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P. falciparum cGMP-dependent protein kinase (PfPKG) is an enticing anti-malarial drug target. Novel chemotypes are needed because existing inhibitors have safety issues that may prevent further development. This work demonstrates isoxazole-based compounds are potent ATP competitive inhibitors of PfPKG and discloses a new analog in this series. Isoxazoles 3 and 5 had K(i) values that are comparable to a known standard, 4-[2-(4-fluorophenyl)-5-(1-methylpiperidine-4-yl)-1H pyrrol-3-yl] pyridine. They also exhibited excellent selectivity for PfPKG over the human ortholog and the gatekeeper mutant T618Q PfPKG, which mimics the less accessible binding site of the human ortholog. The human ortholog’s larger binding site volume was predicted to explain the selectivity of the inhibitors for the P. falciparum enzyme.

[Image: see text] The discovery of new targets for the treatment of malaria, in particular those aimed at the pre-erythrocytic stage in the life cycle, advanced with the demonstration that orally administered inhibitors of Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) could clear infection in a murine model. This enthusiasm was tempered by unsatisfactory safety and/or pharmacokinetic issues found with these chemotypes. To address the urgent need for new scaffolds, this paper presents initial structure–activity relationships in an imidazole scaffold at four positions, representative in vitro ADME, hERG characterization, and cell-based antiparasitic activity. This series of PfPKG inhibitors has good in vitro PfPKG potency, low hERG activity, and cell-based antiparasitic activity against multiple Plasmodium species that appears to be correlated with the in vitro potency.

The discovery of new targets for treatment of malaria and in particular those aimed at the pre-erythrocytic stage in the life cycle, advanced with the demonstration that orally administered inhibitors of Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) could clear infection in a murine model. This enthusiasm was tempered by unsatisfactory safety and/or pharmacokinetic issues found with these chemotypes. To address the urgent need for new scaffolds, this manuscript presents initial structure-activity relationships in an imidazole scaffold at four positions, representative in vitro ADME, hERG characterization and cell-based anti-parasitic activity. This series of PfPKG inhibitors has good in vitro PfPKG potency, low hERG activity and cell-based anti-parasitic activity against multiple Plasmodium species that appears to correlate with in vitro potency.

The discovery of new targets for treatment of malaria advanced with the demonstration that orally administered inhibitors of Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) could clear infection in a murine model. This enthusiasm was tempered by unsatisfactory safety and/or pharmacokinetic issues found with these chemotypes. To address the urgent need for new scaffolds, we recently reported the discovery and optimization of novel, potent isoxazole-based PfPKG inhibitors that lacked any obvious safety warnings. This manuscript presents representative in vitro ADME, hERG characterization and cell-based antiparasitic activity of these PfPKG inhibitors. We also report the discovery and structure-activity relationships of a new series with good potency, low hERG activity and cell-based anti-parasitic activity comparable to a literature standard.

P. falciparum cGMP-dependent protein kinase (PfPKG) is an enticing anti-malarial drug target. Structurally novel isoxazole-based compounds were shown to be ATP competitive inhibitors of PfPKG. Isoxazoles 3 and 5 had Ki values of 0.7 ± 0.2 and 2.3 ± 0.9 nM, respectively, that are comparable to a known standard, 4-[2-(4-fluorophenyl)-5-(1-methylpiperidine-4-yl)-1H pyrrol-3-yl] pyridine (1.4 ± 0.5 nM). They also exhibited excellent selectivity for PfPKG over the human ortholog and the gatekeeper mutant T618Q PfPKG, which mimics the less accessible binding site of the human ortholog. The human ortholog’s larger binding site volume was predicted to explain the selectivity of the inhibitors for the P. falciparum enzyme. Analogs 4 and 6 were at least 20-fold less potent compared to 3 and 5, suggesting that removing the carbonyl group in 3 or altering the diethylamino moiety in 5 reduced affinity.

The primary effector of cGMP signaling in Plasmodium is the cGMP-dependent protein kinase (PKG). Work in human-infective Plasmodium falciparum and rodent-infective Plasmodium berghei has provided biological validation of P. falciparum PKG (PfPKG) as a drug target for treating and/or protecting against malaria. PfPKG is essential in the asexual erythrocytic and sexual cycles as well as the pre-erythrocytic cycle. Medicinal chemistry efforts, both target-based and phenotype-based, have targeted PfPKG in the past few years. This review provides a brief overview of their results and challenges.

In recent years, understanding ways to improve the value and impact of heterocycles, in drug discovery and medicinal chemistry has increased with understanding of the multitude ways this fragment can influence properties. This chapter defines heterocycles as aromatic and non-aromatic rings containing one or more non-carbon atoms. Accompanying this is an expansion of the routes for synthesis that can be applied generally and more specifically to individual examples to efficiently deliver key building blocks used in drug discovery. This chapter will highlight recent examples of applications of heterocycles to favorably improve drug candidates in a range of therapeutic areas. In addition, synthetic methodology to access these heterocycles, including a discussion of late stage functionalization as a means to create new molecules will be presented.

The cGMP-dependent protein kinase in Plasmodium falciparum (PfPKG) plays multiple roles in the life cycle of the parasite. As a result, this enzyme is a potential target for new antimalarial agents. Existing inhbitors, while potent and active in malaria models are not optimal. This communication describes initial optimization of a structurally distinct class of PfPKG inhibitors.

[Image: see text] Lymphatic filariasis infects over 120 million people worldwide and can lead to significant disfigurement and disease. Resistance is emerging with current treatments, and these therapies have dose limiting adverse events; consequently new targets are needed. One approach to achieve this goal is inhibition of parasitic protein kinases involved in circumventing host defense mechanisms. This report describes structure–activity relationships leading to the identification of a potent, orally bioavailable stress activated protein kinase inhibitor that may be used to investigate this hypothesis.

Conformational restriction is a useful approach for ligand design in organic and medicinal chemistry. This manuscript reports the facile synthesis and in silico conformational analysis of two new diastereomeric [3.2.2]-3-azabicyclic, two new [3.2.1]-3-aza-8-oxy-bicyclic and one new [3.2.1]-3-azabicyclic diamine scaffolds. A conformational analysis of these structures along with calculation of carbon–carbon/carbon–nitrogen bond angles was carried out and compared to those in the flexible 1,3-diaminopropane template upon which they were based. It is of particular importance that these scaffolds have bond lengths and angles that can overlap with low energy conformers of the flexible diamine. Such information is useful for ligand design in organic chemistry and for development of structure activity relationships and in silico screening in medicinal chemistry.

Filariasis is a tropical disease caused by the parasitic nematodes Wuchereria bancrofti and Brugia malayi. Known inhibitors of dihydrofolate reductase (DHFR) have been previously shown to kill Brugia malayi nematodes and to inhibit Brugia malayi DHFR (BmDHFR) at nanomolar concentrations. These data suggest that BmDHFR is a potential target for the treatment of filariasis. Here, protocols for cloning, expression and purification of Wuchereria bancrofti DHFR (WbDHFR) were developed. The Uniprot entry J9F199-1 predicts a 172 amino acid protein for WbDHFR but alignment of this sequence to the previously described BmDHFR shows that this WbDHFR sequence lacks a crucial, conserved 13 amino acid loop. The presence of the loop in WbDHFR is supported by a noncanonical splicing event and the loop sequence was therefore included in the gene design. Subsequently, the KM for dihydrofolate (3.7 ± 2 μM), kcat (7.4 ± 0.6 s-1), and pH dependence of activity were determined. IC50 values of methotrexate, trimethoprim, pyrimethamine, raltitrexed, aminopterin, (-)-epicatechin gallate, (-)-epicatechin, and vitexin were measured for WbDHFR and BmDHFR. Methotrexate and structurally related aminopterin were found to be effective inhibitors of WbDHFR, with an KI of 1.2 ± 0.2 nM and 2.1 ± 0.5 nM, respectively, suggesting that repurposing of known antifolate compound may be an effective strategy to treating filariasis. Most compounds showed similar inhibition profiles toward both enzymes, suggesting that the two enzymes have important similarities in their active site environments and can be targeted with the same compound, once a successful inhibitor is identified.

The discovery and clinical development of heat shock protein 90 (Hsp90) inhibitors continue to progress. A number of Hsp90 inhibitors are in clinical trials, and preclinical discoveries of new chemotypes that bind to distinct regions in the protein as well as isoform selective compounds are active areas of research. This review will highlight progress in the field since 2010.

Quinolinol-based compounds are a promising starting point for discovery of effective inhibitors of the clostridial neurotoxin, botulinum neurotoxin type A light chain (BoNT/A LC). Insights into the mechanism of inhibition by quinolinol compounds facilitate interpretation of docking data and inhibitor optimization. In this study, a fluorogenic substrate of BoNT/A, SNAPtide, was used to study the mechanism by which two new quinolinol compounds, MSU58 and MSU84, with IC50 values of 3.3 μM and 5.8 μM, respectively, inhibit BoNT/A LC. Kinetic studies and model discrimination analysis showed both compounds to be competitive inhibitors of BoNT/A LC with inhibition constants (KI) 3.2 μM and 6.2 μM for MSU58 and MSU84, respectively. These data indicate that the inhibitors bind in the BoNT/A LC active site and that inhibitor binding is mutually exclusive with the binding of the substrate. This is the first study to report the competitive inhibition of BoNT/A LC by quinolinol compounds. These data help define the inhibitor binding pocket and, along with structure activity relationship studies, provide immediate direction for further compound synthesis.

Protein kinases are becoming widely investigated targets for treatment of protozoal parasitic tropical diseases such as malaria and leishmaniasis. The search for potent, selective inhibitors of these parasitic enzymes has been aided by the extensive variety of structures prepared for human diseases. Genomic approaches to target identification and validation have aided the search. Substantial progress has been made and research is continuing to expand in an effort to find safe, effective drug candidates for these difficult to treat and widespread diseases.

Small molecules remain the backbone for modern drug discovery. They are conceived and synthesized by medicinal chemists, many of whom were originally trained as organic chemists. Support from government and industry to provide training and personnel for continued development of this critical skill set has been declining for many years. This Viewpoint highlights the value of organic chemistry and organic medicinal chemists in the complex journey of drug discovery as a reminder that basic science support must be restored.

Drug discovery for non-life-threatening disorders is an active area of medicinal chemistry research. This chapter will describe the discovery and properties of phosphodiesterase 5 inhibitors for erectile dysfunction, the medicinal chemistry of agents for treatment of insomnia, and smoking cessation. Keywords: insomnia; phosphodiesterase 5 inhibitors; smoking cessation

The synthesis and structure–activity relationships of novel dipeptidyl peptidase IV inhibitors replacing the classical cyanopyrrolidine P1 group with other small nitrogen heterocycles are described. A unique potency enhancement was achieved with β-branched natural and unnatural amino acids, particularly adamantylglycines, linked to a (2S,3R)-2,3-methanopyrrolidine based scaffold.

Phosphodiesterase enzymes convert cyclic GMP and cyclic AMP to the corresponding nucleotide monophosphates. Phosphodiesterase 5 (PDE5) inhibition is now a widely accepted and efficacious therapeutic option for the treatment of erectile dysfunction in men, as a result of extensive clinical experience with sildenafil and other new PDE5 inhibitors. Research in the field continues at a substantial level to identify new, selective PDE5 inhibitors and to investigate their usefulness and activity in other areas. This review summarizes recent clinical trials with PDE5 inhibitors, advances in medicinal chemistry, and other activities and potential applications of this class of compounds.

International audience; Preventing viral entry into cells is a recognized approach for HIV therapy and has attracted attention for use against the hepatitis C virus (HCV). Recent reports described the activity of (−)-epigallocatechin gallate (EGCG) as an inhibitor of HCV entry with modest potency. EGCG is a polyphenolic natural product with a wide range of biological activity and unfavorable pharmaceutical properties. In an attempt to identify more drug-like EGCG derivatives with improved efficacy as HCV entry inhibitors, we initiated structure–activity investigations using semi-synthetic and synthetic EGCG analogs. The data show that there are multiple regions in the EGCG structure that contribute to activity. The gallate ester portion of the molecule appears to be of particular importance as a 3,4-difluoro analog of EGCG enhanced potency. This derivative and other active compounds were shown not to be cytotoxic in Huh-7 cell culture. These data suggest that more potent, non-cytotoxic EGCG analogs can be prepared in an attempt to identify more drug-like candidates to treat HCV infection by this mechanism.

Summary: This application claims a series of indoles as molecules that inhibit tau phosphorylation. This approach to neurodegenerative disease is of interest because of the hypothesized role for tau in neuronal cell death. Tau is an intracellular protein that stabilizes microtubules and helps regulate their function, for example in cell division. Test compounds were studied for their ability to inhibit tau phosphorylation or inhibit α-synuclein in animals and in cell culture.

(-)-Epigallocatechin gallate (EGCG) is the major flavonoid of green tea and has been widely explored for a range of biological activities including anti-infective, anti-inflammatory, anti-cancer, and neuroprotection. Existing structure-activity data for EGCG has been largely limited to exploration of simple ethers and hydroxyl deletion. EGCG has poor drug-like properties because of multiple phenolic hydroxyl moieties and a metabolically labile ester. This work reports a substantial expansion of structure-activity understanding by exploring a range of semi-synthetic and synthetic derivatives with ester replacements and variously substituted aromatic and alicyclic groups containing more drug-like substituents. Structure-activity relationships for these molecules were obtained for Hsp90 inhibition. The results indicate that amide and sulfonamide linkers are suitable ester replacements. Hydroxylated aromatic rings and the cis-stereochemistry in EGCG are not essential for Hsp90 inhibition. Selected analogs in this series are more potent than EGCG in a luciferase refolding assay for Hsp90 activity.

Phosphodiesterase type 5 (PDE5) inhibitors with improved PDE isozyme selectivity relative to sildenafil may result in agents for the treatment of male erectile dysfunction (MED) with a lower incidence of PDE-associated adverse effects. This paper describes the discovery of 14, a PDE5 inhibitor with improved potency and selectivity in vitro compared to sildenafil. This compound shows activity in a functional assay of erectile function comparable to that of sildenafil.

A series of 3,9 disubstituted [(alkylthio)methyl]- and (alkoxymethyl)-K-252a derivatives was synthesized with the aim of enhancing and separating the neurotrophic properties from the undesirable NGF (trk A kinase) and PKC inhibitory activities of K-252a. Data from this series reveal that substitution in the 3- and 9-positions of K-252a with these groups reduces trk A kinase inhibitory properties approximately 100- to500-fold while maintaining or in certain cases enhancing the neurotrophic activity. From this research, 3,9-bis[(ethylthio)methyl]-K-252a (8) was identified as a potent and selective neurotrophic agent in vitro as measured by enhancement of choline acetyltransferase activity in embryonic rat spinal cord and basal forebrain cultures. Compound 8 was found to have weak kinase inhibitory activity for trk A, protein kinase C1 protein kinase A, and myosin light chain kinase. On the basis of the in vitro profile, 8 was evaluated in in vivo models suggestive of neurological diseases. Compound 8 was active in preventing degeneration of cholinergic neurons of the nucleus basalis magnocellularis (NBM) and reduced developmentally programmed cell death (PCD) of female rat spinal nucleus of the bulbocavernosus motoneurons and embryonic chick lumbar motoneurons.

Boceprevir was the first direct acting agent developed for the treatment of hepatitis C virus infection. Boceprevir functions by targeting NS3 protease, a viral enzyme essential for replication. This peptidomimetic molecule was optimized from a peptide lead to provide a potent, selective and orally bioavailable drug that can be combined with ribavirin and peg interferon to achieve sustained viral response (undetectable HCV RNA levels for 24 weeks after completion of therapy) in patients infected with Genotype 1 of the virus.This article provides a review of the pre-clinical and clinical discovery of boceprevir. This review includes the role and function of its molecular target, NS3 protease, as well as the assays used to measure in vitro efficacy, compound optimization and clinical studies to demonstrate safety and efficacy.As the first direct acting anti-HCV agent, boceprevir represents an important advance in therapy of this widespread chronic disease. Yet, while this therapy is a valuable approach, it does have limitations. Studies have suggested that 30% of patients do not achieve sustained viral response and 11% of patients have developed anemia and/or neutropenia. Current drug discovery and development efforts are underway to develop novel therapeutic options that address these issues.

Notes The authors declare no competing financial interest. Title: Gamma Secretase Modulators Application Number: WO 2013066740A1 Publication date: 10 May 2013 Priority Application: 61/553,384 Priority date: 31 October 2011 Inventors: W. Greenlee, D. Pissarnitski, Z. Zhao, Z. Zhu Assignee Company: Merck Sharpe & Dohme Disease Area: Neurodegeneration Biological Target: Gamma secretase Summary: Gamma secretase is an aspartic protease complex involved in the biosynthesis of Aβ peptide, a potential neurotoxic contributor in the progression of Alzheimer’s disease. Direct inhibition of enzymatic activity introduces potential selectivity issues associated with other biological functions of gamma secretase including Notch and Eph processing. As an alternative approach to gamma secretase inhibition, modulation of enzyme activity using, e.g., NSAIDs is a potentially druggable concept. This patent describes the synthesis and evaluation of a novel chemical series that demonstrates inhibition of gamma secretase activity in vitro and reduction of Aβ42 CSF levels following oral administration of a standard dose of 30 mg/kg. Primary Markush

Since the discovery of haloperidol in the 1950s, monoaminergic receptors have provided a number of potential targets for treatment of schizophrenia. This chapter will survey the profiles of existing dopaminergic-based antipsychotic drugs and review recent medicinal chemistry approaches that engage other monoaminergic receptors to discover novel agents for treatment of schizophrenia. In addition to single-target approaches, attempts to discover molecules that interact selectively (i.e. designed to bind) with more than a single receptor to provide effective antipsychotic agents will be reviewed. These efforts highlight attempts to address unmet needs with existing therapy, including efficacy in a broader range of patients of this complex and debilitating disease.

Pyrrolo[3,4-c]carbazole derivatives were prepared as potential neurotrophic agents. The compounds were assayed for their ability to stimulate choline acetyltransferase (ChAT) activity in embryonic rat spinal cord cultures. These simplified K252a derivatives, although less potent and efficacious, have led to the identification of minimal structural requirements for K252a neurotrophic activity.

Ophiobolin A [1], 3-anhydroophiobolin A [2], ophiobolin B [3], and ophiobolin L [4] were isolated from fermentation broths of Cochliobolus heterostrophus. Preliminary screening showed that a number of organisms were capable of metabolizing the sesterterpene ophiobolin A [1]. Large-scale transformations of ophiobolin A [1] with Polyangium cellulosum produced 6 and 7 while Pseudomonas aeruginosa produced 8. Resting-cell preparations of Penicillium patulum afforded 9 and 10. The structures of these metabolites were established by spectroscopic methods and by comparison of the spectral data with those of the starting material. The antimicrobial activity of the ophiobolins was also evaluated.

The first synthesis of stereospecific 3,4,5-trisubstituted γ-butyrolactone phospholipids has been achieved by a ten-step sequence starting fromN,N-dimethylacetamide (9). Alkylation of 9 with 1-bromohexane gaveN,N-dimethyloctanamide (11), which was subjected to aldol condensation with acrolein and afforded theerythro-N,N-dimethyl-3-hydroxy-2-hexyl-4-pentenamide (6) and itsthreo isomer 7, both of which were subsequently converted to the corresponding 3-oxy(hexanoyl) esters 15 and 16. Stereospecific cyclization of diastereomeric allylic amides (6,7,15 and 16)via iodolactonization gave 3,4,5-trisubstituted γ-butyrolactones (19–25) in satisfactory yields (68–89%) and with high stereoselectivity (at least 6∶1), except for thethreo amide 16 (2∶1). Conversion of the 6-iodo-group of the major iodolactones 23 and 24 to the corresponding 6-hydroxy lactones 31 and 32 through a wet Prevost reaction also resulted in 4-hydroxy lactones 30 and 33, and a mechanism for this reaction is proposed. Further phosphorylation of 4- or 6-hydroxy lactones 30, 31 and 32 with diphenyl chlorophosphate gave the corresponding diphenyl phosphoric acid lactone esters 34, 35 and 36, whereas 33 underwent an elimination reaction under formation of a C(3)−C(4) double bond. Hydrogenolysis of the diphenyl groups of esters 34, 35 and 36 over Adams' catalyst [platinum(IV) oxide] yielded the corresponding phosphoric acid lactone esters 38, 39 and 40, which were finally treated with choline tetraphenylborate to afford the desired lactone phospholipids 41, 42 and 43 in overall yields of 9, 30 and 18%, respectively. The structures of all new compounds were unambiguously assigned by analysis of their1H and13C one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectra obtained on a 300 MHz NMR spectrometer, and the structures were confirmed by low or high resolution mass spectrometry as well as elemental analysis. The stereoisomeric purity of the final products (98.2, 99.0 and 98.5% for 41, 42 and 43, respectively) was determined by high-performance liquid chromatography.

A series of α-mono and dialkyl-β-oxygenated (hydroxyl and alkyl ester) tertiary amides were subjected to iodolactonization and it was observed that with only 1 exception, (threo 11b), all of the compounds cyclized with useful levels of stereoselection (at least 3:1). While the origin of this effect is obscure, these results suggest that in such amide substrates with at least one substituent larger than methyl α to the amide, iodolactonization is a viable strategy for the stereocontrolled preparation of highly substituted γ-butyrolactones