v3.22.4
Stock-Based Compensation (Tables)
 12 Months Ended
Dec. 31, 2022
Share-based Payment Arrangement [Abstract]  
Summary of Option Activity
A summary of option activity under the Plans for the year ended December 31, 2022 is as follows:

(in thousands, except for share and per share amounts)
Number of
Shares		Weighted Average
Exercise Price at Grant Date		Weighted Average
Remaining Term
(Years)		Aggregate
Intrinsic
Value
Outstanding at December 31, 20213,721,148 $14.16 5.77$11,327 
Granted745,028 11.10 
Expired(14,000)11.95 
Exercised(219,966)3.34 1,579 
Outstanding at December 31, 20224,232,210 14.19 5.81— 
Exercisable at December 31, 20222,969,040 14.43 4.62— 
Vested and expected to vest at December 31, 20224,104,620 14.23 5.72— 
Summary of RSU Activity
A summary of RSU activity for the Plans for the year ended December 31, 2022 is as follows:
Number of
Shares		Weighted
Average
Grant Date Fair Value
Unvested at December 31, 20211,764,740 $17.27 
Granted944,374 11.24 
Forfeited(130,625)14.48 
Vested(662,943)17.49 
Unvested at December 31, 20221,915,546 14.41 
Stock-Based Compensation Expense Stock-based compensation expense recognized for the years ended December 31, 2022, 2021 and 2020 comprised of the following:
 Year Ended December 31,
(in thousands)202220212020
Research and development$3,964 $3,955 $3,804 
Selling, general and administrative12,315 11,419 9,556 
Total stock-based compensation expense$16,279 $15,374 $13,360 
Black-Scholes-Merton Option Pricing Model for Employee and Director Stock Options Granted Assumptions used in the Black-Scholes-Merton option pricing model for employee and director stock options granted during the years ended December 31, 2022, 2021 and 2020 were as follows:
 Year Ended December 31,
 202220212020
Expected dividend yield— %— %— %
Weighted average expected volatility46 %46 %51 %
Weighted average expected term (years)6.055.986.07
Weighted average risk-free rate2.03 %0.75 %1.14 %