The U.S. Food and Drug Administration (FDA) has granted approval to XOLREMDI™ (mavorixafor) capsules, developed by X4 Pharmaceuticals, for treating patients aged 12 and older with WHIM syndrome (warts, hypogammaglobulinemia, infections, and myelokathexis). This marks a significant advancement as XOLREMDI becomes the first therapy specifically indicated for this rare, combined primary immunodeficiency.
XOLREMDI is a selective CXC chemokine receptor 4 (CXCR4) antagonist designed to address the underlying cause of WHIM syndrome, which is the dysfunction of the CXCR4 pathway. WHIM syndrome is characterized by low blood levels of neutrophils (neutropenia) and lymphocytes (lymphopenia), leading to serious and frequent infections. It is estimated that at least 1,000 people are currently diagnosed with WHIM syndrome in the U.S.
Clinical Trial Results
The FDA's approval was primarily based on the results from the pivotal 4WHIM Phase 3 clinical trial. This global, randomized, double-blind, placebo-controlled study involved 31 participants aged 12 years and older with diagnosed WHIM syndrome. The study evaluated the efficacy and safety of XOLREMDI over a 52-week period.
Key findings from the 4WHIM trial include:
- Absolute Neutrophil Count (ANC): XOLREMDI treatment significantly increased the time above threshold (≥500 cells/microliter) for ANC compared to placebo (p<0.0001).
- Absolute Lymphocyte Count (ALC): Similarly, XOLREMDI increased the time above threshold (≥1000 cells/microliter) for ALC compared to placebo (p<0.0001).
- Infection Rate: Treatment with XOLREMDI resulted in a 60% reduction in the annualized infection rate compared to placebo-treated patients.
Analyses of a composite endpoint showed an approximate 40% reduction in total infection score, weighted by infection severity, in XOLREMDI-treated patients compared with placebo-treated patients.
Mechanism of Action
XOLREMDI (mavorixafor) works by antagonizing the CXCR4 receptor, which plays a crucial role in the movement of white blood cells between the bone marrow and peripheral circulation. By blocking the CXCR4 receptor, mavorixafor promotes the mobilization of neutrophils and lymphocytes from the bone marrow into the bloodstream, thereby increasing their levels and improving the body's ability to fight infections.
Safety and Adverse Reactions
The most common adverse reactions reported in the 4WHIM trial (≥10% and more frequently reported than placebo) were thrombocytopenia, pityriasis, rash, rhinitis, epistaxis, vomiting, and dizziness.
XOLREMDI carries warnings and precautions regarding embryo-fetal toxicity and QTc interval prolongation. It is contraindicated with drugs highly dependent on CYP2D6 for clearance. Caution is advised when co-administering with CYP3A4 inducers or inhibitors.
Supporting Patients
X4 Pharmaceuticals has launched X4Connect, a program offering support to eligible U.S. patients throughout their XOLREMDI treatment journey. This includes resources, insurance navigation assistance, and copay support. XOLREMDI will be commercially available in the U.S. through X4’s specialty pharmacy partner, PANTHERx® Rare.
"The approval of XOLREMDI is a transformational milestone both for X4 and, more importantly, for the WHIM syndrome community," said Paula Ragan, Ph.D., President and Chief Executive Officer of X4 Pharmaceuticals.
