Note 8 - Stock Based Awards - Activity Under Stock Option Plan (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($) $ / shares shares
Balances, number of shares (in shares) | shares	2,439,253
Balances, weighted average exercise price (in dollars per share) | $ / shares	$ 3.96
Options granted, number of shares (in shares) | shares	2,813,641
Options granted, weighted average exercise price (in dollars per share) | $ / shares	$ 1.63
Options cancelled, number of shares (in shares) | shares	(643,879)
Options cancelled, weighted average exercise price (in dollars per share) | $ / shares	$ 3.56
Options exercised, number of shares (in shares) | shares	0
Options exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Balances, number of shares (in shares) | shares	4,609,015
Balances, weighted average exercise price (in dollars per share) | $ / shares	$ 2.60
Balances, weighted average remaining contractual life (Year)	7 years 2 months 12 days
Balances, aggregate intrinsic value | $	$ 358
Outstanding and expected to vest, number of shares (in shares) | shares	4,238,168
Outstanding and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 2.63
Outstanding and expected to vest, weighted average remaining contractual life (Year)	7 years 1 month 6 days
Outstanding and expected to vest, aggregate intrinsic value | $	$ 358
Exercisable, number of shares (in shares) | shares	2,126,154
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 3.09
Exercisable, weighted average remaining contractual life (Year)	4 years 7 months 6 days
Exercisable, aggregate intrinsic value | $	$ 358