The novel 5‐HT7 receptor antagonist, SB‐269970‐A, potently displaced 3H‐5‐CT from human 5‐HT7(a) (pKi 8.9±0.1) and 5‐HT7 receptors in guinea‐pig cortex (pKi 8.3±0.2).
5‐CT stimulated adenylyl cyclase ...activity in 5‐HT7(a)/HEK293 membranes (pEC50 7.5±0.1) and SB‐269970‐A (0.03–1 μM) inhibited the 5‐CT concentration‐response with no significant alteration in the maximal response. The pA2 (8.5±0.2) for SB‐269970‐A agreed well with the pKi determined from 3H‐5‐CT binding studies.
5‐CT‐stimulated adenylyl cyclase activity in guinea‐pig hippocampal membranes (pEC50 of 8.4±0.2) was inhibited by SB‐269970‐A (0.3 μM) with a pKB (8.3±0.1) in good agreement with its antagonist potency at the human cloned 5‐HT7(a) receptor and its binding affinity at guinea‐pig cortical membranes.
5‐HT7 receptor mRNA was highly expressed in human hypothalamus, amygdala, thalamus, hippocampus and testis.
SB‐269970‐A was CNS penetrant (steady‐state brain : blood ratio of ca. 0.83 : 1 in rats) but was rapidly cleared from the blood (CLb=ca. 140 ml min−1 kg−1). Following a single dose (3 mg kg−1) SB‐269970 was detectable in rat brain at 30 (87 nM) and 60 min (58 nM). In guinea‐pigs, brain levels averaged 31 and 51 nM respectively at 30 and 60 min after dosing, although the compound was undetectable in one of the three animals tested.
5‐CT (0.3 mg kg−1 i.p.) induced hypothermia in guinea‐pigs was blocked by SB‐269970‐A (ED50 2.96 mg kg−1 i.p.) and the non‐selective 5‐HT7 receptor antagonist metergoline (0.3–3 mg kg−1 s.c.), suggesting a role for 5‐HT7 receptor stimulation in 5‐CT induced hypothermia in guinea‐pigs.
SB‐269970‐A (30 mg kg−1) administered at the start of the sleep period, significantly reduced time spent in Paradoxical Sleep (PS) during the first 3 h of EEG recording in conscious rats.
British Journal of Pharmacology (2000) 130, 539–548; doi:10.1038/sj.bjp.0703357
SB-399885 (N-3,5-dichloro-2-(methoxy)phenyl-4-(methoxy)-3-(1-piperazinyl)benzenesulfonamide) has high affinity for human recombinant and native 5-HT(6) receptors, with pK(i) values 9.11+/-0.03 and ...9.02+/-0.05, respectively and is a potent competitive antagonist (pA(2) 7.85+/-0.04). It displays over 200-fold selectivity for the 5-HT(6) receptor over all other receptors, ion channels and enzymes tested to date. SB-399885 inhibited ex vivo (125)ISB-258585 (4-Iodo-N-4-methoxy-3-(4-methyl-piperazin-1-yl)-phenyl-benzenesulfonamide) binding with an ED(50) of 2.0+/-0.24 mg/kg p.o. in rats. It had a minimum effective dose of 1 mg/kg p.o. in a rat maximal electroshock seizure threshold test and a long duration of action, overall demonstrating an excellent pharmacokinetic-pharmacodynamic correlation. Repeated administration of this agent (10 mg/kg p.o., b.i.d. for 7 days) significantly reversed a scopolamine-induced deficit (0.5 mg/kg i.p.) in a rat novel object recognition paradigm. Moreover, in aged rats (22 months old) SB-399885 (10 mg/kg p.o., b.i.d. for 7 days) fully reversed the age-dependent deficit in water maze spatial learning compared to vehicle-treated age-matched controls and significantly improved recall of the task measured by increases in the searching of the target quadrant on post-training days 1, 3 and 7. In vivo microdialysis in the rat medial prefrontal cortex demonstrated that acute SB-399885 (10 mg/kg p.o.) significantly increased extracellular acetylcholine levels. These data demonstrate that SB-399885 is a potent, selective, brain penetrant, orally active 5-HT(6) receptor antagonist with cognitive enhancing properties that are likely to be mediated by enhancements of cholinergic function. These studies provide further support for the potential therapeutic utility of 5-HT(6) receptor antagonists in disorders characterised by cognitive deficits such as Alzheimer's disease and schizophrenia.
During the lead optimization of NK₁/NK₃ receptor antagonists program, a focused exploration of molecules bearing a lactam moiety was performed. The aim of the investigation was to identify the ...optimal position of the carbonyl and hydroxy methyl group in the lactam moiety, in order to maximize the in vitro affinity and the level of insurmountable antagonism at both NK₁ and NK₃ receptors. The synthesis and biological evaluation of these novel lactam derivatives, with potent and balanced NK₁/NK₃ activity, were reported in this paper.
Bioisoteric replacement of the metabolically labile N-methyl amide group of a series of benzoxazinones with small heterocyclic rings has led to novel series of fused tricyclic benzoxazines which are ...potent 5-HT1A/B/D receptor antagonists with and without concomitant human serotonin transporter (hSerT) activity. Optimizing against multiple parameters in parallel identified 6-{2-4-(2-methyl-5-quinolinyl)-1-piperazinylethyl}-4H-imidazo5,1-c1,4benzoxazine-3-carboxamide (GSK588045) as a potent 5-HT1A/B/D receptor antagonist with a high degree of selectivity over human ether-à-go-go related gene (hERG) potassium channels, favorable pharmacokinetics, and excellent activity in vivo in rodent pharmacodynamic (PD) models. On the basis of its outstanding overall profile, this compound was progressed as a clinical candidate with the ultimate aim to assess its potential as a faster acting antidepressant/anxiolytic with reduced side-effect burden.
Starting from benzylpyrimidine 2, molecular modeling and X-ray crystallography were used to design highly potent inhibitors of Interleukin-2 inducible T-cell kinase (ITK). Sulfonylpyridine 4i showed ...sub-nanomolar affinity against ITK, was selective versus Lck and its activity in the Jurkat cell-based assay was greatly improved over 2.
Inhibition of the non-receptor tyrosine kinase ITK, a component of the T-cell receptor signalling cascade, may represent a novel treatment for allergic asthma. Here we report the structure-based ...optimization of a series of benzothiazole amides that demonstrate sub-nanomolar inhibitory potency against ITK with good cellular activity and kinase selectivity. We also elucidate the binding mode of these inhibitors by solving the X-ray crystal structures of several inhibitor-ITK complexes.
SB‐271046, potently displaced 3H‐LSD and 125I‐SB‐258585 from human 5‐HT6 receptors recombinantly expressed in HeLa cells in vitro (pKi 8.92 and 9.09 respectively). SB‐271046 also displaced ...125I‐SB‐258585 from human caudate putamen and rat and pig striatum membranes (pKi 8.81, 9.02 and 8.55 respectively).
SB‐271046 was over 200 fold selective for the 5‐HT6 receptor vs 55 other receptors, binding sites and ion channels.
In functional studies on human 5‐HT6 receptors SB‐271046 competitively antagonized 5‐HT‐induced stimulation of adenylyl cyclase activity with a pA2 of 8.71.
SB‐271046 produced an increase in seizure threshold over a wide‐dose range in the rat maximal electroshock seizure threshold (MEST) test, with a minimum effective dose of 0.1 mg kg−1 p.o. and maximum effect at 4 h post‐dose. The level of anticonvulsant activity achieved correlated well with the blood concentrations of SB‐271046 (EC50 of 0.16 μM) and brain concentrations of 0.01–0.04 μM at Cmax.
These data, together with the observed anticonvulsant activity of other selective 5‐HT6 receptor antagonists, SB‐258510 (10 mg kg−1, 2–6 h pre‐test) and Ro 04‐6790 (1–30 mg kg−1, 1 h pre‐test), in the rat MEST test, suggest that the anticonvulsant properties of SB‐271046 are likely to be mediated by 5‐HT6 receptors.
Overall, these studies demonstrate that SB‐271046 is a potent and selective 5‐HT6 receptor antagonist and is orally active in the rat MEST test. SB‐271046 represents a valuable tool for evaluating the in vivo central function of 5‐HT6 receptors.
British Journal of Pharmacology (2000) 130, 1606–1612; doi:10.1038/sj.bjp.0703457
SB‐258585 (4‐Iodo‐N‐4‐methoxy‐3‐(4‐methyl‐piperazin‐1‐yl)‐phenyl‐benzenesulphonamide) is a high affinity ligand at 5‐HT6 receptors. It displays over 100 fold selectivity for the 5‐HT6 receptor over ...all other 5‐HT receptors tested so far. SB‐258585 has been radiolabelled, to high specific activity, for its characterization as a 5‐HT6 receptor selective radioligand.
125I‐SB‐258585 bound, with high affinity, to a single population of receptors in a cell line expressing human recombinant 5‐HT6 receptors. Kinetic and saturation binding experiments gave pKD values of 9.01±0.09 and 9.09±0.02, respectively.
In membranes derived from rat or pig striatum and human caudate putamen, 125I‐SB‐258585 labelled a single site with high levels (>60%) of specific binding. Saturation analysis revealed pKD values of 8.56±0.07 for rat, 8.60±0.10 for pig and 8.90±0.02 for human. Bmax values for the tissues ranged from 173±23 and 181±25 fmol mg−1 protein in rat and pig striatum, respectively, to 215±41 fmol mg−1 protein in human caudate putamen.
The pKi rank order of potency for a number of compounds, determined in competition binding assays with 125I‐SB‐258585, at human caudate putamen membranes was: SB‐271046>SB‐258585>SB‐214111>methiothepin>clozapine>5‐Me‐OT>5‐HT>Ro 04‐6790>mianserin>ritanserin=amitriptyline>5‐CT>mesulergine. Similar profiles were obtained from pig and rat striatal membranes and recombinant 5‐HT6 receptors; data from the latter correlated well with 3H‐LSD binding.
Thus, 125I‐SB‐258585 is a high affinity, selective radioligand which can be used to label both recombinant and native 5‐HT6 receptors and will facilitate further characterization of this receptor subtype in animal and human tissues.
British Journal of Pharmacology (2000) 130, 1597–1605; doi:10.1038/sj.bjp.0703458
The evolution, synthesis, and biological activity of a novel series of 5-HT2C receptor inverse agonists are reported. Biarylcarbamoylindolines have been identified with excellent 5-HT2C affinity and ...selectivity over 5-HT2A receptors. In addition, (pyridyloxypyridyl)carbamoylindolines have been discovered with additional selectivity over the closely related 5-HT2B receptor. Compounds from this series are inverse agonists at the human cloned 5-HT2C receptor, completely abolishing basal activity in a functional assay. The new series have reduced P450 inhibitory liability compared to a previously described series of 1-(3-pyridylcarbamoyl)indolines (Bromidge et al. J. Med. Chem. 1998, 41, 1598) from which they evolved. Compounds from this series showed excellent oral activity in a rat mCPP hypolocomotion model and in animal models of anxiety. On the basis of their favorable biological profile, 32 (SB-228357) and 40 (SB-243213) have been selected for further evaluation to determine their therapeutic potential for the treatment of CNS disorders such as depression and anxiety.
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