Leiden, The Netherlands, Sept. 6, 2013 (GLOBE NEWSWIRE) -- Prosensa Holding N.V. (NASDAQ: RNA), the Dutch biopharmaceutical company focusing on RNA-modulating therapeutics for rare diseases with high unmet need, today announced the dosing of the first patient in its Phase I/II clinical trial of PRO053, an exon-skipping compound for the treatment of Duchenne muscular dystrophy (DMD). "We are pleased that our fourth exon-skipping compound, PRO053, has advanced into clinical trials." Giles Campion, Prosensa's Chief Medical Officer, said. "Bringing new drug candidates, such as PRO053, into the clinic exemplifies how we can leverage our scientific and regulatory expertise gleaned from the experience in advancing the investigational development compound, drisapersen, through the clinic. Most importantly, a broader clinical portfolio may offer additional patients with subtypes of DMD a much-needed potential treatment option." PRO053, the company's fourth drug development candidate, induces exon 53 skipping and may be applicable to approximately 8% of all DMD patients. This is an open-label study designed to assess the safety, efficacy, tolerability and pharmacokinetics of multiple doses of PRO053 in a subset of patients with DMD. The primary outcome measure of the study will be change from baseline in the six-minute walk test (6MWT) after 48 weeks of treatment. A number of secondary outcome measures will also be assessed, including safety, muscle function and strength, and functional outcome based on a questionnaire. The initial dose-finding portion of the study will be conducted at several clinical trial sites in Europe. The study may then be extended to additional territories in and outside of Europe. Prosensa's current portfolio includes six compounds for the treatment of DMD, all of which have received orphan drug status in the United States and the European Union. The compounds use an innovative technique called exon-skipping to provide a personalized medicine approach to treat different populations of DMD patients. The company's lead investigational drug candidate, drisapersen, which was exclusively licensed to GlaxoSmithKline, is in Phase III clinical trials.