Current protocol of a research phase I clinical trial of full-length dystrophin plasmid DNA in Duchenne/Becker muscular dystrophies. Part III. Ethical considerations

The role of corticosteroids in muscular dystrophy: a critical appraisal

Over the years various steroid trials have been conducted in Duchenne muscular dystrophy (DMD). In children who are still able to walk as well as in those who are wheelchair-bound, corticosteroids have been found to stabilize muscle strength for a period of time. Controlled clinical observations have shown that some boys remain ambulatory for years longer than reported in natural history data. The two main steroids used are prednisone/prednisolone and deflazacort. They are probably equally effective in stabilizing muscle strength but may have different side-effect profiles; for instance, deflazacort causes less weight gain. The exact mechanism by which steroids slow the dystrophic process is under investigation. DMD children treated long term also seem to develop other complications of the condition less frequently. For instance, they develop respiratory insufficiency later and have fewer cardiac symptoms. The therapeutic value of corticosteroids is limited, but these drugs represent the best treatment option currently available.

Phase I Study of Dystrophin Plasmid-Based Gene Therapy in Duchenne/Becker Muscular Dystrophy

Nine patients with Duchenne or Becker muscular dystrophy were injected via the radialis muscle with a full-length human dystrophin plasmid, either once with 200 or 600 microg of DNA or twice, 2 weeks apart, with 600 microg of DNA. In the biopsies taken 3 weeks after the initial injection, the vector was detected at the injection site in all patients. Immunohistochemistry and nested reverse transcription-polymerase chain reaction indicated dystrophin expression in six of nine patients. The level of expression was low (up to 6% weak, but complete sarcolemmal dystrophin staining, and up to 26% partial sarcolemmal labeling). No side effects were observed, nor any cellular or humoral anti-dystrophin responses. These results suggest that exogenous dystrophin expression can be obtained in Duchenne/Becker patients after intramuscular transfer of plasmid, without adverse effects, hence paving the way for future developments in gene therapy of hereditary muscular diseases.

Novel therapies for Duchenne muscular dystrophy

The development of therapeutic strategies that overcome the unique problems posed by Duchenne muscular dystrophy (DMD) has lead to the development of many contemporary approaches to human disease in general. Various treatment approaches have been explored--such as pharmacological therapies and cell-based, cytokine, and genetic therapies--that are all targeted to specific features of dystrophic DMD muscle pathology. In genetic therapies, the large size of the dystrophin gene has necessitated the development and use of novel functional minidystrophin and microdystrophin genes, muscle-specific promoter systems, and gutted adenoviral systems. In addition to these well defined viral strategies, plasmid vectors and the upregulation of utrophin (a dystrophin homologue) have potential. Various novel genetic approaches--such as antisense-mediated exon skipping, gene correction, and new cytokine approaches--are also being developed. Together these exciting developments bring an effective treatment for DMD closer than ever before.