X4 Pharmaceutical’s Immunodeficiency Disease Therapy gets FDA Approval

X4 Pharmaceuticals announced on Monday, April 29, 2024, that it has received FDA approval in the United States to treat a rare genetic immunodeficiency disease in patients 12 years and older using its mavorixafor. The therapy will be sold under the brand name Xolremdi.

Xolremdi is the first therapy to be approved in the United States for the treatment of Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM syndrome). This rare genetic disease affects the immune system. Its name is an acronym for all the main clinical manifestations of the disease.

The company has set the wholesale acquisition cost for Xolremdi at $496,400 annually for patients above 50 kilograms and $372,300 for patients under or equal to 50 kilograms. The approval of the therapy was based on the outcome of a late-stage study where it achieved a 60% reduction in infection rate compared to a placebo when tested in patients with WHIM syndrome. 

How Xolremdi work

Xolremdi works by targeting the CXCR4 gene in the body which is responsible for facilitating the mobilization of white blood cells from the bone marrow into the blood, thereby improving immune system function. 

The company is also evaluating the effectiveness of the therapy for other conditions, including chronic disorders where the body has very low levels of neutrophils—a type of white blood cell. Leah Cann, an analyst for Brookline Capital Markets said, “An approval to treat WHIM could lead to 2024 sales of $54.6 million for the therapy, and with a second indication in 2025, product sales could grow to $450.9 million in 2027”. 

The approval of Xolremdi also came with a rare pediatric disease priority voucher. The voucher allows the drugmaker to expedite the review process of its product even if it does not fit the requirements for a quick process. According to government data, WHIM syndrome affects less than 1,000 people in the United States.