Chemotherapeutics overcoming nonsense mutation-associated genetic diseases: medicinal chemistry of negamycin.

Nonsense mutations caused by the presence of an in-frame premature termination codon (PTC) account for ~10% of gene lesions that together cause over 1800 inherited human diseases. One approach to treating genetic diseases that stem from PTCs is selective promotion of translational readthrough in a PTC using 'readthrough compounds' that can lead to partial restoration of full-length functional protein expression. (+)-Negamycin, a natural dipeptide-like antibiotic, may restore some dystrophin expression in the skeletal muscles of mice with Duchenne muscular dystrophy, and this compound has been recognized as a potential therapeutic agent for diseases caused by nonsense mutations. In an effort to develop new candidate molecules with improved activities, we established the efficient total synthesis in eight steps of (+)-negamycin using both achiral and chiral starting material. These routes provided a deamino derivative with in vivo readthrough activity with potential for long-term treatment. In a separate approach, we discovered two natural negamycin analogs, 3-epi-deoxynegamycin and its leucine derivative, which are potent readthrough compounds effective against nonsense mutations of eukaryotes but not prokaryotes. These compounds fail to display antimicrobial activity. More potent derivatives, whose structure is derived from 3-epi-deoxynegamycin, were identified and their chemistry is discussed in this review.