X4 Pharmaceuticals, Inc.

61 North Beacon Street, 4th Floor

Boston, MA 02134

June 16, 2023

Via Edgar

United States Securities and Exchange Commission

Division of Corporation Finance

100 F Street, N.E.

Washington, D.C. 20549

Attn:    Jimmy McNamara

RE:    X4 Pharmaceuticals, Inc.

    Registration Statement on Form S-3

    File No. 333-272551

    Acceleration Request

        Requested Date:    June 20, 2023

        Requested Time:    4:00 p.m. Eastern Time

Ladies and Gentlemen:

Pursuant to Rule 461 under the Securities Exchange Act of 1933, as amended, the undersigned registrant hereby requests that the Securities and Exchange Commission take appropriate action to cause the above-referenced Registration Statement on Form S-3 (File No. 333-272551) (the “Registration Statement”) to become effective at 4:00 p.m. Eastern Time on Tuesday, June 20, 2023, or as soon thereafter as is practicable.

Once the Registration Statement has been declared effective, please orally confirm that event with Daniel I. Goldberg of Cooley LLP, counsel to the registrant, at (212) 479-6722.

[Signature page follows]

Sincerely,

X4 Pharmaceuticals, Inc.

By:     /s/ Adam S. Mostafa        

    Adam S. Mostafa

Chief Financial Officer

cc:    Paula Ragan, Ph.D., Chief Executive Officer, X4 Pharmaceuticals, Inc.    

    Daniel I. Goldberg, Cooley LLP

Eric Blanchard, Cooley LLP

Courtney T. Thorne, Cooley LLP