Unaudited Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating expenses:
Research and development	$ 10,383	$ 9,407	$ 28,077	$ 25,609
General and administrative	4,674	5,968	15,353	17,945
Total operating expenses	15,057	15,375	43,430	43,554
Loss from operations	(15,057)	(15,375)	(43,430)	(43,554)
Interest income	495	637	1,782	1,711
Other income (expense)	0	(1)	151	(17)
Loss before income tax provision (benefit)	(14,562)	(14,739)	(41,497)	(41,860)
Income tax provision (benefit)	(125)	6	(116)	(833)
Net loss	(14,437)	(14,745)	(41,381)	(41,027)
Comprehensive loss	$ (14,437)	$ (14,745)	$ (41,381)	$ (41,027)
Net loss per common share:
Net loss per common shares - basic and diluted (in dollars per share)	$ (0.35)	$ (0.41)	$ (1.00)	$ (1.13)
Weighted average common shares outstanding:
Weighted average common shares outstanding - basic and dilutive (in shares)	41,552	36,202	41,486	36,181