Condensed Consolidated Statements Of Operations And Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
General and administrative	$ 5,317	$ 5,146	$ 10,920	$ 9,547
Research and development	5,870	6,337	12,051	12,179
Amortization of intangible assets	167	166	333	333
Total operating expenses	11,354	11,649	23,304	22,059
Other income:
Interest income	21	290	99	622
Total other income	21	290	99	622
Net loss	(11,333)	(11,359)	(23,205)	(21,437)
Other comprehensive loss:
Unrealized gain on available-for-sale securities	(17)	20	(4)	23
Comprehensive loss	$ (11,350)	$ (11,339)	$ (23,209)	$ (21,414)
Net loss per share:
Basic and diluted net loss per share	$ (0.53)	$ (0.55)	$ (1.10)	$ (1.04)
Weighted average shares used to compute net loss per common share - basic and diluted	21,528	20,728	21,183	20,704