Synthesis and in vitro anticancer activity of new gemcitabine-nucleoside analogue dimers containing methyltriazole or ester-methyltriazole linker

Two series of novel gemcitabine-nucleoside analogue dimers were synthesized using the 'click' chemistry approach. In the first series of dimers (21-30), the nucleoside units were connected with a stable methyltriazole 4N-3'(or 5')C linker whereas in the second series (31-40) with a cleavable ester-methyltriazole 4N-3'(or 5')C linker. Dimers 21-40 were evaluated for their cytotoxic activity in five human cancer cell lines such as cervical (HeLa), nasopharyngeal (KB), lung (A549), brain (U87), liver (HepG2) and normal dermal fibroblast cell line (HDF) using the sulforhodamine B (SRB) assay. Compound 29 comprising two gemcitabine (dFdC) units exhibited the highest activity among dimers 21-30. The activity of compound 29 was higher than that of dFdC in all the studied cancer cell lines. A similar order of activity was observed for compounds 25, 28, and 30. The best activity among all the dimers synthesized was displayed by compound 39, comprising two gemcitabine units with a cleavable linker. The activity of compound 39 was 5 to 9 times higher than that of dFdC, depending on the cell line. In addition, marked cytotoxic activity was shown by compounds 31, 36, 38, and 40.