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The activation of tumor necrosis factor (TNF)-related apoptosis-inducing ligand receptor 2 (TRAIL-R2)/death receptor 5 (DR5) induces apoptosis in various tumor cells but not in normal human cells. Because some therapeutic antibodies targeting TRAIL-R2 have demonstrated severe hepatotoxicity in clinical applications, novel in vivo models reflecting clinical hepatotoxicity are now required. In this study, we investigated the hepatotoxicity caused by KMTR2, an anti-human TRAIL-R2 monoclonal antibody, in chimeric mice with humanized livers (PXB-mice). PXB-mice were exposed to KMTR2 by single or repeated (weekly for 4 weeks) intravenous administrations, and the analyses of blood chemistry, liver histopathology, hepatic gene expression, and toxicokinetics were performed. Treatment with 1 or 10 mg/kg of KMTR2 increased alanine transaminase (ALT) activity and human ALT1 levels in blood. Histopathological analysis revealed that cell death and degeneration with the infiltration of inflammatory cells in human but not mouse hepatocytes were increased in a time-dependent manner after KMTR2 administration. Furthermore, increases in TdT-mediated dUTP nick end labeling (TUNEL)-positive human hepatocytes and serum concentration of cleaved cytokeratin 18, a human-specific apoptosis marker, were observed. RNA sequence analysis showed that the gene expression profile changed in different manners between human and mouse hepatocytes and the up-regulation of TRAIL-R2-related genes was observed only in human hepatocytes. Taken together, these results indicate that KMTR2-mediated TRAIL-R2 activation induces apoptosis of human hepatocytes and hepatotoxicity in PXB-mice and suggest that chimeric mice with humanized liver can be novel tools for the evaluation of in vivo human-specific hepatotoxicity induced by therapeutic antibodies in pre-clinical studies.

Malignant pleural mesothelioma (MPM) is a rare and highly aggressive neoplasm that arises from the pleural, pericardial, or peritoneal lining. Although surgery, chemotherapy, radiotherapy, and combinations of these therapies are used to treat MPM, the median survival of such patients is dismal. Therefore, there is a compelling need to develop novel therapeutics with different modes of action. Ganglioside GM2 is a glycolipid that has been shown to be overexpressed in various types of cancer. However, there are no published reports regarding the use of GM2 as a potential therapeutic target in cases of MPM. In this study, we evaluated the efficacy of the anti-GM2 antibody BIW-8962 as an anti-MPM therapeutic using in vitro and in vivo assays. Consequently, the GM2 expression in the MPM cell lines was confirmed using flow cytometry. In addition, eight of 11 cell lines were GM2-positive (73%), although the GM2 expression was variable. BIW-8962 showed a significant antibody-dependent cellular cytotoxicity activity against the GM2-expressing MPM cell line MSTO-211H, the effect of which depended on the antibody concentration and effector/target ratio. In an in vivo orthotropic mouse model using MSTO-211H cells, BIW-8962 significantly decreased the incidence and size of tumors. Additionally, the GM2 expression was confirmed in the MPM clinical specimens. Fifty-eight percent of the MPM tumors were positive for GM2, with individual variation in the intensity and frequency of staining. These data suggest that anti-GM2 antibodies may become a therapeutic option for MPM patients. In this study, the anti-GM2 antibody BIW-8962 first showed a significant ADCC activity against malignant pleural mesothelioma (MPM) cell line and therapeutic activity in an in vivo orthotropic mouse model using the cell line. Additionally, the GM2 expression was confirmed in the MPM clinical specimens. These data suggest that anti-GM2 antibodies may become a therapeutic option for MPM patients. © 2014 The Authors. Cancer Science published by Wiley Publishing Asia Pty Ltd on behalf of Japanese Cancer Association.

Introduction: Folate receptor alpha (FOLR1) is a folate transporter expressed in many cancers, including ovarian cancer. Currently, several clinical trials of FOLR1-targeting drugs [conventional IgG1 antibodies, which exhibit antibody-dependent cellular cytotoxicity/complement dependent cytotoxicity (ADCC/CDC) activities, folic acid or antibody-drug conjugates and vaccines] have been conducted for ovarian and lung cancer. Therefore, FOLR1 is a remarkable target for cancer therapy under ongoing investigation. We established KHK2805, a novel anti-FOLR1 monoclonal antibody, using AccretaMab® technology to enhance both ADCC and CDC activities. Translational research (TR) using clinical samples is essential for determining whether a novel drug shows potent efficacy in clinical studies. In this study, we evaluated the anti-cancer activity of KHK2805 using malignant ascites and serum samples from patients with ovarian cancer. In addition, the FOLR1 expression was evaluated immunohistochemically using ovarian cancer tissues. Materials and Methods: An autologous ADCC assay was conducted using cells from the malignant ascites of ovarian cancer patients, in which both malignant cells (target cells) and immune cells (effector cells) were present. Similarly, the CDC activity was evaluated using supernatant of the malignant ascites obtained from the patients. Furthermore, a CDC assay using the serum of ovarian cancer patients was conducted. An immunohistochemical protocol was established using KM4193, the parental rat antibody of KHK2805, and formalin-fixed, paraffin-embedded ovarian cancer samples were immunohistochemically stained with KM4193. Results: KHK2805 showed potent ADCC activity against FOLR1-positive ovarian cancer cells in the autologous setting using the malignant ascites samples of the ovarian cancer patients, showing a clearly higher activity than that of the conventional anti-FOLR1 antibody. In addition, the CDC activity of KHK2805 was higher than that of the conventional anti-FOLR1 antibody under conditions using the supernatant of malignant ascites or serum from the ovarian cancer patients. Therefore, KHK2805 is thought to have markedly higher killing activity against tumor cells in patients with ovarian cancer. An immunohistochemical examination of the FOLR1 expression showed that the ovarian cancer tissues were positively stained with KM4193. Conclusions: TR using clinical samples from patients with ovarian cancer demonstrated that KHK2805 may be a promising novel anti-FOLR1 ovarian therapeutic agent with a potent antitumor activity. Citation Format: Kaito Nihira, Munetoshi Ando, Keiko Nagata, Maiko Adachi, Yui Suzuki, Yutaka Kanda, Takeshi Oshima, Ken-ichiro Nan-ya, Masanori Hiura, Toshihiko Ishii, Ryuichiro Nakai, Takeshi Takahashi. A novel anti-FOLR1 antibody developed with AccretaMab® technology, KHK2805, exhibits potent anti-cancer activity against ovarian cancer samples with the FOLR1 expression. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C124.