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Stock-Based Compensation (Tables)
9 Months Ended
Sep. 30, 2024
Summary of Assumptions Used in Black-Scholes Option Pricing Model

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Three Months Ended

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Nine Months Ended

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September 30, 

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September 30, 

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2024

    

2023

    

    

2024

    

2023

    

Risk-free interest rate

 

N/A

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4.20%

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4.12% - 4.34%

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3.38% - 4.22%

 

Expected volatility

 

N/A

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80.8%

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89.6% - 89.8%

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76.3% - 81.3%

 

Expected dividend yield

 

N/A

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0%

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0%

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0%

 

Expected life of employee and Board options (in years)

 

N/A

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6.25

 

 

6.25

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6.25

 

Summary of Stock Option Activity

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Weighted

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Number of

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Average Exercise

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Shares

    

 Price

    

Outstanding, December 31, 2023

 

7,897,647

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$

12.99

 

Granted

 

3,045,125

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0.86

 

Exercised

 

—

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—

 

Forfeited

 

(3,311,296)

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5.08

 

Expired

 

(3,371,914)

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14.92

 

Outstanding, September 30, 2024

 

4,259,562

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$

8.95

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Options exercisable, September 30, 2024

 

2,284,882

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Employees And Non-Employee Members Of Board Of Directors  
Summary of Restricted Stock Unit Activity

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Weighted

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Number of

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Average Grant

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Units

    

Date Fair Value

Outstanding, December 31, 2023

 

566,324

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$

9.27

Awarded

 

903,883

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0.66

Vested and released

 

(365,935)

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7.81

Forfeited

 

(136,348)

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10.57

Outstanding, September 30, 2024

 

967,924

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$

1.60

Restricted stock units exercisable (vested and deferred), September 30, 2024

 

—

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Employee Stock Option  
Summary of Compensation Expense Recognized

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Three Months Ended

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Nine Months Ended

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September 30, 

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September 30, 

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2024

    

2023

    

2024

    

2023

    

Research and development

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$

16

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$

1,387

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$

795

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$

4,314

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General and administrative

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1,120

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1,447

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3,494

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4,122

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Total stock option expense

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$

1,136

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$

2,834

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$

4,289

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$

8,436

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Restricted Stock Units  
Summary of Compensation Expense Recognized

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Three Months Ended

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Nine Months Ended

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September 30, 

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September 30,

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2024

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2023

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2024

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2023

Research and development

 

$

—

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$

90

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$

249

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$

385

General and administrative

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​

353

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410

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2,036

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​

1,308

Total restricted stock unit expense

 

$

353

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$

500

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$

2,285

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$

1,693