FDA approves mavorixafor as first drug for WHIM syndrome

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The rare genetic disease causes the body's immune system to not function properly.

FDA approves mavorixafor as first drug for WHIM syndrome | Image Credit: © Calin - © Calin - stock.adobe.com.

FDA approves mavorixafor as first drug for WHIM syndrome | Image Credit: © Calin - © Calin - stock.adobe.com.

The FDA has approved mavorixafor (Xolremdi; X4 Pharmaceuticals) capsules for patients aged 12 years and older with WHIM syndrome ((warts, hypogammaglobulinemia, infections and myelokathexis).1,2

The drug aims to increase the number of circulating mature neutrophils and lymphocytes. The elective CXC chemokine receptor 4 (CSCR4) antagonist is the first therapy "specifically indicated" in patients with WHIM syndrome, according to X4 Pharmaceuticals.2

The New Drug Application (NDA) for mavorixafor was evaluated under Priority Review by the FDA and was also granted Breakthrough Therapy Designation.2

"Until now, supportive care for people with WHIM syndrome has focused on symptom management and not the underlying cause of disease — the dysfunction of the CXCR4 pathway," said Teresa K. Tarrant, MD, professor of Medicine, Rheumatology, and Immunology, Duke University School of Medicine, in a statement.2

"I am thrilled that with the approval of [mavorixafor], a therapy designed to address dysregulated CXCR4 pathway signaling, we now have a targeted treatment that has demonstrated the ability to elevate absolute neutrophil and lymphocyte counts, increasing WHIM patients’ ability to fight infections," added Tarrant.

The genetic disease reduces the number of mature neutrophils and lymphocytes (white blood cells important in fighting infection) that circulate in the body, stated the FDA. The federal agency added WHIM syndrome is estimated to occur in approximately 1 in 5 million live births, with approximately 60 cases reported in the medical literature.1

WHIM syndrome patients can have recurrent infections such as pneumonia, sinusitis, and skin infections. These patients are also at risk for life-threatening bacterial and viral infections, along with other varying symptoms.1

Efficacy of mavorixafor was assessed in a 52-week randomized, double-blind, placebo-controlled trial (NCT03995108) that included 31 adults and adolescents with WHIM syndrome. The newly-approved drug "improved absolute neutrophil counts and absolute lymphocyte counts, assessed over a 24-hour period four times throughout the study," stated the FDA.1

Absolute neutrophil counts below 500 cells / µL and absolute lymphocyte counts below 1000 cells / µL are associated with an increased risk of infections. Compared to the placebo group, the average length of time over 24 hours that counts were above these levels were "significantly longer" with mavorixafor (15.0 hours compared to 2.8 hours for absolute neutrophil counts; 15.8 hours compared to 4.6 hours for absolute lymphocyte counts).1

The FDA added mavorixafor decreased infection score by 40% over the 52-week period, but did not improve warts.1

Thrombocytopenia (low platelet counts), rash, rhinitis (stuffy nose), epistaxis (nosebleed), vomiting, and dizziness were the most commonly reported adverse reactions. The FDA also warned that mavorixafor can cause fetal harm, and that potentially childbearing persons "should be advised to use effective contraception."

References:

1. FDA approves first drug for WHIM syndrome, a rare disorder that can lead to recurrent, life-threatening infections. FDA. Press release. April 29, 2024. Accessed April 29, 2024. https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-first-drug-whim-syndrome-rare-disorder-can-lead-recurrent-life-threatening-infections?utm_medium=email&utm_source=govdelivery

2. X4 Pharmaceuticals Announces FDA Approval of XOLREMDI™ (mavorixafor) Capsules, First Drug Indicated in Patients with WHIM Syndrome. X4 Pharmaceuticals. Press release. April 29, 2024. Accessed April 29, 2024. https://investors.x4pharma.com/news-releases/news-release-details/x4-pharmaceuticals-announces-fda-approval-xolremditm-mavorixafor

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