Organization and description of business - Additional Information (Details) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended		14 Months Ended
	Dec. 09, 2019 USD ($) $ / shares shares	Nov. 12, 2019 USD ($) $ / shares shares	Feb. 29, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2019 USD ($) shares
Organization And Description Of Business [Line Items]
Date of incorporation				Nov. 19, 2012
Reverse stock split description				The Company effected a one-for-5.056564 reverse stock split of its common stock on October 25, 2019. The reverse stock split combined each approximately five shares of the Company’s issued and outstanding common stock into one share of common stock and correspondingly adjusted the conversion price of its redeemable convertible preferred stock
Reverse stock split ratio				0.197762749566702
Proceeds from royalty purchase agreement | $				$ 20,000	$ 20,000	$ 60,000
Accumulated deficit | $				$ (161,350)	$ (104,823)	$ (161,350)
Common stock, shares issued (shares) | shares				24,811,567	300,597	24,811,567
Shares issued upon conversion | shares		19,061,502
Redeemable Convertible Preferred Stock
Organization And Description Of Business [Line Items]
Shares issued upon conversion | shares		19,061,502
IPO
Organization And Description Of Business [Line Items]
Common stock, shares issued (shares) | shares		5,000,000
Public offering price | $ / shares		$ 12.00
Net proceeds from stock offering | $		$ 53,000
Over-allotment option
Organization And Description Of Business [Line Items]
Common stock, shares issued (shares) | shares	445,690
Public offering price | $ / shares	$ 12.00
Net proceeds from stock offering | $	$ 5,000
Subsequent Event
Organization And Description Of Business [Line Items]
Proceeds from royalty purchase agreement | $			$ 20,000