title: Differential killing of CD56-expressing cells by drug-conjugated human antibodies targeting membrane-distal and membrane-proximal non-overlapping epitopes.
abstract: CD56 (NCAM, neural cell adhesion molecule) is over-expressed in many tumor types, including neuroblastoma, multiple myeloma, small cell lung cancer, ovarian cancer, acute myeloid leukemia, NK-T lymphoma, neuroendocrine cancer and pancreatic cancer. Using phage display, we identified 2 high-affinity anti-CD56 human monoclonal antibodies (mAbs), m900 and m906, which bound to spatially separated non-overlapping epitopes with similar affinity (equilibrium dissociation constant 2.9 and 4.5 nM, respectively). m900 bound to the membrane proximal fibronectin type III-like domains, whereas m906 bound to the N-terminal IgG-like domains. m906 induced significant down-regulation of CD56 in 4 neuroblastoma cell lines tested, while m900-induced downregulation of CD56 was much lower. Antibody-drug conjugates (ADCs) made by conjugation with a highly potent pyrrolobenzodiazepine dimer (PBD) exhibited killing activity that correlated with CD56 down-regulation, and to some extent with in vivo binding ability of the antibodies. The m906PBD ADC was much more potent than m900PBD, likely due to higher CD56-mediated downregulation and stronger binding to cells. Treatment with m906PBD ADC resulted in very potent cytotoxicity (IC50: 0.05-1.7 pM). These results suggest a novel approach for targeting CD56-expressing neuroblastoma cells. Further studies in animal models and in humans are needed to find whether these antibodies and their drug conjugates are promising candidate therapeutics.
authors.affiliation: a Protein Interactions Section, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute , Frederick , MD , USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Feng
authors.affiliation: a Protein Interactions Section, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute , Frederick , MD , USA.|b Geneva Foundation , Tacoma , WA , USA.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Wang
authors.affiliation: a Protein Interactions Section, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute , Frederick , MD , USA.
authors.forename: Zhongyu
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: a Protein Interactions Section, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute , Frederick , MD , USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: c Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia , Philadelphia , PA , USA.
authors.forename: Robyn T
authors.initials: RT
authors.lastname: Sussman
authors.affiliation: c Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia , Philadelphia , PA , USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Randall
authors.affiliation: c Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia , Philadelphia , PA , USA.|d Department of Pediatrics , Perelman School of Medicine at the University of Pennsylvania , Philadelphia , PA , USA.
authors.forename: Kristopher R
authors.initials: KR
authors.lastname: Bosse
authors.affiliation: c Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia , Philadelphia , PA , USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Maris
authors.affiliation: a Protein Interactions Section, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute , Frederick , MD , USA.
authors.forename: Dimiter S
authors.initials: DS
authors.lastname: Dimitrov
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000915:Antibody Affinity; D000970:Antineoplastic Agents / Q000494:pharmacology*; D019002:CD56 Antigen / Q000276:immunology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000939:Epitopes; D006801:Humans; D018796:Immunoconjugates / Q000494:pharmacology*; D009447:Neuroblastoma / Q000276:immunology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D019002:CD56 Antigen; D000939:Epitopes; D018796:Immunoconjugates; C522918:NCAM1 protein, human
keywords: Antibody-drug conjugates; CD56 internalization; CD56-targeting therapy; PBD; neuroblastoma; therapeutic antibodies