Using the fluorescence red edge effect to assess the long-term stability of lyophilized protein formulations

Predicting the Stability of Formulations Containing Lyophilized Human Serum Albumin and Sucrose/Trehalose Using Solid-State NMR Spectroscopy

Stabilization of proteins by disaccharides in lyophilized formulations depends on the interactions between the protein and the disaccharide (system homogeneity) and the sufficiently low mobility of the system. Human serum albumin (HSA) was lyophilized with disaccharides (sucrose and/or trehalose) in different relative concentrations. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy 1H T1 and 1H T1ρ relaxation times were measured to determine the homogeneity of the lyophilized systems on 20-50 and 1-3 nm domains, respectively, with 1H T1 relaxation times also being used to determine the β-relaxation rate. HSA/sucrose systems had longer 1H T1 relaxation times and were slightly more stable than HSA/trehalose systems in almost all cases shown. HSA/sucrose/trehalose systems have 1H T1 relaxation times between the HSA/sucrose and HSA/trehalose systems and did not result in a more stable system compared with binary systems. Inhomogeneity was evident in a sample containing relative concentrations of 10% HSA and 90% trehalose, suggesting trehalose crystallization during lyophilization. Under these stability conditions and with these ssNMR acquisition parameters, a 1H T1 relaxation time below 1.5 s correlated with an unstable sample, regardless of the disaccharide(s) used.

Predicting the Stability of Lyophilized Human Serum Albumin Formulations Containing Sucrose and Trehalose Using Solid-State NMR Spectroscopy: Effect of Storage Temperature on 1H T1 Relaxation Times

In a lyophilized protein/disaccharide system, the ability of the disaccharide to form a homogeneous mixture with the protein and to slow the protein mobility dictates the stabilization potential of the formulation. Human serum albumin was lyophilized with sucrose or trehalose in histidine, phosphate, or citrate buffer. 1H T1 relaxation times were measured by solid-state NMR spectroscopy and were used to assess the homogeneity and mobility of the samples after zero, six, and twelve months at different temperatures. The mobility of the samples decreased after 6 and 12 months storage at elevated temperatures, consistent with structural relaxation of the amorphous disaccharide matrix. Formulations with sucrose had lower mobility and greater stability than formulations with trehalose.

Solid-State NMR Characterization of Lyophilized Formulations of Monoclonal Antibody Therapeutics

Monoclonal antibodies (mAbs) are an important and growing class of biotherapeutic drugs. Method development for the characterization of critical quality attributes, including higher-order structure (HOS), of mAbs remains an area of active inquiry. Recently, solution-state nuclear magnetic resonance (NMR) spectroscopy has received increased attention and is a means for reliable, high-resolution HOS characterization of aqueous-based preparations of mAbs. While mAbs are predominantly formulated in solution, up to 20% are prepared as solid amorphous powders and techniques for the robust characterization of HOS in the solid state remain limited. We propose here the use of solid-state NMR (ssNMR) fingerprinting to inform directly on the HOS of solid preparations of mAbs. Using lyophilized samples of the NISTmAb reference material prepared with different formulation conditions, we demonstrate that ¹H-¹³C cross-polarization (hC-CP) buildup spectral series at natural isotopic abundance mAb samples are sensitive to differences in formulation. We also demonstrate that principal component analysis (PCA) can be used to differentiate the samples from one another in a user-independent manner while also highlighting areas where expert analysis can provide structural details about important molecular interactions in solid-phase protein formulations. Results from this study contribute to establishing the foundation for the use of ssNMR for HOS characterization of solid-phase biotherapeutics.

In Situ Characterization of the Microstructural Evolution of Biopharmaceutical Solid-State Formulations with Implications for Protein Stability

Lyophilized and spray-dried biopharmaceutical formulations are used to provide long-term stability for storage and transport, but questions remain about the molecular structure in these solid formulations and how this structure may be responsible for protein stability. Small-angle neutron scattering with a humidity control environment is used to characterize protein-scale microstructural changes in such solid-state formulations as they are humidified and dried in situ. The findings indicate that irreversible protein aggregates of stressed formulations do not form within the solid-state but do emerge upon reconstitution of the formulation. After plasticization of the solid-state matrix by exposure to humidity, the formation of reversibly self-associating aggregates can be detected in situ. The characterization of the protein-scale microstructure in these solid-state formulations facilitates further efforts to understand the underlying mechanisms that promote long-term protein stability.

Investigating Structure and Dynamics of Proteins in Amorphous Phases Using Neutron Scattering

In order to increase shelf life and minimize aggregation during storage, many biotherapeutic drugs are formulated and stored as either frozen solutions or lyophilized powders. However, characterizing amorphous solids can be challenging with the commonly available set of biophysical measurements used for proteins in liquid solutions. Therefore, some questions remain regarding the structure of the active pharmaceutical ingredient during freezing and drying of the drug product and the molecular role of excipients. Neutron scattering is a powerful technique to study structure and dynamics of a variety of systems in both solid and liquid phases. Moreover, neutron scattering experiments can generally be correlated with theory and molecular simulations to analyze experimental data. In this article, we focus on the use of neutron techniques to address problems of biotechnological interest. We describe the use of small-angle neutron scattering to study the solution structure of biological molecules and the packing arrangement in amorphous phases, that is, frozen glasses and freeze-dried protein powders. In addition, we discuss the use of neutron spectroscopy to measure the dynamics of glassy systems at different time and length scales. Overall, we expect that the present article will guide and prompt the use of neutron scattering to provide unique insights on many of the outstanding questions in biotechnology.

Dynamics of hydrated proteins and bio-protectants: Caged dynamics, β-relaxation, and α-relaxation

BACKGROUND

The properties of the three dynamic processes, α-relaxation, ν-relaxation, and caged dynamics in aqueous mixtures and hydrated proteins are analogous to corresponding processes found in van der Waals and polymeric glass-formers apart from minor differences.

METHODS

Collection of various experimental data enables us to characterize the structural α-relaxation of the protein coupled to hydration water (HW), the secondary or ν-relaxation of HW, and the caged HW process.

RESULTS

From the T-dependence of the ν-relaxation time of hydrated myoglobin, lysozyme, and bovine serum albumin, we obtain Ton at which it enters the experimental time windows of Mössbauer and neutron scattering spectroscopies, coinciding with protein dynamical transition (PDT) temperature Td. However, for all systems considered, the α-relaxation time at Ton or Td is many orders of magnitude longer. The other step change of the mean-square-displacement (MSD) at Tg_alpha originates from the coupling of the nearly constant loss (NCL) of caged HW to density. The coupling of the NCL to density is further demonstrated by another step change at the secondary glass temperature Tg_beta in two bio-protectants, trehalose and sucrose.

CONCLUSIONS

The structural α-relaxation plays no role in PDT. Since PDT is simply due to the ν-relaxation of HW, the term PDT is a misnomer. NCL of caged dynamics is coupled to density and show transitions at lower temperature, Tg_beta and Tg_alpha.

GENERAL SIGNIFICANCE

The so-called protein dynamical transition (PDT) of hydrated proteins is not caused by the structural α-relaxation of the protein but by the secondary ν-relaxation of hydration water. "This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo".

Stabilization of proteins in solid form

Immunogenicity of aggregated or otherwise degraded protein delivered from depots or other biopharmaceutical products is an increasing concern, and the ability to deliver stable, active protein is of central importance. We review characterization approaches for solid protein dosage forms with respect to metrics that are intended to be predictive of protein stability against aggregation and other degradation processes. Each of these approaches is ultimately motivated by hypothetical connections between protein stability and the material property being measured. We critically evaluate correlations between these properties and stability outcomes, and use these evaluations to revise the currently standing hypotheses. Based on this we provide simple physical principles that are necessary (and possibly sufficient) for generating solid delivery vehicles with stable protein loads. Essentially, proteins should be strongly coupled (typically through H-bonds) to the bulk regions of a phase-homogeneous matrix with suppressed β relaxation. We also provide a framework for reliable characterization of solid protein forms with respect to stability.