Several 5-N-alkyl and 5-N,N-dialkylcarbamoyl substituted analogues of the anti-human immunodeficiency virus (HIV) type 1 lead compound[1-[2‘,5’-bis-O-(tert-butyldimethylsilyl)-β-D-ribofuranosyl]-5-(N,N-dimethylcarbamoyl)-1,2,3-triazole]-3‘-spiro-5“-(4”-amino-1“,2”-oxathiole-2“,2”-dioxide) have been prepared and evaluated as inhibitors of HIV-1 replication. A new regiospecific synthetic procedure is described. The compounds were prepared by cycloaddition of the appropriate glycosylazide to 2-oxo-alkylidentriphenyl-phosphoranes, followed by treatment with primary or secondary amines, to yield, exclusively, 5-substituted 1,2,3-triazole-TSAO analogues. Several 5-substituted 1,2,3-triazole-TSAO derivatives proved to be potent inhibitors of HIV-1 replication with higher antiviral selectivity than that of the parent TSAO prototype.

Trabectedin (Yondelis) is a potent antitumor drug that has the unique characteristic of killing cells by poisoning the DNA nucleotide excision repair (NER) machinery. The basis for the NER-dependent toxicity has not yet been elucidated but it has been proposed as the major determinant for the drug's cytotoxicity. To study the in vivo mode of action of trabectedin and to explore the role of NER in its cytotoxicity, we used the fission yeast Schizosaccharomyces pombe as a model system. Treatment of S. pombe wild-type cells with trabectedin led to cell cycle delay and activation of the DNA damage checkpoint, indicating that the drug causes DNA damage in vivo. DNA damage induced by the drug is mostly caused by the NER protein, Rad13 (the fission yeast orthologue to human XPG), and is mainly repaired by homologous recombination. By constructing different rad13 mutants, we show that the DNA damage induced by trabectedin depends on a 46–amino acid region of Rad13 that is homologous to a DNA-binding region of human nuclease FEN-1. More specifically, an arginine residue in Rad13 (Arg961), conserved in FEN1 (Arg314), was found to be crucial for the drug's cytotoxicity. These results lead us to propose a model for the action of trabectedin in eukaryotic cells in which the formation of a Rad13/DNA-trabectedin ternary complex, stabilized by Arg961, results in cell death. (Cancer Res 2006; 66(16): 8155-62)

BACKGROUND AND PURPOSE PM01183 is a new synthetic tetrahydroisoquinoline alkaloid that is currently in phase I clinical development for the treatment of solid tumours. In this study we have characterized the interactions of PM01183 with selected DNA molecules of defined sequence and its in vitro and in vivo cytotoxicity.EXPERIMENTAL APPROACH DNA binding characteristics of PM01183 were studied using electrophoretic mobility shift assays, fluorescence‐based melting kinetic experiments and computational modelling methods. Its mechanism of action was investigated using flow cytometry, Western blot analysis and fluorescent microscopy. In vitro anti‐tumour activity was determined by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay and the in vivo activity utilized several human cancer models.KEY RESULTS Electrophoretic mobility shift assays demonstrated that PM01183 bound to DNA. Fluorescence‐based thermal denaturation experiments showed that the most favourable DNA triplets providing a central guanine for covalent adduct formation are AGC, CGG, AGG and TGG. These binding preferences could be rationalized using molecular modelling. PM01183−DNA adducts in living cells give rise to double‐strand breaks, triggering S‐phase accumulation and apoptosis. The potent cytotoxic activity of PM01183 was ascertained in a 23‐cell line panel with a mean GI₅₀ value of 2.7 nM. In four murine xenograft models of human cancer, PM01183 inhibited tumour growth significantly with no weight loss of treated animals.CONCLUSIONS AND IMPLICATIONS PM01183 is shown to bind to selected DNA sequences and promoted apoptosis by inducing double‐strand breaks at nanomolar concentrations. The potent anti‐tumour activity of PM01183 in several murine models of human cancer supports its development as a novel anti‐neoplastic agent.