The effects of GR205171, a selective tachykinin NK1 receptor antagonist, were investigated on both the acute and delayed phases of cisplatin‐induced nausea‐like behaviour and vomiting in the conscious piglet. Animals receiving cisplatin (5.5 mg kg−1, i.v.) were observed for 60 h. Fifteen min prior to cisplatin infusion (T0−15 min), eight piglets acting as controls received an intravenous injection of saline solution (1 ml kg−1), whereas experimental animals received a single i.v. administration of GR205171 (1 ml kg−1) at a dose of 0.01 (n=8), 0.03 (n=8), 0.1 (n=8), 0.3 (n=16) or 1.0 (n=13) mg kg−1. In eight additional piglets, GR205171 (1 mg kg−1) was administered 15 min before the onset of the delayed phase (T16−15 min). A further five piglets received GR205171 (1 mg kg−1) every 6 h throughout the experiment. The latencies of the first emetic episode (EE) and nausea‐like behavioural episode (NE) increased in all experimental groups treated at T0−15 min, and the total number of both EE and NE during the 60 h was reduced in a dose‐dependent manner. In piglets treated at T0−15 min with GR205171 1 mg kg−1, eight out of 13 (62%) did not vomit throughout the experiment. Animals treated with GR205171 (1 mg kg−1) at T16−15 min exhibited an acute response to cisplatin but did not vomit during the delayed phase. The greatest inhibition of both nausea‐like behaviour and vomiting was observed in piglets receiving multiple injections of GR205171. These results demonstrate the long‐lasting anti‐emetic effects of GR205171, and confirm the key role of substance P within the emetic reflex. British Journal of Pharmacology (1998) 124, 1643–1650; doi:10.1038/sj.bjp.0702019

The medicinal chemistry strategy is described which led to the identification of GR205171, an orally active non-peptide neurokinin-1 receptor antagonist that is the most potent broad-spectrum antiemetic agent reported to date.

The introduction of 5-HT3 antagonists, such as ondansetron, as antiemetic agents has transformed the management of patients receiving chemotherapy or radiation therapy. Studies in animal models with NK1 antagonists suggest that these represent a new class of antiemetic agents having a broader spectrum of activity than 5-HT3 antagonists. Compounds of this class may prove to be more effective in man against delayed emesis induced by cisplatin, postoperative nausea and vomiting and motion sickness. Thus, they have the potential to complement 5-HT3 antagonists and so provide a further advance in the management of nausea and vomiting.

Sialyl Lewis X (SLe(x)) analogs 2a and 2b were synthesised, where the N-acetyl-D-glucose and the D-galactose units of SLe(x) 1 were replaced with an alkyl and a heteroalkyl spacer. Sulphate ester 6i was also synthesised from alcohol 6b and chlorosulphonic acid. A novel promoter. silver mercaptoethanesulphonate. was used to synthesise alpha-sialosides 2c, 7b and 7c.

It has been demonstrated recently that antagonists of the tachykinin NK1 receptor, specifically CP-99,994 and GR203040, possess anti-emetic activity in a range of species. To optimise this activity, a series of analogues based around the structure of GR203040 have been synthesised and their affinity at the human tachykinin NK1 receptor determined. In addition, the potency of these analogues to inhibit emesis induced in the ferret by whole-body X-irradiation has been examined. A range of substitutions at the C-1 position of the tetrazole moiety in GR203040 were explored in vitro and in vivo. The trifluoromethyl compound, GR205171, was the most potent antagonist with regard to the ability to inhibit emesis induced by X-irradiation, This compound was demonstrated to have a broad spectrum of anti-emetic activity, inhibiting emesis in the ferret induced by cisplatin, cyclophosphamide, morphine, ipecacuanha and copper sulphate. Furthermore, emesis was also inhibited in the house-musk shrew, Suncus murinus, when induced by either motion or cisplatin, and in the dog when induced by ipecacuanha. GR205171 has the most potent anti-emetic activity of any tachykinin NK1 receptor antagonist described to date. The compound is orally active in the ferret and dog, long-lasting, and warrants further investigation as a potential broad-spectrum anti-emetic agent.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

SR 48968, N-Methyl-N-[4-(4-acetamido-4-phenylpiperidinyl)-2S-(3,4-dichlorophenyl) butyl]benzamide is a potent and selective non-peptidic antagonist of the NK2 receptor. photoactivatable analogue containing a diazirine moiety also binds with high affinity. This compound is potentially useful for identifying residues at the antagonist binding site of the NK2 receptor.

Two different strategies have been developed in order to synthesise an analogue and potential mimic of sialyl Lewis X that incorporates a carboxymethyl group and a C-2-symmetric 2,3-butanediol unit as replacements for the sialic acid and the N-acetylglucosamine residues respectively.

The synthesis and activity of a novel spiro-piperidine non-peptide antagonist (2) of the neurokinin-1 (NK1) receptor is described. Despite having essentially the same solution conformation as CP 99,994 (1) at physiological pH, (2) has reduced affinity for the NK1 receptor.

The synthesis of a series of 2-(5-fluoro-1H-indol-3-yl)ethyl spiropiperidines is described together with their tachykinin NK2 receptor affinities measured in a rat colon binding assay. Equivalent NK2 receptor binding affinity was observed for the spirooxazolidinone 3-benzyl-8-[2-(5-fluoro-1H-indol-3-yl)ethyl]-1-oxa-3,8-diazaspiro[4,5]decan-2-one (3a), the imidazolidinone 3-benzyl-8-[2-(5-fluoro-1H-indol-3-yl)ethyl]-1,3,8-triazaspiro[4,5]decan-2-one (3s), and the pyrrolidinone 2-benzyl-8-[2-(5-fluoro-1H-indol-3-yl)ethyl]-2,8-diazaspiro[4,5]decan-3-one (3t). Substitution in the phenyl ring of compound 3a produced no significant enhancement in NK2 binding affinity. Replacement of the phenyl ring in 3a with other aromatic rings resulted in a significant loss in binding affinity. Compound 3a was shown to be a potent NK2 receptor antagonist in guinea pig trachea where it also demonstrated 1000-fold selectivity for NK2 receptors over NK1. In the anesthetized guinea pig, compound 3a administered by the intravenous or oral route displayed potent and long-lasting antagonist activity against NK2 receptor agonist induced bronchoconstriction.

The presence of an ortho hydroxymethyl group in arylmethyl sulphoxides results in the exclusive formation of chloromethyl sulphides, mediated via an intramolecular attack to yield an alkoxysulphonium salt. This intramolecular attack prevents the formation of siloxymethyl sulphides which would result via the sila-Pummerer rearrangement.

Arylmethyl sulphoxides treated with trialkylsilyl halide and base undergo a Pummerer-type rearrangement to give α-siloxy and α-chlorosulphides. However, the presence of an ortho hydroxymethyl group results in the exclusive and efficient formation of the α-chlorosulphides, presumably mediated via an intramolecular attack to yield an alkoxysulphonium salt. These 2-(hydroxymethyl)aryl chloromethylsulphides can then be converted into the corresponding 3,1-benzoxathiins via an intramolecular cyclisation. Preliminary investigation of the chemistry of these 3,1-benzoxathiins, reveals that in one case, a novel base induced ring contraction occurs to yield a benzothiophene.

1 Following our earlier observations that the tachykinin NK, receptor antagonist CP-99,994 is an effective anti-emetic in ferrets, we have examined the anti-emetic effects of a more potent and novel NK1 receptor antagonist, GR203040, against various emetic stimuli in the ferret, dog and house musk shrew (Suncus murinus).2 In ferrets, GR203040 (0.1 mg kg(-1) s.c. or i.v.) is effective against emesis induced by radiation, cisplatin, cyclophosphamide, copper sulphate, ipecacuanha or morphine. 3 In animals in which emesis had been established with cisplatin, GR203040 (1 mg kg(-1) s.c.) was fully effective as an interventional treatment. No further emesis was seen in animals treated with GR203040 whilst saline-treated animals continued to vomit.4 GR203040 (0.1 mg kg(-1) s.c.) retains anti-emetic efficacy in the ferret, even when given as a 6 h pretreatment, indicating that this compound has a long duration of action. The compound is also effective orally at the same dose, when given as a 90 min pretreatment.5 GR203040 (0.1 mg kg(-1) i.v.) is fully effective against ipecacuanha-induced emesis in the dog.6 GR203040 is effective against motion- and cisplatin-induced emesis in Suncus murinus. These effects were seen at doses an order of magnitude greater than those shown to be effective against cisplatin in the ferret.7 In conclusion, GR203040 is a novel anti-emetic agent, and the broad spectrum of anti-emetic activity, together with activity observed in three species, suggests that this compound is worthy of clinical investigation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

1. The in vitro and in vivo pharmacology of GR203040 ((2S, 3S)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), a novel, highly potent and selective non-peptide tachykinin NK1 receptor antagonist, was investigated in the present study. 2. GR203040 potently inhibited [3H]-substance P binding to human NK1 receptors expressed in Chinese hamster ovary (CHO) and U373 MG astrocytoma cells, and NK1 receptors in ferret and gerbil cortex (pKi values of 10.3, 10.5, 10.1 and 10.1 respectively). GR203040 had lower affinity at rat NK1 receptors (pKi = 8.6) and little affinity for human NK2 receptors (pKi < 5.0) in CHO cells and NK3 receptors in guinea-pig cortex (pKi < 6.0). With the exception of the histamine H1 receptor (pIC50 = 7.5). GR203040 had little affinity (pIC50 < 6.0) at all non-NK1 receptors and ion channels examined. Furthermore, GR203040 produced only weak inhibition of Na+ currents in SH-SY5Y neuroblastoma and superior cervical ganglion cells (pIC50 values < 4.0). GR203040 produced only weak antagonism of Ca(2+)-evoked contractions of rat isolated portal vein (pKn = 4.1). The enantiomer of GR203040, GR205608 (2R, 3R)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), had 10,000 fold lower affinity at the human NK1 receptor expressed in CHO cells (pKi = 6.3). 3. In gerbil ex vivo binding experiments, GR203040 produced a dose-dependent inhibition of the binding of [3H]-substance P to cerebral cortical membranes (ED50 = 15 micrograms kg-1 s.c. and 0.42 mg kg-1 p.o.). At 10 micrograms kg-1 s.c., the inhibition of [3H]-substance P binding was maintained for > 6 h. In the rat, GR203040 was less potent (ED50 = 15.4 mg kg-1 s.c.) probably reflecting, at least in part, its lower affinity at the rat NK1 receptor. 4. In guinea-pig isolated ileum and dog isolated middle cerebral and basilar arteries, GR203040 produced a rightward displacement of the concentration-effect curves to substance P methyl ester (SPOMe) with suppression of the maximum agonist response (apparent pKB values of 11.9, 11.2 and 11.1 respectively). 5. In anaesthetized rabbits, GR203040 antagonized reductions in carotid arterial vascular resistance evoked by SPOMe, injected via the lingual artery (DR10 (i.e. the dose producing a dose-ratio of 10) = 1.1 micrograms kg-1, i.v.). At a dose 20 fold greater than its DR10 value (i.e. 22 micrograms kg-1, i.v.), significant antagonism was evident more than 2 h after GR203040 administration. 6. In anaesthetized rats, GR203040 (3 and 10 mg kg-1, i.v.) produced a dose-dependent inhibition of plasma protein extravasation in dura mater, conjunctiva, eyelid and lip in response to electrical stimulation of the trigeminal ganglion. 7. It is concluded that GR203040 is one of the most potent and selective NK1 receptor antagonists yet described, and as such, has considerable potential as a pharmacological tool to characterize the physiological and pathological roles of substance P and NK1 receptors. GR203040 may also have potential as a novel therapeutic agent for the treatment of conditions such as migraine, emesis and pain.