Abstract Cisplatin is the standard anti-tumor drug for mesothelioma, and other malignant tumors, however acute renal failure due to renal tubule injury is often induced as its adverse event. Hence, the dose of cisplatin is limited by the patient's renal function. We developed the Cisplatin controlled release complex that released cisplatin steadily, and relieved the adverse event, and examined its characteristics. 1) Slow release of cisplatin from novel complex Concentration of cisplatin penetrated from the dialysis membrane was measured by ICP atomic emission spectrometer. - Approximately 4% of cisplatin was released by day1 (initial burst was very low), and 10% of cisplatin was released by day 15, while free cisplatin oozed out from dialysis membrane immediately. 2) Cytotoxicity of novel complex in vitro Cytotoxicity to murine mesothelioma cell line was measured by MTT assay. - Over 10 μg/mL of cisplatin, novel complex possessed cytotoxicity, but under 5 μg/mL of novel cisplatin complex did not inhibit the growth of the murine mesothelioma cell line. 3) Bio-distribution of novel cisplatin complex in mice Novel cisplatin complex was administrated intra-peritoneal cavity, and the cisplatin concentration of each organ was measured at 1, 3, 5, 7 days after the administration. - Cisplatin of the complex was kept the concentration in the blood after the initial peak concentration, while free cisplatin was disappeared immediately. Furthermore, cisplatin was found in the concentrated amount in the liver, since novel complex was accumulated in the liver at the early phase as a storage of cisplatin, and cisplatin was released steadily into the bloodstream. 4) Acute toxicity test for mouse 50 mg/kg of novel cisplatin complex was administrated into the peritoneal cavity, and mice were observed. - All mice were alive with 9 days after cisplatin complex administration. 5) The anti-tumor efficacy of novel cisplatin complex in mesothelioma bearing mice Each 10 mg/kg of cisplatin formulation was administrated into the peritoneal cavity at five days after subcutaneous inoculation of murine mesothelioma cells. - On 9 days after cisplatin formulation administration, novel cisplatin complex was more effective than free cisplatin. Conclusions; We have demonstrated that novel cisplatin complex that releases cisplatin steadily into the bloodstream can be successfully used for the chemotherapy without severe adverse event, despite high dose administration. Although much additional study of this complex is required, the results in this study warrant additional development of this complex for potential investigation into its use in clinical tumor chemotherapy for mesothelioma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4452. doi:10.1158/1538-7445.AM2011-4452