Results of Prosensa’s Extended Phase I/II Exon-skipping Trial in Duchenne Muscular Dystrophy Published in the New England Journal of Medicine

Leiden, March 24, 2011 – Prosensa, the Dutch biopharmaceutical company focusing on RNA modulating therapeutics, announces the publication of results from a phase I/II and 12-week extension study of its lead product, PRO051 (GSK2402968) for the treatment of Duchenne Muscular Dystrophy (DMD) in the New England Journal of Medicine (NEJM)[1].
PRO051 (GSK2402968) is an antisense oligonucleotide designed to induce skipping of exon 51 of the dystrophin gene. The published data confirmed the safety and tolerability of the drug in all patients and the 12-week extension study reported a modest improvement in walking distance in the six-minute walk test.

The phase I/II open label study was designed to investigate induction of dystrophin expression and to test the safety and tolerability of the drug. PRO051 (GSK2402968) was given to 12 patients, who received weekly subcutaneous injections at different dose levels. All patients entered an open-label long-term extension study after completion of the initial five weeks of the trial.

The study was conducted under the sponsorship of Prosensa at the University Hospital in Leuven (Belgium) and the Queen Silvia Children’s Hospital in Gothenburg (Sweden) with support from Leiden University Medical Center (The Netherlands). “The publication of the phase I/II clinical trial results in the New England Journal of Medicine is a recognition of Prosensa’s exon skipping approach for the treatment of DMD,” commented Dr Judith van Deutekom, the senior author on the publication and Prosensa’s Head of Drug Discovery.

PRO051 (GSK2402968) induced exon skipping in patients receiving 2 mg/kg or higher doses. Post treatment muscle biopsies confirmed that dystrophin expression ranged between 80% and 100% of muscle fibers in six patients and 60% to 80% in four patients. Results of the 12-week extension study showed an improvement of patients in the six-minute walk test. This was confirmed with 24-week extension data, which was presented at the 15th International Congress of the World Muscle Society in Japan, October 12-16, 2010. Results of the 48-week extension study will be presented at the 2011 Annual Meeting of the American Academy of Neurology in Honolulu, April 9-16. Definitive proof of efficacy and safety is being investigated in ongoing controlled clinical studies. PRO051 (GSK2402968) is currently in phase III clinical trials.

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