Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 1,385	$ 237	$ 3,205	$ 12,169
Operating expenses:
Research and development	11,996	9,666	31,359	22,228
General and administrative	6,010	3,850	16,788	12,216
Other operating expense (income), net	4,015	(614)	6,319	1,377
Total operating expenses	22,021	12,902	54,466	35,821
Operating loss	(20,636)	(12,665)	(51,261)	(23,652)
Interest income (expense), net	(1,274)	(1,367)	(3,934)	(4,049)
Non-operating income (expense), net		7		(2,546)
Net loss	$ (21,910)	$ (14,025)	$ (55,195)	$ (30,247)
Net loss per common share - basic and diluted	$ (1.73)	$ (1.17)	$ (4.47)	$ (2.60)
Weighted-average common shares used to compute basic and diluted net loss per common share	12,685,000	11,969,791	12,349,870	11,612,760