Fair Value (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Schedule of fair value hierarchy of liabilities measured at fair value on recurring basis

	2021
	Level 1		Level 2		Level 3		Total
Notes payable	$	736	$	—	$	—	$	736
Common stock warrant liability		—		—		474	$	474
Clene Nanomedicine contingent earn-out		—		—		18,100	$	18,100
Initial Stockholders contingent earn-out		—		—		2,317	$	2,317

	2020
	Level 1		Level 2		Level 3		Total
Notes payable	$	1,296	$	—	$	—	$	1,296
Clene Nanomedicine contingent earn-out		—		—		52,053	$	52,053
Initial Stockholders contingent earn-out		—		—		5,906	$	5,906

Schedule of unobservable inputs to the conversion feature, warrant liability, and contingent earn-out valuation models

	2021
Expected stock price volatility		105.00	%
Risk-free interest rate		0.70	%
Expected dividend yield		0.00	%
Expected term	2.39 years

	2021
Expected stock price volatility		105.00	%
Risk-free interest rate		1.20	%
Expected dividend yield		0.00	%
Expected term	3.89 – 4.39 years

	2021			2020
Expected stock price volatility		105.00	%		85.00	%
Risk-free interest rate		1.10	%		0.40	%
Expected dividend yield		0.00	%		0.00	%
Expected term	4.00 years			5.00 years

Schedule of changes in fair value of financial liabilities related to the notes payable, the derivative instrument, the preferred stock warrants, and the contingent earn-outs

(in thousands)	Notes Payable			Derivative Instrument			Preferred Stock Warrant Liability			Common Stock Warrant Liability			Clene Nanomedicine Contingent Earn-out			Initial Stockholders Contingent Earn-out
Balance - December 31, 2019	$	640		$	—		$	3,213		$	—		$	—		$	—
Issuance of convertible promissory notes		—			705			—			705			—			—
Initial fair value of instrument		—			—			—			—			64,712			7,371
Change in fair value		656			(29	)		14,615			(29	)		(12,659	)		(1,465	)
Extinguishment of preferred stock warrant liability in connection with the conversion of redeemable convertible preferred stock		—			—			(17,828	)		—			—			—
Extinguishment of derivative liability in connection with extinguishment of the 2020 Convertible Notes (Note 12)		—			(676	)		—			(676	)		—			—
Balance - December 31, 2020	$	1,296		$	—		$	—		$	—		$	52,053		$	5,906
Initial fair value of instrument		—			—			—			1,457			—			—
Change in fair value		(560	)		—			—			(983	)		(33,953	)		(3,589	)
Balance - December 31, 2021	$	736		$	—		$	—		$	474		$	18,100		$	2,317