negamycin and Muscular-Dystrophy--Duchenne

In this paper I review the results of the treatments directed to modify the mRNA of dystrophin with the goal of converting the severe Duchenne type to the milder Becker muscular dystrophy. Antisense oligomers potential to modify Duchenne muscular dystrophy (DMD) gene expression and therapeutic strategies to induce ribosomal read-through of nonsense mutations (PTC124) are described. They are an important advance in the treatment of DMD, so far unspecific. Significant expression of new dystrophin is observed in biopsies of peripheral muscle, although the functional improvement is not so encouraging. New modification of chemistries are expected to improve the liberation, broad distribution in muscles, as well as their efficacy and safety enough to allow a positive chronic treatment of DMD.

Topics: Amino Acids, Diamino; Aminoglycosides; Animals; Clinical Trials, Phase I as Topic; Clinical Trials, Phase II as Topic; Codon, Nonsense; Disease Models, Animal; Dogs; Dystrophin; Exons; Gene Expression Regulation; Genetic Therapy; Humans; Mice; Mice, Inbred mdx; Morpholinos; Muscle, Skeletal; Muscular Dystrophy, Duchenne; Oligonucleotides; Oligonucleotides, Antisense; Oxadiazoles; Protein Biosynthesis; RNA Splicing; Suppression, Genetic

Effective treatment for Duchenne muscular dystrophy (DMD) is currently unavailable. Readthrough of disease-causing premature termination codons might alleviate the symptoms of genetic diseases caused by nonsense mutations. Several ribosome-binding compounds, including selective antibiotics and synthetic novel small molecules, induce translational readthrough, restoring full-length functional proteins. Here in this innovative therapeutic strategy has been summarized with a focus on DMD. We have previously reported that negamycin restored dystrophin expression with less toxicity than gentamicin in mdx mice. To explore more potent readthrough inducers, we established the transgenic mouse called READ (readthrough evaluation and assessment by dural receptor) for readthrough-specific detection. Using READ mice, we discovered drug candidates, including sterically negamycin-like small molecules and aminoglycoside derivatives. The newly developed small molecules induced dose-dependent readthrough with greater potency than ataluren in vitro and promoted the expression of dystrophin and reduction in serum creatine kinase activity in mdx mice. Moreover, the aminoglycoside derivative restored both dystrophin protein and contractile function of mdx skeletal muscles with appreciably higher readthrough activity and lower toxicity than that of gentamicin. Furthermore, we confirmed the efficacy of a thioglycolate-based depilatory agent to enhance the topical delivery of skin-impermeable drugs, including aminoglycosides. These promising new chemotherapeutic agents with beneficial effects on readthrough action, lower toxicity, and transdermal delivery may have significant value in treating or preventing genetic diseases caused by nonsense mutations.

Topics: Amino Acids, Diamino; Aminoglycosides; Animals; Codon, Nonsense; Creatine Kinase; Dose-Response Relationship, Drug; Drug Design; Dystrophin; Humans; Injections, Intradermal; Mice; Molecular Targeted Therapy; Muscular Dystrophy, Duchenne; Skin

Topics: Amino Acids, Diamino; Humans; Muscular Dystrophy, Duchenne

The ability of aminoglycoside antibiotics to promote read-through of nonsense mutations has attracted interest in these drugs as potential therapeutic agents in genetic diseases. However, the toxicity of aminoglycoside antibiotics may result in severe side effects during long-term treatment. In this paper, we report that negamycin, a dipeptide antibiotic, also restores dystrophin expression in skeletal and cardiac muscles of the mdx mouse, an animal model of Duchenne muscular dystrophy (DMD) with a nonsense mutation in the dystrophin gene, and in cultured mdx myotubes. Dystrophin expression was confirmed by immunohistochemistry and immunoblotting. We also compared the toxicity of negamycin and gentamicin, and found negamycin to be less toxic. Furthermore, we demonstrate that negamycin binds to a partial sequence of the eukaryotic rRNA-decoding A-site. We conclude that negamycin is a promising new therapeutic candidate for DMD and other genetic diseases caused by nonsense mutations.

Topics: Amino Acids, Diamino; Animals; Body Weight; Brain Stem; Dystrophin; Gene Expression Regulation; Gentamicins; Male; Mice; Mice, Inbred C57BL; Mice, Inbred mdx; Muscle, Skeletal; Muscular Dystrophy, Animal; Muscular Dystrophy, Duchenne; Myocardium; RNA, Ribosomal