Aerosol delivery of DNA/liposomes to the lung for cystic fibrosis gene therapy

Lung gene therapy is being evaluated for a range of acute and chronic diseases including cystic fibrosis (CF). As these therapies approach clinical realisation it is becoming increasingly clear that the ability to efficiently deliver gene transfer agents (GTAs) to target cell populations within the lung may prove just as critical as the gene therapy formulation itself in terms of generating positive clinical outcomes. Key to the success of any aerosol gene therapy is the interaction between the GTA and nebulisation device. We evaluated the effects of aerosolisation on our preferred formulation, plasmid DNA (pDNA) complexed with the cationic liposome GL67A (pDNA/GL67A) using commercially available nebuliser devices. The relatively high viscosity (6.3 ± 0.1 cP) and particulate nature of pDNA/GL67A formulations hindered stable aerosol generation in ultrasonic and vibrating mesh nebulisers, but was not problematic in the jet nebulisers tested. Aerosol size characteristics varied significantly between devices but the AeroEclipse II nebuliser operating at 50 psi generated stable pDNA/GL67A aerosols suitable for delivery to the CF lung (MMAD 3.4 ± 0.1 µm). Importantly, biological function of pDNA/GL67A formulations was retained following nebulisation and although aerosol delivery rate was lower than other devices (0.17 ± 0.01 ml/min) the breath-actuated AeroEclipse II nebuliser generated aerosol only during the inspiratory phase and as such was more efficient than other devices with 83 ± 3% of generated aerosol available for patient inhalation. Based on these results we have selected the AeroEclipse II nebuliser for the delivery of pDNA/GL67A formulations to the lungs of CF patients as part of Phase IIa/b clinical studies.