• 12 June 2020
    X4 Pharmaceuticals Presents Positive Clinical Data from Phase 2 Study of Mavorixafor in WHIM Syndrome at EHA 2020

    X4 Pharmaceuticals, Inc. (Nasdaq: XFOR), a leader in the discovery and development of novel therapies targeting diseases resulting from dysfunction of the CXCR4 pathway, today presented positive biomarker, efficacy, and safety data from its ongoing Phase 2 open-label extension trial of its lead candidate, mavorixafor, in patients with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome. The results included significant reductions in yearly infection rates and wart burden in WHIM patients treated for at least six months with mavorixafor. The data were presented in an e-poster at the 25th European Hematology Association (EHA) Annual Congress, taking place virtually from June 11-14, 2020.

    “We are extremely encouraged by the positive therapeutic profile of mavorixafor emerging from this study, including improvements in key biomarkers and clinical symptoms at the higher doses,” said Paula Ragan, Ph.D., President and Chief Executive Officer of X4 Pharmaceuticals. “These results suggest that mavorixafor is a promising, disease-modifying therapy that, by down-regulating CXCR4/CXCL12 signaling, could lead to improved and durable clinical efficacy in patients with WHIM syndrome. We view these data as a significant de-risking event for our ongoing and pivotal Phase 3 clinical trial, from which we expect top-line data in 2022. We look forward to continuing to advance the development of mavorixafor for patients with WHIM syndrome, a rare disease that we estimate could affect more than 3,500 people in the United States and that has no currently approved treatments.”

    The original Phase 2 clinical trial was an open-label, dose-escalation study that was followed by an open-label extension study to assess the safety, tolerability, dose-response, and clinical impact of mavorixafor in adult patients with genetically confirmed WHIM syndrome. The extension phase was open to patients who completed at least 24 weeks of the initial dose-escalation study and explored additional endpoints related to absolute neutrophil and lymphocyte counts, infection rates and wart burden, as well as long-term safety.

    Key Data Presented:

    • The Phase 2 trial results informed the design of the company’s ongoing global pivotal Phase 3 clinical trial (4WHIM) in:
      • The selection of the 400 mg once-daily dose; and
      • The choice of time above threshold for absolute neutrophil counts (TATANC), defined as the number of hours during which the absolute neutrophil count is raised above the 500 cells per microliter threshold (“time above threshold”), as the primary endpoint of the trial.
    • Sustained, dose-dependent increases in WBC (white blood cells), ANC (absolute neutrophil count), and ALC (absolute lymphocyte count) were achieved; higher doses of mavorixafor were shown to increase the TATANC at least 4.5-fold versus the TATANC at lower doses.
    • These long-term hematological improvements correlated with fewer infections and reduced numbers of cutaneous warts, two secondary clinical endpoints in the 4WHIM trial:
      • A decreased yearly infection rate from 4.63 [95%CI 3.3,6.3] events in the 12 months prior to the trial, to 2.27 [95%CI 1.4, 3.5] events when treated with mavorixafor at higher doses once daily; notably, deeper reductions in yearly infection rates correlated with increased time on treatment.
      • The patients with cutaneous warts on hands and/or feet at baseline achieved an average 75% reduction in the number of warts.
    • Mavorixafor was well-tolerated for the extended duration of up to more than two years without any attributable serious adverse effects.