ABSTRACT:Apixaban is an oral, direct, and highly selective factor Xa inhibitor in late-stage clinical development for the prevention and treatment of thromboembolic diseases. The metabolic drug-drug interaction potential of apixaban was evaluated in vitro. The compound did not show cytochrome P450 inhibition (IC 50 values >20 M) in incubations of human liver microsomes with the probe substrates of CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4/5. Apixaban did not show any effect at concentrations up to 20 M on enzyme activities or mRNA levels of selected P450 enzymes (CYP1A2, 2B6, and 3A4/5) that are sensitive to induction in incubations with primary human hepatocytes. Apixaban showed a slow metabolic turnover in incubations of human liver microsomes with formation of O-demethylation (M2) and hydroxylation products (M4 and M7) as prominent in vitro metabolites. Experiments with human cDNA-expressed P450 enzymes and P450 chemical inhibitors and correlation with P450 activities in individual human liver microsomes demonstrated that the oxidative metabolism of apixaban for formation of all metabolites was predominantly catalyzed by CYP3A4/5 with a minor contribution of CYP1A2 and CYP2J2 for formation of M2. The contribution of CYP2C8, 2C9, and 2C19 to metabolism of apixaban was less significant. In addition, a human absorption, distribution, metabolism, and excretion study showed that more than half of the dose was excreted as unchanged parent (f m CYP <0.5), thus significantly reducing the overall metabolic drug-drug interaction potential of apixaban. Together with a low clinical efficacious concentration and multiple clearance pathways, these results demonstrate that the metabolic drug-drug interaction potential between apixaban and coadministered drugs is low.Apixaban (Fig. 1), a novel and highly selective inhibitor of factor Xa (Luettgen et al., 2006;Pinto et al., 2007;Wong et al., 2008), is under development for the treatment and prevention of thromboembolic disorders, prevention of stroke in patients with atrial fibrillation, and secondary prevention in patients with acute coronary syndromes (APPRAISE Steering Committee and Investigators, 2009). In addition to demonstrating high oral availability (Frost et al., 2007), clinical studies of apixiban have shown prevention of venous thromboembolic events in patients after knee replacement surgery (Lassen et al., 2007). Apixaban is efficacious and well tolerated in the treatment of patients with acute symptomatic deep vein thrombosis (Buller et al., 2008). After oral administration, apixaban was slowly metabolized and thus was mostly unchanged in the circulation although apixaban was metabolized by multiple pathways in animals and humans (Zhang et al., , 2010. The primary metabolic pathways of apixaban in humans included O-demethylation (M2) and hydroxylation (M4 and M7). M2 was further conjugated by sulfation to form a sulfate metabolite (M1) Wang et al., 2009). Other metabolites (M3, M5, and M6) previously identified as minor metabolites in animals and humans were als...

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Certain classes of neuroactive steroids (NASs) are positive allosteric modulators (PAM) of synaptic and extrasynaptic GABA receptors. Herein, we report new SAR insights in a series of 5β-nor-19-pregnan-20-one analogues bearing substituted pyrazoles and triazoles at C-21, culminating in the discovery of 3α-hydroxy-3β-methyl-21-(4-cyano-1H-pyrazol-1'-yl)-19-nor-5β-pregnan-20-one (SAGE-217, 3), a potent GABA receptor modulator at both synaptic and extrasynaptic receptor subtypes, with excellent oral DMPK properties. Compound 3 has completed a phase 1 single ascending dose (SAD) and multiple ascending dose (MAD) clinical trial and is currently being studied in parallel phase 2 clinical trials for the treatment of postpartum depression (PPD), major depressive disorder (MDD), and essential tremor (ET).

4-(1,3-Dimethoxyprop-2-ylamine)-2,7-dimethyl-8-(2,4-dichlorophenyl)-pyrazolo[1,5-a]-1,3,5-triazine (DMP696) is a highly selective and potent, nonpeptide corticotropin-releasing factor 1 (CRF 1 ) antagonist. In this study, we measured in vivo CRF 1 receptor occupancy of DMP696 by using ex vivo ligand binding and quantitative autoradiography and explored the relationship of receptor occupancy with plasma and brain exposure and behavioral efficacy. In vitro affinity (IC 50 ) of DMP696 to brain CRF 1 receptors measured using the brain section binding autoradiography in this study is similar to that assessed using homogenized cell membrane assays previously. The ex vivo binding assay was validated by demonstrating that potential underestimation of receptor occupancy with this procedure could be minimized by identifying an appropriate in vitro incubation time (40 min) based upon the dissociation kinetics of DMP696. Orally administrated DMP696 dose dependently occupied CRF 1 receptors in the brain, with ϳ60% occupancy at 3 mg/kg. In the defensive withdrawal test of anxiety, this dose of DMP696 produced approximately 50% reduction in the exit latency. The time course of plasma and brain drug levels paralleled that of receptor occupancy, with peak exposure at 90 min after dosing. The plasma-free concentration of DMP696 corresponding to 50% CRF 1 receptor occupancy (in vivo IC 50 , 1.22 nM) was similar to the in vitro IC 50 (ϳ1.0 nM). Brain concentrations of DMP696 were over 150-fold higher than the plasma-free levels. In conclusion, doses of DMP696 occupying over 50% brain CRF 1 receptors are consistent with doses producing anxiolytic efficacy in the defense withdrawal test of anxiety, and the IC 50 value estimated in vivo based on plasmafree drug concentrations is consistent with the in vitro IC 50 value.Corticotropin releasing factor (CRF), a 41-amino acid peptide, plays a pivotal role in the behavioral, endocrine, immune, and autonomic responses of the body to stress (Owens and Nemeroff, 1991). In addition to the hypothalamic paraventricular nucleus where it was originally identified, CRF is also widely distributed across brain regions (Chalmers et al., 1996;Heinrichs and De Souza, 1999;Gilligan et al., 2000a). The physiological functions of CRF are mediated by at least two G-protein coupled receptors, CRF 1 and CRF 2 (including splice variants CRF 2␣ , CRF 2␤ , CRF 2␥ ), both of which are linked to adenylyl cyclase activation but have distinct brain distributions. CRF 1 receptors are widespread in the cortex, limbic system, cerebellum, and pituitary, whereas CRF 2 receptors are dominant in subcortical areas including the lateral septum (CRF 2␣ ), ventromedial hypothalamus (CRF 2␣ ), and choroid plexus (CRF 2␤ ) (De Souza, 1987;Chalmers et al., 1995;Primus et al., 1997;Rominger et al., 1998).Increasing evidence suggests that the CRF system is involved in pathophysiology of anxiety disorders (Heinrichs and De Souza, 1999;Gilligan et al., 2000a). Intracerebroventricular administration of CRF induces stress beha...

ABSTRACT:The metabolism and disposition of [ 14 C]apixaban, a potent, reversible, and direct inhibitor of coagulation factor Xa, were investigated in mice, rats, rabbits, dogs, and humans after a single oral administration and in incubations with hepatocytes. In plasma, the parent compound was the major circulating component in mice,