Debt (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of debt valuation assumptions

The assumptions used in the Black-Scholes option-pricing model were determined as follows:

	December 31, 2020
Volatility	96.30	%
Risk-free interest rate	0.65	%
Weighted average expected life (in years)	5.42
Dividend yield	0	%

The assumptions used in the Black-Scholes option-pricing model remain unchanged and are determined as follows:

Volatility	98.01	%
Risk-free interest rate	1.58	%
Expected life (in years)	7
Dividend yield	0 %

Schedule of carrying amounts of debt

The net carrying amounts of the liability components consisted of the following (in thousands):

	December 31,
	2021		2020
Principal	$	39,194	$	50,001
Less: debt discount	(3,402)		(4,282)
Net carrying amount	$	35,792	$	45,719

Schedule of interest expense recognized

The following table sets forth total interest expense recognized related to the 2024 Notes (in thousands):

	December 31,
	2021		2020
Contractual interest expense	$	7,052	$	6,429
Accretion of debt discount	880		750
Total	$	7,932	$	7,179