Distinct ß-sheet structure in protein aggregates determined by ATR-FTIR spectroscopy.

Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to study the conformation of aggregated proteins in vivo and in vitro. Several different protein aggregates, including amyloid fibrils from several peptides and polypeptides, inclusion bodies, folding aggregates, soluble oligomers, and protein extracts from stressed cells, were examined in this study. All protein aggregates demonstrate a characteristic new ß structure with lower-frequency band positions. All protein aggregates acquire this new ß band following the aggregation process involving intermolecular interactions. The ß sheets in some proteins arise from regions of the polypeptide that are helical or non ß in the native conformation. For a given protein, all types of the aggregates (e.g., inclusion bodies, folding aggregates, and thermal aggregates) showed similar spectra, indicating that they arose from a common partially folded species. All of the aggregates have some nativelike secondary structure and nonperiodic structure as well as the specific new ß structure. The new ß could be most likely attributed to stronger hydrogen bonds in the intermolecular ß-sheet structure present in the protein aggregates.

Mechanisms and consequences of protein aggregation: the role of folding intermediates.

Protein aggregation, being one of the hottest topics of modern protein science, is recognized now as a serious biomedical and biotechnological problem. Protein aggregation is considered as a causative factor (or at least an associated symptom) of a wide spectrum of human pathologies. Furthermore, aggregation and precipitation are known to trammel recombinant protein production, as well as to affect the manufacture, storage and delivery of proteinaceous drugs. Therefore, this topic attracts the serious attention of many researchers, a conclusion that follows from the average daily publication of 7-8 scientific papers dedicated to the various aspects of protein aggregation. However, the situation was rather different 15-20 years ago when it was believed that the formation of protein aggregates causing the irreversibility of unfolding or denaturation of some proteins was nothing more than an annoying experimental artifact, hampering the detailed characterization of the unfolding/denaturation processes. At that time, only a few laboratories (including the laboratory of Prof. Anthony L. Fink) seriously worked on understanding the molecular mechanisms of this "artifact". In this review, we summarize some of the early work of Tony Fink on aggregation, of protein folding intermediates and on the analysis of the structural consequences of this process.

The design and performance of the exubera pulmonary insulin delivery system.

The Exubera system (Pfizer, New York, NY/Nektar Therapeutics, San Carlos, CA) is an integration of five major new technologies: protein formulation, powder processing, powder filling, drug packaging, and delivery device. The product provides a simple interface, where the patient interacts only with the delivery device and powder packaging. These components were designed together to assure repeatable dosing when used by a wide range of patients under real-world life-style and handling conditions. The device design is purely mechanical, using patient-generated compressed air as the energy source. Upon actuation, a sonic discharge of air through the novel release unit reproducibly extracts, de-agglomerates, and disperses the inhalation powder into a respirable aerosol. A clear holding chamber allows for patient feedback via dose visualization and separates aerosol cloud generation from the inspiratory effort. The Exubera product was tested under a wide range of typical use conditions and potential misuse scenarios and following long-term usage in clinical trials. These comprehensive characterization programs demonstrated robust aerosol and mechanical performance, confirming the design intent of the inhaler. These studies provide assurance of consistent and reliable dose delivery in a real-world use of the product.

EXUBERA: pharmaceutical development of a novel product for pulmonary delivery of insulin.

Development of a product for pulmonary delivery of insulin presented significant technology challenges for this first-in-class pharmaceutical product. These included developing (a) a chemically stabilized protein, (b) a dry powder formulation exhibiting required aerosol physical characteristics, (c) low-dose powder filling and packaging technology, and (d) a mechanical device for powder dispersal and reliable dosing to the patient. The insulin drug is formulated using a novel excipient combination to create a powder with a high glass transition temperature (Tg). The high Tg minimizes insulin mobility (thus reactivity), enabling ambient storage conditions. The formulation composition results in minimal hygroscopicity, where customized packaging produced product ruggedness to humidity. The formulated insulin powder is manufactured by spray-drying. This technology was further engineered to produce the desired reproducible powder characteristics with tight control over particle size and moisture content. A solution step prior to drying assures homogeneity and minimizes dependence on the physical form of the components. Novel low-dose filling and packaging technology reproducibly meters milligram quantities of microfine powder to meet stringent quality requirements for dose control. The technology for accurate, uniform, high-throughput metering of drug powders allows for automation and is scaleable for commercial operations. Finally, the mechanical device design provides powder deagglomeration and dispersion processes in a reusable dry powder inhaler with unique characteristics. The device was designed to rely on patient-generated compressed air as the energy source. A sonic discharge of air through the novel TransJector reproducibly extracts, deagglomerates, and disperses the inhalation powder. A clear holding (spacer-type) chamber allows for patient feedback via dose visualization, and separates powder dispersal from the inspiratory effort. The EXUBERA [Pfizer (New York, NY) and sanofi-aventis (Paris, France)] product provides insulin into the bloodstream with similar reproducibly and effectiveness as subcutaneous injections.