As of June 30, 2022, there were 2,133,880 shares available for future issuance under the 2020 Equity Incentive Plan and 500,000 shares available for future issuance under the 2022 Inducement Equity Incentive Plan, which was adopted on March 1, 2022. The 2020 Equity Incentive Plan provides for the grants of stock options and other equity-based awards to employees, non-employee directors and consultants of the Company. The 2022 Inducement Equity Incentive Plan provides for the grants of equity-based awards to individuals not previously employees or non-employee directors of the Company.

The table below summarizes the total stock-based compensation expense included in the Company’s statements of operations and comprehensive loss for the periods presented (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	1,587	$	1,264	$	3,155	$	2,331
General and administrative		2,505		1,949		4,882		3,626
Total stock-based compensation expense	$	4,092	$	3,213	$	8,037	$	5,957

The following table summarizes the stock option activity for the six months ended June 30, 2022:


	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2021		5,268,320		$	14.16
Granted		1,757,035			8.13
Exercised		(46,889	)		1.65
Forfeited and cancelled		(324,389	)		16.94
Outstanding at June 30, 2022		6,654,077		$	12.51		8.0	$	4,449
Exercisable at June 30, 2022		3,087,337		$	10.05		6.9	$	3,935

The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes-Merton option pricing model with the following assumptions:


	Six Months Ended June 30,
	2022	2021
Risk-free interest rate	1.47% - 3.34%	0.60% - 1.15%
Expected volatility	82.98% - 87.60%	85.31% - 88.43%
Expected term (in years)	5.50-6.08	5.50 - 6.08
Expected dividend yield	0%	0%

The Company recognized stock-based compensation expense related to the vesting of stock options of $3.8 million and $3.2 million during the three months ended June 30, 2022 and 2021, respectively, and $7.5 million and $6.0 million during the six months ended June 30, 2022 and 2021, respectively. The total unrecognized compensation expense related to outstanding unvested stock-option awards as of June 30, 2022, was $35.8 million, which is expected to be recognized over a weighted-average remaining service period of 2.8 years.

The following table summarizes the restricted stock unit activity for the six months ended June 30, 2022:


	Number of Shares			Weighted- Average Grant-Date Fair Value
Outstanding at December 31, 2021		—		$	—
Granted		249,018			8.84
Vested		—			—
Forfeited		(12,076	)		9.48
Outstanding at June 30, 2022		236,942		$	8.81

The Company recognized stock-based compensation expense related to the vesting of restricted stock units of $0.2 million and $0.3 million during the three and six months ended June 30, 2022, respectively. The Company did not grant restricted stock units in 2021. Total unrecognized compensation expense related to restricted stock units as of June 30, 2022, was $1.8 million, which is expected to be recognized over a weighted-average remaining service period of 2.5 years.

The company recognized stock-based compensation expense related to the Employee Stock Purchase Plan (ESPP) of $0.1 million and $0.2 million during the three and six months ended June 30, 2022, respectively. There was no ESPP expense for the three and six months ended June 30, 2021.

The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive:


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Options to purchase common stock		6,654,077		5,206,688		6,654,077		5,206,688
Non-vested restricted stock units		236,942		—		236,942		—
Total		6,891,019		5,206,688		6,891,019		5,206,688