Michael Alistair O'brien

Identification of N-(4-Piperidinyl)-4-(2,6-Dichlorobenzoylamino)-1H-Pyrazole-3-Carboxamide (at7519), a Novel Cyclin Dependent Kinase Inhibitor Using Fragment-Based X-Ray Crystallography and Structure Based Drug Design.

The application of fragment-based screening techniques to cyclin dependent kinase 2 (CDK2) identified multiple (>30) efficient, synthetically tractable small molecule hits for further optimization. Structure-based design approaches led to the identification of multiple lead series, which retained the key interactions of the initial binding fragments and additionally explored other areas of the ATP binding site. The majority of this paper details the structure-guided optimization of indazole (6) using information gained from multiple ligand-CDK2 cocrystal structures. Identification of key binding features for this class of compounds resulted in a series of molecules with low nM affinity for CDK2. Optimisation of cellular activity and characterization of pharmacokinetic properties led to the identification of 33 (AT7519), which is currently being evaluated in clinical trials for the treatment of human cancers.

Fragment-Based Drug Discovery Applied to Hsp90. Discovery of Two Lead Series with High Ligand Efficiency.

Inhibitors of the chaperone Hsp90 are potentially useful as chemotherapeutic agents in cancer. This paper describes an application of fragment screening to Hsp90 using a combination of NMR and high throughput X-ray crystallography. The screening identified an aminopyrimidine with affinity in the high micromolar range and subsequent structure-based design allowed its optimization into a low nanomolar series with good ligand efficiency. A phenolic chemotype was also identified in fragment screening and was found to bind with affinity close to 1 mM. This fragment was optimized using structure based design into a resorcinol lead which has subnanomolar affinity for Hsp90, excellent cell potency, and good ligand efficiency. This fragment to lead campaign improved affinity for Hsp90 by over 1,000,000-fold with the addition of only six heavy atoms. The companion paper (DOI: 10.1021/jm100060b) describes how the resorcinol lead was optimized into a compound that is now in clinical trials for the treatment of cancer.

Abstract 1361: Fragment based drug discovery of selective inhibitors of Fibroblast Growth Factor Receptor (FGFR)

Recent data in a number of tumour types has implicated Fibroblast Growth Factor (FGF) and Fibroblast Growth Factor receptor (FGFR) signalling as being key to the molecular pathology of cancer. A fragment screening campaign was conducted against the tyrosine kinase domain of FGFR1 to detect low molecular weight compounds that bound to the hinge region of the kinase. The screening produced several fragment inhibitors (molecular weight The poster will focus on the description of previously undescribed compounds bearing an imidazo[1,2-a]pyridine core scaffold where selectivity versus other protein kinases, for example FLT3, is obtained using the X-ray crystal structure and structure-based design. In summary we will illustrate how X-ray crystallography and fragment-based drug design (FBDD) can be used to discover compounds with activity in an FGFR driven xenograft model when dosed by the oral route. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1361. doi:10.1158/1538-7445.AM2011-1361