A novel tachykinin NK2 receptor antagonist prevents motility-stimulating effects of neurokinin A in small intestine

1 MEN 11420 (nepadutant) is a potent, selective and competitive antagonist of tachykinin NK2 receptors. 2 The objective of the present study was to assess the capability of the drug to antagonize the stimulatory effects of neurokinin A (NKA) on gastrointestinal motility, as well as to change the fasting migrating motor complex (MMC). 3 Thirty-four male volunteers were randomized to treatment with either placebo or MEN 11420 in a double-blinded manner. Effects of MEN 11420 (8 mg intravenously) were evaluated as changes in phases I, II and III of MMC as well as contraction frequency, amplitude and motility index during baseline conditions and during stimulation of motility using NKA (125 pmol kg(-1) min(-1) intravenously). 4 NKA preceded by placebo increased the fraction of time occupied by phase II, increased contraction frequency, amplitude and motility index. 5 MEN 11420 effectively antagonized the motility-stimulating effects of NKA. MEN 11420 reduced the phase II-stimulating effect of NKA. In addition, the stimulatory effect of NKA on contraction frequency and amplitude, as well as motility index were inhibited by MEN 11420. MEN 11420 did not affect the characteristics of MMC during saline infusion. 6 Plasma levels of MEN 11420 peaked during the first hour after infusion and decreased to less than half during the first 2 h. 7 In conclusion, intravenous MEN 11420 effectively inhibited NKA-stimulated, but not basal gastrointestinal motility, and was well tolerated by all subjects.