Alexander Lifke

Antibody mediated CDCP1 degradation as mode of action for cancer targeted therapy

CUB‐domain‐containing‐protein‐1 (CDCP1) is an integral membrane protein whose expression is up‐regulated in various cancer types. Although high CDCP1 expression has been correlated with poor prognosis in lung, breast, pancreas, and renal cancer, its functional role in tumor formation or progression is incompletely understood. So far it has remained unclear, whether CDCP1 is a useful target for antibody therapy of cancer and what could be a desired mode of action for a therapeutically useful antibody. To shed light on these questions, we have investigated the cellular effects of a therapeutic antibody candidate (RG7287). In focus formation assays, prolonged RG7287 treatment prevented the loss of contact inhibition caused by co‐transformation of NIH3T3 cells with CDCP1 and Src. In a xenograft study, MCF7 cells stably overexpressing CDCP1 reached the predefined tumor volume faster than the parental MCF7 cells lacking endogenous CDCP1. This tumor growth advantage was abolished by RG7287 treatment. In vitro, RG7287 induced rapid tyrosine phosphorylation of CDCP1 by Src, which was accompanied by translocation of CDCP1 to a Triton X‐100 insoluble fraction of the plasma membrane. Triggering these effects required bivalency of the antibody suggesting that it involves CDCP1 dimerization or clustering. However, this initial activation of CDCP1 was only transient and prolonged RG7287 treatment induced internalization and down‐regulation of CDCP1 in different cancer cell lines. Antibody stimulated CDCP1 degradation required Src activity and was proteasome dependent. Also in three different xenograft models with endogenous CDCP1 expression RG7287 treatment resulted in significant tumor growth inhibition concomitant with substantially reduced CDCP1 levels as judged by immunohistochemistry and Western blotting. Thus, despite transiently activating CDCP1 signaling, the RG7287 antibody has a therapeutically useful mode of action.

Abstract B67: Antibody-mediated delivery of viral peptides selectively activates CD8+ T cells to eliminate tumor cells in vitro and in vivo

Recent success of T cell based cancer immunotherapy approaches like chimeric antigen receptor T cells (CAR-Ts) and especially bispecific T cell engagers (BiTEs) has suggested great potential for cancer therapy. However, these technologies have several drawbacks like high risks for side-effects, such as autoimmunity, as well as inappropriate T cell activation due to a non-natural synapse. Hence, we sought to use antibody-mediated delivery of viral peptides to tumor cells in order to mimic viral infection and induce tumor cell lysis by virus-specific cytotoxic CD8+ T cells. Here, we generated immunoconjugates called antibody-targeted pathogen-derived peptides (ATPPs), where mature virus-derived MHC class I peptides from Influenza A or Epstein-Barr virus were conjugated to a tumor-associated antigen-specific antibody via a disulfide bond. Using optical imaging in combination with fluorescence resonance energy transfer, we revealed that after ATPP binding to the target antigen and subsequent internalization, the peptides are released in endosomes and loaded onto recycling MHC class I complexes. These peptide-MHC complexes are subsequently presented on the cell surface and mediate activation of human peptide-specific CD8+ T cells as shown by Interferon-γ release using enzyme-linked immunosorbent assay. Moreover, ATPP-loaded cancer cells from different tumor types were efficiently killed in vitro by human CD8+ T cells in a dose-dependent manner, reaching up to 100% killing after 24h at 0,13nM with an effector-to-target ratio of 3:1. Tumor cell death was assessed by the xCELLigence system as well as lactate dehydrogenase quantification in the supernatant. Interestingly, ATPPs were about 1000-times more potent than free peptide, while antibody alone, a non-cleavable ATPP construct, as well as peptides conjugated to a non-binding antibody exhibited no effects. Importantly, all used antibodies carried the P329G/LALA mutation for abolished Fc-receptor binding. In addition, we performed an experimental subcutaneous xenograft in vivo study with PDL1-expressing MDA-MB231 breast cancer cells in NOG mice in combination with anti-PD1 treatment. We observed that ATPPs successfully recruited adoptively transferred human peptide-specific CD8+ T cells into the tumor and induced 60% tumor growth inhibition of an established tumor after 3 weeks in the anti-PD1 combination setting. Altogether, we generated first in class immunoconjugates for antibody-targeted loading of cancer cells with foreign MHC-I restricted peptide antigens. Our results demonstrate potent ATPP-mediated antitumor efficacy in vitro and in vivo , by loading tumor cells with viral peptide antigens and redirecting virus-specific cytotoxic T cells against cancer. Citation Format: Julian Peter Sefrin, Lars Hillringhaus, Valeria Lifke, Alexander Lifke. Antibody-mediated delivery of viral peptides selectively activates CD8+ T cells to eliminate tumor cells in vitro and in vivo. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B67.

Abstract 2667: RG7287, a novel humanized anti-CDCP1 antibody with superior preclinical in vivo efficacy in combination with Paclitaxel

CUB domain-containing protein 1 (CDCP1) is a transmembrane glycoprotein and a substrate of Src family kinase (SFK). It has been shown to be upregulated and significantly contributing to a number of different cancers, including colon, lung, breast, kidney, and pancreas cancer. High expression of CDCP1 has been shown to correlate with poor prognosis. CDCP1 is involved in the regulation of anoikis resistance, cell migration and invasion. We have recently described RG7287, a humanized glycoengineered therapeutic anti-CDCP1 antibody with a dual mode of action. (1) downregulation of the receptor from the cell surface, and (2) engaging immune effector functions such as antibody-dependent cellular cytotoxicity (ADCC). Upon ligation of RG7287 to CDCP1 an initial phosphorylation of CDCP1 occurs, this transient activation results in the down-regulation of CDCP1. RG7287 prohibits the transformation potential of CDCP1 and Src in focus formation assays. In vivo, RG7287 increased the survival time of mice bearing tumors of MCF7 cells stably expressing CDCP1 compared to untreated CDCP1 overexpressing MCF7 tumors. Treatment of three different xenograft models with RG7287 inhibited tumor growth. In this study we looked at the possibility of eradicating the tumors by combining RG7287 with paclitaxel. Combining the cytostatic with RG7287 increases tumor growth inhibition compared to RG7287 alone in one xenograft model. In another model the combination of RG7287 with paclitaxel leads to tumor stasis. These results indicate a potential combination therapy for RG7287. We also tested whether RG7287 inhibits metastasis in vivo. Using a metastasis model we could show convincing inhibition of metastasis. Citation Format: Gwendlyn Kollmorgen, Alexander Lifke, Adam Nopora, Frieder Bauss, Gerhard Niederfellner, Birgit Bossenmaier. RG7287, a novel humanized anti-CDCP1 antibody with superior preclinical in vivo efficacy in combination with Paclitaxel. [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 2667. doi:10.1158/1538-7445.AM2014-2667