• 12 November 2019
    X4 Pharmaceuticals Receives Breakthrough Therapy Designation from the FDA for Mavorixafor for the Treatment of WHIM Syndrome

    X4 Pharmaceuticals, Inc. (Nasdaq: XFOR), a clinical-stage biopharmaceutical company focused on the development of novel therapeutics for the treatment of rare diseases, today announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation for mavorixafor (X4P-001) for the treatment of adult patients with WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome, a rare, inherited, primary immunodeficiency disease caused by genetic mutations in the CXCR4 receptor gene.

    Mavorixafor is a potential first-in-class, once-daily, oral, small molecule antagonist of chemokine receptor CXCR4, and is currently being investigated in a pivotal Phase 3 global clinical trial, 4WHIM, for the treatment of WHIM syndrome. The Breakthrough Therapy Designation granted to mavorixafor is based on data from X4’s Phase 2 open-label, multi-center trial of mavorixafor in adult patients with WHIM syndrome. In this trial, proof of concept was established based on clinically meaningful increases in absolute neutrophil counts (ANCs), absolute lymphocyte counts (ALCs), evidence indicating reductions in infection rates and wart burden, and a safety profile showing that mavorixafor is well-tolerated.

    “Rare diseases such as WHIM don’t often receive the attention and research that patients and their families deserve. The FDA’s decision to grant Breakthrough Therapy Designation to mavorixafor for the treatment of adults with WHIM syndrome represents a significant milestone for patients and X4 alike, helping to further highlight the severity of this underdiagnosed disease and the importance of offering a potential novel, disease-modifying therapeutic option to this underserved patient population,” said Paula Ragan, Ph.D., President and Chief Executive Officer of X4 Pharmaceuticals. “We are excited to continue to advance our ongoing global Phase 3 pivotal trial and look forward to working closely with the FDA to bring this potential first-in-class treatment option to patients with WHIM syndrome as quickly as possible through this expedited regulatory pathway.”

    A Breakthrough Therapy Designation may be granted to expedite the development and regulatory review of an investigational new drug that is intended to treat a serious or life-threatening condition where there is an unmet need. The criteria for Breakthrough Therapy Designation require preliminary clinical evidence that demonstrates that the drug may provide substantial improvements over any available therapy on at least one clinically significant endpoint.

    Mavorixafor was granted orphan drug status by the FDA in 2018 and by the European Commission in 2019 for the treatment of WHIM syndrome. X4 is also developing the drug for the treatment of Severe Congenital Neutropenia (SCN), Waldenström’s macroglobulinemia (WM), and clear cell renal cell carcinoma (ccRCC).