The United States Food and Drug Administration (FDA) has granted Breakthrough Therapy designation for GlaxoSmithKline's (GSK's) investigational compound drisapersen (previously GSK2402968/PRO051) for the potential treatment of patients with Duchenne Muscular Dystrophy.

The Breakthrough Therapy designation is one of several programmes created by the FDA to expedite the development and review of drugs for serious or life-threatening conditions and was enacted in 2012 as part of the Food and Drug Administration Safety and Innovation Act (FDASIA).

DMD is a severely debilitating childhood neuromuscular disease that affects one in 3,500 live male births. This rare disease is caused by mutations in the dystrophin gene, resulting in the absence or defect of the dystrophin protein.

GSK’s clinical development plan evaluates the effect of drisapersen in ambulant (phases II and III) and non-ambulant boys (phase I) with DMD who have dystrophin gene mutations amenable to an exon 51 skip. Up to 13 per cent of boys with DMD have dystrophin gene mutations/deletions amenable to an exon 51 skip.  

The Breakthrough Therapy designation was based on results from the phase II Study (DMD114117), presented in April at Cold Spring Harbour.

GSK is developing drisapersen under an exclusive, worldwide license from the Dutch company, Prosensa Holding BV.

Drisapersen, (previously GSK2402968/PRO051) an anti-sense oligonucleotide, which induces exon skipping of exon 51, is currently in late stage development for DMD. It has been designated orphan drug status in the EU and US, and is being developed as part of an alliance between GlaxoSmithKline and Prosensa.

The dystrophin gene is the largest gene in the body, consisting of 79 exons. Exons are small sequences of genetic code which lead to the manufacture of sections of protein. In DMD, when certain exons are mutated/ deleted, the RNA cannot read past the fault. This prevents the rest of the exons being read, resulting in a non-functional dystrophin protein and the severe symptoms of DMD.

NA-based therapeutics, specifically anti-sense oligonucleotides inducing exon skipping, are currently in development for DMD. This technology uses small pieces of DNA called anti-sense oligonucleotides to skip a defective exon and thereby correct the reading frame, enabling the production of a novel dystrophin protein. Up to 13 per cent of boys with DMD have dystrophin gene mutation/ deletions amenable to an exon 51 skip.

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