v3.25.4
Stock-based Compensation (Tables)
 12 Months Ended
Dec. 31, 2025
Share-Based Payment Arrangement [Abstract]  
Assumptions Used to Value Option Grants The assumptions used to value option grants to employees and non-employees for the years ended December 31, 2025, 2024 and 2023 were as follows:
202520242023
Expected term (in years)
4.6 – 5.5
4.6 – 5.0
5.0 – 6.2
Risk-free interest rate
4.4% – 4.4%
3.4% – 5.2%
3.4% – 4.4%
Expected volatility
107% – 114%
82% – 91%
62% – 64%
Expected dividend yield———
Weighted average fair value per share at grant date$1.17$1.03$1.01
Stock Option Activity
A summary of the stock option activity is presented in the table below:
Number
of Options 		Weighted Average
Exercise Price
(per share)		Weighted Average
Remaining
Contractual Life
(in years)		Aggregate
Intrinsic Value
(in thousands)
Outstanding at December 31, 202420,803,142$2.61 7.8$11,507 
Granted1,166,855 1.44 
Exercised(830,228)2.31 
Forfeited(2,009,819)3.36 
Outstanding at December 31, 202519,129,950$2.47 7.1$22 
Exercisable at December 31, 202510,796,502 $2.81 6.4$22 
Vested and expected to vest at December 31, 202519,129,950 $2.47 7.1$22 
RSU Activity
The number of shares and weighted average grant date fair values of restricted non-vested common stock at the beginning and end of 2025, as well as restricted stock units granted, vested, and forfeited during the year were as follows:
Number of Shares
Underlying RSUs 		Weighted Average
Grant-Date Fair
Value (per share)
Non-vested RSUs at December 31, 20247,179,009$1.39 
Granted8,535,7321.21
Vested(3,082,653)1.36
Forfeited(1,513,697)1.21
Non-vested RSUs at December 31, 202511,118,391$1.29 
Stock-Based Compensation Stock-based compensation expense for the years ended December 31, 2025, 2024 and 2023 is as follows (in thousands):
202520242023
Research and development$2,834 $2,659 $2,961 
Selling, general and administrative7,939 6,228 5,555 
Total stock-based compensation$10,773 $8,887 $8,516