François Gessier

Oxysterols direct immune cell migration via EBI2.

Epstein–Barr virus-induced gene 2 (EBI2, also known as GPR183) is a G-protein-coupled receptor that is required for humoral immune responses; polymorphisms in the receptor have been associated with inflammatory autoimmune diseases. The natural ligand for EBI2 has been unknown. Here we describe the identification of 7α,25-dihydroxycholesterol (also called 7α,25-OHC or 5-cholesten-3β,7α,25-triol) as a potent and selective agonist of EBI2. Functional activation of human EBI2 by 7α,25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high-affinity radioligand binding. Furthermore, we find that 7α,25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A critical enzyme required for the generation of 7α,25-OHC is cholesterol 25-hydroxylase (CH25H). Similar to EBI2 receptor knockout mice, mice deficient in CH25H fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that CH25H generates EBI2 biological activity in vivo and indicates that the EBI2–oxysterol signalling pathway has an important role in the adaptive immune response.

Probing the Proteolytic Stability of β‐Peptides Containing α‐Fluoro‐ and α‐Hydroxy‐β‐Amino Acids

One of the benefits of β‐peptides as potential candidates for biological applications is their stability against common peptidases. Attempts have been made to rationalize this stability by altering the electron availability of a given amide carbonyl bond through the introduction of polar substituents at the α‐position of a single β‐amino acid. Such β‐amino acids (β‐homoglycine, β‐homoalanine), containing one or two fluorine atoms or a hydroxy group in the α‐position, were prepared in enantiopure form. A versatile method for preparing these α‐fluoro‐β‐amino acids by the homologation of appropriate α‐amino acids and C‐OH→C‐F or CO→CF2 substitution with DAST, is described. Consequently, a series of β‐peptides possessing an electronically modified residue at the N terminus or embedded within the chain was synthesized, and their proteolytic stability was investigated against a selection of enzymes. All ten β‐peptides tested were resilient to proteolysis. Introducing a polar, sterically undemanding group, into the α‐position of β‐amino acids in a β‐peptide chain does not appear to facilitate localized or general enzymatic degradation.

Discovery of a Dihydroisoquinolinone Derivative (NVP-CGM097): A Highly Potent and Selective MDM2 Inhibitor Undergoing Phase 1 Clinical Trials in p53wt Tumors

As a result of our efforts to discover novel p53:MDM2 protein-protein interaction inhibitors useful for treating cancer, the potent and selective MDM2 inhibitor NVP-CGM097 (1) with an excellent in vivo profile was selected as a clinical candidate and is currently in phase 1 clinical development. This article provides an overview of the discovery of this new clinical p53:MDM2 inhibitor. The following aspects are addressed: mechanism of action, scientific rationale, binding mode, medicinal chemistry, pharmacokinetic and pharmacodynamic properties, and in vivo pharmacology/toxicology in preclinical species.

A distinct p53 target gene set predicts for response to the selective p53–HDM2 inhibitor NVP-CGM097

Biomarkers for patient selection are essential for the successful and rapid development of emerging targeted anti-cancer therapeutics. In this study, we report the discovery of a novel patient selection strategy for the p53–HDM2 inhibitor NVP-CGM097, currently under evaluation in clinical trials. By intersecting high-throughput cell line sensitivity data with genomic data, we have identified a gene expression signature consisting of 13 up-regulated genes that predicts for sensitivity to NVP-CGM097 in both cell lines and in patient-derived tumor xenograft models. Interestingly, these 13 genes are known p53 downstream target genes, suggesting that the identified gene signature reflects the presence of at least a partially activated p53 pathway in NVP-CGM097-sensitive tumors. Together, our findings provide evidence for the use of this newly identified predictive gene signature to refine the selection of patients with wild-type p53 tumors and increase the likelihood of response to treatment with p53–HDM2 inhibitors, such as NVP-CGM097. DOI: http://dx.doi.org/10.7554/eLife.06498.001

EBI2 regulates intracellular signaling and migration in human astrocyte

The G protein‐coupled receptor EBI2 (Epstein–Barr virus‐induced gene 2) is activated by 7α, 25‐dihydroxycholesterol (7α25HC) and plays a role in T cell‐dependant antibody response and B cell migration. Aberrant EBI2 signaling is implicated in a range of autoimmune disorders however its role in the CNS remains unknown. Here we characterize the functional role of EBI2 in GLIA cells using primary human astrocytes and EBI2 knockout animals. We find human and mouse astrocytes express EBI2 and the enzymes necessary for synthesis and degradation of 7α25HC. In astrocytes, EBI2 activation stimulates ERK phosphorylation, Ca2+ signaling and induces cellular migration. These results, for the first time, demonstrate a role for EBI2 in astrocyte function and suggest that modulation of this receptor may be beneficial in neuroinflammatory disorders. GLIA 2015;63:341–351

Transcriptional regulation and functional characterization of the oxysterol/EBI2 system in primary human macrophages.

Oxysterols such as 7 alpha, 25-dihydroxycholesterol (7α,25-OHC) are natural ligands for the Epstein-Barr virus (EBV)-induced gene 2 (EBI2, aka GPR183), a G protein-coupled receptor (GPCR) highly expressed in immune cells and required for adaptive immune responses. Activation of EBI2 by specific oxysterols leads to chemotaxis of B cells in lymphoid tissues. While the ligand gradient necessary for this critical process of the adaptive immune response is established by a stromal cells subset here we investigate the involvement of the oxysterol/EBI2 system in the innate immune response. First, we show that primary human macrophages express EBI2 and the enzymes needed for ligand production such as cholesterol 25-hydroxylase (CH25H), sterol 27-hydroxylase (CYP27A1), and oxysterol 7α-hydroxylase (CYP7B1). Furthermore, challenge of monocyte-derived macrophages with lipopolysaccharides (LPS) triggers a strong up-regulation of CH25H and CYP7B1 in comparison to a transient increase in EBI2 expression. Stimulation of EBI2 expressed on macrophages leads to calcium mobilization and to directed cell migration. Supernatants of LPS-stimulated macrophages are able to stimulate EBI2 signaling indicating that an induction of CH25H, CYP27A1, and CYP7B1 results in an enhanced production and release of oxysterols into the cellular environment. This is a study characterizing the oxysterol/EBI2 pathway in primary monocyte-derived macrophages. Given the crucial functional role of macrophages in the innate immune response these results encourage further exploration of a possible link to systemic autoimmunity.

Discovery of dihydroisoquinolinone derivatives as novel inhibitors of the p53-MDM2 interaction with a distinct binding mode.

Blocking the interaction between the p53 tumor suppressor and its regulatory protein MDM2 is a promising therapeutic concept under current investigation in oncology drug research. We report here the discovery of the first representatives of a new class of small molecule inhibitors of this protein-protein interaction: the dihydroisoquinolinones. Starting from an initial hit identified by virtual screening, a derivatization program has resulted in compound 11, a low nanomolar inhibitor of the p53-MDM2 interaction showing significant cellular activity. Initially based on a binding mode hypothesis, this effort was then guided by a X-ray co-crystal structure of MDM2 in complex with one of the synthesized analogs. The X-ray structure revealed an unprecedented binding mode for p53-MDM2 inhibitors.

Identification and characterization of small molecule modulators of the Epstein-Barr virus-induced gene 2 (EBI2) receptor.

Oxysterols have recently been identified as natural ligands for a G protein-coupled receptor called EBI2 (aka GPR183) ( Nature 2011 , 475 , 524 ; 519 ). EBI2 is highly expressed in immune cells ( J. Biol. Chem. 2006 , 281 , 13199 ), and its activation has been shown to be critical for the adaptive immune response and has been genetically linked to autoimmune diseases such as type I diabetes ( Nature 2010 , 467 , 460 ). Here we describe the isolation of a potent small molecule antagonist for the EBI2 receptor. First, we identified a small molecule agonist NIBR51 (1), which enabled identification of inhibitors of receptor activation. One antagonist called NIBR127 (2) was used as a starting point for a medicinal chemistry campaign, which yielded NIBR189 (4m). This compound was extensively characterized in binding and various functional signaling assays. Furthermore, we have used 4m to block migration of a monocyte cell line called U937, suggesting a functional role of the oxysterol/EBI2 pathway in these immune cells.

Discovery of C-(1-aryl-cyclohexyl)-methylamines as selective, orally available inhibitors of dipeptidyl peptidase IV.

The successful launches of dipeptidyl peptidase IV (DPP IV) inhibitors as oral anti-diabetics warrant and spur the further quest for additional chemical entities in this promising class of therapeutics. Numerous pharmaceutical companies have pursued their proprietary candidates towards the clinic, resulting in a large body of published chemical structures associated with DPP IV. Herein, we report the discovery of a novel chemotype for DPP IV inhibition based on the C-(1-aryl-cyclohexyl)-methylamine scaffold and its optimization to compounds which selectively inhibit DPP IV at low-nM potency and exhibit an excellent oral pharmacokinetic profile in the rat.

Abstract 1798: Mechanistic study of NVP-CGM097: a potent, selective and species specific inhibitor of p53-Mdm2

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA An effective strategy to restore p53 activity in cancer cells containing wild type p53 is to inhibit the Mdm2-p53 protein-protein interaction (PPI). NVP-CGM097 is a novel PPI inhibitor under evaluation in a Phase I clinical trial. It binds to the p53 binding-site of the Mdm2 protein, disrupting the interaction between both proteins, leading to an activation of the p53 pathway. The main biophysical and biochemical inhibitory characteristics of NVP-CGM097 are presented here. These include an affinity constant for Mdm2 in the nanomolar range and a selectivity of 3 orders of magnitude vs. Mdm4. The binding kinetics of NVP-CGM097 to Mdm2 are characterized by a high association rate constant (Kon =37 x 106 M-1.s-1) and a moderate dissociation rate constant (Koff =0.071 s-1). Additionally, NVP-CGM097 exhibits an 8-fold greater affinity for Mdm2 over Nutlin-3 due to a longer residence time of the Mdm2-inhibitor complex. Moreover, biochemical studies have revealed the species specificity of NVP-CGM097 with human Mdm2 being inhibited more strongly than the dog, mouse or rat forms of the protein. This was confirmed in cellular assays where NVP-CGM097 treatment resulted in induction of p53 target gene expression (p21, PUMA and Mdm2) only in human, but not in dog, mouse or rat cell lines. Citation Format: Therese Valat, Keiichi Masuya, Frederic Baysang, Genevieve Albrecht, Nicole Buschmann, Dirk Erdmann, Pascal Furet, Tobias Gabriel, Francois Gessier, Francesco Hofmann, Philipp Holzer, Joerg Kallen, Carole Pissot-Solderman, Stefan Stutz, Patrick Chene, Sebastien Jeay. Mechanistic study of NVP-CGM097: a potent, selective and species specific inhibitor of p53-Mdm2. [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 1798. doi:10.1158/1538-7445.AM2014-1798