Biotechnology Value Fund's Ownership in X4 Pharmaceuticals, Inc.

The filing discloses the ownership of common stock in X4 Pharmaceuticals, Inc. by Biotechnology Value Fund, L.P. and related entities. As of August 20, 2025, BVF beneficially owned approximately 5.2% of the outstanding shares, BVF2 owned approximately 4.0%, and Trading Fund OS owned less than 1%. BVF GP, BVF2 GP, Partners OS, BVF GPH, Partners, BVF Inc., and Mark N. Lampert may be deemed to beneficially own varying percentages of the outstanding shares, with Mr. Lampert potentially owning approximately 9.99%. The filing also details the ownership structure and the limitations on the exercise of Pre-Funded Warrants held by the Reporting Persons.