Clifford David Jones

Sustained Mps1 activity is required in mitosis to recruit O-Mad2 to the Mad1–C-Mad2 core complex

To satisfy the mitotic checkpoint and drive chromosome congression, the Mps1 kinase lets go of kinetochores by phosphorylating itself in trans (see also related papers by Maciejowski et al. and Santaguida et al. in this issue).

Structure-Guided Design of Highly Selective and Potent Covalent Inhibitors of Erk1/2.

The RAS/RAF/MEK/ERK signaling pathway has been targeted with a number of small molecule inhibitors in oncology clinical development across multiple disease indications. Importantly, cell lines with acquired resistance to B-RAF and MEK inhibitors have been shown to maintain sensitivity to ERK1/2 inhibition by small molecule inhibitors. There are a number of selective, noncovalent ERK1/2 inhibitors reported along with the promiscuous hypothemycin (and related analogues) that act via a covalent mechanism of action. This article reports the identification of multiple series of highly selective covalent ERK1/2 inhibitors informed by structure-based drug design (SBDD). As a starting point for these covalent inhibitors, reported ERK1/2 inhibitors and a chemical series identified via high-throughput screening were exploited. These approaches resulted in the identification of selective covalent tool compounds for potential in vitro and in vivo studies to assess the risks and or benefits of targeting this pathway through such a mechanism of action.

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.

Abstract 2348: Discovery of AZD6738, a potent and selective inhibitor with the potential to test the clinical efficacy of ATR kinase inhibition in cancer patients.

AZD6738 is a potent and selective inhibitor of ataxia telangiectasia and rad3 related (ATR) kinase with the potential to be used in the clinic. We report the discovery of a morpholino-pyrimidine series and its subsequent optimisation to the pre-clinical candidate AZD6738 which has a good overall balance of potency, selectivity, pharmacokinetic and biopharmaceutical properties suitable for oral dosing. ATR is a serine/threonine protein kinase involved in DNA damage response signalling caused by DNA replication associated stress. Activation of ATR at stalled replication forks leads to suppression of replication fork origin firing, promotes repair and S/G2-cell cycle checkpoints to prevent premature mitosis and maintain genomic integrity. Failure to resolve damage leads to genomic instability and if sufficiently high, cell death. Stalled replication forks may collapse leading to formation of DNA double stranded breaks and activation of the ataxia telangiectasia mutated (ATM) kinase. ATM works in conjunction with ATR to efficiently resolve replication associated DNA damage creating a co-dependency with loss of one leading to a greater reliance on the other to maintain genomic stability. ATM is frequently inactivated across B-cell malignancies, head and neck, breast and lung cancers through chromosomal deletion, promoter hypermethylation or mutation. ATM-deficient tumours are hypothesised to be more reliant on ATR for survival and specific inhibition of ATR may lead enhanced anti-tumour activity while minimizing normal tissue toxicity. AZD6378 has the potential to test the clinical efficacy of ATR inhibition in cancer patients as monotherapy against ATM-deficient tumours or in combination with chemo or radiotherapy. Citation Format: Clifford D. Jones, Kevin Blades, Kevin M. Foote, Sylvie M. Guichard, Philip J. Jewsbury, Thomas McGuire, Johannes W. Nissink, Rajesh Odedra, Kin Tam, Pia Thommes, Paul Turner, Gary Wilkinson, Christine Wood, James W. Yates. Discovery of AZD6738, a potent and selective inhibitor with the potential to test the clinical efficacy of ATR kinase inhibition in cancer patients. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2348. doi:10.1158/1538-7445.AM2013-2348

Novel imidazo[1,2-a]pyridine based inhibitors of the IGF-1 receptor tyrosine kinase: Optimization of the aniline

Following the discovery of imidazopyridine 1 as a potent IGF-1R tyrosine kinase inhibitor, the aniline part has been modified with the aim to optimize the properties of this series. The structure-activity relationships against IGF-1R kinase activity as well as inhibition of the hERG ion channel are discussed.

Imidazole pyrimidine amides as potent, orally bioavailable cyclin-dependent kinase inhibitors

The development of a novel series of imidazole pyrimidine amides as cyclin-dependent kinase (CDK) inhibitors is described. The series was found to have much improved CDK2 inhibition and potent in vitro anti-proliferative effects against cancer cell lines. Control of overall lipophilicity was important to achieve good in vitro potency along with acceptable physiochemical properties and margins against inhibition of both CYP isoforms and the hERG potassium ion channel. A compound with an attractive overall balance of properties was profiled in vivo and possessed suitable physiochemical and pharmacokinetic profiles for oral dosing.

Cellularly active N -hydroxyurea FEN1 inhibitors block substrate entry to the active site

The structure-specific nuclease human flap endonuclease-1 (hFEN1) plays a key role in DNA replication and repair and may be of interest as an oncology target. We present the first crystal structure of inhibitor-bound hFEN1 and show a cyclic N-hydroxyurea bound in the active site coordinated to two magnesium ions. Three such compounds had similar IC50 values but differed subtly in mode of action. One had comparable affinity for protein and protein–substrate complex and prevented reaction by binding to active site catalytic metal ions, blocking the unpairing of substrate DNA necessary for reaction. Other compounds were more competitive with substrate. Cellular thermal shift data showed engagement of both inhibitor types with hFEN1 in cells with activation of the DNA damage response evident upon treatment. However, cellular EC50s were significantly higher than in vitro inhibition constants and the implications of this for exploitation of hFEN1 as a drug target are discussed.

Abstract 3343: The pre-clinical in vitro and in vivo activity of AZD6738: A potent and selective inhibitor of ATR kinase.

AZD6738 is a potent and selective orally bioavailable kinase inhibitor of ataxia telangiectasia and rad3 related (ATR). Here we report the pre-clinical in vitro and in vivo and biological profile of AZD6738. ATR is a serine/threonine protein kinase involved in DNA damage response signalling caused by DNA replication associated stress. Activation of ATR at stalled replication forks leads to suppression of replication fork origin firing, promotes repair and S/G2-cell cycle checkpoints to prevent premature mitosis and maintain genomic integrity. Failure to resolve damage leads to genomic instability and if sufficiently high, cell death. Stalled replication forks may collapse leading to formation of DNA double stranded breaks and activation of the ataxia telangiectasia mutated (ATM) kinase. ATM works in conjunction with ATR to efficiently resolve replication associated DNA damage creating a co-dependency with loss of one leading to a greater reliance on the other to maintain genomic stability. ATM is frequently inactivated across B-cell malignancies, head and neck, breast and lung cancers through chromosomal deletion, promoter hypermethylation or mutation. ATM-deficient tumours are hypothesised to be more reliant on ATR for survival and specific inhibition of ATR may lead enhanced anti-tumour activity while minimizing normal tissue toxicity. AZD6738 demonstrates this preclinical profile. AZD6738 inhibits the phosphorylation of direct downstream substrate CHK1 while increasing the phosphorylation of ATM-dependent substrate CHK2 and DNA damage marker γH2AX. This is associated with impaired S-phase cell cycle progression with prolonged inhibition causing cell death, indicative of replication fork stalling, collapse and irreversible damage. AZD6738 is active as a single agent across cancer cell line panels but shows enhanced sensitivity in cell lines with ATM-pathway defects. AZD6738 when used in combination with DNA damaging inducing agents’ gemcitabine, cisplatin or ionising radiation (IR) shows enhanced synergistic cell killing activity. In vivo, AZD6738 monotherapy treatment leads to significant anti-tumour activity in ATM-deficient but not ATM-proficient xenograft models at equivalent, tolerated doses. When AZD6738 is used in combination with carboplatin or IR anti-tumour growth inhibitory activity or regression is observed. AZD6738 in vivo activity is also associated with a persistent increased γH2AX staining in tumour tissue but only a transient increase in normal bone marrow or gut tissue suggesting a favourable therapeutic index can be achieved. Early pre-clinical safety studies support these findings with target related bone marrow suppression, neutropenia and GI tract impact only at high-doses. These data merit further investigation of AZD6738 as a monotherapy or in combination with chemo or radiotherapy. Citation Format: Sylvie M. Guichard, Elaine Brown, Rajesh Odedra, Adina Hughes, Dan Heathcote, Jen Barnes, Alan Lau, Steve Powell, Clifford D. Jones, Willem Nissink, Kevin M. Foote, Philip J. Jewsbury, Martin Pass. The pre-clinical in vitro and in vivo activity of AZD6738: A potent and selective inhibitor of ATR kinase. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3343. doi:10.1158/1538-7445.AM2013-3343

Structure-Guided Discovery of Potent and Selective Inhibitors of ERK1/2 from a Modestly Active and Promiscuous Chemical Start Point.

There are a number of small-molecule inhibitors targeting the RAS/RAF/MEK/ERK signaling pathway that have either been approved or are in clinical development for oncology across a range of disease indications. The inhibition of ERK1/2 is of significant current interest, as cell lines with acquired resistance to BRAF and MEK inhibitors have been shown to maintain sensitivity to ERK1/2 inhibition in preclinical models. This article reports on our recent work to identify novel, potent, and selective reversible ERK1/2 inhibitors from a low-molecular-weight, modestly active, and highly promiscuous chemical start point, compound 4. To guide and inform the evolution of this series, inhibitor binding mode information from X-ray crystal structures was critical in the rapid exploration of this template to compound 35, which was active when tested in in vivo antitumor efficacy experiments.

Discovery of a Potent, Selective, Orally Bioavailable, and Efficacious Novel 2-(Pyrazol-4-ylamino)-pyrimidine Inhibitor of the Insulin-like Growth Factor-1 Receptor (IGF-1R)

Optimization of cellular lipophilic ligand efficiency (LLE) in a series of 2-anilino-pyrimidine IGF-1R kinase inhibitors led to the identification of novel 2-(pyrazol-4-ylamino)-pyrimidines with improved physicochemical properties. Replacement of the imidazo[1,2-a]pyridine group of the previously reported inhibitor 3 with the related pyrazolo[1,5-a]pyridine improved IGF-1R cellular potency. Substitution of the amino-pyrazole group was key to obtaining excellent kinase selectivity and pharmacokinetic parameters suitable for oral dosing, which led to the discovery of (2R)-1-[4-(4-{[5-chloro-4-(pyrazolo[1,5-a]pyridin-3-yl)-2-pyrimidinyl]amino}-3,5-dimethyl-1H-pyrazol-1-yl)-1-piperidinyl]-2-hydroxy-1-propanone (AZD9362, 28), a novel, efficacious inhibitor of IGF-1R.