The discovery and optimisation of benzazepine sulfonamide and sulfones as potent agonists of the motilin receptor.

Optimisation of a series of benzazepine sulfonamide hit compounds identified from high throughput screening led to the discovery of a new series of tractable, potent motilin receptor agonists.

Identification of small molecule agonists of the motilin receptor.

High-throughput screening resulted in the identification of a series of novel motilin receptor agonists with relatively low molecular weights. The series originated from an array of biphenyl derivatives designed to target 7-transmembrane (7-TM) receptors. Further investigation of the structure-activity relationship within the series resulted in the identification of compound (22) as a potent and selective agonist at the motilin receptor.

The discovery of biaryl carboxamides as novel small molecule agonists of the motilin receptor.

Optimisation of urea (5), identified from high throughput screening and subsequent array chemistry, has resulted in the identification of pyridine carboxamide (33) which is a potent motilin receptor agonist possessing favourable physicochemical and ADME profiles. Compound (33) has demonstrated prokinetic-like activity both in vitro and in vivo in the rabbit and therefore represents a promising novel small molecule motilin receptor agonist for further evaluation as a gastroprokinetic agent.

Characterization of a calcitonin gene-related peptide release assay in rat isolated distal colon.

The release of calcitonin gene-related peptide (CGRP) plays a key role gastrointestinal tract homeostasis. We aimed to investigate mechanisms that mediate CGRP release from the rat colon in vitro. Colon segments were stimulated and the amount of CGRP released was measured using an enzyme immunoassay. Capsaicin and low pH induced significant increases in CGRP release which was shown to be mediated by TRPV1 activation as demonstrated with the TRPV1 antagonists CTPC and capsazepine. The mast cell degranulator, compound 48/80 significantly increased CGRP release an effect that was blocked in the presence of the mast cell stabilizer, ketotifen and the selective Gi inhibitor benzalkonium chloride. The addition of a mixture of inflammatory mediators containing pro-inflammatory cytokines, 5HT, bradykinin and PGE2 showed no effect at neutral pH but at low pH a significant additive effect was observed. We conclude that CGRP release in the rat distal colon occurs in response to mast cell degranulation, inflammatory mediators, low pH and capsaicin and describe a role for TRPV1 receptors in mediating the response.

UDP-glucose modulates gastric function through P2Y14 receptor-dependent and -independent mechanisms.

P2Y receptors have been reported to modulate gastrointestinal functions. The newest family member is the nucleotide-sugar receptor P2Y14. P2ry14 mRNA was detected throughout the rat gut, with the highest level being in the forestomach. We investigated the role of the receptor in stomach motility using cognate agonists and knockout (KO) mice. In rat isolated forestomach, 100 microM UDP-glucose and 100 muM UDP-galactose both increased the baseline muscle tension (BMT) by 6.2+/-0.6 and 1.6+/-0.6 mN (P<0.05, n=3-4), respectively, and the amplitude of contractions during electrical field stimulation (EFS) by 3.7+/-1.7 and 4.3+/-2.5 mN (P<0.05, n=3-4), respectively. In forestomach from wild-type (WT) mice, 100 microM UDP-glucose increased the BMT by 1.0+/-0.1 mN (P<0.05, n=6) but this effect was lost in the KO mice (change of -0.1+/-0.1 mN, n=6). The 100 microM UDP-glucose also increased the contraction amplitude during EFS in this tissue from the WT animals (0.9+/-0.4 mN, P < 0.05, n=6) but not from the KO mice (0.0+/-0.2 mN, n=6). In vivo, UDP-glucose at 2,000 mg/kg ip reduced gastric emptying in rats by 49.7% (P<0.05, n=4-6) and in WT and KO mice by 56.1 and 66.2%, respectively (P<0.05, n=7-10) vs. saline-treated control animals. There was no significant difference in gastric emptying between WT and KO animals receiving either saline or d-glucose. These results demonstrate a novel function of the P2Y14 receptor associated with contractility in the rodent stomach that does not lead to altered gastric emptying after receptor deletion and an ability of UDP-glucose to delay gastric emptying without involving the P2Y14 receptor.

Discovery of N-(3-fluorophenyl)-1-[(4-([(3S)-3-methyl-1-piperazinyl]methyl)phenyl)acetyl]-4-piperidinamine (GSK962040), the first small molecule motilin receptor agonist clinical candidate.

N-(3-fluorophenyl)-1-[(4-([(3S)-3-methyl-1-piperazinyl]methyl)phenyl)acetyl]-4-piperidinamine 12 (GSK962040) is a novel small molecule motilin receptor agonist. It possesses excellent activity at the recombinant human motilin receptor and also at the native rabbit motilin receptor where its agonist activity results in potentiation of the amplitude of neuronal-mediated contractions of isolated gastric antrum tissue. Compound 12 also possesses highly promising pharmacokinetic profiles in both rat and dog, and these results, in combination with further profiling in human native tissue and an in vivo model of gastrointestinal transit in the rabbit, have led to its selection as a candidate for further development.

Potentiation by cholinesterase inhibitors of cholinergic activity in rat isolated stomach and colon.

Acetylcholinesterase (AChE) inhibitors stimulate gastrointestinal (GI) motility and are potential treatments of conditions associated with inadequate GI motility. The ability of itopride to facilitate neuronally (predominantly cholinergic) mediated contractions of rat isolated stomach, evoked by electrical field stimulation (EFS), has been compared with other cholinesterase inhibitors and with tegaserod, a clinically effective prokinetic and non-selective 5-HT(4) receptor agonist which also facilitates GI cholinergic function. Neostigmine greatly increased EFS-evoked contractions over a narrow concentration range (0.01-1 microM; 754+/-337% facilitation at 1 microM); higher concentrations (1, 3 microM) also increased muscle tension. Donepezil increased EFS-evoked contractions gradually over the full range of concentrations (0.01-10 microM; maximum increase 516+/-20% at 10 microM). Itopride increased the contractions even more gradually, rising to 188+/-84% at 10 microM. The butyrylcholinesterase inhibitor iso-OMPA 0.01-10 microM also increased EFS-evoked contractions, to a maximum of 36+/-5.0% at 10 microM, similar to that caused by tegaserod (35+/-5.2% increase at 1 microM). The effects of tegaserod, but not itopride were inhibited by the 5-HT(4) receptor antagonist SB-204070A 0.3 microM. In rat isolated colon, neostigmine was again the most efficacious, causing a defined maximum increase in EFS-evoked contractions (343+/-82% at 10 microM), without changing muscle tension. Maximum increases caused by donepezil and itopride were, respectively, 57.6+/-20 and 43+/-15% at 10 microM. These data indicate that the abilities of different AChE inhibitors to increase GI cholinergic activity differ markedly. Understanding the reasons is essential if AChE inhibitors are to be optimally developed as GI prokinetics.