Substituted 4-(2,2-diphenylethyl)pyridine-N-oxides as phosphodiesterase-4 inhibitors: SAR study directed toward the improvement of pharmacokinetic parameters

Structure dependence of intramolecular electron transfer reactions of simple dyads of a zinc(ii) porphyrin complex bearing a peripheral bipyridine moiety

Photoinduced intramolecular electron transfer and charge recombination reactions were investigated using various Zn(ii)-porphyrin dyads having a 2,2′-bipyridine moiety.

Nonracemic synthesis of GK-GKRP disruptor AMG-3969

A nonracemic synthesis of the glucokinase-glucokinase regulatory protein disruptor AMG-3969 (5) is reported. Key features of the synthetic approach are an asymmetric synthesis of the 2-alkynyl piperazine core via a base-promoted isomerization and a revised approach to the synthesis of the aminopyridinesulfonamide with an improved safety profile.

Small molecule disruptors of the glucokinase-glucokinase regulatory protein interaction: 2. Leveraging structure-based drug design to identify analogues with improved pharmacokinetic profiles

In the previous report , we described the discovery and optimization of novel small molecule disruptors of the GK-GKRP interaction culminating in the identification of 1 (AMG-1694). Although this analogue possessed excellent in vitro potency and was a useful tool compound in initial proof-of-concept experiments, high metabolic turnover limited its advancement. Guided by a combination of metabolite identification and structure-based design, we have successfully discovered a potent and metabolically stable GK-GKRP disruptor (27, AMG-3969). When administered to db/db mice, this compound demonstrated a robust pharmacodynamic response (GK translocation) as well as statistically significant dose-dependent reductions in fed blood glucose levels.

Small molecule disruptors of the glucokinase-glucokinase regulatory protein interaction: 1. Discovery of a novel tool compound for in vivo proof-of-concept

Small molecule activators of glucokinase have shown robust efficacy in both preclinical models and humans. However, overactivation of glucokinase (GK) can cause excessive glucose turnover, leading to hypoglycemia. To circumvent this adverse side effect, we chose to modulate GK activity by targeting the endogenous inhibitor of GK, glucokinase regulatory protein (GKRP). Disrupting the GK-GKRP complex results in an increase in the amount of unbound cytosolic GK without altering the inherent kinetics of the enzyme. Herein we report the identification of compounds that efficiently disrupt the GK-GKRP interaction via a previously unknown binding pocket. Using a structure-based approach, the potency of the initial hit was improved to provide 25 (AMG-1694). When dosed in ZDF rats, 25 showed both a robust pharmacodynamic effect as well as a statistically significant reduction in glucose. Additionally, hypoglycemia was not observed in either the hyperglycemic or normal rats.

Antidiabetic effects of glucokinase regulatory protein small-molecule disruptors

Glucose homeostasis is a vital and complex process, and its disruption can cause hyperglycaemia and type II diabetes mellitus. Glucokinase (GK), a key enzyme that regulates glucose homeostasis, converts glucose to glucose-6-phosphate in pancreatic β-cells, liver hepatocytes, specific hypothalamic neurons, and gut enterocytes. In hepatocytes, GK regulates glucose uptake and glycogen synthesis, suppresses glucose production, and is subject to the endogenous inhibitor GK regulatory protein (GKRP). During fasting, GKRP binds, inactivates and sequesters GK in the nucleus, which removes GK from the gluconeogenic process and prevents a futile cycle of glucose phosphorylation. Compounds that directly hyperactivate GK (GK activators) lower blood glucose levels and are being evaluated clinically as potential therapeutics for the treatment of type II diabetes mellitus. However, initial reports indicate that an increased risk of hypoglycaemia is associated with some GK activators. To mitigate the risk of hypoglycaemia, we sought to increase GK activity by blocking GKRP. Here we describe the identification of two potent small-molecule GK-GKRP disruptors (AMG-1694 and AMG-3969) that normalized blood glucose levels in several rodent models of diabetes. These compounds potently reversed the inhibitory effect of GKRP on GK activity and promoted GK translocation both in vitro (isolated hepatocytes) and in vivo (liver). A co-crystal structure of full-length human GKRP in complex with AMG-1694 revealed a previously unknown binding pocket in GKRP distinct from that of the phosphofructose-binding site. Furthermore, with AMG-1694 and AMG-3969 (but not GK activators), blood glucose lowering was restricted to diabetic and not normoglycaemic animals. These findings exploit a new cellular mechanism for lowering blood glucose levels with reduced potential for hypoglycaemic risk in patients with type II diabetes mellitus.

Synthesis of azafluorenone antimicrobial agents

A flexible synthesis of the azafluorenone alkaloids 1, 2, 3, and 4 is described.

Peripheral phosphodiesterase 4 inhibition produced by 4-[2-(3,4-Bis-difluoromethoxyphenyl)-2-[4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-phenyl]-ethyl]-3-methylpyridine-1-oxide (L-826,141) prevents experimental autoimmune encephalomyelitis

Administration of phosphodiesterase 4 (PDE4) inhibitors suppresses the pathogenesis associated with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). In the present study, we compared the effects of rolipram and 4-[2-(3,4-bis-difluoromethoxyphenyl)-2-[4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-phenyl]-ethyl]-3-methylpyridine-1-oxide (L-826,141), a novel nonbrain penetrant PDE4 inhibitor, on the onset and severity of clinical signs in a chronic, nonrelapsing/remitting model of EAE. Both rolipram (10 mg/kg p.o.) and L-826,141 (3 mg/kg p.o.) reduced the severity of EAE relative to controls, whereas L-826,141 (3 mg/kg p.o.) also delayed disease onset. To assess whether L-826,141 prevented EAE progression after the first signs of clinical onset, rolipram (10 mg/kg p.o.) or L-826,141 (3 or 30 mg/kg p.o.) were administered 24 h after the first signs of EAE were observed. Only L-826,141 at a dose of 30 mg/kg p.o. significantly decreased the clinical severity of EAE compared with vehicle controls. Immunohistochemical detection of the neuronal activity marker Fos confirmed that L-826,141 did not reach concentrations in the central nervous system sufficient to activate central neurons. Lipopolysaccharide-induced tumor necrosis factor-alpha in whole blood and plasma concentrations of L-826,141 revealed that only the 30-mg/kg dose resulted in levels sufficient to produce a near complete inhibition of PDE4 activity in immune cells. Taken together, these results demonstrate that peripheral PDE4 inhibition, produced by L-826,141, prevents the progression of EAE after the first onset of clinical signs, and suggest that similar compounds may have clinical efficacy in the treatment of MS.

Enantiomer discrimination illustrated by the high resolution crystal structures of type 4 phosphodiesterase

Type 4 phosphodiesterase (PDE4) inhibitors are emerging as new treatments for a number of disorders including asthma and chronic obstructive pulmonary disease. Here we report the biochemical characterization on the second generation inhibitor (+)-1 (L-, IC50=0.4 nM) and its enantiomer (-)-1 (L-, IC50=43 nM) and their cocrystal structures with PDE4D at 2.0 A resolution. Despite the 107-fold affinity difference, both enantiomers interact with the same sets of residues in the rigid active site. The weaker (-)-1 adopts an unfavorable conformation to preserve the pivotal interactions between the Mg-bound waters and the N-oxide of pyridine. These structures support a model in which inhibitors are anchored by the invariant glutamine at one end and the metal-pocket residues at another end. This model provides explanations for most of the observed structure-activity relationship and the metal ion dependency of the catechol-ether based inhibitors and should facilitate their further design.

Practical Asymmetric Synthesis of a Potent PDE4 Inhibitor via Stereoselective Enolate Alkylation of a Chiral Aryl−Heteroaryl Secondary Tosylate

A practical, chromatography-free catalytic asymmetric synthesis of a potent and selective PDE4 inhibitor (L-869,298, 1) is described. Catalytic asymmetric hydrogenation of thiazole ketone 5a afforded the corresponding alcohol 3b in excellent enantioselectivity (up to 99.4% ee). Activation of alcohol 3b via formation of the corresponding p-toluenesulfonate followed by an unprecedented displacement with the lithium enolate of ethyl 3-pyridylacetate N-oxide 4a generated the required chiral trisubstituted methane. The displacement reaction proceeded with inversion of configuration and without loss of optical purity. Conversion of esters 2b to 1 was accomplished via a one-pot deprotection, saponification, and decarboxylation sequence in excellent overall yield.

Simultaneously quantifying parent drugs and screening for metabolites in plasma pharmacokinetic samples using selected reaction monitoring information-dependent acquisition on a QTrap instrument

Bioanalytical support of plasma pharmacokinetic (PK) studies for drug discovery programs primarily involves the quantitative analysis of dosed compounds using liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) operated in selected reaction monitoring (SRM) mode. However, there is a growing need for information on the metabolism of new chemical entities (NCEs), in addition to the time-concentration profiles from these studies. In this paper, we present a novel approach to not only quantify parent drugs with SRM, but also simultaneously screen for metabolites using a hybrid triple quadrupole/linear ion trap (QqQ(LIT)) instrument. This was achieved by incorporating both the conventional SRM-only acquisition of parent compounds and the SRM-triggered information-dependent acquisition (IDA) of potential metabolites within the same scan cycle during the same LC/MS/MS run. Two test compounds were used to demonstrate the applicability of this approach. Plasma samples from PK studies were processed by simple protein precipitation and the supernatant was diluted with water before injection. The fast scanning capability of the linear ion trap allowed for the information-dependent acquisition of metabolite MS/MS spectra (<1 s/scan), in addition to the collection of adequate data points for SRM-only channels. The MS/MS spectra obtained from potential metabolites in post-dose samples correlated well with the spectra of the parent compounds studied, therefore providing additional confirmatory structure information without the need for repetitive analyses. Relative quantitative time-concentration profiles of identified metabolites were also obtained. Furthermore, this articulated SRM+SRM-IDA approach generated equivalent quantitative results for parent compounds to those obtained by conventional SRM-only analysis. This approach has been successfully used to support discovery PK screening programs.

Nucleophilic displacement at benzhydryl centers: asymmetric synthesis of 1,1-diarylalkyl derivatives

[reaction: see text] Activation of substituted 1,1-diarylmethanols as their corresponding toluenesulfonates and subsequent displacement with a range of carbon, nitrogen, oxygen, and sulfur nucleophiles proceeds in 81-96% yield. Enantiomerically enriched diarylmethanols 8a-c were activated and displaced with pyridine acetate enolate with complete stereochemical inversion at carbon to yield 1,1-diarylalkyl derivatives 10a-c without loss of optical purity.

Optimization of a tertiary alcohol series of phosphodiesterase-4 (PDE4) inhibitors: structure-activity relationship related to PDE4 inhibition and human ether-a-go-go related gene potassium channel binding affinity

A SAR study on the tertiary alcohol series of phosphodiesterase-4 (PDE4) inhibitors related to 1 is described. In addition to inhibitory potency against PDE4 and the lipopolysaccharide-induced production of TNFalpha in human whole blood, the binding affinity of these compounds for the human ether-a-go-go related gene (hERG) potassium channel (an in vitro measure for the potential to cause QTc prolongation) was assessed. Four key structural moieties in the molecule were studied, and the impact of the resulting modifications in modulating these activities was evaluated. From these studies, (+)-3d (L-869,298) was identified as an optimized structure with respect to PDE4 inhibitory potency, lack of binding affinity to the hERG potassium channel, and pharmacokinetic behavior. (+)-3d exhibited good in vivo efficacy in several models of pulmonary function with a wide therapeutic index with respect to emesis and prolongation of the QTc interval.

Substituted 2-pyridinemethanol derivatives as potent and selective phosphodiesterase-4 inhibitors

The synthesis and the phosphodiesterase-4 (PDE4) inhibitory activity of 2-pyridinemethanol derivatives is described. The evaluation of the structure-activity relationship (SAR) in this series of novel PDE4 inhibitors led to the identification of compound 9 which exhibits excellent in vitro activity, desirable pharmacokinetic parameters and good efficacy in animal models of bronchoconstriction.

Substituted aminopyridines as potent and selective phosphodiesterase-4 inhibitors

The synthesis and the biological evaluation of new potent phosphodiesterase type 4 (PDE4) inhibitors are presented. This new series was elaborated by replacement of the metabolically resistant phenyl hexafluorocarbinol of L-791,943 (1) by a substituted aminopyridine residue. The structure-activity relationship of N-substitution on 3 led to the identification of (-)-3n which exhibited a good PDE4 inhibitor activity (HWB-TNFalpha=0.12 microM) and an improved pharmacokinetic profile over L-791,943 (rat t(1/2)=2 h). (-)-3n was well tolerated in ferret with an emetic threshold of 30 mg/kg (po) and was found to be active in the ovalbumin-induced bronchoconstriction model in guinea pig (54%, 0.1 mg/kg, ip) as well as the ascaris-induced bronchoconstriction model in sheep (64%/97%, early/late, 0.5 mg/kg, iv).