A New Series of Antileukemic Agents: Design, Synthesis, In Vitro and In Silico Evaluation of Thiazole-Based ABL1 Kinase Inhibitors

BACKGROUND

After the approval of imatinib, more than 25 antitumor agents targeting kinases have been approved, and several promising candidates are at various stages of clinical evaluation.

OBJECTIVES

Due to the importance of the thiazole scaffold in targeted anticancer drug discovery, the goal of this work is to identify new thiazolyl hydrazones as potent ABL1 kinase inhibitors for the management of Chronic Myeloid Leukemia (CML).

METHODS

New thiazolyl hydrazones (2a-p) were synthesized and investigated for their cytotoxic effects on the K562 CML cell line. Compounds 2h, 2j and 2l showed potent anticancer activity against K562 cell line. The cytotoxic effects of these compounds on other leukemia (HL-60, MT-2 and Jurkat) and HeLa human cervical carcinoma cell lines were also investigated. Furthermore, their cytotoxic effects on Mitogen-Activated Peripheral Blood Mononuclear Cells (MA-PBMCs) were evaluated to determine their selectivity. Due to its selective and potent anticancer activity, compound 2j was benchmarked for its apoptosis-inducing potential on K562 cell line and inhibitory effects on eight different Tyrosine Kinases (TKs), including ABL1 kinase. In order to investigate the binding mode of compound 2j into the ATP binding site of ABL1 kinase (PDB: 1IEP), a molecular docking study was conducted using MOE 2018.01 program. The QikProp module of Schrödinger's Molecular modelling package was used to predict the pharmacokinetic properties of compounds 2a-p.

RESULTS

4-(4-(Methylsulfonyl)phenyl)-2-[2-((1,3-benzodioxol-4-yl)methylene)hydrazinyl]thiazole (2j) showed antiproliferative activity against K562 cell line with an IC₅₀ value of 8.87±1.93 μM similar to imatinib (IC50= 6.84±1.11μM). Compound 2j was found to be more effective than imatinib on HL-60, Jurkat and MT-2 cells. Compound 2j also showed cytotoxic activity against HeLa cell line similar to imatinib. The higher selectivity index value of compound 2j than imatinib indicated that its antiproliferative activity was selective. Compound 2j also induced apoptosis in K562 cell line more than imatinib. Among eight TKs, compound 2j showed the strongest inhibitory activity against ABL1 kinase enzyme (IC₅₀= 5.37±1.17μM). According to molecular docking studies, compound 2j exhibited high affinity to the ATP binding site of ABL1 kinase, forming significant intermolecular interactions. On the basis of in silico studies, this compound did not violate Lipinski's rule of five and Jorgensen's rule of three.

CONCLUSION

Compound 2j stands out as a potential orally bioavailable ABL1 kinase inhibitor for the treatment of CML.

Anticancer activity of Turkish marine extracts: a purple sponge extract induces apoptosis with multitarget kinase inhibition activity

Marine natural products have drawn a great deal of attention as a vital source of new drugs for the last five decades. However, marine organisms in the seas surrounding Turkey (the Black Sea, the Aegean Sea and the Mediterranean Sea) haven't been yet extensively explored. In the present study, three marine organisms (Dysidea avara, Microcosmus sabatieri and Echinaster sepositus) were sampled from the Dardanelles (Turkish Straits System, Western Turkey) by scientific divers, transferred to the laboratory and then were extracted with 70% ethanol. The extracts were tested for their cytotoxic effect against K562, KMS-12PE, A549, and A375 cancer cell lines. The sponge extract elicited the most promising cytotoxic activity, thus it was further evaluated against H929, MCF-7, HeLa, and HCT116 cancer cells. Most of the designated cells showed a considerable sensitivity for the sponge extract particularly H929, K562, KMS-12PE and HeLa cells with IC₅₀ less than 10 μg/mL. On the contrary, the other two extracts exhibited no cytotoxic activity on all cells at 100 μg/mL concentration. The sponge extract was tested for its capacity to induce apoptosis in cancer cells and to inhibit a panel of tyrosine kinases showing remarkable results. The outcome of this study represents a platform for discovery of new chemotherapeutic agents of marine natural origin.

Design, Synthesis and Biological Evaluation of Pentacyclic Triterpene Derivatives: Optimization of Anti-ABL Kinase Activity

Imatinib, an Abelson (ABL) tyrosine kinase inhibitor, is a lead molecular-targeted drug against chronic myelogenous leukemia (CML). To overcome its resistance and adverse effects, new inhibitors of ABL kinase are needed. Our previous study showed that the benzyl ester of gypsogenin (1c), a pentacyclic triterpene, has anti-ABL kinase and a subsequent anti-CML activity. To optimize its activities, benzyl esters of carefully selected triterpenes (PT1-PT6), from different classes comprising oleanane, ursane and lupane, and new substituted benzyl esters of gypsogenin (GP1-GP5) were synthesized. All of the synthesized compounds were purified and charachterized by different spectroscopic methods. Cytotoxicity of the parent triterpenes and the synthesized compounds against CML cell line K562 was examined; revealing three promising compounds PT5, GP2 and GP5 (IC50 5.46, 4.78 and 3.19 μM, respectively). These compounds were shown to inhibit extracellular signal-regulated kinase (ERK) downstream signaling, and induce apoptosis in K562 cells. Among them, PT5 was identified to have in vitro activity (IC50 = 1.44 μM) against ABL1 kinase, about sixfold of 1c, which was justified by molecular docking. The in vitro activities of GP2 and GP5 are less than PT5, hence they were supposed to possess other more mechanisms of cytotoxicity. In general, our design and derivatizations resulted in enhancing the activity against ABL1 kinase and CML cells.