Consolidated Statements Of Operations And Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Revenues	$ 1,418
Cost and expenses:
Cost of revenues	1,968
Research and development	28,640	26,444	24,961
Sales and marketing	14,751	7,256	5,857
General and administrative	19,073	16,265	17,136
Total costs and expenses	64,432	49,965	47,954
Loss from operations	(63,014)	(49,965)	(47,954)
Other income (expense):
Interest income (expense), net	(646)	114	983
Total other income (expense)	(646)	114	983
Loss from operations, before income taxes	(63,660)	(49,851)	(46,971)
Income tax benefit
Net loss	(63,660)	(49,851)	(46,971)
Other comprehensive gain (loss):
Unrealized gain (loss) on available-for-sale securities	1	(5)	5
Comprehensive loss	$ (63,659)	$ (49,856)	$ (46,966)
Net loss per share:
Basic and diluted net loss per share	$ (2.28)	$ (2.14)	$ (2.26)
Weighted average shares used to compute net loss per common share - basic and diluted	27,964	23,248	20,746