Consolidated Statements of Comprehensive Loss-Unaudited - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenues:
Royalties and other revenue	$ 37	$ 27
Operating expenses:
Research and development, including stock-based compensation of $1,032, and $1,286, respectively	14,926	12,609
Selling, general and administrative, including stock-based compensation of $1,740, and $1,565, respectively	8,491	8,257
Total operating expenses	23,417	20,866
Loss from operations	(23,380)	(20,839)
Interest expense	(110)	(167)
Interest and other income, net	14	48
Net loss	$ (23,476)	$ (20,958)
Net income (loss) per common share, Basic	$ (0.16)	$ (0.15)
Shares used in computing net loss per common share, Basic	149,150	143,379
Unrealized gain on investments	$ (27)	$ 11
Comprehensive loss	(23,503)	(20,947)
Supplemental Income Statement Elements [Abstract]
Stock-based compensation expense associated with selling, general and administrative expense	1,740	1,565
Stock-based compensation expense associated with research and development expense	$ 1,032	$ 1,286