Stock incentive plans

6 Months Ended

Jun. 30, 2022

Stock incentive plans

Stock incentive plans

8.           Stock incentive plans

On June 5, 2018, the Company’s stockholders approved the 2018 Stock Option and Incentive Plan (the “2018 Plan”), which became effective on June 20, 2018.

Stock-based compensation expense

Non-cash stock-based compensation expense recognized in the accompanying condensed statements of operations relating to stock options, restricted stock awards, and restricted stock units for the three and six months ended June 30, 2022 and 2021, was as follows (in thousands):

	Three months ended				Six months ended
	June 30,				June 30,
	2022		2021		2022		2021
Research and development	$	444	$	676	$	819	$	1,413
General and administrative		1,837		1,802		3,812		3,720
Total stock‑based compensation expense	$	2,281	$	2,478	$	4,631	$	5,133

Stock options

The table below summarizes activity related to stock options (in thousands, except per share amounts):

				Weighted‑
		Weighted‑		average
		average		remaining	Aggregate
		exercise		contractual	intrinsic
Options	Shares	price		term	value
Outstanding, December 31, 2021	10,713	$	5.36	8.07	$	718
Granted	2,286		2.98
Exercised	—		—
Forfeited and canceled	(383)		3.97
Outstanding, June 30, 2022	12,616	$	4.97	7.82	$	19
Vested and expected to vest at June 30, 2022	12,616	$	4.97	7.82	$	19
Exercisable at June 30, 2022	6,282	$	6.64	6.61	$	2

During the six months ended June 30, 2022 and 2021, the Company granted 2.3 million and 3.1 million stock options, respectively, and these options had a weighted-average grant-date fair value of $2.28 and $2.73 per share, respectively. The weighted-average grant-date fair value of options was determined using the Black-Scholes option-pricing model. The assumptions used in the Black-Scholes option-pricing model for options granted during the six months ended June 30, 2022, were similar to those as described in the Annual Report, except for the manner in which the expected volatility was determined. The expected volatility for the Company’s options granted during the six months ended June 30, 2022, is based on a weighted-average of the historical volatility of share values of publicly traded companies within the biotechnology industry, which includes the historical volatility of the Company’s stock since the Company’s initial public offering. As of June 30, 2022, there was $14.6 million of total unrecognized stock-based compensation expense related to non-vested stock options, which is expected to be recognized over a weighted-average period of 2.7 years. The options have a ten-year life and generally vest over a period of four years, subject to continuous employment.

Restricted stock units

In June 2020, the Company issued an aggregate of 205,200 restricted stock units to employees. The restricted stock units issued in 2020 vested ten months from the date of grant. Such shares were not accounted for as outstanding until they vested. Non-cash restricted stock unit award expense recognized in the accompanying condensed statements of operations was $0.0 million and $0.2 million for the three months ended in June 30, 2022 and 2021, respectively, and $0.0 million and $0.8 million for the six months ended June 30, 2022 and 2021, respectively. There were no unvested restricted stock units as of June 30, 2022.