During the three and six months ended June 30, 2022, the Company’s stock option compensation expense was approximately $3.5 million and $6.9 million, respectively, and during the three and six months ended June 30, 2021, the Company’s stock option compensation expense was approximately $3.1 million and $5.8 million, respectively. There was no recognized tax benefit in either of the periods. As of June 30, 2022, the unamortized expense balance was $34.2 million, to be amortized over a weighted average period of 2.53 years.

Stock option activity during the six months ended June 30, 2022 is as follows:


	Shares subject to options			Weighted- average exercise price		Weighted- average remaining contractual term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of January 1, 2022		5,692,514		$	12.07	8.63		$	16,763
Granted		3,742,124		$	3.01
Exercised		(5,591	)	$	1.92
Cancelled		(416,678	)	$	10.08
Outstanding as of June 30, 2022		9,012,369		$	8.41		8.61	$	200

Options vested and expected to vest as of June 30, 2022		9,006,650		$	8.41		8.61	$	200
Options vested and exercisable as of June 30, 2022		2,766,840		$	9.90		7.82	$	200

The weighted-average grant date fair value of options granted during the three and six months ended June 30, 2022 was $0.91 and $2.10 per share, respectively, and during the three and six months ended June 30, 2021 was $17.70 and $17.61 per share, respectively.

During the three and six months ended June 30, 2022, the Company recorded total stock-based compensation expense related to restricted stock awards of $15,000 and $0.1 million, respectively. During the three and six months ended June 30, 2021, the Company recorded total stock-based compensation expense related to restricted stock awards of $0.1 million and $0.2 million, respectively. As of June 30, 2022, there was no unrecognized stock-based compensation expense related to outstanding unvested shares of restricted stock awards remaining.

The following table summarizes the Company’s restricted common stock activity for the six months ended June 30, 2022:


	Number of Awards			Weighted- Average Grant Date Fair Value		Aggregate Fair Value (in thousands)
Issued and unvested as of January 1, 2022		89,054		$	1.30	$	117
Restricted stock awards granted		—
Restricted stock awards vested		(85,337	)	$	1.30	$	(111	)
Issued and unvested as of June 30, 2022		3,717		$	1.30	$	6

During the six months ended June 30, 2022, the Company did not issue shares of common stock, upon exercise of unvested stock options or purchases for unvested restricted stock awards. During the six months ended June 30, 2021, the Company issued 262,982 shares of common stock, upon exercise of unvested stock options or purchases for unvested restricted stock awards. As of June 30, 2022 and December 31, 2021, there were 65,688 and 163,855 shares of Common Stock held by employees subject to repurchase at an aggregate price of approximately $0.1 million and $0.3 million, respectively. A corresponding liability was recorded and included in accrued expenses on the condensed consolidated balance sheet as of June 30, 2022 and December 31, 2021, respectively.

During the three and six months ended June 30, 2022, the Company recorded total stock-based compensation expense related to the employee stock purchase plan of $0.4 million and $0.7 million, respectively, and $0.2 million in the three months ended June 30, 2021. The employee stock purchase plan began in the second quarter of 2021, therefore there was no expense in the first quarter of 2021. During the three months ended June 30, 2022, 112,468 grants of awards under this plan have been made. No purchases of common stock were made during the first quarter of 2022, and during the three and six months ended June 30, 2021.

Stock-based compensation expense was allocated as follows for the three and six months ended June 30, 2022 and 2021 (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2022		2021		2022		2021
Research and development	$	2,199	$	1,974	$	4,200	$	3,683
General and administrative		1,795		1,474		3,580		2,521
Total	$	3,994	$	3,448	$	7,780	$	6,204