Effect of protein and solution properties on the donnan effect during the ultrafiltration of proteins

Histidine as a versatile excipient in the protein-based biopharmaceutical formulations

Adequate stabilization is essential for marketed protein-based biopharmaceutical formulations to withstand the various stresses that can be exerted during the pre- and post-manufacturing processes. Therefore, a suitable choice of excipient is a significant step in the manufacturing of such delicate products. Histidine, an essential amino acid, has been extensively used in protein-based biopharmaceutical formulations. The physicochemical properties of histidine are unique among amino acids and could afford multifaceted benefits to protein-based biopharmaceutical formulations. With a pKa of approximately 6.0 at the side chain, histidine has been primarily used as a buffering agent, especially for pH 5.5-6.5. Additionally, histidine exhibited several affirmative properties similar to those of carbohydrates (e.g., sucrose and trehalose) and could therefore be considered to be an alternative approach to established protein-based formulation strategies. The current review describes the general physicochemical properties of histidine, lists all commercial histidine-containing protein-based biopharmaceutical products, and discusses a brief outline of the existing research focused on the versatile applications of histidine, which can act as a buffering agent, stabilizer, cryo-/lyo-protectant, antioxidant, viscosity reducer, and solubilizing agent. The interaction between histidine and proteins in protein-based biopharmaceutical formulations, such as the Donnan effect during diafiltration of monoclonal antibody solutions and the degradation of polysorbates in histidine buffer, has also been discussed. As the first review of histidine in protein biopharmaceuticals, it helps to deepen our understanding of the opportunities and challenges associated with histidine as an excipient for protein-based biopharmaceutical formulations.

A modular and multi-functional purification strategy that enables a common framework for manufacturing scale integrated and continuous biomanufacturing

Biopharmaceutical manufacture is transitioning from batch to integrated and continuous biomanufacturing (ICB). The common framework for most ICB, potentially enables a global biomanufacturing ecosystem utilizing modular and multi-function manufacturing equipment. Integrating unit operation hardware and software from multiple suppliers, complex supply chains enabled by multiple customized single-use flow paths, and large volume buffer production/storage make this ICB vision difficult to achieve with commercially available manufacturing equipment. Thus, we developed SymphonX™, a downstream processing skid with advanced buffer management capabilities, a single disposable generic flow path design that provides plug-and-play flexibility across all downstream unit operations and a single interface to reduce operational risk. Designed for multi-product and multi-process cGMP facilities, SymphonX™ can perform stand-alone batch processing or ICB. This study utilized an Apollo™ X CHO-DG44 mAb-expressing cell line in a steady-state perfusion bioreactor, harvesting product continuously with a cell retention device and connected SymphonX™ purification skids. The downstream process used the same chemistry (resins, buffer composition, membrane composition) as our historical batch processing platform, with SymphonX™ in-line conditioning and buffer concentrates. We used surge vessels between unit operations, single-column chromatography (protein A, cation and anion exchange) and two-tank batch virus inactivation. After the first polishing step (cation exchange), we continuously pooled product for 6 days. These 6 day pools were processed in batch-mode from anion exchange to bulk drug substance. This manufacturing scale proof-of-concept ICB produced 0.54 kg/day of drug substance with consistent product quality attributes and demonstrated successful bioburden control for unit-operations undergoing continuous operation.

Combining Scattering Experiments and Colloid Theory to Characterize Charge Effects in Concentrated Antibody Solutions

Charges and their contribution to protein-protein interactions are essential for the key structural and dynamic properties of monoclonal antibody (mAb) solutions. In fact, they influence the apparent molecular weight, the static structure factor, the collective diffusion coefficient, or the relative viscosity, and their concentration dependence. Further, charges play an important role in the colloidal stability of mAbs. There exist standard experimental tools to characterize mAb net charges, such as the measurement of the electrophoretic mobility, the second virial coefficient, or the diffusion interaction parameter. However, the resulting values are difficult to directly relate to the actual overall net charge of the antibody and to theoretical predictions based on its known molecular structure. Here, we report the results of a systematic investigation of the solution properties of a charged IgG1 mAb as a function of concentration and ionic strength using a combination of electrophoretic measurements, static and dynamic light scattering, small-angle X-ray scattering, and tracer particle-based microrheology. We analyze and interpret the experimental results using established colloid theory and coarse-grained computer simulations. We discuss the potential and limits of colloidal models for the description of the interaction effects of charged mAbs, in particular pointing out the importance of incorporating shape and charge anisotropy when attempting to predict structural and dynamic solution properties at high concentrations.

Impact of Excipient Extraction and Buffer Exchange on Recombinant Monoclonal Antibody Stability

The foundation of a biosimilar manufacturer's regulatory filing is the demonstration of analytical and functional similarity between the biosimilar product and the pertinent originator product. The excipients in the formulation may interfere with characterization using typical analytical and functional techniques during this biosimilarity exercise. Consequently, the producers of biosimilar products resort to buffer exchange to isolate the biotherapeutic protein from the drug product formulation. However, the impact that this isolation has on the product stability is not completely known. This study aims to elucidate the extent to which mAb isolation via ultrafiltration-diafiltration-based buffer exchange impacts mAb stability. It has been demonstrated that repeated extraction cycles do result in significant changes in higher-order structure (red-shift of 5.0 nm in fluorescence maxima of buffer exchanged samples) of the mAb and also an increase in formation of basic variants from 19.1 to 26.7% and from 32.3 to 36.9% in extracted innovator and biosimilar Tmab samples, respectively. It was also observed that under certain conditions of tertiary structure disruptions, Tmab could be restabilized depending on formulation composition. Thus, mAb isolation through extraction with buffer exchange impacts the product stability. Based on the observations reported in this paper, we recommend that biosimilar manufacturers take into consideration these effects of excipients on protein stability when performing biosimilarity assessments.

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.

From cell factories to patients: Stability challenges in biopharmaceuticals manufacturing and administration with mitigation strategies

Active ingredients of biopharmaceuticals consist of a wide array of biomolecular structures, including those of enzymes, monoclonal antibodies, nucleic acids, and recombinant proteins. Recently, these molecules have dominated the pharmaceutical industry owing to their safety and efficacy. However, their manufacturing is hindered by high cost, inadequate batch-to-batch equivalence, inherent instability, and other quality issues. This article is an up-to-date review of the challenges encountered during different stages of biopharmaceutical production and mitigation of problems arising during their development, formulation, manufacturing, and administration. It is a broad overview discussion of stability issues encountered during product life cycle i.e., upstream processing (aggregation, solubility, host cell proteins, color change), downstream bioprocessing (aggregation, fragmentation), formulation, manufacturing, and delivery to patients.

Predicting Formulation Conditions During Ultrafiltration and Dilution to Drug Substance Using a Donnan Model with Homology-Model Based Protein Charge

In the manufacturing of therapeutic monoclonal antibodies (mAbs), the final steps of the purification process are typically ultrafiltration/diafiltration (UF/DF), dilution, and conditioning. These steps are developed such that the final drug substance (DS) is formulated to the desired mAb, buffer, and excipient concentrations. To develop these processes, process and formulation development scientists often perform experiments to account for the Gibbs-Donnan and volume-exclusion effects during UF/DF, which affect the output pH and buffer concentration of the UF/DF process. This work describes the development of an in silico model for predicting the DS pH and buffer concentration after accounting for the Gibbs-Donnan and volume-exclusion effects during the UF/DF operation and the subsequent dilution and conditioning steps. The model was validated using statistical analysis to compare model predictions against experimental results for nine molecules of varying protein concentrations and formulations. In addition, our results showed that the structure-based in silico approach used to calculate the protein charge was more accurate than a sequence-based approach. Finally, we used the model to gain fundamental insights about the Gibbs-Donnan effect by highlighting the role of the protein charge concentration (the protein concentration multiplied with protein charge at the formulation pH) on the Gibbs-Donnan effect. Overall, this work demonstrates that the Gibbs-Donnan and volume-exclusions effects can be predicted using an in silico model, potentially alleviating the need for experiments.

Effect of the Tubing Material Used in Peristaltic Pumping in Tangential Flow Filtration Processes of Biopharmaceutics on Particle Formation and Flux

Tangential flow filtration (TFF) is a central step in manufacturing of biopharmaceutics. Membrane clogging leads to decreased permeate flux, longer process time and potentially complete failure of the process. The effect of peristaltic pumping with tubings made of three different materials on protein particle formation during TFF was monitored via micro flow imaging, turbidity and photo documentation. At low protein concentrations, pumping with a membrane pump resulted in a stable flux with low protein particle concentration. Using a peristaltic pump led to markedly higher protein particle formation dependent on tubing type. With increasing protein particle formation propensity of the tubing, the permeate flux rate became lower and the process took longer. The protein particles formed in the pump were captured in the cassette and accumulated on the membrane leading to blocking. Using tubing with a hydrophilic copolymer modification counteracted membrane clogging and flux decrease by reducing protein particle formation. In ultrafiltration mode the permeate flux decrease was governed by the viscosity increase rather than by the protein aggregation; but using modified tubing is still beneficial due to a lower particle burden of the product. In summary, using tubing material for peristaltic pumping in TFF processes which leads a less protein particle formation, especially tubing material with hydrophilic modification, is highly beneficial for membrane flux and particle burden of the product.

Succinate Buffer in Biologics Products: Real-world Formulation Considerations, Processing Risks and Mitigation Strategies

The succinic acid/succinate system has an excellent buffering capacity at acidic pH values (4.5-6.0), promising to be a buffer of choice for biologics having slightly acidic to basic isoelectric points (pI 6 - 9). However, its prevalence in drug products is limited due to the propensity (risk) of its components to crystallize during freezing and the consequent shift in the pH which might affect the product stability. Most of these previous assessments have been performed under operational conditions that do not simulate typical drug product processing conditions. In this work, we have characterized the physicochemical behavior of succinate formulations under representative pharmaceutical conditions. Our results indicate that the pH increases by ∼ 1.2 units in 25 mM and 250 mM succinate buffers at pharmaceutically relevant freezing conditions. X-ray diffractometry studies revealed selective crystallization of monosodium succinate, which is posed as the causative mechanism. This salt crystallization was not observed in the presence of 2% w/v sucrose, suggesting that this pH shift can be mitigated by including sucrose in the formulation. Additionally, three monoclonal antibodies (mAbs) that represent different IgG subtypes and span a range of pIs (5.9 - 8.8) were formulated with succinate and sucrose and subjected to freeze-thaw, frozen storage and lyophilization. No detrimental impact on quality attributes (QA) such as high molecular weight (HMW) species, turbidity, alteration in protein concentration and sub-visible particles, was observed of any of the mAbs tested. Lastly, drug formulations lyophilized in succinate buffer with sucrose demonstrated acceptable QA profiles upon accelerated kinetic storage stability, supporting the use of succinate buffers in mAb drug products.

Albumins as Extracellular Protein Nanoparticles Collaborate with Plasma Ions to Control Biological Osmotic Pressure

Introduction

Plasma albumins as protein nanoparticles (PNs) exert essential functions in the control of biological osmotic pressure (OP), being involved in regulating water metabolism, cell morphology and cell tension. Understanding how plasma albumins and different electrolytes co-determine biological OP effects is crucial for correct interpretation of hemodynamic disorders, and practical treatment of hypo/hyper-proteinemia.

Methods

Optical measurement based on intermediate filament (IF) tension probe was used for real-time evaluation of transmembrane osmotic effects in live cells. Ion fluorescent probes were employed to evaluate intracellular ion levels, and a current clamp was used to measure membrane potential, thus exploring association of electrochemical and osmotic effects.

Results

Albumins are involved in regulation of intracellular osmolarity by a quantitative relationship. Extracellular PNs can alter membrane potentials by adsorbing counterions, induce production of intracellular PNs and further control the opening of ion channels and ion flow, contributing to electrochemical and osmotic re-equilibrium. Furthermore, various ions interplay with extracellular PNs, showing different osmotic effects: increased levels of calcium ions result in a hypotonic effect, whereas potassium ions induce hyper-osmolarity.

Conclusion

Extracellular PNs and Ca²⁺/K⁺ display antagonistic or synergetic effects in regulating biological OP. Live cells can spontaneously regulate osmotic effects through changing membrane potential and controlling intracellular ion content. Various plasma components need to be comprehensively analyzed, further developing a diagnostic index that considers the biological OP effects of various blood components and improves the evaluation of symptoms and diseases, such as calcium/potassium-hemodynamic disorders and edema.

Procedure providing SI-traceable results for the calibration of protein standards by sulfur determination and its application on tau

Quantitative proteomics is a growing research area and one of the most important tools in the life sciences. Well-characterized and quantified protein standards are needed to achieve accurate and reliable results. However, only a limited number of sufficiently characterized protein standards are currently available. To fill this gap, a method for traceable protein quantification using sulfur isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) was developed in this study. Gel filtration and membrane filtration were tested for the separation of non-protein-bound sulfur in the protein solution. Membrane filtration demonstrated a better performance due to the lower workload and the very low sulfur blanks of 11 ng, making it well suited for high-purity proteins such as NIST SRM 927, a bovine serum albumin (BSA). The method development was accomplished with NIST SRM 927e and a commercial avidin. The quantified mass fraction of NIST SRM 927e agreed very well with the certified value and showed similar uncertainties (3.6%) as established methods while requiring less sample preparation and no species-specific standards. Finally, the developed procedure was applied to the tau protein, which is a biomarker for a group of neurodegenerative diseases denoted “tauopathies” including, e.g., Alzheimer’s disease and frontotemporal dementia. For the absolute quantification of tau in the brain of transgenic mice overexpressing human tau, a well-defined calibration standard was needed. Therefore, a pure tau solution was quantified, yielding a protein mass fraction of (0.328 ± 0.036) g/kg, which was confirmed by amino acid analysis.

Inflammasome-Induced Osmotic Pressure and the Mechanical Mechanisms Underlying Astrocytic Swelling and Membrane Blebbing in Pyroptosis

Cell swelling and membrane blebbing are characteristic of pyroptosis. In the present study, we explored the role of intracellular tension activity in the deformation of pyroptotic astrocytes. Protein nanoparticle-induced osmotic pressure (PN-OP) was found to be involved in cell swelling and membrane blebbing in pyroptotic astrocytes, and was associated closely with inflammasome production and cytoskeleton depolymerization. However, accumulation of protein nanoparticles seemed not to be absolutely required for pyroptotic permeabilization in response to cytoskeleton depolymerization. Gasdermin D activation was observed to be involved in modification of typical pyroptotic features through inflammasome-induced OP upregulation and calcium increment. Blockage of nonselective ion pores can inhibit permeabilization, but not inflammasome production and ion influx in pyroptotic astrocytes. The results suggested that the inflammasomes, as protein nanoparticles, are involved in PN-OP upregulation and control the typical features of pyroptotic astrocytes.

Process analytical technology for on-line monitoring of quality attributes during single-use ultrafiltration/diafiltration

Process analytical technology (PAT) is a fast-growing field within bioprocessing that enables innovation in biological drug manufacturing. This study demonstrates novel PAT methods for monitoring multiple quality attributes simultaneously during the ultrafiltration and diafiltration (UF/DF) process operation, the final step of monoclonal antibody (mAb) purification. Size exclusion chromatography (SEC) methods were developed to measure excipients arginine, histidine, and high molecular weight (HMW) species using a liquid chromatography (LC) system with autosampler for both on-line and at-line PAT modes. The methods were applied in UF/DF studies for the comparison of single-use tangential flow filtration (TFF) cassettes to standard reusable cassettes to achieve very high concentration mAb drug substance (DS) in the order of 100-200 g/L. These case studies demonstrated that single-use TFF cassettes are a functionally equivalent, low-cost alternative to standard reusable cassettes, and that the on-line PAT measurement of purity and excipient concentration was comparable to orthogonal offline methods. These PAT applications using an on-line LC system equipped with onboard sample dilution can become a platform system for monitoring of multiple attributes over a wide dynamic range, a potentially valuable tool for biological drug development and manufacturing.

A mechanistic model to account for the Donnan and volume exclusion effects in ultrafiltration/diafiltration process of protein formulations

Ultrafiltration/diafiltration (UF/DF) is a typical step in protein drug manufacturing process to concentrate and exchange the protein solution into a desired formulation. However, significant offset of pH and composition from the target formulation have been frequently observed after UF/DF, posing challenges to the stability, performance, and consistency of the final drug product. Such shift can often be attributed to the Donnan and volume exclusion effects. In order to predict and compensate for those effects, a mechanistic model is developed based on the protein charge, mass and charge balances, as well as the equilibrium condition across the membrane. The integrated UF/DF model can be used to predict both the dynamic behavior and the final outcome of the process. Examples of the modeling results for the pH and composition variation during the UF/DF operations are presented for two monoclonal antibody proteins. The model predictions are in good agreement with a comprehensive experimental data set that covers different process steps, protein concentrations, solution matrices, and process scales. The results show that significant pH and excipient concentration shifts are more likely to occur for high protein concentration and low ionic strength matrices. As a special example, a self-buffering protein formulation shows unique pH behavior during DF, which could also be captured with the dynamic model. The capability of the model in predicting the performance of UF/DF process as a function of protein characteristics and formulation conditions makes it a useful tool to improve process understanding and facilitate process development.

Designing scalable ultrafiltration/diafiltration process of monoclonal antibodies via mathematical modeling by coupling mass balances and Poisson-Boltzmann equation

Ultrafiltration/diafiltration (UF/DF) operations are employed for achieving the desired therapeutic monoclonal antibody (mAb) formulations. Due to electrostatic interactions between the charged proteins, solute ions, and uncharged excipients, the final pH and concentration values are not always equal to those in the DF buffer. At high protein concentrations, typical for industrial formulations, this effect becomes predominant. To account for challenges occurring in industrial environments, a robust mathematical framework enabling the prediction of pH and concentration profiles throughout the UF/DF process is provided. The proposed mechanistic model combines a macroscopic mass balance approach with a molecular approach based on a Poisson-Boltzmann equation dealing with electrostatic interactions and accounting for protein exclusion volume effect. The mathematical model was validated with experimental data of two commercially relevant mAbs obtained from an industrial UF/DF process using scalable laboratory equipment. The robustness and flexibility of the model were tested by using proteins with different isoelectric points and net charges. The latter was determined via a titration curve, enabling realistic protein charge-pH evaluation. In addition, the model was tested for different DF buffer types containing both monovalent and polyvalent ions, with various types of uncharged excipients. The model generality enables its implementation for the UF/DF processes of other protein varieties.

Ice-templating of chitosan/agarose porous composite hydrogel with adjustable water-sensitive shape memory property and multi-staged degradation performance

Water-induced shape memory polymers (SMPs) may have important applications in the fields of tissue engineering and biomedicine. However, most of the ideal candidates often suffer from non-biodegradation, weak mechanical strength and random macro-porous structure, which do limit the creativity and dynamism of water-sensitive SPMs. To address above issue, in this study, by incorporating the pH-responsive chitosan (CHIT) into a thermoplastic elastomer agarose (Agar) matrix and ice-templating, a novel dual-responsive interpenetrating polymer network hydrogel with highly porous structure was facilely prepared, which has a ultra-high porosity (>95 %) and water-induced shape recovery ratio (>90 %, response time <1 min). Results showed that such shape memory property is erasable and pH-dependent which achieves a great shape memory property at high pH and then can be erased in acidic condition. In vitro dissolution test indicates the great possibility of programming the multi-staged degradation of such composites in response to sequential pH or thermal stimuli. Based on the porous internal structure, we also demonstrate some potential applications of the hydrogels for assembly of nanomaterials, such as Au nanorods for remote sensing system and model protein of insulin for drug controlled release. Moreover, the process proved to be versatile, allowing the use of most natural polymer including gelatin, alginate, and so on. Thus, coupling of such straightforward fabrication approach, multifunctionality and biodegradable prerequisite feature indicates great potential for use in the minimally invasive surgery.

Downstream Processing Technologies/Capturing and Final Purification : Opportunities for Innovation, Change, and Improvement. A Review of Downstream Processing Developments in Protein Purification

Increased pressure on upstream processes to maximize productivity has been crowned with great success, although at the cost of shifting the bottleneck to purification. As drivers were economical, focus is on now on debottlenecking downstream processes as the main drivers of high manufacturing cost. Devising a holistically efficient and economical process remains a key challenge. Traditional and emerging protein purification strategies with particular emphasis on methodologies implemented for the production of recombinant proteins of biopharmaceutical importance are reviewed. The breadth of innovation is addressed, as well as the challenges the industry faces today, with an eye to remaining impartial, fair, and balanced. In addition, the scope encompasses both chromatographic and non-chromatographic separations directed at the purification of proteins, with a strong emphasis on antibodies. Complete solutions such as integrated USP/DSP strategies (i.e., continuous processing) are discussed as well as gains in data quantity and quality arising from automation and high-throughput screening (HTS). Best practices and advantages through design of experiments (DOE) to access a complex design space such as multi-modal chromatography are reviewed with an outlook on potential future trends. A discussion of single-use technology, its impact and opportunities for further growth, and the exciting developments in modeling and simulation of DSP rounds out the overview. Lastly, emerging trends such as 3D printing and nanotechnology are covered. Graphical Abstract Workflow of high-throughput screening, design of experiments, and high-throughput analytics to understand design space and design space boundaries quickly. (Reproduced with permission from Gregory Barker, Process Development, Bristol-Myers Squibb).

ZWIĄZKI WIĄŻĄCE SIĘ Z BIAŁKAMI OSOCZA U LUDZI. ZNACZENIE W TERAPII ORAZ METODY OZNACZANIA WOLNEJ FRAKCJI

Wiele substancji endogennych oraz egzogennych wykazuje zdolność do wiązania się z białkami osocza, głównie z ludzką albuminą surowicy oraz α-1-kwaśną glikoproteiną. Substancje te w krwioobiegu występują zarówno w formie wolnej jak i związanej z białkami. Białko posiada na swojej powierzchni miejsca wiązania charakterystyczne dla danego związku, różniące się wielkością, kształtem oraz powinowactwem. Wiązanie z białkami następuje w wyniku oddziaływań hydrofobowych, van der Waalsa oraz elektrostatycznych. Stopień związania z białkami osocza zależy od m.in. obecności stanu zapalnego, występowania chorób nerek i wątroby oraz wieku. Jedynie forma wolna związku jest aktywna biologicznie oraz jest zdolna do pokonywania barier biologicznych. W związku z tym duże znaczenie mają metody pomiaru stężenia frakcji niezwiązanej z białkami w osoczu. Najczęściej stosowana jest dializa równowagowa, uznawana za metodę referencyjną. Inne metody to m.in. ultrafiltracja, ultrawirowanie, mikrodializa, mikroekstrakcja, wysokosprawna analiza czołowa oraz ekstrakcja w punkcie zmętnienia.

Rational design of viscosity reducing mutants of a monoclonal antibody: hydrophobic versus electrostatic inter-molecular interactions

High viscosity of monoclonal antibody formulations at concentrations ≥100 mg/mL can impede their development as products suitable for subcutaneous delivery. The effects of hydrophobic and electrostatic intermolecular interactions on the solution behavior of MAB 1, which becomes unacceptably viscous at high concentrations, was studied by testing 5 single point mutants. The mutations were designed to reduce viscosity by disrupting either an aggregation prone region (APR), which also participates in 2 hydrophobic surface patches, or a negatively charged surface patch in the variable region. The disruption of an APR that lies at the interface of light and heavy chain variable domains, VH and VL, via L45K mutation destabilized MAB 1 and abolished antigen binding. However, mutation at the preceding residue (V44K), which also lies in the same APR, increased apparent solubility and reduced viscosity of MAB 1 without sacrificing antigen binding or thermal stability. Neutralizing the negatively charged surface patch (E59Y) also increased apparent solubility and reduced viscosity of MAB 1, but charge reversal at the same position (E59K/R) caused destabilization, decreased solubility and led to difficulties in sample manipulation that precluded their viscosity measurements at high concentrations. Both V44K and E59Y mutations showed similar increase in apparent solubility. However, the viscosity profile of E59Y was considerably better than that of the V44K, providing evidence that inter-molecular interactions in MAB 1 are electrostatically driven. In conclusion, neutralizing negatively charged surface patches may be more beneficial toward reducing viscosity of highly concentrated antibody solutions than charge reversal or aggregation prone motif disruption.

Concentration dependent viscosity of monoclonal antibody solutions: explaining experimental behavior in terms of molecular properties

PURPOSE

Early identification of monoclonal antibody candidates whose development, as high concentration (≥100 mg/mL) drug products, could prove challenging, due to high viscosity, can help define strategies for candidate engineering and selection.

METHODS

Concentration dependent viscosities of 11 proprietary mAbs were measured. Sequence and structural features of the variable (Fv) regions were analyzed to understand viscosity behavior of the mAbs. Coarse-grained molecular simulations of two problematic mAbs were compared with that of a well behaved mAb.

RESULTS

Net charge, ξ-potential and pI of Fv regions were found to correlate with viscosities of highly concentrated antibody solutions. Negative net charges on the Fv regions of two mAbs with poor viscosity behaviors facilitate attractive self-associations, causing them to diffuse slower than a well-behaved mAb with positive net charge on its Fv region. An empirically derived equation that connects aggregation propensity and pI of the Fv region with high concentration viscosity of the whole mAb was developed.

CONCLUSIONS

An Fv region-based qualitative screening profile was devised to flag mAb candidates whose development, as high concentration drug products, could prove challenging. This screen can facilitate developability risk assessment and mitigation strategies for antibody based therapeutics via rapid high throughput material-free screening.

Efforts toward broadening the spectrum of arylomycin antibiotic activity

New antibiotics are needed, and one source may be 'latent' antibiotics, natural products whose once broad-spectrum activity is currently limited by the evolution of resistance in nature. We have identified a potential class of latent antibiotics, the arylomycins, which are lipopeptides with a C-terminal macrocycle that target signal peptidase and whose spectrum is limited by a resistance-conferring mutation in many bacteria. Herein, we report the synthesis and evaluation of several arylomycin derivatives, and demonstrate that both C-terminal homologation with a glycyl aldehyde and addition of a positive charge to the macrocycle increase the activity and spectrum of the arylomycin scaffold.

Viscosity behavior of high-concentration monoclonal antibody solutions: correlation with interaction parameter and electroviscous effects

The purpose of this work was to understand the viscosity behavior of high-concentration monoclonal antibody (mAb) solutions in a wide range of solution conditions and generate guidelines helpful to formulate products with manageable viscosity. The zeta potential and effective isoelectric point (pI) were determined from electrophoretic mobility measurements. High-frequency rheology studies characterized viscoelasticity at high concentrations. The interaction parameter (k(D) ) obtained from dynamic light scattering quantified intermolecular interactions. Circular dichroism characterized conformational stability upon change in solution pH. Except for mAb-1, all other mAb solutions were found to be more viscous at solution pHs closer to the molecular pI. For mAb-2, mAb-3, and mAb-10,the k(D) indicated intermolecular attractions at the pI, wherein the net molecular charge (Z) was zero, whereas repulsions dominated at pHs away from the pI. At the pI, Z and, hence, the charge-induced repulsions are minimal, whereas the charge distribution becomes most conspicuous. The resulting dominance of nonspecific attractive interactions at the pI increases the self-association or aggregation behavior of protein molecules, leading to a higher viscosity at the pI. mAb-1 is an exception to this general behavior. The k(D) could serve as a qualitative screening tool to predict high-concentration viscosity behavior, whereas the correlation with net charge was inconsistent. A higher negative k(D) generally resulted in a more viscous solution at high concentrations; however, direct quantitative assessment was not possible.

Protein-excipient interactions: mechanisms and biophysical characterization applied to protein formulation development

The purpose of this review is to demonstrate the critical importance of understanding protein-excipient interactions as a key step in the rational design of formulations to stabilize and deliver protein-based therapeutic drugs and vaccines. Biophysical methods used to examine various molecular interactions between solutes and protein molecules are discussed with an emphasis on applications to pharmaceutical excipients in terms of their effects on protein stability. Key mechanisms of protein-excipient interactions such as electrostatic and cation-pi interactions, preferential hydration, dispersive forces, and hydrogen bonding are presented in the context of different physical states of the formulation such as frozen liquids, solutions, gels, freeze-dried solids and interfacial phenomenon. An overview of the different classes of pharmaceutical excipients used to formulate and stabilize protein therapeutic drugs is also presented along with the rationale for use in different dosage forms including practical pharmaceutical considerations. The utility of high throughput analytical methodologies to examine protein-excipient interactions is presented in terms of expanding formulation design space and accelerating experimental timelines.