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 liposomes 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 in the lung (Figure 1). We synthesized PEG-paclitaxel ester conjugates with the aim to achieve sustained release of paclitaxel in the lung. These conjugates were characterized physicochemically and showed good stability in phosphate buffer and in bronchoalveolar lavage, but hydrolyzed quickly in mouse serum. The conjugates showed cytotoxicity to B16-F10 melanoma cells and Lewis lung carcinoma cells but less than Taxol, which is the commercial paclitaxel solution. The conjugates will be further investigated in vivo on B16-F10 lung metastasis mouse model to test the sustained drug release as well as the anti-tumor efficacy.
Figure 1: Schematic view of the fate of drugs in the lungs (from Todoroff & Vanbever, Curr. Opin. Coll. Interf. Sc., 2011)
Anti-IL17 F(ab’)2 and anti-IL13 Fab’ antibody fragments were conjugated to a large PEG chain and conjugation was shown to greatly prolonged the presence of these fragments within the lungs of mice. 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. PEGylated proteins were principally retained within the lung lumen rather than the nasal cavities or lung parenchyma. PEG increased pulmonary retention of antibody fragments through mucoadhesion and escape from alveolar macrophages rather than increased hydrodynamic size or improved enzymatic stability.
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 the N terminal residue and the conjugated enzyme preserved the full enzymatic activity of the native protein. PEGylated rhDNase was retained in the lungs for more than 10 days, compared to a few hours for unconjugated rhDNase.
We develop 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. Their sizes were comprised between 150 and 180 nm and a sustained release of antigens from the nanoliposomes over several hours was obtained. The fate of liposomes-encapsulated peptides in the respiratory tract is currently studied and the protection these formulations afford is currently assessed in vivo in murine models.