SecProbe.io

August 14, 2019
Paula Ragan
Chief Executive Officer
X4 Pharmaceuticals, Inc.
955 Massachusetts Avenue, 4th Floor
Cambridge, MA 02139
Re:X4 Pharmaceuticals, Inc.
Registration Statement on Form S-3
Filed August 9, 2019
File No. 333-233161
Dear Dr. Ragan:
            We have limited our review of your registration statement to those issues we have
addressed in our comments.  In some of our comments, we may ask you to provide us with
information so we may better understand your disclosure.
            Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
            After reviewing any amendment to your registration statement and the information you
provide in response to these comments, we may have additional comments.
Registration Statement on Form S-3
Description of Capital Stock
Anti-Takeover Provisions
Exclusive Forum Selection, page 15
1.We note that your forum selection provision identifies the Court of Chancery of the State
of Delaware as the exclusive forum for certain litigation, including any “derivative
action.” Please disclose whether this provision applies to actions arising under the
Securities Act or Exchange Act. In that regard, we note that Section 27 of the Exchange
Act creates exclusive federal jurisdiction over all suits brought to enforce any duty or
liability created by the Exchange Act or the rules and regulations thereunder, and Section
22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all
suits brought to enforce any duty or liability created by the Securities Act or the rules and

 FirstName LastNamePaula Ragan
 Comapany NameX4 Pharmaceuticals, Inc.
 August 14, 2019 Page 2
 FirstName LastName
Paula Ragan
X4 Pharmaceuticals, Inc.
August 14, 2019
Page 2
regulations thereunder. If the provision applies to Securities Act claims, please also revise
your prospectus to state that there is uncertainty as to whether a court would enforce such
provision and that investors cannot waive compliance with the federal securities laws and
the rules and regulations thereunder.  If this provision does not apply to actions arising
under the Securities Act or Exchange Act, please also tell us how you will inform
investors in future filings that the provision does not apply to any actions arising under the
Securities Act or Exchange Act.
            We remind you that the company and its management are responsible for the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action or absence of
action by the staff.
            Refer to Rules 460 and 461 regarding requests for acceleration.  Please allow adequate
time for us to review any amendment prior to the requested effective date of the registration
statement.
            Please contact Sonia Bednarowski at 202-551-3666 or Justin Dobbie, Legal Branch
Chief, at 202-551-3469 with any questions.
Sincerely,
Division of Corporation Finance
Office of Healthcare & Insurance