Chiesi Group’s Filsuvez is the second drug to win FDA approval for epidermolysis bullosa and the first for junctional EB, a more severe form of the rare skin disease. The birch tree bark-derived drug is from Chiesi’s $1.25 billion Amryt Pharma acquisition.

By FRANK VINLUAN
The rare inherited disorder epidermolysis bullosa, or EB, leads to skin so fragile that it tears like tissue paper. The resulting wounds and blisters are slow to heal and prone to infection. On Tuesday, the FDA approved a Chiesi Group drug developed to promote faster wound healing in EB patients.

Privately held Chiesi will market its new drug as Filsuvez, the same brand name for the product in Europe, where it won its first regulatory approval last year. The FDA decision for this topical gel covers the treatment of patients age six months and older.

EB stems from a mutation to the gene that codes for a certain type of collagen important for anchoring the dermal and epidermal skin layers. Without this collagen, the skin becomes susceptible to injury. There are five major types of EB. In the most common form, wounds usually heal quickly. The FDA’s approval of Filsuvez covers the treatment of patients with two rarer and more severe types of the disease: dystrophic EB and junctional EB.

Filsuvez’s active pharmaceutical ingredient is birch triterpenes, a botanical substance extracted and refined from the bark of two types of birch trees native to Europe. That substance is delivered in a gel made from sunflower oil. This topical product is meant to be applied to a wound in a thin layer each time a patient changes dressings. Filsuvez’s mechanism of action is unknown, but lab tests showed the active ingredient promoted the differentiation of skin cells into mature epithelial skin cells. The drug is intended to help wounds heal more quickly.

FDA approval of Filsuvez is based on data from a clinical trial that enrolled 233 adults and children with dystrophic EB and junctional EB. Participants were randomly assigned to receive the study drug or a placebo gel applied to partial thickness wounds every one to four days for 90 total days. The main goal was achieving complete closure of the target wound within 45 days. Results showed that 41.3% of patients in the Filsuvez arm met this goal compared to 28.9% of those in the placebo group. The most common adverse reactions reported in the study were itching and pain at the site where the gel was applied.

“The FDA’s decision to approve Filsuvez provides those living with EB a safe and effective treatment option for the most prominent and difficult symptom of EB, open wounds that may not heal,” Brett Kopelan, executive director of EB patient group Debra of America, said in a prepared statement.

Filsuvez is the second EB therapy approved by the FDA this year. In May, the FDA greenlit Krystal Biotech’s Vyjuvek, a gene therapy that addresses the genetic mutation at the root of the disease. Vyjuvek is administered as a topical gel and in a first for a gene therapy, this treatment is redosable. The product, sold in vials carrying a wholesale price of $24,250 each, is administered as drops applied to wounds once a week.

Vyjuvek was the first FDA-approved treatment for dystrophic EB. Filsuvez is the first to win FDA approval in junctional EB, a more severe form in which blisters start developing in infancy. Parma, Italy-based Chiesi did not respond to emailed questions about the drug’s price and the timeline for a product launch.

Filsuvez came to Chiesi from Amryt Pharma. Though Amryt was able to steer the drug to a European Medicines Agency approval for the treatment of EB in 2022, the FDA turned down the drug that year, asking for more data. At the start of this year, Chiesi announced a deal to acquire Amryt for $1.25 billion up front. Contingent value rights tied to milestones could have Chiesi paying out up to $225 million more.
The pipeline of Chiesi Global Rare Diseases, the Boston-based rare disease unit of Chiesi Group, includes an EB gene therapy that also came from the Amryt acquisition. This program is in preclinical development.

Photo by Flickr user Thomas via a Creative Commons license