X4 Pharmaceuticals (NASDAQ: XFOR) announced the European Commission has granted marketing authorization for XOLREMDI (mavorixafor) capsules to treat patients with WHIM syndrome in the European Union.

The approval marks the first authorized treatment for WHIM syndrome in the EU. The marketing authorization was granted under exceptional circumstances, reflecting the ultra-rare nature of the condition.

XOLREMDI is a CXC chemokine receptor 4 (CXCR4) antagonist authorized for patients 12 years and older with WHIM syndrome. The oral, once-daily therapy increases the number of circulating mature neutrophils and lymphocytes.

WHIM syndrome is an inherited combined primary immunodeficiency and chronic neutropenic disorder characterized by warts, hypogammaglobulinemia, infections, and myelokathexis. The condition results from CXCR4 receptor dysfunction that impairs mobilization of white blood cells from bone marrow into peripheral circulation.

The approval is based on results from the pivotal Phase 3 4WHIM trial, a 52-week multicenter study that evaluated mavorixafor in 31 people aged 12 years and older diagnosed with WHIM syndrome.

European commercialization will be led by X4's partner Norgine under a licensing and supply agreement signed in January 2025. X4 could receive up to €226 million contingent on regulatory and commercial milestones, plus escalating double-digit royalties up to the mid-twenties on net sales in licensed territories including Europe, Australia and New Zealand.

X4 is currently conducting a global Phase 3 clinical trial called 4WARD evaluating mavorixafor in chronic neutropenia. The company has received Fast Track designation from the FDA for mavorixafor in chronic neutropenia treatment.