Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ 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	$ 206	$ 2,354	$ 6,374	$ 9,185
General and administrative	1,385	2,268	7,240	6,802
Total operating expenses	1,591	4,622	13,614	15,987
Loss from operations	(1,591)	(4,622)	(13,614)	(15,987)
Other income:
Investment income	53	113	231	311
Other income (expense), net	2	(1)	1	206
Total other income	55	112	232	517
Net loss	(1,536)	(4,510)	(13,382)	(15,470)
Foreign currency translation adjustment	(2)		(3)	(1)
Unrealized gain on available-for-sale investments		3		19
Comprehensive loss	(1,538)	(4,507)	(13,385)	(15,452)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(1,536)	(4,510)	(13,382)	(15,470)
Net loss attributable to common stockholders	$ (1,536)	$ (4,510)	$ (13,382)	$ (15,470)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.08)	$ (0.25)	$ (0.69)	$ (0.87)
Weighted-average common shares outstanding used in net loss per share attributable to common stockholders - basic and diluted (in shares)	19,585,394	17,824,186	19,476,487	17,725,095
Included in operating expenses, above, are the following amounts for non-cash stock-based compensation expense:
Allocated share-based compensation	$ 96	$ 904	$ 977	$ 2,647
Research and Development Expense [Member]
Included in operating expenses, above, are the following amounts for non-cash stock-based compensation expense:
Allocated share-based compensation	(26)	298	233	877
General and Administrative Expense [Member]
Included in operating expenses, above, are the following amounts for non-cash stock-based compensation expense:
Allocated share-based compensation	$ 122	$ 606	$ 744	$ 1,770