RARE Daily

FDA Grants X4 Pharmaceuticals Fast Track Designation for WHIM Therapy

October 8, 2020

Rare Daily Staff

The U.S. Food and Drug Administration granted X4 Pharmaceuticals Fast Track designation for mavorixafor for the treatment of adult patients with the rare genetic syndrome WHIM.

WHIM syndrome is a rare, primary immunodeficiency disease caused by genetic mutations in the CXCR4 receptor gene. It is named for the characteristic clinical symptoms of the syndrome – Warts, Hypogammaglobulinemia, Infections, and Myelokathexis. Patients with WHIM may experience significant morbidity beginning in early childhood and continuing throughout life with an increased likelihood of various recurrent, potentially life-threatening infections, and may also be susceptible to malignancies such as HPV-related cervical cancer and lymphomas. The overall cancer risk in patients with WHIM is estimated to be 30 percent by 40 years of age. There are no approved therapies for WHIM. Although the exact prevalence of WHIM is unknown, in the United States there are between 15,000 and 100,000 patients classified as having a primary immunodeficiency disease of unknown origin – of which WHIM is one.

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 for the treatment of WHIM syndrome. Results are expected in 2022.

Fast Track designation is designed to facilitate the development and expedite the review of drugs to treat serious conditions and fulfill an unmet medical need, enabling drugs to reach patients earlier. Clinical programs with Fast Track designation may benefit from early and frequent communication with the FDA throughout the regulatory review process.

These clinical programs may also be eligible to apply for Accelerated Approval and Priority Review if relevant criteria are met, as well as Rolling Review, which means that completed sections of the Biologic License Application can be submitted for review before the entire FDA application is complete.  Mavorixafor was previously granted Breakthrough Therapy designation by the FDA and Orphan Drug status by the FDA and the European Commission for the treatment of WHIM syndrome.

“The Fast Track Designation of mavorixafor for the treatment of WHIM syndrome further recognizes WHIM as a serious condition with a clear unmet need for an effective and potentially disease-modifying therapy,” said Paula Ragan, president and CEO of X4 Pharmaceuticals. “We recently showed the potential therapeutic benefit of mavorixafor in a phase 2 clinical trial in WHIM, with significant increases in white blood cell counts and reductions in infection rates and wart burden. We look forward to continuing to demonstrate mavorixafor’s clinical utility in WHIM syndrome in our ongoing phase 3 clinical trial and working with the FDA to potentially bring this promising therapy to patients as soon as possible.”

Photo: Paula Ragan, president and CEO of X4 Pharmaceuticals

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