Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations was as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	2,571	$	3,045	$	7,182	$	9,803
General and administrative	2,160		2,836		7,271		14,127
Total stock-based compensation expense	$	4,731	$	5,881	$	14,453	$	23,930

The following is a summary of restricted stock unit awards activity for the nine months ended September 30, 2023:


	Shares	Weighted Average Grant Date Fair Value Per Share
Unvested restricted stock unit awards as of December 31, 2022	1,499,070	$	18.70
Issued	1,331,578	$	8.71
Vested	(262,588)	$	19.87
Forfeited	(462,777)	$	18.86
Unvested restricted stock unit awards as of September 30, 2023	2,105,283	$	12.20

The restricted stock units issued in the nine months ended September 30, 2023 include 437,842 units granted to certain employees that contain performance-based vesting provisions. The Company recognizes the fair value of the performance-based units through the expected achievement date if the performance-based vesting provisions are deemed probable.

As of September 30, 2023, total unrecognized compensation expense related to unvested restricted stock unit awards was $13.2 million, which the Company expects to recognize over a remaining weighted-average period of 2.54 years.

The following is a summary of stock option activity for the nine months ended September 30, 2023:


	Shares	Weighted Average Exercise Price		Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding at December 31, 2022	5,276,148	$	23.99	8.00	$	402
Granted	2,195,300	$	8.74
Exercised	(3,122)	$	3.38
Cancelled	(1,467,700)	$	30.95
Outstanding at September 30, 2023	6,000,626	$	16.72	7.83	$	342
Exercisable at September 30, 2023	2,449,032	$	22.72	6.34	$	279

As of September 30, 2023, total unrecognized compensation expense related to stock options was $28.1 million, which the Company expects to recognize over a remaining weighted-average period of 2.70 years.