Condensed Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Product sales, net	$ 0	$ 35	$ 0	$ 125
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Costs and operating expenses:
Cost of product sales	$ 0	$ 140	$ 0	$ 370
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 9,232	$ 8,357	$ 18,638	$ 16,017
Selling, general and administrative	3,523	3,669	7,271	7,712
Total costs and operating expenses	12,755	12,166	25,909	24,099
Loss from operations	(12,755)	(12,131)	(25,909)	(23,974)
Other income (expense)
Interest income	89	11	100	26
Interest expense	(415)	(392)	(824)	(774)
Net loss	$ (13,081)	$ (12,512)	$ (26,633)	$ (24,722)
Net loss per share, basic	$ (0.19)	$ (0.19)	$ (0.39)	$ (0.42)
Net loss per share, diluted	$ (0.19)	$ (0.19)	$ (0.39)	$ (0.42)
Weighted-average shares used to compute net loss per share, basic	68,049,320	65,627,778	67,948,065	59,010,204
Weighted-average shares used to compute net loss per share, Diluted	68,049,320	65,627,778	67,948,065	59,010,204