Alquil-lysophospholipids and cancer: development of lipid nanoparticles for oral administration and preclinical studies

Current leukemia treatments are generally associated to severe side-effects and relapse is frequent in adults. Edelfosine (ET) is the prototype of a family of antitumor drugs with potent antitumor effects against several cancer types. However, the use of ET in clinic remains limited due to ET side-effects. Nanomedicine has achieved great success in the medicine field and lipid nanoparticles (LN) have been widely used in cancer due to their benefits in therapy. The present work hypothesized that edelfosine lipid nanoparticles (ET-LN) might be an effective therapy against leukemia. The in vitro studies in leukemia cells showed that the antitumor effect of the drug is preserved after its encapsulation into LN. Moreover, ET-LN were able to overcome drug resistance in case of resistant cells (K-562). Endocytosis studies revealed that ET and ET-LN are internalized by different uptake mechanisms in sensitive and resistant cells. Studies of molecular mechanisms implicated in cell death showed that ET and ET-LN promoted similar caspase-mediated apoptosis cell death in sensitive HL-60 cells, whereas the induction of this cell death mechanism was not observed in resistant K-562 cells. In this cell line, ET and ET-LN endorsed a high induction of autophagic vesicles. As the induction of autophagy was demonstrated for both treatments, it is not possible to directly correlate K-562 sensitivity to ET-LN with autophagy cell death. As these nanosystems are designed for oral delivery, the next step of this work aimed to evaluate the intestinal absorption of ET and ET-LN after oral administration. Surprisingly, these results evidenced a likely metabolic process of ET in enterocytes. In case of ET-LN, ET might be protected from this metabolic process when it is encapsulated into LN. Besides, the developed Caco-2/Raji co-culture model did not show translocation of ET-LN from the apical to the basal compartment. At this point, these results could be explained as the limitations of in vitro experiments to describe drugs in vivo behaviours. Afterwards, and bearing in mind the toxicity of antitumor drugs, we aimed to confirm the benefits that LN might provide in the toxicological profile of ET. Results confirm that LN provide a protective effect against the toxicity of the free drug, as LN prevented from the severe acute toxicity of higher dose of ET. These results were very interesting because they demonstrate not only that ET-LN are safe even at high doses but also that LN are a safe vehicle and could allow the administration of other antitumor agents by the oral route. Finally, a preliminary efficacy study was performed in a xenogeneic mouse model of human acute lymphoblastic leukemia. Radiolabeling studies led to the conclusion that intraperitoneal (i.p.) route might be more adequate to administer ET-LN that intravenous route. Efficacy studies were performed by i.p. route. Animals were administered a dose that is considered safe by the oral route but that showed to be toxic for the animals treated with ET, and ET-LN. Nevertheless, efficacy studies were encouraging as both ET and ET-LN were able to decrease percentage of human leukemia cells in mice with respect to control group. To conclude, the general hypothesis of the work has been confirmed as in vitro results in leukemia cells showed similar o greater efficacy of the ET-LN over the free drug. Besides, even in the case of similar efficacy, LN would offer advantages over the free drug in terms of protection against ET toxicity. Indeed, toxicity studies demonstrated that LN are a safe vehicle for the administration of antitumor agents by the oral route. Finally, in vivo efficacy studies showed promising preliminary results.