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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