Consolidated Statements of Comprehensive Loss-Unaudited - USD ($) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Royalties and other revenue	$ 35,000	$ 234,000	$ 72,000	$ 261,000
Stock-based compensation expense associated with research and development expense	1,098,000	1,184,000	2,130,000	2,470,000
Operating expenses:
Research and development, including stock-based compensation of $1,098, $1,184, $2,130 and $2,470 respectively	13,356,000	10,257,000	28,282,000	22,866,000
Selling, general and administrative, including stock-based compensation of $1,734, $1,602, $3,474 and $3,167 respectively	10,686,000	7,936,000	19,177,000	16,193,000
Total operating expenses	(24,042,000)	18,193,000	47,459,000	39,059,000
Loss from operations	(24,007,000)	(17,959,000)	(47,387,000)	(38,798,000)
Interest expense	(703,000)	(169,000)	(813,000)	(336,000)
Interest and other income, net	123,000	61,000	137,000	109,000
Net loss	$ (24,587,000)	$ (18,067,000)	$ (48,063,000)	$ (39,025,000)
Net income (loss) per common share, Basic	$ (0.16)	$ (0.13)	$ (0.32)	$ (0.27)
Shares used in computing net loss per common share, Basic	149,616	144,451	149,384	143,917
Unrealized gain on investments	$ (113,000)	$ (10,000)	$ (140,000)	$ 1,000
Comprehensive loss	(24,700,000)	(18,077,000)	(48,203,000)	(39,024,000)
Supplemental Income Statement Elements [Abstract]
Stock-based compensation expense associated with selling, general and administrative expense	$ 1,734,000	$ 1,602,000	3,474,000	3,167,000
Business Exit Costs			$ 1,500	$ 0