On January 1, 2022, the number of shares of common stock available for issuance under the 2015 Equity Incentive Award Plan (the “2015 Plan”) and the 2015 Employee Stock Purchase Plan (“ESPP”) was increased by 3,484,942 shares and 696,988 shares, respectively, due to the annual evergreen provision to increase shares available under the 2015 Plan and the ESPP. As of March 31, 2022, there were an aggregate of 2,461,519 shares available for future grant under the 2017 Stock Incentive Plan (the 2017 Plan) and the 2015 Plan, and 1,341,301 shares available for future grant under the ESPP.

The following table summarizes equity‑based compensation expense within the Company’s consolidated statements of operations and comprehensive loss for the three months ended March 31, 2022 and 2021 (in thousands):

	Three Months Ended March 31,
	2022		2021
Research and development	$	375	$	415
General and administrative		515		462
	$	890	$	877

The following table summarizes equity‑based compensation expense by type of award for the three months ended March 31, 2022 and 2021 (in thousands):

	Three Months Ended March 31,
	2022		2021
Stock options	$	820	$	699
Restricted stock awards		53		172
Employee stock purchase plan		17		6
	$	890	$	877

During the three months ended March 31, 2022, the Company granted 2,342,899 stock options with a weighted average exercise price of $1.99. As of March 31, 2022, there was $7.5 million of unrecognized share-based compensation related to unvested stock option grants which is expected to be recognized over a weighted average period of 2.9 years. The total unrecognized share-based compensation cost will be adjusted for actual forfeitures as they occur.

During the three months ended March 31, 2022, the Company granted 507,260 restricted stock awards with a weighted average grant date fair value per share of $1.97. As of March 31, 2022, there was approximately $1.6 million of unrecognized share-based compensation related to restricted stock awards granted, which is expected to be recognized over a weighted average period of 3.5 years. The total unrecognized share-based compensation cost will be adjusted for actual forfeitures as they occur.

For a full description of the Company’s equity plans, refer to Note 9, Equity-based Compensation and Equity Incentive Plans in the 2021 Annual Report.