Organization, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)		1 Months Ended		3 Months Ended			4 Months Ended	9 Months Ended		12 Months Ended
	Oct. 29, 2019 USD ($) shares	Dec. 31, 2020 USD ($) shares	May 31, 2019 shares	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 shares	Mar. 31, 2020 USD ($)	May 06, 2019 USD ($) shares	Sep. 30, 2021 USD ($) Segment shares	Sep. 30, 2020 shares	Dec. 31, 2020 USD ($)
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Fair value liabilities, level 1 to level 2 transfers, amount		$ 0		$ 0				$ 0		$ 0
Fair value liabilities, level 2 to level 1 transfers, amount		$ 0		$ 0				0		0
Fair value liability, transfers into level 3								0		0
Fair value liability, transfers out of level 3								0		$ 0
Conversion of Lender Warrants into equity						$ 318,000
Impairment losses								$ 0
Number of operating segment | Segment								1
Accounting Standards Update 2019-12
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, Accounting Standards Update, adopted [true false]				true				true
Change in accounting principle, Accounting Standards Update, Adoption date				Jan. 01, 2021				Jan. 01, 2021
Change in accounting principle, Accounting Standards Update, Immaterial effect [true false]				true				true
Unvested Shares
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Weighted-average unvested shares | shares				1,666,535	3,186,269			2,173,246	3,606,378
Furniture and Fixtures
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, useful life								3 years
Minimum | Computer Equipment and Related Software
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, useful life								2 years
Maximum | Computer Equipment and Related Software
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, useful life								3 years
Lender Warrants
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Expected cash dividend yield								0.00%
Takeda Warrant | Takeda License | Takeda
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Shares of common stock included in calculation of basic weighted-average common shares | shares				7,588,000				7,588,000
Fair Value, Recurring
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Financial assets fair value disclosure				$ 0				$ 0
Fair Value, Nonrecurring
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Non-financial assets fair value disclosure				0				0
Non-financial liabilities fair value disclosure				$ 0				0
Common Stock
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Common stock shares issued | shares							2,524,852
Net proceeds from issuance of common stock							$ 1,000
Common Stock | Takeda License
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Common stock shares issued | shares			1,084,000
Additional Paid-in Capital
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Conversion of Lender Warrants into equity						$ 318,000
Additional Paid-in Capital | Lender Warrants
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Conversion of Lender Warrants into equity								$ 300,000
IPO | Common Stock
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Common stock shares issued | shares	10,997,630
Proceeds from Initial Public Offering (IPO)	$ 191,500,000
Follow-on Public Offering | Common Stock
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Common stock shares issued | shares		250,000
Net proceeds from issuance of common stock		$ 88,600,000