The Company maintains two equity compensation plans, the 2017 Stock Incentive Plan, as amended (the “2017 Plan”) and the 2019 Inducement Equity Incentive Plan, as amended (the “2019 Inducement Plan”, and together with the 2017 Plan, the “Equity Plans”), which provide for the grant of stock-based awards to its directors, officers, consultants and other employees. The Equity Plans provide for the grant of non-qualified and incentive stock options, as well as restricted stock units (“RSUs”), restricted stock and other stock-based awards.

On May 29, 2024, the stockholders of the Company approved an amendment to the 2017 Plan to increase the number of shares of the Company’s common stock authorized for issuance under the 2017 Plan by 3,000,000 shares.

As of June 30, 2024, an aggregate of 18,345,127 shares of common stock have been authorized and reserved for issuance under the Equity Plans and an aggregate of 5,485,214 shares of common stock were available for future issuance under the Equity Plans.

The weighted-average grant date fair value of options, estimated as of the grant date using the Black-Scholes option pricing model, was $1.12 and $1.29 per option for those options granted during the six months ended June 30, 2024 and 2023, respectively.

The following table summarizes stock option activity under the Equity Plans (excluding RSUs) during the six months ended June 30, 2024:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2023		2,865,594		$	10.89		5.76	$	1
Granted		35,604			1.52
Exercised		—			—
Forfeited or cancelled		(43,156	)		13.31
Outstanding as of June 30, 2024		2,858,042		$	10.74		5.04	$	1
Outstanding as of June 30, 2024 - vested and expected to vest		2,858,042		$	10.74		5.04	$	1
Exercisable at June 30, 2024		2,540,372		$	10.44		4.85	$	—

As of June 30, 2024, there was approximately $2.8 million of total unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted-average period of approximately 1.16 years.

The following table summarizes RSU activity under the Equity Plans during the six months ended June 30, 2024:


	Number of RSU Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2023		5,368,807		$	2.45
Granted		3,410,996			1.56
Vested and released		(1,009,459	)		2.60
Forfeited or cancelled		(149,600	)		1.93
Outstanding as of June 30, 2024		7,620,744		$	2.04

As of June 30, 2024, there was approximately $12.8 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted-average period of approximately 2.97 years.

The fair value of the RSUs is determined on the date of grant based on the market price of the Company’s common stock on that date. Each RSU represents the right to receive one share of the Company’s common stock upon vesting. Other than RSUs granted as retention awards, the RSUs vest in four equal annual installments, subject to the individual’s continued service to the Company through the applicable vesting date, and are subject to the terms and conditions of the Company’s form of RSU agreement under the 2017 Plan and 2019 Inducement Plan, as applicable.

In September 2022, the Company approved an award of 140,000 performance-based stock units as part of an executive inducement grant (the “Inducement PSUs”). The Inducement PSUs were awarded based on certain performance criteria relating to pipeline execution, business development, and financial stewardship. As these performance criteria were deemed to be achieved by May 31, 2023, 70,001 of the Inducement PSUs vested in September 2023 and the remaining 69,999 of the Inducement PSUs will vest in September 2024 upon fulfilment of the service condition.

The following table summarizes Inducement PSU activity under the Equity Plans during the six months ended June 30, 2024:


	Number of Inducement PSU Shares		Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2023		69,999	$	1.08
Granted		—		—
Vested and released		—		—
Forfeited or cancelled		—		—
Outstanding as of June 30, 2024		69,999	$	1.08

The Company recorded share-based compensation expense related to incentive stock options, nonqualified stock options, stock grants, and stock-based awards in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023

Research and development expenses	$	729	$	589	$	1,419	$	1,387
General and administrative expenses		1,384		1,268		2,717		2,640
Total	$	2,113	$	1,857	$	4,136	$	4,027