DMD: Sarepta Expands Exon-Skipping Program

Biopharmaceutical company Sarepta Therapeutics has announced it will expand the focus of its exon-skipping program for Duchenne muscular dystrophy (DMD) by developing compounds that target exons 45, 50 and 53 of the dystrophin gene, in addition to continuing to develop eteplirsen, which targets exon 51 of this gene.

Targeting exon 53, Sarepta says, will potentially address one of the most prevalent sets of mutations in DMD amenable to treatment via exon skipping: deletions of dystrophin exons 42-52, 45-52, 47-52, 48-52, 49-52, 50-52 or 52.

Currently, Sarepta’s experimental exon-skipping drug eteplirsen is undergoing clinical testing in boys with DMD, with very encouraging early results.

Dystrophin gene exons are sections of the gene that code for the dystrophin protein. (Dystrophin's absence from muscle tissue underlies DMD.) The experimental DMD treatment strategy known as exon skipping is based on laboratory studies showing that causing cells to ignore, or "skip," certain exons when making dystrophin protein can lead to production of functional, though shortened, dystrophin. Different dystrophin mutations require drugs that target different exons.

Sarepta, of Cambridge, Mass., announced its plans to develop new exon-skipping compounds in a Nov. 26, 2012, press release.

Prosensa also expanding exon-skipping program

In October 2012, Dutch biotechnology company Prosensa announced development of compounds targeting dystrophin exons 44, 45, 52, 53 and 55.

Some of Prosensa's exon-skipping program is conducted in collaboration with multinational pharmaceutical company GlaxoSmithKline (GSK).

GSK's drug drisapersen, which targets exon 51, is in clinical testing in DMD.

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