Abstract 2642: Antibody-drug conjugate for human pancreatic cancer cells using anti-tissue factor monoclonal antibody
Authors: Koga Yoshikatsu , Sato Ryuta , Tsumura Ryo , Machida Hikaru , Yamamoto Yoshiyuki , Hisada Yohei , Fujiwara Yuki , Yasunaga Masahiro , Manabe Shino , Matsumura Yasuhiro 
Published: May 2015

Abstract
Background: The incidence of venous thromboembolism in patients with cancer is reported to be twofold higher than that in patients without cancer. One of the well-characterized procoagulants associated with cancer is tissue factor (TF). TF is expressed not only on the surfaces of the cancer cells, but also in the monocytes and endothelial cells which are stimulated under the cancerous condition. Thus, TF is an appropriate molecule for drug delivery to both cancer cells and cancer stroma. In the present study, the antitumor effect of an antibody drug conjugate (ADC), anti-TF monoclonal antibody (mAb) conjugated with monomethyl auristatin E (MMAE), was investigated.
Methods: MMAE was conjugated to anti-human TF (hTF) and -mouse TF (mTF) antibody using a valine-citrulline dipeptide linker. The stability of ADC under the physiological and intracellular conditions were analyzed by HPLC. The bio-distributions of hTF and mTF mAbs were analyzed in vivo. The cytotoxic effects of the ADC in four pancreatic cancer cell lines were analyzed both in vitro and in vivo.
Results: The four pancreatic cancer cell lines used in this study were classified into 3 groups; high-TF-expressing cells (BxPC-3), moderate-TF-expressing cells (PSN-1), and low-TF-expressing cells (Capan-1 and Panc-1). Anti-hTF mAb was sufficiently internalized in the cytoplasm of BxPC-3 after 3-h incubation. The ADC was stable under the extracellular condition, and sufficient free MMAE was released into the cytoplasm. hTF mAb permeating from the tumor vessels was distributed at the periphery of the tumors. On the other hand, mTF mAb was distributed in the cancer stroma. The IC50 of MMAE for these pancreatic cancer cell lines was approximately 1 nM, while the IC50 of the MMAE contained in hTF-MMAE for BxPC-3 was 1.15 nM; on the other hand the values for Capan-1 and Panc-1 exceeded 100 nM. BxPC-3 subcutaneous tumor growth was significantly suppressed in the 20 mg/kg hTF-MMAE group as compared with that in the saline group (P &lt; 0.001). Tumor growth in the 20 mg/kg mTF-MMAE group was also significantly suppressed as compared with that in the saline group (P = 0.001). The Ki67-positive cell rate in the hTF-MMAE treatment group was significantly lower than that in the saline (P = 0.001) and mTF-MMAE treatment groups (P = 0.015).
Conclusions: ADC measuring 10 nm in size could reach cancer cells through the cancer stroma and could be effectively internalized into cancer cells. Meanwhile, cancer-stroma-targeting mAb (mTF mAb) elicit a partial response as compared to hTF mAb. Our anti-TF mAb conjugated with MMAE warrants clinical evaluation.
Citation Format: Yoshikatsu Koga, Ryuta Sato, Ryo Tsumura, Hikaru Machida, Yoshiyuki Yamamoto, Yohei Hisada, Yuki Fujiwara, Masahiro Yasunaga, Shino Manabe, Yasuhiro Matsumura. Antibody-drug conjugate for human pancreatic cancer cells using anti-tissue factor monoclonal antibody. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2642. doi:10.1158/1538-7445.AM2014-2642