Objective: Peritoneal disseminated ovarian and pancreatic cancers are the most difficult to be treated with conventional cytotoxic or molecular targeted drugs. The treatment option is very limited although an intraperitoneal (IP) paclitaxel has been available and shown to improve a prognosis in patients. Therefore, it is urgent to develop a new IP chemotherapeutic drug regulating the fast DNA synthesis in peritoneal disseminated tumors originated commonly from the ovary, pancreas and stomach. We have developed a unique RNAi molecule consisting of shRNA (55-mer) against TS and a cationic liposome (DFP-10825) and tested its anti-tumor activity and PK profile in peritoneal disseminated ascetic tumor models.

Methods: We developed luciferase gene-transfected ovarian cancer (SKOV3-luc) and pancreatic cancer (PANC-1-luc) models in mice. After IP injection of 5x106 cells, DFP-10825 containing 20 µg TS shRNA (20 mg/mouse) was administered in an IP route (q3d x 4) to the tumor-bearing mice. In combination therapy, paclitaxel (10 mg/kg) was also IP administered to SKOV3-luc model to which the treatment was performed in the same schedule. The anti-tumor effect was assessed by measuring luciferase activity and tumor volume. Furthermore, the TS expression level in both ascetic tumor cells and solid tumors was measured by conventional RT-PCR. For PK study with DFP-10825 (especially TS shRNA), total RNAs were isolated at various time points from ascetic tumor cells and disseminated SKOV3-luc solid tumor models treated with DFP-10825 and TS shRNA levels were determined by Stem-loop RT-PCR.

Results: IP DFP-10825 delivery significantly suppressed the growth of ascetic SKOV3-luc and PANC-1-luc tumor cells and extended the survival time of these tumor-bearing mice compared with that of control group. Combination with the IP paclitaxel augmented the efficacy of DFP-10825. After the IP administration, TS shRNA levels derived from DFP-10825 in ascetic fluid were maintained at nM range (0.7 - 4.3-nM) across 24 hours but not detected (below 5 pM) in the plasma, suggesting that TS shRNA be relatively stable in the peritoneal cavity to be able to exert its anti-tumor activity but not in blood. Also, TS expression (TS mRNA) in ascetic tumor cells was significantly suppressed, supporting the notion that the anti-tumor activity and host survival benefit by DFP-10825 in tumor-bearing mice are through MOA to knock down the TS level in tumors specifically.

Conclusion: IP administration of newly developed DFP-10825, the TS shRNA conjugated with cationic liposome is localized stably in the peritoneal cavity and provides a new effective treatment option to the intractable peritoneal disseminated ovarian and pancreatic cancers without any systemic adverse events.

Citation Format: Cheng Jin, Kenzo Iizuka, Kokoro Eshima, Masakazu Fukushima, Tatsuhiro Ishida, Cheng-Long Huang, Hiromi Wada, Kiyoshi Eshima. DFP-10825 IP delivery provides a new effective treatment option to peritoneal-disseminated cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2192. doi:10.1158/1538-7445.AM2017-2192