X4 Pharmaceuticals Prices $85.8 Million Public Offering of Common Stock and Class A Warrants

CAMBRIDGE, Mass.–(BUSINESS WIRE)–X4 Pharmaceuticals, Inc. (Nasdaq: XFOR), a clinical-stage
biopharmaceutical company focused on the development of novel
therapeutics for the treatment of rare diseases, announced today the
pricing of its previously announced underwritten public offering of
5,670,000 shares of its common stock and, in lieu of common stock,
pre-funded warrants to purchase 2,130,000 shares of common stock, and
accompanying Class A warrants to purchase 3,900,000 shares of its common
stock at a price to the public of $11.00 per share and accompanying
Class A warrant (or $10.999 per pre-funded warrant and accompanying
Class A warrant). X4’s gross proceeds from this offering are expected to
be approximately $85.8 million, before deducting underwriting discounts
and estimated offering expenses. All of the securities in the offering
are being sold by X4. The offering is expected to close on or about
April 16, 2019, subject to customary closing conditions.

Cowen and Stifel are acting as joint book-running managers and
representatives of the underwriters for the offering. Canaccord Genuity
is acting as lead manager of the offering.

The offering is being made only by means of a written prospectus and
related prospectus supplement forming part of a shelf registration
statement on Form S-3 that was filed with the Securities and Exchange
Commission (SEC) on January 25, 2019 and declared effective by the SEC
on February 19, 2019. The preliminary prospectus supplement and
accompanying prospectus relating to and describing the terms of the
offering were filed with the SEC on April 12, 2019. The final prospectus
supplement and accompanying prospectus will be filed with the SEC and
will be available at the SEC’s website located at www.sec.gov,
copies of which may be obtained, when available, from Cowen and Company,
LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue,
Edgewood, NY 11717, Attn: Prospectus Department, or by telephone at
631-274-2806, and from Stifel, Nicolaus & Company, Incorporated,
Attention: Syndicate, One Montgomery Street, Suite 3700, San Francisco,
California 94104, or by telephone at 415-364-2720 or by email at [email protected].

This press release shall not constitute an offer to sell or a
solicitation of an offer to buy, nor shall there be any sale of these
securities in any state or other jurisdiction in which such an offer,
solicitation or sale would be unlawful prior to registration or
qualification under the securities laws of any such state or other
jurisdiction.

About X4 Pharmaceuticals

X4 Pharmaceuticals is developing novel therapeutics designed to improve
immune cell trafficking to treat rare diseases, including primary
immunodeficiencies and cancer. X4’s oral small molecule drug candidates
antagonize the CXCR4 pathway, which plays a central role in immune
surveillance. X4’s most advanced product candidate, mavorixafor
(X4P-001), will be commencing a global Phase 3 pivotal trial in patients
with WHIM syndrome, a rare genetic, primary immunodeficiency disease, in
the second quarter of 2019 and is currently also under investigation in
a Phase 2a clinical trial in clear cell renal cell carcinoma. X4 was
founded and is led by a team with extensive product development and
commercialization expertise, including several former members of the
Genzyme leadership team, and is located in Cambridge, Massachusetts.

Forward-Looking Statements

This press release contains forward-looking statements within the
meaning of the Private Securities Litigation Reform Act of 1995, as
amended. The words “may,” “will,” “could,” “would,” “should,” “expect,”
“plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,”
“project,” “potential,” “continue,” “target” and similar expressions are
intended to identify forward-looking statements, although not all
forward-looking statements contain these identifying words.
Forward-looking statements include statements regarding the completion
of the proposed public offering. These statements are subject to various
risks and uncertainties, actual results could differ materially from
those projected and X4 cautions investors not to place undue reliance on
the forward-looking statements in this press release. These risks and
uncertainties include, without limitation, risks and uncertainties
related to market conditions and satisfaction of customary closing
conditions related to the public offering. There can be no assurance
that X4 will be able to complete the public offering on the anticipated
terms and on the anticipated closing date, or at all. Any
forward-looking statements in this press release are based on
management’s current expectations and beliefs and are subject to a
number of risks, uncertainties and important factors that may cause
actual events or results to differ materially from those expressed or
implied by any forward-looking statements contained in this press
release, including, without limitation, the risks and uncertainties
described in the section entitled “Risk Factors” in X4’s preliminary
prospectus supplement related to the proposed offering filed with the
SEC on April 12, 2019, X4’s most recent Annual Report on Form 10-K filed
with the SEC, as updated by X4’s Current Report on Form 8-K filed with
the SEC on April 11, 2019, and in other filings X4 makes with the SEC
from time to time. X4 undertakes no obligation to update the information
contained in this press release to reflect subsequently occurring events
or circumstances.

Contacts

Investors:
Stephanie Carrington
Westwicke, an ICR
company
646-277-1282
[email protected]

Media:
Darcie
Robinson
Westwicke, an ICR company
203-919-7905
[email protected]