Optimization And Screening Of Toxicity On Z24 Serial Compounds

Discovery toxicology applies short-term tests to screen the toxicity of new compounds during the discovery phase of new drug in order to evaluate the potential toxicity of new chemicals. One of the main tasks of discovery toxicology is primary screening of the new compounds. The primary screening can eliminate as soon as possible the compounds that are unfit for further development and can guide for synthesizing the safer compounds.Since our country joined the WTO, the strategy of the new drug studies has being conversed from imitation to innovation. Therefore, we must establish our own system of discovery toxicology. One of the main tasks of discovery toxicology is to establish a short-term toxicity optimization and screening system. So one of aims of this study is to create such a system for evaluation on toxicity of the new compounds. The screening system can evaluate general toxicity including acute toxicity and cytotoxicity, and special toxicity i.e. genotoxicity and teratogenicity. The acute oral toxicity of the new chemicals is evaluated with up-and-down method. The screening system of cytotoxicity consists of MTT colorimetric assay and the long-term inhibition of protein assay. The genotoxicity tests consist of the Ames-fluctuation test, the SOS chromotest and the in vitro cytokinesis-block micronucleus test. The method of the micromass culture of rat embryo midbrain cell is used for screening for teratogenicity.The compounds tested consist of Z24, SU5416, LI , L3 and L4. Their anticancer mechanisms are to induce apoptosis of tumor cells through the antagonism of Bcl-2, aft important antiapoptosis protein. So they can become a kind of new drugs whose mechanisms of action are different from the other anticancer drugs. The second aim of the study is to make use of the screening system we have established to predict the toxicity of the five new anticancer compounds and to provide some toxicolgical data for the selection of new drug candidate from those compounds. The main results are asfollows:The results of general toxicity tests1. Acute toxicity test: The up-and-down method was used for assessment of acute oral toxicity of Z24, SU5416, LI, L3 and L4, the results showed their LD50 to mice were respectively 669.2, >2000, 532.0, 232.0 and 627.7mg/kg.2. Cytotoxicity test: The cytotoxicities of Z24 serial compounds were compared in both the CHL cells by an MTT colorimetric assay and cell viability counting, and the midbrain cells of rat fetuses with neutral red colorimetric assay. All of the five compounds were cytotoxic to CHL cells and the midbrain cell of rat fetuses. The same colometric assays showed Z24 was the least toxic among the Z24 serial compounds. Long-term inhibition of protein assay showed that the EC506W was 331.9 folds lower than the PI5024h, because after pretreatment Hep G2 cells for 6 weeks the cells had to endure an important chemical stress during this period. The PI5024h₆w of Z24 to 3 cell populations survived for 6 weeks of treatment with 3 lower concentrations of Z24 are all lower than the PI5024h of Z24 to the untreated cells. These results indicated that the Hep G2 cell became more sensitive to Z24 after a long period of treatment with Z24.The results of special toxicity tests1. Genotoxicity tests: In Ames-fluctuation test, the Salmonella typhimurium strain TA100 and S9 were used in the assy. All the tested compounds except Z24 showed mutagenic activity in the absence of S9-mix. No genotoxicity effects of the five compounds were detected in the system with S9 activation; In Ames test, only LI showed mutagenic activity on Salmonella typhimurium strain TA100 in the absence of S9-mix. The results of Ames test were the same as the Ames-fluctuation test in the system with S9 activation. The results suggested that Ames-fluctuation test is more sensitive than Ames test. For SOS chromotest, none of five chemicals was found to induce primary DNA damage hi Escherichia coli PQ37 both with and without S9-mix. The clastogenic effect was detected on CHL cell for all of the...