11. Stock Options, Restricted Stock and Stock-Based Compensation

Equity Incentive Plans

The Company’s 2015 Stock Plan, as amended, (the 2015 Plan) provides for the Company to sell or issue common shares or restricted common stock, or to grant incentive stock options or nonqualified stock options for the purchase of common stock, to employees, members of the board of directors and consultants of the Company. The 2015 Plan is

administered by the board of directors and exercise prices, vesting and other restrictions are determined at its discretion. All stock option grants are non-statutory stock options except option grants to employees intended to qualify as incentive stock options under the Internal Revenue Code of 1986, as amended. Incentive stock options may not be granted at less than the fair market value of the Company’s common stock on the date of grant, as determined in good faith by the board of directors at its sole discretion. Nonqualified stock options may be granted at an exercise price established by the board of directors at its sole discretion and the vesting periods may vary. Vesting periods are generally four years and are determined by the board of directors. Stock options become exercisable as they vest. Options granted under the 2015 Plan expire no more than ten years from the date of grant. As of December 31, 2024, there are no shares available for grants under the 2015 Plan and the 2015 Plan continues to govern the terms and conditions of the outstanding awards under the 2015 Plan.

On July 14, 2021, the Company’s 2021 Equity Incentive Plan (the 2021 Plan) was approved by the Company’s stockholders, and became effective upon completion of the IPO and serves as the successor to the 2015 Plan. 6,669,993 shares of common stock are reserved under the 2021 Plan, of which 2,008,379 shares remain available for future grants as of December 31, 2024.

Stock Options

Stock option activity is summarized as follows:

 

 

 

NUMBER OF
STOCK
OPTIONS

 

 

WEIGHTED-
AVERAGE
EXERCISE
PRICE

 

 

WEIGHTED-
AVERAGE
REMAINING
CONTRACTUAL
TERM (IN YEARS)

 

 

AGGREGATE
INTRINSIC
VALUE
(IN THOUSANDS)

 

Outstanding as of December 31, 2023

 

 

5,666,621

 

 

$

2.47

 

 

 

6.61

 

 

$

199

 

Granted

 

 

202,420

 

 

 

4.36

 

 

 

 

 

 

 

Exercised

 

 

(846,943

)

 

 

1.99

 

 

 

 

 

 

 

Cancelled, forfeited or expired

 

 

(535,917

)

 

 

3.36

 

 

 

 

 

 

 

Outstanding as of December 31, 2024

 

 

4,486,181

 

 

$

2.54

 

 

 

6.61

 

 

$

27,599

 

Exercisable as of December 31, 2024

 

 

3,515,651

 

 

$

2.40

 

 

 

6.20

 

 

$

22,116

 

Unvested as of December 31, 2024

 

 

970,530

 

 

$

3.04

 

 

 

8.10

 

 

$

5,483

 

 

The 2015 Plan permits participants to use common stock they previously acquired to pay for the exercise of stock options based upon the fair value on the date of exercise. In connection with the exercise of a stock options to purchase 306,518 shares of our common stock at an exercise price of $1.46, option holders tendered 122,608 shares of our common stock previously acquired in consideration of the full aggregate exercise price in accordance with the terms of the option and the 2015 Plan. The shares tendered are recorded as treasury stock within the Company's consolidated financial statements at December 31, 2024.

The fair value of stock options granted was estimated on the grant date using the Black-Scholes option pricing model based on the following range of assumptions:

 

 

YEAR ENDED DECEMBER 31,

 

 

2024

 

 

2023

 

Expected option life (years)

 

5.50 - 6.08

 

 

5.48 - 6.08

 

Risk-free interest rate

 

3.98% - 4.32%

 

 

3.50% - 4.86%

 

Expected volatility

 

99.30% - 114.68%

 

 

91.33% - 94.51%

 

Expected dividend yield

 

 

0

%

 

 

0

%

 

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the common stock as of the end of the period. The total intrinsic value of stock options exercised during the years ended December 31, 2024 and 2023 was $5.7 million and zero, respectively.

Restricted Stock Units

Under the terms of the restricted stock unit agreements covering the common stock, shares of common stock related to restricted stock units are subject to time-based vesting. The restricted stock units will immediately be forfeited to the Company if the relationship between the recipient and the Company ceases.

Restricted stock activity is summarized as follows:

 

 

NUMBER OF
SHARES
OPTIONS

 

 

WEIGHTED-
AVERAGE GRANT
DATE FAIR VALUE

 

Unvested at December 31, 2023

 

 

2,526,432

 

 

$

1.06

 

Granted

 

 

 

 

$

 

Vested

 

 

(1,936,460

)

 

$

1.07

 

Forfeited

 

 

(259,193

)

 

$

1.11

 

Unvested at December 31, 2024

 

 

330,779

 

 

$

0.98

 

 

The aggregate fair value of restricted stock units that vested during the years ended December 31, 2024 and 2023 was $16.8 million and $0.5 million, respectively.

Stock-Based Compensation

Stock-based compensation expense for the years ended December 31, 2024 and 2023 was classified in the consolidated statements of operations as follows (in thousands):

 

 

YEAR ENDED DECEMBER 31,

 

 

2024

 

 

2023

 

Research and development

 

$

3,276

 

 

$

1,347

 

General and administrative

 

 

2,036

 

 

 

1,744

 

Total stock-based compensation expense

 

$

5,312

 

 

$

3,091

 

 

As of December 31, 2024 and 2023, total unrecognized compensation cost related to the unvested stock-based awards was $1.9 million and $6.1 million, respectively. As of December 31, 2024 and 2023, these amounts are expected to be recognized over a weighted average period of 2.29 and 2.40 years, respectively.

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.