Biopharmaceutical Evaluation of Intra-arterial Drug-Delivery Systems for Liver Cancer: Investigations in healthy pigs and liver cancer patients

There are currently two types of intra-arterial drug-delivery system (DDS) in clinical use in the palliative treatment of primary liver cancer. The chemotherapeutic drug doxorubicin (DOX) can be formulated into a drug-in-lipiodol emulsion (LIPDOX) or a microparticulate drug-eluting bead system (DEBDOX). To facilitate development of future DDSs, we need to understand the release and local distribution of drug from these DDSs into the complex, in vivo, pathological environment. The overall aim of this project was to assess and improve understanding of the in vivo release of DOX from LIPDOX and DEBDOX and its local disposition in the liver. These processes were investigated in detail in a multisampling-site, healthy pig model and in human patients with liver cancer. The mechanisms involved in DOX disposition were studied by examining potential interactions between DOX and lipiodol and/or cyclosporine A (CsA) in pigs. In this project, the main elimination pathway for DOX and its primary metabolite doxorubicinol (DOXol) was via bile; their extensive canalicular carrier-mediated transport (e.g. ATP-binding cassette transporters ABCB1, ABCC1, ABCC2 and ABCG2) was inhibited by CsA. CsA had no effect on the carbonyl and aldo-keto reductases responsible for the metabolism of DOX into DOXol. LIPDOX released DOX more rapidly and to a greater extent into the circulation than DEBDOX, which had only released 15% of the dose in patients after 24 hrs. The systemic exposure to DOX was lower for DEBDOX than for LIPDOX. Greater fractions of DOXol were formed in blood and bile with LIPDOX than with DEBDOX. This may have been because DOX was more widely distributed into regions with increased metabolic capacity or because of increased intracellular uptake when DOX was delivered in LIPDOX. The excipient lipiodol in the LIPDOX formulation did not interact with transporters, enzymes or membranes that would explain the increased cellular uptake of DOX. In conclusion, the release of DOX from DEBDOX is more controlled in vivo than that from LIPDOX, indicating that DEBDOX is a more robust pharmaceutical product. The formulations for future optimized DDSs should therefore be more similar to DEBDOX than to LIPDOX.