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Related Party Transactions - Additional Information (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2020 USD ($) shares	Oct. 31, 2019 USD ($) Research	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019	Dec. 19, 2019 USD ($)
Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Charitable contribution		$ 69,600,000
Committed to provide equity financing		$ 30,000,000
Percentage of outstanding equity on fully diluted basis			6.10%		6.10%		7.40%
Maximum \| Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Number of Integrin research targets \| Research		3
Committed to provide equity financing		$ 30,000,000
IPO \| Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Committed to provide equity financing		10,000,000
Series C Redeemable Convertible Preferred Stock \| Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Committed to provide equity financing		$ 20,000,000						$ 20,000,000
Third Rock Ventures
Related Party Transaction [Line Items]
Consulting service expenses			$ 0		$ 0
Third Rock Ventures \| Non-employee Director \| Stock Options
Related Party Transaction [Line Items]
Option granted \| shares	26,573
Grant date fair value of stock option	$ 100,000
Vesting rights					The common shares subject to these options vest 1/12th on the last day of each calendar quarter over a three-year period and commenced vesting upon our IPO.
Vesting period					3 years
Third Rock Ventures \| General and Administrative Expenses
Related Party Transaction [Line Items]
Consulting service expenses				$ 6,000		$ 32,000
UCSF Foundation
Related Party Transaction [Line Items]
Charitable contribution			$ 0	$ 0	$ 700,000	$ 400,000