A Preliminary Toxicology Study Of A Novel Hsp90 Inhibitor-SNX-2112

At present, malignant tumor, a serious threat to human health, has become a focus of attention worldwide. Traditional chemotherapy and radiotherapy always tend to incur serious toxic side effects to patients, for lack specificity. Therefore, the clinical problem is urgently needed to solve is to find new, safe and effective anti-humor drugs. SNX-2112 is a novel screened Hsp90 inhibitor in recent years, which can specifically inhibit Hsp90 activity and induce their client proteins degradation resulting in cancer cell apoptosis, therefore currently SNX-2112 is considered to be a promising anti-cancer drug for exploring.Objectives To carry out preliminary safety evaluation of SNX-2112 by acute toxicity test, mouse bone marrow micronucleus test, micronucleus test in human peripheral blood lymphocytes and mammalian cell chromosome aberration test, all of which will provide a scientific basis for clinical application of Hsp90 inhibitors with self-owned intellectual property rights.Methods In acute toxicity test, samples were supplied to animal by mainline, intraperitoneal injection and intragastring respectively. After administration, animals were observed respectively with generic states, toxicity appearance, mortality and the weight during the trial period. In mouse bone marrow micronucleus test, samples were supplied to mice by mainline. Bone marrow was obtained from both femurs. Smears were observed under immersion objective. Micronucleus rate was used to show genetic toxicity. PCE ratio in RBC was used to show marrow toxicity. Micronucleus test in human peripheral blood lymphocytes, a combined approach employing conventional micronucleus(MN) assay and cytokinesis-blocked micronucleus(CBMN) assay was utilized to assess the genotoxicity of SNX-2112, peripheral blood lymphocytes were treated with different concentrations of samples for 24h, and the slide preparation of micronucleus were performed using the routine culture of micro-whole blood. The slides were observed under immersion objective. The incidence of micronuclei(MN) and cytokinesis-block micronucleus(CBMN) were calculated. The results were statistically compared. In mammalian cell chromosome aberration test, with or without the presence of S9 metabolic activation, mammalian cells were treated with different concentrations of samples for 24h or 48h. The slides were observed under immersion objective. The rate of chromosome aberration were calculated.Results In acute toxicity test, compare the results of three acute toxicity tests, the results showed that mainline is the best route of administration. The LD50 of SNX-2112 by mainline in mice and rats is 67.79mg/kg and 28.52mg/kg respectively. The LD50 of SNX-2112 by intraperitoneal injection line in mice is 102.35mg/kg. The LD50 of SNX-2112 by intragastring in mice is 132.23mg/kg. In mouse bone marrow micronucleus test, compare PCE ratio in RBC between each groups, there was no significant difference(P> 0.05). Compare MPCE ratio in PCE between each groups. Blank solvent group and SNX-2112 low-dose group, compared with the negative control was no significant difference(P> 0.05). SNX-2112 middle-dose and SNX-2112 high-dose, compared with the negative control was significant difference(P< 0.05). Results showed that in a certain dose range, SNX-2112 has no obvious damage on mouse chromosome. In MN assay and CBMN assay, SNX-2112 could induce the increase of MN rate and CBMN rate in Peripheral Blood Lymphocytes, all with a dose-dependent relationship, indicating a certain genetic toxicity. Compare micronucleus rates between each groups. The micronucleus rates of treatment groups were higher than negative control. The micronucleus rate of the low-dose group(1.25μg/ml) was significantly lower than positive control(MMC 1.00μg /ml), while that of the middle-dose group(2.50μg/ml) was close to positive control. Nevertheless, the micronucleus rate of the high-dose group(5.00μg/ml) was significantly higher than positive control. These results suggest that the mutagenic activity of SNX-2112 was significantly lower than MMC. In mammalian cell chromosome aberration test, metaphase cells have been not observed in the experimental groups. Therefore, chromosome aberrations can not be analyzed. Our results demonstrated that chromosome aberration rate in either negative, solvent control fluctuated in normal level. Significantly increased rate of chromosomal aberration induced by positive control mitomycin C and cyclophosphamide-cell chromosome aberration rate> 20%, indicates that test system is reliable.Conclusions 1. Comparison of the three routes of administration, because of less toxicity and without side effects.Therefore, we chose intravenous administration as the final administration route, providing the scientific basis for the follow-up test.2. The results of mouse bone marrow micronucleus test show that in a certain dose range, SNX-2112 has no obvious damage on mouse chromosome.3. The results of human peripheral blood lymphocyte micronucleus test show that SNX-2112 show a certain genetic toxicity, but its mutagenicity was significantly lower than MMC.4. The results of chromosome aberration test results show that may be due to SNX-2112 and colchicine has a very strong antagonism, resulting in the test group chromosome aberrations can not be analyzed.