X4 Pharmaceuticals, Inc

15. Warrants

In connection with the sale of shares of its common stock, the Company has from time to time issued warrants and pre-funded warrants, which are exercisable for the purchase shares of the Company’s common stock. All outstanding warrants and pre-funded warrants are currently exercisable and do not have price reset provisions. Upon the closing of these public and private offerings, the Company received approximately 99% of the exercise price for the pre-funded warrants, for which the remaining exercise price is equal to or less than$0.03 per share.

The following table rolls forward outstanding warrants for the three years ended December 31, 2025.

(1) Excludes pre-funded warrants, for which the remaining exercise price is between $0.001 and $0.03 per share.

During the year ended December 31, 2025, the Company issued 15,241,246 common shares upon the exercise of 15,255,271 pre-funded warrants pursuant to a net exercise mechanism under the warrants.

As of December 31, 2025, the Company’s outstanding warrants and pre-funded warrants to purchase shares of common stock consisted of the following:

16. Stock-Based Compensation

Summary of Plans—The Company issues stock awards under the following plans: (a) the Amended and Restated 2017 Equity Incentive Plan (the “2017 Plan”), (b) the Amended and Restated 2017 Employee Stock Purchase Plan (the “2017 ESPP”) and (c) the 2019 Inducement Equity Incentive Plan (the “2019 Plan”).

These plans are administered by the Board of Directors or by a committee thereof. The exercise prices, vesting and other restrictions are determined at the discretion of the Board of Directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of the stock option may not be greater thanten years. Incentive stock options granted to employees and restricted stock awards granted to employees, officers, members of the Board of Directors, advisors, and consultants of the Company typically vest over four years. Non-statutory options granted to employees, officers, members of the Board of Directors, advisors, and consultants of the Company typically vest over three orfour years. Shares of common stock, if any, issued upon the exercise of stock options and vesting of restricted stock units are issued as new shares of common stock from the share pool reserves established for the applicable plan. Shares that are expired, terminated, surrendered or canceled under the Plans without having been fully exercised will be available for future awards. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards.

2017 Equity Incentive Plan—Under the 2017 Plan, the Company may grant incentive stock options, non-qualified options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. Under an “evergreen” provision of the 2017 Plan, shares of common stock reserved for issuance under the 2017 Plan are increased annually on January 1, 2026 and on January 1, 2027, in an amount equal to the lower of 4.0% of the number of shares of the Company’s common stock outstanding on January 1 of each year or a lower amount determined by the Company’s Board of Directors. As of December 31, 2025,0.1 million shares were available for future issuance under the 2017 Plan. As of January 1, 2026, an additional 3.6 million shares became available for future issuance under the 2017 Plan under the evergreen provision.

Amended and Restated 2017 Employee Stock Purchase Plan—The 2017 ESPP provides participating employees with the opportunity to purchase shares of the Company’s common stock at defined purchase prices over six-month offering periods. For the year ended December 31, 2025,38,769 shares of common stock were issued under the 2017 ESPP. As of December 31, 2025, approximately 103,102 shares were available for future issuance under the 2017 ESPP.

2019 Inducement Equity Incentive Plan—The 2019 Plan, as amended, is used exclusively for the grant of equity awards to individuals who were not previously employees of the Company, as an inducement material to such individual’s entering into employment with the Company. Shares that are expired, forfeited, canceled or otherwise terminated without having been fully exercised become available for future grant under the 2019 Plan. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for future grants. As of December 31, 2025,1.0 million shares were available for future issuance under the 2019 Plan.

Stock Option Valuation

The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted:

Stock Options

The following table summarizes the Company’s stock option activity for the year ended December 31, 2025:

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 to the extent the stock option had a lower exercise price. There were no options exercised in 2025 and 2024. The weighted average grant-date fair value per share of stock options granted during the years ended December 31, 2025, 2024 and 2023 was $1.35, $22.20, and $29.10 respectively.

Restricted Stock Units

The following table summarizes the Company’s restricted stock unit activity for the year ended December 31, 2025:

The weighted average grant-date fair value per share of restricted stock units granted during the years ended December 31, 2025, 2024 and 2023 was $12.65, $28.50, and $52.80, respectively.

During the year ended December 31, 2025, the Company granted 0.3 million time-based restricted stock units to employees at the grant date fair value of $12.65 per share. These awards vest as the employee provides services to the Company over athree-year vesting period. Also during the year ended December 31, 2025,0.1 million outstanding performance-based restricted stock units (“PRSUs”) vested based on the achievement of an operational milestone. The Company considers the achievement of the remaining operational milestone related to outstanding PRSUs to be probable. Stock-based compensation expense has been recognized for these awards using the accelerated attribution model based on the fair value of the awards as of the date of grant and management’s best estimate of the date the probable operational milestone will be achieved. The Company updates its estimates related to the probability and timing of achievement of the operational milestones each period until the award either vests or is forfeited.

During the year ended December 31, 2025, in connection with the termination of employment for three former executives, the vesting of 0.1 million restricted stock units was accelerated resulting in $0.3 million of incremental stock-based compensation expense within general and administrative expense.

Stock-Based Compensation

Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows:

As of December 31, 2025, total unrecognized compensation expense related to unvested stock options and restricted stock units was $11.7 million, which is expected to be recognized over a weighted average period of 2.4 years.

Stock Appreciation Rights

The following table rolls forward the Company’s stock appreciation right (“SARs”) balances and activity as of December 31, 2025. All SARs have been forfeited due to participant terminations as of December 31, 2025.