8. STOCK-BASED COMPENSATION

Equity Plans

In 2011, Private Tempest adopted the 2011 Equity Incentive Plan (the “2011 Plan), and in 2017, Private Tempest adopted the 2017 Equity Incentive Plan (the “2017 Plan”), and together with the 2011 Plan, the “Tempest Prior Plans.” The Tempest Prior Plans have been terminated and no additional grants may be made under either plan. All stock awards granted under the Tempest Prior Plans will remain subject to the terms of the applicable prior plan. As a result of the merger with Millendo, the Tempest Prior Plans were assumed by the Company.

On April 29, 2019, the Board of Millendo adopted the 2019 Equity Incentive Plan (the “2019 Plan”), subject to approval by the Company’s stockholders, and became effective with such stockholder approval on June 11, 2019. On June 17, 2022, the Company’s stockholders approved the Amended and Restated 2019 Equity Incentive Plan (the “A&R 2019 Plan”), which amended and restated the 2019 Plan and was the successor to, and replacement of, the 2019 Plan.

The Board of Tempest adopted the Amended and Restated 2023 Equity Incentive Plan (the “2023 Plan”) on April 30, 2023, subject to approval by the Company’s stockholders. On June 15, 2023, the Company’s stockholders approved the 2023 Plan, which amended and restated the A&R 2019 Plan and will be a successor to, and replacement of, the A&R 2019 Plan. The number of shares of the Company's common stock reserved for issuance under the 2023 Plan will automatically increase on January 1st of each year, for a period of 10 years, from January 1, 2024 continuing through January 1, 2033, by 4% of the total number of shares of the Company's common stock outstanding on December 31st of the preceding calendar year, or a lesser number of shares as may be determined by the Board of Directors. Accordingly, on January 1, 2026, the common stock reserved for issuance was increased by 197,086 shares. As of June 30, 2026, there were 1,304,070 shares available for future grant under the 2023 Plan. In addition, on January 27, 2026, the Company's stockholders approved the amendment to increase the number of shares issuable under the 2023 Plan by 1,410,000 shares of common stock.

The 2023 Plan allows the Company to grant stock awards to employees, directors and consultants of the Company, including incentive stock options (“ISOs”), non-qualified stock options (“NSOs”), stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock awards.

The Board of Tempest adopted the 2023 Inducement Plan (“2023 Inducement Plan”) on June 21, 2023, pursuant to which the Company reserved 88,461 shares of its common stock to be used exclusively for grants of awards to individuals who were not previously employees or directors of the Company, as an inducement material to the individual’s entry into employment with the Company within the meaning of Rule 5635(c)(4) of the Nasdaq Listing Rules. The 2023 Inducement Plan was approved by the Company’s Board of Directors without stockholder approval in accordance with such rule. As of June 30, 2026, there were 67,615 shares available for future grant under the 2023 Inducement Plan.

The Company measures employee and non-employee stock-based awards at grant date fair value and records compensation expense on a straight-line basis over the vesting period of the award.

Employee Stock Ownership Plan

The Millendo Board adopted the 2019 Employee Stock Purchase Plan on April 29, 2019, which became effective upon stockholder approval on June 11, 2019. On June 17, 2022, the Company’s stockholders approved the Amended and Restated 2019 Employee Stock Purchase Plan (the “2019 ESPP”). The 2019 ESPP enables employees to purchase shares of the Company's common stock through offerings of rights to purchase the Company's common stock to all eligible employees.

The 2019 ESPP provides that the number of shares of common stock reserved for issuance under the 2019 ESPP will automatically increase on January 1, 2023 and continuing through (and including) January 1, 2029, by the lesser of 1.5% of the total number of shares of Common Stock outstanding on December 31st of the preceding calendar year, (ii) 38,461 shares of Common Stock, or (iii) such lesser number of shares of Common Stock as determined by the Board of Directors (which may be zero). On January 1, 2026, the common stock reserved for issuance was increased by 38,461 shares.

As of June 30, 2026, 107,069 shares of common stock remained available for future issuance under the 2019 ESPP. During the three and six months ended June 30, 2026, no shares of common stock were issued under the 2019 ESPP.

Stock Options

Options to purchase the Company’s common stock may be granted at a price not less than the fair market value in the case of both NSOs and ISOs, except for an options holder who owns more than 10% of the voting power of all classes of stock of the Company, in which case the exercise price shall be no less than 110% of the fair market value per share on the grant date. Stock options granted under the Plans generally vest over four years and expire no later than ten (10) years from the date of grant. Vested options can be exercised at any time.

During the six months ended June 30, 2026 and 2025, the Company granted employees and non-employees stock options to purchase 497,541 and 130,091 shares of common stock, respectively, with a weighted-average grant date fair value of $1.89 and $11.20 per share, respectively. As of June 30, 2026 and 2025, total unrecognized compensation costs related to unvested employee stock options were $860 and $512, respectively. These costs are expected to be recognized over a weighted-average period of approximately 1.8 years and 2.0 years, respectively. The fair value of stock options vested was $0.1 million and $0.2 million for the three months ended June 30, 2026 and 2025, respectively, and $0.1 million and $1.5 million for the six months ended June 30, 2026 and 2025, respectively.

The Company estimated the fair value of stock options using the Black-Scholes option pricing valuation model. The fair value of employee and non-employee stock options is being amortized on the straight-line basis over the requisite service period of the awards. The fair value of employee and non-employee stock options was estimated using the following assumptions for the six months ended June 30, 2026 and 2025:

Expected Term—The expected term of options granted represents the period of time that the options are expected to be outstanding. Due to the lack of historical exercise history, the expected term of the Company’s employee stock options has been determined utilizing the simplified method for awards that qualify as plain-vanilla options.

Expected Volatility—The expected stock price volatility assumption was determined by examining the historical volatility of the Company's common stock and the historical volatilities of a group of industry peers. For grants made during the three

months ended March 31, 2026, the Company weighted its own historical volatility and peer volatility 25% and 75%, respectively. For grants made during the three months ended June 30, 2026, the Company weighted these inputs 50% and 50%, respectively. The Company will continue to analyze the historical stock price volatility and expected term assumption as more historical data for the Company’s common stock becomes available.

Risk-Free Interest Rate—The risk-free interest rate assumption is based on the U.S. Treasury instruments whose term was consistent with the expected term of the Company’s stock options.

Dividends—The Company has not paid any cash dividends on common stock since inception and does not anticipate paying any dividends in the foreseeable future. Consequently, an expected dividend yield of zero was used.

During the year ended December 31, 2025, the Company accelerated the vesting of approximately 266,108 time-based vesting stock options grants previously awarded to the Company's employees, pursuant to the separation agreements entered into with such employees. The Company also extended the post-termination exercise period from 90 days to 180 days immediately following the separation date for any options that were vested, including the options that were accelerated in vesting, as described above. Further, in the fourth quarter of 2025, approximately 416,005 of modified stock options were further modified to extend the post-termination exercise period from either (i) 180 days to December 31, 2026 or (ii) to the earlier of (a) the date that is 90 days following termination of continuous service, and (b) the expiration of the term of the options as set forth in the award agreements.

The above modifications to current and former employees stock options grants resulted in modification accounting under ASC 718, Compensation – Stock Compensation. As a result, the Company recognized approximately $0.1 million of stock compensation expense during the three months ended March 31, 2026 and $0.8 million of stock compensation expense during the year ended December 31, 2025. For vested awards with no future service period required to be provided, the expense was measured on the modification date by calculating the difference between the fair value of the modified award and the fair value of the original award immediately before it was modified with immediate expense recognition. For unvested awards with no future service period required to be provided, the Company reversed any stock compensation expense previously recognized, remeasured the fair value of the modified award and immediately recognized stock compensation expense on the modification date. For stock options that were further modified to extend the post-termination exercise period upon termination of continuous service, the Company measured the expense by calculating the difference between the fair value of the modified award and the fair value of the original award immediately before it was modified. The fair value of those awards included a reduction to the share price for the fair value of the warrant dividend as the holders of the modified stock options were not participants in the warrant dividend. For certain awards held by two of the Company's former executive officers that were deemed to be deeply out-of-the-money, the modification established a derived service period. A portion of the related incremental compensation cost was recorded as stock-based compensation expense in the fourth quarter of 2025, with the remainder initially attributed over the derived service period.

During the six months ended June 30, 2026, the Company's former President and Chief Executive Officer and former Chief Financial Officer separated from the Company. The former President and Chief Executive Officer stepped down from his executive position on February 3, 2026 but continued to provide service to the Company as a member of the Board of Directors until his resignation from the Board on May 22, 2026. The former Chief Financial Officer separated from the Company on June 5, 2026. Because the derived service period associated with their out-of-the-money modified awards was not completed as of their respective separation dates, the previously recognized incremental compensation cost related to those awards was reversed during the three months ended June 30, 2026, and no further incremental compensation cost will be recognized. The reversal totaled approximately $0.2 million and reduced stock-based compensation expense within general and administrative expense for the three and six months ended June 30, 2026.

Stock-Based Compensation Expense