Julie A. Tucker

Cyclin-Dependent Kinase 4 Inhibitors as a Treatment for Cancer. Part 1: Identification and Optimisation of Substituted 4,6-Bis Anilino Pyrimidines

Using a high-throughput screening campaign, we identified the 4,6-bis anilino pyrimidines as inhibitors of the cyclin-dependent kinase, CDK4. Herein we describe the further chemical modification and use of X-ray crystallography to develop potent and selective in vitro inhibitors of CDK4.

The Discovery of Azd5597, a Potent Imidazole Pyrimidine Amide Cdk Inhibitor Suitable for Intravenous Dosing.

The development of a novel series of imidazole pyrimidine amides as cyclin-dependent kinase (CDK) inhibitors is described. Optimisation of inhibitory potency against multiple CDKs (1, 2 and 9) resulted in imidazole pyrimidine amides with potent in vitro anti-proliferative effects against a range of cancer cell lines. Excellent physiochemical properties and large margins against inhibition of CYP isoforms and the hERG ion channel were achieved by modification of lipophilicity and amine basicity. A candidate with disease model activity in human cancer cell line xenografts and with suitable physiochemical and pharmacokinetic profiles for intravenous (i.v.) dosing was selected for further development as AZD5597.

Discovery of azabenzimidazole derivatives as potent, selective inhibitors of TBK1/IKKε kinases.

The design, synthesis and biological evaluation of a series of azabenzimidazole derivatives as TBK1/IKKε kinase inhibitors are described. Starting from a lead compound 1a, iterative design and SAR exploitation of the scaffold led to analogues with nM enzyme potencies against TBK1/IKKε. These compounds also exhibited excellent cellular activity against TBK1. Further structure-based design to improve selectivity over CDK2 and Aurora B resulted in compounds such as 5b-e. These probe compounds will facilitate study of the complex cancer biology of TBK1 and IKKε.

Structures of the Human Poly (Adp-Ribose) Glycohydrolase Catalytic Domain Confirm Catalytic Mechanism and Explain Inhibition by Adp-Hpd Derivatives.

Poly(ADP-ribose) glycohydrolase (PARG) is the only enzyme known to catalyse hydrolysis of the O-glycosidic linkages of ADP-ribose polymers, thereby reversing the effects of poly(ADP-ribose) polymerases. PARG deficiency leads to cell death whilst PARG depletion causes sensitisation to certain DNA damaging agents, implicating PARG as a potential therapeutic target in several disease areas. Efforts to develop small molecule inhibitors of PARG activity have until recently been hampered by a lack of structural information on PARG. We have used a combination of bio-informatic and experimental approaches to engineer a crystallisable, catalytically active fragment of human PARG (hPARG). Here, we present high-resolution structures of the catalytic domain of hPARG in unliganded form and in complex with three inhibitors: ADP-ribose (ADPR), adenosine 5′-diphosphate (hydroxymethyl)pyrrolidinediol (ADP-HPD) and 8-n-octyl-amino-ADP-HPD. Our structures confirm conservation of overall fold amongst mammalian PARG glycohydrolase domains, whilst revealing additional flexible regions in the catalytic site. These new structures rationalise a body of published mutational data and the reported structure-activity relationship for ADP-HPD based PARG inhibitors. In addition, we have developed and used biochemical, isothermal titration calorimetry and surface plasmon resonance assays to characterise the binding of inhibitors to our PARG protein, thus providing a starting point for the design of new inhibitors.

Imidazoles: Sar and Development of a Potent Class of Cyclin-Dependent Kinase Inhibitors.

An imidazole series of cyclin-dependent kinase (CDK) inhibitors has been developed. Protein inhibitor structure determination has provided an understanding of the emerging structure activity trends for the imidazole series. The introduction of a methyl sulfone at the aniline terminus led to a more orally bioavailable CDK inhibitor that was progressed into clinical development.

Structural Insights into FGFR Kinase Isoform Selectivity: Diverse Binding Modes of AZD4547 and Ponatinib in Complex with FGFR1 and FGFR4

The fibroblast growth factor receptor (FGFR) family of receptor tyrosine kinases has been implicated in a wide variety of cancers. Despite a high level of sequence homology in the ATP-binding site, the majority of reported inhibitors are selective for the FGFR1-3 isoforms and display much reduced potency toward FGFR4, an exception being the Bcr-Abl inhibitor ponatinib. Here we present the crystal structure of the FGFR4 kinase domain and show that both FGFR1 and FGFR4 kinase domains in complex with ponatinib adopt a DFG-out activation loop conformation. Comparison with the structure of FGFR1 in complex with the candidate drug AZD4547, combined with kinetic characterization of the binding of ponatinib and AZD4547 to FGFR1 and FGFR4, sheds light on the observed differences in selectivity profiles and provides a rationale for developing FGFR4-selective inhibitors.

Novel thienopyrimidine and thiazolopyrimidine kinase inhibitors with activity against Tie-2 in vitro and in vivo.

The SAR and improvement in potency against Tie2 of novel thienopyrimidine and thiazolopyrimidine kinase inhibitors are reported. The crystal structure of one of these compounds bound to the Tie-2 kinase domain is consistent with the SAR. These compounds have moderate potency in cellular assays of Tie-2 inhibition, good physical properties, DMPK, and show evidence of in vivo inhibition of Tie-2.

Imidazole Piperazines: Sar and Development of a Potent Class of Cyclin-Dependent Kinase Inhibitors with a Novel Binding Mode.

A piperazine series of cyclin-dependent kinase (CDK) inhibitors have been identified. The compounds exhibit excellent physiochemical properties and a novel binding mode, whereby a bridging interaction via a water molecule with Asp 86 of CDK2, leads to selectivity for the CDK family of enzymes over other kinases. Piperazines 2e and 2i were subsequently shown to inhibit tumour growth when dosed orally in a nude mouse xenograft study. Additional chemical series that exploit this unexpected interaction with Asp 86 are also described.

Discovery of a novel allosteric inhibitor-binding site in ERK5: comparison with the canonical kinase hinge ATP-binding site.

Crystal structures of the MAP kinase ERK5 in complex with XMD8-92 and four novel inhibitors reveal an allosteric binding site between the kinase P-loop and αC helix. Binding at this site displaces the P-loop into the ATP-binding site and was shown to be ATP-competitive.

Correction: Discovery of 4,6-disubstituted pyrimidines as potent inhibitors of the heat shock factor 1 (HSF1) stress pathway and CDK9. See DOI: 10.1039/c6md00159a

Correction for ‘Discovery of 4,6-disubstituted pyrimidines as potent inhibitors of the heat shock factor 1 (HSF1) stress pathway and CDK9’ by Carl S. Rye et al., Med. Chem. Commun., 2016, 7, 1580–1586.