title: Milatuzumab-SN-38 conjugates for the treatment of CD74+ cancers.
abstract: CD74 is an attractive target for antibody-drug conjugates (ADC), because it internalizes and recycles after antibody binding. CD74 mostly is associated with hematologic tumors but is expressed also in solid cancers. Therefore, ADCs of the humanized anti-CD74 antibody, milatuzumab, were examined for the therapy of CD74-expressing solid tumors. Milatuzumab-doxorubicin and two milatuzumab-SN-38 conjugates with cleavable linkers, differing in their stability in serum and how they release SN-38 in the lysosome, were prepared. CD74 expression was determined by flow cytometry and immunohistology. In vitro cytotoxicity and in vivo therapeutic studies were conducted in the human cancer cell lines A-375 (melanoma), HuH-7 and Hep-G2 (hepatoma), Capan-1 (pancreatic), NCI-N87 (gastric), and Raji Burkitt lymphoma. The milatuzumab-SN-38 ADC was compared with SN-38 ADCs prepared with anti-Trop-2 and anti-CEACAM6 antibodies in xenografts expressing their target antigens. Milatuzumab-doxorubicin was most effective in the lymphoma model, whereas in A-375 and Capan-1 solid tumors, only milatuzumab-SN-38 showed a therapeutic benefit. Despite much lower surface expression of CD74 than Trop-2 or CEACAM6, milatuzumab-SN-38 had similar efficacy in Capan-1 as anti-Trop-2-SN-38, but in NCI-N87, anti-CEACAM6 and anti-Trop-2 conjugates were superior. Studies in two hepatoma lines at a single dose level showed significant benefit over saline controls but not against an irrelevant immunoglobulin G conjugate. CD74 is a suitable target for ADCs in some solid tumor xenografts, with efficacy largely influenced by uniformity of CD74 expression and with SN-38 conjugates providing the best therapeutic responses; SN-38 conjugates were preferable in solid cancers, whereas doxorubicin ADC was better in lymphoma tested.
authors: Immunomedics, Inc., Morris Plains, New Jersey, USA.
authors: Serengulam V
authors: SV
authors: Govindan
authors: Thomas M
authors: TM
authors: Cardillo
authors: Robert M
authors: RM
authors: Sharkey
authors: Fatma
authors: F
authors: Tat
authors: David V
authors: DV
authors: Gold
authors: David M
authors: DM
authors: Goldenberg
mesh_terms: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics* / Q000276:immunology; D000951:Antigens, Neoplasm / Q000378:metabolism; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives; D015815:Cell Adhesion Molecules / Q000378:metabolism; D004317:Doxorubicin / Q000008:administration & dosage; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000276:immunology; D056945:Hep G2 Cells; D000949:Histocompatibility Antigens Class II / Q000235:genetics* / Q000276:immunology; D006801:Humans; D000077146:Irinotecan; D009369:Neoplasms / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D000949:Histocompatibility Antigens Class II; C499380:TACSTD2 protein, human; C045084:invariant chain; C540932:milatuzumab; D000077146:Irinotecan; D004317:Doxorubicin; D002166:Camptothecin