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Stock Plans (Tables)
9 Months Ended
Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]  
Schedule of our option activity
                    
           Weighted     
       Weighted   Average     
       Average   Remaining   Aggregate 
       Exercise   Option   Intrinsic 
   Options (in   Price per   Term   Value 
   thousands)   share   (in years)   (in thousands) 
Outstanding at December 31, 2021   682   $12.53    8.98   $ 
Granted   310    1.18           
Forfeited or expired   (53)   18.01           
Outstanding at September 30, 2022   939   $8.48    8.57   $ 
Exercisable at September 30, 2022   939   $8.48    8.57   $ 
Schedule of the stock-based compensation expense
                    
   Three Months Ended   Nine Months Ended 
(in thousands)  September 30,   September 30, 
   2022   2021   2022   2021 
Research and development  $306   $325   $553   $659 
Selling, general and administrative   217    330    414    691 
Total stock-based compensation  $523   $655   $967   $1,350 
Schedule of assumptions to estimate the fair value of options
                     
   Three Months Ended   Nine Months Ended 
   September 30,   September 30, 
   2022   2021   2022   2021 
Weighted-average risk-free interest rate   %   %   1.91%   0.5%
Expected dividend payments                
Expected holding period (years) 1           5.3    5.5 
Weighted-average volatility factor 2           1.16    1.14 
Estimated forfeiture rates for options granted 3   %   %   5.6%   30%

 

 

(1) Expected holding period is based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and the expectations of future employee behavior.
(2) Weighted average volatility is based on the historical volatility of our common stock.
(3) Estimated forfeiture rates are based on historical data.