On July 2, 2014, the stockholders of the Company approved the 2014 Stock Option and Incentive Plan (the “2014 Plan”), which became effective immediately prior to the completion of the Company’s IPO. The 2014 Plan provides for the grant of restricted stock awards, restricted stock units, incentive stock options and non-statutory stock options. The 2014 Plan replaced the Company’s 2011 Stock Option and Grant Plan (the “2011 Plan”). The Company no longer grants stock options or other awards under its 2011 Plan, but any stock options outstanding under the 2011 Plan remain outstanding and effective in accordance with their terms.

The 2014 Plan provides for an annual increase, to be added on the first day of each year, by up to 4% of the Company’s outstanding shares of common stock as of the last day of the prior year. On January 1, 2023, 2,380,365 shares of common stock, representing 4% of the Company’s outstanding shares of common stock as of December 31, 2022, were added to the 2014 Plan.

On December 15, 2016, the Board of Directors of the Company (the “Board”) approved the 2016 Inducement Equity Plan (as amended and restated, the “2016 Plan”). The 2016 Plan provides for the grant of equity awards to individuals who have not previously been an employee or a non-employee director of the Company to induce them to accept employment and to provide them with a proprietary interest in the Company. On September 20, 2018, the Board amended the 2016 Plan to increase the total number of shares reserved for issuance by 1,200,000 shares.

Terms of equity grants, including vesting requirements, are determined by the Board or the Compensation Committee of the Board, subject to the provisions of the applicable plan. Stock options granted by the Company that are not performance-based are considered time-based because they vest based on the continued service of the grantee with the Company during a specified period following grant. These awards, when granted to employees, generally vest ratably

over four years, with 25% vesting at the one-year anniversary. All stock option awards expire 10 years after the date of grant.

As of March 31, 2023, the total number of shares underlying outstanding awards under all equity plans was 10,793,166 and the total number of shares available for future issuance under all equity plans was 7,616,709 shares.

On June 16, 2022, the Company’s stockholders approved an amendment to the amended 2014 Employee Stock Purchase Plan (the “ESPP”), which had been previously approved by the Board, to add 300,000 shares of common stock to the ESPP.

The following table summarizes activity relating to time-based restricted stock units and performance restricted stock units:


	Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2022		1,415,481		$	48.73
Granted		1,153,335			42.78
Vested		(138,923	)		67.47
Forfeited		(20,037	)		48.18
Outstanding as of March 31, 2023		2,409,856			44.81

During the year ended December 31, 2021, the Company granted 268,119 time-based restricted stock units to certain employees of the Company that vest over four years. In September 2022, 25% vested on the one-year anniversary of the vesting start date and the remaining 75% vest ratably in quarterly increments over the remaining three years. During the three months ended March 31, 2023, 14,494 of these time-based restricted stock units vested, with a fair value of $0.6 million on the date of vesting.

During the three months ended March 31, 2022, no time-based restricted stock units vested.

During the three months ended March 31, 2023, the Company granted 330,617 time-based restricted stock units to certain employees and consultants of the Company. These time-based restricted stock units vest over four years, with 25% vesting at the one-year anniversary of the vesting start date and the remaining 75% will vest in equal installments on each anniversary of the vesting start date for the following three years.

During the three months ended March 31, 2022, the Company granted no time-based restricted stock units.

As of March 31, 2023, 470,891 time-based restricted stock units were both outstanding and unvested, and the total unrecognized stock-based compensation expense related to these awards was $19.4 million.

During the three months ended March 31, 2023 and 2022, the Company granted 822,718 and 415,565 performance restricted stock units, respectively, to its employees and consultants. The majority of the performance restricted stock units granted during the three months ended March 31, 2023 and 2022 vest upon the achievement of certain clinical and regulatory development milestones related to product candidates and certain commercial milestones. Certain performance restricted stock units granted in the three months ended March 31, 2023 vest upon the Company reaching specified measures of total stockholder return.

Recognition of stock-based compensation expense associated with performance restricted stock units, except for those with milestones that are measures of total stockholder return, commences when the performance condition is considered probable of achievement, using management’s best estimates, which consider the inherent risk and uncertainty regarding the future outcomes of the milestones. Recognition of stock-based compensation associated with performance restricted stock units with milestones that are measures of total stockholder return commences on the grant date and is recorded independently of the vesting outcomes of the grants.

As of three months ended March 31, 2023 and 2022, for performance restricted stock units that were outstanding, except for those with milestones that are measures of total stockhholder return, the achievement of the milestones that had not been met was considered not probable, and therefore no expense has been recognized related to these awards during the three months ended March 31, 2023 and 2022, respectively.

During the three months ended March 31, 2023, one milestone for outstanding performance restricted stock units was achieved. The fair value of the performance restricted stock units that vested upon achievement was $5.5 million and the Company recognized stock-based compensation expense related to this milestone of $8.5 million. 27% of the performance restricted stock units that were granted during the year ended December 31, 2021 included this milestone as a vesting condition.

No performance restricted stock units vested during the three months ended March 31, 2022.

As of March 31, 2023, 1,938,965 performance restricted stock units were both outstanding and unvested, and the total unrecognized stock-based compensation expense related to these awards was $87.3 million.

The following table summarizes activity related to time-based and performance-based stock options:


	Shares			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2022		7,788,350		$	77.95		6.36	$	7,275
Granted		712,041		$	44.58
Exercised		(45,908	)	$	5.45
Forfeited		(71,173	)	$	96.42
Outstanding as of March 31, 2023		8,383,310		$	75.36		6.46	$	12,177
Exercisable as of March 31, 2023		5,318,637		$	84.92		5.19	$	8,365

As of March 31, 2023, the Company had unrecognized stock-based compensation expense related to its outstanding and unvested time-based stock option awards of $68.4 million, which is expected to be recognized over the remaining weighted average vesting period of 3.07 years.

The intrinsic value of stock options exercised during the three months ended March 31, 2023 and 2022 was $1.7 million and $3.2 million, respectively.

Recognition of stock-based compensation expense associated with performance-based stock options commences when the performance condition is considered probable of achievement, using management’s best estimates, which consider the inherent risk and uncertainty regarding the future outcomes of the milestones.

As of March 31, 2023 and 2022, for performance-based stock option grants that were outstanding, the achievement of the milestones that had not been met was considered not probable, and therefore no expense has been recognized related to these awards during the three months ended March 31, 2023 and 2022, respectively.

During the three months ended March 31, 2023 and 2022, the Company granted no stock options to purchase shares of common stock that contain performance-based vesting criteria.

During the three months ended March 31, 2023 and 2022, no milestones were achieved under performance-based stock options.

As of March 31, 2023, 650,000 performance-based stock options were both outstanding and unvested, the total unrecognized stock-based compensation expense related to these awards was $8.6 million and the timing of recognition of this stock-based compensation expense is subject to judgment of the Company as to when the performance conditions are considered probable of being achieved.

The following table summarizes stock-based compensation expense recognized during the three months ended March 31, 2023:


	Three Months Ended March 31,
	2023		2022
	(in thousands)
Research and development	$	8,773	$	8,615
Selling, general and administrative		11,265		9,938
	$	20,038	$	18,553

The following table summarizes stock-based compensation expense by award type recognized during the three months ended March 31, 2023:


	Three Months Ended March 31,
	2023		2022
	(in thousands)
Stock options	$	10,015	$	15,465
Restricted stock units		9,553		2,803
Employee stock purchase plan		470		285
	$	20,038	$	18,553

For stock option awards, the fair value is estimated at the grant date using the Black-Scholes option-pricing model, taking into account the terms and conditions upon which stock options are granted. The fair value of the stock options is amortized on a straight-line basis for stock option awards to employees, non-employee directors and non-employee consultants over the requisite service period of the awards.

The weighted average grant date fair value per share of stock options granted under the Company’s stock option plans during the three months ended March 31, 2023 and 2022 was $29.65 and $27.93, respectively.