Search

BACKGROUND: Ulimorelin, a small molecule ghrelin agonist and prokinetic agent, was effective in animal models of gastroparesis and delayed transit. However, employing once daily administration, it failed in clinical trials of postoperative ileus (POI), a condition in which colonic motility recovers last. The aim of this study was to evaluate drug dosing and regional differences in drug activity between stomach and colon. METHODS: Gastric emptying was assessed by scintigraphy in healthy adults at single doses of 600-1200 µg kg-1 and multiple doses of 80-600 µg kg-1 Q8H for 7 days. Colonic motility was assessed by 7-region scintigraphic analysis at a dose of 600 µg kg-1 for 2 days. The primary endpoints were percent change in time to 50% (∆t50 ) liquid gastric emptying on Days 1, 4, and 6 and the geometric mean center of colonic transit at 24 hours (GC24 ). Plasma concentrations of free and total ulimorelin were measured for pharmacokinetic and exposure-response modeling. KEY RESULTS: Ulimorelin 150-600 µg kg-1 every 8 hours resulted in statistically significant improvements (∆t50 = 23% to 46% (P

PurposeEnteral feeding intolerance (EFI) is a frequent problem in the intensive care unit (ICU), but current prokinetic agents have uncertain efficacy and safety profiles. The current study compared the efficacy and safety of ulimorelin, a ghrelin agonist, with metoclopramide in the treatment of EFI.MethodsOne hundred twenty ICU patients were randomized 1:1 to ulimorelin or metoclopramide for 5days. EFI was diagnosed by a gastric residual volume (GRV) 500ml. A volume-based feeding protocol was employed, and enteral formulas were standardized. The primary end point was the percentage daily protein prescription (%DPP) received by patients over 5days of treatment. Secondary end points included feeding success, defined as 80% DPP; gastric emptying, assessed by paracetamol absorption; incidences of recurrent intolerance (GRV500ml); vomiting or regurgitation; aspiration, defined by positive tracheal aspirates for pepsin; and pulmonary infection.ResultsOne hundred twenty patients were randomized and received the study drug (ulimorelin 62, metoclopramide 58). Mean APACHE II and SOFA scores were 21.6 and 8.6, and 63.3% of patients had medical reasons for ICU admission. Ulimorelin and metoclopramide resulted in comparable %DPPs over 5days of treatment (median [Q1, Q3]: 82.9% [38.4%, 100.2%] and 82.3% [65.6%, 100.2%], respectively, p=0.49). Five-day rates of feeding success were 67.7% and 70.6% when terminations unrelated to feeding were excluded, and there were no differences in any secondary outcomes or adverse events between the two groups.ConclusionsBoth prokinetic agents achieved similar rates of feeding success, and no safety differences between the two treatment groups were observed.

Ulimorelin (TZP101) is a ghrelin receptor agonist that stimulates intestinal motility, but also reduces blood pressure in rodents and humans and dilates blood vessels. It has been proposed as a treatment for intestinal motility disorders. Here we investigated the mechanisms through which ulimorelin affects vascular diameter. Actions of ulimorelin on wall tension of rodent arteries were investigated and compared with other ghrelin receptor agonists. Saphenous, mesenteric and basilar arteries were obtained from Sprague-Dawley rats (male, 8 weeks) and saphenous arteries were obtained from wild type or ghrelin receptor null mice. These were mounted in myography chambers to record artery wall tension. Ulimorelin (0.03-30µM) inhibited phenylephrine-induced contractions of rat saphenous (IC50=0.6µM; Imax=66±5%; n=3-6) and mesenteric arteries (IC50=5µM, Imax=113±16%; n=3-4), but not those contracted by U46619, ET-1 or 60mM [K(+)]. Relaxation of phenylephrine-constricted arteries was not observed with ghrelin receptor agonists TZP102, capromorelin or AZP-531. In rat saphenous and basilar arteries, ulimorelin (10-100µM) and TZP102 (10-100µM) constricted arteries (EC50=9.9µM; Emax=50±7% and EC50=8µM; Emax=99±16% respectively), an effect not attenuated by the ghrelin receptor antagonist YIL 781 3µM or mimicked by capromorelin or AZP-531. In mesenteric arteries, ulimorelin, 1-10µM, caused a surmountable rightward shift in the response to phenylephrine (0.01-1000µM; pA2=5.7; n=3-4). Ulimorelin had similar actions in mouse saphenous artery from both wild type and ghrelin receptor null mice. We conclude that ulimorelin causes vasorelaxation through competitive antagonist action at α1-adrenoceptors and a constrictor action not mediated via the ghrelin receptor.

Background and Purpose Some agonists of ghrelin receptors cause rapid decreases in BP. The mechanisms by which they cause hypotension and the pharmacology of the receptors are unknown. Experimental Approach The effects of ligands of ghrelin receptors were investigated in rats in vivo, on isolated blood vessels and on cells transfected with the only molecularly defined ghrelin receptor, growth hormone secretagogue receptor 1a (GHSR1a). Key Results Three agonists of GHSR1a receptors, ulimorelin, capromorelin and CP464709, caused a rapid decrease in BP in the anaesthetized rat. The effect was not reduced by either of two GHSR1a antagonists, JMV2959 or YIL781, at doses that blocked effects on colorectal motility, in vivo. The rapid hypotension was not mimicked by ghrelin, unacylated ghrelin or the unacylated ghrelin receptor agonist, AZP531. The early hypotension preceded a decrease in sympathetic nerve activity. Early hypotension was not reduced by hexamethonium or by baroreceptor (sino-aortic) denervation. Ulimorelin also relaxed isolated segments of rat mesenteric artery, and, less potently, relaxed aorta segments. The vascular relaxation was not reduced by JMV2959 or YIL781. Ulimorelin, capromorelin and CP464709 activated GHSR1a in transfected HEK293 cells at nanomolar concentrations. JMV2959 and YIL781 both antagonized effects in these cells, with their pA2 values at the GHSR1a receptor being 6.55 and 7.84. Conclusions and Implications Our results indicate a novel vascular receptor or receptors whose activation by ulimorelin, capromorelin and CP464709 lowered BP. This receptor is activated by low MW GHSR1a agonists, but is not activated by ghrelin.

Ghrelin and motilin receptor agonists increase gastric motility and are attractive drug targets. However, 14 years after the receptors were described (18-24 years since ligands became available) the inactivity of the ghrelin agonist TZP-102 in patients with gastroparesis joins the list of unsuccessful motilin agonists. Fundamental questions must be asked. Pustovit et al., have now shown that the ghrelin agonist ulimorelin evokes prolonged increases in rat colorectal propulsion yet responses to other ghrelin agonists fade. Similarly, different motilin agonists induce short- or long-lasting effects in a cell-dependent manner. Together, these and other data create the hypothesis that the receptors can be induced to preferentially signal ('biased agonism') via particular pathways to evoke different responses with therapeutic advantages/disadvantages. Biased agonism has been demonstrated for ghrelin. Are motilin agonists which cause long-lasting facilitation of human stomach cholinergic function (compared with motilin) biased agonists (e.g., camicinal, under development for patients with gastric hypo-motility)? For ghrelin, additional complications exist because the therapeutic aims/mechanisms of action are uncertain, making it difficult to select the best (biased) agonist. Will ghrelin agonists be useful treatments of nausea and/or as suggested by Pustovit et al., chronic constipation? How does ghrelin increase gastric motility? As gastroparesis symptoms poorly correlate with delayed gastric emptying (yet gastro-prokinetic drugs can provide relief: e.g., low-dose erythromycin), would low doses of ghrelin and motilin agonists relieve symptoms simply by restoring neuromuscular rhythm? These questions on design and functions need addressing if ghrelin and motilin agonists are to reach patients as drugs.

Background Discovery of adequate pharmacological treatments for constipation has proven elusive. Increased numbers of bowel movements were reported as a side-effect of ulimorelin treatment of gastroparesis, but there has been no investigation of the site of action. Methods Anesthetized rats were used to investigate sites and mechanisms of action of ulimorelin. Key Results Intravenous ulimorelin (1–5 mg/kg) caused a substantial and prolonged (~1 h) increase in colorectal propulsive activity and expulsion of colonic contents. This was prevented by cutting the nerves emerging from the lumbosacral cord, by the nicotinic receptor antagonist hexamethonium and by antagonists of the ghrelin receptor. The effect of intravenous ulimorelin was mimicked by direct application of ulimorelin (5 μg) to the lumbosacral spinal cord. Conclusions & Inferences Ulimorelin is a potent prokinetic that causes propulsive contractions of the colorectum by activating ghrelin receptors of the lumbosacral defecation centers. Its effects are long-lasting, in contrast with other colokinetics that target ghrelin receptors.

Background Delayed recovery of gastrointestinal (GI) motility is a common complication following surgery. TZP-101/ulimorelin is a macrocyclic peptidomimetic ghrelin receptor agonist with GI promotility effects that significantly accelerates time to recovery of GI motility compared to placebo following partial colectomy. It is also well tolerated. The objectives of this analysis were to identify predictors of GI motility recovery in patients undergoing partial colectomy and to evaluate whether these factors affect ulimorelin acceleration of GI recovery. Methods Covariate analysis assessed the effect of eight variables—age, sex, body mass index, type of surgery (right colectomy, left colectomy, other), duration of surgery, blood loss, total opioid consumption, country—on recovery of GI motility in 236 patients randomized to ulimorelin (n = 168) or placebo (n = 68). The primary endpoint was the recovery of GI function (time from the end of surgery to first bowel movement). Stepwise regression identified a parsimonious model of the smallest subset of variables best predicting GI recovery. Results Recovery was shorter for segmental/subtotal colectomies vs. right colectomies (P = 0.016) and longer with increased total opioid use (P = 0.037). The remaining variables had no statistically significant effect on GI recovery. Effects of ulimorelin 480 μg/kg (the most effective dose) on time to GI tract recovery remained statistically and clinically significant (hazard ratio = 1.81, P = 0.014) when adjusted for surgery type and/or total opioid use. Conclusions Two factors, type of surgery and total opioid use, independently modified times to recovery of GI motility following partial large bowel resection surgery. Acceleration of recovery of GI motility by ulimorelin was independent of these factors.

Parkinson's disease (PD) affects the nerves of the entire gastrointestinal (GI) tract and may result in profound gastrointestinal (GI) dysfunction leading to poor patient outcomes. Common GI disturbances in patients with PD include gastroparesis (GP), constipation and small intestinal bacterial overgrowth syndrome (SIBO). In particular, GP is difficult to treat due to the limited options available and precautions, contraindications and adverse effects associated with the approved treatments. Moreover, some commonly used medications can worsen pre-existing PD.Our review will focus on treatment options for GP and SIBO with motilin agonists, dopamine receptor antagonists, Ghrelin agonists muscarinic agonists, 5-HT4 receptor agonists, antibiotics, probiotics and herbal formulation such as iberogast. Constipation occurs in the majority of patients with PD and fortunately many treatments are now available. Our review is based on original papers or reviews selected from PUBMED search and Cochrane reviews.Motility disorders of the GI tract are found frequently in patients with PD and treating the underlying GI disorders caused by PD with various prokinetics and laxatives is paramount in achieving improvements in patient's motor function. Various prokinetics and laxatives are now available to provide some relief of the GI morbidity caused by PD leading even to better absorption of even the PD treatments.

There remains an unmet need for effective pharmacologic treatments for gastroparesis. Ghrelin is the endogenous ligand for the growth hormone secretagogue receptor and has been shown to regulate energy homeostasis and exert prokinetic effects on gastrointestinal motility. In recent years, several ghrelin receptor agonists have been studied in clinical trials of patients with diabetic gastroparesis. The intravenous macrocyclic peptidomimetic, TZP-101, initially suggested improvement in gastroparesis symptoms with intravenous administration when compared to placebo. However, in subsequent studies of oral preparations, TZP-102 failed to confirm these results. Another ghrelin receptor agonist, RM-131, was recently shown to significantly accelerate gastric emptying (GE) in patients with type 1 and type 2 diabetes and delayed GE. RM-131 reduced total Gastroparesis Cardinal Symptom Index-Daily Diary (GCSI-DD) and composite scores among type 1 diabetics. Continued development of ghrelin agonists should be explored in attempts to expand therapeutic options for the treatment of gastroparesis.

Gastrointestinal recovery is a critical milestone after bowel resection with postoperative ileus resulting in increased risk of complications and prolonged hospitalization.The aim of this study is to evaluate the efficacy and safety of ulimorelin, a ghrelin receptor agonist given postoperatively in 2 identically designed phase 3 studies (ClinicalTrials.gov NCT01285570 and NCT01296620).This investigation is designed as a multicenter, double-blind, randomized, parallel-group study.This study involves hospital inpatients.Adult patients undergoing partial bowel resection were included.Thirty-minute intravenous infusions (160 µg/kg, 480 µg/kg ulimorelin, or placebo) once daily were started within 60 minutes after the end of surgery and ended at the first of the following: primary efficacy end point fulfilled (defined below), hospital discharge, or 7 days treatment.The primary efficacy end point was the time from the end of surgery to the composite end point of the later of first bowel movement and tolerance of solid food. Safety was assessed with the use of standard assessments including adverse events and laboratory tests.Ulimorelin Study of Efficacy and Safety 007, n = 332 patients; Ulimorelin Study of Efficacy and Safety 008, n = 330 patients: in both studies, the primary efficacy end point and the secondary efficacy outcomes, which included postsurgical time to first bowel movement, tolerance of solid food, and discharge eligibility, did not differ significantly among patients treated with either dose of ulimorelin versus placebo. Rates of serious adverse events were comparable across all treatment groups. There was no statistically significant difference from placebo in regard to events of interest, namely nausea, vomiting, ileus as an adverse event, nasogastric tube reinsertion, anastomotic complications, and infections.A possible limitation is the variance inherent in surgery and comorbidities.Although the efficacy of ulimorelin in reducing the duration of postoperative ileus was not demonstrated in these studies, intravenous ulimorelin at doses of 160 µg/kg and 480 µg/kg was generally well tolerated in postcolectomy patients. Similar to other promotility agents, ulimorelin may find an application in other indications better suited to its attributes.

High-throughput screening of Tranzyme Pharma's proprietary macrocycle library using the aequorin Ca2+-bioluminescence assay against the human ghrelin receptor (GRLN) led to the discovery of novel agonists against this G-protein coupled receptor. Early hits such as 1 (Ki=86 nM, EC50=134 nM) though potent in vitro displayed poor pharmacokinetic properties that required optimization. While such macrocycles are not fully rule-of-five compliant, principally due to their molecular weight and clogP, optimization of their pharmacokinetic properties proved feasible largely through conformational rigidification. Extensive SAR led to the identification of 2 (Ki=16 nM, EC50=29 nM), also known as ulimorelin or TZP-101, which has progressed to phase III human clinical trials for the treatment of postoperative ileus. X-ray structure and detailed NMR studies indicated a rigid peptidomimetic portion in 2 that is best defined as a nonideal type-I' β-turn. Compound 2 is 24% orally bioavailable in both rats and monkeys. Despite its potency, in vitro and in gastric emptying studies, 2 did not induce growth hormone (GH) release in rats, thus demarcating the GH versus GI pharmacology of GRLN.

Publisher Summary This chapter highlights the advances made in the area of gastrointestinal (GI) prokinetics in both the clinical and early discovery phases between 2006 and 2010, with an emphasis on the more recent developments. The quality of life for people suffering from functional gastrointestinal disorders (FGIDs) is significantly reduced when compared with that of the general population. In recent years, there have been numerous clinical advances in the field of prokinetic agents, which offer great potential for patients who suffer from FGIDs. Specifically, the launches of prucalopride and lubiprostone provide new treatment options for those with cholecystokinin (CC) and irritable bowel syndrome with constipation (IBS-C). Major advances are evident in the area of gastroparesis (GP), where the ghrelin agonist ulimorelin and TZP-102 hold much promise, and in the related motilin field, where the low-molecular-weight agonist GlaxoSmithKline (GSK)-962040 has also reached the clinic. In the chronic idiopathic constipation (CIC) arena, the first in class ileal bile acid transporter (IBAT) inhibitor A-3309 is significant. Given the complex nature of FGIDs, and specifically the low treatment responses versus placebo often observed in clinical trials, it is clear that the design of these trials is critical in ensuring success and ultimately enabling new molecular entities to reach patients.