Nanomedicines for pulmonary delivery (R. Vanbever)

Bruxelles Woluwe

The research aims at improving the treatment or prophylaxis of severe respiratory diseases by designing nanomedicines to enhance the local efficacy of drugs. Our approaches include i) the preparation of polyethylene glycol (PEG)-drug conjugates to sustain drug release within the lung, and ii) the formulation of nanocarriers to target vaccines to lung dendritic cells.

Inhalation aerosols offer a targeted therapy for respiratory diseases. However, the therapeutic efficacy of inhaled drugs is limited by their rapid clearance from the lung (Figure 1). 








Figure 1: Schematic view of the fate of drugs in the lungs (from Todoroff & Vanbever, Curr. Opin. Coll. Interf. Sc., 2011)

Anti-IL17 and anti-IL13 antibody fragments were conjugated to a large PEG chain and conjugation was shown to greatly prolonge the presence of these fragments within the lung of mice, rats and rabbits. The prolonged pulmonary residency of the anti-IL-17 PEG-F(ab’)2 translated into an improved efficacy in reducing lung inflammation in a murine model of house dust mite-induced lung inflammation. The molecular weight of PEG, the nature of the antibody fragment and the site of delivery within the respiratory tract had an impact on the residence time of antibody fragments in the murine lung. PEGylated proteins were principally retained within the lung lumen rather than the nasal cavities or lung parenchyma. PEG increased the pulmonary retention of antibody fragments through mucoadhesion, reduced uptake by alveolar macrophages and epithelial cells rather than increased hydrodynamic size or improved enzymatic stability. A PEGylated Fab’ antibody fragment and 40kDa PEG alone did not induce any lung toxicity following acute or chronic pulmonary administration of high doses in mice.

We have also applied this PEGylation strategy to recombinant human deoxyribonuclease I (rhDNase). rhDNase is the mucolytic agent most widely used for the treatment of respiratory disease in cystic fibrosis. However, rhDNase I is rapidly cleared from the lungs, which limits its therapeutic efficacy and implies frequent dosing. rhDNase was monoPEGylated on its N terminal residue and the conjugated enzyme preserved the full enzymatic activity of the native protein both on DNA solutions and cystic fibrosis sputa. PEGylated rhDNase was retained in the lungs for more than 15 days, compared to a few hours for unconjugated rhDNase. The sustained presence of PEGylated rhDNase in the lung presents interesting perspectives for the development of a long-acting rhDNase with a reduced therapy burden for patients with cystic fibrosis.

We developped liposomes for targeting vaccines to lung dendritic cells. Nanoliposomes were prepared with cationic lipids presenting immunostimulatory capacities. These formulations were shown to successfully co-encapsulate both antigenic peptides and adjuvants with high loading efficiency. Nanoliposomes encapsulating calcein as a tracer were mainly taken up by alveolar macrophages following delivery to the lungs in mice. Few dendritic cells took up the liposomes, and interstitial macrophages did not take up liposomal calcein more than they took up soluble calcein. Stimulation of the innate immune system using liposomal CpG strongly enhanced uptake of calcein liposomes by all phagocytes in the lungs.