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, restricted stock unit (“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 31st 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 January 1, 2022, the number of shares of common stock that may be issued under the 2015 Plan was automatically increased by 2,449,137 shares. As of September 30, 2022, 3,019,432 shares remained available for grant under the 2015 Plan. The Company had 4,343,087 stock options and 1,585,184 RSUs outstanding as of September 30, 2022 under the 2015 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 September 30, 2022 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.

Upon the 2015 Plan becoming effective, no further grants can be made under the 2012 Plan. The Company granted stock options to purchase a total of 1,140,524 shares under the 2012 Plan, of which 473,977 were outstanding as of September 30, 2022. Stock options granted under the 2012 Plan expire after ten years.

The weighted average assumptions the Company used to estimate the fair value of stock options granted during the nine months ended September 30, 2022 and 2021 were as follows:

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.

The following table summarizes stock option activity for the nine months ended September 30, 2022:

The weighted average grant date fair value of stock options granted during the nine months ended September 30, 2022 was $9.83 per share.

Restricted Stock Units

The following table summarizes RSU activity for the nine months ended September 30, 2022:


		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, 2021	1,496,946	$	12.75
Granted	867,707		14.33
Vested	(526,706)		11.55	$	7,839
Forfeited and cancelled	(252,763)		12.30
Outstanding as of September 30, 2022	1,585,184	$	14.09

Stock-Based Compensation

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


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(In thousands)	2022		2021		2022		2021
Cost of revenue	$	307	$	206	$	837	$	787
Research and development		1,400		939		2,228		2,969
General and administrative		2,481		2,557		7,161		6,453
Total stock-based compensation expense	$	4,188	$	3,702	$	10,226	$	10,209

As of September 30, 2022, the Company had unrecognized stock-based compensation expense for stock options and RSUs of $25.5 million and $18.3 million, respectively, which is expected to be recognized over weighted average periods of 3.1 years and 2.9 years, respectively.