Soluble Papain to Digest Monoclonal Antibodies; Time and Cost-Effective Method to Obtain Fab Fragment

Bispecific FpFs: a versatile tool for preclinical antibody development

We previously described FpFs 1̲ (Fab-PEG-Fab) as binding mimetics of IgGs. FpFs are prepared with di(bis-sulfone) conjugation reagents 3̲ that undergo disulfide rebridging conjugation with the accessible disulfide of each Fab (Scheme 1). We have now prepared bispecific FpFs 2̲ (bsFpF and Fab1-PEG-Fab2) as potential bispecific antibody mimetics with the intent that bsFpFs could be used in preclinical antibody development since sourcing bispecific antibodies may be challenging during preclinical research. The di(bis-sulfone) reagent 3̲ was first used to prepare a bsFpF 2̲ by the sequential conjugation of a first Fab and then a second Fab to another target (Scheme 2). Seeking to improve bsFpF synthesis, the asymmetric conjugation reagent, bis-sulfone bis-sulfide 1̲6̲, with different thiol conjugation reactivities at each terminus (Scheme 4) was examined and the bsFpFs appeared to be formed at similar conversion to the di(bis-sulfone) reagent 3̲. To explore the advantages of using common intermediates in the preparation of bsFpF families, we investigated bsFpF synthesis with a protein conjugation-ligation approach (Scheme 5). Reagents with a bis-sulfone moiety for conjugation on one PEG terminus and a ligation moiety on the other terminus were examined. Bis-sulfone PEG trans-cyclooctene (TCO) 2̲8̲ and bis-sulfone PEG tetrazine (Tz) 3̲0̲ were used to prepare several bsFpFs targeting various therapeutic targets (TNF-α, IL6R, IL17, and VEGF) and tissue affinity targets (hyaluronic acid and collagen II). Surface plasmon resonance (SPR) binding studies indicated that there was little difference between the dissociation rate constant (k d) for the unmodified Fab, mono-conjugated PEG-Fab and the corresponding Fab in a bsFpF. The Fab association rate (k a) in the bsFpF was slower than for PEG-Fab, which may be because of mass differences that influence SPR results. These observations suggest that each Fab will bind to its target independently of the other Fab and that bsFpF binding profiles can be estimated using the corresponding PEG-Fab conjugates.

Production of an Efficient Enzymatically Fab Fragment Antivenom against Cobra Snake (Naja naja oxiana) Venom

Since around 100 years ago, the best treatment for millions of global snakebite victims has been polyclonal antivenoms. However, common antivenoms need continuous improvement to reduce rare, their side effects and get better performance. In the present study, Fab antivenom was produced through papain digestion of anti-cobra venom plasma, multi-step purification, and optimization, including ammonium sulfate precipitation and DEAE-cellulose column chromatography. Then, the existence of the corresponding Fab fragment antibody was seen and confirmed by SDS-PAGE method and double immunodifusion (Ouchterlony) test. In addition, the potency test in NIH laboratory mice revealed that each milliliter of the new Fab antivenom was able to neutralize 624 micrograms and (80LD50) of cobra venom, which is about 15% more efficient than the primary plasma of the same concentration, and 1.57 times more effective than the cobra antivenom found in commercial hexavalent antivenom of Razi Institute. According to the findings, it seems that this new Fab antivenom can be used as a new candidate for treatment of cobra snakebite victims.

Direct Comparison of the Hinge-Cleaving Proteases IgdE and BdpK for LC-MS-Based IgG1 Clonal Profiling

Human antibodies are heterogeneous molecules primarily due to clonal sequence variations. Analytical techniques to assess antibody levels quantitatively, such as ELISA, lack the power to resolve abundances at the clonal level. Recently, we introduced an LC-MS-based approach that can distinguish and quantify antibody clones using the mass and retention time of their corresponding Fab-fragments. We used specific hinge-cleaving protease IgdE (FabALACTICA) to release the Fab-fragments from the constant Fc region of the antibody. Here, we explore an alternative IgG1 hinge-cleaving protease, BdpK (FabDELLO), and compare it directly to IgdE for use in IgG1 repertoire profiling. We used IgdE and BdpK in parallel to digest all IgG1s from the same set of plasma samples. Both proteases cleave IgG1 specifically in the hinge, albeit via different mechanisms and at two distinct cleavage sites. Notwithstanding these differences, the Fab fragments generated by IgdE or BdpK produced highly similar clonal repertoires. However, IgdE required ∼16 h of incubation to digest plasma IgG1s, while BdpK required ∼2 h. We authenticated the similarity of the clones by top-down proteomics using electron transfer dissociation. We conclude that BdpK performs very well in digesting polyclonal plasma IgG1s and that neither BdpK nor IgdE displays detectable biases in cleaving IgG1s. We anticipate that BdpK may emerge as the preferred protease for IgG1 hinge-digestion because it offers a shorter digestion time compared to IgdE, an equally specific digestion site, and no bias against any IgG1 present in plasma.

Surface modification strategies in translocating nano-vesicles across different barriers and the role of bio-vesicles in improving anticancer therapy

Nanovesicles and bio-vesicles (BVs) have emerged as promising tools to achieve targeted cancer therapy due to their ability to overcome many of the key challenges currently being faced with conventional chemotherapy. These challenges include the diverse and often complex pathophysiology involving the progression of cancer, as well as the various biological barriers that circumvent therapeutic molecules reaching their target site in optimum concentration. The scientific evidence suggests that surface-functionalized nanovesicles and BVs camouflaged nano-carriers (NCs) both can bypass the established biological barriers and facilitate fourth-generation targeting for the improved regimen of treatment. In this review, we intend to emphasize the role of surface-functionalized nanovesicles and BVs camouflaged NCs through various approaches that lead to an improved internalization to achieve improved and targeted oncotherapy. We have explored various strategies that have been employed to surface-functionalize and biologically modify these vesicles, including the use of biomolecule functionalized target ligands such as peptides, antibodies, and aptamers, as well as the targeting of specific receptors on cancer cells. Further, the utility of BVs, which are made from the membranes of cells such as mesenchymal stem cells (MSCs), white blood cells (WBCs), red blood cells (RBCs), platelets (PLTs) as well as cancer cells also been investigated. Lastly, we have discussed the translational challenges and limitations that these NCs can encounter and still need to be overcome in order to fully realize the potential of nanovesicles and BVs for targeted cancer therapy. The fundamental challenges that currently prevent successful cancer therapy and the necessity of novel delivery systems are in the offing.

The Dawn of a New Era: Targeting the "Undruggables" with Antibody-Based Therapeutics

The high selectivity and affinity of antibodies toward their antigens have made them a highly valuable tool in disease therapy, diagnosis, and basic research. A plethora of chemical and genetic approaches have been devised to make antibodies accessible to more "undruggable" targets and equipped with new functions of illustrating or regulating biological processes more precisely. In this Review, in addition to introducing how naked antibodies and various antibody conjugates (such as antibody-drug conjugates, antibody-oligonucleotide conjugates, antibody-enzyme conjugates, etc.) work in therapeutic applications, special attention has been paid to how chemistry tools have helped to optimize the therapeutic outcome (i.e., with enhanced efficacy and reduced side effects) or facilitate the multifunctionalization of antibodies, with a focus on emerging fields such as targeted protein degradation, real-time live-cell imaging, catalytic labeling or decaging with spatiotemporal control as well as the engagement of antibodies inside cells. With advances in modern chemistry and biotechnology, well-designed antibodies and their derivatives via size miniaturization or multifunctionalization together with efficient delivery systems have emerged, which have gradually improved our understanding of important biological processes and paved the way to pursue novel targets for potential treatments of various diseases.

Real-time monitoring of papain digestion of antibodies immobilized with various strategies by optical interferometry

Antigen binding fragments (Fabs) employed in research are typically generated by the papain digestion of monoclonal antibodies. However, the interaction between papain and antibodies at the interface remains unclear. Herein, we developed ordered porous layer interferometry for the label-free monitoring of the interaction between the antibody and papain at liquid-solid interfaces. Human immunoglobulin G (hIgG) was used as the model antibody, and different strategies were employed to immobilize it on the surface of silica colloidal crystal (SCC) films which are optical interferometric substrates. It was observed that different immobilization strategies induced different changes in the optical thickness (OT) of SCCs. The order of rate of the changes of OT from largest to smallest was IgG immobilized by protein A orientation, glutaraldehyde coupling, and physical adsorption. This phenomenon can be explained by the varied orientations of the antibodies created at the interface by the different modification procedures. The Fab-up orientation maximized the exposure of the hinge region sulfhydryl group and easily underwent conformational transitions because hIgG was immobilized by protein A. This process stimulates papain to produce the highest degree of activity, resulting in the greatest decrease in OT. This study provides insights into the catalysis of papain on antibodies.