A physiologically based pharmacokinetic and pharmacodynamic model for disposition of FF-10832.

This study aimed to quantitatively clarify the critical factors responsible for the superior antitumor efficacy of a liposomal gemcitabine (2,2-difluorodeoxycytidine; dFdC) formulation, FF-10832, compared with dFdC. The underlying hypothesis is the different exposure of tumors to its active metabolite, dFdC triphosphate (dFdCTP), between the two formulations. Therefore, physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) models for encapsulated and unencapsulated dFdC were constructed considering the tumor dFdCTP concentration as an index of antitumor activity. To estimate drug the parameters, the time profiles of encapsulated and unencapsulated dFdC in the blood and those of dFdC and dFdCTP in tumors were measured following the intravenous bolus administration of FF-10832 or dFdC. dFdC metabolism and transport in the liver S9 fraction and isolated hepatocytes, respectively, were experimentally determined. The tumor growth curve in a mouse xenograft model following the administration of FF10832 and dFdC was also used to construct the PD model. The sensitivity analysis of the PBPK/PD model revealed the critical factors affecting antitumor efficacy, which included the total and intratumor tissue uptake clearances for liposomal formulation and the cytidine deaminase and deoxycytidine deaminase activities in tumors. Thus, these parameters are potential biomarkers for predicting the efficacy of the liposomal formulation of dFdC.

A Liposomal Gemcitabine, FF-10832, Improves Plasma Stability, Tumor Targeting, and Antitumor Efficacy of Gemcitabine in Pancreatic Cancer Xenograft Models.

PURPOSE: The clinical application of gemcitabine (GEM) is limited by its pharmacokinetic properties. The aim of this study was to characterize the stability in circulating plasma, tumor targeting, and payload release of liposome-encapsulated GEM, FF-10832. METHODS: Antitumor activity was assessed in xenograft mouse models of human pancreatic cancer. The pharmacokinetics of GEM and its active metabolite dFdCTP were also evaluated. RESULTS: In mice with Capan-1 tumors, the dose-normalized areas under the curve (AUCs) after FF-10832 administration in plasma and tumor were 672 and 1047 times higher, respectively, than after using unencapsulated GEM. The tumor-to-bone marrow AUC ratio of dFdCTP was approximately eight times higher after FF-10832 administration than after GEM administration. These results indicated that liposomal encapsulation produced long-term stability in circulating plasma and tumor-selective targeting of GEM. In mice with Capan-1, SUIT-2, and BxPC-3 tumors, FF-10832 had better antitumor activity and tolerability than GEM. Internalization of FF-10832 in tumor-associated macrophages (TAMs) was revealed by flow cytometry and confocal laser scanning microscopy, and GEM was efficiently released from isolated macrophages of mice treated with FF-10832. These results suggest that TAMs are one of the potential reservoirs of GEM in tumors. CONCLUSION: This study found that FF-10832 had favorable pharmacokinetic properties. The liposomal formulation was more effective and tolerable than unencapsulated GEM in mouse xenograft tumor models. Hence, FF-10832 is a promising candidate for the treatment of pancreatic cancer.

FF-10832 enables long survival via effective gemcitabine accumulation in a lethal murine peritoneal dissemination model.

Chemotherapy has been the treatment of choice for unresectable peritoneal dissemination; however, it is difficult to eradicate such tumors because of poor drug delivery. To solve this issue, we developed FF-10832 as liposome-encapsulated gemcitabine to maintain a high concentration of gemcitabine in peritoneal tumors from the circulation and ascites. A syngeneic mouse model of peritoneal dissemination using murine Colon26 cell line was selected to compare the drug efficacy and pharmacokinetics of FF-10832 with those of gemcitabine. Despite the single intravenous administration, FF-10832 treatment enabled long-term survival of the lethal model mice as compared with those treated with gemcitabine. Pharmacokinetic analysis clarified that FF-10832 could achieve a more effective gemcitabine delivery to peritoneal tumors owing to better stability in the circulation and ascites. The novel liposome-encapsulated gemcitabine FF-10832 may be a curative therapeutic tool for cancer patients with unresectable peritoneal dissemination via the effective delivery of gemcitabine to target tumors.