title: Antigen-dependent internalization is related to rapid elimination from plasma of humanized anti-HM1.24 monoclonal antibody.
abstract: Anti-HM1.24 monoclonal antibody (AHM) is a humanized anti-HM1.24 monoclonal antibody that binds to the HM1.24 antigen, a protein that is highly expressed in multiple myeloma cells. The pharmacokinetics of AHM was determined in experiments in which AHM was administered intravenously to cynomolgus monkeys. The area under the plasma concentration-time curve increased by more than the dose ratio between 2 and 20 mg/kg, and nonlinear pharmacokinetics was observed. The elimination half-life of AHM from the plasma was 7.56 h at 2 mg/kg and 28.6 h at 20 mg/kg, which was shorter than that observed for other therapeutic humanized monoclonal antibodies, such as trastuzumab and bevacizumab. Although antibodies to AHM were detected in all monkeys on or after 10 days of administration, there was a temporal disassociation between the rapid elimination of AHM and the appearance of anti-AHM antibodies. HM1.24 antigen-dependent internalization and intracellular metabolism of AHM were investigated in peripheral blood mononuclear, KPMM2, and U937 cells. In all cases, AHM was rapidly internalized from the cell surface; this internalization was significantly prevented by phenylarsine oxide in KPMM2 cells, an inhibitor of receptor-mediated endocytosis, and the internalized AHM was subsequently degraded within the cells. Furthermore, immunofluorescence microscopy revealed that the internalized AHM is delivered to and degraded in late endosomes/lysosomes. Taken together, our results suggest that the rapid elimination of AHM from plasma in monkey is due to HM1.24 antigen-dependent internalization followed by delivery to the lysosomes.
authors.affiliation: Chugai Pharmaceutical Co., Ltd., Fuji-Gotenba Research Laboratories, 1-135 Komakado, Gotenba-shi, Shizuoka 412-8513, Japan. amanojn@chugai-pharm.co.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Amano
authors.forename: Naoko
authors.initials: N
authors.lastname: Masuyama
authors.forename: Yuko
authors.initials: Y
authors.lastname: Hirota
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Igawa
authors.forename: Rie
authors.initials: R
authors.lastname: Shiokawa
authors.forename: Taichi
authors.initials: T
authors.lastname: Okutani
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyayama
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nanami
authors.forename: Masaki
authors.initials: M
authors.lastname: Ishigai
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D015703:Antigens, CD / Q000276:immunology* / Q000502:physiology; D058851:GPI-Linked Proteins / Q000276:immunology / Q000502:physiology; D006801:Humans; D007457:Iodine Radioisotopes; D008247:Lysosomes / Q000378:metabolism; D008252:Macaca fascicularis; D008297:Male; D020298:U937 Cells; D000074010:Bone Marrow Stromal Antigen 2
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D058851:GPI-Linked Proteins; D007457:Iodine Radioisotopes; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2