Therapeutic antibodies--delivering the promise?

Review of COVID-19 Antibody Therapies

In the global health emergency caused by coronavirus disease 2019 (COVID-19), efficient and specific therapies are urgently needed. Compared with traditional small-molecular drugs, antibody therapies are relatively easy to develop; they are as specific as vaccines in targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); and they have thus attracted much attention in the past few months. This article reviews seven existing antibodies for neutralizing SARS-CoV-2 with 3D structures deposited in the Protein Data Bank (PDB). Five 3D antibody structures associated with the SARS-CoV spike (S) protein are also evaluated for their potential in neutralizing SARS-CoV-2. The interactions of these antibodies with the S protein receptor-binding domain (RBD) are compared with those between angiotensin-converting enzyme 2 and RBD complexes. Due to the orders of magnitude in the discrepancies of experimental binding affinities, we introduce topological data analysis, a variety of network models, and deep learning to analyze the binding strength and therapeutic potential of the 14 antibody-antigen complexes. The current COVID-19 antibody clinical trials, which are not limited to the S protein target, are also reviewed.

Advancements in mRNA Encoded Antibodies for Passive Immunotherapy

Monoclonal antibodies are the fastest growing therapeutic class in medicine today. They hold great promise for a myriad of indications, including cancer, allergy, autoimmune and infectious diseases. However, the wide accessibility of these therapeutics is hindered by manufacturing and purification challenges that result in high costs and long lead times. Efforts are being made to find alternative ways to produce and deliver antibodies in more expedient and cost-effective platforms. The field of mRNA has made significant progress in the last ten years and has emerged as a highly attractive means of encoding and producing any protein of interest in vivo. Through the natural role of mRNA as a transient carrier of genetic information for translation into proteins, in vivo expression of mRNA-encoded antibodies offer many advantages over recombinantly produced antibodies. In this review, we examine both preclinical and clinical studies that demonstrate the feasibility of mRNA-encoded antibodies and discuss the remaining challenges ahead.

Facile production of nanocomposites of carbon nanotubes and polycaprolactone with high aspect ratios with potential applications in drug delivery

The geometries and surface properties of nanocarriers greatly influence the interaction between nanomaterials and living cells. In this work we combine multiwalled carbon nanotubes (CNTs) with poly-ε-caprolactone (PCL) to produce non-spherical nanocomposites with high aspect ratios by using a facile emulsion solvent evaporation method. Particles were characterised by dynamic light scattering (DLS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and asymmetric flow field flow fractionation (AF4). Different sizes and morphologies of nanoparticles were produced depending on the concentration of the sodium dodecyl sulphate (SDS), CNTs and PCL. Rod-like PCL-CNT nanostructures with low polydispersity were obtained with 1.5 mg mL-1 of SDS, 0.9 mg mL-1 of CNTs and 10 mg mL-1 PCL. AFM analysis revealed that the PCL and PCL-CNT nanocomposite had comparatively similar moduli of 770 and 560 MPa respectively, indicating that all the CNTs have been coated with at least 2 nm of PCL. Thermogravimetric analysis of the PCL-CNT nanocomposite indicated that they contained 9.6% CNTs by mass. The asymmetric flow field flow fractionation of the samples revealed that the PCL-CNT had larger hydrodynamic diameters than PCL alone. Finally, the drug loading properties of the nanocomposites were assessed using docetaxel as the active substance. The nanocomposites showed comparable entrapment efficiencies of docetaxel (89%) to the CNTs alone (95%) and the PCL nanoparticles alone (81%). This is a facile method for obtaining non-spherical nanocomposites that combines the properties of PCL and CNTs such as the high aspect ratio, modulus. The high drug entrapment efficiency of these nanocomposites may have promising applications in drug delivery.

Advantages of AlaGln as an additive to cell culture medium: use with anti-CD20 chimeric antibody-producing POTELLIGENT™ CHO cell lines

L-alanyl-L-glutamine (AlaGln) is dipeptide that has better solubility and stability than Glutamine (Gln). In this study, we evaluated the utility of this dipeptide during culture of POTELLIGENT™ Chinese hamster ovary (CHO) cells expressing anti-CD20 chimeric antibody. Although AlaGln in the culture medium lowered the specific growth rate, the MAb titer was maximized when Gln was completely replaced by AlaGln in both the basal and feed media. Moreover, AlaGln augmented production of antibody not only at flask scale but also at spinner scale, although the extent of this effect was dependent on the cell clone. To explore the mechanism responsible for the effect of AlaGln on cell growth, we measured apoptosis in the early phase of cell culture on days 8, 9, and 10. The apoptotic ratio was reduced in medium containing AlaGln. Ammonia was generated in medium containing Gln when it was maintained at 37 °C, which impeded the growth and productivity of the cells. In contrast, AlaGln produced less ammonia under these conditions, which may have been one of the properties associated with its beneficial effects. We conclude that certain dipeptides can serve as superior alternative sources of amino acids in cell culture and antibody production.

Nuclease colicins and their immunity proteins

It is more than 80 years since Gratia first described 'a remarkable antagonism between two strains of Escherichia coli'. Shown subsequently to be due to the action of proteins (or peptides) produced by one bacterium to kill closely related species with which it might be cohabiting, such bacteriocins have since been shown to be commonplace in the internecine warfare between bacteria. Bacteriocins have been studied primarily from the twin perspectives of how they shape microbial communities and how they penetrate bacteria to kill them. Here, we review the modes of action of a family of bacteriocins that cleave nucleic acid substrates in E. coli, known collectively as nuclease colicins, and the specific immunity (inhibitor) proteins that colicin-producing organisms make in order to avoid committing suicide. In a process akin to targeting in mitochondria, nuclease colicins engage in a variety of cellular associations in order to translocate their cytotoxic domains through the cell envelope to the cytoplasm. As well as informing on the process itself, the study of nuclease colicin import has also illuminated functional aspects of the host proteins they parasitize. We also review recent studies where nuclease colicins and their immunity proteins have been used as model systems for addressing fundamental problems in protein folding and protein-protein interactions, areas of biophysics that are intimately linked to the role of colicins in bacterial competition and to the import process itself.

Conformational stability and aggregation of therapeutic monoclonal antibodies studied with ANS and Thioflavin T binding

Characterization of aggregation profiles of monoclonal antibodies (mAb) is gaining importance because an increasing number of mAb-based therapeutics are entering clinical studies and gaining marketing approval. To develop a successful formulation, it is imperative to identify the critical biochemical properties of each potential mAb drug candidate. We investigated the conformational change and aggregation of a human IgG1 using external dye-binding experiments with fluorescence spectroscopy and compared the aggregation profiles obtained to the results of size-exclusion chromatography. We show that using an appropriate dye at selected mAb concentration, unfolding or aggregation can be studied. In addition, dye-binding experiments may be used as conventional assays to study therapeutic mAb stability.

The autophilic anti-CD20 antibody DXL625 displays enhanced potency due to lipid raft-dependent induction of apoptosis

Despite widespread use of anti-CD20 antibodies as therapeutic agents for oncologic and autoimmune indications, precise descriptions of killing mechanisms remain incomplete. Complement-dependent cytolysis and antibody-dependent cell-mediated cytotoxicity are indicated as modes of target cell depletion; however, the importance of apoptosis induction is controversial. Studies showing that the therapeutic anti-CD20 antibody rituximab (Rituxan) mediates apoptosis of tumor cell targets in vitro after cross-linking by anti-Fc reagents suggest that enhancement strategies applied to Fc-independent activities for anti-CD20 antibodies could improve therapeutic efficacy. An anti-CD20 antibody designated DXL625, with autophilic properties such as increased binding avidity, is shown here to independently induce caspase-mediated apoptosis of an established B-cell lymphoma line in vitro. Depletion of membrane cholesterol or chelation of extracellular calcium abrogated the pro-apoptotic activity of DXL625, indicating that intact lipid rafts and calcium are required for this activity. The Fc-mediated complement-dependent and antibody-dependent cellular killing mechanisms are maintained by DXL625 despite conjugation of the parental Rituxan antibody to the autophilic DXL peptide sequence. This study shows a strategy for improving anti-CD20 immunotherapy by endowing therapeutic antibodies with self-interacting properties.

The safety and side effects of monoclonal antibodies

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases, as well as a range of new indications. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness and the generation of antibodies. In addition, there are numerous adverse effects of mAbs that are related to their specific targets, including infections and cancer, autoimmune disease, and organ-specific adverse events such as cardiotoxicity. In March 2006, a life-threatening cytokine release syndrome occurred during a first-in-human study with TGN1412 (a CD28-specific superagonist mAb), resulting in a range of recommendations to improve the safety of initial human clinical studies with mAbs. Here, we review some of the adverse effects encountered with mAb therapies, and discuss advances in preclinical testing and antibody technology aimed at minimizing the risk of these events.

Lactosyl derivatives function in a rat model of severe burn shock by acting as antagonists against CD11b of integrin on leukocytes

Severe burn shock remains an unsolved clinical problem with urgent needs to explore novel therapeutic approaches. In this study, the in vivo bioactivity of a series of synthetic lactosyl derivatives (oligosaccharides) was assessed on rats with burn shock to elucidate the underlying mechanisms. Administration of An-2 and Gu-4, two lactosyl derivatives with di- and tetravalent beta-D: -galactopyranosyl-(1-4)-beta-D: -glucopyranosyl ligands, significantly prolonged the survival time (P < 0.05 vs. saline), stabilized blood pressure and ameliorated the injuries to vital organs after burn. Flow chamber assay displayed that An-2 and Gu-4 markedly decreased the adhesion of leukocytes to microvessel endothelial cells. Competitive binding assay showed that a CD11b antibody significantly interrupted the interaction of An-2 and Gu-4 with leukocytes from rats with burn shock. With fluorescent microscopy, we further found that the oligosaccharides were selectively bound to leukocytes and with a colocalization of CD11b on the cell membrane. Interestingly, the lectin domain-deficient form of CD11b failed to bind with An-2 and Gu-4. The results suggest that both An-2 and Gu-4 significantly inhibit the adhesion of leukocytes to endothelial cells by binding to CD11b and thereby exert protective effects on severe burn shock.

The application of SELDI-TOF mass spectrometry to mammalian cell culture

Surface Enhanced Laser Desorption/Ionisation Time-of-Fight Mass Spectrometry (SELDI-TOF MS) is a technique by which protein profiles can be rapidly produced from a wide variety of biological samples. By employing chromatographic surfaces combined with the specificity and reproducibility of mass spectrometry it has allowed for profiles from complex biological samples to be analysed. Profiling and biomarker identification have been employed widely throughout the biological sciences. To date, however, the benefits of SELDI-TOF MS have not been realised in the area of mammalian cell culture. The advantages in identifying markers for cell stresses, apoptosis and other culture parameters mean that these tools could help greatly to enhance monitoring and control of bioreaction process and improve the production of therapeutics. Better characterisation of culture systems through proteome analysis will allow for improved productivity and better yields.

Preparation and use of therapeutic antibodies primarily of human origin

Therapeutic antibodies include polyclonal immunoglobulins isolated from regular or high-titered human plasma, sera from immunized animals, and monoclonal antibodies. This array of therapeutic antibodies is used for the prevention and treatment of many infectious diseases, antibody immunodeficiencies, autoimmune and inflammatory diseases, neurological disorders, and cancers. Polyclonal human immunoglobulins are available for intramuscular injection (IGIM), intravenous infusion (IGIV) and subcutaneous infusion (SCIG). We review these products and detail the therapeutic use of polyclonal human antibodies in the treatment of antibody immunodeficiencies, including their occasional local side effects (tenderness, sterile abscesses), minor systemic side effects (chills, muscle aches, malaise, headaches) and major side effects (aseptic meningitis, nephropathy, thrombosis).

Applications of glycosyltransferases in the site-specific conjugation of biomolecules and the development of a targeted drug delivery system and contrast agents for MRI

BACKGROUND

The delivery of drugs to the proposed site of action is a challenging task. Tissue and cell-specific guiding molecules are being used to carry a cargo of therapeutic molecules. The cargo molecules need to be conjugated in a site-specific manner to the therapeutic molecules such that the bioefficacy of these molecules is not compromised.

METHODS

Using wild-type and mutant glycosyltransferases, the sugar moiety with a unique chemical handle is incorporated at a specific site in the cargo or therapeutic molecules, making it possible to conjugate these molecules through the chemical handle present on the modified glycan.

RESULTS/CONCLUSIONS

The modified glycan residues introduced at specific sites on the cargo molecule make it possible to conjugate fluorophores for ELISA-based assays, radionuclides for imaging and immunotherapy applications, lipids for the assembly of immunoliposomes, cytotoxic drugs, cytokines, or toxins for antibody-based cancer therapy and the development of a targeted drug delivery system.

Site-specific linking of biomolecules via glycan residues using glycosyltransferases

The structural information on glycosyltransferases has revealed that the sugar-donor specificity of these enzymes can be broadened to include modified sugars with a chemical handle that can be utilized for conjugation chemistry. Substitution of Tyr289 to Leu in the catalytic pocket of bovine beta-1,4-galactosyltransferase generates a novel glycosyltransferase that can transfer not only Gal but also GalNAc or a C2-modified galactose that has a chemical handle, from the corresponding UDP-derivatives, to the non-reducing end GlcNAc residue of a glycoconjugate. Similarly, the wild-type polypeptide-N-acetyl-galactosaminyltransferase, which naturally transfers GalNAc from UDP-GalNAc, can also transfer C2-modified galactose with a chemical handle from its UDP-derivative to the Ser/Thr residue of a polypeptide acceptor substrate that is tagged as a fusion peptide to a non-glycoprotein. The potential of wild-type and mutant glycosyltransferases to produce glycoconjugates carrying sugar moieties with chemical handle makes it possible to conjugate biomolecules with orthogonal reacting groups at specific sites. This methodology assists in the assembly of bio-nanoparticles that are useful for developing targeted drug-delivery systems and contrast agents for magnetic resonance imaging.

Interaction between lysozyme and poly(acrylic acid) microgels

The interaction between lysozyme and oppositely charged poly(acrylic acid) microgels was investigated by micromanipulator-assisted light microscopy, confocal microscopy and circular dichroism. Lysozyme uptake and distribution within the microgel particles, and its effect on microgel deswelling, was studied regarding effects of pH, ionic strength and lysozyme concentration. For a range of conditions, lysozyme distributes nonuniformly within the microgels, forming a lysozyme/microgel shell in the outer parts of the microgel. This shell formation is associated both with increased lysozyme loading to the microgels and with increased lysozyme-induced microgel deswelling. At high microgel charge density, the shell formation displays nonmonotonic ionic strength dependence. The shells formed are characterized by a net positive charge, and by relatively fast exchange of lysozyme between shell and solution, although the exchange kinetics decreases strongly with decreasing ionic strength. At conditions of slower exchange kinetics, the shells are characterized by an effective pore size of less than about 4 nm.

Preparation of integrin alpha(v)beta3-targeting Ab 38C2 constructs

This protocol describes the preparation of Ab constructs using agents that target cells expressing integrins alpha(v)beta3 and alpha(v)beta5, and the monoclonal aldolase Ab 38C2. The targeting agents are equipped with a diketone or vinylketone linker, and selectively react through the reactive Lys residues in the Ab binding sites to form 38C2 conjugates or chemically programmed 38C2 (i.e., cp38C2). The targeting agent possessing a diketone linker reacts with the Lys residues forming an enaminone derivative. By contrast, the vinylketone linker is used as the corresponding acetone adduct (i.e., a pro-vinylketone linker), and this pro-adapter undergoes a 38C2-catalyzed retro-aldol reaction to produce the vinylketone linker, which forms a Michael-type adduct with the Lys residues. The Ab construct formation is achieved in <1 h for the diketone compounds at ambient temperature, and in 2-16 h using the pro-vinylketone linker at 37 degrees C. The 38C2 constructs are retargeted to cells over-expressing integrins, and are potential candidates for immunotherapy.

Antitenascin-C monoclonal antibody radioimmunotherapy for malignant glioma patients

Adults with primary malignant glioma have an unacceptably poor outcome. Most of these tumors recur at or adjacent to the site of origin, which indicates that failure to eradicate local tumor growth is a major factor contributing to poor outcome. Therefore, locoregional therapies may improve local control and overall outcome for malignant glioma patients. Malignant gliomas selectively express several factors that are not present on normal CNS tissue. Regional administration of radiolabeled monoclonal antibodies targeting tumor-specific antigens expressed by malignant gliomas offers an innovative therapeutic strategy that has recently demonstrated encouraging antitumor activity and acceptable toxicity in clinical trials at a number of centers. Most studies have utilized monoclonal antibodies against tenascin-C, an extracellular matrix glycoprotein ubiquitously expressed by malignant gliomas. This review summarizes clinical trials performed using radiolabeled antitenascin-C monoclonal antibodies for malignant glioma patients to date and highlights future plans to further develop this therapeutic strategy.