Novel 1,2,4-triazole and purine acyclic cyclopropane nucleoside analogues: synthesis, antiviral and cytostatic activity evaluations.

Benci, Krešimir; Suhina, Tomislav; Mandić, Leo; Pavelić, Sandra Kraljević; Paravić, Andrea Tomljenović; Pavelić, Krešimir; Balzarini, Jan; Wittine, Karlo; Mintas, Mladen

BACKGROUND Several published studies indicate that the acyclic guanine nucleoside analogues possessing bis(1,2-hydroxymethyl) substituted cyclopropane rings mimicking the sugar moiety are potent inhibitors of replication of several herpes viruses. METHODS Established synthetic methods and antiviral and cytostatic activity assays were used for the evaluation of new 1,2,4-triazole and purine acyclic nucleoside analogues. RESULTS The synthesis of new types of acyclic nucleoside analogues which incorporate 1,2,4-triazole or purine moiety bound via flexible methylenic spacer to the bis(1,2-hydroxymethyl) cyclopropane ring. None of the new compounds showed pronounced antiviral activities at subtoxic concentrations on a broad panel of DNA and RNA viruses. Evaluation of their affinity for herpes simplex type 1 (HSV-1) and varicella-zoster virus-encoded thymidine kinases (VZV TK) also showed that none of the compounds was able to significantly inhibit 1 μM deoxythymidine phosphorylation by HSV-1 and VZV TK at 500 μM concentrations. The in vitro cytostatic activity evaluation results indicated a weak antiproliferative activity for all tested compounds. Only 6-pyrrolylpurine derivative bearing a carboxylic group substituted cyclopropane ring produced a rather slight inhibitory effect at higher micromolar concentrations on a breast carcinoma cell line (MCF-7) and no cytotoxic effect on human normal fibroblasts (WI 38). CONCLUSIONS The lack of antiherpetic activity may be due to poor, if any, recognition of the compounds by virus-induced nucleoside kinases as an alternative substrate to become metabolically activated.