CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 9,510	$ 8,102
General and administrative	3,642	3,143
Restructuring costs		131
Total operating expenses	13,152	11,376
Loss from operations	(13,152)	(11,376)
Other income (expense):
Interest income	125	404
Warrant revaluation income	1,101
Future tranche right revaluation income	20,711
Foreign currency exchange gain (loss)	32	(2)
Net income (loss)	$ 8,817	$ (10,974)
Net income (loss) per share applicable to common stockholders (Note 12)
Basic	$ 0.27	$ (0.40)
Diluted	$ 0.22	$ (0.40)
Weighted-average number of common shares used in computing net income (loss) per share applicable to common stockholders
Basic	30,300	27,676
Diluted	33,010	27,676
Comprehensive income (loss):
Net income (loss)	$ 8,817	$ (10,974)
Unrealized gain on available-for-sale securities		2
Total other comprehensive income		2
Comprehensive income (loss):	$ 8,817	$ (10,972)