STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
STATEMENTS OF OPERATIONS
Alliance revenue			$ 1,448
Revenue, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Operating expenses:
Research and development	$ 16,375	$ 24,772	$ 34,853
General and administrative	9,976	11,915	12,481
Restructuring costs	1,322		181
Total operating expenses	27,673	36,687	47,515
Loss from operations	(27,673)	(36,687)	(46,067)
Other income (expense):
Interest income	9	165	1,150
Interest expense	(7)	(3)
Warrant revaluation gain (loss)	6,983	(3,742)	(598)
Future tranche right revaluation gain (loss)	118,803	(72,367)	(10,964)
Foreign currency exchange loss	(24)	(28)	(36)
Net income / (loss)	98,091	(112,662)	(56,515)
Deemed dividend on preferred stock related to December 2019 Private Placement (see Note 7)			(28,043)
Undistributed earnings to preferred stockholders	(1,150)
Net income (loss) applicable to common stockholders	96,941	(112,662)	(84,558)
Net income (loss) applicable to common stockholders (Note 16)
Net income (loss)	96,941	(112,662)	(84,558)
Diluted	$ (28,845)	$ (112,662)	$ (84,558)
Net income (loss) per share applicable to common stockholders (Note 16)
Basic	$ 1.97	$ (3.33)	$ (2.96)
Diluted	$ (0.58)	$ (3.33)	$ (2.96)
Weighted-average number of common shares used in computing net income (loss) per share applicable to common stockholders
Basic	49,203	33,821	28,545
Diluted	50,127	33,821	28,545