O-P05 Gemcitabine and paclitaxel loaded microbubbles for the treatment of pancreatic cancer

Abstract

Abstract Background Ultrasound targeted microbubble destruction (UTMD) has emerged as an effective strategy for the delivery of drug payloads to solid tumours. However, loading a single microbubble (MB) formulation with two drug payloads is challenging and often involves several manipulations post-MB preparation to enable attachment of drug payloads which can be cumbersome and generally results in low / inconsistent drug loading. Here we report a one-step synthesis of a gemcitabine-functionalised phospholipid and its subsequent incorporation into a stable MB formulation co-loaded with paclitaxel (PTX). The efficacy of the MB conjugate was determined in a Panc-1 spheroid model and ectopic BxPC-3 tumour model of pancreatic cancer. Methods Gemcitabine-modified phospholipid (Lipid-Gem MB) was prepared from 1,2-dibehenoyl-sn-glycero-3-phosphocholine (DBPC) though a transphosphatidylation reaction using gemcitabine (Gem) as the acceptor alcohol. Lipid-Gem MB and Lipid-Gem-PTX MB were prepared from Lipid-Gem MB and/or PTX using a standard thin-film hydration technique followed by sonication in the presence of PFB gas. In vitro efficacy of Lipid-Gem MB and Lipid-Gem-PTX MB were determined in Panc-1 spheroids using an MTT assay. The in vivo effectiveness was determined in BxPC-3 tumour bearing mice following IV administration of either Lipid-Gem MB or Lipid-Gem-PTX MB plus ultrasound (US). Free Gem, free Gem + PTX and untreated mice were used for comparative purposes. Results Spheroids treated with Lipid-Gem MB +US or Lipid-Gem-PTX MB +US were significantly reduced relative to spheroids treated with US alone (p = 0.033 and p = 0.0031 respectively) or with the respective MB formulation alone (i.e. no US) (p = 0.0336 and p = 0.0037 respectively). Furthermore, cell viability for spheroids treated with Lipid-Gem-PTX MB +US was significantly reduced compared with spheroids treated with Lipid-Gem MB +US (p = 0.0077) (Figure a). Mice treated with Lipid-Gem MB +US or Lipid-Gem-PTX MB +US showed an average change in tumour volume of + 7 ± 7% and -10 ± 10 % respectively compared with +45 ±10% and +30 ± 10% for free gem and free gem + PTX respectively (Figure b). Conclusions A Gem-modified lipid was succesfully synthesised using a single step reaction and was subsequently incorporated into MBs containging PTX, eliminating the need for cumbersome drug conjgation methods. UTMD mediated treatment of Panc-1 spheroids and BxPC-3 tumours demonstrated the efficacy and tolerability of the formulations. Given that all components of this formulation are already clinicaly apporved, UTMD using Lipid-Gem-PTX MB offers a promising alternative to existing treatments