Sanofi’s Rare Disease Drug Granted First-Ever FDA Approval for the Condition

After snagging approvals in Japan and Europe this year, Sanofi announced that its rare disease drug, Xenpozyme, received another big approval from the FDA to treat adult and pediatric patients with non-central nervous system manifestations of acid sphingomyelinase deficiency (ASMD). The intravenous infused drug is the US’s first and only specialized treatment for ASMD. 

Innovating Treatment for a Rare and Debilitating Disease

Affecting only approximately 120 Americans, ASMD, informally known as Niemann-Pick, is an incredibly rare disease affecting primarily infants. ASMD is characterized by the body’s inability to metabolize a fatty substance called sphingomyelin, which can build up in organs like the liver, lungs, and spleen. Excessive buildup can inhibit organ function, eventually leading to organ failure. 

Sanofi designed Xenpozyme as a hydrolytic lysosomal sphingomyelin-specific enzyme replacement therapy to replace defective acid sphingomyelinase, the enzyme responsible for breaking down sphingomyelin. There are three types of ASMD; A, A/B, and B, the last of which is the most common. Sanofi said it did not study Xenpozyme in patients with type A ASMD, which is the most severe and rapidly progressive. 

Xenpozyme saw a speedy development pathway after receiving fast track, breakthrough therapy designations, and priority review. The drug also received orphan drug designation early on, which involves tax credits, exemption from user fees, and the potential for seven-year market exclusivity upon approval.

Sanofi expects to market the drug for a list price or wholesale acquisition cost of $7,142 per vial. The price does not take insurance coverage or financial assistance into account. Still, with the small market, Sanofi likely does not expect the drug to be a blockbuster. 

Executive Vice President, Head, Specialty Care at Sanofi, Bill Sibold, said, “Sanofi teams have been dedicated to bringing hope to patients living with ASMD and their families. This is a devastating and extremely rare disease that affects both children and adults. The approval of Xenpozyme represents the culmination of bold work done in research and development, and our unwavering commitment to this historically overlooked community.”

Related Article: Sanofi’s Treatment for Hemophilia A has a Concrete FDA Decision Date

Adult and Pediatric Trials Supporting the FDA’s Decision

The FDA approved Xenpozyme based on two clinical trials, the ASCEND trial involving 31 adult ASMD patients and the ASCEND-Peds trial involving eight pediatric patients younger than 12. Based on the positive results, the FDA approved Xenopozyme to Genzyme, a wholly-owned subsidiary of Sanofi since 2011. 

The ASCEND trial assessed the percent change in predicting the diffusing capacity of the lung for carbon monoxide (DLco) and the percent change of reduced spleen volume. Based on these goals, the Xenpozyme patients demonstrated a 23.9% improvement in DLco compared to a 3% improvement in placebo. Patients treated with Xenpozyme also saw an average 38.9% reduction in spleen volume compared to an increase of 0.5% in placebo. 

The pediatric leg of the trials saw similar positive results with a mean relative improvement of 45.9% in percent predicted DLco. All eight participants also saw an average 46.7% spleen volume reduction by the end of the 52 weeks. Sanofi also recorded lower liver volumes and improved platelet counts in participants by the end of the trials. 

After demonstrating convincing results, Xenpozyme is approved in major markets like the US, Japan, and Europe. Sanofi’s drug provides reprieve for patients with ASMD who had few other treatment options before Xenpozyme. While it might not be a blockbuster for Sanofi, it is a testament to the power of science and medicine to help treat all diseases, including ones that companies might overlook for lack of profit. 

Author

Reed Slater