US FDA approves X4 Pharmaceuticals' therapy for immunodeficiency disease

By Christy Santhosh

(Reuters) -X4 Pharmaceuticals said on Monday the U.S. FDA has approved its therapy to treat a rare genetic immunodeficiency disease in patients 12 years of age and older.

X4's mavorixafor, to be sold under the brand name Xolremdi, is the first therapy to get U.S. approval specifically for the treatment of WHIM syndrome.

WHIM is characterized by disorders in which the body's immune system does not function properly. It is an acronym for warts, hypogammaglobulinemia or low antibody levels, infections, and myelokathexis or low white blood cell count, which are all symptoms of the disorder.

The company has set a wholesale acquisition cost for Xolremdi on an annual basis at $496,400 for patients greater than 50 kilograms and $372,300 for patients less than or equal to 50 kilograms.

The approval is based on a late-stage study where the therapy showed 60% reduction in infection rate compared to placebo when tested in patients with WHIM syndrome.

Xolremdi works by targeting the body's CXCR4 gene, which facilitates the mobilization of white blood cells from the bone marrow into the blood, improving immune system function.

The therapy is also being evaluated for other indications, including certain chronic disorders where the body has low levels of a type of white blood cell called neutrophils.

Brookline Capital Markets analyst Leah Cann 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.

With the approval, X4 has received a rare pediatric disease priority review voucher, which allows a drug developer to expedite the review process of its product even if it does not fit requirements for a quick process.

Less than 1,000 people in the United States have WHIM syndrome, according to government data.

Shares of the company were up 2% in premarket trading.

(Reporting by Christy Santhosh in Bengaluru; Editing by Shinjini Ganguli and Shilpi Majumdar)