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”), which provide for the grant of stock-based awards to its directors, officers and 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.

In July 2023, the Board of Directors approved an amendment to the 2019 Inducement Plan to increase the number of shares of common stock authorized for issuance by 250,000 shares.

The weighted-average grant date fair value of options, estimated as of the grant date using the Black-Scholes option pricing model, was $1.29 and $7.94 per option for those options granted during the nine months ended September 30, 2023 and 2022, respectively.

The following table summarizes stock option activity under all equity plans (excluding RSUs) during the nine months ended September 30, 2023:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2022		3,979,099		$	10.99		5.27	$	1
Granted		46,413			1.74
Exercised		—			—
Forfeited or cancelled		(1,110,322	)		10.71
Outstanding as of September 30, 2023		2,915,190		$	10.95		5.87	$	1
Outstanding as of September 30, 2023 - vested and expected to vest		2,915,190		$	10.95		5.87	$	1
Exercisable at September 30, 2023		2,346,087		$	10.28		5.47	$	—

As of September 30, 2023, a total of 11,845,127 shares of common stock have been authorized and reserved for issuance under all of the Company's equity plans and 2,795,987 shares of common stock were available for future issuance under such plans. As of September 30, 2023, there was approximately $5.5 million of total unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted-average period of approximately 1.74 years.

The Company granted 4,272,199 RSUs to employees during the nine months ended September 30, 2023.

The following table summarizes RSU activity under all equity plans during the nine months ended September 30, 2023:


	Number of RSU Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2022		1,160,397		$	8.29
Granted		4,272,199			1.81
Vested and released		(328,645	)		7.30
Forfeited or cancelled		(341,306	)		7.19
Outstanding as of September 30, 2023		4,762,645		$	2.62

As of September 30, 2023, there was approximately $10.7 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted-average period of approximately 3.32 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. 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 or 2019 Inducement Plan.

In September 2022, the Company approved an award of 140,000 performance-based stock units as part of an executive inducement grant ("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. The Company recognized $0.1 million of expense associated with the Inducement PSUs during the nine months ended September 30, 2023.

The following table summarizes Inducement PSU activity under all equity plans during the nine months ended September 30, 2023:


	Number of Inducement PSU Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2022		140,000		$	1.08
Granted		—			—
Vested and released		(70,001	)		1.08
Forfeited or cancelled		—			—
Outstanding as of September 30, 2023		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 September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022

Research and development expenses	$	619	$	730	$	2,006	$	2,595
General and administrative expenses		1,289		1,376		3,929		4,031
Total	$	1,908	$	2,106	$	5,935	$	6,626