Stock-Based Compensation

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

9. Stock-Based Compensation

Stock Options

A summary of stock option activity was as follows (in thousands, except weighted-average exercise price and contractual term amounts):

	Options Outstanding
	Number of Shares Underlying Outstanding Options			Weighted- Average Exercise  Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding — December 31, 2021		416		$	123.57
Options granted		157		$	8.27
Options cancelled		(86	)	$	98.78
Outstanding — June 30, 2022		487		$	90.74		7.01	$	—
Exercisable — June 30, 2022		275		$	132.11		5.35	$	—

Stock Awards

During the six months ended June 30, 2022, the Company issued 710 restricted stock units, or RSUs, to its employees. The RSUs vest 25% annually over 4 years commencing on the date of grant. The RSUs are measured at grant date fair value, at the market price of the Company’s common stock on the grant date. The Company records stock-based compensation expense related to the RSUs ratably over the employee respective requisite service period.

On January 20, 2021, the Company granted 80,378 performance-based restricted stock units, or PSUs, to employees. The PSUs vested 20% on January 3, 2022 and 80% upon the achievement of two goals that were achieved by January 3, 2022. The PSUs were measured at grant date fair value, using the market price of the Company’s common stock on the grant date of $59.60. The Company estimated that all vesting conditions were probable of being achieved and elected to recognize compensation expense for the PSUs as one aggregate award using the straight-line method over the estimated implicit service period from the grant date to January 3, 2022. The Company monitored the probability of achievement of the goals each reporting period and adjusted its estimates accordingly. During the three months ended June 30, 2022 and 2021, the Company recorded $0 and $0.9 million of expense, respectively, related to the PSUs. During the six months ended June 30, 2022 and 2021, the Company recorded $6,000 and $1.9 million of expense, respectively, related to the PSUs.

A summary of restricted stock unit activity was as follows (in thousands, except weighted-average grant-date fair value and contractual term amounts):

	Stock Awards (PSUs and RSUs)
	Shares			Weighted- Average Grant-Date Fair Value		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding — December 31, 2021		35		$	57.24
RSUs — Awarded		1		$	10.15
PSUs and RSUs — Vested		(17	)	$	59.32
PSUs and RSUs — Cancelled		(4	)	$	56.94
Outstanding — June 30, 2022		15		$	52.67		1.64	$	37

Total stock-based compensation expense related to the Company’s 2010 Equity Incentive Plan, 2014 Equity Incentive Plan, 2018 Inducement Plan, and the 2014 Employee Stock Purchase Plan was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	456	$	1,588	$	954	$	2,868
General and administrative		519		1,056		1,201		2,471
Total stock-based compensation	$	975	$	2,644	$	2,155	$	5,339