Mutagenic activation of CL64,855, an anti-Trypanosoma cruzi nitroderivant, by bacterial nitroreductases

Evaluation of genotoxic effects of new molecules with possible trypanocidal activity for Chagas disease treatment

Chagas disease is responsible for a large number of human infections and many are also at risk of infection. There is no effective drug for Chagas disease treatment. The Institute of Pharmaceutical Technology at Fiocruz, Brazil, has designed three nitro analogs of the nitroimidazole-thiadiazole, megazol: two triazole analogs PTAL 05-02 and PAMT 09 and a pyrazole analog PTAL 04-09. A set of Salmonella enterica serovar Typhimurium strains were used in the bacterial reverse mutation test (Ames test) to determine the mutagenicity and cytotoxicity of megazol and its nitro analogs. Megazol presented positive mutagenic activity at very low concentration, either with or without metabolic activation S9 mix. The mutagenic response of the analogs was detected at higher concentration than the lowest megazol concentration to yield mutagenic activity showing that new advances can be made to develop new analogs. The micronucleus test with rat macrophage cells was used in the genotoxic evaluation. The analogs were capable of inducing micronucleus formation and showed cytotoxic effects. PTAL 04-09 structural modifications might be better suitable for the design of promising new drugs candidate for Chagas' disease treatment.

In vitro and in vivo chromosomal aberrations induced by megazol

With the re-emergence of Human African Trypanosomiasis (HAT) on the one hand, which are increasingly resistant to current therapies, and the stage-dependent effectiveness or even the prohibitive cost of these therapies on the other hand, megazol, a 5-nitroimidazole thiadiazole highly active against various trypanosomal species, was assessed for its genotoxic potential. Very little information has become available until now. Two batches of megazol were provided by two different suppliers: Far-Manguinhos, a part of the Fiocruz foundation, under the Brazilian Minister of Health, and Delphia, a French company. These two batches, obtained by different synthetic routes, were studied by means of the in vitro micronucleus assay on L5178Y mouse lymphoma cells, in its microscale version. Both batches of magazol displayed a strong genotoxic activity in this screening assay. A second batch from Delphia was then investigated by use of two tests, i.e. the in vitro metaphase analysis with human lymphocytes and the in vivo micronucleus test in rat bone-marrow. Megazol was shown to be a potent inducer of in vitro and in vivo chromosomal aberrations. Although megazol is a potent trypanocidal agent and is orally bio-available, its toxicity dictates that it should not be developed further for the treatment of HAT and Chagas disease. All development work has therefore been discontinued.