Developments and Challenges for mAb-Based Therapeutics

Emerging trends and therapeutic applications of monoclonal antibodies

Monoclonal antibodies (mAbs) are being used to prevent, detect, and treat a broad spectrum of malignancies and infectious and autoimmune diseases. Over the past few years, the market for mAbs has grown exponentially. They have become a significant part of many pharmaceutical product lines, and more than 250 therapeutic mAbs are undergoing clinical trials. Ever since the advent of hybridoma technology, antibody-based therapeutics were realized using murine antibodies which further progressed into humanized and fully human antibodies, reducing the risk of immunogenicity. Some of the benefits of using mAbs over conventional drugs include a drastic reduction in the chances of adverse reactions, interactions between drugs, and targeting specific proteins. While antibodies are very efficient, their higher production costs impede the process of commercialization. However, their cost factor has been improved by developing biosimilar antibodies, which are affordable versions of therapeutic antibodies. Along with biosimilars, innovations in antibody engineering have helped to design bio-better antibodies with improved efficacy than the conventional ones. These novel mAb-based therapeutics are set to revolutionize existing drug therapies targeting a wide spectrum of diseases, thereby meeting several unmet medical needs. In the future, mAbs generated by applying next-generation sequencing (NGS) are expected to become a powerful tool in clinical therapeutics. This article describes the methods of mAb production, pre-clinical and clinical development of mAbs, approved indications targeted by mAbs, and novel developments in the field of mAb research.

Engineered polymeric excipients for enhancing the stability of protein biologics: Poly(N-isopropylacrylamide)-poly(ethylene glycol) (PNIPAM-PEG) block copolymers

Protein therapeutics, particularly antibodies, depend on maintaining their native structures for optimal function. Hydrophobic interfaces, such as the air-water interface, can trigger protein aggregation and denaturation. While completely avoiding such interfacial exposures during manufacturing and storage is impractical, minimizing them is crucial for enhancing protein drug stability and extending shelf life. In the biologics industry, surfactants like polysorbates are commonly used as additives (excipients) to mitigate these undesirable interfacial exposures. However, polysorbates, the most prevalent choice, have recognized limitations in terms of polydispersity, purity, and stability, prompting the exploration of alternative excipients. The present study identifies poly(N-isopropylacrylamide)-poly(ethylene glycol) (PNIPAM-PEG) block copolymers as a promising alternative to polysorbates. Due to its stronger affinity for the air-water interface, PNIPAM-PEG significantly outperforms polysorbates in enhancing protein stability. This claim is supported by results from multiple tests. Accelerated dynamic light scattering (DLS) experiments demonstrate PNIPAM-PEG's exceptional efficacy in preserving IgG stability against surface-induced aggregation, surpassing conventional polysorbate excipients (Tween 80 and Tween 20) under high-temperature conditions. Additionally, circular dichroism (CD) spectroscopy results reveal conformational alterations associated with aggregation, with PNIPAM-PEG consistently demonstrates a greater protective effect by mitigating negative shifts at λ ≅ 220 nm, indicative of changes in secondary structure. Overall, this study positions PNIPAM-PEG as a promising excipient for antibody therapeutics, facilitating the development of more stable and effective biopharmaceuticals.

Parainfluenza Virus 5 V Protein Blocks Interferon Gamma-Mediated Upregulation of NK Cell Inhibitory Ligands and Improves NK Cell Killing of Neuroblastoma Cells

Natural killer (NK) cells can be effective immunotherapeutic anti-cancer agents due to their ability to selectively target and kill tumor cells. This activity is modulated by the interaction of NK cell receptors with inhibitory ligands on the surface of target cells. NK cell inhibitory ligands can be upregulated on tumor cell surfaces in response to interferon-gamma (IFN-γ), a cytokine which is produced by activated NK cells. We hypothesized that the resistance of tumor cells to NK cell killing could be overcome by expression of the parainfluenza virus 5 (PIV5) V protein, which has known roles in blocking IFN-γ signaling. This was tested with human PM21-NK cells produced through a previously developed particle-based method which yields superior NK cells for immunotherapeutic applications. Infection of human SK-N-SH neuroblastoma cells with PIV5 blocked IFN-γ-mediated upregulation of three NK cell inhibitory ligands and enhanced in vitro killing of these tumor cells by PM21-NK cells. SK-N-SH cells transduced to constitutively express the V protein alone were resistant to IFN-γ-mediated increases in cell surface expression of NK cell inhibitory ligands. Real-time in vitro cell viability assays demonstrated that V protein expression in SK-N-SH cells was sufficient to increase PM21-NK cell-mediated killing. Toward a potential therapeutic application, transient lentiviral delivery of the V gene also enhanced PM21-NK cell killing in vitro. Our results provide the foundation for novel therapeutic applications of V protein expression in combination with ex vivo NK cell therapy to effectively increase the killing of tumor cells.

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.'

Investigation on the Combined Effect of Hydroxypropyl Beta-Cyclodextrin (HPβCD) and Polysorbate in Monoclonal Antibody Formulation

Monoclonal antibodies require careful formulation due to their inherent stability limitations. Polysorbates are commonly used to stabilize mAbs, but they are prone to degradation, which results in unwanted impurities. KLEPTOSE® HPβCD (hydroxypropyl beta-cyclodextrin) has functioned as a stable stabilizer for protein formulations in our previous research. The current study investigates the collaborative impact of combining polysorbates and HPβCD as excipients in protein formulations. The introduction of HPβCD in formulations showed it considerably reduced aggregation in two model proteins, bevacizumab and ipilimumab, following exposure to various stress conditions. The diffusion interaction parameter revealed a reduction in protein-protein interactions by HPβCD. In bevacizumab formulations, the subvisible particle counts per 0.4 mL of samples in commercial formulations vs. formulations containing both HPβCD and polysorbates subjected to distinct stressors were as follows: agitation, 87,308 particles vs. 15,350 particles; light, 25,492 particles vs. 6765 particles; and heat, 1775 particles vs. 460 particles. Isothermal titration calorimetry (ITC) measurement indicated a weak interaction between PS 80 and HPβCD, with a KD value of 74.7 ± 7.5 µM and binding sites of 5 × 10-3. Surface tension measurements illustrated that HPβCD enhanced the surface activity of polysorbates. The study suggests that combining these excipients can improve mAb stability in formulations, offering an alternative for the biopharmaceutical industry.

High-throughput untargeted screening of biotherapeutic macromolecules in equine plasma by UHPLC-HRMS/MS: Application to monoclonal antibodies and Fc-fusion proteins for doping control

Many innovative biotherapeutics have been marketed in the last decade. Monoclonal antibodies (mAbs) and Fc-fusion proteins (Fc-proteins) have been developed for the treatment of diverse diseases (cancer, autoimmune diseases, and inflammatory disorders) and now represent an important part of targeted therapies. However, the ready availability of such biomolecules, sometimes characterized by their anabolic, anti-inflammatory, or erythropoiesis-stimulating properties, raises concerns about their potential misuse as performance enhancers for human and animal athletes. In equine doping control laboratories, a method has been reported to detect the administration of a specific human biotherapeutic in equine plasma; but no high-throughput method has been described for the screening without any a priori knowledge of human or murine biotherapeutic. In this context, a new broad-spectrum screening method involving UHPLC-HRMS/MS has been developed for the untargeted analysis of murine or human mAbs and related macromolecules in equine plasma. This approach, consisting of a "pellet digestion" strategy performed in a 96-well plate, demonstrates reliable performances at low concentrations (pmol/mL range) with high-throughput capability (≈100 samples/day). Targeting species-specific proteotypic peptides located within the constant parts of mAbs enables the "universal" detection of human biotherapeutics only by monitoring 10 peptides. As proof of principle, this strategy successfully detected different biotherapeutics in spiked plasma samples, and allowed, for the first time, the detection of a human mAb up to 10 days after a 0.12 mg/kg administration to a horse. This development will expand the analytical capabilities of horse doping control laboratories towards protein-based biotherapeutics with adequate sensitivity, throughput, and cost-effectiveness.

Continuous monitoring of a monoclonal antibody by size exclusion chromatography reveals a correlation between system suitability parameters and column aging

Size exclusion chromatography (SEC) is a foundational analytical method to assess product purity of biological molecules. To ensure accurate and reproducible data that meet regulatory agency standards, it is critical to monitor the chromatographic column with efficient and continuous approaches. In this study, 19 SEC columns (Waters Acquity BEH200) were evaluated using an in-house monoclonal antibody made at Regeneron. System suitability parameters (SSPs) were used to monitor the performance of the SEC assay, including USP resolution, USP plate count, USP tailing factor, asymmetry factor, elution time, peak width, and peak height. A general linear model was built and revealed that elution time, peak width, asymmetry factor, and tailing factor increased with injection number, while peak height, resolution, and plate count decreased. After 1000 injections, tailing factor and peak width increased by more than 10%, while resolution and plate count decreased by more than 10% from their respective starting values.

Development and Biophysical Characterization of a Humanized FSH-Blocking Monoclonal Antibody Therapeutic Formulated at an Ultra-High Concentration

Highly concentrated antibody formulations are oftentimes required for subcutaneous, self-administered biologics. Here, we report the creation of a unique formulation for our first-in- class FSH-blocking humanized antibody, MS-Hu6, which we propose to move to the clinic for osteoporosis, obesity, and Alzheimer's disease. The studies were carried out using our Good Laboratory Practice (GLP) platform, compliant with the Code of Federal Regulations (Title 21, Part 58). We first used protein thermal shift, size exclusion chromatography, and dynamic light scattering to examine MS-Hu6 concentrations between 1 and 100 mg/mL. We found that thermal, monomeric, and colloidal stability of formulated MS-Hu6 was maintained at a concentration of 100 mg/mL. The addition of the antioxidant L-methionine and chelating agent disodium EDTA improved the formulation's long-term colloidal and thermal stability. Thermal stability was further confirmed by Nano differential scanning calorimetry (DSC). Physiochemical properties of formulated MS-Hu6, including viscosity, turbidity, and clarity, conformed with acceptable industry standards. That the structural integrity of MS-Hu6 in formulation was maintained was proven through Circular Dichroism (CD) and Fourier Transform Infrared (FTIR) spectroscopy. Three rapid freeze-thaw cycles at -80°C/25°C or -80°C/37°C further revealed excellent thermal and colloidal stability. Furthermore, formulated MS-Hu6, particularly its Fab domain, displayed thermal and monomeric storage stability for more than 90 days at 4°C and 25°C. Finally, the unfolding temperature (T _m ) for formulated MS-Hu6 increased by >4.80°C upon binding to recombinant FSH, indicating highly specific ligand binding. Overall, we document the feasibility of developing a stable, manufacturable and transportable MS-Hu6 formulation at a ultra-high concentration at industry standards. The study should become a resource for developing biologic formulations in academic medical centers.

Monoclonal antibody and protein therapeutic formulations for subcutaneous delivery: high-concentration, low-volume vs. low-concentration, high-volume

Biologic drugs are used to treat a variety of cancers and chronic diseases. While most of these treatments are administered intravenously by trained healthcare professionals, a noticeable trend has emerged favoring subcutaneous (SC) administration. SC administration of biologics poses several challenges. Biologic drugs often require higher doses for optimal efficacy, surpassing the low volume capacity of traditional SC delivery methods like autoinjectors. Consequently, high concentrations of active ingredients are needed, creating time-consuming formulation obstacles. Alternatives to traditional SC delivery systems are therefore needed to support higher-volume biologic formulations and to reduce development time and other risks associated with high-concentration biologic formulations. Here, we outline key considerations for SC biologic drug formulations and delivery and explore a paradigm shift: the flexibility afforded by low-to-moderate-concentration drugs in high-volume formulations as an alternative to the traditionally difficult approach of high-concentration, low-volume SC formulation delivery.

The Impact of Nanobody Density on the Targeting Efficiency of PEGylated Liposomes

Nanoparticles (NPs) are commonly modified with tumor-targeting moieties that recognize proteins overexpressed on the extracellular membrane to increase their specific interaction with target cells. Nanobodies (Nbs), the variable domain of heavy chain-only antibodies, are a robust targeting ligand due to their small size, superior stability, and strong binding affinity. For the clinical translation of targeted Nb-NPs, it is essential to understand how the number of Nbs per NP impacts the receptor recognition on cells. To study this, Nbs targeting the hepatocyte growth factor receptor (MET-Nbs) were conjugated to PEGylated liposomes at a density from 20 to 800 per liposome and their targeting efficiency was evaluated in vitro. MET-targeted liposomes (MET-TLs) associated more profoundly with MET-expressing cells than non-targeted liposomes (NTLs). MET-TLs with approximately 150-300 Nbs per liposome exhibited the highest association and specificity towards MET-expressing cells and retained their targeting capacity when pre-incubated with proteins from different sources. Furthermore, a MET-Nb density above 300 Nbs per liposome increased the interaction of MET-TLs with phagocytic cells by 2-fold in ex vivo human blood compared to NTLs. Overall, this study demonstrates that adjusting the MET-Nb density can increase the specificity of NPs towards their intended cellular target and reduce NP interaction with phagocytic cells.

Identification of amyloid antibodies for Alzheimer disease - immunotherapy

The current study identified the specific antibodies that recognise amyloid protein for Alzheimer disease - immunotherapy. The immune-selection of random sequences from a phage display library and sequencing to obtain the random 12 amino acids peptide library for each antibody, and then we analysed these peptides for unique and common sequences, relation to Aβ42 sequence and shape and pattern of the amino acid reaction to the antibody to predict the epitopes. Data obtained for 4G8 showed that, the sequence segment related to the putative epitope of 4G8 was LVFFAED. Nine of the ten top sequences contain the sequence RHD corresponding to the Aβ sequence from residues 5-7. Peptide 7 has the sequence IRYDTGSYHIH, which has a RYD. It was concluded that, 4G8 and 6E10 can tolerate the binding the sequences that explain it is able to recognise amyloid aggregates.

FSH-blocking therapeutic for osteoporosis

Pharmacological and genetic studies over the past decade have established the follicle-stimulating hormone (FSH) as an actionable target for diseases affecting millions, namely osteoporosis, obesity, and Alzheimer's disease. Blocking FSH action prevents bone loss, fat gain, and neurodegeneration in mice. We recently developed a first-in-class, humanized, epitope-specific FSH-blocking antibody, MS-Hu6, with a KD of 7.52 nM. Using a Good Laboratory Practice (GLP)-compliant platform, we now report the efficacy of MS-Hu6 in preventing and treating osteoporosis in mice and parameters of acute safety in monkeys. Biodistribution studies using 89Zr-labeled, biotinylated or unconjugated MS-Hu6 in mice and monkeys showed localization to bone and bone marrow. The MS-Hu6 displayed a β phase t½ of 7.5 days (180 hr) in humanized Tg32 mice. We tested 217 variations of excipients using the protein thermal shift assay to generate a final formulation that rendered MS-Hu6 stable in solution upon freeze-thaw and at different temperatures, with minimal aggregation, and without self-, cross-, or hydrophobic interactions or appreciable binding to relevant human antigens. The MS-Hu6 showed the same level of "humanness" as human IgG1 in silico and was non-immunogenic in ELISpot assays for IL-2 and IFN-γ in human peripheral blood mononuclear cell cultures. We conclude that MS-Hu6 is efficacious, durable, and manufacturable, and is therefore poised for future human testing.

An Overview on the Recent Advances in Alternative Solvents as Stabilizers of Proteins and Enzymes

Currently, the use of alternative solvents is increasing, namely ionic liquids (ILs) and deep eutectic solvents (DESs) in diverse fields of knowledge, such as biochemistry, chemistry, chemical engineering, biotechnology and biomedicine. Particularly, when compared to traditional solvents, these alternative solvents have great importance for biomolecules due to the enhanced solubility, structure stability and the biological activity of biomolecules, such as protein and enzymes. Thus, in this review article, the recent developments and efforts on the technological developments carried out with ILs and DESs for the stabilization and activation of proteins and enzymes are provided. The most studied IL- and DES-based formulations for proteins and enzymes are discussed and the molecular mechanisms and interactions related to the increased stability promoted by these alternative solvents are disclosed, while emphasizing their main advantages.

Progress and challenges for the machine learning-based design of fit-for-purpose monoclonal antibodies

Although the therapeutic efficacy and commercial success of monoclonal antibodies (mAbs) are tremendous, the design and discovery of new candidates remain a time and cost-intensive endeavor. In this regard, progress in the generation of data describing antigen binding and developability, computational methodology, and artificial intelligence may pave the way for a new era of in silico on-demand immunotherapeutics design and discovery. Here, we argue that the main necessary machine learning (ML) components for an in silico mAb sequence generator are: understanding of the rules of mAb-antigen binding, capacity to modularly combine mAb design parameters, and algorithms for unconstrained parameter-driven in silico mAb sequence synthesis. We review the current progress toward the realization of these necessary components and discuss the challenges that must be overcome to allow the on-demand ML-based discovery and design of fit-for-purpose mAb therapeutic candidates.

Spray layering of human immunoglobulin G: Optimization of formulation and process parameters

Spray layering is a technique used to apply drug or functional polymers onto carrier beads; in addition, it can be used as an alternative method for protein drying and to layer protein on a multiparticulate delivery system. In this study, the effects of formulation variables and process parameters on human immunoglobulin G (IgG) properties during spray layering were studied. Excipients including polyvinylpyrrolidone (PVP), trehalose, sucrose, L-arginine monohydrochloride were studied for their effects on improving IgG stability during spray layering. Process parameters including protein solution feed rate, inlet air temperature, inlet air flow rate, and atomization pressure of spray solution were studied using 2⁴ full factorial design with three replicated center points. Adding PVP into the formulation significantly decreased the turbidity of the reconstitution solution and increased the IgG recovery. Adding trehalose, sucrose, or arginine further improved protein recovery after reconstitution and decreased the percentage of IgG aggregation. The Design of Experiments (DOE) results showed no significant effects from the four process factors on the process yield and IgG protein recovery in the range of parameters studied. All main factors except atomization pressure had significant effects on monomer percentage, among which air flow represented the most significant influence. In addition, the inlet air temperature had significant effects on the in vitro binding activity of IgG after spray layering. By optimizing the formulation, we were able to recover the most spray layered IgG and reduce the IgG aggregation during the process. The DOE studies gave insight into how process variables affect the spray layered products.

The role of Raman spectroscopy in biopharmaceuticals from development to manufacturing

Biopharmaceuticals have revolutionized the field of medicine in the types of active ingredient molecules and treatable indications. Adoption of Quality by Design and Process Analytical Technology (PAT) frameworks has helped the biopharmaceutical field to realize consistent product quality, process intensification, and real-time control. As part of the PAT strategy, Raman spectroscopy offers many benefits and is used successfully in bioprocessing from single-cell analysis to cGMP process control. Since first introduced in 2011 for industrial bioprocessing applications, Raman has become a first-choice PAT for monitoring and controlling upstream bioprocesses because it facilitates advanced process control and enables consistent process quality. This paper will discuss new frontiers in extending these successes in upstream from scale-down to commercial manufacturing. New reports concerning the use of Raman spectroscopy in the basic science of single cells and downstream process monitoring illustrate industrial recognition of Raman’s value throughout a biopharmaceutical product’s lifecycle. Finally, we draw upon a nearly 90-year history in biological Raman spectroscopy to provide the basis for laboratory and in-line measurements of protein quality, including higher-order structure and composition modifications, to support formulation development.

Molecular rationale for SARS-CoV-2 spike circulating mutations able to escape bamlanivimab and etesevimab monoclonal antibodies

The purpose of this work is to provide an in silico molecular rationale of the role eventually played by currently circulating mutations in the receptor binding domain of the SARS-CoV-2 spike protein (S-RBDCoV‑2) in evading the immune surveillance effects elicited by the two Eli Lilly LY-CoV555/bamlanivimab and LY-CoV016/etesevimab monoclonal antibodies. The main findings from this study show that, compared to the wild-type SARS-CoV-2 spike protein, mutations E484A/G/K/Q/R/V, Q493K/L/R, S494A/P/R, L452R and F490S are predicted to be markedly resistant to neutralization by LY-CoV555, while mutations K417E/N/T, D420A/G/N, N460I/K/S/T, T415P, and Y489C/S are predicted to confer LY-CoV016 escaping advantage to the viral protein. A challenge of our global in silico results against relevant experimental data resulted in an overall 90% agreement. Thus, the results presented provide a molecular-based rationale for all relative experimental findings, constitute a fast and reliable tool for identifying and prioritizing all present and newly reported circulating spike SARS-CoV-2 variants with respect to antibody neutralization, and yield substantial structural information for the development of next-generation vaccines and monoclonal antibodies more resilient to viral evolution.

Shedding light on both ends: An update on analytical approaches for N- and C-terminomics

Though proteases were long regarded as nonspecific degradative enzymes, over time, it was recognized that they also hydrolyze peptide bonds very specifically with a limited substrate pool. This irreversible posttranslational modification modulates the fate and activity of many proteins, making proteolytic processing a master switch in the regulation of e.g., the immune system, apoptosis and cancer progression. N- and C-terminomics, the identification of protein termini, has become indispensable in elucidating protease substrates and therefore protease function. Further, terminomics has the potential to identify yet unknown proteoforms, e.g. formed by alternative splicing or the recently discovered alternative ORFs. Different strategies and workflows have been developed that achieve higher sensitivity, a greater depth of coverage or higher throughput. In this review, we summarize recent developments in both N- and C-terminomics and include the potential of top-down proteomics which inherently delivers information on both ends of analytes in a single analysis.

Evaluating a Modified High Purity Polysorbate 20 Designed to Reduce the Risk of Free Fatty Acid Particle Formation

PURPOSE

To evaluate a modified high purity polysorbate 20 (RO HP PS20)-with lower levels of stearate, palmitate and myristate esters than the non-modified HP PS20-as a surfactant in biopharmaceutical drug products (DP). RO HP PS20 was designed to provide functional equivalence as a surfactant while delaying the onset of free fatty acid (FFA) particle formation upon hydrolytic degradation relative to HP PS20.

METHODS

Analytical characterization of RO HP PS20 raw material included fatty acid ester (FAE) distribution, higher order ester (HOE) fraction, FFA levels and trace metals. Functional assessments included 1) vial and intravenous bag agitation; 2) oxidation via a placebo and methionine surrogate study; and 3) hydrolytic PS20 degradation studies to evaluate FFA particle formation with and without metal nucleation.

RESULTS

Interfacial protection and oxidation propensity were comparable between the two polysorbates. Upon hydrolytic degradation, FFA particle onset was delayed in RO HP PS20. The delay was more pronounced when HOEs of PS20 were preferentially degraded. Furthermore, the hydrolytic degradants of RO HP PS20 formed fewer particles in the presence of spiked aluminum.

CONCLUSION

This work highlights the criticality of having tighter control on long chain FAE levels of PS20 to reduce the occurrence of FFA particle formation upon hydrolytic degradation and lower the variability in its onset. By simultaneously meeting compendial PS20 specifications while narrowing the allowable range for each FAE and shifting its composition towards the shorter carbon chain species, RO HP PS20 provides a promising alternative to HP PS20 for biopharmaceutical DPs.

Solving Complex Biologics Truncation Problems by Top-Down Mass Spectrometry

With increasing protein therapeutics being designed as non-mAb (non-monoclonal antibody) modalities, additional efforts and resources are required to develop and characterize such therapeutic proteins. Truncation is an emerging issue for manufacturing of non-mAb drug substances and requires sophisticated methods to investigate. In this paper, we describe two cases with complex truncation problems where traditional methods such as intact mass spectrometry led to inclusive or wrong identifications. Therefore, we developed an online top-down LC-MS (liquid chromatography-mass spectrometry) based workflow to study truncated drug substances, and we successfully identified the clipping locations. Compared to other orthogonal methods, this method provides a unique capability of solving protein clipping problems. The successful identification of truncated species and the high compatibility to routine intact MS make it a very valuable tool for resolving truncation problems during protein production in the pharmaceutical industry.

Rational optimization of a monoclonal antibody improves the aggregation propensity and enhances the CMC properties along the entire pharmaceutical process chain

The discovery of therapeutic monoclonal antibodies (mAbs) primarily focuses on their biological activity favoring the selection of highly potent drug candidates. These candidates, however, may have physical or chemical attributes that lead to unfavorable chemistry, manufacturing, and control (CMC) properties, such as low product titers, conformational and colloidal instabilities, or poor solubility, which can hamper or even prevent development and manufacturing. Hence, there is an urgent need to consider the developability of mAb candidates during lead identification and optimization. This work provides a comprehensive proof of concept study for the significantly improved developability of a mAb variant that was optimized with the help of sophisticated in silico tools relative to its difficult-to-develop parental counterpart. Interestingly, a single amino acid substitution in the variable domain of the light chain resulted in a three-fold increased product titer after stable expression in Chinese hamster ovary cells. Microscopic investigations revealed that wild type mAb-producing cells displayed potential antibody inclusions, while the in silico optimized variant-producing cells showed a rescued phenotype. Notably, the drug substance of the in silico optimized variant contained substantially reduced levels of aggregates and fragments after downstream process purification. Finally, formulation studies unraveled a significantly enhanced colloidal stability of the in silico optimized variant while its folding stability and potency were maintained. This study emphasizes that implementation of bioinformatics early in lead generation and optimization of biotherapeutics reduces failures during subsequent development activities and supports the reduction of project timelines and resources.

The effects of intramolecular and intermolecular electrostatic repulsions on the stability and aggregation of NISTmAb revealed by HDX-MS, DSC, and nanoDSF

The stability and aggregation of NIST monoclonal antibody (NISTmAb) were investigated by hydrogen/deuterium exchange mass spectrometry (HDX-MS), differential scanning calorimetry (DSC), and nano-differential scanning fluorimetry (nanoDSF). NISTmAb was prepared in eight formulations at four different pHs (pH 5, 6, 7, and 8) in the presence and absence of 150 mM NaCl and analyzed by the three methods. The HDX-MS results showed that NISTmAb is more conformationally stable at a pH near its isoelectric point (pI) in the presence of NaCl than a pH far from its pI in the absence of NaCl. The stabilization effects were global and not localized. The midpoint temperature of protein thermal unfolding transition results also showed the C_H 2 domain of the protein is more conformationally stable at a pH near its pI. On the other hand, the onset of aggregation temperature results showed that NISTmAb is less prone to aggregate at a pH far from its pI, particularly in the absence of NaCl. These seemingly contradicting results, higher conformational stability yet higher aggregation propensity near the pI than far away from the pI, can be explained by intramolecular and intermolecular electrostatic repulsion using Lumry-Eyring model, which separates folding/unfolding equilibrium and aggregation event. The further a pH from the pI, the higher the net charge of the protein. The higher net charge leads to greater intramolecular and intermolecular electrostatic repulsions. The greater intramolecular electrostatic repulsion destabilizes the protein and the greater intermolecular electrostatic repulsion prevents aggregation of the protein molecules at pH far from the pI.

An Automated Multicycle Immunoaffinity Enrichment Approach Developed for Sensitive Mouse IgG1 Antibody Drug Analysis in Mouse Plasma Using LC/MS/MS

In the immuno-oncology field, surrogate mouse monoclonal antibodies are often preferred in establishing proper PK/PD/efficacy correlations as well as supporting anticipated mouse to human translation. Thus, a highly sensitive and specific bioanalytical method is needed in quantifying those surrogate mouse antibodies after dosing in mice. Unfortunately, when specific reagents, such as recombinant target antigen and anti-idiotypic antibody, are not available, measuring mouse surrogate antibody drugs in mice is very challenging for ligand binding assay (LBA) due to the severe cross reactivity potential. Different from LBA, if at least one unique surrogate peptide can be identified from the surrogate antibody sequence, the immunoaffinity enrichment based LC/MS/MS assay may be able to differentiate the analyte response from the high endogenous immunoglobulin background and provide adequate sensitivity. Herein, a new automated multicycle immunoaffinity enrichment method was recently developed to extract a surrogate mouse IgG1 (mIgG1) antibody drug from mouse plasma using a commercially available antimouse IgG1 secondary antibody. In the assay, reuse of the capture antibody up to six times mostly resolved the binding capacity issue caused by the abundant endogenous mIgG1 and made the immunoaffinity enrichment step more cost-effective. Combined with a unique surrogate peptide identified from the antibody, the LC/MS/MS assay achieved a limit of quantitation of 5 ng/mL with satisfactory assay precision, accuracy, and dynamic range. The successful implementation of this novel approach in discovery pharmacokinetic (PK) studies eliminates the dependence on specially generated immunoaffinity capturing reagents.

Calculation of therapeutic antibody viscosity with coarse-grained models, hydrodynamic calculations and machine learning-based parameters

High viscosity presents a challenge for manufacturing and drug delivery of therapeutic antibodies. The viscosity is determined by protein-protein interactions among many antibodies. Molecular simulation is a promising method to study protein-protein interactions; however, all-atom models do not allow the simulation of multiple molecules, which is necessary to compute viscosity directly. Coarse-grained models, on the other hand can do this. In this work, a 12-bead coarse-grained model based on Swan and coworkers (J. Phys. Chem. B 2018, 122, 2867-2880) was applied to study antibody interactions. Two adjustable parameters related to the short-range interactions on the variable and constant regions were determined by fitting experimental data of 20 IgG1 monoclonal antibodies at 150 mg/mL. The root-mean-square deviation improved from 1 to 0.68, and the correlation coefficient improved from 0.63 to 0.87 compared to that of a previous model that assumed the short-range interactions were the same for all the beads. Our model is also able to calculate the viscosity over a wide range of concentrations without additional parameters. A tabulated viscosity based on our model is provided to facilitate antibody screening in early-stage design.

Novel Method for the Isolation of Proteins and Small Target Molecules from Biological and Aqueous Media by Salt-Assisted Phase Transformation of Their PEGylated Recognition Counterparts

An efficient and simple method for the application of PEGylated affinity ligands in precipitative isolation of protein target molecules (TMs) from a biological fluid such as blood serum or small target molecules from an aqueous medium is presented for the first time. This approach is based on the high binding specificity of PEGylated recognition molecules (PEG-RMs) to their TMs and the unique physicochemical properties of PEG that result in their salt-assisted phase transformation. Addition of PEG-RM to blood serum results in the formation of an RM-specific macromolecular complex (PEG-RM + TM → PEG-RM.TM) that undergoes facile salt-assisted phase transformation to a separable semisolid with ammonium sulfate. PEG-RM.TM is then dissociated into its components by pH reduction or an increase of ionic strength (PEG-RM.TM → PEG-RM + TM). PEG-RM is salted out to afford pure TM in solution. The same phenomenon is observed when RM or TM are small molecules. The general applicability of the method was validated by PEGylation of two proteins (protein A, sheep antihuman IgG) and a small molecule (salicylic acid) used as model RMs for the isolation of Igs, IgG, and serum albumin from blood serum. The isolated protein TMs were shown to be pure and aggregate-free by gel electrophoresis and dynamic light scattering (DLS). IgG isolated by this method was further characterized by peptide mass fingerprinting. PEGylated protein A was used to demonstrate the recyclability and scale-up potential of PEG-RM. IgG isolated by this method from blood serum of a hepatitis C-vaccinated individual was tested for its binding to sheep antihuman IgG by UV spectroscopy, and its bioactivity was ascertained by comparison of its enzyme-linked immunosorbent assay (ELISA) result to that of a blood sample from the same individual. Reciprocity of RM and TM was ascertained using PEGylated salicylic acid to obtain pure serum albumin, and PEGylated serum albumin was utilized for near-exclusive isolation of one drug from an aqueous equimolar mixture of three drugs (salicylic acid, 91%; capecitabine, 6%; and deferiprone, 3%). Advantages of this approach, including target specificity and general applicability and celerity, over other affinity methods for the isolation of proteins are discussed at a molecular level.

A Comprehensive Assessment of All-Oleate Polysorbate 80: Free Fatty Acid Particle Formation, Interfacial Protection and Oxidative Degradation

PURPOSE

Enzymatic polysorbate (PS) degradation and resulting free fatty acid (FFA) particles are detrimental to biopharmaceutical drug product (DP) stability. Different types and grades of polysorbate have varying propensity to form FFA particles. This work evaluates the homogenous all-oleate (AO) PS80 alongside heterogeneous PS20 and PS80 grades in terms its propensity to form FFA particles and other important attributes like interfacial protection and oxidation susceptibility.

METHODS

FFA particle formation rates were compared by degrading PS using non-immobilized hydrolases and fast degrading DP formulations. Interfacial protection of monoclonal antibodies (mAbs) was assessed by agitation studies in saline using non-degraded and degraded PS. Several antioxidants were assessed for their ability to mitigate AO PS80 oxidation and subsequent mAb oxidation by a 40°C placebo stability study and a 2, 2'-Azobis (2-amidinopropane) dihydrochloride stress model, respectively.

RESULTS

Visible and subvisible particles were significantly delayed in AO PS80 formulations compared with heterogeneous PS20 and PS80 formulations. Non-degraded AO PS80 was less protective of mAbs against the air-water interface compared with heterogeneous PS20. Interfacial protection by AO PS80 improved upon degradation owing to high surface activity of FFAs. Diethylenetriaminepentaacetic acid (DTPA) completely mitigated AO PS80 oxidation unlike L-methionine and N-Acetyl-DL-Tryptophan. However, DTPA did not mitigate radical mediated mAb oxidation.

CONCLUSION

AO PS80 is a promising alternative to reduce FFA particle formation compared with other PS types and grades. However, limitations observed here---such as lower protection against interfacial stresses and higher propensity for oxidation---need to be considered in assessing the risk/benefit ratio in using AO PS80.

mRNA in cancer immunotherapy: beyond a source of antigen

mRNA therapeutics have become the focus of molecular medicine research. Various mRNA applications have reached major milestones at high speed in the immuno-oncology field. This can be attributed to the knowledge that mRNA is one of nature's core building blocks carrying important information and can be considered as a powerful vector for delivery of therapeutic proteins to the patient.For a long time, the major focus in the use of in vitro transcribed mRNA was on development of cancer vaccines, using mRNA encoding tumor antigens to modify dendritic cells ex vivo. However, the versatility of mRNA and its many advantages have paved the path beyond this application. In addition, due to smart design of both the structural properties of the mRNA molecule as well as pharmaceutical formulations that improve its in vivo stability and selective targeting, the therapeutic potential of mRNA can be considered as endless.As a consequence, many novel immunotherapeutic strategies focus on the use of mRNA beyond its use as the source of tumor antigens. This review aims to summarize the state-of-the-art on these applications and to provide a rationale for their clinical application.

Energetic Dissection of Mab-Specific Reversible Self-Association Reveals Unique Thermodynamic Signatures

PURPOSE

Reversible self-association (RSA) remains a challenge in the development of therapeutic monoclonal antibodies (mAbs). We recently analyzed the energetics of RSA for five IgG mAbs (designated as A-E) under matched conditions and using orthogonal methods. Here we examine the thermodynamics of RSA for two of the mAbs that showed the strongest evidence of RSA (mAbs C and E) to identify underlying mechanisms.

METHODS

Concentration-dependent dynamic light scattering and sedimentation velocity (SV) studies were carried out for each mAb over a range of temperatures. Because self-association was weak, the SV data were globally analyzed via direct boundary fitting to identify best-fit models, accurately determine interaction energetics, and account for the confounding effects of thermodynamic and hydrodynamic nonideality.

RESULTS

mAb C undergoes isodesmic self-association at all temperatures examined, with the energetics indicative of an enthalpically-driven reaction offset by a significant entropic penalty. By contrast, mAb E undergoes monomer-dimer self-association, with the reaction being entropically-driven and comprised of only a small enthalpic contribution.

CONCLUSIONS

Classical interpretations implicate van der Waals interactions and H-bond formation for mAb C RSA, and electrostatic interactions for mAb E. However, noting that RSA is likely coupled to additional equilibria, we also discuss the limitations of such interpretations.

Product-Specific Impact of Viscosity Modulating Formulation Excipients During Ultra-High Concentration Biotherapeutics Drug Product Development

Developing ultra-high concentration biotherapeutics drug products can be challenging due to increased viscosity, processing, and stability issues. Excipients used to alleviate these concerns are traditionally evaluated at lower protein concentrations. This study investigates whether classically known modulators of stability and viscosity at low (<50 mg/mL) to high (>50 - 150 mg/mL) protein concentrations are beneficial in ultra-high (>150 mg/mL) concentration protein formulations and drug products. This study evaluates the effect of arginine monohydrochloride, proline, and lysine monohydrochloride on viscosity and concentratability at different high and ultra-high protein concentrations using a monoclonal antibody, mAbN, formulation as a candidate protein system. The effect of excipients on the viscosity and concentratability (rate and extent) was different at high versus ultra-high protein concentrations. These results highlight that classical excipients in literature known to modulate protein interactions at low protein concentrations and reduce viscosity at high protein concentrations may need to be evaluated at target protein concentrations in a product-specific manner while developing ultra-high concentration biologics drug products.

Identification and quantitation of hinge cysteinylation on endogenous IgG2 antibodies from human serum

Cysteinylation is a post-translational modification (PTM) that occurs when a cysteine residue on a protein forms a disulfide bond with a terminal cysteine molecule. This PTM has been found in the hinge region of several recombinant therapeutic IgG2 antibodies, but the impact of cysteinylation on the safety and immunogenicity of therapeutics remains unclear. In this study, we characterized recombinant and endogenous IgG2 antibodies to quantify their levels of hinge cysteinylation, if present. To the best of our knowledge, this is the first study to identify and quantify hinge cysteinylation in endogenous IgG2 antibodies from healthy human serum. We used anti-IgG2 immunopurification of human serum to specifically enrich for endogenous IgG2 antibodies, and then subjected the resulting samples to Lys-C peptide mapping coupled with targeted mass spectrometry techniques. Using this analytical workflow, we found that all healthy human serum samples tested (N = 10) contained quantifiable levels of hinge cysteinylation (0.8 ± 0.3%) in their endogenous human IgG2s (IgG2-A isoform). These findings demonstrate that hinge cysteinylation in therapeutic IgG2s, at least up to a certain level, is well tolerated in humans and pose minimal safety or immunogenicity risks.

Instability of therapeutic proteins - An overview of stresses, stabilization mechanisms and analytical techniques involved in lyophilized proteins

Solid-state is the preferred choice for storage of protein therapeutics to improve stability and preserve the biological activity by decreasing the physical and chemical degradation associated with liquid protein formulations. Lyophilization or freeze-drying is an effective drying method to overcome the instability problems of proteins. However, the processing steps (freezing, primary drying and secondary drying) involved in the lyophilization process can expose the proteins to various stress and harsh conditions, leading to denaturation, aggregation often a loss in activity of protein therapeutics. Stabilizers such as sugars and surfactants are often added to protect the proteins against physical stress associated with lyophilization process and storage conditions. Another way to curtail the degradation of proteins due to process related stress is by modification of the lyophilization process. Slow freezing, high nucleation temperature, decreasing the extent of supercooling, and annealing can minimize the formation of the interface (ice-water) by producing large ice crystals with less surface area, thereby preserving the native structure and stability of the proteins. Hence, a thorough understanding of formulation composition, lyophilization process parameters and the choice of analytical methods to characterize and monitor the protein instability is crucial for development of stable therapeutic protein products. This review provides an overview of various stress conditions that proteins might encounter during lyophilization process, mechanisms to improve the stability and analytical techniques to tackle the proteins instability during both freeze-drying and storage.

Development challenges of high concentration monoclonal antibody formulations

High concentration monoclonal antibody drug products represent a special segment of biopharmaceuticals. In contrast to other monoclonal antibody products, high concentration monoclonal antibodies are injected subcutaneously helping increase patient compliance and reduce the number of hospital patient visits. It is important to note that a high protein concentration (≥50 mg/mL) poses a challenge from a product development perspective. Colloidal properties, physical and chemical protein stability should be considered during formulation, primary packaging and manufacturing process development as well as optimization of other dosage form-related parameters. The aim of such development work is to obtain a drug product capable of maintaining appropriate protein structure throughout its shelf-life and ensure proper and accurate dosage upon administration.

In-Use Interfacial Stability of Monoclonal Antibody Formulations Diluted in Saline i.v. Bags

The use of monoclonal antibodies (mAbs) for the treatment of a variety of diseases is rapidly growing each year. Many mAbs are administered intravenously using i.v. bags containing 0.9% NaCl (normal saline). We studied the aggregation propensity of these antibody solutions in saline and compared it with a low ionic strength formulation buffer. The mAb studied in this work is prone to aggregate, and is known to form a viscoelastic network at the air-solution interface. We observed that this interfacial elasticity increased when formulated in saline. In the bulk, the mAbs exhibited a tendency to self-associate that was higher in saline. We also studied the aggregation of the mAbs in the presence of polysorbate-20, typically added to formulations to mitigate interfacial aggregation. We observed that with surfactants, the presence of salt in the buffer led to a greater mAb adsorption at the interface and resulted in the formation of more particulate aggregates. Our results show that the addition of salt to the buffer led to differences in the interfacial aggregation in mAb formulations, showing that stress studies used to screen for mAb aggregation intended for i.v. administration should be performed in conditions representative of their intended route of administration.

Contribution of Intrinsic Fluorescence to the Design of a New 3D-Printed Implant for Releasing SDABS

Single-domain antibodies (sdAbs) offer great features such as increased stability but are hampered by a limited serum half-life. Many strategies have been developed to improve the sdAb half-life, such as protein engineering and controlled release systems (CRS). In our study, we designed a new product that combined a hydrogel with a 3D-printed implant. The results demonstrate the implant’s ability to sustain sdAb release up to 13 days through a reduced initial burst release followed by a continuous release. Furthermore, formulation screening helped to identify the best sdAb formulation conditions and improved our understanding of our CRS. Through the screening step, we gained knowledge about the influence of the choice of polymer and about potential interactions between the sdAb and the polymer. To conclude, this feasibility study confirmed the ability of our CRS to extend sdAb release and established the fundamental role of formulation screening for maximizing knowledge about our CRS.

In Pursuit of Stability Enhancement of a Prostate Cancer Targeting Antibody Derived from a Transgenic Animal Platform

Accelerated timelines necessitate the discovery of fully human antibodies as biotherapeutics using transgenic animals with a notion that such mAbs bypass humanization. A transgenic animal derived mAb (PCa75) targeted against a prostate cancer antigen had several ‘unusual residues’ (rare somatic hypermutations, rSHM, with positional frequency of <1%) that resulted in compromised biophysical properties (Tm = 61 °C and intrinsic stability ΔGu = 24.3 kJ/mol) and a sub-optimal immunogenicity profile. In our quest for quality medicine, we pursued antibody engineering strategies to enhance the stability of PCa75. PCa62, an engineered variant of PCa75, retained function while significantly improving the drug-like attributes of the molecule (Tm = 75 °C and intrinsic stability ΔGu = 63.5 kJ/mol). rSHM is rather prevalent, 18 out the 21 approved transgenic animal-derived antibodies have at least one ‘unusual residue’. Thus, engineering of rSHM remains critical to enhance the stability and minimize immunogenicity risk of biotherapeutics.

Discovery of a Photoinduced Histidine-Histidine Cross-Link in an IgG4 Antibody

A novel histidine-histidine (His-His) photooxidative cross-link has been identified in an IgG4 antibody. It was formed between the side chain of a histidine residue of the antibody and histidine from the formulation buffer. The structure of the cross-link was elucidated using high performance liquid chromatography (HPLC) hyphenated to tandem mass spectrometry (MS/MS) with higher energy collisional dissociation (HCD). The cross-link was found in multiple conformations, as the location of the oxygen varied. Furthermore, the extent of cross-link formation was shown to correlate with the amount of light the antibody was exposed to as well as the solvent accessibility of each modification site.

Cetuximab-conjugated chitosan-pectinate (modified) composite nanoparticles for targeting colon cancer

In the present study, we successfully developed a cetuximab-conjugated modified citrus pectin-chitosan nanoparticles for targeted delivery of curcumin (Cet-MCPCNPs) for the treatment of colorectal cancer. In vitro analyses revealed that nanoparticles were spherical with size of 249.33 ± 5.15 nm, a decent encapsulation efficiency (68.43 ± 2.4%) and a 'smart' drug release profile. 61.37 ± 0.70% of cetuximab was adsorbed to the surface of the nanoparticles. Cellular uptake studies displayed enhanced internalization of Cet-MCPCNPs in Caco-2 (EGFR +ve) cells, which ultimately resulted in a significant reduction in cancer cell propagation. The cell cycle analysis indicated that Cet- MCPCNPs induced cell death in enhanced percentage of Caco-2 cells by undergoing cell cycle arrest in the G2/M phase. These data suggest that Cet-MCPCNPs represent a new and promising targeting approach for the treatment of colorectal cancer.

Human Serum Albumin, a Suitable Candidate to Stabilize Freeze-Dried IgG in Combination with Trehalose: Central Composite Design

Freeze-dried immunoglobulin G (IgG) incorporating trehalose and human serum albumin (HSA) was statistically evaluated regarding the existence of synergism between additives on the stability profile. The levels of HSA (X₁) and trehalose (X₂) were independent variables. Aggregation following the process (Y₁), after 2 and 3 months at 40°C (Y₂) and (Y₃), respectively, along with the rate constant of aggregation (Y₄) were dependent variables. Aggregation and beta-sheet conformation were quantified through size-exclusion chromatography (SEC-HPLC) and Fourier transform infrared spectroscopy (FTIR). Central composite design (CCD) suggested the best formulation. The integrity and thermodynamic stability of optimized formulation were investigated through sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and differential scanning calorimetry (DSC). The calculated responses were Y₁, 0-0.90%; Y₂, 0.4-4.3%; Y₃, 2.10-13.46%; and Y₄, 0.16-0.69 1/month. The optimized formulation had 10 mg IgG, 86 mg trehalose, and 1 mg HSA with observed responses of Y₁, 0.01%; Y₂, 0.51%; Y₃, 3.08%; and Y₄, 0.33 1/month. The models were statistically well-fitted. The optimized formulation was amorphous during freeze-drying (FD), and no fragmentation was observed. Trehalose and HSA demonstrated statistical synergism. CCD was successfully employed to recommend the best ratio of stabilizers and achieve the maximum stabilization of IgG as a model freeze-dried antibody.

Selective depletion of metastatic stem cells as therapy for human colorectal cancer

Selective elimination of metastatic stem cells (MetSCs) promises to block metastatic dissemination. Colorectal cancer (CRC) cells overexpressing CXCR4 display trafficking functions and metastasis‐initiating capacity. We assessed the antimetastatic activity of a nanoconjugate (T22‐GFP‐H6‐FdU) that selectively delivers Floxuridine to CXCR4⁺ cells. In contrast to free oligo‐FdU, intravenous T22‐GFP‐H6‐FdU selectively accumulates and internalizes in CXCR4⁺ cancer cells, triggering DNA damage and apoptosis, which leads to their selective elimination and to reduced tumor re‐initiation capacity. Repeated T22‐GFP‐H6‐FdU administration in cell line and patient‐derived CRC models blocks intravasation and completely prevents metastases development in 38–83% of mice, while showing CXCR4 expression‐dependent and site‐dependent reduction in foci number and size in liver, peritoneal, or lung metastases in the rest of mice, compared to free oligo‐FdU. T22‐GFP‐H6‐FdU induces also higher regression of established metastases than free oligo‐FdU, with negligible distribution or toxicity in normal tissues. This targeted drug delivery approach yields potent antimetastatic effect, through selective depletion of metastatic CXCR4⁺ cancer cells, and validates metastatic stem cells (MetSCs) as targets for clinical therapy.