5.58 Advances in the Use of Targeted Nanoparticles for the Treatment of B-CLL

Objective: To demonstrate the therapeutic effect of chlorambucil and hydroxichloroquine (CLB/HCQ) as well as Vorinostat and PEITC (V/PEITC) loaded biological nanoparticles (BNPs) coated with the anti-CD20 monoclonal antibody Rituximab targeted to B-CLL cells. Materials and methods: We produced four types of BNPs: BNP0, empty PLGA nanoparticles without a drug or monoclonal antibody; BNP1, Rituximab-coated but without drugs; BNP2, CLB/HCQ-loaded and Rituximab coated; and BNP3, V/PEITC-loaded and Rituximab coated. To evaluate the cytotoxic effect of BNPs, B-CLL cells obtained from 10 B-CLL patients were incubated with defined amounts of all types of BNPs, measuring residual viable cells after 48 hours. The cytotoxic effect of BNPs was also tested on CD20-negative CHO, HUVEC, MEL-28 and IGROV1 cells incubated with BNPs (2 l at 0.9mg/ml of polymer). Results: BNP2 was able to induce cell cytotoxicity in in a dosedependent manner, while BNP0 and BNP1 were almost ineffective. Ninety five percent of tumor cells from all patients were killed using only 2 l of BNP2 at 0.9mg/ml of polymer and containing 5.4 g of CLB/HCQ. The same amount of free cytotoxic agents induced an approx 80% kill rate. No specific cell cytotoxicity was measured using BNP0 and 1 in non-CD20 cells. BNP2 was effective in CHO and melanoma treated cells, but values never exceeded 20% of killing. B-CLL cells with the lowest expression levels of CD20 were killed by BNP2 at about 82%. V/PEITC BNP3 had similar effects to BNP2, but when tested with the lowest CD20 expressing cells the killing effect was around 95%. Discussion: BNPs seem to be a novel and effective strategy to treat B-CLL. CD20 expressed on cell surface seems to be the limiting factor for the binding of a sufficient amount of Rituximab for the activation of all the effector systems. This antibody limitation seems not to be the case for our BNPs. Both CLB/ HCQ and V/PEITC BNPs had a significant killing effect on B-CLL cells independent of the concentration of CD20 on cell surfaces. This was especially noticeable with V/PEITC nanoparticles. This last combination of drugs is a very interesting for use in B-CLL. Its delivery inside biodegradable nanoparticles could provide a new therapeutic option in the near future.