CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Expenses:
Research and development	$ 28,394	$ 12,376	$ 22,005
General and administrative	8,785	6,667	6,237
Loss from operations	(37,179)	(19,043)	(28,242)
Interest income	454	324	128
Interest expense		(159)	(464)
Other expense	(1)	(20)	(65)
Net loss	$ (36,726)	$ (18,898)	$ (28,643)
Per share information:
Net loss per share of common stock-basic and diluted (in dollars per share)	$ (0.90)	$ (0.80)	$ (1.47)
Basic and diluted weighted average shares outstanding (in shares)	40,895,406	23,540,748	19,498,143
Net loss	$ (36,726)	$ (18,898)	$ (28,643)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities	94	(96)
Total comprehensive loss	$ (36,632)	$ (18,994)	$ (28,643)