Dan Smith

Hollow porous particles in metered dose inhalers

AbstractPurpose. To assess the physical stability and aerosol characteristicsof suspensions of hollow porous microspheres (PulmoSpheres™) inHFA-134a. Methods. Cromolyn sodium, albuterol sulfate, and formoterol fumaratemicrospheres were prepared by a spray-drying method. Particle sizeand morphology were determined via electron microscopy. Particleaggregation and suspension creaming times were assessed visually,and aerosol performance was determined via Andersen cascadeimpaction and dose uniformity studies. Results. The hollow porous particle morphology allows the propellantto permeate freely within the particles creating a novel form ofsuspension termed a homodispersion™, wherein the dispersed and continuousphases are identical, separated by an insoluble interfacial layer of drugand excipient. Homodispersion formation improves suspension stabilityby minimizing the difference in density between the particles andthe medium, and by reducing attractive forces between particles. Theimproved physical stability leads to excellent dose uniformity. Excellentaerosolization efficiencies are also observed with PulmoSpheresformulations, with fine particle fractions of about 70%. Conclusions. The formation of hollow porous particles provides anew formulation technology for stabilizing suspensions of drugs inhydrofluoroalkane propellants with improved physical stability, contentuniformity, and aerosolization efficiency.

Novel lipid-based hollow-porous microparticles as a platform for immunoglobulin delivery to the respiratory tract.

AbstractPurpose. Delivery of specific antibodies or immunoglobulin constructsto the respiratory tract may be useful for prophylaxis or active treatmentof local or systemic disorders. Therefore, we evaluated the utilityof lipid-based hollow-porous microparticles (PulmoSpheres™) as apotential delivery vehicle for immunoglobulins. Methods. Lipid-based microparticles loaded with humanimmunoglobulin (hIgG) or control peptide were synthesized by spray drying and testedfor: i) the kinetics of peptide/protein release, using ELISA and bioassays;ii) bioavailability subsequent to nonaqueous liquid instillation into therespiratory tract of BALB/c mice, using ELISA and Western blotting;iii) bioactivity in terms of murine immune response to xenotypic epitopeson human IgG, using ELISA and T cell assays; and iv) mechanismsresponsible for the observed enhancement of immune responses, usingmeasurement of antibodies as well as tagged probes. Results. Human IgG and the control peptide were both readily releasedfrom the hollow-porous microspheres once added to an aqueousenvironment, although the kinetics depended on the compound. Nonaqueousliquid instillation of hIgG formulated in PulmoSpheres into the upperand lower respiratory tract of BALB/c mice resulted in systemicbiodistribution. The formulated human IgG triggered enhanced local andsystemic immune responses against xenotypic epitopes and wasassociated with receptor-mediated loading of alveolar macrophages. Conclusions. Formulation of immunoglobulins in hollow-porousmicroparticles is compatible with local and systemic delivery via therespiratory mucosa and may be used as means to trigger or modulateimmune responses.

Receptor-mediated targeting of spray-dried lipid particles coformulated with immunoglobulin and loaded with a prototype vaccine.

AbstractPurpose. Spray-dried lipid-based microparticles (SDLM) serve as a platform for delivery of a wide variety of compounds including peptides, proteins, and vaccines to the respiratory mucosa. In the present study, we assessed the impact of IgG-mediated targeting to phagocytic cells of inactivated influenza virus formulated in SDLM, on subsequent immune responses. Methods. SDLM were produced containing inactivated influenza virus strain A/WSN/32/H1N1 (WSN), with or without IgG. Using phagocytic antigen presenting cells (APC) and a T cell hybridoma (TcH) line specific for a dominant influenza virus epitope, we compared the in vitro responses elicited by ligand-formulated (SDLM-IgG-WSN) and non-ligand particles (SDLM-WSN). The effect of including the IgG ligand in the formulation was further characterized by measuring the immune responses of rodents vaccinated with SDLM. Results. SDLM-IgG-WSN were internalized in an Fc receptor (FcR)-dependent manner by phagocytic APC that were then able to effectively present a dominant, class II-restricted epitope to specific T cells. While SDLM-WSN elicited a lower response than administration of plain inactivated virus in saline, the level of the T cell response was restored both in vitro and in vivo by incorporating the APC FcR ligand, IgG, in the SDLM. Conclusions. Incorporation of FcR ligand (IgG) in SDLM restored the limited ability of formulated virus to elicit T-cell immunity, by receptor-mediated targeting to phagocytes.

Fc Receptor Targeting With Recombinant Immunoglobulins and Immunoglobulin Formulations

Manipulation of immunity for the purpose of controlling pathogenic responses or prevent diseases such as infections can be achieved by two different approaches: (1) an antigen- or epitope-based strategy, designed to influence the immune system by interaction with lymphocytes that express only receptors specific for such antigens (e.g., vaccines); or (2) the use of agents that decrease or increase immunity by acting via nonantigen specific receptors on lymphocytes (e.g., immune-suppressive drugs for the treatment of autoimmune diseases or immune stimulatory cytokines in cancer). Advances during the last two decades in particular have resulted in the understanding that noninfectious diseases such as autoimmunity and certain cancers can be influenced in a manner depending on antigen-specific recognition. This finding, combined with advances in target discovery and validation catalyzed by the elucidation of the human genetic map, has resulted in an unprecedented world-wide effort in designing safer drugs or therapeutic strategies that give the concept of vaccination a new meaning.