Stability of protein pharmaceuticals

Intermolecular interactions and conformation of antibody dimers present in IgG1 biopharmaceuticals

Intermolecular interactions and conformation in dimer species of Palivizumab, a monoclonal antibody (IgG1), were investigated to elucidate the physical and chemical properties of the dimerized antibody. Palivizumab solution contains ∼1% dimer and 99% monomer. The dimer species was isolated by size-exclusion chromatography and analysed by a number of methods including analytical ultracentrifugation-sedimantetion velocity (AUC-SV). AUC-SV in the presence of sodium dodecyl sulphate indicated that approximately half of the dimer fraction was non-covalently associated, whereas the other half was dimerized by covalent bond. Disulphide bond and dityrosine formation were likely to be involved in the covalent dimerization. Limited proteolysis of the isolated dimer by Lys-C and mass spectrometry for the resultant products indicated that the dimer species were formed by Fab-Fc or Fab-Fab interactions, whereas Fc-Fc interactions were not found. It is thus likely that the dimerization occurs mainly via the Fab region. With regard to the conformation of the dimer species, the secondary and tertiary structures were shown to be almost identical to those of the monomer. Furthermore, the thermal stability turned out also to be very similar between the dimer and monomer.

Stabilization of a recombinant ricin toxin A subunit vaccine through lyophilization

Lyophilization was used to prepare dry, glassy solid vaccine formulations of recombinant ricin toxin A-chain containing suspensions of colloidal aluminum hydroxide adjuvant. Four lyophilized formulations were prepared by using combinations of rapid or slow cooling during lyophilization and one of two buffers, histidine or ammonium acetate. Trehalose was used as the stabilizing excipient. Aggregation of the colloidal aluminum hydroxide suspension was reduced in formulations processed with a rapid cooling rate. Aluminum hydroxide particle size distributions, glass transition temperatures, water contents, and immunogenicities of lyophilized vaccines were independent of incubation time at 40 °C for up to 15 weeks. Mice immunized with reconstituted ricin toxin subunit A (RTA) vaccines produced RTA-specific antibodies and toxin-neutralizing antibodies (TNAs) regardless of the length of high temperature vaccine storage or the degree of aluminum adjuvant aggregation that occurred during lyophilization. In murine studies, lyophilized formulations of vaccines conferred protection against exposure to lethal doses of ricin, even after the lyophilized formulations had been stored at 40 °C for 4 weeks. A corresponding liquid formulation of vaccine stored at 40 °C elicited RTA-specific antibody titers but failed to confer immunity during a ricin challenge.

Effect of small molecule osmolytes on the self-assembly and functionality of globular protein-polymer diblock copolymers

Blending the small molecule osmolytes glycerol and trehalose with the model globular protein-polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) (mCherry-b-PNIPAM) is demonstrated to improve protein functionality in self-assembled nanostructures. The incorporation of either additive into block copolymers results in functionality retention in the solid state of 80 and 100% for PNIPAM volume fractions of 40 and 55%, respectively. This represents a large improvement over the 50-60% functionality observed in the absence of any additive. Furthermore, glycerol decreases the thermal stability of block copolymer films by 15-20 °C, while trehalose results in an improvement in the thermal stability by 15-20 °C. These results suggest that hydrogen bond replacement is responsible for the retention of protein function but suppression or enhancement of thermal motion based on the glass transition of the osmolyte primarily determines thermal stability. While both osmolytes are observed to have a disordering effect on the nanostructure morphology with increasing concentration, this effect is less pronounced in materials with a larger polymer volume fraction. Glycerol preferentially localizes in the protein domains and swells the nanostructures, inducing disordering or a change in morphology depending on the PNIPAM coil fraction. In contrast, trehalose is observed to macrophase separate from the block copolymer, which results in nanodomains becoming more disordered without changing significantly in size.

In vitro and in vivo epidermal growth factor gene therapy for diabetic ulcers with electrospun fibrous meshes

Human epidermal growth factor (hEGF) gene therapy was achieved with an electrospun nanofibrous mesh with matrix metalloproteinase (MMP) responsiveness to control release of plasmid human epidermal growth factor (phEGF) in diabetic ulcers. For MMP responsiveness, linear poly(ethyleneimine) (LPEI) was immobilized on the surface of the nanofiber via an MMP-cleavable linker. phEGF was electrostatically incorporated into LPEI-immobilized nanofibrous meshes with various charge ratios and phEGF incorporation efficiency was increased with increasing charge ratios. The release of both phEGF and LPEI was significantly increased in the presence of MMP-2 due to the enzymatic digestion of the MMP-cleavable linkage between the matrix and LPEI. Human dermal fibroblasts with the released fraction showed a higher expression level of hEGF compared to naked phEGF or phEGF/LPEI complexes. Diabetic wounds treated with phEGF-incorporated nanofibrous meshes showed high hEGF expression level and accelerated wound recovery rates without wound contractions for 14days. Neocollagen and cytokeratin accumulation were significantly increased as well as the expression of the keratinocyte-specific markers at the re-epithelized tissue treated with phEGF nanofibrous meshes, which clearly indicates that EGF gene was transfected to dermal cells and this consequently assisted wound recovery without phenotypic changes of the re-epithelized tissues. Thus, phEGF-incorporated nanofibrous mesh is expected to accelerate the wound-healing process as well as reduce wound contraction during recovery from diabetic ulcers.

In situ spectroscopic quantification of protein-ice interactions

FTIR and confocal Raman microspectroscopy were used to measure interactions between albumin and ice in situ during quasi-equilibrium freezing in dimethyl sulfoxide (DMSO) solutions. At temperatures of -4 and -6 °C, albumin was found to be preferentially excluded from the ice phase during near-equilibrium freezing. This behavior reversed at lower temperatures. Instead, DMSO was preferentially excluded from the ice phase, resulting in an albumin concentration in the freeze-concentrated liquid phase that was lower than predicted. It is hypothesized that this was caused by the albumin in the freeze-concentrated liquid getting adsorbed onto the ice surface or becoming entrapped in the ice phase. It was observed that, under certain freezing protocols, as much as 20% of the albumin in solutions with starting concentrations of 32-53 mg/mL may be adsorbed onto the ice interface or entrapped in the ice phase.

Strategies for enhanced peptide and protein delivery

Recent advances in the fields of molecular biology and biotechnology have allowed for the large-scale production and subsequent exploitation of the therapeutic potential of protein- and peptide-based drugs. The facilitation of delivery of this class of drugs must be tailored to meet the requirements and often the limitations dictated by the route of delivery chosen. The aim of this review is to comprehensively discuss several routes of drug delivery, detailing the uses and exploitation of each, from origins to present day approaches. Specific reference is made to the compatibility or incompatibility of each approach in the facilitation of the delivery of drugs of protein origin. Additionally, the physiological nature of the delivery route and the inherent physiological obstacles that must be considered when determining the most suitable approach to drug design and delivery enhancement are also addressed. Examples of novel protein-based drug designs and delivery methodologies that illustrate such enhancement strategies are explored.

Biological Insights into Therapeutic Protein Modifications throughout Trafficking and Their Biopharmaceutical Applications

Over the lifespan of therapeutic proteins, from the point of biosynthesis to the complete clearance from tested subjects, they undergo various biological modifications. Therapeutic influences and molecular mechanisms of these modifications have been well appreciated for some while remained less understood for many. This paper has classified these modifications into multiple categories, according to their processing locations and enzymatic involvement during the trafficking events. It also focuses on the underlying mechanisms and structural-functional relationship between modifications and therapeutic properties. In addition, recent advances in protein engineering, cell line engineering, and process engineering, by exploring these complex cellular processes, are discussed and summarized, for improving functional characteristics and attributes of protein-based biopharmaceutical products.

Self-associated submicron IgG1 particles for pulmonary delivery: effects of non-ionic surfactants on size, shape, stability, and aerosol performance

The ability to produce submicron particles of monoclonal antibodies of different sizes and shapes would enhance their application to pulmonary delivery. Although non-ionic surfactants are widely used as stabilizers in protein formulations, we hypothesized that non-ionic surfactants will affect the shape and size of submicron IgG particles manufactured through precipitation. Submicron particles of IgG1 were produced by a precipitation process which explores the fact that proteins have minimum solubility but maximum precipitation at the isoelectric point. Non-ionic surfactants were used for size and shape control, and as stabilizing agents. Aerosol performance of the antibody nanoparticles was assessed using Andersen Cascade Impactor. Spinhaler® and Handihaler® were used as model DPI devices. SEM micrographs revealed that the shape of the submicron particles was altered by varying the type of surfactant added to the precipitating medium. Particle size as measured by dynamic light scattering was also varied based on the type and concentration of the surfactant. The surfactants were able to stabilize the IgG during the precipitation process. Polyhedral, sponge-like, and spherical nanoparticles demonstrated improved aerosolization properties compared to irregularly shaped (>20 μm) unprocessed particles. Stable antibody submicron particles of different shapes and sizes were prepared. Careful control of the shape of such particles is critical to ensuring optimized lung delivery by dry powder inhalation.

Effects of polymer end-group chemistry and order of deposition on controlled protein delivery from layer-by-layer assembly

Layer-by-layer (LBL) assembly is an attractive platform for controlled release of biologics given its mild fabrication process and versatility in coating substrates of any shape. Proteins can be incorporated into LBL coatings by sequentially depositing oppositely charged polyelectrolytes, which self-assemble into nanoscale films on medical devices or tissue engineering scaffolds. However, previously reported LBL platforms often require the use of a few hundred layers to avoid burst release, which hinders their broad translation due to the lengthy fabrication process, cost, and batch-to-batch variability. Here we report a biodegradable LBL platform composed of only 10 layers with tunable protein release kinetics, which is an order of magnitude less than previously reported LBL platforms. We performed a combinatorial study to examine the effects of polymer chemistry and order of deposition of poly(β-amino) esters on protein release kinetics under 81 LBL assembly conditions. Using the optimal "polyelectrolyte couples" for constructing the LBL film, basic fibroblast growth factor (bFGF) was released gradually over 14 days with retained biological activity to stimulate cell proliferation. The method reported herein is applicable for coating various substrates including metals, polymers, and ceramics and may be used for a broad range of biomedical and tissue engineering applications.

Formulation and delivery of vaccines: Ongoing challenges for animal management

Development of a commercially successful animal vaccine is not only influenced by various immunological factors, such as type of antigen but also by formulation and delivery aspects. The latter includes the need for a vector or specific delivery system, the choice of route of administration and the nature of the target animal population and their habitat. This review describes the formulation and delivery aspects of various types of antigens such as killed microorganisms, proteins and nucleic acids for the development of efficacious and safe animal vaccines. It also focuses on the challenges associated with the different approaches that might be required for formulating and delivering species specific vaccines, particularly if their intended use is for improved animal management with respect to disease and/or reproductive control.

Physicochemical characterization of complex drug substances: evaluation of structural similarities and differences of protamine sulfate from various sources

The purpose of this study was to characterize and evaluate differences of protamine sulfate, a highly basic peptide drug, obtained from five different sources, using orthogonal thermal and spectroscopic analytical methods. Thermogravimetric analysis and modulated differential scanning calorimetry showed that all five protamine sulfate samples had different moisture contents and glass transition and melting temperatures when temperature was modulated from 25 to 270°C. Protamine sulfate from source III had the highest residual moisture content (4.7 ± 0.2%) at 105°C, resulting in the lowest glass transition (109.7°C) and melting (184.2°C) temperatures compared with the other four sources. By Fourier-transform infrared (FTIR) spectroscopy, the five sources of protamine sulfate had indistinguishable spectra, and the spectra were consistent with a predominantly random coil conformation in solution and a minor population in a β-sheet conformation (~12%). Circular dichroism spectropolarimetry confirmed the FTIR results with prominent minima at 206 nm observed for all five sources. Finally, proton ((1)H) nuclear magnetic resonance spectroscopy showed that all five protamine sulfate sources had identical spectra with backbone amide chemical shifts between 8.20 and 8.80 ppm, consistent with proteins with predominantly random coil conformation. In conclusion, thermal analyses showed differences in the thermal behavior of the five sources of protamine sulfate, while spectroscopic analyses showed the samples had a predominantly random coil conformation with a small amount of β-sheet present.

A platform for characterizing therapeutic monoclonal antibody breakdown products by 2D chromatography and top-down mass spectrometry

With the growing commercialization of therapeutic monoclonal antibodies developed for the treatment of various diseases comes the need for increased analytical scrutiny of the impurity components contained within such drug products. Traditionally, relatively low performance and throughput analytical techniques were employed for elucidating the product-related breakdown components derived from the original molecule, including N-terminal Edman sequencing and matrix-assisted laser desorption time-of-flight (MALDI-TOF) mass spectrometry. Although N-terminal sequencing provides a definitive starting point of an unknown breakdown product, the resolution and mass accuracy of MALDI-TOF instruments are often insufficient for unambiguous sequence characterization. Described here is the implementation of existing advanced analytical technologies, including high-performance mass spectrometry (LTQ-Orbitrap XL-ETD) and a chip-based nanoelectrospray autosampling robot (TriVersa NanoMate), for the thorough identification and characterization of breakdown products derived from a force-degraded monoclonal antibody. Many anticipated breakdown products were identified, including Fab fragment (48,325 Da) and heavy chain polypeptide hydrolysis product (15,521 Da). Using high-resolution collisionally induced and electron transfer dissociation methods, additional identifications were made with specific localization of unpredicted modifications. As examples, a modified Fab fragment (N- and C-terminal cyclization, 47,902 Da) and a hydrolyzed free light chain impurity components (23,191 Da) were identified with a high degree of confidence (E value, <1e-5). This work describes the approach for top-down characterization of breakdown products and is readily applicable to additional monoclonal antibodies (mAb) characterization experiments, including charge isoform characterization and aggregate analysis, for a more thorough understanding of therapeutic mAb drug products.

In vivo chondrocyte and transforming growth factor-β1 delivery using the thermosensitive chitosan/starch/β-glycerol phosphate hydrogel

In present study, the chitosan/starch/β-glycerol phosphate hydrogel was investigated as an effective carrier for chondrocytes and delivery of transforming growth factor-β1. In vitro study indicated that transforming growth factor-β1 was released sustainably for 14 days with its biological activity to stimulate chondrocyte functions, as indicated by the strong expression of type II collagen protein. Subcutaneous implantation to rats revealed the strong expressions of type II collagen and aggrecan messenger ribonucleic acids, and also type II collagen protein was observed in the hydrogel in combination with transforming growth factor-β1 within 2 weeks. Our collective results showed the potential of chitosan/starch/β-glycerol phosphate hydrogel for effective delivery of chondrocytes and transforming growth factor-β1, and preserve chondrocytes’ phenotype and functions in vitro.