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
Authors: Nihira Kaito , Ando Munetoshi , Nagata Keiko , Adachi Maiko , Suzuki Yui , Kanda Yutaka , Oshima Takeshi , Nan-ya Ken-ichiro , Hiura Masanori , Ishii Toshihiko , Nakai Ryuichiro , Takahashi Takeshi 
Published: May 2016

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.