Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating expenses:
Research and development	$ 8,852	$ 8,106
General and administrative	2,839	2,094
Total operating expenses	11,691	10,200
Loss from operations	(11,691)	(10,200)
Other income, net	631	341
Loss before income taxes	(11,060)	(9,859)
Income tax expense	9
Net loss	$ (11,069)	$ (9,859)
Net loss per share, basic and diluted	$ (0.38)	$ (0.46)
Weighted-average common shares used in computing net loss per share, basic and diluted	29,014,750	21,523,072
Other comprehensive gain (loss):
Net loss	$ (11,069)	$ (9,859)
Unrealized gains on marketable securities	73
Comprehensive loss	$ (10,996)	$ (9,859)