Orally administered novel cyclic pentapeptide P-317 alleviates symptoms of diarrhoea-predominant irritable bowel syndrome

Objective The aim of our study was to characterize the effect of P-317, a novel cyclic derivative of morphiceptin, on gastrointestinal (GI) motility and abdominal pain in mouse models mimicking symptoms of diarrhoea-predominant irritable bowel syndrome (IBS-D). Methods The effect of P-317 on mouse intestinal motility was characterized in vitro and in vivo in physiological and pathopysiological conditions. The antinociceptive action of P-317 was characterized in the mustard oil-induced abdominal pain model and the writhing test. Locomotor activity and grip-strength tests were used to evaluate the effect of P-317 in the central nervous system (CNS). To translate our study to clinical conditions, the semi-quantitative expression of μ-opioid receptors (MOP) and κ-opioid receptors (KOP) messenger RNA (mRNA) in human colonic samples from IBS-D patients was quantified. Key findings In vitro, P-317 (10−10–10−6 M) inhibited colonic and ileal smooth muscle contractions in a concentration-dependent, β-funaltrexamine and nor-binaltorphimine-reversible manner. In vivo, P-317 (0.1 mg/kg, i.p. and 1 mg/kg, p.o.) inhibited GI transit, displayed a potent antinociceptive action in abdominal pain tests and did not influence the CNS. Conclusion P-317 produced a potent analgesic and antidiarrhoeal action in the mouse GI tract after oral administration. Given lower expression of MOP and KOP mRNA in IBS-D patients, P-317 is a promising peptide-based drug candidate for IBS-D therapy.