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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)
9 Months Ended
Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]  
Summary of allocation of stock-based compensation expense included in operating expenses on condensed statements of operations related to share-based payment awards The following table summarizes the stock-based compensation expense included in operating expenses on our condensed statements of operations related to stock options and employee stock purchases for the three and nine months ended September 30, 2021 and 2020, which was allocated as follows:

 

 

 

 

Three Months Ended September 30,

 

 

Nine Months Ended September 30,

 

(In thousands)

 

2021

 

 

2020

 

 

2021

 

 

2020

 

Research and development

 

$

924

 

 

$

623

 

 

$

2,655

 

 

$

1,703

 

General and administrative

 

 

1,084

 

 

 

1,145

 

 

 

3,120

 

 

 

3,340

 

Stock-based compensation expense included in operating expenses

 

$

2,008

 

 

$

1,768

 

 

$

5,775

 

 

$

5,043

 

 

Schedule of assumptions used to estimate the fair value of service-based stock options granted The fair value of service-based options granted during the nine months ended September 30, 2021 and 2020 has been estimated at the date of grant using the Black Scholes option-pricing model with the following assumptions:

 

 

Nine Months Ended September 30,

 

 

2021

 

2020

Dividend yield

 

0%

 

0%

Expected volatility range

 

0.777 to 0.783

 

0.781 to 0.793

Risk-free interest rate range

 

0.51% to 0.94%

 

0.31% to 1.62%

Expected term

 

5.5 yrs

 

5.25 yrs

Schedule of assumptions used to estimate the fair value of employee stock purchases under the purchase plan

The fair value of employees’ purchase rights during the nine months ended September 30, 2021 and 2020 has been estimated using the Black Scholes option-pricing model with the following assumptions:

 

 

Nine Months Ended September 30,

 

 

2021

 

2020

Dividend yield

 

0%

 

0%

Expected volatility range

 

0.507 to 0.707

 

0.478 to 0.818

Risk-free interest rate range

 

0.09% to 0.16%

 

0.16% to 1.57%

Expected term range

 

6 mos to 12 mos

 

6 mos to 12 mos