v3.25.2
Equity Incentive Plans (Tables)
 6 Months Ended
Jun. 30, 2025
Equity [Abstract]  
Schedule of Stock Option Plan Activity
The following table summarizes the stock option activity for the six months ended June 30, 2025:
Outstanding Options
Number of OptionsWeighted-Average
Exercise Price
Outstanding at December 31, 202414,263,242$2.93 
Granted1,104,000$0.78 
Exercised(26,500)$0.76 
Cancelled(1,442,640)$8.05 
Outstanding at June 30, 202513,898,102$2.23 
Schedule of Share-Based Compensation Expense
The following table summarizes share-based compensation expense related to share-based payment awards granted pursuant to all of our equity compensation arrangements (in thousands):
Three Months Ended June 30,Six Months Ended June 30,
2025202420252024
Research and development$253 $954 $584 $1,561 
General and administrative698 1,035 1,309 1,744 
Total share-based compensation expense$951 $1,989 $1,893 $3,305 
Schedule of Fair Value of Each Grant Using Weighted-Average Assumptions
The following are the weighted-average assumptions for stock options:
For the Six Months Ended June 30,
20252024
Risk-free interest rate4.1%4.4%
Dividend yield0.0%0.0%
Volatility105.7%103.7%
Expected life (years)610
Early exercise multiple (years)— 
2.2 - 2.8
Schedule of Weighted-Average Assumptions for Purchase Rights under ESPP The following are the weighted-average assumptions for purchase rights under our ESPP. There was no new offering period during the six months ended June 30, 2024.
For the Six Months Ended June 30, 2025
Risk-free interest rate4.1%
Dividend yield0.0%
Volatility109.0%
Expected life (months)
6 - 24