“Receiving an orphan drug designation from the FDA for our gene-therapy candidate, AP103, is a significant development for patients suffering from EB and provides additional momentum to our development pipeline,” Joe Wiley, CEO of Amryt Pharma, the medication’s developer, said in a press release.
Orphan drug status provides companies with incentives to support the development of medicines that might treat rare diseases, defined as those affecting fewer than 200,000 people in the U.S.
These include waivers for FDA application fees, and a seven-year period of marketing exclusivity should AP103 win regulatory approval.
“Unlike other gene therapies that rely on viral vectors, AP103 is based on a novel polymer-based topical delivery platform,” Wiley added, “which we believe offers potential advantages in the gene-therapy field and has potential to be used in other genetic skin conditions.”
This polymer, called HPAE (highly branched poly beta-amino ester), is reported to be relatively inexpensive and easy to manufacture. According to Amryt, using the polymer means being able to deliver genes in a stable manner while avoiding the immune responses that viral-based gene therapies can provoke.
In the case of AP103, HPAE polymers provide patients with a healthy copy of COL7A1, the gene that is mutated in DEB.
COL7A1 produces the collagen VII protein, which plays a key role in attaching different layers of skin to each other. Skin grows fragile without it, easily blistering and tearing.
The COL7A1 gene delivered by AP103 will not remain inside patients’ cells, meaning that periodic reuse would be necessary — and increasing the importance of the therapy not provoking an immune response via a viral vector.
In preclinical studies, use of the HPAE polymer to deliver a healthy gene showed no evidence of toxicity, and led to collagen VII production in keratinocytes — the main cell type found in the top layer of skin.
AP103 is also expected to receive orphan drug status in Europe.
In addition to AP103, Amryt is developing a topical gel called Filzuvez to treat EB. Results from the ongoing Phase 3 EASE trial (NCT03068780) have shown that Filsuvez significantly improved would closure in people with DEB, junctional EB, or Kindler syndrome, compared with a placebo gel.
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