Abstract 1669: Preclinical efficacy of Sym004, novel anti-EGFR antibody, in esophageal squamous cell carcinoma cell lines
Authors: Fukuoka Shota , Kojima Takashi , Koga Yoshikatsu , Yamauchi Mayumi , Komatsuzaki Rie , Aoyagi Kazuhiko , Sasaki Hiroki , Yasunaga Masahiro , Matsumura Yasuhiro , Kuronita Toshio , Doi Toshihiko , Ohtsu Atsushi 
Published: August 2015

Background: Epidermal growth factor receptor (EGFR) is a well-validated oncology target molecule for monoclonal antibody therapies. Sym004 is a novel anti-EGFR antibody mixture that consists of two recombinant IgG1 antibodies against domain III of the EGFR. The primary mechanism of action of Sym004 is thought to be EGFR cross-linking, internalization and degradation of the EGFR from the cell surface. EGFR is highly expressed in the overwhelming majority of esophageal squamous cell carcinoma (ESCC). We, therefore, investigated the effect of Sym004 in human ESCC cell lines in the present study.

Method: In this preclinical study, approximately 50 ESCC cell lines and 3 kinds of anti-EGFR antibodies (Sym004, cetuximab, and panitumumab) were used. According to protein expression status and gene mutation status analyzed by Western blotting and next generation sequencing, these ESCC cell lines were classified into several groups. High EGFR-expressing cell lines were used for further investigations. Internalization of anti-EGFR antibodies into ESCC cells and inhibition of the EGFR signaling cascade by anti-EGFR antibodies were studied in in vitro experiments. Growth inhibitions by anti-EGFR antibody treatment were investigated in in vitro and in vivo experiments. The present preclinical studies were conducted at the National Cancer Center East Japan as collaborative studies with Merck Serono.

Result: Even though protein expression of EGFR was detected in all ESCC cell lines, a variety of the expression levels were seen among the cell lines consistent with the previous data of clinical specimens. In addition, following gene alterations were found: EGFR amplification, Ras mutation, and PIK3CA mutation, and their frequency was 17% (8/48), 6.3% (3/48) and 8.3% (4/48), respectively. More effective internalization of Sym004 was observed than cetuximab and panitumumab in the high EGFR-expression cell lines. In a growth inhibition assay, more potent anti-proliferative activity of Sym004 was observed than those of other anti-EGFR antibodies in some cell lines. No obvious correlation between EGFR expression and the anti-proliferative activity was observed, although cell lines with higher EGFR expression showed a trend toward higher sensitivity to Sym004. In vivo xenograft studies of Sym004 using human ESCC cell lines are currently underway and will be presented in the annual meeting.

Conclusions: These studies showed that Sym004 exhibited antitumor activity in some ESCC cell lines in preclinical settings, and are expected to provide a scientific rationale along with a possible clinical indication of ESCC in clinical setting.

Citation Format: Shota Fukuoka, Takashi Kojima, Yoshikatsu Koga, Mayumi Yamauchi, Rie Komatsuzaki, Kazuhiko Aoyagi, Hiroki Sasaki, Masahiro Yasunaga, Yasuhiro　 Matsumura, Toshio Kuronita, Toshihiko Doi, Atsushi Ohtsu. Preclinical efficacy of Sym004, novel anti-EGFR antibody, in esophageal squamous cell carcinoma cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1669. doi:10.1158/1538-7445.AM2015-1669