The vesicular monoamine transporter 2 (VMAT2) is an integral presynaptic protein that regulates the packaging and subsequent release of dopamine and other monoamines from neuronal vesicles into the synapse. Valbenazine (NBI-98854), a novel compound that selectively inhibits VMAT2, is approved for the treatment of tardive dyskinesia. Valbenazine is converted to two significant circulating metabolites in vivo, namely, (+)--dihydrotetrabenazine (R,R,R-HTBZ) and a mono-oxy metabolite, NBI-136110. Radioligand-binding studies were conducted to assess and compare valbenazine, tetrabenazine, and their respective metabolites in their abilities to selectively and potently inhibit [H]-HTBZ binding to VMAT2 in rat striatal, rat forebrain, and human platelet homogenates. A broad panel screen was conducted to evaluate possible off-target interactions of valbenazine, R,R,R-HTBZ, and NBI-136110 at >80 receptor, transporter, and ion channel sites. Radioligand binding showed R,R,R-HTBZ to be a potent VMAT2 inhibitor in homogenates of rat striatum (K = 1.0-2.8 nM), rat forebrain (K = 4.2 nM), and human platelets (K = 2.6-3.3 nM). Valbenazine (K = 110-190 nM) and NBI-136110 (K = 160-220 nM) also exhibited inhibitory effects on VMAT2, but with lower potency than R,R,R-HTBZ. Neither valbenazine, R,R,R-HTBZ, nor NBI-136110 had significant off-target interactions at serotonin (5-HT, 5-HT, 5-HT) or dopamine (D or D) receptor sites. In vivo studies measuring ptosis and prolactin secretion in the rat confirmed the specific and dose-dependent interactions of tetrabenazine and R,R,R-HTBZ with VMAT2. Evaluations of potency and selectivity of tetrabenazine and its pharmacologically active metabolites were also performed. Overall, the pharmacologic characteristics of valbenazine appear consistent with the favorable efficacy and tolerability findings of recent clinical studies [KINECT 2 (NCT01733121), KINECT 3 (NCT02274558)].

Oral administration of a nonpeptide GnRH antagonist, elagolix, suppressed the reproductive endocrine axis in healthy premenopausal women. These results suggest that elagolix may enable dose-related pituitary and gonadal suppression in premenopausal women as part of treatment strategies for reproductive hormone-dependent disease states.

We have previously shown that 3-phenylpyrazolo[1,5-a]pyrimidines exemplified by 8 were potent antagonists of the human corticotropin-releasing factor-1 receptor. A series of 3-pyridylpyrazolo[1,5-a]pyrimidines 15, 25-30, 34, and 35 containing a weakly basic pyridine ring at the 3-position of the bicyclic nucleus was designed to reduce lipophilicity from the initial leads such as 7. Here, we showed that these 3-pyridyl compounds exhibited potent antagonists at the human CRF(1) receptor. Moreover, the hydrophilic and weakly basic pyridine moiety increased the water solubility of some analogues. Compound 26 h exhibited good binding affinity at the human CRF(1) receptor with a K(i) value of 3.5 nM. As a functional antagonist, it dose-dependently inhibited CRF-stimulated cAMP production in cells expressing the CRF(1) receptor (IC(50) = 50 nM), and CRF-stimulated ACTH release from cultured rat pituitary cells (IC(50) = 20 nM). 26 h had a log P value of 4.9 and water solubility of greater than 10 mg/mL. Pharmacokinetic studies in rats showed that 26 h was orally bioavailable and able to penetrate into the brain. 26 h has been demonstrated in vivo efficacy in animal behavioral models that measure anxiolytic activity. These results suggest that analogues from this series were potent CRF(1) receptor antagonists with proper physicochemical properties and good pharmacokinetic profiles. 26 h was developed into a clinical compound and exhibited efficacy in patients with major depression.

The discovery of novel uracil phenylethylamines bearing a butyric acid as potent human gonadotropin-releasing hormone receptor (hGnRH-R) antagonists is described. A major focus of this optimization was to improve the CYP3A4 inhibition liability of these uracils while maintaining their GnRH-R potency. R-4-{2-[5-(2-fluoro-3-methoxyphenyl)-3-(2-fluoro-6-[trifluoromethyl]benzyl)-4-methyl-2,6-dioxo-3,6-dihydro-2H-pyrimidin-1-yl]-1-phenylethylamino}butyric acid sodium salt, 10b (elagolix), was identified as a potent and selective hGnRH-R antagonist. Oral administration of 10b suppressed luteinizing hormone in castrated macaques. These efforts led to the identification of 10b as a clinical compound for the treatment of endometriosis.