Anna Wróbel

// Tomasz Rzymski 1, * , Michał Mikula 2, * , Eliza Żyłkiewicz 1 , Agnieszka Dreas 1 , Katarzyna Wiklik 1 , Aniela Gołas 1 , Katarzyna Wójcik 1 , Magdalena Masiejczyk 1 , Anna Wróbel 1 , Izabela Dolata 1 , Agata Kitlińska 1 , Małgorzata Statkiewicz 2 , Urszula Kuklinska 2 , Krzysztof Goryca 2 , Łukasz Sapała 1 , Aleksandra Grochowska 3 , Aleksandra Cabaj 2, 4 , Małgorzata Szajewska-Skuta 1 , Ewelina Gabor-Worwa 1 , Katarzyna Kucwaj 1 , Arkadiusz Białas 1 , Adam Radzimierski 1 , Michał Combik 1 , Jakub Woyciechowski 1 , Maciej Mikulski 1 , Renata Windak 1 , Jerzy Ostrowski 2, 3 and Krzysztof Brzózka 1 1 R&D Department, Selvita S.A., Kraków, Poland 2 Department of Genetics, Maria Sklodowska-Curie Memorial Cancer Center, Warsaw, Poland 3 Department of Gastroenterology, Hepatology and Clinical Oncology, Medical Center for Postgraduate Education, Warsaw, Poland 4 Laboratory of Bioinformatics, Nencki Institute of Experimental Biology, Warsaw, Poland * These authors have contributed equally to this work Correspondence to: Krzysztof Brzózka, email: krzysztof.brzozka@selvita.com Keywords: CDK8 mediator, kinase inhibitor, STAT5, AML, leukemia stem cells Received: August 04, 2016      Accepted: March 09, 2017      Published: April 04, 2017 ABSTRACT Inhibition of oncogenic transcriptional programs is a promising therapeutic strategy. A substituted tricyclic benzimidazole, SEL120-34A, is a novel inhibitor of Cyclin-dependent kinase 8 (CDK8), which regulates transcription by associating with the Mediator complex. X-ray crystallography has shown SEL120-34A to be a type I inhibitor forming halogen bonds with the protein’s hinge region and hydrophobic complementarities within its front pocket. SEL120-34A inhibits phosphorylation of STAT1 S727 and STAT5 S726 in cancer cells in vitro . Consistently, regulation of STATs- and NUP98-HOXA9- dependent transcription has been observed as a dominant mechanism of action in vivo . Treatment with the compound resulted in a differential efficacy on AML cells with elevated STAT5 S726 levels and stem cell characteristics. In contrast, resistant cells were negative for activated STAT5 and revealed lineage commitment. In vivo efficacy in xenotransplanted AML models correlated with significant repression of STAT5 S726. Favorable pharmacokinetics, confirmed safety and in vivo efficacy provide a rationale for the further clinical development of SEL120-34A as a personalized therapeutic approach in AML.

The potency of flavonoids (isoflavones, flavones, and flavanones) to inhibit efflux of 2',7'-bis-(carboxypropyl)-5(6)-carboxyfluorescein (BCPCF) from human erythrocytes was investigated. Structure-activity relationship analysis showed that the strongest inhibitors were found among flavanones bearing a hydrophobic prenyl, geranyl, or lavandulyl group at position 8 (and hydroxyl groups at 5 and 7) in ring A. A prenyl group at position 5' or stilbene at positions 4'-5' in ring B further seemed to increase inhibitor potency. The most efficient flavanones, euchrestaflavanone A and sophoraflavanone H, were approximately 20 times more efficient than genistein, and induced 50% inhibition of BCPCF efflux (IC50) at 3 microM (60 min, 37 degrees C). This is comparable to IC50 of benzbromarone (4 microM) and lower than IC50 of indomethacin (10 microM), both known MRP1 (ABCC1) inhibitors. It is suggested that BCPCF efflux is mainly due to MRP1 activity. Our results indicate that flavonoid molecular structure provides a promising base for development of potent MRP1 inhibitors.