Stock-Based Awards

12 Months Ended

Dec. 31, 2023

Stock-Based Awards

Stock-Based Awards

9. Stock-Based Awards

2015 Equity Incentive Plan

In September 2015, the Company’s board of directors adopted the 2015 Equity Incentive Plan (the “2015 Plan”), and the Company’s stockholders approved the 2015 Plan. The 2015 Plan became effective in connection with the Company’s initial public offering in October 2015. Beginning at the time the 2015 Plan became effective, no further grants may be made under the Company’s 2012 Equity Compensation Plan, as amended and restated (the “2012 Plan”). The 2015 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, RSU awards, performance stock awards, cash-based awards and other stock-based awards. The number of shares initially reserved for issuance under the 2015 Plan was 1,643,872 shares of common stock. The number of shares of common stock that may be issued under the 2015 Plan will automatically increase on January 1 of each year ending on January 1, 2025, in an amount equal to the lesser of (i) 4.0% of the shares of the Company’s common stock outstanding on December 31 of the preceding calendar year or (ii) an amount determined by the Company’s board of directors. The shares of common stock underlying any awards that expire, are otherwise terminated, settled in cash or repurchased by the Company under the 2015 Plan and the 2012 Plan will be added back to the shares of common stock available for issuance under the 2015 Plan. As of December 31, 2023, 3,703,234 shares remained available for grant under the 2015 Plan. As of January 1, 2024, the number of shares of common stock that may be issued under the 2015 Plan was automatically increased by 2,835,795 shares. The Company had 5,668,063 stock options and 1,521,940 RSUs outstanding as of December 31, 2023 under the 2015 Plan.

2017 Inducement Plan

In July 2017, the Company’s board of directors adopted the 2017 Inducement Plan (the “2017 Inducement Plan”). The 2017 Inducement Plan is a non-stockholder approved stock plan adopted pursuant to the “inducement exception” provided under Nasdaq listing rules. The Company had 370,600 stock options outstanding as of December 31, 2023 under the 2017 Inducement Plan. All shares of common stock that were eligible for issuance under the 2017 Inducement Plan after October 1, 2018, including any shares underlying any awards that expire or are otherwise terminated, reacquired to satisfy tax withholding obligations, settled in cash or repurchased by the Company in the future that would have been eligible for re-issuance under the 2017 Inducement Plan, were retired. 

2012 Equity Compensation Plan

In August 2012, the Company’s board of directors adopted the 2012 Equity Incentive Plan (“2012 Plan”), and the Company’s stockholders approved the 2012 Plan. Upon the 2015 Plan becoming effective, no further grants can be made under the 2012 Plan. The Company had 380,792 stock options outstanding as of December 31, 2023 under the 2012 Plan.

Stock Option Valuation

The weighted average assumptions the Company used to estimate the fair value of stock options granted during the years ended December 31, 2023, 2022 and 2021 were as follows:

	Year Ended
	December 31,
	2023		2022		2021
Risk-free interest rate	3.55	%	2.22	%	0.92	%
Expected term (in years)	6.2		6.2		6.2
Expected volatility	77.73	%	77.95	%	76.60	%
Expected dividend yield	0	%	0	%	0	%

The Company recognizes compensation expense for awards over their vesting period. Compensation expense for awards includes the impact of forfeitures in the period when they occur.

Stock Options

The following table summarizes stock option activity for the years ended December 31, 2023, 2022 and 2021:

				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
	Number	Exercise		Contractual	Intrinsic
(In thousands, except share and per share data and years)	of Shares	Price		Term	Value
				(in years)
Outstanding as of December 31, 2020	2,871,498	$	15.16	6.8	$	4,890
Granted	1,068,100		23.44
Exercised	(115,548)		12.63			1,373
Forfeited and cancelled	(31,600)		23.26
Outstanding as of December 31, 2021	3,792,450	$	17.50	6.8	$	13,710
Granted	2,548,750		14.40
Exercised	(88,172)		1.78			1,120
Forfeited and cancelled	(1,085,864)		18.44
Outstanding as of December 31, 2022	5,167,164	$	16.04	7.2	$	15,288
Granted	2,241,550		15.62
Exercised	(71,092)		1.31			473
Forfeited and cancelled	(918,167)		16.85
Outstanding as of December 31, 2023	6,419,455	$	15.94	7.1	$	14
Options vested and expected to vest as of December 31, 2023	6,419,455	$	15.94	7.1	$	14
Options exercisable as of December 31, 2023	2,879,529	$	16.55	5.1	$	14

The weighted average grant date fair value of stock options granted during the years ended December 31, 2023, 2022 and 2021 was $10.98, $9.95, and $15.67 per share, respectively.

Restricted Stock Units

The following table summarizes RSU activity for the years ended December 31, 2023, 2022 and 2021.

		Weighted
		Average
		Grant Date		Aggregate
	Number	Fair Value		Intrinsic
(In thousands, except share and per share data)	of Shares	Per Share		Value
Outstanding as of December 31, 2020	2,244,157	$	3.83
Granted	664,948		23.33
Vested	(1,340,042)		3.18	$	31,492
Forfeited and cancelled	(72,117)		10.36
Outstanding as of December 31, 2021	1,496,946	$	12.75
Granted	936,563		14.43
Vested	(533,212)		11.61	$	7,943
Forfeited and cancelled	(379,567)		13.40
Outstanding as of December 31, 2022	1,520,730	$	14.02
Granted	993,662		15.17
Vested	(745,279)		11.72	$	8,262
Forfeited and cancelled	(247,173)		15.15
Outstanding as of December 31, 2023	1,521,940	$	15.72

Stock-Based Compensation

Stock-based compensation expense included in total costs and expenses on the consolidated statement of operations included the following:

	Year Ended
	December 31,
(In thousands)	2023		2022		2021
Cost of revenue	$	1,456	$	1,151	$	981
Research and development		6,801		3,745		3,866
General and administrative		12,285		10,143		9,213
Total stock-based compensation expense	$	20,542	$	15,039	$	14,060

As of December 31, 2023, the Company had unrecognized stock-based compensation expense for stock options and RSUs of $30.0 million and $17.7 million, respectively, which is expected to be recognized over weighted average periods of 2.7 years and 2.6 years, respectively.