The following table summarizes the Company’s stock-based compensation expense by line item for the three and six months ended June 30, 2023 and 2022 (in thousands):


	Three months ended June 30,				Six months ended June 30,
	2023		2022		2023		2022
Research and development	$	209	$	8,190	$	4,344	$	15,126
Selling, general and administrative	6,498		12,583		12,199		26,327
Total	$	6,707	$	20,773	$	16,543	$	41,453

The fair value of the Warrants at the issuance date was measured using the Black-Scholes-Merton option pricing model. The key inputs used in the valuation were as follows:



Expected term (years)	10
Risk free interest rate	3.0		%
Expected volatility	91.3		%
Dividend yield	—		%
Exercise price	$	2.15
Stock price	$	3.63

The fair value of the warrants upon the expiration of the option period was measured using the Black-Scholes-Merton option pricing model. The key inputs used in the valuation were as follows:



Expected term (year)	0.9
Expected volatility	116.4		%
Expected dividend rate	—		%
Risk free rate	4.7		%
Estimated fair value per warrant	$	0.57
Exercise price	$	1.05
Stock price	$	1.20

The warrants are liability classified and subject to periodic remeasurement. The fair value of the warrants at the issuance date was measured using the Black-Scholes option pricing model. The key inputs used in the valuation were as follows:


Expected term (years)	5.48
Expected volatility	124.9	%
Expected dividend rate	—	%
Risk free rate	4.05	%
Estimated fair value per warrant	$0.41
Exercise price	$0.67
Stock price	$0.48


Expected term (years)	5.27
Expected volatility	124.9	%
Expected dividend rate	—	%
Risk free rate	4.07	%
Estimated fair value per warrant	$0.40
Exercise Price	$0.65
Stock Price	$0.48