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Stock-based Compensation
9 Months Ended
Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]  
Stock-based Compensation

9. Stock-based Compensation

 

Equity Incentive Plans

 

The following table summarizes stock-based compensation expense related to stock options, restricted stock awards (RSAs) granted to employees, non-employee directors and consultants, and the 2019 Employee Stock Purchase Plan (the 2019 ESPP) included in the condensed consolidated statements of operations as follows (in thousands):

 

   2023   2022   2023   2022 
   Three Months Ended
September 30,
   Nine Months Ended
September 30,
 
   2023   2022   2023   2022 
                 
Research and development  $30    150   $99    491 
Selling and marketing   42    144    146    459 
General and administrative   186    687    698    2,179 
Total  $258   $981   $943   $3,129 

 

Stock Options

 

There were no shares of stock options granted during the three and nine months ended September 30, 2023, respectively. As of September 30, 2023, unrecognized stock-based compensation expense for employee stock options was approximately $1.4 million, which the Company expects to recognize over a weighted-average remaining period of 1.9 years, assuming all unvested options become fully vested.

 

Restricted Stock Awards

 

There were no shares of performance-based RSAs granted in 2023 to the Company’s executive management team.

 

For performance-based RSAs, (i) the fair value of the award is determined on the grant date; (ii) the Company assesses the probability of achieving each individual milestone associated with the award using reasonable assumptions based on the Company’s operation performance towards each milestone; (iii) the fair value of the shares subject to the milestone is expensed over the implicit service period commencing once management believes the performance criteria is probable of being met; and (iv) the Company reassesses the probability of achieving each individual milestone at each reporting date, and any change in estimate is accounted for through a cumulative adjustment in the period when the change in estimate occurs. Non-performance based RSAs are valued at the fair value on the grant date and the associated expenses will be recognized over the vesting period.

 

As of September 30, 2023, there was no unrecognized noncash stock-based compensation expense related to unvested RSAs.

 

 

Employee Stock Purchase Plan

 

The purchase price under the 2019 ESPP is 85% of the lesser of the fair market value of the common stock on the first or the last business day of an offering period. The maximum number of shares of common stock that may be purchased by any participant during an offering period is equal to $0.025 million divided by the fair market value of the common stock on the first business day of an offering period. In October 2022, the Board terminated the offering period ending December 15, 2022, refunded all employee contributions, and suspended future offering periods.

 

There were no shares of common stock purchased under the 2019 ESPP during the three and nine months ended September 30, 2023 or 2022.

 

The fair market value of shares to be issued to employees under the 2019 ESPP is estimated using a Black-Scholes option-pricing model at the grant date, which requires the use of subjective and complex assumptions, including (i) the expected stock price volatility, (ii) the calculation of the expected term of the award, (iii) the risk-free interest rate and (iv) the expected dividend yield. The following weighted average assumptions were used in the calculation of fair value of shares under the 2019 ESPP at the grant dates for the three and nine months ended September 30, 2022. No grant date fair value calculation was performed during the three and nine months ended September 30, 2023.

 

   Three and Nine months ended September 30, 
   2022 
Expected volatility   177.2%
Risk-free interest rate   2.3%
Expected dividend yield   0.0%
Expected term (years)   0.5