Novel Prodrug Of Doxorubicin PDOX Anti-tumor Efficacy And Toxicity Study

Part Ⅰ:The study of a novel prodrug of Doxorubicin (PDOX) in the treatment of a gastric cancer peritoneal carcinomatosis mice modelBackground and Objective Gastric cancer is one of the most common malignant cancer in developing countries, and it’s likely to develop peritoneal carcinomatosis. Up to30%of gastric cancer patients have been developed peritoneal carcinomatosis at the time of diagnosis. Nearly60%of gastric cancer patients died from peritoneal carcinomatosis. Doxorubicin (DOX) is effective in gastric cancer treatment, however it has severe dose-dependent toxicities. A novel prodrug of DOX (Ac-Phe-Lys-PABC-DOX, PDOX) is designed by the authors to delivery free DOX relying on Cathepsin B (Cat B) and reduce side effects. In the current study, the authors examined the antitumor effect and toxicities of PDOX against gastric cancer peritoneal carcinomatosis.Methods SGC-7901gastric cancer cell line was used for the study. The in vitro study investigated the effects of DOX and PDOX on cell growth dynamics and cell colony-forming ability and cell cycle. The in vivo study investigated the efficacy and toxicity of PDOX on nude mice model of peritoneal carcinomatosis, with DOX as positive control. The status and weight of mice were recorded, and blood routine was monitored. At the end point or when the mouse was on the brink of death, mice were sacrificed, then serum was obtained for biochemical analysis, including ALT, AST, BUN, Cr, Ck, CK-MB and LDH. The lavage fluid of peritoneal cavity was also collected for apoptosis analysis.Results In the in vitro study, PDOX had a lower dose dependent inhibitory effect on SGC-7901cells than DOX. DOX inhibited the cell cycle and induced obviously a peak of apoptosis, while PDOX showed no apoptotic peak. In the in vivo study on control, DOX and PDOX groups, the median experimental peritoneal carcinomatosis indexes were6,1.5, and1, respectively (P=0.004); the body weights were24.32±1.40g,18.40±2.97g, and23.61±0.80g, respectively (P=0.000). Biochemical studies showed that PDOX had significantly lower toxicities on the bone marrow, liver, kidney and particularly the heart. Histopathological studies on control, DOX and PDOX groups found significant myocardium toxicities in3,7,4animals, respectively.Conclusions PDOX could be an effective molecular targeting drug to treat gastric cancer peritoneal carcinomatosis at present dosage without serious cardiac toxicities. PDOX is also a potential drug for other tumors that produces Cat B, with enhanced efficacy and reduced toxicity. Part II:Acute toxicity study of a novel prodrug of Doxorubicin (PDOX) in mice, administrated intraperitoneally and intravenouslyBackground and Objective Chemotherapy is an important part of comprehensive cancer treatment. Now clinical applications are mainly traditional chemotherapy drugs, such as Doxorubicin (DOX). Being lack of targeting ability, they always cause serious side effects. In order to reduce the cardiac toxicity of DOX, we design a prodrug of DOX, named PDOX (Ac-Phe-Lys-PABC-DOX). PDOX is stable in normal tissue, and will be specifically cleaved in tumor local-region by Cathepsin B (Cat B). Previous studies shown PDOX was effective in gastric cancer peritoneal carcinomatosis mice model, gastric cancer orthotopic xenograft mice model, hepatocellular cancer orthotopic xenograft mice model and gastric cancer peritoneal carcinomatosis rabbit model, with lower side effects than DOX. The purpose of this study was to investigate the acute toxicity of PDOX, and find out the most optimal dosing regimen and the maximally tolerated dose.Methods According to previous study and results reported in the literatures, PDOX acute toxicity study doses were designed. First, Kunming mice were divided into control group (vehicle), five PDOX groups (90.0mg/kg,112.0mg/kg,120.6mg/kg,130.0mg/kg and140.0mg/kg group),10mice per group (half male and half female), and used to evaluate the LD50of PDOX administrated intraperitoneally. The reaction to PDOX of mice and weight were recorded. When sacrificed, blood routine was tested, and then autopsy was done to research animal viscera index. To evaluate the LD5o of PDOX administrated intravenously, DOX was used as positive control group. Kunming mice were divided into control group, DOX group in different doses (15.0mg/kg,18.0mg/kg,21.6mg/kg,25.9mg/kg,31.1mg/kg) and PDOX group in different doses (47.1mg/kg,51.4mg/kg,56.0mg/kg,61.1mg/kg,66.7mg/kg),10mice per group (half male and half female). The reaction of animal and changes in body weight were observed, blood serum was collected for biochemical analysis. Animal viscera index and histopathology were also studied.Results The acute toxicity of PDOX mainly occurred in the acute phase, and it had little impact to recovery phase, while DOX had a continuous effect to mice last up to a week. PDOX reduced side effects on the status and weight significantly than DOX. The biochemical and histopathological study shown the same results, PDOX reduced cardiac and hepatic toxicities. The LD50of PDOX when given intraperitoneally and intravenously were129.61mg/kg and55.17mg/kg, respectively, and were5.45and1.37times higher than that of DOX, respectively.Conclusions Compared to DOX, the LD50of modified PDOX is increased, on contrast, side effects on important organs are decreased. PDOX has a certain dose-dependent toxicity, the main toxicities were acute lung disease. The optimal dosing regimen should be designed in the further long-term toxicity study.