Protein freeze concentration and micro-segregation analysed in a temperature-controlled freeze container

Impact of Sugar Molecular Weight on the Miscibility and Stability of Lyophilized and Spray-Dried Protein Formulations

Poor stability of biological products such as proteins is a major challenge facing the biopharmaceutical industry. Poor stability is usually mitigated by formulating these products in the solid state, employing sugars as stabilizers. Several studies have pointed out the superior stabilizing ability of disaccharides, including sucrose and trehalose, as compared to polysaccharides such as dextrans. The aim of this study was to investigate the impact of excipient molecular weight on miscibility with a model protein, bovine serum albumin (BSA). Aqueous solutions containing a binary combination of a sugar-based stabilizer and BSA were dried using different methods (air drying to form films, spray drying, and lyophilization). The stabilizers tested varied in molecular weight and were dextran 6, 70, or 2000 kDa, hydroxypropyl methyl cellulose (HPMC), and trehalose. Miscibility was evaluated using a variety of techniques including confocal fluorescence microcopy, infrared and Raman microscopy, and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. The stability of BSA in dried mixtures subjected to accelerated storage conditions was also measured. BSA was more stable in the presence of dextran 2000 kDa compared to dextran 70 and 6 kDa, while stability was highest in trehalose and lowest in HPMC. From ssNMR spectroscopy, BSA-Dex 2000 kDa and BSA-trehalose were miscible over 20 and 5 nm length scales, BSA-Dex 6 kDa was miscible over a 20 nm length scale and phase-separated over a 5 nm length scale, while BSA-Dex 70 kDa and BSA-HPMC were phase-separated over both length scales. It was postulated that for dextran, the size of the polysaccharide relative to the size of the protein determined the extent of the system miscibility and stability. A smaller or similar polysaccharide size compared to that of the protein, as in the case of BSA-Dex 6 kDa and BSA-Dex 70 kDa, leads to depletion-induced phase separation. A much larger polysaccharide size compared to that of the protein allows the protein molecules to be trapped within a polysaccharide mesh, resulting in a miscible system. This study suggests that the impact of the relative size of the stabilizer and protein on miscibility is more complex than previously considered.

Directional freezing and thawing of biologics in drug substance bottles

Biological drug substance (DS) is typically stored frozen to increase stability. However, freezing and thawing (F/T) of DS can impact product quality and therefore F/T processes need to be controlled. Because active F/T systems for DS bottles are lacking, freezing is often performed uncontrolled in conventional freezers, and thawing at ambient temperature or using water baths. In this study, we evaluated a novel device for F/T of DS in bottles, which can be operated in conventional freezers, generating a directed air stream around bottles. We characterized the F/T geometry and process performance in comparison to passive F/T using temperature mapping and analysis of concentration gradients. The device was able to better control the F/T process by inducing directional bottom-up F/T. As a result, it reduced cryo-concentration during freezing as well as ice mound formation. However, freezing with the device was dependent on freezer performance, i.e. prolonged process times in a highly loaded freezer were accompanied by increased cryo-concentrations. Thawing was faster compared to without the device, but had no impact on concentration gradients and was slower compared to thawing in a water bath. High-performance freezers might be required to fully exploit the potential of directional freezing with this device and allow F/T process harmonization and scaling across sites.

Impact of secondary ice in a frozen NaCl freeze-concentrated solution on the extent of methylene blue aggregation

Freezing and lyophilization have been utilized for decades to stabilize pharmaceutical and food products. Freezing a solution that contains dissolved salt and/or organic matter produces pure primary ice crystal grains separated by freeze-concentrated solutions (FCS). The microscopic size of the primary ice crystals depends on the cooling conditions and the concentration of the solutes. It is generally accepted that primary ice crystals size influences the rate of sublimation and also can impact physico-chemical behaviour of the species in the FCS. This article, however, presents a case where the secondary ice formed inside the FCS plays a critical role. We microscoped the structures of ice-cast FCS with an environmental scanning electron microscope and applied the aggregation-sensitive spectroscopic probe methylene blue to determine how the microstructure affects the molecular arrangement. We show that slow cooling at -50 °C produces large salt crystals with a small specific surface, resulting in a high degree of molecular aggregation within the FCS. In contrast, fast liquid nitrogen cooling yields an ultrafine structure of salt crystals having a large specific surface area and, therefore, inducing smaller aggregation. The study highlights a critical role of secondary ice in solute aggregation and introduces methylene blue as a molecular probe to investigate freezing behaviour of aqueous systems with crystalline solute.

Application of Formulation Principles to Stability Issues Encountered During Processing, Manufacturing, and Storage of Drug Substance and Drug Product Protein Therapeutics

The field of formulation and stabilization of protein therapeutics has become rather extensive. However, most of the focus has been on stabilization of the final drug product. Yet, proteins experience stress and degradation through the manufacturing process, starting with fermentaition. This review describes how formulation principles can be applied to stabilize biopharmaceutical proteins during bioprocessing and manufacturing, considering each unit operation involved in prepration of the drug substance. In addition, the impact of the container on stabilty is discussed as well.

The effect of mAb and excipient cryoconcentration on long-term frozen storage stability – Part 1: Higher molecular weight species and subvisible particle formation

Cryoconcentration upon large-scale freezing of monoclonal antibody (mAb) solutions leads to regions of different ratios of low molecular weight excipients, like buffer species or sugars, to protein. This study focused on the impact of the buffer species to mAb ratio on aggregate formation after frozen storage at −80 °C, −20 °C, and − 10 °C after 6 weeks, 6 months, and 12 months. An optimised sample preparation was established to measure T_g′ of samples with different mAb to histidine ratios via differential scanning calorimetry (DSC). After storage higher molecular weight species (HMWS) and subvisible particles (SVPs) were detected using size-exclusion chromatography (SEC) and FlowCam, respectively. For all samples, sigmoidal curves in DSC thermograms allowed to precisely determine T_g′ in formulations without glass forming sugars. Storage below T_g′ did not lead to mAb aggregation. Above T_g′, at −20 °C and − 10 °C, small changes in mAb and buffer concentration markedly impacted stability. Samples with lower mAb concentration showed increased formation of HMWS. In contrast, higher concentrated samples led to more SVPs. A shift in the mAb to histidine ratio towards mAb significantly increased overall stability. Cryoconcentration upon large-scale freezing affects mAb stability, although relative changes compared to the initial concentration are small. Storage below T_g′ completely prevents mAb aggregation and particle formation.

The effect of mAb and excipient cryoconcentration on long-term frozen storage stability – part 2: Aggregate formation and oxidation

We examined the impact of monoclonal antibody (mAb) and buffer concentration, mimicking the cryoconcentration found upon freezing in a 2 L bottle, on mAb stability during frozen storage. Upon cryoconcentration, larger protein molecules and small excipient molecules freeze-concentrate differently, resulting in different protein to stabiliser ratios within a container. Understanding the impact of these shifted ratios on protein stability is essential. For two mAbs a set of samples with constant mAb (5 mg/mL) or buffer concentration (medium histidine/adipic acid) was prepared and stored for 6 months at −10 °C. Stability was evaluated via size-exclusion chromatography, flow imaging microscopy, UV/Vis spectroscopy at 350 nm, and protein A chromatography. Dynamic light scattering was used to determine k_D values. Soluble aggregate levels were unaffected by mAb concentration, but increased with histidine concentration. No trend in optical density could be identified. In contrast, increasing mAb or buffer concentration facilitated the formation of subvisible particles. A trend towards attractive protein-protein interactions was seen with higher ionic strength. MAb oxidation levels were negatively affected by increasing histidine concentration, but became less with higher mAb concentration. Small changes in mAb and buffer composition had a significant impact on stability during six-month frozen storage. Thus, preventing cryoconcentration effects in larger freezing containers may improve long-term stability.

Isolated Effects of Plasma Freezing versus Thawing on Metabolite Stability

Freezing and thawing plasma samples is known to perturb metabolite stability. However, no study has systematically tested how different freezing and thawing methods affect plasma metabolite levels. The objective of this study was to isolate the effects of freezing from thawing on mouse plasma metabolite levels, by comparing a matrix of freezing and thawing conditions through 10 freeze–thaw cycles. We tested freezing with liquid nitrogen (LN2), at −80 °C, or at −20 °C, and thawing quickly in room temperature water or slowly on ice. Plasma samples were extracted and the relative abundance of 87 metabolites was obtained via liquid chromatography–mass spectrometry (LC–MS). Observed changes in metabolite abundance by treatment group correlated with the amount of time it took for samples to freeze or thaw. Thus, snap-freezing with LN2 and quick-thawing with water led to minimal changes in metabolite levels. Conversely, samples frozen at −20 °C exhibited the most changes in metabolite levels, likely because freezing required about 4 h, versus freezing instantaneously in LN2. Overall, our results show that plasma samples subjected to up to 10 cycles of LN2 snap-freezing with room temperature water quick-thawing exhibit remarkable metabolomic stability.

Evaluation of Two Novel Scale-Down Devices for Testing Monoclonal Antibody Aggregation During Large-Scale Freezing

There is a need for representative small volume devices that reflect monoclonal antibody (mAb) aggregation during freezing and thawing (FT) in large containers. We characterised two novel devices that aim to mimic the stress in rectangular 2 L bottles. The first scale-down device (SDD) consists of a 125 mL bottle surrounded by a 3D printed cover that manipulates heat exchange. The second device, a micro scale-down device (mSDD), adapts cooling and heating of 10 mL vials to extend stress time. MAb aggregation upon repeated FT was evaluated considering formation of higher molecular weight species, subvisible particles, and the increase in hydrodynamic radius, polydispersity index, and optical density at 350 nm. Three different mAb solutions were processed. Both an unshielded 125 mL bottle and the SDD can be used to predict aggregation during FT in 2 L bottles. In specific cases the unshielded 125 mL bottle underestimates whereas the SDD slightly overestimates soluble aggregate formation. The mSDD increases aggregation compared to 10 mL vials but is less representative than the SDD. Ultimately, both SDDs enable characterisation of protein sensitivity to large-scale FT with two orders of magnitude less volume and are superior to simply using smaller bottles.

Scaling Down Large-Scale Thawing of Monoclonal Antibody Solutions: 3D Temperature Profiles, Changes in Concentration, and Density Gradients

PURPOSE

Scale-down devices (SDD) are designed to simulate large-scale thawing of protein drug substance, but require only a fraction of the material. To evaluate the performance of a new SDD that aims to predict thawing in large-scale 2 L bottles, we characterised 3D temperature profiles and changes in concentration and density in comparison to 125 mL and 2 L bottles. Differences in diffusion between a monoclonal antibody (mAb) and histidine buffer after thawing were examined.

METHODS

Temperature profiles at six distinct positions were recorded with type T thermocouples. Size-exclusion chromatography allowed quantification of mAb and histidine. Polysorbate 80 was quantified using a fluorescent dye assay. In addition, the solution's density at different locations in bottles and the SDD was identified.

RESULTS

The temperature profiles in the SDD and the large-scale 2 L bottle during thawing were similar. Significant concentration gradients were detected in the 2 L bottle leading to marked density gradients. The SDD slightly overestimated the dilution in the top region and the maximum concentrations at the bottom. Fast diffusion resulted in rapid equilibration of histidine.

CONCLUSION

The innovative SDD allows a realistic characterisation and helps to understand thawing processes of mAb solutions in large-scale 2 L bottles. Only a fraction of material is needed to gain insights into the thawing behaviour that is associated with several possible detrimental limitations.

Alternatives to Meat and Dairy

The increasing size and affluence of the global population have led to a rising demand for high-protein foods such as dairy and meat. Because it will be impossible to supply sufficient protein to everyone solely with dairy and meat, we need to transition at least part of our diets toward protein foods that are more sustainable to produce. The best way to convince consumers to make this transition is to offer products that easily fit into their current habits and diets by mimicking the original foods. This review focuses on methods of creating an internal microstructure close to that of the animal-based originals. One can directly employ plant products, use intermediates such as cell factories, or grow cultured meat by using nutrients of plant origin. We discuss methods of creating high-quality alternatives to meat and dairy foods, describe their relative merits, and provide an outlook toward the future.

Protection of Alcohol Dehydrogenase against Freeze-Thaw Stress by Ice-Binding Proteins Is Proportional to Their Ice Recrystallization Inhibition Property

Ice-binding proteins (IBPs) have ice recrystallization inhibition (IRI) activity. IRI property has been extensively utilized for the cryopreservation of different types of cells and tissues. Recent reports demonstrated that IRI can also play a significant role in protecting proteins from freezing damage during freeze-thaw cycles. In this study, we hypothesized that the protective capability of IBPs on proteins against freeze-thaw damage is proportional to their IRI activity. Hence we used two IBPs: one with higher IRI activity (LeIBP) and the other with lower activity (FfIBP). Yeast alcohol dehydrogenase (ADH) was used as a freeze-labile model protein. IBPs and ADH were mixed, frozen at -20 °C, and thawed repeatedly. The structure of ADH was assessed using fluorescence emission spectra probed by 1-anilinonaphthalene-8-sulfonate over the repeated freeze-thaw cycles. The activity was monitored at 340 nm spectrophotometrically. Fluorescence data and activity clearly indicated that ADH without IBP was freeze-labile. However, ADH maintained about 70% residual activity after five repeated cycles at a minimal concentration of 0.1 mg mL^-1 of high IRI-active LeIBP, but only 50% activity at 4 mg mL^-1 of low active FfIBP. These results showed that the protection of proteins from freeze-thaw stress by IBPs is proportional to their IRI activity.

Cryoconcentration and 3D Temperature Profiles During Freezing of mAb Solutions in Large-Scale PET Bottles and a Novel Scale-Down Device

PURPOSE

Small-scale models that simulate large-scale freezing of bulk drug substance of biopharmaceuticals are highly needed to define freezing and formulation parameters based on process understanding. We evaluated a novel scale-down device (SDD), which is based on a specially designed insulation cover, with respect to changes in concentration after freezing, referred to as cryoconcentration, and 3D temperature profiles. Furthermore, the effect of the initial monoclonal antibody (mAb) concentration on cryoconcentration was addressed.

METHODS

2 L and 125 mL bottles were utilized. Temperatures were mapped using type T thermocouples. Frozen blocks were cut and mAb and histidine concentrations were analysed by HPLC. In addition, concentration- and temperature-dependent viscosities were measured.

RESULTS

3D freezing profiles in the SDD were comparable to large-scale bottles. The SDD accurately predicted cryoconcentration of both mAb and histidine of large-scale freezing. Concentric changes in concentration were evident as well as an unforeseen diluted core at the last point to freeze. At low initial mAb concentration cryoconcentration was substantial, while high initial mAb concentration suppressed cryoconcentration almost completely.

CONCLUSION

The novel SDD gives detailed insights into large-scale freezing of mAb solutions using only a fraction of the simulated volume. It is a promising material- and cost-saving tool to understand large-scale freezing processes.

The need for new control strategies for particulate matter in parenterals

An undesirable characteristic in lyophilized parenteral products is the potential presence of particulate matter in the final product, which may affect patient safety. In this study, quality risk management tools described in the International Conference on Harmonization Guideline Q9 were used to estimate the risks for a pharmaceutical manufacturing line, based on three critical quality attributes: (1) visible particulate matter; (2) lyo-cake collapse traces; and (3) lyo-cake melt-back traces. Together with a Process Failure Mode Effect Analysis (PFMEA), an input-output analysis of the individual unit operations identified seven major material classes of extrinsic particulate matter. In addition to the process assessment, an experimental investigation of the location of impurities in lyophilized products was performed. To that end, intentionally contaminated vials were examined to locate the particulate matter and its possible migration. The results emphasize the importance of a full transmission mode release testing since the particles may enter the interior of the lyo-cake. A theoretical explanation of the observed impurity locations is provided.

Ice-recrystallization inhibiting polymers protect proteins against freeze-stress and enable glycerol-free cryostorage

Proteins are ubiquitous in molecular biotechnology, biotechnology and as therapeutics, but there are significant challenges in their storage and distribution, with freezing often required. This is traditionally achieved by the addition of cryoprotective agents such as glycerol (or trehalose) or covalent modification of mutated proteins with cryoprotectants. Here, ice recrystallization inhibiting polymers, inspired by antifreeze proteins, are used synergistically with poly(ethylene glycol) as an alternative to glycerol. The primary mechanism of action appears to be preventing irreversible aggregation due to ice growth. The polymer formulation is successfully used to cryopreserve a range of important proteins including insulin, Taq DNA polymerase and an IgG antibody. The polymers do not require covalent conjugation, nor modification of the protein and are already used in a wide range of biomedical applications, which will facilitate translation to a range of biologics.

Rapid, Reproducible, Quantifiable NMR Metabolomics: Methanol and Methanol: Chloroform Precipitation for Removal of Macromolecules in Serum and Whole Blood

Background: Though blood is an excellent biofluid for metabolomics, proteins and lipids present in blood can interfere with 1d-¹H NMR spectra and disrupt quantification of metabolites. Here, we present effective macromolecule removal strategies for serum and whole blood (WB) samples. Methods: A variety of macromolecule removal strategies were compared in both WB and serum, along with tests of ultrafiltration alone and in combination with precipitation methods. Results: In healthy human serum, methanol:chloroform:water extraction with ultrafiltration was compared to methanol precipitation with and without ultrafiltration. Methods were tested in healthy pooled human serum, and in serum from patients with sepsis. Effects of long-term storage at −80 °C were tested to explore the impact of macromolecule removal strategy on serum from different conditions. In WB a variety of extraction strategies were tested in two types of WB (from pigs and baboons) to examine the impact of macromolecule removal strategies on different samples. Conclusions: In healthy human serum methanol precipitation of serum with ultrafiltration was superior, but was similar in recovery and variance to methanol:chloroform:water extraction with ultrafiltration in pooled serum from patients with sepsis. In WB, high quality, quantifiable spectra were obtained with the use of a methanol: chloroform precipitation.