Consolidated Statements of Operations and Other Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Collaboration revenue	$ 704	$ 984	$ 2,679	$ 2,409
Operating expenses:
General and administrative	3,318	2,776	11,205	9,640
Research and development	7,517	5,302	25,542	20,523
Total operating expenses	10,835	8,078	36,747	30,163
Loss from operations	(10,131)	(7,094)	(34,068)	(27,754)
Other income:
Interest income	123	99	460	309
Other (expense) income	(23)	5	(74)	77
Total other income	100	104	386	386
Loss before income taxes	(10,031)	(6,990)	(33,682)	(27,368)
Income tax expense				(413)
Net loss	(10,031)	(6,990)	(33,682)	(27,782)
Unrealized gains from available-for-sale securities	83		82	11
Comprehensive loss	$ (9,948)	$ (6,990)	$ (33,600)	$ (27,771)
Net loss per common share – basic and diluted	$ (0.34)	$ (0.31)	$ (1.20)	$ (1.30)
Weighted average common shares outstanding – basic and diluted	29,650,909	22,450,071	28,151,361	21,334,195