Subvisible (2-100 µm) particle analysis during biotherapeutic drug product development: Part 2, experience with the application of subvisible particle analysis.

Measurement and characterization of subvisible particles (including proteinaceous and non-proteinaceous particulate matter) is an important aspect of the pharmaceutical development process for biotherapeutics. Health authorities have increased expectations for subvisible particle data beyond criteria specified in the pharmacopeia and covering a wider size range. In addition, subvisible particle data is being requested for samples exposed to various stress conditions and to support process/product changes. Consequently, subvisible particle analysis has expanded beyond routine testing of finished dosage forms using traditional compendial methods. Over the past decade, advances have been made in the detection and understanding of subvisible particle formation. This article presents industry case studies to illustrate the implementation of strategies for subvisible particle analysis as a characterization tool to assess the nature of the particulate matter and applications in drug product development, stability studies and post-marketing changes.

Subvisible (2-100 µm) Particle Analysis During Biotherapeutic Drug Product Development: Part 1, Considerations and Strategy.

Measurement and characterization of subvisible particles (defined here as those ranging in size from 2 to 100 µm), including proteinaceous and nonproteinaceous particles, is an important part of every stage of protein therapeutic development. The tools used and the ways in which the information generated is applied depends on the particular product development stage, the amount of material, and the time available for the analysis. In order to compare results across laboratories and products, it is important to harmonize nomenclature, experimental protocols, data analysis, and interpretation. In this manuscript on perspectives on subvisible particles in protein therapeutic drug products, we focus on the tools available for detection, characterization, and quantification of these species and the strategy around their application.

Protein covalent dimer formation induced by reversed-phase HPLC conditions.

Reversed-phase high-performance liquid chromatography (RP-HPLC), which is routinely used to detect and quantitate levels of protein oxidation, was used to analyze a free cysteine-containing protein. However, the RP-HPLC method appeared to induce dimerization of the oxidized protein. The purpose of this study was to understand the role of RP-HPLC conditions in inducing protein dimerization. Samples were also analyzed by orthogonal size-based analytical methods such as size-exclusion high-performance liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. These methods indicated the presence of dimer and confirmed that the acidic solvent conditions induced the dimer formation of the oxidized protein. Furthermore, the dimerization was observed only when the protein was mildly oxidized and not when the protein was severely oxidized or in its native form. The sulfenic acid form of cysteine is a likely precursor to the disulfide formation. The amount of dimers increased with increasing concentration of trifluoroacetic acid (TFA) or formic acid is in the range of 0%-0.3%. The effect of the organic solvent was less than the effect of TFA/formic acid on dimer formation. Given that RP-HPLC is typically run with low-pH mobile phase containing an ion-pairing acid for improved resolution, its potential for inducing artifacts needs to be taken into consideration during method development.

Demonstrating the stability of albinterferon alfa-2b in the presence of silicone oil.

Silicone oil is often used to decrease glide forces in prefilled syringes and cartridges, common primary container closures for biopharmaceutical products. Silicone oil has been linked to inducing protein aggregation (Diabet Med 1989;6:278; Diabet Care 1987;10:786-790), leading to patient safety and immunogenicity concerns. Because of the silicone oil application process (Biotech Adv 2007;25:318-324), silicone oil levels tend to vary between individual container closures. Various silicone oil levels were applied to a container closure prior to filling and lyophilization of an albumin and interferon alfa-2b fusion protein (albinterferon alfa-2b). Data demonstrated that high silicone oil levels in combination with intended and stress storage conditions had no impact on protein purity, higher order structure, stability trajectory, or biological activity. Subvisible particulate analysis (1-10 µm range) from active and placebo samples from siliconized glass barrels showed similar particle counts. Increases in solution turbidity readings for both active and placebo samples correlated well with increases in silicone oil levels, suggesting that the particles in solution are related to the presence of silicone oil and not large protein aggregates. Results from this study demonstrate that silicone oil is not always detrimental to proteins; nevertheless, assessing the impact of silicone oil on a product case-by-case basis is still recommended.

An industry perspective on the monitoring of subvisible particles as a quality attribute for protein therapeutics.

Concern around the lack of monitoring of proteinaceous subvisible particulates in the 0.1-10 microm range has been heightened (Carpenter et al., 2009, J Pharm Sci 98: 1202-1205), primarily due to uncertainty around the potential immunogenicity risk from these particles. This article, representing the opinions of a number of industry scientists, aims to further the discussion by developing a common understanding around the technical capabilities, limitations, as well as utility of monitoring this size range; reiterating that the link between aggregation and clinical immunogenicity has not been unequivocally established; and emphasizing that such particles are present in marketed products which remain safe and efficacious despite the lack of monitoring. Measurement of subvisible particulates in the <10 microm size range has value as an aid in product development and characterization. Limitations in measurement technologies, variability from container/closure, concentration, viscosity, history, and inherent batch heterogeneity, make these measurements unsuitable as specification for release and stability or for comparability, at the present time. Such particles constitute microgram levels of protein with currently monitored sizes >or=10 microm representing the largest fraction. These levels are well below what is detected or reported for other product quality attributes. Subvisible particles remain a product quality attribute that is also qualified in clinical trials.

Effect of polyanions on the structure and stability of repifermin (keratinocyte growth factor-2).

The interaction of several of the fibroblast growth factors (FGFs) with polyanions is thought to be of physiological significance and has been exploited to create more stable pharmaceutical formulations of FGF-1 and -2. The extent of such phenomena throughout the 23-member FGF family is, however, unknown. In these studies, we examine the effect of several polyanions on the structure and stability of keratinocyte growth factor 2 (KGF-2, FGF-10), a candidate for use as a wound-healing agent. Employing a variety of methods sensitive to the protein's structure including circular dichroism (CD), intrinsic fluorescence, derivative near-UV absorption spectroscopy, bis-ANS (4,4'-dianilino-1,1'-binaphthyl-5,5-disulfonic acid) fluorescence, differential scanning calorimetry (DSC), and dynamic light scattering (DLS), we find that a variety of polyanions (e.g., heparin, sucrose octasulfate (SOS), and inositol hexaphosphate (IHP)) stabilize KGF-2 by increasing the thermal-unfolding temperature by approximately 9-15 degrees C. Negatively charged liposomes produce a similar effect, arguing for relatively nonspecific interactions of polyanions with KGF-2. Unlike some other FGFs, no evidence for the presence of a molten globule state is found during thermal perturbation of this growth factor. The generality of this polyanion/protein interaction is discussed as well as its potential role in various cellular events such as protein folding and transport.

Lyophilization cycle development for a high-concentration monoclonal antibody formulation lacking a crystalline bulking agent.

An efficient freeze-dry cycle was developed for a high concentration monoclonal antibody formulation lacking a crystalline bulking agent. The formulation, at multiple protein concentrations, was characterized using differential scanning calorimetry (DSC) and freeze-dry microscopy. At low protein concentrations the glass transition temperature of the maximally freeze-concentrated solution (T(g)') determined by DSC was similar to the collapse temperature determined by freeze-dry microscopy. However, at higher protein concentrations, the difference between collapse temperature and T(g)' became progressively larger. The difference between the onset temperature for collapse and the complete collapse temperature also became progressively larger as protein concentration increased. JMP Design of Experiment studies were used to assess the effect of freezing rate, primary drying shelf temperature, and chamber pressure on primary drying product temperature, length of primary drying, and product quality attributes. Primary drying was shortened significantly by adjusting to conditions where the product temperature substantially exceeded T(g)' without any apparent detrimental effect to the product.