Citation: Stukan, I.; Gryzik, M.; Hoser, G.; Want, A.; Grabowska-Pyrzewicz, W.; Zdioruk, M.; Napiórkowska, M.; Cie´ slak, M.; Królewska-Goli ´ nska, K.; Nawrot, B.; et al. Novel Dicarboximide BK124.1 Breaks Multidrug Resistance and Shows Anticancer Efficacy in Chronic Myeloid Leukemia Preclinical Models and Patients’ CD34 + /CD38 − Leukemia Stem Cells. Cancers 2022, 14, 3641. https://doi.org/10.3390/ cancers14153641 Academic Editor: Zhixiang Wang Received: 10 June 2022 Accepted: 23 July 2022 Published: 27 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). cancers Article Novel Dicarboximide BK124.1 Breaks Multidrug Resistance and Shows Anticancer Efficacy in Chronic Myeloid Leukemia Preclinical Models and Patients’ CD34 + /CD38 - Leukemia Stem Cells Iga Stukan 1,† , Marek Gryzik 1 , Gra ˙ zyna Hoser 1,2 , Andrew Want 1 , Wioleta Grabowska-Pyrzewicz 1 , Mikolaj Zdioruk 1 , Mariola Napiórkowska 3 , Marcin Cie´ slak 4 , Karolina Królewska-Goli ´ nska 4 , Barbara Nawrot 4 , Grzegorz Basak 5 and Urszula Wojda 1, * 1 Laboratory of Preclinical Testing of Higher Standard, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland; iga.stukan@pum.edu.pl (I.S.); m.gryzik@nencki.edu.pl (M.G.); grazyna.hoser@cmkp.edu.pl (G.H.); a.want@nencki.edu.pl (A.W.); w.grabowska@nencki.edu.pl (W.G.-P.); myko.zdioruk@gmail.com (M.Z.) 2 Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland 3 Departmentof Biochemistry, Medical University of Warsaw, 02-097 Warsaw, Poland; mariola.napiorkowska@wum.edu.pl 4 Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, 90-363 Lodz, Poland; marcin@cbmm.lodz.pl (M.C.); kkrolews@cbmm.lodz.pl (K.K.-G.); bnawrot@cbmm.lodz.pl (B.N.) 5 Department of Hematology, Transplantation and Internal Medicine, Medical University of Warsaw, 02-097 Warsaw, Poland; grzegorz.basak@wum.edu.pl * Correspondence: u.wojda@nencki.edu.pl; Tel.: +48-22-5892-578 † Current address: Department of General Pathology, Pomeranian Medical University and Independent Pharmacokinetics and Clinical Pharmacy Laboratory, Pomeranian Medical University, 70-111 Szczecin, Poland. Simple Summary: Chemotherapy is a first line treatment in many cancer types, but the constant exposition to chemotherapeutics often leads to therapy resistance. An example is chronic myeloid leukemia that, due to the use of tyrosine kinase inhibitors such as imatinib, remains manageable, however incurable. Overall, 20–25% of imatinib responders develop secondary resistance, and among them, 20–40% is due to mechanisms such as expression of P-glycoprotein (MDR1) or leukemia stem cells’ mechanisms of survival and cancer regrowth. This study provides the first evidence from animal and cellular models that this resistance can be overcome with the novel dicarboximide BK124.1. The compound causes no visible toxicity in mice, and has proper pharmacokinetics for therapeutic applications. It was efficient against both multidrug resistant CML blasts and CD34 + /CD38 − leukemia stem cells coming from CML patients. Future development of BK124.1 could offer curative treatment of CML and of other cancers resistant or intolerant to current chemotherapy. Abstract: The search is ongoing for new anticancer therapeutics that would overcome resistance to chemotherapy. This includes chronic myeloid leukemia, particularly suitable for the studies of novel anticancer compounds due to its homogenous and well-known genetic background. Here we show anticancer efficacy of novel dicarboximide denoted BK124.1 (C 31 H 37 ClN 2 O 4 ) in a mouse CML xenograft model and in vitro in two types of chemoresistant CML cells: MDR1 blasts and in CD34 + patients’ stem cells (N = 8) using immunoblotting and flow cytometry. Intraperitoneal administration of BK124.1 showed anti-CML efficacy in the xenograft mouse model (N = 6) comparable to the commonly used imatinib and hydroxyurea. In K562 blasts, BK124.1 decreased the protein levels of BCR-ABL1 kinase and its downstream effectors, resulting in G2/M cell cycle arrest and apoptosis associated with FOXO3a/p21 waf1/cip1 upregulation in the nucleus. Additionally, BK124.1 evoked massive apoptosis in multidrug resistant K562-MDR1 cells (IC 50 = 2.16 μM), in CD34 + cells from CML patients (IC 50 = 1.5 μM), and in the CD34 + /CD38 − subpopulation consisting of rare, drug- resistant cancer initiating stem cells. Given the advantages of BK124.1 as a potential chemotherapeutic and its unique ability to overcome BCR-ABL1 dependent and independent multidrug resistance Cancers 2022, 14, 3641. https://doi.org/10.3390/cancers14153641 https://www.mdpi.com/journal/cancers