Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended						9 Months Ended
	Mar. 12, 2020	Apr. 12, 2019	Apr. 01, 2019	Apr. 02, 2018	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Apr. 30, 2019
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Conversion of convertible preferred stock into common stock upon initial public offering, Shares				24,168,656
Common Stock, capacity terminated														$ 76,800
Net loss					$ 28,232	$ 35,340	$ 35,331	$ 29,627	$ 26,270	$ 23,852	$ 98,903	$ 79,749
Accumulated deficit					$ 298,577						298,577		$ 199,674
Net proceed from issuance of common stock												$ 134,524
Common Stock
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares issued and sold									6,388,889
Initial Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares issued and sold				10,350,000
Common stock at a public offering price				$ 16.00
Net proceeds from initial public offering after underwriting discounts and commissions and offering expenses				$ 150,800
Follow-On Offering | Common Stock
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares issued and sold		5,555,556
Shares issued price per share		$ 22.50
Net proceeds after deducting underwriting discounts and commissions and offering expenses		$ 116,900
Underwriters Option | Common Stock
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares issued and sold		833,333
Shares issued price per share		$ 22.50
Net proceeds after deducting underwriting discounts and commissions and offering expenses		$ 17,600
ATM
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds through future financings											$ 150,000
ATM | Maximum
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds through future financings	$ 150,000		$ 100,000
ATM | Common Stock
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares issued and sold											0
Pfizer Inc. Private Placement
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceed from issuance of common stock											$ 60,000