Stock-based compensation

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Stock-based compensation expense for the three and nine months ended September 30, 2023 and 2022 was classified in the Company’s condensed consolidated statement of operations and comprehensive loss as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Stock-based compensation expense:
Research and development	$	3,906	$	2,636	$	9,133	$	10,024
General and administrative	4,294		3,375		11,743		13,073
Total stock-based compensation expense	$	8,200	$	6,011	$	20,876	$	23,097

Stock options

During the nine months ended September 30, 2023, the Company granted stock options for the purchase of 4,427,620 shares of common stock with a weighted average exercise price of $3.89 per share and a weighted average grant-date fair value of $2.86 per shares. As of September 30, 2023, the unrecognized compensation cost related to outstanding stock options was $42.9 million, which is expected to be recognized over a weighted-average period of 2.4 years.

Performance-based restricted stock units

During the three and nine months ended September 30, 2023, the Company did not grant any performance-based restricted stock units, or PSUs. 135,301 PSUs vested during the nine months ended September 30, 2023 upon their respective achievement of performance-based vesting criteria. Upon vesting, each PSU automatically converted into one share of the Company’s common stock. The Company indirectly repurchased 17,556 shares of its common stock through net-share settlement as consideration for employee tax withholding obligations arising upon vesting of the PSUs, which tax amounts were remitted to the applicable revenue authorities in cash. As of September 30, 2023, the unrecognized compensation cost related to outstanding PSUs with performance-based vesting criteria that are considered not probable of achievement was $6.4 million.

Time-based restricted stock units

During the three and nine months ended September 30, 2023, the Company issued restricted stock units, or RSUs, that were subject to time-based vesting conditions to its employees . These RSUs are valued on the grant date using the grant date market price of the underlying shares. Upon vesting, each RSU automatically converts into one share of the Company’s common stock.

The following table summarizes the Company’s RSU activity for the nine months ended September 30, 2023:


	Shares	Weighted-Average Grant Date Fair Value
Outstanding as of December 31, 2022	—	$	—
Issued	824,600	5.37
Vested	—	—
Forfeited	(68,640)	$	5.67
Outstanding as of September 30, 2023	755,960	$	5.35

As of September 30, 2023, the unrecognized compensation cost related to outstanding RSUs was $3.4 million, which is expected to be recognized over a weighted-average period of 3.4 years.