| Antisense-mediated exon 51 skipping restores local dystrophin expression in muscle of Duchenne muscular dystrophy patients.
A. Aartsma-Rus1, J.J.G.M. Verschuuren2, A.A.M. Janson3, G. Platenburg3, G-J.B. van Ommen1, J.C.T. van Deutekom1,3 1) Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands; 2) Department of Neurology, Leiden University Medical Center, Leiden, the Netherlands; 3) Prosensa B.V. Leiden, the Netherlands.
Antisense-mediated reading frame restoration is currently one of the most promising therapeutic approaches for Duchenne muscular dystrophy (DMD). In this approach, antisense oligoribonucleotides (AONs) induce specific exon skipping during pre-mRNA splicing. They have been successful in repairing the disrupted open reading frame accompanied by the generation of internally deleted, partially functional Becker-like dystrophins. Proof of concept has been achieved in cultured muscle cells from patients, as well as in the mdx mouse model. As an essential step towards broad clinical studies and future applications, we here evaluated the effect of a single, intramuscular dose of DMD AON PRO051. Four DMD patients with different mutations were included on basis of eligible mutation, adequate condition of the target muscle, and positive in vitro PRO051 skip-response. A dose of 0.8 mg PRO051, without any excipient, was injected locally into tibialis anterior muscle and a biopsy was taken after 4 weeks. Exon 51 skipping on RNA level and restoration of dystrophin expression was confirmed for each patient, as demonstrated by RT-PCR, immunohistochemical and western blot analyses. Dystrophin levels were ~10% of wild type levels, except for one patient who suffered from a severe loss of muscle fibers and profound signs of dystrophy in his tibialis muscle . The AON was well tolerated and did not provoke serious adverse events in any of the patients. Our results provide a strong basis for subsequent studies on systemic treatment of DMD patients.
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