title: Design and synthesis of selective CDK8/19 dual inhibitors: Discovery of 4,5-dihydrothieno[3',4':3,4]benzo[1,2-d]isothiazole derivatives.
abstract: To develop a novel series of CDK8/19 dual inhibitors, we employed structure-based drug design using docking models based on a library compound, 4,5-dihydroimidazolo[3',4':3,4]benzo[1,2-d]isothiazole 16 bound to CDK8. We designed various [5,6,5]-fused tricyclic scaffolds bearing a carboxamide group to maintain predicted interactions with the backbone CO and NH of Ala100 in the CDK8 kinase hinge region. We found that 4,5-dihydrothieno[3',4':3,4]benzo[1,2-d]isothiazole derivative 29a showed particularly potent enzymatic inhibitory activity in both CDK8/19 (CDK8 IC50: 0.76nM, CDK19 IC50: 1.7nM). To improve the physicochemical properties and kinase selectivity of this compound, we introduced a substituted 3-pyridyloxy group into the scaffold 8-position. The resulting optimized compound 52h showed excellent in vitro potency (CDK8 IC50: 0.46nM, CDK19 IC50: 0.99nM), physicochemical properties, and kinase selectivity (only 5 kinases showed <35% unbound fraction at 300nM. CDK19: 4.6%, CDK8: 8.3%, HASPIN: 23%, DYRK1B: 27%, HIP1: 32%). Based on a docking model of 52h bound to CDK8, we could explain the highly specific kinase activity profile found for this compound, based on the interaction of the pyridyl group of 52h interacting with Met174 of the CDK8 DMG activation loop. In vitro pharmacological evaluation of 52h revealed potent suppression of phosphorylated STAT1 in various cancer cells. The high oral bioavailability found for this compound enabled in vivo studies, in which we demonstrated a mechanism-based in vivo PD effect as well as tumor growth suppression in an RPMI8226 human hematopoietic and lymphoid xenograft model in mouse [T/C: -1% (2.5mg/kg, qd)].
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan. Electronic address: kouji.ono@takeda.com.
authors.forename: Koji
authors.initials: K
authors.lastname: Ono
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Banno
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Okaniwa
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Hirayama
authors.affiliation: Takeda Union, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Iwamura
authors.affiliation: Product Information Group Japan Oncology Business Unit, Takeda Pharmaceutical Co., Ltd., 12-10, Nihonbashi 2-Chome, Chuo-ku, Tokyo 103-8686, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Hikichi
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Saomi
authors.initials: S
authors.lastname: Murai
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Hasegawa
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Yonemori
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Akito
authors.initials: A
authors.lastname: Hata
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Aoyama
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., Shonan Research Center, 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Cary
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D015195:Drug Design; D006801:Humans; D020128:Inhibitory Concentration 50; D051379:Mice; D008958:Models, Molecular; D047428:Protein Kinase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D013844:Thiazoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D047428:Protein Kinase Inhibitors; D013844:Thiazoles; D018844:Cyclin-Dependent Kinases
keywords: 4,5-Dihydrothieno[3′,4′:3,4]benzo[1,2-d]isothiazole; CDK19; CDK8; Cyclin-dependent kinases (CDKs); DMG; RPMI8226; STAT1; SW480; Transcriptional regulation