Background: Engagement of Tumor Necrosis Factor-α (TNF-α) with its receptor can lead to dramatically different cellular outcomes ranging from regulating cell survival and inflammation to induction of programmed forms of cell death. A critical proximal checkpoint determining the nature of TNF-α signaling is put in place by the cellular inhibitor of apoptosis proteins (cIAPs). In the context of cancer therapy these constitute an attractive target as they (1) block the TNF-α induced activation of apoptotic/necroptotic cues and (2) are negatively regulated by a highly selective endogenous ligand (i.e. SMAC), which served as a blueprint for the development of small molecule inhibitors of IAP (so called SMAC mimetics). Methods: Here we investigated the efficacy of SMAC mimetic BI891065 in enhancing targeted and chemotherapeutic approaches in preclinical mouse cancer models and describe immune-modulatory effects in syngeneic settings. To identify responding indications, a large pan-cancer cell line panel screening comprising 246 cell lines was performed (Eurofins). Proliferation of cells treated with increasing concentrations of BI 891065 combined with a fixed concentration of TNF-α was assessed by high-content screening. Furthermore, to gain a better understanding of the molecular determinants associated with sensitivity to SMAC mimetic treatment, genome-wide CRISPR/Cas9 drug modifier screens were performed. Results: Here we present key data demonstrating antitumor activity of BI891065 in preclinical models, our efforts towards understanding of genetic determinants of SMAC sensitivity and of potential responsive indications. By using genome-wide CRISPR/Cas9 drug modifier screens we not only demonstrated the feasibility of such unbiased approaches, as we identified many known (e.g. TNF Receptor 1, RIPK1, Caspase 8 and members of the NFκB signaling pathways) - but also potentially novel - regulators of TNF-α/SMAC mimetic induced cell death. In addition, to identify potential responsive indications to BI891065, extensive profiling of in vitro drug sensitivity across a large set of cancer cell types was performed. As a result of this, colorectal cancer (n=56) was identified as a promising indication: 5% of cell lines were found to be sensitive to BI 891065 single treatment. This could be further extended by the exogenous supply of TNF-α to BI 891065, increasing the number of sensitive cells to 21%. Conclusion: The presented data demonstrate the potential of BI 891065 to facilitate tumor cell death and to enhance anti-tumor immune responses, and nominate the compound as an attractive combination partner in cancer therapy. Our results led to the identification of potentially novel modulators of SMAC mimetic sensitivity via genome-wide CRISPR/Cas9 drug sensitizer screens and suggest colorectal cancer as a promising indication for clinical positioning. Citation Format: Martin Aichinger, Valeria Santoro, Ksenija Slavic-Obradovic, Stefanie Ruhland, Andreas Wernitznig, Andrea Neudolt, Markus Schaefer, Sabine Kallenda, Daniel Zach, Sabine Olt, Carina Salomon, Sarah Rieser, Martina Weissenboeck, Florian Ebner, Andreas Schlattl, Melanie Talata De Almeida, Rebecca Langlois, Martina Sykora, Markus Reschke, Thomas Zichner, Daniel Gerlach, Julian Jude, Michaela Fellner, Dirk Scharn, Norbert Kraut, Juergen Moll, Johannes Zuber, Sebastian Carotta, Maria Antonietta Impagnatiello, Ulrike Tontsch-Grunt. Targeting IAP in cancer: BI 891065 a potent small molecule SMAC mimetic that synergizes with immune checkpoint inhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6221.
SMAC mimetics (SMACm), drugs that mimic natural antagonists of Inhibitor of Apoptosis (IAP) are in clinical trials for hematological malignancies and solid cancers. The clinical benefit for patients in monotherapy was so far dismal. Hence, current clinical evaluation of SMACm focuses on combinations, in particular with checkpoint inhibitors and/or radiation therapy. The BET family protein BRD4 is a “reader” of epigenetic information and binds to acetylated chromatin to act as a key regulator of transcription. BET inhibitors (BETi) were tested in numerous clinical trials as novel treatment option for hematological and solid cancers. Like SMACm, monotherapy with BETi showed only moderate clinical activity stressing the importance of combination trials. BI 891065 a monovalent, oral SMACm, with a favorable safety profile allowing continuous dosing, is in Clinical Phase I (NCT03166631, NCT04138823). BI 894999 is a very potent and selective oral BETi, administered by intermittent dosing in Clinical Phase I (NCT02516553). We studied the combinatorial effect of both compounds in vitro across a large number of human tumor cell lines (lung, colorectal, pancreatic, and gastric cancer) in proliferation assays using Bliss synergy analysis and IncuCyte ZOOM® live cell imaging, and in vivo in three independent models. Of the 60+ cancer cell lines, around 30% showed synergy when treated with the BI 891065 + BI 894999 combination, irrespective of indication. Efficacy correlated with downmodulation of the key apoptosis regulator XIAP by BI 894999. In most of the cell lines tested, the synergistic effect was blocked by addition of the TNFα scavenger Enbrel and/or the apoptotic pathway inhibitor zVAD. In vivo efficacy was tested in two PDAC xenograft models (one immunocompetent and one immunodeficient) and one CRC model at clinically relevant doses. Daily oral application of both compounds was well tolerated and did not lead to drug-drug interactions. Target engagement markers were modulated as expected (cIAP1 degradation for SMACm and Hexim1 induction for BETi) and not compromised by the combination. Tumor growth inhibition in the BxPC3 pancreas model achieved 22% TGI for 50 mg/kg BI 891065, 70% TGI for 2 mg/kg BI 894999, and 96% TGI for the combination. In the Pan02 pancreas model 9% TGI for 50 mg/kg BI 891065, 30% TGI for 4 mg/kg BI 894999 and 92% TGI for the combination were recorded. Evaluation of the cellular composition of the tumor microenvironment in this immunocompetent model showed distinct changes evident of a reduced immuno-suppressive milieu upon combination treatment. Combination effects on tumor growth in the CRC model LoVo were far less pronounced. These preclinical in vitro and in vivo data are highlighting the potential of a SMACm/BETi combination for the treatment of solid cancers. The identification of patient selection markers for this combination will be necessary for advancing this concept into pivotal clinical trials. Citation Format: Paula-Elena Traexler, Dominik Arnold, Florian Ebner, Ksenija Slavic-Obradovic, Robin Jacob, Ha Pham Thi Thanh, Martin Aichinger, Anke Baum, Andreas Wernitznig, Daniel Gerlach, Maria-Antonietta Impagnatiello, Valeria Santoro, Sabine Olt, Dirk Scharn, Regina Ruzicka, Reniqua P. House, Mary Y. Murphy, Ulrich Reiser, Harald Engelhardt, Vittoria Zinzalla, Thorsten Laux, Flavio Solca, Ulrike Tontsch-Grunt. SMAC mimetic and BET inhibitor - a promising combination for solid cancer treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1951.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.