Note 8. Stock-Based Compensation

2024 Inducement Equity Incentive Plan

In September 2024, the Board of Directors (the Board) adopted the Company's 2024 Inducement Equity Incentive Plan (the Inducement Plan), and subject to the adjustment provisions of the Inducement Plan, reserved 1,200,000 shares of the Company’s common stock for issuance pursuant to equity awards granted under the Inducement Plan. The Inducement Plan allows the Company to make equity awards to prospective employees of the Company as an inducement to such individual's commencement of employment with the Company.

Total shares reserved and available for grant under the Inducement Plan as of December 31, 2024, are 1,188,000.

2021 Equity Incentive Plan

Under the Company's 2021 Equity Incentive Plan (2021 Plan), 4,000,000 shares of the Company’s common stock were initially reserved for issuance of equity awards to employees, directors, and consultants, under terms and provisions established by the Board. The number of shares of common stock available for issuance under the 2021 Plan automatically increases on the first day of January for a period of ten years, commencing on January 1, 2022, in an amount equal to the lesser of: 4,000,000 shares; 4% of the outstanding shares of the Company’s common stock as of the last day of the immediately preceding year; or such other amount as the Board may determine.

Total shares reserved and available for grant under the 2021 Plan as of December 31, 2024, are 1,791,393.

Stock Option Activity

The following table summarizes stock option activity:

 

 

Shares

 

 

Weighted-
Average
Exercise
Price

 

 

Weighted-
Average
Remaining
Contractual
Life

 

 

Aggregate
Intrinsic
Value

 

 

 

 

 

 

(in dollars)

 

 

(Years)

 

 

(In thousands)

 

Outstanding as of December 31, 2023

 

 

8,343,434

 

 

$

7.47

 

 

 

 

 

 

 

Granted

 

 

2,754,100

 

 

$

4.81

 

 

 

 

 

 

 

Exercised

 

 

(50,945

)

 

$

2.20

 

 

 

 

 

 

 

Cancelled

 

 

(1,792,613

)

 

$

8.47

 

 

 

 

 

 

 

Outstanding as of December 31, 2024

 

 

9,253,976

 

 

$

6.51

 

 

 

7.22

 

 

$

406

 

Exercisable as of December 31, 2024

 

 

5,339,995

 

 

$

7.29

 

 

 

6.56

 

 

$

406

 

The aggregate intrinsic value is the value of the Company’s closing stock price on the last trading day of the year in excess of the weighted-average exercise price multiplied by the number of options outstanding or exercisable. The total intrinsic value of options exercised during the years ended December 31, 2024 and 2023, was $74.9 thousand and $36.7 thousand, respectively.

The weighted-average grant-date fair value of options granted during the years ended December 31, 2024 and 2023 was $3.73 and $2.62 per share, respectively.

As of December 31, 2024, there was $16.2 million of unrecognized stock-based compensation cost related to stock options, which is expected to be recognized over an estimated weighted-average period of 2.3 years.

Stock Option Valuation

The fair value of the Company’s stock option awards is estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions:

The assumptions used to determine the fair value of options granted were as follows. Each of these inputs is subjective, involve inherent uncertainties, and generally requires significant judgment. The assumptions used to determine the fair value of the awards represent management’s best estimates.

 

 

Year Ended
December 31,

 

 

2024

 

2023

Expected term (in years)

 

5.5 – 6.1

 

5.5 – 6.1

Expected volatility

 

89% – 93%

 

93% – 95%

Risk-free interest rate

 

3.9% – 4.5%

 

3.4% – 4.5%

Expected dividend yield

 

%

 

%

Expected Term— The Company determines the expected term, which represents the period that stock-based awards are expected to be outstanding, in accordance with the simplified method due to its limited operating history, which is presumed to be the mid-point between the contractual term and the vesting period.

Expected Volatility— As there is limited trading history for the Company’s common stock, the Company determines its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company, including stage of product development and life science industry focus. The historical volatility is calculated based on a period of time commensurate with the expected term assumption.

Risk-Free Interest Rate— The Company bases the risk-free interest rate on U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term assumption.

Expected Dividend Yield— The expected dividend yield is assumed to be zero as the Company has never paid and has no plans to pay any dividends on its common stock.

Restricted Stock Units

Restricted stock units (RSUs) are awards that entitle the holder to receive freely tradable shares of the Company’s common stock upon the completion of a specific period of continued service. RSUs generally vest over a two to four year period and are subject to forfeiture if employment terminates prior to the release of vesting restrictions. RSUs are valued at the market price of the underlying common stock on the date of grant. The Company recognizes noncash compensation expense for the fair value of RSUs on a straight-line basis over the requisite service period of the awards. The following table summarizes activity of RSUs granted to employees with service-based vesting under the 2021 Plan.

 

 

Shares

 

 

Weighted
Average
Grant Date
Fair Value
per Share

 

 

Weighted-
Average
Remaining
Contractual
Life

 

 

Aggregate
Intrinsic
Value

 

 

 

 

 

 

(in dollars)

 

 

(Years)

 

 

(In thousands)

 

Unvested as of December 31, 2023

 

 

1,088,276

 

 

$

3.34

 

 

 

 

 

 

 

  Granted

 

 

1,314,865

 

 

$

4.52

 

 

 

 

 

 

 

  Vested

 

 

(692,096

)

 

$

3.51

 

 

 

 

 

 

 

  Forfeited

 

 

(356,867

)

 

$

4.32

 

 

 

 

 

 

 

Unvested as of December 31, 2024

 

 

1,354,178

 

 

$

4.14

 

 

 

1.21

 

 

$

1,936

 

As of December 31, 2024, there was $4.9 million of unrecognized stock-based compensation cost related to RSUs, which is expected to be recognized over an estimated weighted-average period of 2.2 years.

2021 Employee Stock Purchase Plan

Under the Company's 2021 Employee Stock Purchase Plan (ESPP), the Company initially reserved 800,000 shares for future issuance. The number of shares of common stock available for issuance under the ESPP automatically increases on the first day of each fiscal year beginning with 2022 in an amount equal to the lesser of: 800,000 shares; 1% of the outstanding shares of the Company’s common stock as of the last day of the immediately preceding year; or such other amount as the Board may determine. As of December 31, 2024, 1,665,077 shares were reserved for future issuance under the ESPP. Under the Company’s ESPP, employees are generally eligible to participate and can purchase shares on each purchase date established semi-annually through payroll deductions at the lower of 85% of the fair market value of the Company’s stock at the commencement of the offering period or each purchase date of the offering period. Each offering period spans 6 months. The ESPP permits eligible employees to purchase common stock through payroll deductions for up to 15% of qualified compensation, up to an annual limit of $25,000 per the Internal Revenue Service. The first offering period commenced in January 2022. For the years ended December 30, 2024 and 2023, the stock-based compensation expense for ESPP was not material.

Stock-Based Compensation

The following table summarizes stock-based compensation recognized in the Company’s statements of operations and comprehensive loss:

 

 

Year Ended
December 31,

 

 

 

2024

 

 

2023

 

Research and development

 

$

8,200

 

 

$

7,039

 

General and administrative

 

 

8,302

 

 

 

8,270

 

  Total stock-based compensation

 

$

16,502

 

 

$

15,309

 

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.