Sanofi's rare disease drug Xenpozyme scores FDA approval after nods in Japan and Europe

On a campaign to develop first-in-class and best-in-class medicines, Sanofi has gained an FDA nod for its latest rare disease drug.

In March, regulators in Japan signed off on Xenpozyme to treat Niemann-Pick, a rare genetic disease that prevents the body from metabolizing fat and leads to premature death. Officials in Europe did the same two months later.

Now, the intravenously infused treatment will be available to children and adults in the U.S. It is the first drug approved for the non-central nervous system (non-CNS) manifestations of the condition, also known as acid sphingomyelinase deficiency (ASMD), said the FDA.

There are fewer than 120 people diagnosed with ASMD in the U.S., Sanofi said, with roughly two-thirds of patients being children. The condition is caused by a lack of an enzyme needed to break down a complex lipid, called sphingomyelin, which collects in the liver, spleen, lung and brain.

Symptoms of the progressive disease can present at any age from infancy to adulthood. Infants with the most severe and early symptoms rarely live beyond three years. Others can survive into adulthood but often die from respiratory failure.

Xenpozyme is a hydraulic lysomal enzyme replacement therapy that reduces the accumulation of sphingomyelin. The drug is not expected to cross the blood-brain barrier or modulate CNS manifestations of ASMD, Sanofi said, and it has not been studied in patients with that (type A) form of the disease.

The drug proved its value in a randomized, placebo-controlled study of 31 patients, which showed it reduced the size of the spleen and liver and improved lung function.

Xenpozyme is administered every two weeks. Sanofi expects to make it available in the coming weeks at a U.S. list price of $7,142 per vial, the company said.

Xenpozyme received fast-trackbreakthrough-therapy, and priority-review designations. It also received orphan-drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases. The FDA approval came in well ahead of its Oct. 3 target date, which was previously extended by three months.

While the approval marks a win for Sanofi in its efforts to advance new innovative medicines, Xenpozyme is unlikely to become a major commercial success. Back in 2020, analysts with ODDO BHF predicted the drug would generate just $40 million in 2024. 

For their part, Jefferies analysts last year assigned a $500 million peak sales target to the drug, but they said there was a 50% chance the drug could reach that mark.