Abstract
The in vitro and in vivo pharmacological profile of SB 223412 [(S)-(−)-N-(α-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-carboxamide], a novel human NK-3 (hNK-3) receptor antagonist, is described. SB 223412 demonstrated enantioselective affinity for inhibition of [125I][MePhe7]neurokinin B (NKB) binding to membranes of CHO cells expressing the hNK-3 receptor (CHO hNK-3). SB 223412, the (S)-isomer, (K i = 1.0 nM), has similar affinity as the natural ligand, NKB (K i = 0.8 nM) and another nonpeptide NK-3 receptor antagonist, SR 142801 (K i = 1.2 nM). SB 223412 was selective for hNK-3 receptors compared with hNK-1 (>10,000-fold selective) and hNK-2 receptors (>140-fold selective), and selectivity was further demonstrated by its lack of effect, in concentrations up to 1 or 10 μM, in >60 receptor, enzyme and ion channel assays. SB 223412 enantioselectively inhibited the NKB-induced Ca++mobilization in HEK 293 cells stably expressing the hNK-3 receptor. SB 223412 (10–1,000 nM) produced concentration-dependent rightward shifts in NKB-induced Ca++ mobilization concentration-response curves with a K b value of 3 nM. In addition, SB 223412 antagonized senktide-induced contraction in the isolated rabbit iris sphincter muscle (K b = 1.6 nM). In mice, oral administration of SB 223412 produced dose-dependent inhibition of behavioral responses induced by the NK-3 receptor-selective agonist, senktide (ED50 = 12.2 mg/kg). Pharmacokinetic evaluation of SB 223412 in rat and dog indicated low plasma clearance, oral bioavailability and high and sustained plasma concentrations after 4 to 8 mg/kg oral dosages. The preclinical profile of SB 223412 (high affinity, selectivity, reversibility and oral activity) suggests that it will be a useful tool compound to define the physiological and pathophysiological roles of NK-3 receptors.
Footnotes
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Send reprint requests to: Henry M. Sarau, Ph.D., SmithKline Beecham Pharmaceuticals, Department of Pulmonary Pharmacology (UW 2531), 709 Swedeland Road, King of Prussia, PA 19406. E-mail:Skip_Sarau-1{at}sbphrd.com
- Abbreviations:
- NK-1
- neurokinin 1
- NK-2
- neurokinin 2
- NK-3
- neurokinin 3
- CHO
- Chinese hamster ovary
- CHO hNK-3
- CHO cells stably expressing the human neurokinin -3 receptor
- CHO hNK-2
- CHO cells stably expressing the human neurokinin-2 receptor
- CHO hNK-1
- CHO cells expressing the human neurokinin -1 receptor
- HEK
- human embryonic kidney
- HEK 293 hNK-3
- HEK 293 cells stably expressing the human NK-3 receptor
- NKA
- neurokinin A
- NKB
- neurokinin B
- BSA
- bovine serum albumin
- KRH
- Krebs-Ringer-Henseleit
- EC50
- concentration of agonist producing 50% of maximal response
- IC50
- concentration of antagonist causing 50% inhibition of agonist response
- Ki
- apparent inhibition constant
- Kb
- dissociation constant
- PCR
- polymerase chain reaction
- LC/MS/MS
- liquid chromatography with triple quadrupole mass spectrometric detection
- Received September 18, 1996.
- Accepted February 14, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
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