Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Summary of Assumptions Used for Valuation of Fair Value of Stock Options

The Black-Scholes option-pricing model was used to estimate the fair value of stock options granted during the years ended December 31, 2022 and 2021 with the following weighted average assumptions:

	Year Ended December 31,
	2022	2021
Risk-free interest rate	1.7% – 4.2%	0.4% – 1.3%
Expected term (in years)	5.8 – 6.1	5.3 – 6.1
Expected volatility	90%	90%
Expected dividend yield	0%	0%

Fair Value Measurement Inputs and Valuation Techniques

The following assumptions were used in the estimation of the fair value of the tranche liability as a forward contract as of each of the dates indicated:

	June 17, 2021	December 31, 2020
Risk-free interest rate	0.07%	0.12%
Expected time to Milestone Closing (in years)	0.8	1.3
Probability of achievement of Milestone Closing	100%	65%

The following assumptions were used in the estimation of the fair value of the warrant liability using the OPM backsolve method as of each of the dates indicated:

	June 22, 2021	December 31, 2020
Risk-free interest rate	0.25%	0.13%
Expected term (in years)	2.0	2.0
Expected volatility	90%	90%
Expected dividend yield	0%	0%

As of December 31, 2020, management, with the assistance of an independent third-party valuation firm, estimated the fair value of a share of common stock utilizing the following assumptions:

Risk-free interest rate	0.13%
Expected time to liquidity event (in years)	2.0
Expected volatility	90%
Expected dividend yield	0%

Summary of Stock Option Activity

The following table reflects summarized stock option activity:

	Stock Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2022	3,835,618	$	2.51
Granted	1,999,050	$	5.04
Exercised	(131,626)	$	0.93
Forfeited	(79,872)	$	6.35
Expired	(12,277)	$	16.00
Outstanding at December 31, 2022	5,610,893	$	3.36	8.1	$	14,980
Vested and exercisable at December 31, 2022	2,188,874	$	2.03	7.1	$	8,714

Summary of Share-Based Compensation Expense Related to Stock Options

The Company recorded stock-based compensation expense related to stock options in the following expense categories of its statements of operations and comprehensive loss for the periods shown (in thousands):

	Year Ended December 31,
	2022		2021
General and administrative	$	2,163	$	690
Research and development	898		232
Total stock-based compensation	$	3,061	$	922