X4 Pharmaceuticals Submits NDA of Mavorixafor for Rare Immunodeficiency Disease

X4 Pharmaceuticals has submitted a new drug application to the FDA for the approval of mavorixafor to treat patients 12 years and older with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome.

WHIM is an extremely rare immunodeficiency disease caused by reduced mobilization of white blood cells from the bone marrow due to over-signaling of the CXCR4/CXCL12 pathway. People with WHIM syndrome characteristically have very low blood levels of neutrophils and lymphocytes. Its exact prevalence or incidence in the general population is unknown. About 60 cases have been reported in the medical literature, accordingto the Immune Deficiency Foundation.

Symptoms can vary but patients often experience recurrent infections with a high risk of lung disease, refractory warts from underlying human papillomavirus (HPV) infection, and an increased risk of developing certain types of cancer. Current treatment involves intravenous immunoglobulin or granulocyte colony-stimulating factor (G-CSF), an immune-cell-growth molecule. These treatments, however, do not specifically target the CXCR4 genetic defect,

Mavorixafor is an investigational small-molecule antagonist of CXCR4 being developed as a once-daily oral therapy.

“The submission of our first NDA is a significant milestone in X4’s journey to transform the care of those living with rare immunodeficiencies,” Paula Ragan, Ph.D., president and CEO of X4 Pharmaceuticals, said in a press release. “We’re excited that this submission moves us one step closer to introducing what could be the first approved product in the United States for those with WHIM syndrome.”

The NDA is supported by the pivotal 4WHIM phase 3 clinical trial, which met its primary end point and key secondary end point. In the trial, mavorixafor treatment resulted in reductions in the rate, severity, and duration of infections in trial participants versus placebo. Mavorixafor was generally well tolerated, with no treatment-related serious adverse events reported and no discontinuations for safety events.

In May 2023, the company announced results of this trial, which showed that mavorixafor treatment results in about a 60% reduction in annualized infection rate, a greater than 75% reduction in the percentage of patients experiencing severe infections and a greater than 70% reduction in mean total days with infections.

These and additional 4WHIM phase 3 data were published in oral presentations at the annual meetings of both the Clinical Immunology Society and European Hematology Association.

X4 Pharmaceuticals continues research of mavorixafor in chronic neutropenic disorders, and is enrolling a phase 2 trial for people with idiopathic, cyclic, and congenital chronic neutropenia. A phase 3 trial is expected to begin in the first half of 2024 in certain chronic neutropenic disorders.