Design and in-vitro/in-vivo evaluation in colon cancer cells of targeted oxaliplatin liposomes to epidermal growth factor receptor by conjugation of different ligands

Abstract

The colorectal cancer (CRC) is one of the main cancers diagnosed in the first world. Oxaliplatin is currently in the first therapeutic line for metastatic CRC treatment. This drug presents a good tolerability and low toxicity in patients. However, it shows a high and irreversible binding to erythrocytes and plasma proteins leading to a low free drug. This active fraction is rapidly cleared from plasma by covalent binding to tissues and renal elimination. These characteristics provide a low antitumor efficacy to oxaliplatin in monotherapy. On the other hand, nanotechnology is a strategy that has proved to modulate the pharmacokinetic properties of several encapsulated drugs. In this field, liposomes, considered as a biocompatible particle system with low toxicity and dynamism, allow the encapsulation of different types of agents, including platinum derivatives. In the last few years advanced strategies in these kind of carriers have been applied. One of them consist in the coupling of several ligands on the surface of the liposome to target specific receptors or antigens expressed in the tumor cell. In this way, the Epidermal Growth Factor Receptor (EGFr) implicated in the cellular proliferation process, is one of the receptor over-expressed in CRC. To inhibit its activity, several approaches with biomolecules like monoclonal antibodies (mAb) are currently used in clinic. Cetuximab is a mAb combined with other chemotherapeutic drugs, as oxaliplatin in CRC treatment. Therefore, the aim of the work was the development of EGFr targeted oxaliplatin liposomes using Cetuximab or its Fab¿ fragment as specific ligands. Based on that objective, several types of lipids and methods were evaluated to finally select the Film method and the lipid composition HSCP:CH:DSPE-PEG2000, to develop oxaliplatin liposomes with adequate particle size, efficiency of encapsulation and stability in in-vitro studies. In addition, the in-vivo experiments showed a greater antitumor efficacy for liposomes than for the free oxaliplatin. In the second step, this liposomal formulation was conjugated with Cetuximab and Fab¿ using the conventional method for the coupling. The cell uptake of these targeted formulations in EGFr positive cell lines was higher than for non-targeted liposomes. The role of the receptor was evaluated by a pre-treatment with Cetuximab which caused its inhibition. In fact, the uptake was dramatically decreased, supporting the targeted receptor of these formulations. According to these results, the targeted formulations were able to reduce statistically the tumor growth of an EGFr positive cell line inoculated in mice, in comparison with non-targeted liposomes or the free drug. Between targeted liposomes, the greater efficacy was observed for Fab¿-formulation. In conclusion, EGFr targeted liposomes of oxaliplatin seem to be a promising strategy to improve the free drug activity.