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// Arjan Kol 1 , Anton Terwisscha van Scheltinga 2 , Martin Pool 1 , Christian Gerdes 3 , Elisabeth de Vries 1 , Steven de Jong 1 1 Department of Medical Oncology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands 2 Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands 3 Roche Pharma Research & Early Development, Roche Innovation Center Zurich, Schlieren, Switzerland Correspondence to: Steven de Jong, email: s.de.jong@umcg.nl Keywords: non-small cell lung cancer, EGFR, imgatuzumab, cetuximab, antibodies Received: October 19, 2016 Accepted: March 30, 2017 Published: April 17, 2017 ABSTRACT Imgatuzumab is a novel glycoengineered anti-epidermal growth factor receptor (EGFR) monoclonal antibody optimized to induce both antibody-dependent cellular cytotoxicity (ADCC) and EGFR signal transduction inhibition. We investigated anti-EGFR monoclonal antibodies imgatuzumab and cetuximab–induced internalization and membranous turnover of EGFR, and whether this affected imgatuzumab–mediated ADCC responses and growth inhibition of non-small cell lung cancer (NSCLC) cells. In a panel of wild-type EGFR expressing human NSCLC cell lines, membranous and total EGFR levels were downregulated more effectively by imgatuzumab when compared with cetuximab. Imgatuzumab plus cetuximab enhanced EGFR internalization and reduced membranous turnover of EGFR, resulting in an even stronger downregulation of EGFR. Immunofluorescent analysis showed that combined treatment increased clustering of receptor-antibody complexes and directed internalized EGFR to lysosomes. The antibody combination potently inhibited intracellular signaling and epidermal growth factor (EGF)-dependent cell proliferation. More importantly, robust EGFR downregulation after 72 hours with the antibody combination did not impair ADCC responses. In conclusion, imgatuzumab plus cetuximab leads to a strong downregulation of EGFR and superior cell growth inhibition in vitro without affecting antibody-induced ADCC responses. These findings support further clinical exploration of the antibody combination in EGFR wild-type NSCLC.

// Simon-Peter Williams 1 , Annie Ogasawara 1 , Jeff N. Tinianow 1 , Judith E. Flores 1 , David Kan 1 , Jeffrey Lau 1 , MaryAnn Go 1 , Alexander N. Vanderbilt 1 , Herman S. Gill 1 , Li Miao 1 , Joshua Goldsmith 1 , Bonnee Rubinfeld 1 , Weiguang Mao 1 , Ron Firestein 1 , Shang-Fan Yu 1 , Jan Marik 1 , Anton G.T. Terwisscha van Scheltinga 1, 2 1 Genentech Research and Early Development, Genentech, Inc., South San Francisco, CA, 94080, USA 2 Department of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, 9700RB, The Netherlands Correspondence to : Simon-Peter Williams, e-mail: williams.simon@gene.com Keywords: antibody-drug conjugates, immunoPET, TENB2, STEAP1, zirconium-89 Received: December 10, 2015 Accepted: March 04, 2016 Published: March 26, 2016 ABSTRACT The efficacy of antibody-drug conjugates (ADCs) targeted to solid tumors depends on biological processes that are hard to monitor in vivo . 89 Zr-immunoPET of the ADC antibodies could help understand the performance of ADCs in the clinic by confirming the necessary penetration, binding, and internalization. This work studied monomethyl auristatin E (MMAE) ADCs against two targets in metastatic castration-resistant prostate cancer, TENB2 and STEAP1, in four patient-derived tumor models (LuCaP35V, LuCaP70, LuCaP77, LuCaP96.1). Three aspects of ADC biology were measured and compared: efficacy was measured in tumor growth inhibition studies; target expression was measured by immunohistochemistry and flow cytometry; and tumor antibody uptake was measured with 111 In-mAbs and gamma counting or with 89 Zr-immunoPET. Within each model, the mAb with the highest tumor uptake showed the greatest potency as an ADC. Sensitivity between models varied, with the LuCaP77 model showing weak efficacy despite high target expression and high antibody uptake. Ex vivo analysis confirmed the in vivo results, showing a correlation between expression, uptake and ADC efficacy. We conclude that 89 Zr-immunoPET data can demonstrate which ADC candidates achieve the penetration, binding, and internalization necessary for efficacy in tumors sensitive to the toxic payload.

Mesothelin is a tumor differentiation antigen expressed by epithelial tumors, including pancreatic cancer. Currently, mesothelin is being targeted with an antibodydrug conjugate (ADC) consisting of a mesothelin-specific antibody coupled to a highly potent chemotherapeutic drug. Considering the toxicity of the ADC and reduced accessibility of pancreatic tumors, non-invasive imaging could provide necessary information. We therefore developed a zirconium-89 (Zr-89) labeled anti-mesothelin antibody (Zr-89-AMA) to study its biodistribution in human pancreatic tumor bearing mice. Biodistribution and dose-finding of Zr-89-AMA were studied 144 h after tracer injection in mice with subcutaneously xenografted HPAC. MicroPET imaging was performed 24, 72 and 144 h after tracer injection in mice bearing HPAC or Capan-2. Tumor uptake and organ distribution of Zr-89-AMA were compared with nonspecific 111In-IgG. Biodistribution analyses revealed a dose-dependent Zr-89-AMA tumor uptake. Tumor uptake of Zr-89-AMA was higher than 111In-IgG using the lowest tracer dose. MicroPET showed increased tumor uptake over 6 days, whereas activity in blood pool and other tissues decreased. Immunohistochemistry showed that mesothelin was expressed by the HPAC and CAPAN-2 tumors and fluorescence microscopy revealed that AMA-800CW was present in tumor cell cytoplasm. Zr-89-AMA tumor uptake is antigen-specific in mesothelin-expressing tumors. Zr-89-AMA PET provides non-invasive, real-time information about AMA distribution and tumor targeting.