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
Authors: Ando Munetoshi , Nagata Keiko , Ando Hiroshi , Nakano Mariko , Kameyama Naoya , Kubota Tsuguo , Adachi Maiko , Suzuki Yui , Nakamura Kazuyasu , Ishii Toshihiko , Nakai Ryuichiro , Takahashi Takeshi 
Published: May 2016

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.