Subsequent events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 31, 2020	Jul. 07, 2020	Jun. 30, 2020
Subsequent Event [Line Items]
Offering costs unpaid at period-end			$ 255
Subsequent Event
Subsequent Event [Line Items]
Offering costs unpaid at period-end		$ 4,900
Proceeds from offering, net of underwriting discounts and commissions		$ 71,400
Subsequent Event | Acqinox Pharmaceuticals [Member]
Subsequent Event [Line Items]
Consideration from sale of assets	$ 8,200
Underwritten Public Offering [Member] | Subsequent Event
Subsequent Event [Line Items]
Common stock shares issued		3,262,471
Common stock shares issued, price per share		$ 15.25
Prefunded Warrants [Member] | Subsequent Event
Subsequent Event [Line Items]
Warrant to purchase common stock		1,737,529
Warrant to purchase common stock, exercise price per share		$ 15.249999
Warrant to purchase common stock after issuance, exercise price per share		$ 0.000001