Stock-based Compensation Expense (Tables)

12 Months Ended

Dec. 31, 2023

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity during the year ended December 31, 2023:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2022		6,504,080		$	11.99		8.55	$	1,885,160
Granted		6,089,933			5.87
Exercised		(38,903	)		8.96
Cancelled		(2,582,893	)		11.33
Outstanding at December 31, 2023		9,972,217		$	8.44		8.49	$	15,114,074
Exercisable at December 31, 2023		3,225,146		$	12.59		7.17	$	407,817

Weighted Average Assumptions Used to Calculate Fair Value of Stock Option

The fair value of stock options granted during the years ended December 31, 2023 and 2022 has been calculated on the date of grant using the following weighted average assumptions:

	Year Ended December 31, 2023			Year Ended December 31, 2022
Risk-free interest rate		3.7	%		2.7	%
Expected dividend yield		0.0	%		0.0	%
Expected term (years)		6.1			6.1
Expected stock price volatility		98.6	%		90.0	%

Summary of Stock-Based Compensation Expense Recognized

The total compensation cost recognized in the statements of operations and comprehensive loss associated with all stock-based compensation awards granted by the Company is as follows (in thousands):

	Year Ended December 31,
	2023		2022
General and administrative	$	11,026	$	9,652
Research and development		3,776		3,698
Total stock-based compensation expense	$	14,802	$	13,350

Grants Outside of 2016 Stock Incentive Plan and 2019 Stock Incentive Plan

Summary of Restricted Stock Activity

The following table summarizes the Company’s restricted stock unit activity during the year ended December 31, 2023:

	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2022		76,718		$	9.73
Granted		37,045			12.59
Vested		(18,144	)		9.79
Cancelled		(20,602	)		11.03
Unvested at December 31, 2023		75,017		$	10.77