WAY-318068: a novel, potent and selective noradrenaline re-uptake inhibitor with activity in rodent models of pain and depression.

BACKGROUND AND PURPOSE: Antidepressants, which raise the CNS concentrations of 5-HT and noradrenaline, are frequently used in the treatment of chronic pain; however, it is not known if increasing CNS noradrenaline levels alone is sufficient for efficacy, in part resulting from a lack of small molecules with sufficient selectivity. EXPERIMENTAL APPROACH: In this report, we present the in vitro pharmacological and in vivo pharmacokinetic and pharmacological properties of the novel, orally available and CNS penetrant inhibitor of the noradrenaline transporter (NET), WAY-318068 (1-[(1S,2R)-1-(3,5-difluorophenyl)-2-hydroxy-3-(methylamino)propyl]-7-fluoro-3,3-dimethyl-1,3-dihydro-2H-indol-2-one). KEY RESULTS: WAY-318068 is a potent and effective inhibitor of the NET with a K(i) of 8.7 nM in a binding assay, and an IC(50) of 6.8 nM in an assay of transporter function, without significant binding to the dopamine transporter. Furthermore, the compound has only weak activity at the 5-HT transporter, leading to a functional selectivity of greater than 2500-fold. It is orally bioavailable with substantial quantities of the compound found in the CNS after oral dosing. As measured by microdialysis in rats, the compound causes a robust and significant increase in cortical noradrenaline levels without affecting 5-HT. WAY-318068 was effective in models of acute, visceral, inflammatory, osteoarthritic, neuropathic, diabetic and bone cancer pain, as well as in traditional models of depression at doses that do not cause motor deficits. CONCLUSIONS AND IMPLICATIONS: Collectively, the present results support the conclusion that selectively increasing CNS levels of noradrenaline is sufficient for efficacy in models of depression and pain.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and pain.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels underlie the pacemaker currents in neurons and cardiac cells designated as I(h) and I(f), respectively. HCN channels are activated at negative membrane potentials and specifically upon repolarization following action potential firing resulting in a depolarizing current influencing the threshold for subsequent action potential generation. Consequently, HCN channels and I(h)/I(f) play a critical role in regulating excitability and rhythmic activity in excitable cells. The distribution of the four HCN channel subtypes has been studied in some detail in sensory neurons demonstrating a diverse and widespread distribution and raising the question as to their potential involvement in pain pathophysiology, frequently ascribed to aberrant neuronal hyperexcitability. This review discusses the evidence implicating a role for HCN channels in pain.

Species-specific in vitro pharmacological effects of the cannabinoid receptor 2 (CB2) selective ligand AM1241 and its resolved enantiomers.

BACKGROUND AND PURPOSE: Racemic (R,S) AM1241 is a cannabinoid receptor 2 (CB(2))-selective aminoalkylindole with antinociceptive efficacy in animal pain models. The purpose of our studies was to provide a characterization of R,S-AM1241 and its resolved enantiomers in vitro and in vivo. EXPERIMENTAL APPROACH: Competition binding assays were performed using membranes from cell lines expressing recombinant human, rat, and mouse CB(2) receptors. Inhibition of cAMP was assayed using intact CB(2)-expressing cells. A mouse model of visceral pain (para-phenylquinone, PPQ) and a rat model of acute inflammatory pain (carrageenan) were employed to characterize the compounds in vivo. KEY RESULTS: In cAMP inhibition assays, R,S-AM1241 was found to be an agonist at human CB(2), but an inverse agonist at rat and mouse CB(2) receptors. R-AM1241 bound with more than 40-fold higher affinity than S-AM1241, to all three CB(2) receptors and displayed a functional profile similar to that of the racemate. In contrast, S-AM1241 was an agonist at all three CB(2) receptors. In pain models, S-AM1241 was more efficacious than either R-AM1241 or the racemate. Antagonist blockade demonstrated that the in vivo effects of S-AM1241 were mediated by CB(2) receptors. CONCLUSIONS AND IMPLICATIONS: These findings constitute the first in vitro functional assessment of R,S-AM1241 at rodent CB(2) receptors and the first characterization of the AM1241 enantiomers in recombinant cell systems and in vivo. The greater antinociceptive efficacy of S-AM1241, the functional CB(2) agonist enantiomer of AM1241, is consistent with previous observations that CB(2) agonists are effective in relief of pain.

Acetylenic TACE inhibitors. Part 3: Thiomorpholine sulfonamide hydroxamates.

A series of thiomorpholine sulfonamide hydroxamate TACE inhibitors, all bearing propargylic ether P1' groups, was explored. In particular, compound 5h has excellent in vitro potency against isolated TACE enzyme and in cells, oral activity in a model of TNF-alpha production and a collagen-induced arthritis model, was selected as a clinical candidate for the treatment of RA.

Acetylenic TACE inhibitors. Part 1. SAR of the acyclic sulfonamide hydroxamates.

The SAR of a series of potent sulfonamide hydroxamate TACE inhibitors, all bearing a butynyloxy P1' group, was explored. In particular, compound 5j has excellent in vitro potency against isolated TACE enzyme and in cells, good selectivity over MMP-1 and MMP-9, and oral activity in an in vivo model of TNF-alpha production and a collagen-induced arthritis model.