Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Product sales, net	$ 125	$ 273	$ 600
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Costs and operating expenses:
Cost of product sales	$ 370	$ 1,188	$ 912
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 34,673	$ 27,997	$ 32,805
Selling, general and administrative	14,707	14,575	11,690
Total costs and operating expenses	49,750	43,760	45,407
Loss from operations	(49,625)	(43,487)	(44,807)
Other income (expense):
Interest income	43	326	1,723
Interest expense	(1,599)	(1,570)	(1,591)
Total other (expense) income, net	(1,556)	(1,244)	132
Net loss	$ (51,181)	$ (44,731)	$ (44,675)
Net loss per share, basic and diluted	$ (0.81)	$ (1.10)	$ (1.45)
Weighted-average shares used to compute net loss per share, basic and diluted	63,441,330	40,845,844	30,726,786