Chiesi’s $1.25B Amryt Buy Pays Off with FDA Approval of Filsuvez

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The FDA on Tuesday approved Chiesi Global Rare Diseases’ topical drug birch triterpenes, now to be marketed as Filsuvez, for the treatment of junctional or dystrophic epidermolysis bullosa in patients six months of age and older.

Tuesday’s regulatory win makes Filsuvez the first approved treatment for wounds related to junctional epidermolysis bullosa (EB), a rare and moderate-to-severe form of the skin disease that often develops starting from infancy, according to Chiesi.

Brett Kopelan, executive director of the non-profit debra of America, in a statement called Filsuvez’s approval an “important milestone” for patients living with junctional EB, adding that Filsuvez can also provide “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.”

The FDA’s decision is backed by data from the Phase III EASE study, a double-blinded, randomized and vehicle-controlled study that demonstrated accelerated wound healing in patients treated with Filsuvez, along with a reduction in overall wound burden and lower pain associated with changing wound dressings.

Filsuvez is a topical herbal gel mixture, containing dry extracts from two bark species—Betula pendula Roth and Betula pubescens Ehrh—as well as hybrids of both species. Its exact mechanism of action is currently unknown but based on its clinical efficacy and safety profile Filsuvez won the EU’s marketing authorization in June 2022.

The topical treatment was originally developed by Amryt Pharma, which Chiesi bought in January 2023 for $1.25 billion upfront. The deal also came with a contingent payment of up to $225 million if Filsuvez met certain milestones—including winning an FDA approval.

The Amryt acquisition also gave Chiesi two other rare disease assets: Myalept (metreleptin) for congenital or acquired generalized lipodystrophy and Mycapssa (octreotide) for acromegaly.

The FDA previously rejected Filsuvez. In February 2022, the regulator handed Amryt a Complete Response Letter, asking for additional confirmatory data to prove the topical treatment’s efficacy.

The biotech pushed back against the rejection and in June 2022 filed a formal dispute resolution request with the FDA.

With Filsuvez’s approval on Tuesday, it joins Krystal Biotech’s Vyjuvek (beremagene geperpavec-svdt), which won the FDA’s go-ahead in May 2023 for dystrophic EB. Vyjuvek is the first-ever topical and redosable gene therapy to hit the market.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. He can be reached at tristan@tristanmanalac.com or tristan.manalac@biospace.com.

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