Propellant-driven aerosols for delivery of proteins in the respiratory tract

Carrier-based strategies for targeting protein and peptide drugs to the lungs

With greater interest in delivery of protein and peptide-based drugs to the lungs for topical and systemic activity, a range of new devices and formulations are being investigated. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of protein/peptide drugs by inhalation using carriers and ligands.

Innovations and perspectives of metered dose inhalers in pulmonary drug delivery

The phase-out of chlorofluorocarbons (CFCs) has spurred the development of alternative pulmonary drug delivery systems to pressurized metered dose inhalers (MDIs), such as dry powder inhalers and pocket size nebulizers. Reformulation of CFC-MDIs with hydrofluoroalkanes (HFAs) 134a and 227 is also an opportunity to improve these widely accepted systems with respect to ease of handling, compliance, dosing, and more reliable and efficient lung deposition. MDIs have the advantage to protect the drug substance from external parameters such as temperature and humidity and to meter and de-agglomerate the drug independent from patients inspiratory flow rates. Novel formulation technologies combined with improved valves and actuators should help to overcome dose uniformity and priming problems and will increase the percentage of fine particles capable of reaching the deeper regions of the lungs. Spacer mouthpieces can reduce the cold freon effect and undesired oropharyngeal deposition caused by the rapid evaporation of the propellant and plume velocity of the aerosol cloud. More advanced delivery devices may allow the patient to inhale at predetermined flow rates (fast/slow) to target the deposition of fine drug particles (1-6 microm) to specific sites into the lungs. Breath-actuated devices make these systems more effective and patient friendly. The above features in combination with numerical counters showing the remaining number of shots, and built-in blocking mechanisms to avoid tail-off dependent dose uniformity problems of the last labeled shots, should help to improve both acceptance and compliance of pMDIs compared to other inhalation devices. However, only those inhalation systems, which are accepted and appreciated by patients and offering an ambulatory treatment at reasonable cost, will be successful in a more and more competitive market. These issues must be considered in the development of future devices and formulations.

Formulation of a protein with propellant HFA 134a for aerosol delivery

The purpose of this study was to investigate the formulation and delivery of a protein in a pressurized metered-dose inhaler (pMDI) containing HFA 134a as the propellant for aerosol delivery. Ethanol and surfactants, including polyoxyethylene 10 oleyl ether (Brij 97), polyoxyethylene 20 oleyl ether (Brij 98), polyoxyethylene sorbitan monooleate (Tween 80) and Aerosol OT (AOT), were investigated as formulation adjuvants to improve the dose delivery characteristics of the model protein (bovine serum albumin) containing pMDI formulations. The aqueous solution of a surfactant and protein was lyophilized to obtain a solid carrier system of the protein. Readily dispersible suspensions were obtained by suspending this solid carrier system in HFA 134a with ethanol as a dispersing aid. The formulations containing Tween 80 resulted in the highest respirable fraction. This study suggested a potential formulation containing a lyophilized complex of surfactant and protein readily dispersible in HFA 134a for delivering a therapeutic protein to the respiratory tract by inhalation.

Tetrafluoroethane (HFC 134A) propellant-driven aerosols of proteins

PURPOSE

Develop metered-dose propellant-driven aerosols of proteins using tetrafluoroethane (HFC 134A) as propellant.

METHODS

Proteins were lyophilized with the propellant-soluble surfactants Triton X-100, Triton X-405, Laureth-9, Brij-30, Nonidet-40, and diethylene glycol monoethylether and then charged with propellants.

RESULTS

Small particle aerosols of the experimental protein bovine gamma globulin were produced. The fraction of aerosolized respirable-sized protein particles (< 4-5 microns) increased after dispersion of particles in propellant with agitation by shaking. Scanning electron microscopy of respirable-sized protein aerosols demonstrated bead-like particles in grape-like clusters. Vigorous shaking of propellant-suspended particles for 2 minutes or more reduced the size of clusters and reduced the diameters of the protein-containing subparticles that constituted the clusters. A 50:50 ratio of HFC 134A and dimethylether (DME) propellants improved the respirability of protein aerosols compared to HFC 134A as the sole propellant. Protein/surfactant particles first dispersed in DME and then diluted in HFC 134A propellant most efficiently produced respirable-sized, propellant-driven, protein aerosols.

Aerosol bolus dispersion and aerosol-derived airway morphometry: assessment of lung pathology and response to therapy, Part 1

review discusses the potential utility of two methods using inhaled aerosols to detect and diagnose lung disease and to evaluate the efficacy of therapy. Aerosol bolus dispersion measures convective gas mixing; aerosol-derived airway morphometry assesses the calibers of airway and airspaces. These two methods are discussed in terms of their ease of use (simplicity and acceptability) and current data regarding their validity, reproducibility, specificity, sensitivity, and detection of lung improvement with therapy. Part 1 of this review focuses upon aerosol bolus dispersion; Part 2(1) focuses upon aerosol-derived airway morphometry. Aerosol bolus dispersion has many features that make it clinically attractive. It is simple to administer and patients can successfully perform the maneuvers. It detects known alterations in the lungs. It is reproducible and has high specificity and sensitivity. However, every lung disease or condition known to be detected by aerosol bolus dispersion is also detected by spirometery, maximal expiratory flow-volume curves, or another conventional lung function test. This, aerosol bolus dispersion appears best reserved as a specialized method to supplement conventional lung function tests and to characterize convective gas transport.