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Stock-Based Compensation (Tables)
9 Months Ended
Sep. 30, 2022
Stock-Based Compensation  
Summary of stock option activity

Options Outstanding and Exercisable

Weighted

Weighted

Average

Aggregate

Average

Remaining

Intrinsic

Number of

Exercise

Contractual

Value(1)

    

Shares

    

Price

    

Life (Years)

    

(in thousands)

Outstanding as of December 31, 2021

4,545,794

$

14.15

8.1

$

2,860

Granted

 

1,722,350

$

5.37

 

 

Exercised

(50,420)

$

1.32

Forfeitures

(940,891)

$

13.79

Outstanding as of September 30, 2022

 

5,276,833

$

11.48

 

7.9

$

767

Exercisable as of September 30, 2022

 

2,607,339

$

12.83

 

6.8

$

767

(1)The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money at September 30, 2022 and December 31, 2021.
Summary of stock based compensation expense recorded

Three Months Ended

Nine Months Ended

September 30, 

September 30, 

(in thousands)

    

2022

    

2021

    

2022

    

2021

Research and development

$

779

$

1,054

$

2,274

$

3,068

General and administrative

 

1,533

 

1,429

 

4,908

 

4,710

Total stock-based compensation expense

$

2,312

$

2,483

$

7,182

$

7,778

Summary of assumptions used in the Black Scholes option pricing model for stock options granted

Nine Months Ended

September 30, 

    

2022

    

2021

Expected term

 

5.5 - 6.1

years 

5.5 - 6.1

years 

Expected volatility

 

79.7 - 81.4

%

79.7

%

Risk free interest rate

 

1.8 - 4.0

%

0.8 - 1.4

%

Expected dividend yield

 

%

%