CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Expenses:
Research and development	$ 10,010	$ 7,232	$ 18,882	$ 11,159
General and administrative	2,502	2,338	6,169	4,526
Loss from operations	(12,512)	(9,570)	(25,051)	(15,685)
Interest income	90	65	186	181
Other (expense) income	(1)	1	(41)
Net loss	$ (12,423)	$ (9,504)	$ (24,906)	$ (15,504)
Per share information:
Net loss per share of common stock-basic and diluted (in dollars per share)	$ (0.24)	$ (0.24)	$ (0.47)	$ (0.38)
Basic and diluted weighted average shares outstanding (in shares)	52,522,225	40,395,650	52,493,874	40,384,429
Net loss	$ (12,423)	$ (9,504)	$ (24,906)	$ (15,504)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities		38		27
Total comprehensive loss	$ (12,423)	$ (9,466)	$ (24,906)	$ (15,477)