ly-2459989 ly-2459989 ly-2459989 is a silent antagonist of the κ-opioid receptor (kor) that has been developed by eli lilly as a radiotracer of the aforementioned receptor, labeled either with carbon-11 or fluorine-18. it possesses high affinity for the kor (ki = 0.18 nm) and is highly selective for it over the μ-opioid receptor (ki = 7.68 nm) and the δ-opioid receptor (ki = 91.3 nm) (over 43-fold selectivity for the kor over the other opioid receptors). ly-2459989 is a fluorine-containing analogue and follow-up compound of ly-2795050, the first kor-selective antagonist radiotracer. relative to ly-2795050, ly-2459989 displays 4-fold higher affinity for the kor and similar selectivity and also possesses greatly improved central nervous system permeation (brain levels were found to be 6-fold higher than those of ly-2795050). the drug appears to possess a short duration of action, with only 25% remaining in serum at 30 minutes post-injection in rhesus monkeys, making it an ideal agent for application in biomedical imaging, for instance in positron emission tomography (pet). ly-2459989clinical dataroutes ofadministrationoral, intravenousatc codenonepharmacokinetic dataelimination half-life15 minutes (in rhesus monkeys)identifiers iupac name 3-fluoro-4-methyl]phenoxy]benzamide cas number2254067-61-1 ypubchem cid134819873unii2x23m5hp34chemical and physical dataformulac23h22fn3o2molar mass391.446 g·mol−13d model (jsmol)interactive image smiles nc(=o)c1ccc(oc2ccc(cn3ccc3c4cccnc4)cc2)c(f)c1 inchi inchi=1s/c23h22fn3o2/c24-20-13-17(23(25)28)7-10-22(20)29-19-8-5-16(6-9-19)15-27-12-2-4-21(27)18-3-1-11-26-14-18/h1,3,5-11,13-14,21h,2,4,12,15h2,(h2,25,28)/t21-/m0/s1key:drghcuttxwierb-nrfanrhfsa-n earlier analogues of ly-2459989 besides ly-2795050 with similar actions and potential uses have also been described.