Radiotracer Imaging of Unstable Plaque
Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer in Cardiovascular Molecular Imaging, 2007
Despite the improved specific activity achieved at the target site using the charge-modified antibody, there are limitations due to both the 111In tag and to nonspecific antibody uptake contributing to background activity. Although smaller than whole antibodies, antibody fragments are still relatively large molecules and therefore have relatively slow blood pool clearance. Transchelation of 111In is a problem, especially to bone (ribs and clavicle) in SPECT imaging looking for focal uptake in coronary arteries in the thorax. There are further modifications that can improve the performance of Z2D3 imaging, which is to develop a bispecific antibody approach. In this approach, first a bispecific antibody with one functional unit that binds the antigen is injected. This molecule stays on the surface of the targeted cells but is phagocytosed into cells in the reticuloendothelial system that is a major contributing factor to high background activity. After a period of time (12 to 24 hours) to allow the bispecific antibody to clear from the blood pool and to be phagocytosed, a second small molecule with a radio tag directed against the second functional unit on the bispecific antibody is injected.
Bispecific Antibodies
Siegfried Matzku, Rolf A. Stahel in Antibodies in Diagnosis and Therapy, 2019
The simplest way of preparing a bispecific antibody is to chemically crosslink two antibodies using reagents that randomly link the antibodies by amino acid side chain groups, usually ε-amino groups on lysine residues (Segal, 1993; Carlson et al., 1978; Karpovsky et al., 1984; Segal and Bast, 1995) (Figure 2A). The most commonly used reagents for preparing such bsAbs use dithiol exchange reactions, which greatly favor the formation of hetero- over homoconjugates. Randomly crosslinked heteroconjugates work well for most in vitro applications, where, for example, a receptor on a cytotoxic cell needs to be linked to a cell surface component on a target cell. However, because of their heterogeneity in size and chemical composition, and because of variability between batches, heteroconjugates would not give consistent results in vivo, where size and composition greatly effect biodistribution and stability. Instead, homogeneous bispecific molecules are greatly preferred for in vivo animal and clinical studies. Two types of homogeneous bsAbs, the hybrid-hybridoma and the hinge-linked hetero-F(ab’)2 are currently in use, but a number of genetically engineered constructs have recently been described that hold great promise for simplifying the preparation of bispecific molecules. The different types of bsAbs are reviewed in this section.
Antibody-Based Therapies
David E. Thurston, Ilona Pysz in Chemistry and Pharmacology of Anticancer Drugs, 2021
Other types of bispecific antibody formats have been designed to overcome certain problems, such as short half-life, immunogenicity, and side effects caused by cytokine liberation. They include chemically linked Fabs [e.g., F(ab’)2]consisting of only the Fab regions (Figure 7.51B), and various types of bivalent and trivalent single-chain variable fragments (scFvs) with fusion proteins mimicking the variable domains of two different antibodies. The most developed of these newer formats are the bispecific T-cell engagers (BiTEs) and mAb2’s, antibody fragments engineered to contain an Fcab antigen-binding fragment instead of the Fc constant region (Figure 7.51C). These different bsMAb formats are explored below in more detail.
Discovery and optimization of a novel anti-GUCY2c x CD3 bispecific antibody for the treatment of solid tumors
Published in mAbs, 2021
Adam R. Root, Gurkan Guntas, Madan Katragadda, James R. Apgar, Jatin Narula, Chew Shun Chang, Sara Hanscom, Matthew McKenna, Jason Wade, Caryl Meade, Weijun Ma, Yongjing Guo, Yan Liu, Weili Duan, Claire Hendershot, Amy C. King, Yan Zhang, Eric Sousa, Amy Tam, Susan Benard, Han Yang, Kerry Kelleher, Fang Jin, Nicole Piche-Nicholas, Sinead E. Keating, Fernando Narciandi, Rosemary Lawrence-Henderson, Maya Arai, Wayne R. Stochaj, Kristine Svenson, Lidia Mosyak, Khetemcnee Lam, Christopher Francis, Kimberly Marquette, Liliana Wroblewska, H. Lily Zhu, Alfredo Darmanin Sheehan, Edward R. LaVallie, Aaron M. D’Antona, Alison Betts, Lindsay King, Edward Rosfjord, Orla Cunningham, Laura Lin, Puja Sapra, Lioudmila Tchistiakova, Divya Mathur, Laird Bloom
The value of the high-throughput protein production system employed in this work was underscored by the need to optimize multiple properties and the observation that optimizing one property can come at the expense of another. For example, removal of predicted T cell epitopes in the anti-CD3 domain led to loss of affinity, and phage selection yielding thermostable GUCY2C domains did not produce hits that altered the H54/H55 asparagine deamidation site despite use of a library designed to do so. The production and testing of over 1600 variants at the 1 mg scale compensated for the relative rarity of designs that achieved a balance among the set of targeted biophysical and functional properties. The availability of protein in formats attuned to specific assays (for example, the rapid thermal stability assay in the scFv-Fc format and affinity measurements in monovalent Fc format) ensured that sequence variants contributing to antibody stability, posttranslational modification, and potential immunogenicity could be evaluated thoroughly. The availability in parallel of proteins in the final therapeutic format – over 500 BsAb were produced for the program – enabled rapid identification of molecules that successfully combined the outputs of multiple strands of optimization. The final result was a well-behaved bispecific antibody suitable for manufacturing and clinical development.
Preliminary Report on Interleukin-22, GM-CSF, and IL-17F in the Pathogenesis of Acute Anterior Uveitis
Published in Ocular Immunology and Inflammation, 2021
Jerry Chien-Chieh Huang, Matthew Schleisman, Dongseok Choi, Claire Mitchell, Lindsey Watson, Mark Asquith, James T. Rosenbaum
Second, we noted increased IL-17A production by CD8 cells from subjects with AAU. An increase in IL-17A and IL-17F synthesis was noted among MAIT-like cells with AAU. IL-17 has been strongly implicated in spondyloarthritis24, in rodent models of uveitis25,26, and in patients with uveitis.27 However, clinical trials to block IL-17 as a treatment for uveitis have yielded inconsistent results.27,28 An abstract presentation has suggested that blocking IL-17 in patients with spondyloarthritis might reduce the frequency of recurrent AAU (Deodhar, A, presented at EULAR (European League Against Rheumatism), Amsterdam, June, 2018). We believe that this is the first study to implicate IL-17F in the pathogenesis of uveitis. We noted an increase in IL-17F frequency among stimulated MAIT-like cells. IL-17 has several isoforms including predominantly IL-17A and IL-17F. Most clinical trials to date have targeted just IL-17A. A bispecific antibody, bimekizumab, that targets both IL-17A and IL-17F, has shown promising results in a number of clinical trials including one for the treatment of ankylosing spondylitis.29 Our observations support the rationale to use a bispecific antibody.
Characterization and analysis of scFv-IgG bispecific antibody size variants
Published in mAbs, 2018
Mingyan Cao, Chunlei Wang, Wai Keen Chung, Dana Motabar, Jihong Wang, Elizabeth Christian, Shihua Lin, Alan Hunter, Xiangyang Wang, Dengfeng Liu
More than 100 bispecific antibody formats have been reported in the literature.9,11 This diversity is the result of a large number of bispecific “building blocks” that include antigen-binding fragments (Fabs), single-chain variable fragments (scFvs), and receptor ligands. Bispecific antibody formats can be broadly classified into three groups. Constructions of these three different groups of bispecific antibody formats are shown in Supplementary Figure S1. Those in the first group do not possess fragment crystallizable (Fc) regions (i.e., are Fc-less) and have two antigen-binding sites connected by a flexible linker (e.g., Blincyto®).16–19 The second group consists of immunoglobulin G (IgG)-like bispecific antibodies with an asymmetrical architecture in which the two binding arms of the antibody have different targets, and hence different structures (e.g., Removab® and Hemlibra®).20–23 The third group comprises appended IgGs with symmetrical architecture, in which the second binding site is fused to either the IgG heavy or light chain. This format was first reported by Coloma and Morrison in 1997.24 Since then, the secondary binding site, often in an scFv format, has been fused to the C terminus/N terminus of the heavy chain, the hinge region, the C terminus/N terminus of the light chain, the CH3 domain of the heavy chain, or other regions.25–27
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