The Company currently grants equity-based awards under its 2020 Incentive Award Plan (“2020 Plan”) and its 2022 Employment Inducement Award Plan (“Inducement Award Plan”). The Company previously granted equity-based awards under its 2005 Equity Incentive Plan (“2005 Plan”) and 2016 Equity Incentive Plan (“2016 Plan” and together with the 2020 Plan, the Inducement Award Plan and the 2005 Plan, the “Plans”). The Company also maintains the 2020 Employee Stock Purchase Plan (the “ESPP”).

A summary of the restricted stock unit activity under the Plans for the six months ended June 30, 2024 was as follows:


	Shares			Weighted- Average Grant Date Fair Value
Restricted stock units outstanding as of December 31, 2023		105,048		$	3.20
Granted		984,929		$	5.49
Vested		(27,869	)	$	3.29
Forfeited		(194,636	)	$	4.28
Restricted stock units outstanding as of June 30, 2024		867,472		$	5.56

A summary of the stock option activity under the Plans for the six months ended June 30, 2024 was as follows:


	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023		5,709,980		$	5.68		8.0	$	6,334
Granted		2,605,002			4.89
Exercised		(1,002	)		3.96
Cancelled		(1,268,147	)		4.56
Outstanding at June 30, 2024		7,045,833		$	5.59		8.0	$	—

The fair value of each stock option granted to employees, directors and non-employees was estimated on the date of grant using the Black-Scholes option-pricing model, or a Monte Carlo simulation in the case of certain options granted to executive officers, with the following weighted-average assumptions for the three and six months ended June 30, 2024 and 2023:


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Risk-free interest rate		4.4	%		3.8	%		4.2	%		3.7	%
Expected dividend yield		—	%		—	%		—	%		—	%
Expected term (in years)		5.7			6.1			6.0			6.0
Expected volatility		111.5	%		82.0	%		80.5	%		82.9	%

The weighted-average fair value of options granted to employees, directors and non-employees during the three months ended June 30, 2024 and 2023 was $1.19 and $2.24, respectively. The weighted-average fair value of options granted to employees, directors and non-employees during the six months ended June 30, 2024 and 2023 was $2.80 and $2.07, respectively.

Stock-based compensation expense included in the Company’s consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Three Months Ended June 30,					Six Months Ended June 30,
	2024			2023		2024		2023
Research and development	$	(290	)	$	287	$	413	$	571
General and administrative		1,414			1,067		2,873		2,393
Total	$	1,124		$	1,354	$	3,286	$	2,964

For the period ended June 30, 2024, approximately $15,000 of the stock-based compensation expense was recorded as a liability. For the period ended June 30, 2023, the Company did not record any stock-based compensation expense as a liability.

Unrecognized share-based compensation related to stock-based options amounted to $7.5 million at June 30, 2024 and is expected to be recognized over a weighted average period of approximately 3.05 years. Unrecognized share-based compensation related to restricted stock units amounted to $2.6 million at June 30, 2024 and is expected to be recognized over a weighted average period of approximately 2.3 years.

In March 2024, the Company granted options to purchase 550,000 shares of common stock at an exercise price of $6.07 per share to its Chief Executive Officer (“2024 Performance Option”) and granted 385,000 RSUs to its Executive Chair (“2024 PSUs”), each with performance-based vesting conditions under the 2020 Plan. Vesting of the 2024 Performance Option and the 2024 PSUs are based on the achievement of various clinical and regulatory milestones during the specified periods.

For the performance-based stock awards, the Company measures stock compensation expense based on the fair value of the award on the grant date and then once the Company determines the performance criteria is probable of achievement, recognizes such amount over the vesting term of the award, which is approximately 3.8 years. The Company determined the fair value of the

2024 Performance Option using the Black-Scholes option-pricing model using the following inputs: risk-free interest rate of 4.26%, volatility of 76.82%, expected dividend yield 0%, and expected term of 6.0 years.

The Company measured the 2024 PSUs based on the fair value of the Company’s stock on the date of grant.

As of March 31, 2024, the Company has determined that 183,333 shares of common stock subject to the 2024 Performance Option and 128,333 shares of common stock underlying the 2024 PSUs are probable to vest and as of June 30, 2024 has recognized approximately $112,000 of expense, which is included in stock-based compensation expense. As of June 30, 2024, there is $1.4 million of unrecognized stock compensation expense to be recognized in connection with all of the performance-based awards that are deemed to be probable as of June 30, 2024.

As of June 30, 2024, there were 1,531,693 shares available for grant under the 2020 Plan and 635,917 shares available for grant under the Inducement Award Plan.

As of June 30, 2024, there are a total of 724,906 shares available for issuance, no awards outstanding under the 2020 ESPP and no shares have been issued under the 2020 ESPP.