Total stock-based compensation expense recognized was as follows (in thousands):


	Three Months Ended March 31,
	2022		2021
Research and development	$	1,687	$	1,588
General and administrative		2,663		1,455
Total stock-based compensation	$	4,350	$	3,043

A summary of stock option activity for three months ended March 31, 2022 is set forth below:


	Number of Shares Underlying Outstanding Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2021		3,875,317		$	14.08		8.85	$	13,212
Options authorized		—
Options granted		1,555,000		$	14.59
Options exercised		(10,099	)	$	9.29
Options forfeited or cancelled		(44,073	)	$	14.21
Outstanding, March 31, 2022		5,376,145		$	14.24		8.89	$	30,825
Options exercisable, March 31, 2022		1,296,481		$	13.67		8.45	$	8,174
Vested and expected to vest, March 31, 2022		5,376,145		$	14.24		8.89	$	30,825

The assumptions used in the Black Scholes Model to calculate stock-based compensation are as follows:


	Three Months Ended March 31,
	2022	2021
Fair value of common stock	$11.93 - $19.97	$8.33 - $11.39
Expected term (years)	5.8 - 6.1	5.9 - 6.1
Volatility	77.4% - 77.7%	79.2% - 79.8%
Risk free rates	1.6% - 2.4%	0.7% - 0.9%
Dividend rate	0.0%	0.0%

In August 2021, the Company granted 210,750 restricted stock units (RSUs) to employees with a weighted-average grant date fair value of $7.12 per share.

In October 2021, the Company granted 560,000 RSUs with service and performance conditions to certain employees, 224,000 of which vested during the three months ended March 31, 2022. Vesting of these awards is contingent on the occurrence of certain milestone events and fulfilment of any remaining service condition. As a result, the related compensation cost is recognized as an expense when achievement of the milestone is considered probable. The expense recognized for these

awards is based on the grant date fair value of the Company's common stock multiplied by the number of units granted. The Company recognized $1.1 million of related expense during the three months ended March 31, 2022.

The summary of RSU activity and related information follows:


	Number of Units Outstanding			Weighted- Average Grant Date Fair Value
Outstanding, December 31, 2021		771,660		$	7.84
RSUs granted		—			-
RSUs Vested		(224,000	)	$	8.02
RSUs forfeited		(9,000	)	$	7.12
Outstanding, March 31, 2022		538,660		$	7.75

The Company has a 2014 Share Option Plan (the 2014 Plan), 2015 Stock Incentive Plan (the 2015 Plan), 2017 Stock Incentive Plan (the 2017 Plan), 2018 Stock Incentive Plan (the 2018 Plan), and 2018 Employee Stock Purchase Plan (the 2018 ESPP, and, collectively with the 2014 Plan, the 2015 Plan, the 2017 Plan and the 2018 Plan, the Plans). There have been no material changes in the Plans from those disclosed in Note 18 to the consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021.

As of March 31, 2022, the number of shares of common stock available for grant under the 2017 and 2018 Plan is 2,641,835 shares. As of March 31, 2022, an aggregate of 4,234,328 shares of common stock were issuable upon the exercise of outstanding stock options under the 2017 Plan and 2018 Plans at a weighted average exercise price of $15.03 per share. Included in this amount was a grant of 6,410 PSUs, 210,750 RSUs and 560,000 RSUs the Company granted in May 2021, August 2021 and October 2021, respectively.

As of March 31, 2022, the number of shares of common stock available for grant under the 2014 and 2015 Plans is 13,418. As of March 31, 2022, an aggregate of 1,171,193 shares of Former Adicet common stock were issuable upon the exercise of outstanding stock options under the 2015 plan at a weighted average exercise price of $11.89 per share and an aggregate of 185,396 shares of Former Adicet common stock were issuable upon the exercise of outstanding stock options under the 2014 Plan at a weighted average exercise price of $1.61 per share.

On January 1, 2022, as a result of the foregoing evergreen provision, the number of shares of common stock available for issuance under the 2018 ESPP automatically increased from 524,775 to 922,144 shares. No shares have been issued under the 2018 ESPP during the three months ended March 31, 2022.

As of March 31, 2022, an aggregate of 486,303 shares of common stock were issuable upon the exercise of inducement grants of stock options approved by the Company in accordance with Nasdaq listing Rule 5635(c)(4) at a weighted average exercise price of $14.52 per share.