Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating expenses:
General and administrative	$ 3,632	$ 3,060
Research and development	2,191	2,154
Total operating expenses	5,823	5,214
Loss from operations	(5,823)	(5,214)
Other income (expense):
Change in fair value of warrant liability	3	(12)
Other income, net	69	257
Interest income	52	153
Interest expense	(29)	(353)
Gain on foreign currency exchange	3
Total other income	98	45
Loss before income tax expense	(5,725)	(5,169)
Net loss attributable to common stockholders	(5,725)	(5,169)
Other comprehensive gain, net:
Unrealized gain on marketable securities		12
Other comprehensive gain, net		12
Comprehensive loss	$ (5,725)	$ (5,157)
Per share information:
Net loss per share of common stock, basic and diluted (in dollars per share)	$ (0.06)	$ (0.06)
Weighted average common shares outstanding, basic and diluted (in shares)	96,332,324	88,897,292