Discovery of GSK2795039, a Novel Small Molecule NADPH Oxidase 2 Inhibitor.

AIMS: The NADPH oxidase (NOX) family of enzymes catalyzes the formation of reactive oxygen species (ROS). NOX enzymes not only have a key role in a variety of physiological processes but also contribute to oxidative stress in certain disease states. To date, while numerous small molecule inhibitors have been reported (in particular for NOX2), none have demonstrated inhibitory activity in vivo. As such, there is a need for the identification of improved NOX inhibitors to enable further evaluation of the biological functions of NOX enzymes in vivo as well as the therapeutic potential of NOX inhibition. In this study, both the in vitro and in vivo pharmacological profiles of GSK2795039, a novel NOX2 inhibitor, were characterized in comparison with other published NOX inhibitors. RESULTS: GSK2795039 inhibited both the formation of ROS and the utilization of the enzyme substrates, NADPH and oxygen, in a variety of semirecombinant cell-free and cell-based NOX2 assays. It inhibited NOX2 in an NADPH competitive manner and was selective over other NOX isoforms, xanthine oxidase, and endothelial nitric oxide synthase enzymes. Following systemic administration in mice, GSK2795039 abolished the production of ROS by activated NOX2 enzyme in a paw inflammation model. Furthermore, GSK2795039 showed activity in a murine model of acute pancreatitis, reducing the levels of serum amylase triggered by systemic injection of cerulein. INNOVATION AND CONCLUSIONS: GSK2795039 is a novel NOX2 inhibitor that is the first small molecule to demonstrate inhibition of the NOX2 enzyme in vivo.

In vivo 5-HT(6) receptor occupancy by antipsychotic drugs in the rat brain.

The 5-HT(6) receptor subtype is predominantly expressed in the central nervous system, and preclinical evidence suggests that it plays a critical role in the regulation of molecular pathways underlying cognitive function. Patients with schizophrenia show cognitive impairment as a fundamental symptom, and it is proposed that the procognitive properties of some antipsychotics such as olanzapine and clozapine would be, in part, due to the central blockade of 5-HT(6) receptors. In this study, we characterized the brain 5-HT(6) receptor occupancy of olanzapine, clozapine and chlorpromazine in relation to their pharmacokinetic profiles using in vivo [(3)H]GSK215083 binding assay in rat brain. Oral administration of olanzapine (3mg/kg), clozapine (30mg/kg) and chlorpromazine (30mg/kg) produced significant 5-HT(6) receptor occupancy in the brain, inhibiting radioligand binding by 88, 97 and 81%, respectively. The blood concentrations required to achieve significant occupancy were clinically achievable (9.6, 26.9 and 98.6nM for olanzapine, clozapine and chlorpromazine, respectively). This data provides preclinical evidence to support the hypothesis that brain 5-HT(6) antagonism contributes to the procognitive properties of antipsychotic drugs such as olanzapine and clozapine.