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Background Several factors contribute to the development failure of novel pharmaceuticals, one of the most important being adverse effects in pre-clinical and clinical studies. Early identification of off-target compound activity can reduce safety-related attrition in development. In vitro profiling of drug candidates against a broad range of targets is an important part of the compound selection process. Many compounds are synthesized during early drug discovery, making it necessary to assess poly-pharmacology at a limited number of targets. This paper describes how a rational, statistical-ranking approach was used to generate a cost-effective, optimized panel of assays that allows selectivity focused structure-activity relationships to be explored for many molecules. This panel of 50 targets has been used to routinely screen Roche small molecules generated across a diverse range of therapeutic targets. Target hit rates from the Bioprint® database and internal Roche compounds are discussed. We further describe an example of how this panel was used within an anti-infective project to reduce in vivo testing. Method To select the optimized panel of targets, IC50 values of compounds in the BioPrint® database were used to identify assay “hits” i.e. IC50 ≤ 1 μM in 123 different in vitro pharmacological assays. If groups of compounds hit the same targets, the target with the higher hit rate was selected, while others were considered redundant. Using a step-wise analysis, an assay panel was identified to maximize diversity and minimize redundancy. Over a five-year period, this panel of 50 off-targets was used to screen ≈1200 compounds synthesized for Roche drug discovery programs. Compounds were initially tested at 10 μM and hit rates generated are reported. Within one project, the number of hits was used to refine the choice of compounds being assessed in vivo. Results 95% of compounds from the BioPrint® panel were identified within the top 47-ranked assays. Based on this analytical approach and the addition of three targets with established safety concerns, a Roche panel was created for external screening. hERG is screened internally and not included in this analysis. Screening at 10 μM in the Roche panel identified that adenosine A3 and 5HT2B receptors had the highest hit rates (~30%), with 50% of the targets having a hit rate of ≤4%. An anti-infective program identified that a high number of hits in the Roche panel was associated with mortality in 19 mouse tolerability studies. To reduce the severity and number of such studies, future compound selections integrated the panel hit score into the selection process for in vivo studies. It was identified that compounds which hit less targets in the panel and had free plasma exposures of ~2 μM were generally better tolerated. Discussion This paper describes how an optimized panel of 50 assays was selected on the basis of hit similarity at 123 targets. This reduced panel, provides a cost-effective screening panel for assessing compound promiscuity, whilst also including many safety-relevant targets. Frequent use of the panel in early drug discovery has provided promiscuity and safety-relevant information to inform pre-clinical drug development at Roche.

Negative allosteric modulators (NAMs) of metabotropic glutamate receptor 5 (mGlu5) have potential for the treatment of psychiatric diseases including depression, fragile X syndrome (FXS), anxiety, obsessive-compulsive disorders, and levodopa induced dyskinesia in Parkinson's disease. Herein we report the optimization of a weakly active screening hit 1 to the potent and selective compounds chloro-4-[1-(4-fluorophenyl)-2,5-dimethyl-1H-imidazol-4-ylethynyl]pyridine (basimglurant, 2) and 2-chloro-4-((2,5-dimethyl-1-(4-(trifluoromethoxy)phenyl)-1H-imidazol-4-yl)ethynyl)pyridine (CTEP, 3). Compound 2 is active in a broad range of anxiety tests reaching the same efficacy but at a 10- to 100-fold lower dose compared to diazepam and is characterized by favorable DMPK properties in rat and monkey as well as an excellent preclinical safety profile and is currently in phase II clinical studies for the treatment of depression and fragile X syndrome. Analogue 3 is the first reported mGlu5 NAM with a long half-life in rodents and is therefore an ideal tool compound for chronic studies in mice and rats.

Several drugs (clozapine, chlorpromazine, imipramine, buspirone, diltiazem, and propranolol) were subjected to modified Udenfriend conditions (Fe 2+ /Mn 2+ /EDTA/ascorbic acid/O 2 ). From each reaction, one to four oxidation products were obtained in 1–8% overall yield. Many of these products (9 out of 14) have been reported to be metabolites of the parent drugs in vivo. The products resulted mainly from aromatic hydroxylation, and are not readily accessible by conventional synthesis. Thus, the described reaction may be useful in drug discovery whenever a facile synthetic access is more important than high yields (e.g., for a fast derivatisation of compounds or the preparation of metabolites). Poorly water-soluble compounds cannot be converted, which is an important limitation of this method.

During a program directed at selective NK(1) receptor antagonists, we serendipitously discovered an NK(1) receptor ligand with additional affinity for the NK(3) receptor. Recognising an opportunity for a drug discovery program aiming for dual NK(1)/NK(3) receptor antagonists, we prepared a series of analogues from a novel, versatile building block. From this series emerged compounds with high and balanced affinities for the NK(1) and the NK(3) receptors. Typical representatives of this series were active in the gerbil foot tapping assay after oral administration.

2-Quinolones are prepared from o -aminophenylketones by N-acylation with phosphonoalkanoylchlorides, followed by an intramolecular Horner–Wadsworth–Emmons olefination. The transformation proceeds under mild conditions, is generally applicable, gives good yields and can be performed either in two steps or as a one-pot reaction.

Detailed information on the metabolic fate of lead compounds can be a powerful tool for an informed approach to the stabilization of metabolically labile compounds in the lead optimization phase. The combination of high performance liquid chromatography (HPLC) with nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) has been used to give comprehensive structural data on metabolites of novel drugs in development. Recently, increased automation and the embedding of on-line solid-phase extraction (SPE) into a integrated LC-SPE-NMR-MS system have improved enormously the detection limits of this approach. The new technology platform allows the analysis of complex mixtures from microsome incubations, combining low material requirements with relatively high throughput. Such characteristics make it possible to thoroughly characterize metabolites of selected compounds at earlier phases along the path to lead identification and clinical candidate selection, thus providing outstanding guidance in the process of eliminating undesired metabolism and detecting active or potentially toxic metabolites. Such an approach was applied at the lead identification stage of a backup program on metabotropic glutamate receptor 5 (mGlu5) allosteric inhibition. The major metabolites of a lead 5-aminothiazole-4-carboxylic acid amide 1 were synthesized and screened, revealing significant in vitro activity and possible involvement in the overall pharmacodynamic behavior of 1. The information collected on the metabolism of the highly active compound 1 was pivotal to the synthesis of related compounds with improved microsomal stability.

In a search for novel DPP-IV inhibitors, 2-aminobenzo[a]quinolizines were identified as submicromolar HTS hits. Due to the difficult synthetic access to this compound class, 1,3-disubstituted 4-aminopiperidines were used as model compounds for optimization. The developed synthetic methodology and the SAR could be transferred to the 2-aminobenzo[a]quinolizine series, leading to highly active DPP-IV inhibitors.

Cyanopyrrolidines (cyanopyrrolidides, pyrrolidine-2-nitriles, prolinenitriles) as inhibitors of the serine protease dipeptidyl peptidase IV (DPP-IV, DP IV, CD26, EC 3.4.14.5) were first reported in 1995. The interest in this compound class grew immensely when DPP-IV was discovered as a target for the treatment of type 2 diabetes. The research on cyanopyrrolidines cumulated in the discoveries of vildagliptin (LAF237, NVP-LAF237) and saxagliptin (BMS-477118). These compounds entered Phase III clinical trials in 2004 and 2005, respectively, and an application for market approval has been filed for vildagliptin in 2006. Today cyanopyrrolidines are, as judged by the numbers of patent applications, the most prominent of several series of DPP-IV inhibitors, and have the potential to become valuable medicines for type 2 diabetes in the near future. This review summarizes some historical aspects of the discovery of cyanopyrrolidine DPP-IV inhibitors, and then focuses mainly on structure-activity-relationships, the evolution of different subseries, the possibilities to improve on the chemical instability that is associated with this compound class, and on the discoveries of vildagliptin and saxagliptin. Within this context, the properties of individual compounds and results from biological studies are discussed. The rationale of DPP-IV inhibition, clinical data, and the relevance of selectivity over related proteases are extensively reviewed in other contributions to this issue of Curr. Top. Med. Chem., and are therefore only very briefly touched.

Prevalence of type 2 diabetes has increased dramatically in the last decades. Current medicines are not yet capable to efficiently prevent or reverse progression of the disease and its associated comorbidities. As a consequence, there is a great need for novel antidiabetic drugs. Treatments of type 2 diabetes that are based on enhanced and sustained action of insulinotropic incretin hormones such as GLP-1 have received much attention in the past years. Treatment strategies include administration of: 1) GLP-1 analogues that are resistant to degradation by the serine protease DPP-IV, and 2) small molecule DPP-IV inhibitors that are able to provide sustained action of endogenous GLP-1, again by preventing its degradation. This review summarizes recent research results for the second approach. It briefly touches upon the advantages that treatment of type 2 diabetes with DPP-IV inhibitors may offer over current medications. In the main section, several important structural classes of DPP-IV inhibitors are described and compared based on literature data. Specific attention is given to the analysis of several X-ray structures of enzyme-inhibitor co-crystals. Finally, as clinical data are steadily emerging for some of the most advanced development candidates, the last section of this review is providing a brief overview of some efficacy data from recent clinical studies with DPP-IV inhibitors.

Fenobam [N-(3-chlorophenyl)-N'-(4,5-dihydro-1-methyl-4-oxo-1H-imidazole-2-yl)urea] is an atypical anxiolytic agent with unknown molecular target that has previously been demonstrated both in rodents and human to exert anxiolytic activity. Here, we report that fenobam is a selective and potent metabotropic glutamate (mGlu)5 receptor antagonist acting at an allosteric modulatory site shared with 2-methyl-6-phenylethynyl-pyridine (MPEP), the protypical selective mGlu5 receptor antagonist. Fenobam inhibited quisqualate-evoked intracellular calcium response mediated by human mGlu5 receptor with IC(50) = 58 +/- 2 nM. It acted in a noncompetitive manner, similar to MPEP and demonstrated inverse agonist properties, blocking 66% of the mGlu5 receptor basal activity (in an over expressed cell line) with an IC(50) = 84 +/- 13 nM. [(3)H]Fenobam bound to rat and human recombinant receptors with K(d) values of 54 +/- 6 and 31 +/- 4 nM, respectively. MPEP inhibited [(3)H]fenobam binding to human mGlu5 receptors with a K(i) value of 6.7 +/- 0.7 nM, indicating a common binding site shared by both allosteric antagonists. Fenobam exhibits anxiolytic activity in the stress-induced hyperthermia model, Vogel conflict test, Geller-Seifter conflict test, and conditioned emotional response with a minimum effective dose of 10 to 30 mg/kg p.o. Furthermore, fenobam is devoid of GABAergic activity, confirming previous reports that fenobam acts by a mechanism distinct from benzodiazepines. The non-GABAergic activity of fenobam, coupled with its robust anxiolytic activity and reported efficacy in human in a double blind placebo-controlled trial, supports the potential of developing mGlu5 receptor antagonists with an improved therapeutic window over benzodiazepines as novel anxiolytic agents.

Fenobam is a clinically efficacious anxiolytic that acts as metabotropic glutamate receptor 5 (mGlu5) antagonist by binding to an allosteric site. Other mGlu5 receptor antagonists such as MPEP and MTEP bind to the same allosteric site and are efficacious in preclinical models of anxiety and depression. Consequently, the allosteric-binding site of the mGlu5 receptor is an attractive target for the discovery of novel psychiatric therapies. Radioligands of this binding site can be used for in vitro and in vivo pharmacodynamic studies. We report here a short synthesis of such a radioligand for the allosteric mGlu5 receptor-binding site, [3H]fenobam. Copyright © 2008 John Wiley & Sons, Ltd.

Polypharmacology describes the activity of compounds at multiple targets. Current research focuses on two aspects of polypharmacology: (1) unintended polypharmacology can lead to adverse effects; (2) polypharmacology across several disease-relevant targets can improve therapeutic efficacy, prevent drug resistance, or reduce therapeutic-target-related adverse effects. This perspective reviews these interconnected aspects of polypharmacology. The first part discusses the relevance of polypharmacology for the safety of drugs, the mitigation of safety risks, and methods to identify polypharmacological compounds early in the drug discovery process. The second part discusses the advantages of polypharmacology in the treatment of multigenic diseases and infections, and opportunities for drug discovery and drug repurposing. This perspective aims to provide a balanced view on polypharmacology, which can compromise the safety of drugs, but can also confer superior efficacy.

The term 'pharmacological promiscuity' describes the activity of a single compound against multiple targets. When undesired, promiscuity is a major safety concern that needs to be detected as early as possible in the drug discovery process. The analysis of large datasets reveals that the majority of promiscuous compounds are characterized by recognizable molecular properties and structural motifs, the most important one being a basic center with a pK(a)(B)>6. These compounds interact with a small set of targets such as aminergic GPCRs; some of these targets attract surprisingly high hit rates. In this review, we discuss current trends in the assessment of pharmacological promiscuity and propose strategies to enable early detection and mitigation.

Pyrido pyrimidinones are selective agonists of the human high affinity niacin receptor GPR109A (HM74A). They show no activity on the highly homologous low affinity receptor GPR109B (HM74). Starting from a high throughput screening hit the in vitro activity of the pyrido pyrimidinones was significantly improved providing lead compounds suitable for further optimization.

Structural modifications of the gamma-secretase inhibitor, LY411575, led to a malonamide analogue (S),(S)-1 with potent inhibitory activity in vitro, but disappointing activity in a mouse model of Alzheimer's disease. Identification and replacement of a metabolically labile position provided an improved compound (R/S),(S)-13 with high in vitro activity (IC(50)=1.7 nM), and in vivo activity after oral administration (MED=3 mg/kg). Further modifications gave an equipotent carbamate analogue 14 with improved molecular properties.

Fragment screening revealed that tyramine binds to the active site of the Alzheimer's disease drug target BACE-1. Hit expansion by selection of compounds from the Roche compound library identified tyramine derivatives with improved binding affinities as monitored by surface plasmon resonance. X-ray structures show that the amine of the tyramine fragment hydrogen-bonds to the catalytic water molecule. Structure-guided ligand design led to the synthesis of further low molecular weight compounds that are starting points for chemical leads.

The optimisation of affinity and selectivity in a novel series of dual 5-HT 5A /5-HT 7 receptor ligands is described. Brain penetrant 2-aminodihydroquinazolines with low nanomolar affinities were identified.

The optimisation of molecular properties within a series of 2-amino dihydroquinazoline 5-HT5A/5-HT7 receptor ligands resulted in a significantly improved brain-to-plasma ratio, enhancing the pharmacological utility of these compounds. By modulating the lipophilicity and pKa, a 20-fold increase in brain-to-plasma ratio could be achieved, leading to micromolar brain concentrations after oral administration. The enantiomers of one representative of this series of improved compounds were separated, and the configuration of the eutomer was determined by X-ray crystallography.

Structural modifications of the gamma-secretase inhibitor, LY411575, led to a malonamide analogue (S),(S)-1 with potent inhibitory activity in vitro, but disappointing activity in a mouse model of Alzheimer's disease. Identification and replacement of a metabolically labile position provided an improved compound (R/S),(S)-13 with high in vitro activity (IC(50)=1.7 nM), and in vivo activity after oral administration (MED=3 mg/kg). Further modifications gave an equipotent carbamate analogue 14 with improved molecular properties.

Optimization of affinity and microsomal stability led to identification of the potent, metabolically stable fenobam analog 4l. Robust in vivo efficacy of 4l was demonstrated in four different models of anxiety. Additionally, a ligand based pharmacophore alignment of fenobam and MPEP is proposed.

Optimisation of affinity, chemical stability, metabolic stability and solubility led from a chemically labile HTS hit 1 to mGlu5 receptor antagonists (24-26) with high affinity for the allosteric MPEP binding site, improved microsomal metabolic stability and anxiolytic-like activity in vivo as assessed by the Vogel conflict drinking test.

In a novel series of DPP-IV inhibitors, a large increase of inhibitory activity was achieved by optimisation of aromatic substituents and conformational restriction.

A recently identified DPP-IV inhibitor (1) was found to induce phospholipidosis and to inhibit CYP3A4. A small series of less lipophilic and less amphiphilic analogues was synthesized in an effort to overcome these issues. One compound from this series was equipotent to 1, did not induce phospholipidosis and showed a reduced CYP3A4 inhibition.

The influence of aromatic substitution on a newly discovered class of inhibitors of dipeptidyl peptidase IV was investigated. A 10(5)-fold increase in potency was achieved by the optimization of aromatic substituents in a parallel chemistry program. The observed SAR could be explained by an X-ray structure of the protein-ligand complex.

The α-effect can be used in the acceleration of the Diels–Alder reaction between a series of dienes and electron deficient dienophiles using iminium ion catalysis, providing a novel molecular scaffold capable of performing this class of catalytic process.

The alpha-effect can be used in the acceleration of the Diels-Alder reaction between a series of dienes and electron deficient dienophiles using iminium ion catalysis, providing a novel molecular scaffold capable of performing this class of catalytic process.

A novel two-step procedure for the preparation of diprotected anthranilic acid derivatives from ortho-bromoanilines is described.

In a novel application of [PhCH2Ru(PCy3)2Cl2] 1, triynes are isomerised to benzene derivatives; a cascade of four metathesis reactions is proposed as a mechanistic explanation.

In this book chapter, we first introduce the concept of multitargeted drugs in neurodegenerative diseases. Then, we report and discuss some examples of multitargeted drug candidates in (pre)clinical trials for the treatment of Alzheimer's disease.