Abstract Neutralizing CD47, the ‘don't eat me signal’ hijacked by different tumor types, is a novel generally applicable therapeutic strategy. Because of a distinct mechanism of action and the ability to stimulate the innate anti-tumor immunity, CD47-neutralizing agents are poised as attractive candidates for combination therapies in association with other immunotherapies. However, the development of general CD47 antagonists could be hindered by the ubiquitous and abundant expression of CD47 on virtually all healthy cells. To overcome potential pharmacological and clinical liabilities of a general CD47 antagonist, we have developed bispecific kappa/lambda bodies, which selectively target CD47 in cancer cells. These kappa/lambda bodies: (i) are full-length bispecific IgGs, (ii) bind with high affinity and neutralize the CD47-SIRP alpha interaction in cancer cells expressing a tumor-associated antigen (TAA), and (iii) mediate efficient cell killing of TAA-positive cancer cells in vitro through Fc-dependent mechanisms such as ADCP (antibody mediated cellular phagocytosis) and ADCC (antibody mediated cellular cytotoxicity). We are currently developing two molecules of this type, one targeting CD47 and CD19 (for B cell malignancies), the other targeting CD47 and mesothelin (for various mesothelin-positive solid tumors). The efficacy of the CD47/CD19 kappa/lambda body was demonstrated in vivo, using two B-cell lymphoma xenograft models in NOD/SCID mice. We also performed a pharmacokinetics study in non-human primates with the CD47/CD19 lead candidate, with the objective of assessing the potential “antigen sink” effect related to ubiquitous CD47 expression on erythrocytes, platelets and other cells. Encouragingly, the CD47/CD19 kappa/lambda body administered in a single dose to cynomolgus monkeys, at 0.5 and 10 mg/kg, showed an acceptable pharmacokinetic profile and the absence of hematological toxicities. The example of the CD47/CD19 kappa/lambda body illustrates the power of the dual-targeting approach for addressing a ubiquitous cell surface receptor such as CD47. Citation Format: Krzysztof Masternak, Lucile Broyer, Elie Dheilly, Stefano Majocchi, Valéry Moine, Giovanni Magistrelli, François Rousseau, Ulla Ravn, Franck Gueneau, Pauline Malinge, Sébastien Calloud, Maud Charreton-Galby, Mireille Guerrier, Nessie Costes, Nicolas Bosson, Gérard Didelot, Lucie Bernard, Vanessa Buatois, Laura Cons, Laurence Chatel, Anne Papaioannou, Zoë Johnson, Walter Ferlin, Marie Kosco-Vilbois, Nicolas Fischer. Neutralizing CD47 in cancer cells with dual targeting kappa/lambda bodies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2482. doi:10.1158/1538-7445.AM2015-2482