Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 2,120	$ 2,760	$ 6,168	$ 6,831
General and administrative	3,266	2,240	5,855	4,534
Total operating expenses	5,386	5,000	12,023	11,365
Loss from operations	(5,386)	(5,000)	(12,023)	(11,365)
Other income:
Investment income	73	106	178	198
Other (expense) income, net	(2)	15	(1)	207
Total other income	71	121	177	405
Net loss	(5,315)	(4,879)	(11,846)	(10,960)
Foreign currency translation adjustment	(2)	(3)	(1)	(1)
Unrealized gain on available-for-sale investments		8		16
Comprehensive loss	(5,317)	(4,874)	(11,847)	(10,945)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(5,315)	(4,879)	(11,846)	(10,960)
Net loss attributable to common stockholders	$ (5,315)	$ (4,879)	$ (11,846)	$ (10,960)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.27)	$ (0.28)	$ (0.61)	$ (0.62)
Weighted-average common shares outstanding used in net loss per share attributable to common stockholders - basic and diluted (in shares)	19,585,394	17,674,729	19,421,131	17,674,729
Included in operating expenses, above, are the following amounts for non-cash stock-based compensation expense:
Allocated share-based compensation	$ 101	$ 922	$ 881	$ 1,743
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	4	312	259	579
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	$ 97	$ 610	$ 622	$ 1,164