Valerio Berdini

Fragment-Based Discovery of the Pyrazol-4-Yl Urea (at9283), a Multitargeted Kinase Inhibitor with Potent Aurora Kinase Activity.

Here, we describe the identification of a clinical candidate via structure-based optimization of a ligand efficient pyrazole-benzimidazole fragment. Aurora kinases play a key role in the regulation of mitosis and in recent years have become attractive targets for the treatment of cancer. X-ray crystallographic structures were generated using a novel soakable form of Aurora A and were used to drive the optimization toward potent (IC(50) approximately 3 nM) dual Aurora A/Aurora B inhibitors. These compounds inhibited growth and survival of HCT116 cells and produced the polyploid cellular phenotype typically associated with Aurora B kinase inhibition. Optimization of cellular activity and physicochemical properties ultimately led to the identification of compound 16 (AT9283). In addition to Aurora A and Aurora B, compound 16 was also found to inhibit a number of other kinases including JAK2 and Abl (T315I). This compound demonstrated in vivo efficacy in mouse xenograft models and is currently under evaluation in phase I clinical trials.

Crystal structure of human soluble adenylate cyclase reveals a distinct, highly flexible allosteric bicarbonate binding pocket.

Soluble adenylate cyclases catalyse the synthesis of the second messenger cAMP through the cyclisation of ATP and are the only known enzymes to be directly activated by bicarbonate. Here, we report the first crystal structure of the human enzyme that reveals a pseudosymmetrical arrangement of two catalytic domains to produce a single competent active site and a novel discrete bicarbonate binding pocket. Crystal structures of the apo protein, the protein in complex with α,β‐methylene adenosine 5′‐triphosphate (AMPCPP) and calcium, with the allosteric activator bicarbonate, and also with a number of inhibitors identified using fragment screening, all show a flexible active site that undergoes significant conformational changes on binding of ligands. The resulting nanomolar‐potent inhibitors that were developed bind at both the substrate binding pocket and the allosteric site, and can be used as chemical probes to further elucidate the function of this protein.

Potent, Selective Inhibitors of Fibroblast Growth Factor Receptor Define Fibroblast Growth Factor Dependence in Preclinical Cancer Models

We describe here the identification and characterization of 2 novel inhibitors of the fibroblast growth factor receptor (FGFR) family of receptor tyrosine kinases. The compounds exhibit selective inhibition of FGFR over the closely related VEGFR2 receptor in cell lines and in vivo. The pharmacologic profile of these inhibitors was defined using a panel of human tumor cell lines characterized for specific mutations, amplifications, or translocations known to activate one of the four FGFR receptor isoforms. This pharmacology defines a profile for inhibitors that are likely to be of use in clinical settings in disease types where FGFR is shown to play an important role. Mol Cancer Ther; 10(9); 1542–52. ©2011 AACR.

Fragment-Based Discovery of Type I Inhibitors of Maternal Embryonic Leucine Zipper Kinase

Fragment-based drug design was successfully applied to maternal embryonic leucine zipper kinase (MELK). A low affinity (160 μM) fragment hit was identified, which bound to the hinge region with an atypical binding mode, and this was optimized using structure-based design into a low-nanomolar and cell-penetrant inhibitor, with a good selectivity profile, suitable for use as a chemical probe for elucidation of MELK biology.

Structure-Based Design of Type II Inhibitors Applied to Maternal Embryonic Leucine Zipper Kinase

A novel Type II kinase inhibitor chemotype has been identified for maternal embryonic leucine zipper kinase (MELK) using structure-based ligand design. The strategy involved structural characterization of an induced DFG-out pocket by protein-ligand X-ray crystallography and incorporation of a slender linkage capable of bypassing a large gate-keeper residue, thus enabling design of molecules accessing both hinge and induced pocket regions. Optimization of an initial hit led to the identification of a low-nanomolar, cell-penetrant Type II inhibitor suitable for use as a chemical probe for MELK.

Exploitation of a Novel Binding Pocket in Human Lipoprotein-Associated Phospholipase A2 (Lp-PLA2) Discovered through X-ray Fragment Screening.

Elevated levels of human lipoprotein-associated phospholipase A2 (Lp-PLA2) are associated with cardiovascular disease and dementia. A fragment screen was conducted against Lp-PLA2 in order to identify novel inhibitors. Multiple fragment hits were observed in different regions of the active site, including some hits that bound in a pocket created by movement of a protein side chain (approximately 13 Å from the catalytic residue Ser273). Using structure guided design, we optimized a fragment that bound in this pocket to generate a novel low nanomolar chemotype, which did not interact with the catalytic residues.

Crystal structure of calf spleen purine nucleoside phosphorylase complexed to a novel purine analogue

The combined use of a rapid virtual screen of a small fragment library together with a single point enzyme assay has been used for the discovery of novel PNP inhibitors. The availability of readily soakable crystals of bovine PNP has allowed the approach to be experimentally validated by determining the crystal structure of one of the inhibitor‐PNP complexes. Comparison of the experimentally determined binding mode with that predicted by the virtual screening shows them to be similar. This represents a starting point for the growth of the ligand into a higher affinity inhibitor.

Abstract 4748: Discovery of JNJ-42756493, a potent fibroblast growth factor receptor (FGFR) inhibitor using a fragment based approach

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Fibroblast growth factors (FGFs) and their receptors (FGFR1 through 4) regulate a variety of key cellular processes, including proliferation, migration, survival, and differentiationa. Aberrant activation of FGF/FGFR is strongly implicated in oncogenic signalling in many tumor types. This has stimulated the development of a number of FGFR inhibitors, with diverse kinase inhibition and pharmacological profiles that are currently being evaluated in clinical studies. We conducted a fragment screening campaign and this resulted in identification of a 6-aminoquinoxalinyl fragment with a binding affinity in the micromolar range. Structure-guided medicinal chemistry led to the identification of a novel quinoxaline-based chemical series with nanomolar affinity for FGFR1, 2, 3, and 4, activity in cells, and selectivity with respect to VEGFR-2. Further optimisation resulted in the generation of JNJ-42756493, a compound with favourable drug-like properties that demonstrated strong anti-tumoral activity in a FGFR2-dependent SNU-16 human gastric carcinoma xenograft model. This report represents the first disclosure of the structure-activity relationships as well as the chemical synthesis pathway of the JNJ-42756493 series and illustrates how a fragment-based drug discovery approach has been efficiently used to discover FGFR1-4 inhibitors with nanomolar affinity. aTurner, N. and Grose, R. Nat. Rev. Cancer, 2010, 10, 116-129. Citation Format: Patrick R. Angibaud, Laurence Mevellec, Gordon Saxty, Christophe Adelinet, Rhalid Akkari, Valerio Berdini, Pascal Bonnet, Marine Bourgeois, Xavier Bourdrez, Anne Cleasby, Helene Colombel, Imre Csoka, Werner Embrechts, Eddy Freyne, Ronaldus Gilissen, Eleonora Jovcheva, Peter King, Jean Lacrampe, Delphine Lardeau, Yannick Ligny, Steve Mcclue, Lieven Meerpoel, David R. Newell, Martin Page, Alexandra Papanikos, Elisabeth Pasquier, Isabelle Pilatte, Virginie Poncelet, Olivier Querolle, David C. Rees, Sharna Rich, Bruno Roux, Elodie Sement, Yvan Simonnet, Matthew Squires, Virginie Tronel, Tinne Verhulst, Jorge Vialard, Marc Willems, Steven J. Woodhead, Berthold Wroblowski, Christopher W. Murray, Timothy Perera. Discovery of JNJ-42756493, a potent fibroblast growth factor receptor (FGFR) inhibitor using a fragment based approach. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4748. doi:10.1158/1538-7445.AM2014-4748

Perspective on computational and structural aspects of kinase discovery from IPK2014

Recent advances in understanding the activity and selectivity of kinase inhibitors and their relationships to protein structure are presented. Conformational selection in kinases is studied from empirical, data-driven and simulation approaches. Ligand binding and its affinity are, in many cases, determined by the predetermined active and inactive conformation of kinases. Binding affinity and selectivity predictions highlight the current state of the art and advances in computational chemistry as it applies to kinase inhibitor discovery. Kinome wide inhibitor profiling and cell panel profiling lead to a better understanding of selectivity and allow for target validation and patient tailoring hypotheses. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.

Fragment-based approaches to the discovery of kinase inhibitors.

Protein kinases are one of the most important families of drug targets, and aberrant kinase activity has been linked to a large number of disease areas. Although eminently targetable using small molecules, kinases present a number of challenges as drug targets, not least obtaining selectivity across such a large and relatively closely related target family. Fragment-based drug discovery involves screening simple, low-molecular weight compounds to generate initial hits against a target. These hits are then optimized to more potent compounds via medicinal chemistry, usually facilitated by structural biology. Here, we will present a number of recent examples of fragment-based approaches to the discovery of kinase inhibitors, detailing the construction of fragment-screening libraries, the identification and validation of fragment hits, and their optimization into potent and selective lead compounds. The advantages of fragment-based methodologies will be discussed, along with some of the challenges associated with using this route. Finally, we will present a number of key lessons derived both from our own experience running fragment screens against kinases and from a large number of published studies.