CD47 is a ubiquitously expressed immune checkpoint receptor that is often upregulated in cancer. CD47 interacts with its counter-receptor SIRPα on macrophages and other myeloid cells to inhibit cancer cell phagocytosis and drive immune evasion. To overcome tolerability and "antigen sink" issues arising from widespread CD47 expression, we generated dual-targeting bispecific antibodies that selectively block the CD47-SIRPα interaction on malignant cells expressing a specific tumor-associated antigen; e.g., CD19 or mesothelin. These bispecific κλ bodies are fully human, native IgG1 molecules, combining tumor targeting and selective CD47 blockade with immune activating mechanisms mediated by the Fc portion of the antibody. CD47-neutralizing κλ bodies efficiently kill cancer cells in vitro and in vivo but interact only weakly with healthy cells expressing physiological levels of CD47. Accordingly, a κλ body administered to non-human primates showed a typical IgG pharmacokinetic profile and was well tolerated. Importantly, κλ bodies preserve their tumoricidal capabilities in the presence of a CD47 antigen sink. Thus, dual-targeting κλ bodies allow for efficacious yet safe targeting of CD47 in cancer. Such a bispecific design could be applied to limit the extent of neutralization of other ubiquitously expressed therapeutic targets.
Keywords: CD19; CD47; bispecific antibody; cancer immunotherapy; immune checkpoint; macrophage; mesothelin; phagocytosis; pharmacokinetics.
Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.