Abstract 2648: Enhanced antitumor effect of anti tissue factor (TF) antibody-conjugated epirubicin-incorporating polymeric micelles in human cancer xenografts with high TF expression

Abstract

Abstract Background: Anticancer agent-incorporating polymeric micelles, categorized as passive targeting agents, are expected to accumulate in tumors based on the enhanced permeability and retention effect. Recently, we made epirubicin-incorporating micelles containing acid-sensitive bonds (NC-6300), and reported the enhanced antitumor activity and reduced cardiotoxicity in preclinical studies; a Phase I study of NC-6300 is also under way in Japan. In order to further enhance the accumulation of NC-6300 in tumors using the active targeting strategy, we tried to attach a tumor-specific monoclonal antibody (mAb) to the terminal of polyethylene glycol comprising NC-6300. As the targeting molecule, we selected transmembrane receptor tissue factor (TF), namely, the primary initiator of coagulation. TF, which is known to play an important role in not only blood coagulation, but also in tumor growth and metastasis, is frequently overexpressed in various types of tumor. We have established a mAb against human TF, and succeeded in developing anti TF mAb-conjugated NC-6300 (anti TF-NC-6300). Here, we report the results of in vitro and in vivo studies of this immunoconjugate. Methods: Anti TF-NC-6300 was prepared based on our Antibody/Drug-Conjugated Micelle (ADCM) technology (Japan Patent No.4538666) with slight modification. In the in vitro assay, real-time cell analysis was performed using the xCELLigence system to determine the effects of anti TF-NC-6300 and NC-6300 on pancreatic tumor cell proliferation. Next, image analysis and quantification of the intracellular epirubicin concentration were performed using Array Scan VTI. For evaluating the in vivo antitumor effects, anti TF-NC-6300 (10 mg/kg), NC-6300 (10 mg/kg) and epirubicin (10 mg/kg) were administered intravenously once a week for 3 weeks to mice bearing human pancreatic cancer xenografts or human gastric cancer xenografts with high TF expression (BxPC3 or 44As3). Results: In the real-time cell proliferation assay, anti TF-NC-6300 exerted a greater degree of inhibition of cell growth than NC-6300 in BxPC3. On the other hand, there was no difference in effect between these two drugs in SUIT2, a human pancreatic cancer with low TF expression. In the imaging cytometric analysis, anti TF-NC-6300 was internalized sooner than NC-6300, resulting in higher accumulation of epirubicin in the cytoplasm and nuclei of the BxPC3 cells. On the other hand, no such difference was observed in the case of SUIT2. In the in vivo antitumor assay, as compared to both epirubicin and NC-6300, anti TF-NC-6300 showed significant antitumor activity in xenograft models of BxPC3 and 44As3. Conclusion: These data warrant a clinical evaluation of anti TF mAb-conjugated epirubicin-incorporating polymeric micelles in patients with TF-positive cancer subtypes. Citation Format: Yoshiyuki Yamamoto, Ichinosuke Hyodo, Yoshikatsu Koga, Ryo Tsumura, Ryuta Sato, Toshihumi Obonai, Hirobumi Fuchigami, Masahisa Kudo, Masahiro Yasunaga, Mitsunori Harada, Tatsuyuki Hayashi, Yasuki Kato, Yasuhiro Matsumura. Enhanced antitumor effect of anti tissue factor (TF) antibody-conjugated epirubicin-incorporating polymeric micelles in human cancer xenografts with high TF expression. [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 2648. doi:10.1158/1538-7445.AM2014-2648