v3.25.4
Stock-based compensation (Tables)
12 Months Ended
Dec. 31, 2025
Share-Based Payment Arrangement [Abstract]  
Schedule of stock-based compensation expense

Total stock-based compensation recorded in the statements of operations and comprehensive loss related to stock options, restricted stock units and the ESPP (defined below) for employees and non-employees was as follows (in thousands):

  ​ ​ ​

Years Ended December 31,

2025

2024

Stock options

$

5,334

$

4,227

Restricted stock units

 

1,106

 

1,061

Employee stock purchase plan

9

Total stock-based compensation expense

$

6,449

$

5,288

Included in:

General and administrative expense

$

5,516

$

4,306

Research and development expense

 

933

 

982

Total stock-based compensation expense

$

6,449

$

5,288

Schedule of option activity transactions

The following table summarizes stock option activity (in thousands, except share and per share data):

  ​ ​ ​

  ​ ​ ​

  ​ ​ ​

Weighted- 

  ​ ​ ​

Number of 

Average 

Shares 

Weighted- 

Remaining 

Underlying 

Average 

Contractual 

Aggregate 

Outstanding 

Exercise 

Term 

Intrinsic 

Options

Price

(in Years)

Value (1)

Outstanding, January 1, 2025

 

4,462,517

$

6.58

 

7.4

$

619

Granted

 

1,337,219

4.92

 

 

Exercised

(44,792)

6.14

Forfeited/expired

 

(32,618)

19.88

 

 

Outstanding, December 31, 2025(2)

 

5,722,326

$

6.12

 

7.1

$

3,799

Vested and expected to vest, December 31, 2025

 

5,722,326

$

6.12

 

7.1

$

3,799

Exercisable at December 31, 2025

 

3,685,879

$

6.55

 

6.3

$

1,424

(1)Aggregate intrinsic value represents the difference between the fair value of the Company’s Series A common stock on the last day of the fiscal period and the exercise price, multiplied by the number of options outstanding.
(2)Includes 477,467 performance-based options with a weighted-average exercise price of $6.44, all of which were fully vested and exercisable.
Schedule of restricted stock unit activity

Weighted-Average

  ​ ​ ​

Restricted

  ​ ​ ​

Grant Date

  ​ ​ ​

Stock Units

  ​ ​ ​

Fair Value

Outstanding, January 1, 2025

 

844,382

$

2.96

Granted

 

267,157

4.85

Vested/released

 

(281,462)

2.96

Outstanding, December 31, 2025

830,077

$

3.57

Schedule of fair value assumptions

  ​ ​ ​

Years Ended December 31,

2025

2024

Expected volatility

 

95 - 96

%  

91 - 96

%  

Risk-free interest rate

 

3.8 - 4.3

%  

3.6 - 4.5

%  

Dividend yield

 

 

 

Expected term (in years)

 

5.3 - 6.0

5.3 - 6.1