8. Stock-based compensation

2018 Equity incentive plan

Following the Company's IPO in October 2020, the remaining shares from the 2018 Equity Incentive Plan (the 2018 Plan) were made available for issuance under the 2020 Incentive Award Plan (the 2020 Plan). As of December 31, 2025, there are 55,234 options outstanding and exercisable under the 2018 Plan.

2020 Incentive award plan

The Company adopted the 2020 Plan effective October 15, 2020. The 2020 Plan provides for a variety of stock-based compensation awards, including stock options, stock appreciation rights, or SARs, restricted stock awards, restricted stock unit awards, performance bonus awards, performance stock unit awards, dividend equivalents, or other stock or cash-based awards. The Company has granted 1,771,959 shares subject to awards as of December 31, 2025 with 465,915 remaining available for future grant.

Following the effectiveness of the 2020 Plan, the Company will not make any further grants under the 2018 Plan. However, the 2018 Plan will continue to govern the terms and conditions of the outstanding awards granted under this plan. Shares of common stock subject to awards granted under the 2018 Plan that are forfeited or lapse unexercised and which following the effective date of the 2020 Plan are not issued under the 2018 Plan will be available for issuance under the 2020 Plan.

2024 Employment inducement award plan

The Company adopted the 2024 Employment Inducement Award Plan (the 2024 Plan) in September 2024 as an inducement material to entering employment in accordance with Nasdaq Listing Rule 5635(c)(4). The 2024 Plan is used exclusively for the grant of equity awards to individuals who were not previously employed by the Company. The 2024 Plan provides for issuance of non-qualified stock options only. The Company has granted 269,500 shares subject to awards as of December 31, 2025 with 348,584 remaining available for future grant.

2020 Employee stock purchase plan

The Company adopted the 2020 Employee Stock Purchase Plan (the 2020 ESPP) effective on October 15, 2020. The 2020 ESPP enables eligible employees of the Company to purchase shares of common stock at a discount to fair market value. The Company has initially reserved for issuance 14,756 shares of common stock pursuant to the 2020 ESPP. As of December 31, 2025, 133,682 grants of awards under this plan have been made.

During each of the years ended December 31, 2025 and 2024, the Company's 2020 ESPP compensation expense was $0.5 million. The assumptions that the Company used to determine the grant-date fair value of shares granted to participants were as follows, disclosed on a grant date basis:

 

 

 

2025

 

 

2024

 

 

 

 

 

 

 

 

Expected term (in years)

 

0.5 - 2.0 years

 

 

0.5 - 2.0 years

 

Risk-free interest rate

 

4.83% - 5.38%

 

 

2.58% - 5.38%

 

Dividend yield

 

 

-

 

 

 

-

 

Volatility

 

53.24% - 82.71%

 

 

50.36% - 73.67%

 

Weighted-average estimated fair value of purchase rights

 

$2.26 - $7.56

 

 

$4.00 - $15.14

 

Stock options

The exercise price for incentive stock options is at least 100% of the fair market value on the date of grant for stockholders owning less than 10% of the voting power of all classes of stock, or at least 110% of the fair market value for stockholders owning more than 10% of the voting power of all classes of stock. Options generally expire in 10 years and vest over periods determined by the Board, generally 48 months. Certain stock options referred to as “early exercise stock options” permit the holders to exercise the option in whole or in part prior to the full vesting of the option in exchange for unvested shares of Restricted Stock with respect to any unvested portion of the option so exercised.

During the years ended December 31, 2025 and December 31, 2024, the Company’s stock option compensation expense was approximately $4.4 million and $7.9 million, respectively, and there was no recognized

tax benefit in either year. As of December 31, 2025, unrecognized stock-based compensation expense related to stock options was $11.4 million, to be recognized over a weighted-average period of 3.02 years.

The assumptions that the Company used to determine the grant-date fair value of stock options granted to Participants were as follows, presented on a weighted-average basis:

 

 

 

2025

 

 

2024

 

 

 

 

 

 

 

 

Expected term (in years)

 

 

6.01

 

 

 

5.94

 

Risk-free interest rate

 

 

4.07

%

 

 

3.98

%

Dividend yield

 

 

-

 

 

 

-

 

Volatility

 

 

96.99

%

 

 

87.35

%

 

Stock option activity during the year ended December 31, 2025 and 2024 was as follows:

 

 

 

Shares
subject
to options

 

 

Weighted-
average
exercise
price

 

 

Weighted-
average
remaining
contractual
term (years)

 

 

Aggregate
Intrinsic
Value
(in thousands)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Outstanding as of December 31, 2024

 

 

627,685

 

 

$

35.93

 

 

 

8.50

 

 

$

10,611

 

Granted

 

 

1,159,434

 

 

 

11.42

 

 

 

 

 

 

 

Exercised

 

 

 

 

 

 

 

 

 

 

 

 

Forfeited or Expired

 

 

(58,382

)

 

 

61.79

 

 

 

 

 

 

 

Outstanding as of December 31, 2025

 

 

1,728,737

 

 

 

18.62

 

 

 

8.82

 

 

$

859

 

Options vested and expected to vest as of December 31, 2025

 

 

1,728,737

 

 

 

18.62

 

 

 

8.82

 

 

$

859

 

Options vested and exercisable as of December 31, 2025

 

 

488,305

 

 

 

34.67

 

 

 

7.74

 

 

$

95

 

 

The weighted-average grant date fair value of stock options granted was $8.83 per share during the year ended December 31, 2025. The weighted-average grant date fair value of stock options granted was $12.88 per share during the year ended December 31, 2024. The total intrinsic value of stock options exercised during the years ended December 31, 2025 and 2024 were not material.

During the years ended December 31, 2025 and 2024 the Company did not issue shares for unvested stock options. As of December 31, 2025 and 2024, there were no shares of Common Stock held by employees subject to repurchase.

Restricted stock awards

The Company may grant restricted stock purchase awards to the Participants to purchase restricted stock under the Company’s Plan, which are subject to vesting conditions. The purchase prices of the restricted stock are determined by the Board. The Company has a right to repurchase the shares if the Participant’s service period is not fulfilled or upon termination of service at the original per share issuance price. The right of repurchase lapses over a service period which is typically four years with 25% vesting on the first anniversary of the vesting commencement date and 1/48 each month thereafter.

Before the adoption of the Company’s Plan, the Company granted 20,118 restricted stock awards to employees and founders. These restricted stock awards have similar characteristics to the restricted stock awards granted under the Company’s Plan, other than the right of repurchase, which typically lapses over three years with 33% vesting on the first anniversary of the vesting commencement date and 1/36 each month thereafter.

During each of the years ended December 31, 2025 and 2024, the Company recorded a total stock-based compensation expense of $0.1 million, related to the restricted stock awards. The number of restricted stock awards vested includes shares of common stock that the Company withheld on behalf of employees or sold to cover to

satisfy the minimum statutory tax withholding requirements. As of December 31, 2025, there was $0.7 million unrecognized stock-based compensation costs related to outstanding unvested restricted stock awards that are expected to vest over 3.37 years.

The following table summarizes the Company’s restricted common stock activity for years ended December 31, 2025 and 2024:

 

 

 

Number
of Awards

 

 

Weighted-
Average
Grant Date
Fair Value

 

 

Aggregate
Fair Value
(in thousands)

 

 

 

 

 

 

 

 

 

 

 

Issued and unvested as of December 31, 2024

 

 

4,729

 

 

$

15.44

 

 

$

74

 

Granted

 

 

74,955

 

 

 

10.11

 

 

 

758

 

Vested and released

 

 

(2,898

)

 

 

16.47

 

 

 

(48

)

Issued and unvested as of December 31, 2025

 

 

76,786

 

 

$

10.20

 

 

$

784

 

 

Stock-based compensation expense was allocated as follows for the years ended December 31, 2025 and December 31, 2024:

 

 

 

Year Ended

 

 

 

 

December 31,

 

 

 

 

2025

 

 

2024

 

 

Research and development

 

$

2,712

 

 

$

4,842

 

 

General and administrative

 

 

2,332

 

 

 

3,610

 

 

Total

 

$

5,044

 

 

$

8,452

 

 

Historical Timeline

Fiscal YearFiled
2025Mar 5, 2026Showing above
2024Mar 10, 2025
2023Mar 12, 2024
2022Mar 9, 2023
2021Mar 10, 2022

About Stock Compensation Disclosures

Stock-based compensation disclosures detail the equity awards granted to employees and executives — including stock options, restricted stock units (RSUs), and performance shares — along with the valuation methods and assumptions used to expense them. This section reveals the true cost of talent retention and the alignment between management incentives and shareholder interests.

Key signals: total unrecognized compensation expense and its expected recognition period signal future earnings headwinds from already-granted awards. For stock options, examine Black-Scholes assumptions — expected volatility, risk-free rate, and expected term — as understating any of these reduces reported compensation expense. Compare stock compensation expense as a percentage of revenue against peers to assess dilution cost. Watch vesting schedules for acceleration clauses tied to change-of-control events. Performance-based awards with undemanding targets may indicate weak governance. Add back stock compensation to operating cash flow to calculate a more conservative free cash flow figure.