Toshihiko Ishii

Potent Therapeutic Activity Against Peritoneal Dissemination and Malignant Ascites by the Novel Anti-Folate Receptor Alpha Antibody KHK2805

Many ovarian cancer patients often show peritoneal metastasis with malignant ascites. However, unmet medical needs remain regarding controlling these symptoms after tumors become resistant to chemotherapies. We developed KHK2805, a novel anti-folate receptor α (FOLR1) humanized antibody with enhanced antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). The primary aim of the present study was to evaluate whether the anti-tumor activity of KHK2805 was sufficient for therapeutic application against peritoneal dissemination and malignant ascites of platinum-resistant ovarian cancer in preclinical models. Here, both the ADCC and CDC of KHK2805 were evaluated in ovarian cancer cell lines and patient-derived samples. The anti-tumor activity of KHK2805 was evaluated in a SCID mouse model of platinum-resistant peritoneal dissemination. As results, KHK2805 showed specific binding to FOLR1 with high affinity at a novel epitope. KHK2805 exerted potent ADCC and CDC against ovarian cancer cell lines. Furthermore, primary platinum-resistant malignant ascites cells were susceptible to autologous ADCC with KHK2805. Patient-derived sera and malignant ascites induced CDC of KHK2805. KHK2805 significantly reduced the total tumor burden and amount of ascites in SCID mice with peritoneal dissemination and significantly prolonged their survival. In addition, the parental rat antibody strongly stained serous and clear cell-type ovarian tumors by immunohistochemistry. Overall, KHK2805 showed cytotoxicity against both ovarian cancer cell lines and patient-derived cells. These translational study findings suggest that KHK2805 may be promising as a novel therapeutic agent for platinum-resistant ovarian cancer with peritoneal dissemination and malignant ascites.

Abstract 2358: KHK2805, a novel ADCC- and CDC-enhanced anti-FOLR1 antibody with AccretaMab® technology, shows a potent anti-tumor activity in combination with pemetrexed

Introduction: Folate receptor 1 (FOLR1, FR alpha) is a folate transporter which is expressed in many cancers including ovarian cancer (OvC) and non-small cell lung cancer (NSCLC), and which is an attractive target for cancer therapy, is currently the subject of ongoing studies. We established KHK2805, a novel anti-FOLR1 monoclonal antibody with AccretaMab® technology to enhance both the antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) activities. It was demonstrated that KHK2805 exhibits markedly high ADCC and CDC activity levels in clinical samples from ovarian cancer patients, while a tolerable safety profile has been observed in preclinical models using cynomolgus monkeys (100 mg/kg weekly for 4 weeks, intravenously). A greater understanding of the biology of FOLR1 is important for providing a novel therapeutic option for KHK2805 for patients with cancer. Pemetrexed (PEM), a second-generation anti-folate which inhibits thymidylate synthase, glycinamide ribonucleotide transformylase and dihydrofolate reductase, is used as a standard therapy for patients with cancers such as NSCLC. It is not fully understood how PEM treatment affects the expression of FOLR1 on cancer cells. We therefore examined the level of FOLR1 expression in cancer cells after PEM treatment, and the anti-tumor activity of KHK2805 in combination with PEM. Materials and Methods: The FOLR1 expression levels after PEM treatment were examined in OvC, NSCLC, and endometrial cancer cells by flow cytometry. The ADCC activity of KHK2805 against PEM-treated cells was evaluated. The anti-tumor activity of KHK2805 in combination with PEM was investigated in SCID mice. Results: Flow cytometry showed that PEM treatment increased the FOLR1 expression of various cancers such as OvC (IGROV1, SKOV3, MCAS), NSCLC (NCI-H1437, NCI-H2228), and endometrial cancer (MESSA, HEC1A, HEC1B) cells. In addition, PEM treatment enhanced the ADCC activity of KHK2805 against MCAS, NCI-H1437, and NCI-H2228, in comparison to cells that did not receive PEM treatment. Furthermore, the anti-tumor activity of KHK2805 in SCID mice bearing subcutaneous MCAS tumors was enhanced by PEM treatment. Conclusions: PEM induced further FOLR1 expression in OvC, NSCLC, and endometrial cancer, resulting in the enhancement of the ADCC activity of KHK2805. The use of KHK2805 with PEM might therefore be a potent therapeutic option. Citation Format: Munetoshi Ando, Keiko Nagata, Toshihiko Ishii, Ryuichiro Nakai, Takeshi Takahashi. KHK2805, a novel ADCC- and CDC-enhanced anti-FOLR1 antibody with AccretaMab® technology, shows a potent anti-tumor activity in combination with pemetrexed. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2358.

Abstract C123: A novel anti-FOLR1 antibody developed with AccretaMab® technology, KHK2805, exhibits markedly high ADCC/CDC activity and a tolerable safety profile in preclinical models

Introduction: Folate receptor alpha (FOLR1) is a member of the folate transporter family expressed on normal tissues and overexpressed in multiple types of tumors, such as ovarian cancer, uterine cancer, non-small cell lung cancer, gastric cancer, breast cancer and kidney 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. AccretaMab® technology involves combining both the POTELLIGENT®, a clinically validated ADCC-enhanced technology, and COMPLEGENT®, a new CDC-enhanced technology, systems to result in a superior technology for enhancing the killing activity of antibodies. KHK2805 is a novel humanized and CDR-altered anti-FOLR1 antibody developed with AccretaMab® technology. In this study, we evaluated the anti-cancer activity of KHK2805 in preclinical ovarian cancer models, both in vitro and in vivo, and confirmed the safety profile of KHK2805 in cynomolgus monkeys, since KHK2805 cross-reacts to cynomolgus monkey FOLR1. Materials and Methods: The binding kinetics of KHK2805 against recombinant FOLR1 (rFOLR1) were measured using the Biacore system. The epitope was determined with an ELISA against rFOLR1s. The in vitro ADCC and CDC activities against FOLR1-positive ovarian cancer cells were evaluated using PBMCs and serum from healthy volunteers. The in vivo anti-tumor activity of KHK2805 was examined using a SCID mouse model. The safety profile of KHK2805 was evaluated in cynomolgus monkeys. Results: KHK2805 induced potent ADCC and CDC activities against FOLR1-positive ovarian cancer cells. The ADCC activity of KHK2805 was significantly higher than that of the conventional anti-FOLR1 antibody. Furthermore, KHK2805 showed a potent ADCC activity against ovarian cancer cells with a low FOLR1 expression or low folic acid-uptake activity, which may be difficult to target with current FOLR1-targeting drugs. The results also showed that the markedly higher ADCC activity of KHK2805 was caused by its super-high affinity, unique epitope and use of AccretaMab® technology. In addition, the CDC activity of KHK2805 was also clearly higher than that of the conventional anti-FOLR1 antibody. This indicates that the higher CDC activity of KHK2805 is due to the application of protein engineering of CDR alterations and AccretaMab® technology. Moreover, the potent anti-tumor activity of KHK2805 was observed in a peritoneal dissemination model in SCID mice. Finally, we completed preliminary safety experiments with KHK2805. A repeated-dose toxicity study of KHK2805 (weekly 100 mg/kg for 4 weeks, intravenously) showed an acceptable tolerability profile in cynomolgus monkeys. Conclusions: KHK2805 may be a promising novel anti-FOLR1 therapeutic agent with a potent anti-tumor activity and tolerable safety profile for patients with the FOLR1 expression. Citation Format: Munetoshi Ando, Keiko Nagata, Hiroshi Ando, Mariko Nakano, Naoya Kameyama, Tsuguo Kubota, Maiko Adachi, Yui Suzuki, Kazuyasu Nakamura, Toshihiko Ishii, Ryuichiro Nakai, Takeshi Takahashi. A novel anti-FOLR1 antibody developed with AccretaMab® technology, KHK2805, exhibits markedly high ADCC/CDC activity and a tolerable safety profile in preclinical models. [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 C123.

Abstract C124: A novel anti-FOLR1 antibody developed with AccretaMab® technology, KHK2805, exhibits potent anti-cancer activity against ovarian cancer samples with the FOLR1 expression

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.