Share-based Compensation

12 Months Ended

Dec. 31, 2022

Share-based Payment Arrangement [Abstract]

We currently grant stock options, restricted stock awards, performance stock units and restricted stock units under the Amended and Restated 2021 Stock Plan (“2021 Stock Plan”), which was approved by the stockholders on May 5, 2021 and provides for the grant of up to 17.8 million shares of common stock to selected employees, consultants and non-employee members of our Board of Directors as stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and performance awards. Awards are subject to terms and conditions established by the Compensation Committee of our Board of Directors. During the year ended December 31, 2022, we granted share-based awards under the 2021 Stock Plan. At December 31, 2022, 6,550,075 shares were subject to outstanding awards and 14,764,481 shares were available for future grants of share-based awards.

Total share-based compensation expense related to share-based awards excluding the acceleration of Antares equity awards was comprised of the following (in thousands):


	Year Ended December 31,
	2022		2021		2020
Research and development	$	9,903	$	6,992	$	5,484
Selling, general and administrative	14,494		13,828		11,720
Share-based compensation expense	$	24,397	$	20,820	$	17,204

Share-based compensation expense by type of share-based award (in thousands):


	Year Ended December 31,
	2022		2021		2020
Stock options	$	10,973	$	10,252	$	8,955
RSAs, RSUs, PSUs and ESPP	13,424		10,568		8,249
	$	24,397	$	20,820	$	17,204

Total unrecognized estimated compensation cost by type of award and the weighted-average remaining requisite service period over which such expense is expected to be recognized (in thousands, unless otherwise noted):


	December 31, 2022
	Unrecognized Expense		Remaining Weighted-Average Recognition Period (years)
Stock options	$	26,730	2.66
RSUs	$	26,488	2.32
PSUs	$	3,986	1.91
ESPP	$	247	0.45

In February 2021, our Board of Directors approved our 2021 ESPP and our stockholders approved the plan in May 2021. The ESPP enables eligible employees to purchase shares of our common stock at the end of each offering period at a price equal to 85% of the fair market value of the shares on the first business day or the last business day of the offering period, whichever is lower. Share purchases are funded through payroll deduction of at least 1% and up to 15% of an employee’s compensation for each payroll period, and no employee may purchase shares under the ESPP that exceeds $25,000 worth of our common stock for a calendar year. As of December 31, 2022, 2,650,103 shares were available for future purchase. The offering period is generally for a six-months period and the first offering period commenced on June 16, 2021. Offering periods shall commence on or about the sixteenth day of June and December of each year and end on or about the fifteenth day of the next December and June respectively, occurring thereafter. During the twelve months ended December 31, 2022, 32,124 shares were issued pursuant to the ESPP.

Stock Options. Options granted under the Plans must have an exercise price equal to at least 100% of the fair market value of our common stock on the date of grant. The options generally have a maximum contractual term of ten years and vest at the rate of one-fourth of the shares on the first anniversary of the date of grant and 1/48 of the shares monthly thereafter. Certain option awards provide for accelerated vesting if there is a change in control (as defined in the Plans).

A summary of our stock option award activity as of and for the year ended December 31, 2022 is as follows:


	Shares Underlying Stock Options	Weighted Average Exercise Price per Share	Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in Millions)
Outstanding at December 31, 2021	4,965,374	$20.76
Granted	1,773,912	$37.25
Exercised	(789,870)	$19.40
Canceled/forfeited	(581,191)	$33.87
Outstanding at December 31, 2022	5,368,225	$24.99	6.48	$171.3
Vested and expected to vest at December 31, 2022	5,368,225	$24.99	6.48	$171.3
Exercisable at December 31, 2022	3,176,691	$17.22	4.92	$126.0

The weighted average grant date fair values of options granted during the years ended December 31, 2022, 2021 and 2020 were $14.22 per share, $18.21 per share and $20.74 per share, respectively. The total intrinsic value of options exercised during the years ended December 31, 2022, 2021 and 2020 was approximately $21.6 million, $33.5 million and $49.7 million, respectively. Cash received from stock option exercises for the years ended December 31, 2022, 2021 and 2020 was approximately $15.3 million, $16.6 million and $66.2 million, respectively.

The exercise price of stock options granted is equal to the closing price of the common stock on the date of grant. The fair value of each option award is estimated on the date of grant using the Black-Scholes-Merton option pricing model (“Black-Scholes model”). Expected volatility is based on historical volatility of our common stock. The expected term of options granted is based on analyses of historical employee termination rates and option exercises. The risk-free interest rate is based on the U.S. Treasury yield for a period consistent with the expected term of the option in effect at the time of the grant. The dividend yield assumption is based on the expectation of no future dividend payments. The assumptions used in the Black-Scholes model were as follows:


	Year Ended December 31,
	2022	2021	2020
Expected volatility	39.91-50.81%	41.01-46.45%	47.57-51.82%
Average expected term (in years)	4.7	4.7	5.1
Risk-free interest rate	1.37-4.27%	0.36-1.20%	0.22-1.67%
Expected dividend yield	—	—	—

Restricted Stock Units. A RSU is a promise by us to issue a share of our common stock upon vesting of the unit. The RSUs will generally vest at the rate of one-fourth of the shares on each anniversary of the date of grant.

The following table summarizes our RSU activity during the year ended December 31, 2022:


	Number of Shares	Weighted Average Grant Date Fair Value	Weighted Average Remaining Contractual Term (yrs)	Aggregate Intrinsic Value (in Millions)
Outstanding at December 31, 2021	858,742	$29.54
Granted	706,096	$39.18
Vested	(320,767)	$26.68
Forfeited	(204,690)	$35.69
Outstanding at December 31, 2022	1,039,381	$35.76	1.25	$59.1

The estimated fair value of the RSUs was based on the closing market value of our common stock on the date of grant. The total grant date fair value of RSUs vested during the years ended December 31, 2022, 2021 and 2020 was approximately $8.6 million, $6.6 million and $10.1 million, respectively. The fair value of RSUs vested during the years ended December 31, 2022, 2021 and 2020 was approximately $11.3 million, $19.0 million and $14.0 million, respectively.

Performance Stock Units. A PSU is a promise by us to issue a share of our common stock upon achievement of a specific performance condition.

The following table summarizes our PSU activity during the year ended December 31, 2022:


	Number of Shares	Weighted Average Grant Date Fair Value
Outstanding at December 31, 2021	69,382	$40.66
Granted	129,773	$41.42
Vested	(2,565)	$63.41
Forfeited	(53,746)	$27.20
Outstanding at December 31, 2022	142,844	$46.01

The estimated fair value of the PSUs was based on the closing market value of our common stock on the date of grant. The fair value of PSUs vested during the years ended December 31, 2022 and 2021 was $0.2 million and $0.1 million, respectively.