Share-Based Compensation

9 Months Ended

Sep. 30, 2022

Share-Based Payment Arrangement [Abstract]

Pursuant to the evergreen provisions of the Company's 2013 stock incentive plan (the “2013 Plan”), annual increases have resulted in the addition of an aggregate of approximately 15,624,000 additional shares to the 2013 Plan, including for 2022, an increase of approximately 2,542,000 shares. As of September 30, 2022, the Company had approximately 3,204,000 shares available for grant under the 2013 Plan.

In October 2019, the Company's board of directors adopted its 2019 Inducement Stock Incentive Plan (the “2019 Inducement Plan”) to reserve initially 1,000,000 shares of its common stock to be used exclusively for grants of awards to individuals who were not previously employees or directors of the Company as a material inducement to such individuals’ entry into employment with the Company within Rule 5635(c)(4) of the Nasdaq Listing Rules. The terms and conditions of the 2019 Inducement Plan are substantially similar to those of the 2013 Plan. In March 2020, the Company's board of directors amended the 2019 Inducement Plan to reserve an additional 1,000,000 shares of its common stock for issuance under the plan, and in February 2021, September 2021, December 2021 and May 2022, the Company's board of directors further amended the 2019 Inducement Plan to reserve an additional 600,000 shares, an additional 1,000,000 shares, an additional 1,000,000 shares and an additional 1,000,000 shares, respectively, of its common stock for issuance under the plan. As of September 30, 2022, the Company had approximately 1,245,000 shares available for grant under the 2019 Inducement Plan.

Share-based compensation expense, net of estimated forfeitures, includes expenses related to stock options and RSUs granted to employees, non-employee directors and consultants, as well as options granted to employees to purchase shares

under the ESPP. Stock-based compensation by award type was as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Stock options	$	4,021	$	1,485	$	11,095	$	3,997
Restricted stock units	2,444		1,101		7,020		2,896
Employee stock purchase plan	91		40		215		104
Total	$	6,556	$	2,626	$	18,330	$	6,997

The Company allocated stock-based compensation expense in the Company’s Consolidated Statements of Operations and Comprehensive Loss as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development	$	2,681	$	1,476	$	8,108	$	4,138
General and administrative	3,875		1,150		10,222		2,859
Total	$	6,556	$	2,626	$	18,330	$	6,997

Stock Options

A summary of the stock option activity, weighted average exercise prices, options outstanding, exercisable and expected to vest as of September 30, 2022 is as follows (in thousands except weighted average exercise price):


	Number of Shares Underlying Options	Weighted Average Exercise Price
Outstanding, December 31, 2021	10,861	$	10.94
Granted	1,388	$	14.23
Exercised	(1,797)	$	3.69
Forfeited	(202)	$	14.14


Outstanding, September 30, 2022	10,250	$	12.60
Vested and exercisable, September 30, 2022	4,830	$	13.38
Vested and expected to vest, September 30, 2022	9,762	$	12.63

As of September 30, 2022, there were approximately $37.4 million of unrecognized compensation costs, net of estimated forfeitures, related to stock option awards grants, which are expected to be recognized over a remaining weighted average period of 2.9 years.

RSUs

The following table presents a summary of the Company's outstanding RSU awards granted as of September 30, 2022 (in thousands except weighted average grant-date fair value):


	Restricted Stock Units	Weighted Average Grant-Date Fair Value
Outstanding, December 31, 2021	2,246	$	9.82
Awarded	494	$	11.79
Vested	(293)	$	8.32
Forfeited	(46)	$	10.95
Outstanding, September 30, 2022	2,401	$	10.39
Outstanding, expected to vest	2,185	$	10.39

As of September 30, 2022, there were approximately $16.8 million of unrecognized compensation costs, net of estimated forfeitures, related to RSUs grants, which are expected to be recognized over a remaining weighted average period of 2.5 years.

ESPPAs of September 30, 2022, there were 712,394 shares available for future purchases under the ESPP. There were 25,921 and 27,529 shares issued under the ESPP during the three months ended September 30, 2022 and 2021, respectively. There were 41,016 and 51,951 shares of common stock issued under the ESPP during the nine months ended September 30, 2022 and 2021, respectively. Cash proceeds from ESPP purchases were $331 thousand and $146 thousand during the three months ended September 30, 2022 and 2021, respectively. Cash proceeds from ESPP purchases were $515 thousand and $266 thousand during the nine months ended September 30, 2022 and 2021, respectively.