title: Understanding the role of cross-arm binding efficiency in the activity of monoclonal and multispecific therapeutic antibodies.
abstract: Antibodies are essential components of the adaptive immune system that provide protection from extracellular pathogens and aberrant cells in the host. Immunoglobulins G, which have been adapted for therapeutic use due to their exquisite specificity of target recognition, are bivalent homodimers composed of two antigen binding Fab arms and an immune cell recruiting Fc module. In recent years significant progress has been made in optimizing properties of both Fab and Fc components to derive antibodies with improved affinity, stability, and effector function. However, systematic analyses of the efficiency with which antibodies crosslink their targets have lagged, despite the well-recognized importance of this cross-arm binding for optimal antigen engagement. Such an understanding is particularly relevant given the variety of next-generation multispecific antibody scaffolds under development. In this manuscript we attempt to fill this gap by presenting a framework for analysis and optimization of antibody cross-arm engagement. We illustrate the power of this integrated approach by presenting case studies for rational multispecific antibody design based on quantitative assessment of the interplay between antibody valency, target expression, and cross-arm binding efficiency. We conclude that optimal design parameters for cross-arm binding strongly depend on the biological context of the disease, and that cross-arm binding efficiency needs to be considered for successful application of multispecific antibodies.
authors.affiliation: Merrimack Pharmaceuticals Inc., 1 Kendall Sq., Ste. B7201, Cambridge, MA 02139, USA. Electronic address: bharms@merrimackpharma.com.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Harms
authors.affiliation: Merrimack Pharmaceuticals Inc., 1 Kendall Sq., Ste. B7201, Cambridge, MA 02139, USA.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Kearns
authors.affiliation: Merrimack Pharmaceuticals Inc., 1 Kendall Sq., Ste. B7201, Cambridge, MA 02139, USA.
authors.forename: Sergio
authors.initials: S
authors.lastname: Iadevaia
authors.affiliation: Merrimack Pharmaceuticals Inc., 1 Kendall Sq., Ste. B7201, Cambridge, MA 02139, USA. Electronic address: alugovskoy@merrimackpharma.com.
authors.forename: Alexey A
authors.initials: AA
authors.lastname: Lugovskoy
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000737:chemistry* / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000494:pharmacology; D000918:Antibody Specificity; D002460:Cell Line; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry; D020128:Inhibitory Concentration 50; D011485:Protein Binding; D015202:Protein Engineering; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D020893:Receptor, ErbB-3 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D017526:Receptor, IGF Type 1; C508053:ERBB2 protein, human; C581292:ERBB3 protein, human
keywords: Avidity; Bispecific antibody; Computational modeling; Cross-arm binding; HER2; HER3; HRG; IGF-1; IGF-1R; Immunoglobulin; Multispecific antibodies; dsIgG; dual-specific IgG; heregulin; human epidermal growth factor receptor 2; human epidermal growth factor receptor 3; insulin-like growth factor-1; insulin-like growth factor-1 receptor; pAKT; phosphorylated AKT