Xenon Pharmaceuticals Inc.

Rule 10b5-1 Trading Plans

As previously disclosed, on December 3, 2025, certain of our officers adopted a Rule 10b5-1 trading arrangement intended to qualify as a “plan providing for eligible sell-to-cover transactions” under Rule 10b5-1(c)(1)(ii)(D)(3) under the Exchange Act (the “Sell-to-Cover Instructions”). On September 30, 2026, each of Ian Mortimer, the Company’s President and Chief Executive Officer, and Thomas P. Kelly, the Company’s Chief Financial Officer, modified their respective Sell-to-Cover Instructions to provide that, under certain circumstances, with respect to any vesting or settlement of restricted share units and performance share units within six months of September 30, 2026, the sell-to-cover instruction may be disregarded, and the executive will remit to the Company the amount of withholding tax incurred in connection with such vesting or settlement. The Sell-to-Cover Instructions otherwise remain unmodified in all respects.

Amended and Restated 2025 Inducement Plan

On November 9, 2026, we amended and restated our Amended and Restated 2025 Inducement Equity Incentive Plan (as amended and restated, the “2025 Inducement Plan”) to increase the maximum number of our common shares reserved for issuance under the 2025 Inducement Plan from 1,175,000 shares to 1,475,000 shares (subject to adjustments as provided in the 2025 Inducement Plan), to be used exclusively for grants of nonstatutory stock options, stock appreciation rights, restricted stock units, restricted stock, and performance awards as an inducement material to individuals being hired, or rehired following a bona fide period of interruption of employment, as an employee of Xenon or any of its subsidiaries. In accordance with Nasdaq Listing Rule 5635(c)(4), the Company did not seek approval of the 2025 Inducement Plan by its shareholders.

The foregoing is a brief description of the material terms of the 2025 Inducement Plan and is qualified in its entirety by reference to the full text of the 2025 Inducement Plan filed as Exhibit 10.1 to this report.

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