Nature of the Business - Additional Information (Details)				1 Months Ended	3 Months Ended								12 Months Ended
	May 01, 2019 USD ($)	Apr. 23, 2018 USD ($) $ / shares shares	Apr. 06, 2018	Jan. 31, 2016 shares	Dec. 31, 2019 USD ($) shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)
Class Of Stock [Line Items]
State of incorporation													DE
Net proceeds from issuance of common stock													$ 24,000
Common stock, issued | shares					27,893,337				27,772,600				27,893,337	27,772,600
Net loss					$ (15,954,000)	$ (16,878,000)	$ (17,758,000)	$ (4,199,000)	$ (4,735,000)	$ (17,222,000)	$ (15,852,000)	$ 31,212,000	$ (54,789,000)	$ (6,597,000)	$ (45,377,000)
Accumulated deficit					121,595,000				$ 66,806,000				$ 121,595,000	$ 66,806,000
Operating expenses and capital expenditure requirements													12 months
Cash, cash equivalents and marketable securities					$ 105,161,000								$ 105,161,000
Series A and A-1 Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock converted into common stock | shares		16,863,624
Initial Public Offering
Class Of Stock [Line Items]
Issuance of common stock (in shares) | shares		7,200,000
Shares issued, price per share | $ / shares		$ 15.00
Gross proceeds from issuance of common stock		$ 108,000,000
Net proceeds from issuance of common stock		$ 97,209,000
ATM Facility
Class Of Stock [Line Items]
Net proceeds from issuance of common stock													$ 24,000
Common stock, issued | shares					10,581								10,581
Novartis Institutes for Biomedical Research, Inc. | Novartis Collaboration | Private Placement
Class Of Stock [Line Items]
Issuance of common stock (in shares) | shares		766,666		766,666
Shares issued, price per share | $ / shares		$ 15.00
Net proceeds from issuance of common stock		$ 11,500,000
JonesTrading Institutional Services LLC | ATM Facility | Maximum
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock	$ 30,000,000
Percentage of gross proceeds of shares sold for compensation	3.00%
Common Stock
Class Of Stock [Line Items]
Reverse stock split, conversion ratio			0.4545
Issuance of common stock (in shares) | shares													10,581
Common Stock | Initial Public Offering
Class Of Stock [Line Items]
Issuance of common stock (in shares) | shares														7,200,000
Common Stock | Novartis Institutes for Biomedical Research, Inc. | Private Placement
Class Of Stock [Line Items]
Issuance of common stock (in shares) | shares														766,666