Synthesis and biological evaluation of novel diaziridinylquinone-acridine conjugates

The synthesis and biological evaluation of a homologous series of conjugates (9-13) of 2,5-diaziridinylbenzoquinone (DZQ) and 9-carbonylacridine, a DNA intercalating moiety, via a polymethylene unit (n=2-6) are described. In addition, the non-acridine compound 14, analogous to compound 12, and the 5-methyl-DZQ derivatized conjugate 15, an analog of compound 10, were also prepared. Through a Comet assay, compounds 9-13 were shown to produce DNA interstrand cross-links at submicromolar concentrations, consistent with K562 leukemia cells accumulating in the G2/M stage in the cell cycle. The cytotoxicity of compounds 9-15 was examined using a MTT assay on several human cancer cell lines, including chronic myeloid leukemia K562, the non-small cell lung cancers H596 and H460, and colon carcinoma cells BE and HT29. H460 and HT29 are rich in DT-diaphorase (DTD), and H596 and BE cells have negligible amounts of functional DTD. Under continuous exposure of drugs, except to the non-aziridine compound 19b, the IC50 values of all other compounds were determined to be in the range of 0.3-11.3 nM. Compound 10, which has a propyl linker group, was subjected to in vivo studies. When BDF1 mice with established mouse mammary carcinoma were treated with compound 10 (2 mg/kg at day 1 and 5 mg/kg at day 7), a significant delay (9-10 days) in cancer growth was recorded when compared to untreated controls. Furthermore, administration of compound 10 to nu/nu BDF1 mice bearing human lung cancer H460 xenograft (1.5 mg/kg for 10 for five consecutive days from day 13 and 17) also showed a significant reduction in tumor growth compared to untreated controls. The half-life of compound 10 in the presence of five different peptidases (porcine esterase, carboxypeptidase A, B and Y, and pepsin) was determined to be between 30 and 60 h.