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Stock-based Compensation (Tables)
12 Months Ended
Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Schedule of Activities Under Company's Stock Option Plans

The following table summarizes the Company's stock option activities:

 

 

 

 

 

 

Options Outstanding

 

 

 

 

 

 

Number of
Shares

 

 

Weighted-
Average
Exercise
Price Per
Share

 

 

Weighted-
Average
Remaining
Contractual
Life (years)

 

 

Aggregate
Intrinsic
Value

 

 

 

 

 

 

 

 

 

 

 

 

(in thousands)

 

Balances at December 31, 2021

 

 

12,192,216

 

 

$

9.42

 

 

 

 

 

 

 

Options granted

 

 

4,991,018

 

 

 

2.93

 

 

 

 

 

 

 

Options exercised

 

 

(102,221

)

 

 

0.98

 

 

 

 

 

 

 

Options cancelled

 

 

(3,791,175

)

 

 

7.25

 

 

 

 

 

 

 

Balances at December 31, 2022

 

 

13,289,838

 

 

 

7.67

 

 

 

6.2

 

 

$

29.3

 

Options Exercisable—December 31, 2022

 

 

7,429,335

 

 

$

10.22

 

 

 

5.0

 

 

$

10.3

 

Total Stock-based Compensation Recognized

Total stock-based compensation recorded related to stock options, TRSUs, PSUs and the ESPP was as follows (in thousands):

 

 

 

Year Ended December 31,

 

 

 

2022

 

 

2021

 

Research and development

 

$

5,544

 

 

$

5,797

 

General and administrative

 

 

7,581

 

 

 

7,370

 

Total stock-based compensation expense

 

$

13,125

 

 

$

13,167

 

Schedule of Estimated Fair Value of Employee Stock Options and ESPP Using Black-Scholes Valuation Model

The Company estimated the fair value of employee stock options and ESPP using the Black-Scholes valuation model based on the date of grant with the following assumptions:

 

 

 

Options

 

ESPP

 

 

Year Ended December 31,

 

Year Ended December 31,

 

 

2022

 

2021

 

2022

 

2021

Expected volatility

 

74.6% - 83.3%

 

69.6% - 74.8%

 

93.3% - 96.1%

 

46.9% - 69.6%

Risk-free interest rate

 

1.6% - 4.3%

 

0.5% - 1.3%

 

1.6% - 4.7%

 

0.04% - 0.10%

Dividend yield

 

 %

 

 %

 

 %

 

 %

Expected term
   (in years)

 

4.3 - 4.6

 

4.5 - 4.8

 

0.5

 

0.5

 

Time based RSUs  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Schedule of Company's TRSU Activities

The following table summarizes the Company's TRSU activities:

 

 

 

Number of
Shares

 

 

Weighted-
Average
Remaining
Contractual
Life (years)

 

 

Aggregate
Intrinsic
Value
(in thousands)

 

 

Weighted Average Grant Date Fair Value Per Share

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Balance at December 31, 2021

 

 

433,250

 

 

 

 

 

 

 

 

$

5.34

 

RSUs awarded

 

 

1,314,210

 

 

 

 

 

 

 

 

 

2.74

 

RSUs vested

 

 

(134,125

)

 

 

 

 

 

 

 

 

5.34

 

RSUs cancelled

 

 

(400,451

)

 

 

 

 

 

 

 

 

4.45

 

Balance at December 31, 2022

 

 

1,212,884

 

 

 

1.2

 

 

$

1,941

 

 

$

2.81

 

The Company recorded $1.2 million and $0.2 million of stock-based compensation expense related to the TRSUs for the year ended December 31, 2022 and 2021, respectively.
Performance based RSUs  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Schedule of Activities for Company's PSUs

The following table summarizes the Company's PSU activities:

 

 

 

Number of
Shares

 

 

Weighted-
Average
Remaining
Contractual
Life (years)

 

 

Aggregate
Intrinsic
Value
(in thousands)

 

 

Weighted Average Grant Date Fair Value Per Share

 

 

 

 

 

Balance at December 31, 2021

 

 

435,000

 

 

 

 

 

 

 

 

$

5.34

 

PSUs awarded

 

 

250,000

 

 

 

 

 

 

 

 

 

1.59

 

PSUs vested

 

 

(193,750

)

 

 

 

 

 

 

 

 

5.34

 

PSUs cancelled

 

 

(107,500

)

 

 

 

 

 

 

 

 

5.12

 

Balance at December 31, 2022

 

 

383,750

 

 

 

1.3

 

 

$

614

 

 

$

2.96

 

As of December 31, 2022, the unrecognized compensation expense with respect to PSUs granted was $0.1 million and is expected to be recognized over 1.25 years.