SCHEDULE 13G 0001964437 XXXXXXXX LIVE Common Stock 10/24/2025 0001501697 X4 Pharmaceuticals, Inc. 98420X202 61 North Beacon Street 4th Floor Boston MA 02134 Rule 13d-1(b) Saturn V Capital Management LP DE 0.00 6433481.00 0.00 6433481.00 6433481.00 N 7.36 IA * Saturn V Capital Management LP acts as the investment manager of certain pooled investment vehicles and managed accounts (collectively the "Clients") in which such shares referred to above are held. As a result, Saturn V Capital Management LP possesses the power to vote and dispose or direct the disposition of all the shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding shares of the Issuer. Saturn V Capital Management LP disclaims beneficial ownership of any of the shares held by the Clients. + Based on 87,436,688 shares outstanding of the Issuer as of October 31, 2025, as set forth in the Issuer's Form 10-Q, filed November 5, 2025. Xiaoying Tian X1 0.00 6433481.00 0.00 6433481.00 6433481.00 N 7.36 IN * Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn V Capital Management LP, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the shares held by the Clients. + Based on 87,436,688 shares outstanding of the Issuer as of October 31, 2025, as set forth in the Issuer's Form 10-Q, filed November 5, 2025. X4 Pharmaceuticals, Inc. 61 North Beacon Street, 4th Floor, Boston, MA 02134 Saturn V Capital Management LP, Xiaoying Tian 919 Congress Avenue, Suite 830, Austin, TX 78701 Saturn V Capital Management LP is a Delaware Limited Partnership. Xiaoying Tian is a citizen of the United States. N HC Aggregate of all Reporting Persons: 6,433,481 Saturn V Capital Management LP - 6,433,481* Xiaoying Tian - 6,433,481** * Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients. ** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients. Aggregate of all Reporting Persons: 7.36%+ Saturn V Capital Management LP - 7.36%+* Xiaoying Tian - 7.36%+** * Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients. ** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients. + Based on 87,436,688 shares outstanding of the Issuer as of October 31, 2025, as set forth in the Issuer's Form 10-Q, filed November 5, 2025. Saturn V Capital Management LP - 0 Xiaoying Tian - 0 Saturn V Capital Management LP - 6,433,481* Xiaoying Tian - 6,433,481** * Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients. ** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients. Saturn V Capital Management LP - 0 Xiaoying Tian - 0 Saturn V Capital Management LP - 6,433,481* Xiaoying Tian - 6,433,481** * Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients. ** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients. Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Saturn V Capital Management LP Xiaoying Tian 02/12/2026 Xiaoying Tian Xiaoying Tian 02/12/2026