title: Ocaratuzumab, an Fc-engineered antibody demonstrates enhanced antibody-dependent cell-mediated cytotoxicity in chronic lymphocytic leukemia.
abstract: Chronic lymphocytic leukemia (CLL) is common in both developed and developing nations where the need for inexpensive and convenient administration of therapy is apparent. Ocaratuzumab is a novel Fc-engineered humanized IgG1 anti-CD20 monoclonal antibody (mAb) designed for effective antibody-dependent cell-mediated cytotoxicity (ADCC) at very low concentrations that may facilitate sub-cutaneous (vs. intravenous) dosing. Here, we report ocaratuzumab's potency against CLL cells. In vitro assessment of ocaratuzumab's direct cytotoxicity (DC), complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and ADCC was performed on CLL cells. Ocaratuzumab induced DC, CDC, and ADCP similarly to rituximab or ofatumumab (anti-CD20 mAbs). However, ocaratuzumab showed an advantage in NK cell-mediated ADCC over these antibodies. In allogeneic ADCC, [E:T (effector:target) ratios = 25:1, 12:1, 6:1], ocaratuzumab (10 µg/mL) improved ADCC by ~3-fold compared with rituximab or ofatumumab (P<0.001 all tested E:T ratios). Notably, the superiority of ocaratuzumab-induced ADCC was observed at low concentrations (0.1-10 ug/ml; P<0.03; allogeneic assays). In extended allogeneic ADCC E:T titration, ocaratuzumab (0.1 µg/mL) demonstrated 19.4% more cytotoxicity than rituximab (E:T = 0.38:1; P = 0.0066) and 21.5% more cytotoxicity than ofatumumab (E:T = 1.5:1; P = 0.0015). In autologous ADCC, ocaratuzumab (10 µg/mL) demonstrated ~1.5-fold increase in cytotoxicity compared with rituximab or ofatumumab at all E:T ratios tested (E:Ts = 25:1,12:1,6:1; all P<0.001). Obinutuzumab, a glyco-engineered anti-CD20 mAb, showed no improvement in ADCC activity compared with ocaratuzumab. The enhanced ADCC of ocaratuzumab suggests that it may be effective at low concentrations. If supported by clinical investigation, this feature could potentially allow for subcutaneous dosing at low doses that could expand the potential of administering chemoimmunotherapy in developing countries.
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Cheney
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Stephens
authors.affiliation: Center for Biostatistics; The Ohio State University; Columbus, OH USA.
authors.forename: Xiaokui
authors.initials: X
authors.lastname: Mo
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Sarwish
authors.initials: S
authors.lastname: Rafiq
authors.affiliation: Division of Pulmonary Medicine; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Butchar
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Flynn
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Jones
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Kami
authors.initials: K
authors.lastname: Maddocks
authors.affiliation: Mentrik Biotech, LLC; Dallas, TX USA.
authors.forename: Adrienne
authors.initials: A
authors.lastname: O'Reilly
authors.affiliation: Mentrik Biotech, LLC; Dallas, TX USA.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Ramachandran
authors.affiliation: Division of Pulmonary Medicine; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Susheela
authors.initials: S
authors.lastname: Tridandapani
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA.
authors.forename: Natarajan
authors.initials: N
authors.lastname: Muthusamy
authors.affiliation: Division of Hematology; Department of Internal Medicine; The Ohio State University; Columbus, OH USA; Division of Medicinal Chemistry; College of Pharmacy; The Ohio State University; Columbus, OH USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Byrd
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized / Q000235:genetics / Q000276:immunology* / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived / Q000276:immunology / Q000627:therapeutic use; D000920:Antibody-Dependent Cell Cytotoxicity; D018951:Antigens, CD20 / Q000276:immunology; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use; D007694:Killer Cells, Natural / Q000276:immunology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology* / Q000628:therapy*; D010587:Phagocytosis / Q000276:immunology; D015202:Protein Engineering; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D000069283:Rituximab; C527517:ofatumumab; C550337:ocaratuzumab
keywords: AME-133v; CD20; antibody dependent cell mediated cytotoxicity; chronic lymphocytic leukemia; monoclonal antibody