Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue	$ 1	$ 17	$ 22	$ 22
Operating expenses:
Research and development (including amounts with related parties)	13,709	13,131	26,943	25,729
Selling, general and administrative (including amounts with related parties)	6,519	4,182	11,892	9,924
Total operating expenses	20,228	17,313	38,835	35,653
Loss from operations	(20,227)	(17,296)	(38,813)	(35,631)
Other income (expense):
Investment income, net	75	533	253	903
Interest expense	(3)	0	(10)	(3)
Other income, net (including amounts with related parties)	67	83	99	130
Total other income	139	616	342	1,030
Loss before income taxes	(20,088)	(16,680)	(38,471)	(34,601)
Income tax (expense) benefit	(4)	(2)	(4)	34
Net loss	$ (20,092)	$ (16,682)	$ (38,475)	$ (34,567)
Net loss per share:
Basic and diluted	$ (0.20)	$ (0.17)	$ (0.39)	$ (0.38)
Weighted-average number of shares during the period:
Basic and diluted	98,769,687	98,594,355	98,621,161	89,975,707