Discovery of Aminobenzyloxyarylamides as κ Opioid Receptor Selective Antagonists: Application to Preclinical Development of a κ Opioid Receptor Antagonist Receptor Occupancy Tracer

Abstract

Arylphenylpyrrolidinylmethylphenoxybenzamides were found to have high affinity and selectivity for κ opioid receptors. On the basis of receptor binding assays in Chinese hamster ovary (CHO) cells expressing cloned human opioid receptors, (S)-3-fluoro-4-(4-((2-(3-fluorophenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (25) had a K(i) = 0.565 nM for κ opioid receptor binding while having a K(i) = 35.8 nM for μ opioid receptors and a K(i) = 211 nM for δ opioid receptor binding. Compound 25 was also a potent antagonist of κ opioid receptors when tested in vitro using a [(35)S]-guanosine 5'O-[3-thiotriphosphate] ([(35)S]GTP-γ-S) functional assay in CHO cells expressing cloned human opioid receptors. Compounds were also evaluated for potential use as receptor occupancy tracers. Tracer evaluation was done in vivo, using liquid chromatography-tandem mass spectrometry (LC/MS/MS) methods, precluding the need for radiolabeling. (S)-3-Chloro-4-(4-((2-(pyridine-3-yl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (18) was found to have favorable properties for a tracer for receptor occupancy, including good specific versus nonspecific binding and good brain uptake.

The macrocyclic tetrapeptide [D‐Trp]CJ‐15,208 produces short‐acting κ opioid receptor antagonism in the CNS after oral administration

“…The recent termination of the phase 1 clinical trials of JDTic due to undisclosed adverse effects (ClinicalTrials.gov, NCT01431586) has further spurred the search for new, safe and shorter acting KOR-selective antagonists. As discussed above, while several new non-peptide KOR antagonists have recently been reported, including some with finite durations of KOR antagonist activity (Runyon et al, 2010;Peters et al, 2011) or with short residence time in the brain (Grimwood et al, 2011;Mitch et al, 2011) after peripheral administration, reports of orally active KOR antagonists have been limited to only four KOR-selective antagonists: JDTic (Beardsley et al, 2005), an analogue of JDTic (Beardsley et al, 2010), an aminobenzyloxyarylamide (Mitch et al, 2011), and a biphenylsulfonamide (Chang et al, 2011). To date, p.o.…”

“…However, activity after p.o. administration has been reported for only four KOR selective antagonists (Beardsley et al, 2005(Beardsley et al, , 2010Chang et al, 2011;Mitch et al, 2011), but not for any of the shorter acting antagonists, prompting a continued search for KOR antagonists.…”

“…Unfortunately, this prolonged duration precludes certain key preclinical studies and could potentially impair clinical development. Recently, several new non-peptide KOR antagonists have been reported (Brugel et al, 2010;Runyon et al, 2010;Grimwood et al, 2011;Mitch et al, 2011;Peters et al, 2011;Frankowski et al, 2012), some of which demonstrated shorter durations of KOR antagonist activity (Runyon et al, 2010;Peters et al, 2011) or were detected for relatively short (<8 h) periods in the brain (Grimwood et al, 2011;Mitch et al, 2011). However, activity after p.o.…”

An Improved Antagonist Radiotracer for the κ-Opioid Receptor: Synthesis and Characterization of 11C-LY2459989

“…In vitro binding experiments and GTP-γ-S antagonist functional assays were performed according to the published procedures (30). …”

“…injection of naloxone (1 mg/kg) at 10 min before the second injection of [ 11 C]LY2459989. In the second set of experiments, a [ 11 C]LY2459989 baseline scan was followed by a blocking scan either with LY2456302 (29, 30), or the unlabeled LY2459989. A total of 12 PET scans were performed.…”