title: Interleukin-2 enhancement of cytotoxicity by humanized monoclonal antibody M195 (anti-CD33) in myelogenous leukemia.
abstract: Humanized M195 (HuM195) is a genetically engineered, human IgG1 version of the parent M195, a mouse immunoglobulin G2a, anti-CD33 monoclonal antibody which reacts with early myeloid progenitor cells and myelogenous leukemia cells. In Phase I studies in patients with relapsed and refractory myelogenous leukemia, HuM195 safely targeted to sites of disease and was nonimmunogenic. HuM195 shows only modest capability of antibody-dependent cellular cytotoxicity (ADCC) against target HL60 cells and minimal cytolytic activity mediated by human complement. Therefore, efforts were made to enhance ADCC using cytokines. gamma-Interferon, granulocyte-macrophage colony-stimulating factor, and granulocyte colony-stimulating factor did not promote neutrophil-mediated ADCC with HuM195. However, interleukin-2 (IL-2) showed a range of 2-6-fold increases in ADCC against fresh myelogenous leukemia cells and HL60 cells over that seen with HuM195 or low-dose IL-2 alone. ADCC potency was not improved further by the use of homodimeric HuM195. Flow cytometry and Fc receptor-blocking experiments showed that CD16(+) cells were essential for IL-2-enhanced ADCC. As compared to HL60 cells, a multidrug-resistant line of HL60 cells was at least as susceptible to killing by IL-2 or HuM195 or in combination, suggesting that the mechanism of killing may be active against cells surviving and resistant to chemotherapy. Since these in vitro levels of IL-2 and HuM195 can be safely achieved in patients, the enhancement of HuM195 ADCC with low-dose IL-2 is a possible strategy that may be used in vivo to eliminate minimal disease in future trials of patients with myeloid leukemias.
authors.affiliation: Department of Medicine, Clinical Immunology and Leukemia Services, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: P C
authors.initials: PC
authors.lastname: Caron
authors.forename: L T
authors.initials: LT
authors.lastname: Lai
authors.forename: D A
authors.initials: DA
authors.lastname: Scheinberg
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000633:toxicity*; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects / Q000502:physiology; D015703:Antigens, CD / Q000502:physiology; D000970:Antineoplastic Agents / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects*; D016207:Cytokines / Q000494:pharmacology*; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology*; D020014:K562 Cells; D007951:Leukemia, Myeloid / Q000188:drug therapy / Q000276:immunology / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D011961:Receptors, Fc / Q000502:physiology; D017452:Receptors, IgG / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000970:Antineoplastic Agents; D016207:Cytokines; D007376:Interleukin-2; D011961:Receptors, Fc; D017452:Receptors, IgG; D011994:Recombinant Proteins; C101579:monoclonal antibody M195; D016179:Granulocyte Colony-Stimulating Factor; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor