Note 8 - Stock Based Awards - Activity Under Stock Option Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2023
Balances, number of shares (in shares)	4,570,432
Balances, weighted average exercise price (in dollars per share)	$ 2.5
Options granted, number of shares (in shares)	3,207,654
Options granted, weighted average exercise price (in dollars per share)	$ 1.69
Options expired, number of shares (in shares)	(43,838)
Options expired, weighted average exercise price (in dollars per share)	$ 6.18
Options forfeited, number of shares (in shares)	(2,385,156)
Options forfeited, weighted average exercise price (in dollars per share)	$ 1.83
Balances, number of shares (in shares)	5,349,092
Balances, weighted average exercise price (in dollars per share)	$ 2.29
Balances, weighted average remaining contractual life (Year)	6 years 7 months 6 days
Balances, aggregate intrinsic value	$ 0
Outstanding and expected to vest, number of shares (in shares)	5,028,804
Outstanding and expected to vest, weighted average exercise price (in dollars per share)	$ 2.32
Outstanding and expected to vest, weighted average remaining contractual life (Year)	6 years 4 months 24 days
Outstanding and expected to vest, aggregate intrinsic value	$ 0
Exercisable, number of shares (in shares)	3,300,921
Exercisable, weighted average exercise price (in dollars per share)	$ 2.54
Exercisable, weighted average remaining contractual life (Year)	5 years
Exercisable, aggregate intrinsic value	$ 0