Unraveling the interaction mechanism of a benzothiadiazole-2.2-dioxide derivative with STAT3 : towards novel direct inhibitors

Unraveling the interaction mechanism of a benzothiadiazole-2,2- dioxide derivative with STAT3: towards novel direct inhibitors Matteo Mori 1, Ettore Gilardoni 1, Luca Regazzoni 1, Alessandro Pedretti 1, Diego Colombo 2, Gary Parkinson 3, Akira Asai 4, Giulia Cazzaniga 1, Fiorella Meneghetti 1, Stefania Villa 1 and Arianna Gelain 1 1 Department of Pharmaceutical Sciences, University of Milan, via L. Mangiagalli 25, 20133 Milan, Italy 2 Department of Medical Biotechnology and Translational Medicine, University of Milan, via C. Saldini 50, 20133 Milan, Italy 3 Department of Pharmaceutical and Biological Chemistry – UCL School of Pharmacy, University College London, 29/39 Brunswick Square, WC1N 1AX London, United Kingdom 4 Center for Drug Discovery – Graduate School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, 422-8526 Shizuoka, Japan Signal Transducer and Activator of Transcription 3 (STAT3) participates in oncogenesis by stimulating cell proliferation and preventing apoptosis; this protein has been validated as a suitable and selective target for anticancer therapy [1,2]. Starting from a virtual screening approach on STAT3-SH2 domain, we identified 5,6-dimethyl-1H,3H-2,1,3-benzothiadiazole-2,2-dioxide (I) as a potential inhibitor. Therefore, we synthesized and tested a series of derivatives (Figure 1), among which benzosulfamide I showed a significant activity (IC50 = 15.8 ± 0.6 μM by AlphaScreen-based assay) as a direct STAT3 inhibitor. Hence, an in-depth investigation through mass spectrometry, liquid chromatography and UV spectroscopy studies was carried out, shedding light on its intriguing mechanism of interaction, also involving cysteine residues located around the SH2 domain [3]. Figure 1. Benzothiadiazole derivatives of compound I. [1] T. Bowman,. M. A. Broome, D. Sinibaldi, W. Wharton, W. J. Pledger, J. M. Sedivy, R. Irby, T. Yeatman, S. A. Courtneidge, R. Jove, Proc. Natl. Acad. Sci. 2001, 98, 7319. [2] J. Turkson, D. Ryan, J. S Kim, Y. Zhang, Z. Chen, E. Haura, A. Laudano, S. Sebti, A. D. Hamilton, R. Jove, J. Biol. Chem. 2001, 276, 45443. [3] M. Mori, E. Gilardoni, L. Regazzoni, A. Pedretti, D. Colombo, G. Parkinson, A. Asai, F. Meneghetti, S. Villa, A. Gelain, Molecules 2020, 25(15), 3509.