Kinetic Approach to Pathway Attenuation Using XOMA 052, a Regulatory Therapeutic Antibody That Modulates Interleukin-1β Activity

Abstract

Many therapeutic antibodies act as antagonists to competitively block cellular signaling pathways. We describe here an approach for the therapeutic use of monoclonal antibodies based on context-dependent attenuation to reduce pathologically high activity while allowing homeostatic signaling in biologically important pathways. Such attenuation is achieved by modulating the kinetics of a ligand binding to its various receptors and regulatory proteins rather than by complete blockade of signaling pathways. The anti-interleukin-1␤ (IL-1␤) antibody XOMA 052 is a potent inhibitor of IL-1␤ activity that reduces the affinity of IL-1␤ for its signaling receptor and co-receptor but not for its decoy and soluble inhibitory receptors. This mechanism shifts the effective dose response of the cytokine so that the potency of IL-1␤ bound by XOMA 052 is 20 -100-fold lower than that of IL-1␤ in the absence of antibody in a variety of in vitro cell-based assays. We propose that by decreasing potency of IL-1␤ while allowing binding to its clearance and inhibitory receptors, XOMA 052 treatment will attenuate IL-1␤ activity in concert with endogenous regulatory mechanisms. Furthermore, the ability to bind the decoy receptor may reduce the potential for accumulation of antibody⅐target complexes. Regulatory antibodies like XOMA 052, which selectively modulate signaling pathways, may represent a new mechanistic class of therapeutic antibodies.

Detailed Mechanistic Analysis of Gevokizumab, an Allosteric Anti–IL-1βAntibody with Differential Receptor-Modulating Properties

“…Gevokizumab antibody binding fragment (Fab) was expressed transiently in human embryonic kidney 293E cells using the corresponding heavy chain and light chain genes encoding the Fab fragment. Control blocking antibody 5 (Ab5) is an IgG 1 lambda synthesized by fusing the variable region sequences reported for a receptor-blocking antibody to the appropriate human constant regions (Roell et al, 2010). The isotype control antibody was an anti-keyhole limpet hemocyanin human IgG 2 lambda antibody (clone KLH8.G2; generated at XOMA, Berkeley, CA).…”

“…HeLa cells stably transfected with a nuclear factor-kB (NF-kB) luciferase reporter plasmid (Biomyx, San Diego, CA) were plated in assay buffer (Dulbecco's modified Eagle's/F12 medium with 10% fetal bovine serum) and incubated at 37°C overnight. Activity was assayed as described previously (Roell et al, 2010). In brief, for the IL-1b neutralization assay, increasing amounts of IL-1b were preincubated for 2 hours at room temperature with increasing concentrations of antagonist prior to addition to the reporter cells.…”

“…Binding of sIL-1RAcP to sIL-1RI·IL-1b or sIL-1RI·IL-1b·gevokizumab complexes was performed as described previously (Roell et al, 2010).…”

“…Gevokizumab is currently in development to address significant unmet medical needs, including noninfectious uveitis, Behçet's uveitis, cardiovascular disease, and other autoinflammatory diseases (Bhaskar et al, 2011;Gul et al, 2012). We have shown previously that gevokizumab does not block the interaction of IL-1b with the soluble receptors sIL-1RI, sIL-1RII, and sIL-1RAcP (Roell et al, 2010). Herein, we describe detailed binding parameters for the interactions that underlie the mechanistic basis for regulation of IL-1b signaling using two different methods: 1) Schild analysis with an IL-1b reporter cell line, and 2) labelfree surface plasmon resonance (SPR) with purified protein components of the system.…”

International Union of Basic and Clinical Pharmacology. XC. Multisite Pharmacology: Recommendations for the Nomenclature of Receptor Allosterism and Allosteric Ligands

“…Another interesting example that increases the diversity and complexity of receptor allosterism involves the anti-interleukin-1b (IL-1b) monoclonal antibody gevokizumab, which was recently shown to exert its highly specific and context-dependent inhibitory effects via a classic allosteric ternary complex mechanism (Roell et al, 2010;Issafras et al, 2014). However, rather than interacting with an allosteric site on the IL-1b receptor, gevokizumab acts on the orthosteric agonist (IL-1b) itself, changing its subsequent interactive properties with the orthosteric site on the receptor.…”