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pubmed:abstractText |
This study evaluated the in vitro and in vivo pharmacological properties of TD-8954, a potent and selective 5-HT(4) receptor agonist. TD-8954 had high affinity (pK(i)?=?9.4) for human recombinant 5-HT(4(c)) (h5-HT(4(c))) receptors, and selectivity (>2,000-fold) over all other 5-hydroxytryptamine (5-HT) receptors and non-5-HT receptors, ion channels, enzymes and transporters tested (n?=?78). TD-8954 produced an elevation of cAMP in HEK-293 cells expressing the h5-HT(4(c)) receptor (pEC(50)?=?9.3), and contracted the guinea pig colonic longitudinal muscle/myenteric plexus preparation (pEC(50)?=?8.6). TD-8954 had moderate intrinsic activity in the in vitro assays. In conscious guinea pigs, subcutaneous administration of TD-8954 (0.03-3?mg/kg) increased the colonic transit of carmine red dye, reducing the time taken for its excretion. Following intraduodenal dosing to anesthetized rats, TD-8954 (0.03-10?mg/kg) evoked a dose-dependent relaxation of the esophagus. Following oral administration to conscious dogs, TD-8954 (10 and 30??g/kg) produced an increase in contractility of the antrum, duodenum, and jejunum. In a single ascending oral dose study in healthy human subjects, TD-8954 (0.1-20?mg) increased bowel movement frequency and reduced the time to first stool. It is concluded that TD-8954 is a potent and selective 5-HT(4) receptor agonist in vitro, with robust in vivo stimulatory activity in the gastrointestinal (GI) tract of guinea pigs, rats, dogs, and humans. TD-8954 may have clinical utility in patients with disorders of reduced GI motility.
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