Liquid Formulations for Long-Term Storage of Monoclonal IgGs

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

N-Acetylated-L-arginine (NALA) is an enhanced protein aggregation suppressor under interfacial stresses and elevated temperature for protein liquid formulations

Even though arginine hydrochloride has been recognized as a protein aggregation suppressor in the biopharmaceutical industry, its use has been questioned due to decreasing transition unfolding temperatures (T_m). Four compounds were designed to enhance the role of arginine by changing the length of the carbon chain with removal or N-acetylation of α-amino group. Biophysical properties were observed by differential scanning calorimetry (DSC), dynamic light scattering (DLS), size-exclusion chromatography (SEC), and flow imaging (FI). N-Acetyl-L-arginine (NALA) performed the best at minimizing decrease in T_m with arginine at different pH. NALA also demonstrated relatively higher colloidal stability than arginine hydrochloride, especially in the acidic pH, thereby reducing agitation stress of IgG. Moreover, NALA exhibited a cooperative effect with commercially used glycine buffer for IVIG to maintain the monomer contents with almost no change and suppressed larger particle formation after agitation with heat. The study concludes that the decreasing T_m of proteins by arginine hydrochloride is due to amide group in the α-carbon chain. Moreover, chemical modification on the group compared to removing it will be a breakthrough of arginine's limitations and optimize storage stability of protein therapeutics.

Science and art of protein formulation development

Protein pharmaceuticals have become a significant class of marketed drug products and are expected to grow steadily over the next decade. Development of a commercial protein product is, however, a rather complex process. A critical step in this process is formulation development, enabling the final product configuration. A number of challenges still exist in the formulation development process. This review is intended to discuss these challenges, to illustrate the basic formulation development processes, and to compare the options and strategies in practical formulation development.

Computational Design To Reduce Conformational Flexibility and Aggregation Rates of an Antibody Fab Fragment

Computationally guided semirational design has significant potential for improving the aggregation kinetics of protein biopharmaceuticals. While improvement in the global conformational stability can stabilize proteins to aggregation under some conditions, previous studies suggest that such an approach is limited, because thermal transition temperatures ( T_m) and the fraction of protein unfolded ( f_T) tend to only correlate with aggregation kinetics where the protein is incubated at temperatures approaching the T_m. This is because under these conditions, aggregation from globally unfolded protein becomes dominant. However, under native conditions, the aggregation kinetics are presumed to be dependent on local structural fluctuations or partial unfolding of the native state, which reveal regions of high propensity to form protein-protein interactions that lead to aggregation. In this work, we have targeted the design of stabilizing mutations to regions of the A33 Fab surface structure, which were predicted to be more flexible. This Fab already has high global stability, and global unfolding is not the main cause of aggregation under most conditions. Therefore, the aim was to reduce the conformational flexibility and entropy of the native protein at various locations and thus identify which of those regions has the greatest influence on the aggregation kinetics. Highly dynamic regions of structure were identified through both molecular dynamics simulation and B-factor analysis of related X-ray crystal structures. The most flexible residues were mutated into more stable variants, as predicted by Rosetta, which evaluates the ΔΔ G_ND for each potential point mutation. Additional destabilizing variants were prepared as controls to evaluate the prediction accuracy and also to assess the general influence of conformational stability on aggregation kinetics. The thermal conformational stability, and aggregation rates of 18 variants at 65 °C, were each examined at pH 4, 200 mM ionic strength, under which conditions the initial wild-type protein was <5% unfolded. Variants with decreased T_m values led to more rapid aggregation due to an increase in the fraction of protein unfolded under the conditions studied. As expected, no significant improvements were observed in the global conformational stability as measured by T_m. However, 6 of the 12 stable variants led to an increase in the cooperativity of unfolding, consistent with lower conformational flexibility and entropy in the native ensemble. Three of these had 5-11% lower aggregation rates, and their structural clustering indicated that the local dynamics of the C-terminus of the heavy chain had a role in influencing the aggregation rate.

Practical Approaches to Forced Degradation Studies of Vaccines

During the early stages of vaccine development, forced degradation studies are conducted to provide information about the degradation properties of vaccine formulations. In addition to supporting the development of analytical methods for the detection of degradation products, these stress studies are used to identify optimal long-term storage conditions and are part of the regulatory requirements for the submission of stability data. In this chapter, we provide detailed methods for forced degradation analysis under thermal, light, and mechanical stress conditions.

Comparative Evaluation of the Chemical Stability of 4 Well-Defined Immunoglobulin G1-Fc Glycoforms

As part of a series of articles in this special issue evaluating model IgG1-Fc glycoforms for biosimilarity analysis, 3 well-defined IgG1-Fc glycoforms (high mannose-Fc, Man5-Fc, and N-acetylglucosamine-Fc) and a nonglycosylated Fc protein (N297Q-Fc) were examined in this work to elucidate chemical degradation pathways. The 4 proteins underwent a combination of accelerated thermal stability studies and 4 independent forced degradation studies (UV light, metal-catalyzed oxidation, peroxyl radicals, and hydrogen peroxide) at pH 6.0. Our results highlight chemical degradations at Asn315, Met428, Trp277, and Trp313. A cross-comparison of the different Fc glycoforms, stress conditions, and the observed chemical reactions revealed that both the deamidation of Asn315 and the transformation of Trp277 into glycine hydroperoxide were glycan dependent during incubation for 3 months at 40 °C. Our data will show that different glycans not only affect chemical degradation differently but also do lead to different impurity profiles, which can affect chemical degradation.

Evaluating mixtures of 14 hygroscopic additives to improve antibody microarray performance

Microarrays allow the miniaturization and multiplexing of biological assays while only requiring minute amounts of samples. As a consequence of the small volumes used for spotting and the assays, evaporation often deteriorates the quality, reproducibility of spots, and the overall assay performance. Glycerol is commonly added to antibody microarray printing buffers to decrease evaporation; however, it often decreases the binding of antibodies to the surface, thereby negatively affecting assay sensitivity. Here, combinations of 14 hygroscopic chemicals were used as additives to printing buffers for contact-printed antibody microarrays on four different surface chemistries. The ability of the additives to suppress evaporation was quantified by measuring the residual buffer volume in open quill pins over time. The seven best additives were then printed either individually or as a 1:1 mixture of two additives, and the homogeneity, intensity, and reproducibility of both the spotted protein and of a fluorescently labeled analyte in an assay were quantified. Among the 28 combinations on the four slides, many were found to outperform glycerol, and the best additive mixtures were further evaluated by changing the ratio of the two additives. We observed that the optimal additive mixture was dependent on the slide chemistry, and that it was possible to increase the binding of antibodies to the surface threefold compared to 50 % glycerol, while decreasing whole-slide coefficient of variation to 5.9 %. For the two best slides, improvements were made for both the limit of detection (1.6× and 5.9×, respectively) and the quantification range (1.2× and 2.1×, respectively). The additive mixtures identified here thus help improve assay reproducibility and performance, and might be beneficial to all types of microarrays that suffer from evaporation of the printing buffers.

Conformational and Colloidal Stabilities of Isolated Constant Domains of Human Immunoglobulin G and Their Impact on Antibody Aggregation under Acidic Conditions

Antibody therapeutics are now in widespread use and provide a new approach for treating serious diseases such as rheumatic diseases and cancer. Monoclonal antibodies used as therapeutic agents must be of high quality, and their safety must be guaranteed. Aggregated antibody is a degradation product that may be generated during the manufacturing process. To maintain the high quality and safety of antibody therapeutics, it is necessary to understand the mechanism of aggregation and to develop technologies to strictly control aggregate formation. Here, we extensively investigated the conformational and colloidal characteristics of isolated antibody constant domains, and provided insights into the molecular mechanism of antibody aggregation. Isolated domains (CH2, CH3, CL, and CH1-CL dimer) of human immunoglobulin G were synthesized, solubilized using 49 sets of solution conditions (pH 2-8 and 0-300 mM NaCl), and characterized using circular dichroism, intrinsic tryptophan fluorescence, and dynamic light scattering. Salt-induced conformational changes and oligomer formation were kinetically analyzed by NaCl-jump measurements (from 0 to 300 mM at pH 3). Phase diagrams revealed that the domains have different conformational and colloidal stabilities. The unfolded fractions of CH3 and CH2 at pH 3 were larger than that of CL and CH1-CL dimer. The secondary and tertiary structures and particle sizes of CH3 and CH2 showed that, in non-native states, these domains were sensitive to salt concentration. Kinetic analyses suggest that oligomer formation by CH3 and CH2 proceeds through partially refolded conformations. The colloidal stability of CH3 in non-native states is the lowest of the four domains under the conditions tested. We propose that the impact of IgG constant domains on aggregation follows the order CH3 > CH2 > CH1-CL dimer > CL; furthermore, we suggest that CH3 plays the most critical role in driving intact antibody aggregation under acidic conditions.

Suppression of IgM Proteolysis by Conformational Stabilization Through Excipients

Protease activity from host cell lines may cause product loss or affect the quality of recombinant proteins. In this study, we showed that excipients like glycine and sorbitol reduce the proteolysis of an immunoglobulin M (IgM) in the presence of added proteases like α-chymotrypsin, papain, and pepsin. The activity of the proteases in the IgM-protective environments was conserved or even enhanced as tested using low molecular weight substrates. Thus, a higher resistance against proteolytic degradation appears to be caused by the conformational stabilization of the IgM due to preferential exclusion of sorbitol and glycine.

Generation of novel hybrid aptamer-molecularly imprinted polymeric nanoparticles

A strategy to exploit aptamers as recognition elements of molecularly imprinted polymeric nanoparticles (AptaMIP NPs) is presented, via modification of the chemical structure of the DNA. It is demonstrated that the introduction of this modified "aptamer monomer" results in an increase of the affinity of the produced MIP NPs, without altering their physical properties such as size, shape, or dispersibility.