NOTE 12—EQUITY INCENTIVE PLANS AND STOCK-BASED COMPENSATION

2018 Equity Incentive Plan

In May 2018, the Company adopted the 2018 Equity Incentive Plan (the “2018 Plan”). The 2018 Plan serves as a successor to the 2004 Amended and Restated Equity Incentive Plan (the “2004 Plan”), the 2009 Stock Plan, as amended (the “2009 Plan”) and the 2014 Equity Incentive Plan, as amended (the “2014 Plan”) with any forfeited, expired or cancelled awards under those plans being absorbed into the 2018 Plan for future issuance. The terms of the 2018 Plan provide for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, other stock awards, and performance awards that may be settled in cash, stock, or other property. Stock options may be granted under the 2018 Plan with an exercise price not less than 100% of the fair market value of the common stock on the date of grant. Stock options under the 2018 Plan may be granted with terms of up to ten years and generally vest over a period of four years, with the exception of grants to non-employee directors and consultants where the vesting period is or may be shorter. The total number of shares of the Company’s common stock initially reserved for issuance under the 2018 Plan was equal to the sum of (i) 133,333 newly reserved shares, which included, as of April 30, 2018, 6,945 shares reserved and unallocated under the 2009 Stock Plan, and 22,336 shares reserved and unallocated under the 2014 Equity Incentive Plan, plus (ii) up to 192,341 additional shares that may be added to the 2018 Plan in connection with the forfeiture, expiration or cancellation of awards outstanding under the 2014 Plan, the 2009 Plan and the 2004 Plan as of May 31, 2018. Additionally, the number of shares of common stock that may be issued under the 2018 Plan shall increase on each January 1, beginning with January 1, 2019, and continuing through and including January 1, 2028 by an amount equal to the lesser of (i) 4% of the number of outstanding shares of

common stock on that date and (ii) an amount determined by the Company’s board of directors or compensation committee; provided, however, that in no event will the number of shares available for issuance under the 2018 Plan be increased to the extent such increase, in addition to any other increases proposed by the board of directors in the number of shares available for issuance under all other employee or director stock plan would result in the total number of shares then available for issuance under all employee and director stock plans exceeding 20% of the outstanding shares of the Company’s common stock on the first day of the applicable fiscal year. As of December 31, 2023, options to purchase 386,600 shares of common stock were available for future grants under the 2018 Plan.

2004 Employee Stock Purchase Plan

On January 1, 2017, an additional 606 shares were authorized for issuance under the 2004 Employee Stock Purchase Plan (the “2004 Purchase Plan”) pursuant to the annual automatic increase to the authorized shares under the 2004 Purchase Plan. The 2004 Purchase Plan contains consecutive, overlapping 24 month offering periods. Each offering period includes four six-month purchase periods. The price of the common stock purchased will be the lower of 85% of the fair market value of the common stock at the beginning of an offering period or at the end of the purchase period. For both the years ended December 31, 2023 and 2022, no shares were purchased by employees under the 2004 Purchase Plan. As of December 31, 2023 and 2022, 576 shares were authorized and available for issuance under the 2004 Purchase Plan.

Equity Incentive Plan

The following table summarizes information about stock option activity for years ended December 31, 2023 and 2022:

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As of December 31, 2023, stock options outstanding and exercisable by exercise price were as follows:

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The total intrinsic value of stock options exercised during both the years ended December 31, 2023 and 2022 was zero, as determined at the date of the option exercise.

Cash received from stock option exercises was zero, for both the years ended December 31, 2023 and 2022. The Company issues new shares of common stock upon exercise of options. In connection with the exercises, there is no tax benefit realized by the Company due to the Company’s current loss position.

Equity-Based Compensation Expense

Stock-based compensation expense, which consists of the compensation cost for employee stock options and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative in the consolidated statements of operations as follows (in thousands):

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As of December 31, 2023, the total unrecognized compensation cost related to unvested stock-based awards granted to employees under the Company’s 2018 equity incentive plan was approximately $4.7 million. This cost will be recorded as compensation expense on a ratable basis over the remaining weighted average requisite service period of approximately 2.41 years.

Valuation Assumptions

The Company estimated the fair value of stock options granted using the Black-Scholes option-pricing formula and a single option award approach. This fair value is being amortized ratably over the requisite service periods of the awards, which is generally the vesting period.

The fair value of employee stock options was estimated using the following weighted-average assumptions:

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