Note 2 - Basis of Presentation, Principles of Consolidation and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block]

	December 31,
	2021		2020
Prepaid insurance	$	589	$	579
Vendor prepayments and deposits		486		1,281
Prepaid sponsored research		474		164
Non-trade receivables		23		1
Related party receivables		22		—
Total prepaid expenses and other current assets	$	1,594	$	2,025

Schedule of Property, Plant and Equipment Useful Life [Table Text Block]

	Years
Leasehold improvements	Shorter of estimated useful lives or the term of the lease
Computer equipment		2
Software		3
Machinery and equipment		2 to 5
Furniture and office equipment		2 to 7

Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]

Description	Liabilities Measured at Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)
Fair value of warrant liability:
December 31, 2021	$	1,412	$	—	$	—	$	1,412
December 31, 2020	$	8,192	$	—	$	—	$	8,192

	Warrant Liability Long-Term
December 31, 2019	$	5,818
Exercise of warrants		(4	)
Issuances of warrants		4,724
Change in fair value - net		(2,346	)
December 31, 2020	$	8,192
Exercise of warrants		(52	)
Change in fair value - net		(6,728	)
December 31, 2021	$	1,412