amount	$ 0	$ 0

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development expenses	$ 1,345	$ 871
Prepaid other	323	322
Prepaid expenses and other current assets	$ 1,668	$ 1,193

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 2,381	$ 1,962
Less: accumulated depreciation and amortization	(889)	(675)
Property and equipment, net	1,492	1,287
Laboratory and Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,115	694
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,266	$ 1,268

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 100	$ 100	$ 214	$ 149

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued research and development expenses	$ 2,364	$ 193
Accrued bonuses	760	854
Accrued other	808	401
Total accrued expenses and other current liabilities	$ 3,932	$ 1,448

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($)	Jun. 22, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Series B Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock conversion ratio		0.10%
Preferred stock outstanding		0	55,200,000	55,200,000	55,200,000	55,200,000	55,200,000
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock converted into shares of common stock	24,290,875
Convertible preferred stock converted to common stock				1
Preferred stock outstanding		0		61,017,996
Preferred stock, voting rights		The holder of each share of Preferred Stock was entitled to one vote for each share of common stock into which it would convert and to vote with the common stock on all matters.
Preferred stock, conversion terms		As of December 31, 2020, the shares of Preferred Stock were convertible into shares of common stock, at the conversion price in effect at the time of such conversion, which was initially one-for-one subject to adjustment for certain potential non-dilutive transactions. The conversion could be initiated by the holder at any time or was mandatory (a) at any time upon the written consent of the holders of a majority of the outstanding shares of the Preferred Stock or (b) immediately upon the closing of a qualified public offering of gross proceeds to the Company of at least $50,000,000. In the event that any holder of shares of Series B Preferred Stock did not purchase the full amount of such holder’s preferred stock tranche obligation, then each share of Series B Preferred Stock held by such holder automatically converted into shares of common stock at a ratio of 1/10th of the applicable conversion ratio.
Threshold gross proceeds from qualified public offering		$ 50,000,000
Percentage of dividends for preferred stock holders		8.00%
Dividends declared		$ 0

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock - Schedule of Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Series A Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized	0		5,817,996
Preferred stock issued	0		5,817,996
Preferred stock outstanding	0	5,817,996	5,817,996	5,817,996	5,817,996	5,817,996
Carrying value		$ 5,696	$ 5,696	$ 5,696	$ 5,696	$ 5,696
Liquidation value			$ 5,696
Common stock issuable upon conversion			1,706,998
Series B Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized	0		71,199,999
Preferred stock issued	0		55,200,000
Preferred stock outstanding	0	55,200,000	55,200,000	55,200,000	55,200,000	55,200,000
Carrying value		$ 51,715	$ 51,715	$ 51,715	$ 51,715	$ 51,715
Liquidation value			$ 51,715
Common stock issuable upon conversion			16,195,656
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred stock authorized			77,017,995
Preferred stock issued			61,017,996
Preferred stock outstanding	0		61,017,996
Carrying value			$ 57,411
Liquidation value			$ 57,411
Common stock issuable upon conversion			17,902,654

Common stock - Additional Infor

Common stock - Additional Information (Details)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Common stock, voting rights	The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders (and written actions in lieu of meetings), and there are not any cumulative voting rights.

Common stock - Schedule of Comm

Common stock - Schedule of Common Stock for Potential Conversion of Outstanding Preferred Stock and Exercise of Stock Options (Details) - shares	Jun. 30, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock issuable upon conversion	8,478,975	19,343,901
Preferred Stock
Class Of Stock [Line Items]
Common stock issuable upon conversion		17,902,654
Options to Purchase Common Stock
Class Of Stock [Line Items]
Common stock issuable upon conversion	2,619,744	1,293,212
Remaining Shares Reserved for Future Issuance
Class Of Stock [Line Items]
Common stock issuable upon conversion	5,859,231	148,035

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 21, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of shares of common stock		8,478,975		8,478,975	19,343,901
Weighted-average grant date fair value of stock options granted		$ 9.36	$ 0.87
Weighted-average period				1 year 4 months 24 days
Total fair value of options vested		$ 0.7	$ 0.1
Unvested Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested shares related to early exercises of stock options		369,411		369,411	675,070
2012 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum term of options granted				10 years
Common stock available for future grant		2,732,632		2,732,632
Vesting period				4 years
Unrecognized stock based compensation expense		$ 8.9		$ 8.9
2012 Stock Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of shares of common stock		6,941,421		6,941,421
2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of shares of common stock		5,932,632		5,932,632
Common stock available for future grant		5,859,231		5,859,231
Percentage of number of shares of stock outstanding	5.00%
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of number of shares of stock outstanding	1.00%
Number of share increase				600,000
2021 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of shares of common stock	300,000
Number of shares of stock authorized		6,300,000		6,300,000
Current Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of shares of common stock		3,200,000		3,200,000
2012 Plan Shares Made Available Under 2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of shares of common stock		2,732,632		2,732,632
Common stock available for future grant		2,732,632		2,732,632

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions Used in Black Scholes Option-Pricing Model to Determine Grant Fair Value of Stock Option (Details) - Stock Option	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate range, minimum	0.75%	0.40%
Risk-free interest rate range, maximum	1.09%	1.20%
Dividend yield	0.00%	0.00%
Volatility rate range, minimum	95.60%	88.80%
Volatility rate range, maximum	97.20%	94.60%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life of options (years)	6 years 1 month 6 days	6 years 6 months
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life of options (years)	5 years 6 months	5 years 6 months

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, beginning balance	1,293,021
Number of shares, Granted	1,447,699
Number of shares, Exercised	(65,228)
Number of shares, Forfeited or cancelled	(55,748)
Number of shares, ending balance	2,619,744	1,293,021
Number of shares, Options vested and exercisable	279,614
Weighted average exercise price, beginning balance	$ 1.23
Weighted average exercise price, Granted	7.93
Weighted average exercise price, Exercised	2.97
Weighted average exercise price, Forfeited or cancelled	1.79
Weighted average exercise price, ending balance	4.88	$ 1.23
Weighted average exercise price, Options vested and exercisable	$ 2.87
Weighted average remaining contractual term (in years), balance	9 years 1 month 20 days	9 years 10 days
Weighted average remaining contractual term (in years), Granted	9 years 7 months 24 days
Weighted average remaining contractual term (in years), Exercised	4 years 8 months 4 days
Weighted average remaining contractual term (in years), Options vested and exercisable	7 years 11 months 8 days
Aggregate intrinsic value, beginning balance	$ 567
Aggregate intrinsic value, Granted	14,580
Aggregate intrinsic value, Exercised	980
Aggregate intrinsic value, Forfeited or cancelled	906
Aggregate intrinsic value, ending balance	34,373	$ 567
Aggregate intrinsic value, Options vested and exercisable	$ 4,230

Stock-based Compensation - Sc_2

Stock-based Compensation - Schedule of Stock 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
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 772	$ 107	$ 1,260	$ 196
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	256	31	426	64
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 516	$ 76	$ 834	$ 132

Net Loss per Share - Computatio

Net Loss per Share - Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Series A Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS		1,706,998
Series B Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS		16,195,656
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS	2,619,744	2,011,720
Unvested Shares from Early Exercises
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS	369,441

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Office Space $ in Millions	Feb. 16, 2020USD ($)Option$ / ft²	Nov. 01, 2018USD ($)Option$ / ft²	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021
Lessee, Lease, Description [Line Items]
Lease agreement term		5 years
Existence option to extend operating lease		true
Description of option to extend operating lease					On November 1, 2018, the Company entered into a lease agreement (the “Lease”) for office space for a term of 5 years and the Company has the option to extend the term for one additional 3-year period.
Term of option to extend operating lease		3 years
Number of option to extend lease term | Option		1
Tenant improvement allowance per square foot | $ / ft²		70
Rent expense			$ 0.2	$ 0.2
Massachusetts
Lessee, Lease, Description [Line Items]
Existence option to extend operating lease	true
Description of option to extend operating lease					The Company also has the same option to extend the term of the 1st Amendment for one additional 3-year period.
Term of option to extend operating lease	3 years
Number of option to extend lease term | Option	1
Tenant improvement allowance per square foot | $ / ft²	60
Security deposit	$ 0.3
Lease expiration date	Oct. 31, 2023
Restricted Cash
Lessee, Lease, Description [Line Items]
Security deposit		$ 0.1

Commitments and contingencies_2

Commitments and contingencies - Schedule of Future Minimum Payments Required Under Lease (Details) $ in Thousands	Jun. 30, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021 (6 months)	$ 359
2022	735
2023	627
Future minimum payments	$ 1,721

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Subsequent Event [Member] $ / shares in Units, $ in Millions	Jul. 01, 2021USD ($)$ / sharesshares
Subsequent Event [Line Items]
Over-allotment option by purchasing an additional shares of common stock | shares	885,644
Offering price per share | $ / shares	$ 18
Gross proceeds from issuance of common stock | $	$ 15.9