Safety and efficacy of ulimorelin administered postoperatively to accelerate recovery of gastrointestinal motility following partial bowel resection: results of two randomized, placebo-controlled phase 3 trials

Postoperative ileus-Immune mechanisms and potential therapeutic interventions

BACKGROUND

Postoperative ileus (POI) is a condition marked by a temporary suppression of gastrointestinal motility following abdominal surgery. The mechanism of POI encompasses various factors and is characterized by two phases: the early neurogenic phase involving both adrenergic and non-adrenergic neural pathways; the later immune-mediated phase is characterized by a sterile inflammatory response that lasts several days. Activation of muscularis macrophages triggers a sterile inflammatory process that results in dysfunction of the enteric nervous system (ENS) and a reversible inhibition of gastrointestinal motility.

PURPOSE

In this minireview, recent insights in the pathophysiological mechanisms underlying POI and potential new therapeutic strategies are described.

Prucalopride and Bowel Function Post Gastrointestinal Surgery: Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Prolonged postoperative ileus (PPOI) contributes to morbidity and prolonged hospitalization. Prucalopride, a selective 5-hydroxytryptamine receptor agonist, may enhance bowel motility. This review assesses whether the perioperative use of prucalopride compared to placebo is associated with accelerated return of bowel function post gastrointestinal (GI) surgery.

METHODS

OVID, CENTRAL, and EMBASE were searched as of January 2024 to identify randomized controlled trials (RCTs) comparing prucalopride and placebo for prevention of PPOI in adult patients undergoing GI surgery. The primary outcomes were time to stool, time to flatus, and time to oral tolerance. The secondary outcomes were incidence of PPOI, length of stay (LOS), postoperative complications, adverse events, and overall costs. The Cochrane risk of bias tool for randomized trials and the Grading of Recommendations, Assessment, Development, and Evaluations framework were used. An inverse variance random effects model was used.

RESULTS

From 174 citations, 3 RCTs with 139 patients in each treatment group were included. Patients underwent a variety of GI surgeries. Patients treated with prucalopride had a decreased time to stool (mean difference 36.82 hours, 95% CI 59.4 to 14.24 hours lower, I2 = 62%, low certainty evidence). Other outcomes were not statistically significantly different (very low certainty evidence). Postoperative complications and adverse events could not be meta-analyzed due to heterogeneity; yet individual studies suggested no significant differences (very low certainty evidence).

DISCUSSION

Current RCT evidence suggests that prucalopride may enhance postoperative return of bowel function. Larger RCTs assessing patient important outcomes and associated costs are needed before routine use of this agent.

Postoperative ileus after digestive surgery: Network meta-analysis of pharmacological intervention

AIMS

Several medicinal treatments for avoiding postoperative ileus (POI) after abdominal surgery have been evaluated in randomized controlled trials (RCTs). This network meta-analysis aimed to explore the relative effectiveness of these different treatments on ileus outcome measures.

METHODS

A systematic literature review was performed to identify RCTs comparing treatments for POI following abdominal surgery. A Bayesian network meta-analysis was performed. Direct and indirect comparisons of all regimens were simultaneously compared using random-effects network meta-analysis.

RESULTS

A total of 38 RCTs were included in this network meta-analysis reporting on 6371 patients. Our network meta-analysis shows that prokinetics significantly reduce the duration of first gas (mean difference [MD] = 16 h; credible interval -30, -3.1; surface under the cumulative ranking curve [SUCRA] 0.418), duration of first bowel movements (MD = 25 h; credible interval -39, -11; SUCRA 0.25) and duration of postoperative hospitalization (MD -1.9 h; credible interval -3.8, -0.040; SUCRA 0.34). Opioid antagonists are the only treatment that significantly improve the duration of food recovery (MD -19 h; credible interval -26, -14; SUCRA 0.163).

CONCLUSION

Based on our meta-analysis, the 2 most consistent pharmacological treatments able to effectively reduce POI after abdominal surgery are prokinetics and opioid antagonists. The absence of clear superiority of 1 treatment over another highlights the limits of the pharmacological principles available.

Use of prokinetic agents in hospitalised adult patients: A scoping review

BACKGROUND

Gastrointestinal motility is important for adequate uptake of fluids and nutrition but is often impaired in hospitalised patients. Prokinetic agents enhance gastrointestinal motility and are prescribed for many hospitalised patients. In this scoping review, we aimed to systematically describe the body of evidence on the use of prokinetic agents in hospitalised patients. We hypothesised, that the body of evidence would be limited and derive from heterogeneous populations.

METHODS

We conducted this scoping review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews statement. We searched Medline, Embase, Epistemonikos and the Cochrane Library for studies assessing the use of prokinetic agents on any indication and outcome in adult hospitalised patients. We used a modified version of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) to assess the certainty of evidence.

RESULTS

We included 102 studies with a total of 8830 patients. Eighty-six studies were clinical trials (84%), and 52 (60%) of these were conducted in the intensive care unit, with feeding intolerance as the main indication. In the non-intensive care setting the indications were wider; most studies assessed use of prokinetic agents before gastroscopy to improve visualisation. The most studied prokinetic agent was metoclopramide (49% of studies) followed by erythromycin (31%). In total 147 outcomes were assessed with only 67% of the included studies assessing patient-centred outcomes, and with gastric emptying as the most frequently reported outcome. Overall, the data provided no firm evidence on the balance between the desirable and undesirable effects of prokinetic agents.

CONCLUSIONS

In this scoping review, we found that the studies addressing prokinetic agents in hospitalised adults had considerable variations in indications, drugs and outcomes assessed, and that the certainty of evidence was judged to be low to very low.

Review article: An analysis of the pharmacological rationale for selecting drugs to inhibit vomiting or increase gastric emptying during treatment of gastroparesis

BACKGROUND

Drugs which can inhibit nausea/vomiting and/or increase gastric emptying are used to treat gastroparesis, mostly 'off-label'. Within each category, they act at different targets and modulate different physiological mechanisms.

AIMS

Address the questions: In gastroparesis, why should blocking one pathway causing vomiting, be more appropriate than another? Why might increasing gastric emptying via one mechanism be more appropriate than another?

METHODS

Drugs used clinically were identified via consensus opinions and reviews, excluding the poorly characterised. Their pharmacology was defined, mapped to mechanisms influencing vomiting and gastric emptying, and rationale developed for therapeutic use.

RESULTS

Vomiting: Rationale for 5-HT₃ , D₂ , H₁ or muscarinic antagonists, and mirtazapine, amitriptyline, nortriptyline, are poor. Arguments for inhibiting central consequences of vagal afferent transmission by NK₁ antagonism are complicated by doubts over effects on nausea. Gastric emptying: Confusion emerges because of side-effects of drugs increasing gastric emptying: Metoclopramide (5-HT₄ agonist, D₂ and 5-HT₃ antagonist; also blocks some emetic stimuli and causes tardive dyskinesia) and Erythromycin (high-efficacy motilin agonist, requiring low doses to minimise side-effects). Limited trials with selective 5-HT₄ agonists indicate variable efficacy.

CONCLUSIONS

Several drug classes inhibiting vomiting have no scientific rationale. NK₁ antagonism has rationale but complicated by limited efficacy against nausea. Studies must resolve variable efficacy of selective 5-HT₄ agonists and apparent superiority over motilin agonists. Overall, lack of robust activity indicates a need for novel approaches targeting nausea (e.g., modulating gastric pacemaker or vagal activity, use of receptor agonists or new targets such as GDF15) and objective assessments of nausea.

Shenhuang Plaster Application Improves Gastrointestinal Motility in Mice with Postoperative Ileus through Intestinal Microbiota

Postoperative ileus (POI) is a common surgical complication, and its incidence remains high. Shenhuang Plaster (SHP) is a famous traditional Chinese medicine with a definite curative effect on postoperative intestinal dysfunction; however, the mechanisms involved in these effects are unclear. Accordingly, in this study, we constructed a POI mouse model and used the intestinal flora as the target to explore the regulatory effect of SHP on gastrointestinal motility. The results illustrated that SHP applied at the Shenque acupoint promoted the recovery of gastrointestinal motility, relieved intestinal villus atrophy and basal damage caused by POI, protected the integrity of intestinal tissue morphology, and alleviated the inflammatory response in the intestinal tissue of POI model mice. In addition, we clarified the role of the intestinal flora in the occurrence and development of POI, further evaluated the changes in the intestinal flora in each group of mice, and analysed the regulatory effect of SHP on the intestinal flora in mice with POI. The results suggested that SHP might improve gastrointestinal motility disorder in POI mice by effectively regulating intestinal flora.

Advances in the Development of Nonpeptide Small Molecules Targeting Ghrelin Receptor

Ghrelin is an octanoylated peptide acting by the activation of the growth hormone secretagogue receptor, namely, GHS-R1a. The involvement of ghrelin in several physiological processes, including stimulation of food intake, gastric emptying, body energy balance, glucose homeostasis, reduction of insulin secretion, and lipogenesis validates the considerable interest in GHS-R1a as a promising target for the treatment of numerous disorders. Over the years, several GHS-R1a ligands have been identified and some of them have been extensively studied in clinical trials. The recently resolved structures of GHS-R1a bound to ghrelin or potent ligands have provided useful information for the design of new GHS-R1a drugs. This perspective is focused on the development of recent nonpeptide small molecules acting as GHS-R1a agonists, antagonists, and inverse agonists, bearing classical or new molecular scaffolds, as well as on radiolabeled GHS-R1a ligands developed for imaging. Moreover, the pharmacological effects of the most studied ligands have been discussed.

Postoperative Ileus: a Pharmacological Perspective

Post-operative ileus (POI) is a frequent complication after abdominal surgery. The consequences of POI can be potentially serious such as bronchial inhalation or acute functional renal failure. Numerous advances in peri-operative management, particularly early rehabilitation, have made it possible to decrease POI. Despite this, the rate of prolonged POI ileus remains high and can be as high as 25% of patients in colorectal surgery. From a pathophysiological point of view, POI has two phases, an early neurological phase and a later inflammatory phase, to which we could add a "pharmacological" phase during which analgesic drugs, particularly opiates, play a central role. The aim of this review article is to describe the phases of the pathophysiology of POI, to analyse the pharmacological treatments currently available through published clinical trials and finally to discuss the different research areas for potential pharmacological targets.

Postoperative Ileus and Postoperative Gastrointestinal Tract Dysfunction: Pathogenic Mechanisms and Novel Treatment Strategies Beyond Colorectal Enhanced Recovery After Surgery Protocols

Postoperative ileus (POI) and postoperative gastrointestinal tract dysfunction (POGD) are well-known complications affecting patients undergoing intestinal surgery. GI symptoms include nausea, vomiting, pain, abdominal distention, bloating, and constipation. These iatrogenic disorders are associated with extended hospitalizations, increased morbidity, and health care costs into the billions and current therapeutic strategies are limited. This is a narrative review focused on recent concepts in the pathogenesis of POI and POGD, pipeline drugs or approaches to treatment. Mechanisms, cellular targets and pathways implicated in the pathogenesis include gut surgical manipulation and surgical trauma, neuroinflammation, reactive enteric glia, macrophages, mast cells, monocytes, neutrophils and ICC's. The precise interactions between immune, inflammatory, neural and glial cells are not well understood. Reactive enteric glial cells are an emerging therapeutic target that is under intense investigation for enteric neuropathies, GI dysmotility and POI. Our review emphasizes current therapeutic strategies, starting with the implementation of colorectal enhanced recovery after surgery protocols to protect against POI and POGD. However, despite colorectal enhanced recovery after surgery, it remains a significant medical problem and burden on the healthcare system. Over 100 pipeline drugs or treatments are listed in Clin.Trials.gov. These include 5HT4R agonists (Prucalopride and TAK 954), vagus nerve stimulation of the ENS-macrophage nAChR cholinergic pathway, acupuncture, herbal medications, peripheral acting opioid antagonists (Alvimopen, Methlnaltexone, Naldemedine), anti-bloating/flatulence drugs (Simethiocone), a ghreline prokinetic agonist (Ulimovelin), drinking coffee, and nicotine chewing gum. A better understanding of the pathogenic mechanisms for short and long-term outcomes is necessary before we can develop better prophylactic and treatment strategies.

Guidelines for Perioperative Care in Cytoreductive Surgery (CRS) with or without hyperthermic IntraPEritoneal chemotherapy (HIPEC): Enhanced Recovery After Surgery (ERAS®) Society Recommendations - Part II: Postoperative management and special considerations

BACKGROUND

Enhanced recovery after surgery (ERAS) pathways have been shown to considerably reduce complications, length of stay and costs after most of surgical procedures by standardised application of best evidence-based perioperative care. The aim was to elaborate dedicated recommendations for cytoreductive surgery (CRS) ± hyperthermic intraperitoneal chemotherapy (HIPEC) in a two-part series of guidelines based on expert consensus. The present part II of the guidelines highlights postoperative management and special considerations.

METHODS

The core group assembled a multidisciplinary panel of 24 experts involved in peritoneal surface malignancy surgery representing the fields of general surgery (n = 12), gynaecological surgery (n = 6), and anaesthesia (n = 6). Experts systematically reviewed and summarized the available evidence on 72 identified perioperative care items, following the GRADE (grading of recommendations, assessment, development, evaluation) system. Final consensus (defined as ≥50%, or ≥70% of weak/strong recommendations combined) was reached by a standardised 2-round Delphi process, regarding the strength of recommendations.

RESULTS

Response rates were 100% for both Delphi rounds. Quality of evidence was evaluated high, moderate low and very low, for 15 (21%), 26 (36%), 29 (40%) and 2 items, respectively. Consensus was reached for 71/72(98.6%) items. Strong recommendations were defined for 37 items. No consensus could be reached regarding the preemptive use of fresh frozen plasma.

CONCLUSION

The present ERAS recommendations for CRS ± HIPEC are based on a standardised expert consensus process providing clinicians with valuable guidance. There is an urgent need to produce high quality studies for CRS ± HIPEC and to prospectively evaluate recommendations in clinical practice.

Ileus in the critically ill: causes, treatment and prevention

Bowel dysfunction, especially ileus, has been increasingly recognized in critically ill patients. Ileus is commonly associated to constipation, however abnormal motility can also concern the upper digestive tract, therefore impaired gastrointestinal transit (IGT) seems to be a more appropriate term. IGT, especially constipation, is common among patients under mechanical ventilation, occurring in up to 80% of the patients during the first week, and has been associated with worse outcome in intensive care unit (ICU). It is acknowledged that the most relevant definition for constipation in ICU is the absence of stool for the first six days after admission. Concerning the upper digestive intolerance (UDI), the diagnosis should rely only on vomiting and the systematic gastric residual volume (GRV) monitoring should be avoided. IGT results from a complex pathophysiology in which both the critical illness and its specific treatments may have a deleterious role. Both observational and experimental studies have shown the deleterious effect of sepsis, multiorgan failure, sedation (especially opioids) and mechanical ventilation on gut function. To date few studies have reported effect of treatment on IGT and the level of evidence is low. However, cholinesterase inhibitors seem safe and could probably be used in case of constipation but remains poorly prescribed. Prevention with bowel management protocol using osmotic laxatives appears to be safe but did not demonstrate its effectiveness. For patients treated with high posology of opioids during sedation, enteral opioid antagonists may be a promising strategy.

The effects of ulimorelin, a ghrelin agonist, on liquid gastric emptying and colonic transit in humans

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 < .05)) in gastric emptying from baseline that were sustained through Day 6. However, no effects on GC₂₄ were observed. Pharmacokinetic analyses suggested that the free concentrations of ulimorelin achieved in POI trials and dosing frequency may have been inadequate.

CONCLUSIONS AND INFERENCES

Ulimorelin is a potent gastric prokinetic but lacks evidence of activity in the human colon, pointing to the stomach as the predominant site of action of ghrelin in humans; ClinicalTrials.gov NCT02993055.

Applications of fluorine-containing amino acids for drug design

Fluorine-containing amino acids are becoming increasingly prominent in new drugs due to two general trends in the modern pharmaceutical industry. Firstly, the growing acceptance of peptides and modified peptides as drugs; and secondly, fluorine editing has become a prevalent protocol in drug-candidate optimization. Accordingly, fluorine-containing amino acids represent one of the more promising and rapidly developing areas of research in organic, bio-organic and medicinal chemistry. The goal of this Review article is to highlight the current state-of-the-art in this area by profiling 42 selected compounds that combine fluorine and amino acid structural elements. The compounds under discussion represent pharmaceutical drugs currently on the market, or in clinical trials as well as examples of drug-candidates that although withdrawn from development had a significant impact on the progress of medicinal chemistry and/or provided a deeper understanding of the nature and mechanism of biological action. For each compound, we present features of biological activity, a brief history of the design principles and the development of the synthetic approach, focusing on the source of tailor-made amino acid structures and fluorination methods. General aspects of the medicinal chemistry of fluorine-containing amino acids and synthetic methodology are briefly discussed.

Growth Hormone Secretagogues and the Regulation of Calcium Signaling in Muscle

Growth hormone secretagogues (GHS) are a family of synthetic molecules, first discovered in the late 1970s for their ability to stimulate growth hormone (GH) release. Many effects of GHS are mediated by binding to GHS-R1a, the receptor for the endogenous hormone ghrelin, a 28-amino acid peptide isolated from the stomach. Besides endocrine functions, both ghrelin and GHS are endowed with some relevant extraendocrine properties, including stimulation of food intake, anticonvulsant and anti-inflammatory effects, and protection of muscle tissue in different pathological conditions. In particular, ghrelin and GHS inhibit cardiomyocyte and endothelial cell apoptosis and improve cardiac left ventricular function during ischemia–reperfusion injury. Moreover, in a model of cisplatin-induced cachexia, GHS protect skeletal muscle from mitochondrial damage and improve lean mass recovery. Most of these effects are mediated by GHS ability to preserve intracellular Ca²⁺ homeostasis. In this review, we address the muscle-specific protective effects of GHS mediated by Ca²⁺ regulation, but also highlight recent findings of their therapeutic potential in pathological conditions characterized by skeletal or cardiac muscle impairment.

A multicenter, randomized, double-blind study of ulimorelin and metoclopramide in the treatment of critically ill patients with enteral feeding intolerance: PROMOTE trial

PURPOSE

Enteral 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.

METHODS

One hundred twenty ICU patients were randomized 1:1 to ulimorelin or metoclopramide for 5 days. EFI was diagnosed by a gastric residual volume (GRV) ≥ 500 ml. 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 5 days of treatment. Secondary end points included feeding success, defined as 80% DPP; gastric emptying, assessed by paracetamol absorption; incidences of recurrent intolerance (GRV ≥ 500 ml); vomiting or regurgitation; aspiration, defined by positive tracheal aspirates for pepsin; and pulmonary infection.

RESULTS

One 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 5 days 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.

CONCLUSIONS

Both prokinetic agents achieved similar rates of feeding success, and no safety differences between the two treatment groups were observed.

Anti-emetic Action of the Brain-Penetrating New Ghrelin Agonist, HM01, Alone and in Combination With the 5-HT3 Antagonist, Palonosetron and With the NK1 Antagonist, Netupitant, Against Cisplatin- and Motion-Induced Emesis in Suncus murinus (House Musk Shrew)

Ghrelin has well-known activity to stimulate appetite and weight gain. Evidence suggests that ghrelin may also have effects in reducing chemotherapy-induced emesis via growth hormone secretagogue receptors (GHS-R1A) in the brain. However, it is not known whether the stimulation of GHS-R1A has broad inhibitory anti-emetic effects. In the present studies, we used Suncus murinus to investigate the potential of the new and novel orally bioavailable brain-penetrating GHS-R1A mimetic, HM01 (1-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-3-methyl-3-[(4R)-1-Methyl-3,3-dimethyl-4-piperidyl]urea), to reduce emesis induced by a variety of emetic challenges. HM01 (1 to 30 mg/kg, p.o.) antagonized emesis induced by cisplatin (30 mg/kg, i.p.) and by motion (4 cm horizontal displacement, 1 Hz) but was ineffective against emesis induced by nicotine (5 mg/kg, s.c.) and copper sulfate (120 mg/kg by intragastric gavage). In other experiments, HM01 (3 mg/kg, p.o.) enhanced the anti-emetic control of a regimen of palonosetron (0.01 mg/kg, p.o.) alone and palonosetron (0.01 mg/kg p.o.) plus netupitant (1 mg/kg, p.o.). HM01 (10 mg/kg, p.o.) also had positive effects in increasing feeding and drinking in nicotine-treated animals, and it shortened the latency to drink in animals treated with cisplatin. These data indicate that brain-penetrating GHS-R1A agonists may have use alone and/or in combination with standard anti-emetic regimens for the treatment of chemotherapy-induced nausea and vomiting and motion sickness.

Cardiovascular safety of prokinetic agents: A focus on drug-induced arrhythmias

BACKGROUND

Gastrointestinal sensorimotor dysfunction underlies a wide range of esophageal, gastric, and intestinal motility and functional disorders that collectively constitute nearly half of all referrals to gastroenterologists. As a result, substantial effort has been dedicated toward the development of prokinetic agents intended to augment or restore normal gastrointestinal motility. However, the use of several clinically efficacious gastroprokinetic agents, such as cisapride, domperidone, erythromycin, and tegaserod, is associated with unfavorable cardiovascular safety profiles, leading to restrictions in their use.

PURPOSE

The purpose of this review is to detail the cellular and molecular mechanisms that lead commonly to drug-induced cardiac arrhythmias, specifically drug-induced long QT syndrome, torsades de pointes, and ventricular fibrillation, to examine the cardiovascular safety profiles of several classes of prokinetic agents currently in clinical use, and to explore potential strategies by which the risk of drug-induced cardiac arrhythmia associated with prokinetic agents and other QT interval prolonging medications can be mitigated successfully.

Postoperative ileus following major colorectal surgery

BACKGROUND

Postoperative ileus (POI) is characterized by delayed gastrointestinal recovery following surgery. Current knowledge of pathophysiology, clinical interventions and methodological challenges was reviewed to inform modern practice and future research.

METHODS

A systematic search of MEDLINE and Embase databases was performed using search terms related to ileus and colorectal surgery. All RCTs involving an intervention to prevent or reduce POI published between 1990 and 2016 were identified. Grey literature, non-full-text manuscripts, and reanalyses of previous RCTs were excluded. Eligible articles were assessed using the Cochrane tool for assessing risk of bias.

RESULTS

Of 5614 studies screened, 86 eligible articles describing 88 RCTs were identified. Current knowledge of pathophysiology acknowledges neurogenic, inflammatory and pharmacological mechanisms, but much of the evidence arises from animal studies. The most common interventions tested were chewing gum (11 trials) and early enteral feeding (11), which are safe but of unclear benefit for actively reducing POI. Others, including thoracic epidural analgesia (8), systemic lidocaine (8) and peripheral μ antagonists (5), show benefit but require further investigation for safety and cost-effectiveness.

CONCLUSION

POI is a common condition with no established definition, aetiology or treatment. According to current literature, minimally invasive surgery, protocol-driven recovery (including early feeding and opioid avoidance strategies) and measures to avoid major inflammatory events (such as anastomotic leak) offer the best chances of reducing POI.

Postoperative Ileus: Pathophysiology, Current Therapeutic Approaches

Postoperative ileus, which develops after each abdominal surgical procedure, is an iatrogenic disorder characterized by a transient inhibition of gastrointestinal motility. Its pathophysiology is complex involving pharmacological (opioids, anesthetics), neural, and immune-mediated mechanisms. The early neural phase, triggered by activation of afferent nerves during the surgical procedure, is short lasting compared to the later inflammatory phase. The latter starts after 3-6 h and lasts several days, making it a more interesting target for treatment. Insight into the triggers and immune cells involved is of great importance for the development of new therapeutic strategies. In this chapter, the pathogenesis and the current therapeutic approaches to treat postoperative ileus are discussed.

Ghrelin and Motilin Control Systems in GI Physiology and Therapeutics

Ghrelin and motilin are released from gastrointestinal endocrine cells during hunger, to act through G protein-coupled receptors that have closely related amino acid sequences. The actions of ghrelin are more complex than motilin because ghrelin also exists outside the GI tract, it is processed to des-acyl ghrelin which has activity, ghrelin can exist in truncated forms and retain activity, the ghrelin receptor can have constitutive activity and is subject to biased agonism and finally additional ghrelin-like and des-acyl ghrelin receptors are proposed. Both ghrelin and motilin can stimulate gastric emptying, acting via different pathways, perhaps influenced by biased agonism at the receptors, but research is revealing additional pathways of activity. For example, it is becoming apparent that reduction of nausea may be a key therapeutic target for ghrelin receptor agonists and perhaps for compounds that modulate the constitutive activity of the ghrelin receptor. Reduction of nausea may be the mechanism through which gastroparesis symptoms are reduced. Intriguingly, a potential ability of motilin to influence nausea is also becoming apparent. Ghrelin interacts with digestive function through its effects on appetite, and ghrelin antagonists may have a place in treating Prader-Willi syndrome. Unlike motilin, ghrelin receptor agonists also have the potential to treat constipation by acting at the lumbosacral defecation centres. In conclusion, agonists of both ghrelin and motilin receptors hold potential as treatments for specific subsets of digestive system disorders.

Prokinetics in the Management of Functional Gastrointestinal Disorders

PURPOSE OF REVIEW

The goal of this review is to review the current status of prokinetics and to place it in historical context. Impaired motility and thus propulsion have long been thought to play important roles in the pathogenesis of a number of gastrointestinal disorders including gastroesophageal reflux disease (GERD), gastroparesis, chronic idiopathic pseudo-obstruction, and constipation. Historically, disordered motility was also thought to contribute to a number of functional gastrointestinal disorders such as functional dyspepsia (FD) and irritable bowel syndrome (IBS).

RECENT FINDINGS

As we learn more of the pathophysiology of FD, IBS, GERD, constipation, and gastroparesis, the limitations of a therapeutic strategy based on the stimulation of motility (i.e., the use of a prokinetic) have become apparent and the disappointments of the past explained. The development of prokinetic drugs has also been hampered by the non-selective nature of many of the agents studied to date which resulted in some unexpected side effects. There is still an unmet need for an effective and safe prokinetic, but drug development in this area must be mindful of the challenges of the area and the need for selectivity for a given target receptor.

Future Treatment of Constipation-associated Disorders: Role of Relamorelin and Other Ghrelin Receptor Agonists

There is an unmet need for effective pharmacological therapies for constipation, a symptom that significantly deteriorates patients’ quality of life and impacts health care. Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor and has been shown to exert prokinetic effects on gastrointestinal (GI) motility via the vagus and pelvic nerves. The pharmacological potential of ghrelin is hampered by its short half-life. Ghrelin receptor (GRLN-R) agonists with enhanced pharmacokinetics were thus developed. Centrally penetrant GRLN-R agonists stimulate defecation and improve impaired lower GI transit in animals and humans. This review summarizes the current knowledge on relamorelin, a potent ghrelin mimetic, and other GRLN-R analogs which are in preclinical or clinical stages of development for the management of disorders with underlying GI hypomotility, like constipation.

The use of alvimopan for postoperative ileus in small and large bowel resections

Transient ileus is a normal physiologic process after surgery. When prolonged, it is an important contributor to postoperative complications, increased length of stay and increased healthcare costs. Efforts have been made to prevent and manage postoperative ileus; alvimopan is an oral, peripheral μ-opioid receptor antagonist, and the only currently US FDA-approved medication to accelerate the return of gastrointestinal function postoperatively.

Disorders of gastrointestinal hypomotility

Ingestion and digestion of food as well as expulsion of residual material from our gastrointestinal tract requires normal propulsive, i.e. motor, function. Hypomotility refers to inherited or acquired changes that come with decreased contractile forces or slower transit. It not only often causes symptoms but also may compromise nutritional status or lead to other complications. While severe forms, such as pseudo-obstruction or ileus, may have a tremendous functional impact, the less severe forms of hypomotility may well be more relevant, as they contribute to common disorders, such as functional dyspepsia, gastroparesis, chronic constipation, and irritable bowel syndrome (IBS). Clinical testing can identify changes in contractile activity, defined by lower amplitudes or abnormal patterns, and the related effects on transit. However, such biomarkers show a limited correlation with overall symptom severity as experienced by patients. Similarly, targeting hypomotility with pharmacological interventions often alters gut motor function but does not consistently improve symptoms. Novel diagnostic approaches may change this apparent paradox and enable us to obtain more comprehensive information by integrating data on electrical activity, mechanical forces, patterns, wall stiffness, and motions with information of the flow of luminal contents. New drugs with more selective effects or more specific delivery may improve benefits and limit adverse effects. Lastly, the complex regulation of gastrointestinal motility involves the brain-gut axis as a reciprocal pathway for afferent and efferent signaling. Considering the role of visceral input in emotion and the effects of emotion on visceral activity, understanding and managing hypomotility disorders requires an integrative approach based on the mind-body continuum or biopsychosocial model of diseases.

Pharmacological management to prevent ileus in major abdominal surgery: a systematic review and meta-analysis

BACKGROUND

Prolonged ileus is a common complication following gastrointestinal surgery, with an incidence of up to 40 %. Investigations examining pharmacological treatment of ileus have proved largely disappointing; however, recently, several compounds have been shown to have benefited when used as prophylaxis to prevent ileus.

OBJECTIVE

This review aimed to evaluate the safety and efficacy of compounds which have been recently developed or repurposed to reduce bowel recovery time, thereby preventing ileus.

DATA SOURCES

Data were taken from a systematic review of the MEDLINE, EMBASE and Cochrane Library Databases, in addition to manual searching of reference lists up to April 2015. No limits were applied.

STUDY SELECTION

Only randomized trials were eligible for inclusion.

INTERVENTIONS

Opioid receptor antagonists, ghrelin receptor agonists and serotonin receptor agonists used for the prevention of postoperative ileus in gastrointestinal surgery.

MAIN OUTCOME MEASURES

Outcomes of time to first defecation, first flatus and composite bowel recovery endpoints (GI2 and GI3) were used to determine efficacy. Pooled treatment effects were presented as the standard mean difference or as hazard ratios alongside the corresponding 95 % confidence intervals. Risk of bias was assessed using the Cochrane risk of bias framework.

RESULTS

A total of 17 studies were included in the final analysis. The μ-opioid receptor antagonist alvimopan and serotonin receptor agonists appeared to significantly shorten the duration of ileus. The use of Ghrelin receptor agonists did not appear to have any effect in five trials. No publication bias was detected.

LIMITATIONS

Most of the trials were poorly reported and of mixed quality. Future studies must focus on the development of a set of core outcomes.

CONCLUSIONS

There is evidence to make a strong recommendation for the use of alvimopan in major gastrointestinal surgery to reduce postoperative ileus. Further randomized trials are required to establish whether serotonin receptor agonists are of use. Identifying a low-cost compound to promote bowel recovery following surgery could reduce complications and shorten duration of hospital admissions.

Randomised clinical trial: prucalopride, a colonic pro-motility agent, reduces the duration of post-operative ileus after elective gastrointestinal surgery

BACKGROUND

Previous studies have shown that recovery of colonic transit is a major determinant of post-operative ileus and clinical recovery after gastrointestinal surgery. Prucalopride is a highly selective 5-hydroxytryptamine receptor-4 agonist with colonic pro-motility effects.

AIM

To evaluate the effect and safety of prucalopride on post-operative ileus and surgical outcomes after elective gastrointestinal surgery.

METHODS

In this phase II randomised clinical trial, 110 patients undergoing elective gastrointestinal surgery were randomised to either oral prucalopride (2 mg/day) (n = 55) or placebo (n = 55). Intervention was started 24 h after surgery and stopped after defecation or maximally at 7 days. The primary outcome was time to defecation. Secondary outcomes included time to first passage of flatus, tolerance of solid food, nasogastric tube reinsertion, post-operative length of stay, hospital readmission, overall cost, time to walk independently, surgical complications and inflammatory parameters.

RESULTS

Patients who received prucalopride had a shorter time to defecation (65.0 vs. 94.5 h, P = 0.001), passage of flatus (53.0 vs. 73.0 h, P < 0.001), and post-operative length of stay (7.0 vs. 8.0 days, P = 0.001) than controls. The number of patients with prolonged ileus (>5 days) (16.4% vs. 34.5%, P = 0.026) and the C-reactive protein level on post-operative day 5 (35.67 vs. 59.07 mg/L, P = 0.040) were lower in the prucalopride group. There was no significant difference in post-operative Clavien-Dindo grade III and IV complications (P = 0.606) between the groups.

CONCLUSION

Prucalopride is a safe and effective treatment to reduce post-operative ileus and systemic inflammation without affecting post-operative complications in patients undergoing elective gastrointestinal surgery. ClinicalTrials.gov: NCT02004652.

Ghrelin and motilin receptors as drug targets for gastrointestinal disorders

The gastrointestinal tract is the major source of the related hormones ghrelin and motilin, which act on structurally similar G protein-coupled receptors. Nevertheless, selective receptor agonists are available. The primary roles of endogenous ghrelin and motilin in the digestive system are to increase appetite or hedonic eating (ghrelin) and initiate phase III of gastric migrating myoelectric complexes (motilin). Ghrelin and motilin also both inhibit nausea. In clinical trials, the motilin receptor agonist camicinal increased gastric emptying, but at lower doses reduced gastroparesis symptoms and improved appetite. Ghrelin receptor agonists have been trialled for the treatment of diabetic gastroparesis because of their ability to increase gastric emptying, but with mixed results; however, relamorelin, a ghrelin agonist, reduced nausea and vomiting in patients with this disorder. Treatment of postoperative ileus with a ghrelin receptor agonist proved unsuccessful. Centrally penetrant ghrelin receptor agonists stimulate defecation in animals and humans, although ghrelin itself does not seem to control colorectal function. Thus, the most promising uses of motilin receptor agonists are the treatment of gastroparesis or conditions with slow gastric emptying, and ghrelin receptor agonists hold potential for the reduction of nausea and vomiting, and the treatment of constipation. Therapeutic, gastrointestinal roles for receptor antagonists or inverse agonists have not been identified.

Gastrointestinal hormones and gut motility

PURPOSE OF REVIEW

To summarize the recent findings.

RECENT FINDINGS

Studies of changes in the plasma levels confirm the earlier concepts, but offer little proof of causal effect. It is increasingly realized that peptides produced in the gut have a paracrine role or an indirect effect via the gut-brain axis. Interest in prokinetic peptide agonists remains high despite the failure of two candidate drugs, but relamorelin and camicinal offer new hope.

SUMMARY

We review the original studies published since January 2013 on peptides produced in the gut and with an effect on gastrointestinal motility.

The Pentapeptide RM-131 Promotes Food Intake and Adiposity in Wildtype Mice but Not in Mice Lacking the Ghrelin Receptor

The gastrointestinal peptide hormone ghrelin is the endogenous ligand of the growth hormone secretagogue receptor (a.k.a. ghrelin receptor, GHR). Currently, ghrelin is the only circulating peripheral hormone with the ability to promote a positive energy balance by stimulating food intake while decreasing energy expenditure and body fat utilization, as defined in rodents. Based on these and additional, beneficial effects on metabolism, the endogenous ghrelin system is considered an attractive target to treat diverse pathological conditions including those associated with eating/wasting disorders and cachexia. As the pharmacological potential of ghrelin is hampered by its relatively short half-life, ghrelin analogs with enhanced pharmacokinetics offer the potential to sustainably improve metabolism. One of these ghrelin analogs is the pentapeptide RM-131, which promotes food intake and adiposity with higher potency as compared to native ghrelin in rodents. Whereas, the effect of RM-131 on energy metabolism is solidly confirmed in rodents, it remains elusive whether RM-131 exerts its effect solely via the ghrelin receptor. Accordingly, we assessed the receptor specificity of RM-131 to promote food intake and adiposity in mice lacking the GHR. Our data show that in wildtype mice RM-131 potently promotes weight gain and adiposity through stimulation of food intake. However, RM-131 fails to affect food intake and body weight in mice lacking the GHR, underlining that the anabolic effects of RM-131 are mediated via the ghrelin receptor in mice.

New developments in colorectal surgery

PURPOSE OF REVIEW

Surgical management of diseases of the colon and rectum continues to evolve. This review examines the recent publications that have led to or may lead to changes in practice in this field.

RECENT FINDINGS

We identified and reviewed the recent publications in the areas of colon, rectal, and anal cancers; inflammatory bowel disease; incontinence; diverticulitis; hemorrhoids; fistulas; and quality improvement initiatives.

SUMMARY

New technologies and novel questions have changed practice and will improve patient outcomes. Multiinstitutional studies, ideally randomized, continue to be essential to answer the questions that will lead to identification of best practices.

Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients

BACKGROUND

Postoperative ileus is a significant clinical challenge lacking effective management strategies. Ghrelin-receptor stimulation has promotility effects in the upper and lower gastrointestinal tract.

OBJECTIVE

This proof-of-concept, phase 2, randomized study evaluated the safety and efficacy of the ghrelin-receptor agonist ipamorelin in the treatment of postoperative ileus following abdominal surgery (ClinicalTrials.gov NCT00672074).

DESIGN

The design was a multicenter, double-blind, placebo-controlled, clinical trial.

SETTINGS

The settings include hospital inpatients.

PATIENTS

The patients were adults undergoing small and large bowel resection by open or laparoscopic surgery.

INTERVENTION

The intervention was intravenous infusions of 0.03-mg/kg ipamorelin vs placebo twice daily, on postoperative day 1 to 7 or hospital discharge.

MAIN OUTCOME MEASURES

Safety was assessed by monitoring adverse events and laboratory tests. The key efficacy endpoint was time from first dose of study drug to tolerance of a standardized solid meal.

RESULTS

One hundred seventeen patients were enrolled, of whom 114 patients composed the safety and modified intent-to-treat populations. Demographic and disease characteristics were balanced between groups. Overall incidence of any treatment-emergent adverse events was 87.5 % in the ipamorelin group and 94.8 % in placebo group. Median time to first tolerated meal was 25.3 and 32.6 h in the ipamorelin and placebo groups, respectively (p = 0.15).

LIMITATIONS

This proof of concept study was small and enrolled patients with a broad range of underlying conditions.

CONCLUSIONS

Ipamorelin 0.03-mg/kg twice daily for up to 7 days was well tolerated. There were no significant differences between ipamorelin and placebo in the key and secondary efficacy analyses.

Novel and conventional receptors for ghrelin, desacyl-ghrelin, and pharmacologically related compounds

The only molecularly identified ghrelin receptor is the growth hormone secretagogue receptor GHSR1a. Its natural ligand, ghrelin, is an acylated peptide whose unacylated counterpart (UAG) is almost inactive at GHSR1a. A truncated, nonfunctional receptor, GHSR1b, derives from the same gene. We have critically evaluated evidence for effects of ghrelin receptor ligands that are not consistent with actions at GHSR1a. Effects of ghrelin are observed in cells or tissues where the expression of GHSR1a is not detectable or after the Ghsr gene has been inactivated. In several, effects of ghrelin are mimicked by UAG, and ghrelin binding is competitively reduced by UAG. Effects in the absence of GHSR1a and sites at which ghrelin and UAG have similar potency suggest the presence of novel nonspecific ghrelin receptors (ghrelin receptor-like receptors [GRLRs]). A third class of receptor, the UAG receptors, at which UAG, but not ghrelin, is an agonist has been proposed. None of the novel receptors, with the exception of the glycoprotein CD36, which accounts for ghrelin action at a limited number of sites, have been identified. GHSR1a and GHSR1b combine with other G protein-coupled receptors to form heterodimers, whose pharmacologies differ from their components. Thus, it is feasible some GRLRs and some UAG receptors are heterodimers. Effects mediated through GRLRs or UAG receptors include adipocyte lipid accumulation, myoblast differentiation, osteoblast proliferation, insulin release, cardioprotection, coronary artery constriction, vascular endothelial cell proliferation, and tumor cell proliferation. The molecular identification and pharmacologic characterization of novel ghrelin receptors are thus important objectives.

Brain peptides and the modulation of postoperative gastric ileus

Postoperative ileus (POI) develops after abdominal surgery irrespective of the site of surgery. When prolonged, POI can lead to longer hospitalization times and higher healthcare costs. Moreover, it is associated with complaints for the patient. In order to develop new strategies to treat this condition, a deeper understanding of the pathophysiology of the POI is necessary. This review will focus on brain peptides (ghrelin, nesfatin-1, somatostatin, corticotropin-releasing factor, thyrotropin-releasing hormone and calcitonin gene-related peptide) involved in the mediation of POI and the possible modulation of these pathways to shorten the time of POI. Lastly, the role of vagal signaling or chewing gum as potential treatment strategies of alleviating symptoms of POI is discussed.

Preclinical gastrointestinal prokinetic efficacy and endocrine effects of the ghrelin mimetic RM-131

AIMS

The 28 amino acid hormone ghrelin, the natural ligand for the growth hormone secretagogue, or ghrelin receptor (GHR), has diverse physiological functions, including a possible role as a gastrointestinal prokinetic. The synthetic ghrelin mimetic RM-131 is in Phase II clinical trials for treatment of diabetic gastroparesis and other gastrointestinal (GI) disorders. We aimed to determine the relative potency of RM-131, when compared to other GI ghrelin mimetics, to predict efficacy and determine the role of RM-131 in models of inflammatory bowel disease.

MAIN METHODS

We evaluated and compared ghrelin, RM-131 and other synthetic ghrelin mimetics for their prokinetic potency in models of gastrointestinal disorders in the rat and we evaluated the endocrine (rats and dogs) and anti-inflammatory effects (mice) of the ghrelin mimetic RM-131.

KEY FINDINGS

The pentapeptide RM-131 increased gastric emptying in rodent models of ileus. RM-131 is about 100-fold more potent than human ghrelin and is 600 to 1800-fold more potent, when compared to several investigational ghrelin mimetics tested in clinical trials. RM-131 has anti-inflammatory effects and significantly increases survival and reduces macroscopic markers of tissue damage in a TNBS model of inflammatory bowel disease. RM-131 treatment shows a transient increase in growth hormone levels in Beagle dogs and rats, returning to baseline upon chronic treatment. Significant effects on glucose and insulin are not observed in chronic studies.

SIGNIFICANCE

RM-131's potency, efficacy and endocrine profile, are promising attributes for the treatment of diverse functional gastrointestinal disorders in humans.

Discontinued drugs for pulmonary, allergy, gastrointestinal, arthritis (2012)

INTRODUCTION

Various compounds are developed to interfere with pathogenic pathways involved in inflammation processes. Some of them are able to enter the clinical development for different diseases with a common pathogenic denominator such as, for example, rheumatoid arthritis and chronic obstructive pulmonary disease (COPD), based on the preclinical evidence, but not all these molecules prove to be efficacious while tested in different phases of clinical development.

AREAS COVERED

This review discusses about the drugs that were discontinued from further development for pulmonary, allergy, gastrointestinal and arthritis diseases

EXPERT OPINION

Most of the drugs discontinued during 2012 were compounds with anti-inflammatory activity which were mostly designed to treat arthritis/rheumatoid arthritis. Some of these molecules were also intended for COPD. Many of them failed the late phases of the clinical development.