Randomised clinical trial: ghrelin agonist TZP-101 relieves gastroparesis associated with severe nausea and vomiting--randomised clinical study subset data

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.

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.

Ghrelin and Glucagon-Like Peptide-1: A Gut-Brain Axis Battle for Food Reward

Eating behaviors are influenced by the reinforcing properties of foods that can favor decisions driven by reward incentives over metabolic needs. These food reward-motivated behaviors are modulated by gut-derived peptides such as ghrelin and glucagon-like peptide-1 (GLP-1) that are well-established to promote or reduce energy intake, respectively. In this review we highlight the antagonizing actions of ghrelin and GLP-1 on various behavioral constructs related to food reward/reinforcement, including reactivity to food cues, conditioned meal anticipation, effort-based food-motivated behaviors, and flavor-nutrient preference and aversion learning. We integrate physiological and behavioral neuroscience studies conducted in both rodents and human to illustrate translational findings of interest for the treatment of obesity or metabolic impairments. Collectively, the literature discussed herein highlights a model where ghrelin and GLP-1 regulate food reward-motivated behaviors via both competing and independent neurobiological and behavioral mechanisms.

Gastroparesis in the Hospital Setting

Gastroparesis (GP) is commonly seen in hospitalized patients. Refractory vomiting and related dehydration, electrolyte abnormalities, and malnutrition are indications for hospital admission. In addition, tube feeding intolerance is a common sign of gastric dysmotility in critically ill patients. The diagnosis and management of GP in the hospital setting can be quite challenging. Diagnostic tests are often deferred because of patient intolerance of the oral meal for standard scintigraphy or severity of the primary disease. The diagnosis of GP is often established on the basis of clinical scenario and risk factors for gastric motor dysfunction. Medical therapy in GP is directed toward controlling nausea and vomiting by prokinetic and antinausea medications and correcting nutrition risks or treating malnutrition with nutrition therapy. Enteral nutrition is the preferred nutrition intervention for patients with GP. Delayed gastric emptying in critically ill patients has a negative impact on the timely delivery of enteral feeding and meeting the energy and protein goals. Measures to improve gastric tolerance or provide feeding beyond the stomach are often needed, since early enteral nutrition has been an important target of therapy for critically ill patients. This review will address the current understanding of the mechanisms of GP and feeding intolerance in critical illness, diagnostic workup, drug therapies, and interventions to improve the provision of enteral nutrition in hospital settings when gastric dysmotility is present or suspected.

Efficacy and Safety of Ghrelin Agonists in Patients with Diabetic Gastroparesis: A Systematic Review and Meta-Analysis

Background/Aims

Ghrelin agonists are emerging prokinetic agents for treating gastroparesis. Although recent clinical trials have demonstrated their efficacy in patients with diabetic gastroparesis (DG), the impact of such agents on symptoms and gastric dysmotility remains unclear. We performed a systematic review and meta-analysis to evaluate the efficacy and safety of ghrelin agonists in patients with DG.

Methods

A search of common electronic databases (MEDLINE, Embase, and Cochrane Central Register of Controlled Trials) was preformed, using keyword combinations that referenced ghrelin and DG and retrieving all eligible randomized controlled trials (RCTs) of ghrelin agonists versus placebo in patients with DG. The primary outcome measure was the change in patient-reported overall gastroparesis symptom scores. Secondary outcomes included the change in gastric emptying time, specific symptoms related to gastroparesis, and adverse events. A random-effects model was applied to all study outcomes. Heterogeneity among studies was determined by the chi-square test and I² statistics.

Results

We selected six RCTs of patients with DG (n=557) for meta-analysis. Ghrelin agonist administration (vs placebo) significantly improved overall gastroparesis symptoms (standardized mean difference, –0.34; 95% confidence interval, –0.56 to –0.13) and significantly improved symptoms related to gastroparesis, including nausea, vomiting, early satiety, and abdominal pain. Adverse events recorded for ghrelin agonists and placebo did not differ significantly. There was no significant heterogeneity among eligible studies.

Conclusions

Compared with placebo, ghrelin agonists are effective and well-tolerated for the treatment of DG.

Ghrelin inhibits autonomic response to gastric distension in rats by acting on vagal pathway

Ghrelin is the only orexigenic peptide currently known and a potent prokinetic by promoting gastric motility but novel insights suggest that its role extends beyond satiety regulation. Whereas ghrelin was shown to provide somatic and colonic antinociception, its impact on gastric sensitivity is unknown even though stomach is a major ghrelin secreting tissue. Autonomic response to gastric mechanosensitivity was estimated by measuring blood pressure variation as a surrogate marker in response to gastric distension (GD) before and after ghrelin (or vehicle) administration. Involvement of spinal and vagal pathways in the ghrelin effect was studied by performing celiac ganglionectomy and subdiaphragmatic vagotomy respectively and by evaluating the expression of phosphorylated extracellular-regulated kinase 1/2 (p-ERK1/2) in dorsal root and nodose ganglia. Finally the phenotype of Ghrelin receptor expressing neurons within the nodose ganglia was determined by in situ hybridization and immunofluorescence. Ghrelin reduced blood pressure variation in response to GD except in vagotomized rats. Phosphorylated-ERK1/2 levels indicated that ghrelin reduced neuronal activation induced by GD in nodose ganglion. The effect of ghrelin on gastric mechanosensitivity was abolished by pre-treatment with antagonist [D-Lys³]-GHRP-6 (0.3 mg/kg i.v.). Immunofluorescence staining highlights the colocalization of Ghrelin receptor with ASIC3 and TRPV1 within gastric neurons of nodose ganglion. Ghrelin administration reduced autonomic response to gastric distension. This effect likely involved the Ghrelin receptor and vagal pathways.

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.

Pharmacological Approaches to Diabetic Gastroparesis: A systematic review of randomised clinical trials

Pharmacological interventions of diabetic gastroparesis (DG) constitute an essential element of a patient’s management. This article aimed to systematically review the available pharmacological approaches of DG, including their efficacy and safety. A total of 24 randomised clinical trials (RCTs) that investigated the efficacy and/or safety of medications targeting DG symptoms were identified using several online databases. Their results revealed that metoclopramide was the only approved drug for accelerating gastric emptying and improving disease symptoms. However, this medication may have several adverse effects on the cardiovascular and nervous systems, which might be resolved with a new intranasal preparation. Acceptable alternatives are oral domperidone for patients without cardiovascular risk factors or intravenous erythromycin for hospitalised patients. Preliminary data indicated that relamorelin and prucalopride are novel candidates that have proven to be effective and safe. Future RCTs should be conducted based on unified guidelines using universal diagnostic modalities to reveal reliable and comprehensive outcomes.

Diabetic Gastroparesis and Glycaemic Control

PURPOSE OF REVIEW

Gastroparesis is an important complication of diabetes that may have a major impact on the quality of life as a result of upper gastrointestinal symptoms and impaired glycaemic control. Current management strategies include optimising blood glucose control, dietary modifications and supportive nutrition. Pharmacologic approaches with drugs that have prokinetic and/or antiemetic effects are also used widely; however, current available treatments have major limitations. There is increasing recognition that the rate of gastric emptying (GE) is a key determinant of the glycaemic response to a meal.

RECENT FINDINGS

There is ongoing uncertainty regarding the impact of longstanding hyperglycaemia on GE, which requires clarification. New diagnostic techniques have been developed to better characterise the mechanisms underlying gastroparesis in individual patients, and these have the potential to lead to more personalised therapy. Management of gastroparesis is complex and suboptimal; novel approaches are desirable. This review summarises recent advances in the understanding of diabetic gastroparesis, with an emphasis on the current therapies that influence GE, and the bidirectional relationship between glycaemic control and GE.

Revisiting the physiology of nausea and vomiting-challenging the paradigm

PURPOSE

The predominant neurotransmitters and receptors for acute and delayed chemotherapy-induced nausea and vomiting (CINV) are represented in the current paradigm, which reflects successful control of emesis. However, control of nausea (N) lags behind management of vomiting (V). This review aims to re-examine and incorporate new information about the mechanisms of V and N.

METHODS

The initial literature search focused on CINV. Keywords in articles led to subsequent discovery of publications focused on N&V in other medical and scientific fields (e.g., gastroenterology, neurology, cannabinoid science, neuropharmacology, and motion sickness). Using keywords to identify other sources continued until no further recent, meaningful publications were found.

RESULTS

More than 86% of references were from recent non-oncology journals and books, suggesting there are many areas for cross-fertilization research into mechanisms and management of N&V-particularly of N, which involves overlapping and dissimilar CNS areas from V. Information from cited articles was incorporated into visual representation of N&V, which is certainly not exhaustive but supports highly complex processes in the stomach and gut, the vagus nerve and spinal cord neurons, the nucleus tractus solitarii, and the anterior insular cortex and anterior cingulate cortex with input from the amygdala.

CONCLUSIONS

These data support the idea that mechanisms for N, whatever the cause, must be highly similar. Continued research into nausea, including patient-reported evaluation and outcomes, is important; interventions for nausea could be considered adjuvants to current standard of care antiemetics and be individualized, depending on patient-reported efficacy and adverse effects and preferences.

MECHANISMS IN ENDOCRINOLOGY: Anorexia nervosa and endocrinology: a clinical update

Anorexia nervosa is a syndrome, that is collections of symptoms, which is not defined by its etiology. The severe cases are intractable. The syndrome is associated with multiple, profound endocrine alterations which may be adaptive, reactive or etiologic. Adaptive changes potentially may be inappropriate in clinical settings such as inpatient intensive re-nutrition or in a setting with somatic comorbidity. Electrolyte levels must be closely monitored during the refeeding process, and the need for weight gain must be balanced against potentially fatal refeeding complications. An important focus of clinical research should be to identify biomarkers associated with different stages of weight loss and re-nutrition combined with psychometric data. Besides well-established peripheral endocrine actions, several hormones also are released directly to different brain areas, where they may exert behavioral and psychogenic actions that could offer therapeutic targets. We need reliable biomarkers for predicting outcome and to ensure safe re-nutrition, however, first of all we need them to explore the metabolism in anorexia nervosa to open new avenues with therapeutic targets. A breakthrough in our understanding and treatment of this whimsical disease remains. Considering this, the aim of the present review is to provide an updated overview of the many endocrine changes in a clinical perspective.

Glass half empty? Lessons learned about gastroparesis

Gastroparesis is defined as a combination of chronic dyspeptic symptoms and delayed emptying of a solid test meal. It remains a difficult-to-treat disorder with a significant impact on quality of life. Although gastroparesis is defined by delayed emptying, several important studies did not find a correlation between this biomarker and symptom severity or treatment success. Thus, some of the more recent trials explored strategies that ranged from antiemetics to antidepressants. Although dietary management showed benefit, most of the other interventions were barely superior to placebo or were not superior at all. Placebo responses were often quite high and this complicates the assessment of active agents. While it complicates the design and interpretation of clinical trials, high response rates for active and sham interventions indicate that we can achieve symptom relief in many patients and thus give them some reassurance. If indeed most therapies are only marginally better than placebo, the differences in adverse effects should be weighed more strongly, a point that is especially important in view of the controversy surrounding metoclopramide. Mechanistic studies introduced the network of macrophages as another potentially important player in the development of gastroparesis. Results are too preliminary and are largely based on preclinical data but show up- and downregulation of cellular elements controlling gastric function. Thus, future developments may teach us how they interfere with some of these mechanisms in clinical settings, potentially making gastroparesis a reversible process.

The Investigation and Treatment of Diabetic Gastroparesis

PURPOSE

This review provides an update on the investigations and treatment options for gastroparesis.

METHODS

A comprehensive literature search of Medline, PubMed, Embase and OVID was conducted which included all systematic reviews and research articles that focused on the diagnosis, investigations and management diabetic gastroparesis.

FINDINGS

Dietary modifications and pharmacologic treatment with prokinetics to increase gastric motility form the mainstay of treatment. However, the use of prokinetics is limited by adverse effects and serious adverse effects, leaving metoclopramide as the only drug approved by the US Food and Drug Administration for the treatment of gastroparesis. Newer therapies, including motilin receptor agonists, ghrelin receptor agonists, and neurokinin receptor antagonists, are currently being investigated. Transpyloric stenting, gastric electrical stimulation, and gastric per-oral endoscopic myotomy provide mechanical options for intervention, and surgical interventions in severe intractable gastroparesis include laparoscopic pyloroplasty or gastrectomy.

IMPLICATIONS

Advances to better understand the pathophysiology and management of diabetic gastroparesis have been limited, especially with discordance between symptoms and severity of delay in gastric emptying. Established treatment options are limited; however, recent pharmacologic and surgical interventions show promise.

Elevated circulating ghrelin in patients with COPD: A meta-analysis

Ghrelin, an endogenous ligand for growth hormone secretagogue receptor, has been implicated in chronic obstructive pulmonary disease (COPD). Recently, several studies reported inconsistent levels of ghrelin in plasma/serum of COPD patients. This meta-analysis aims to determine the circulating level of ghrelin in COPD. Published case–control or cohort studies were retrieved from Pubmed and Embase databases. Pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated in a random-effects model. Nine studies involving 515 subjects were included. Pooled effect size showed that circulating ghrelin levels were significantly enhanced in COPD patients compared with those in controls (SMD: 0.83, 95% CI: 0.04 to 1.62, p = 0.039). Noticeably, five studies stratified for body mass index in COPD group and we further found ghrelin levels were significantly higher in underweight COPD patients than those in normal weight cases (SMD: 1.52, 95% CI: 0.43 to 2.61, p = 0.006). However, no significant difference regarding ghrelin levels was indicated between normal weight COPD and controls (SMD: 0.64, 95% CI: −0.36 to 1.63, p = 0.210). In this meta-analysis, circulating level of ghrelin is significantly elevated in patients with COPD, especially in those underweight, indicating supplement with exogenous ghrelin could be a therapeutic choice for underweight COPD patients.

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.

Therapeutic Potential of Targeting the Ghrelin Pathway

Ghrelin was discovered in 1999 as the endogenous ligand of the growth-hormone secretagogue receptor 1a (GHSR1a). Since then, ghrelin has been found to exert a plethora of physiological effects that go far beyond its initial characterization as a growth hormone (GH) secretagogue. Among the numerous well-established effects of ghrelin are the stimulation of appetite and lipid accumulation, the modulation of immunity and inflammation, the stimulation of gastric motility, the improvement of cardiac performance, the modulation of stress, anxiety, taste sensation and reward-seeking behavior, as well as the regulation of glucose metabolism and thermogenesis. Due to a variety of beneficial effects on systems’ metabolism, pharmacological targeting of the endogenous ghrelin system is widely considered a valuable approach to treat metabolic complications, such as chronic inflammation, gastroparesis or cancer-associated anorexia and cachexia. The aim of this review is to discuss and highlight the broad pharmacological potential of ghrelin pathway modulation for the treatment of anorexia, cachexia, sarcopenia, cardiopathy, neurodegenerative disorders, renal and pulmonary disease, gastrointestinal (GI) disorders, inflammatory disorders and metabolic syndrome.

From Belly to Brain: Targeting the Ghrelin Receptor in Appetite and Food Intake Regulation

Ghrelin is the only known peripherally-derived orexigenic hormone, increasing appetite and subsequent food intake. The ghrelinergic system has therefore received considerable attention as a therapeutic target to reduce appetite in obesity as well as to stimulate food intake in conditions of anorexia, malnutrition and cachexia. As the therapeutic potential of targeting this hormone becomes clearer, it is apparent that its pleiotropic actions span both the central nervous system and peripheral organs. Despite a wealth of research, a therapeutic compound specifically targeting the ghrelin system for appetite modulation remains elusive although some promising effects on metabolic function are emerging. This is due to many factors, ranging from the complexity of the ghrelin receptor (Growth Hormone Secretagogue Receptor, GHSR-1a) internalisation and heterodimerization, to biased ligand interactions and compensatory neuroendocrine outputs. Not least is the ubiquitous expression of the GHSR-1a, which makes it impossible to modulate centrally-mediated appetite regulation without encroaching on the various peripheral functions attributable to ghrelin. It is becoming clear that ghrelin’s central signalling is critical for its effects on appetite, body weight regulation and incentive salience of food. Improving the ability of ghrelin ligands to penetrate the blood brain barrier would enhance central delivery to GHSR-1a expressing brain regions, particularly within the mesolimbic reward circuitry.

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.

Dose-dependent effect of ghrelin on gastric emptying in rats and the related mechanism of action

The aim of this study was to investigate the dose-dependent effect of ghrelin on gastric emptying in rats and the related mechanism of action. Sixty Wistar rats were randomized into control and test groups, which respectively received intraperitoneal injection of normal saline and ghrelin at different doses (0.5 nmol/kg, 1.0 nmol/kg, 1.5 nmol/kg, 2.0 nmol/kg, and 2.5 nmol/kg). After 45 minutes, all rats were gavaged with semisolid paste. The gastric emptying rate was determined 30 minutes later, and the plasma cholecystokinin level was tested by radioimmunoassay. The mean gastric emptying rate in the test groups was significantly higher than in the control group (38.24 ± 7.15% and 27.18 ± 2.37%, respectively, p < 0.05). Medium and high doses of ghrelin (1.0 nmol/kg, 1.5 nmol/kg, 2.0 nmol/kg, and 2.5 nmol/kg), but not low dose (0.5 nmol/kg), accelerated the gastric emptying. In addition, the plasma cholecystokinin level in the test groups was significantly higher than in the control group (p < 0.01). The gastric emptying rate was positively correlated with the plasma cholecystokinin level (p < 0.01). Intraperitoneal injection of ghrelin at medium and high doses significantly accelerated gastric emptying in rats.

Pharmacological, Pharmacokinetic, and Pharmacogenomic Aspects of Functional Gastrointestinal Disorders

This article reviews medications commonly used for the treatment of patients with functional gastrointestinal disorders. Specifically, we review the animal models that have been validated for the study of drug effects on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of new drugs; the biomarkers that are validated for studies of sensation and motility endpoints with experimental medications in humans; the pharmacogenomics applied to these medications and their relevance to the FGIDs; and the pharmacology of agents that are applied or have potential for the treatment of FGIDs, including psychopharmacologic drugs.

Current and Emerging Medical Therapies for Gastroparesis

OPINION STATEMENT

Gastroparesis likely involves various pathophysiological disorders and is increasingly prevalent as complications of surgeries, medications, and chronic diabetes. Key to diagnosis is evidence of delayed gastric emptying, generally based on standardized scintigraphy, and ruling out distal obstruction or other dysmotilities. Initial medical management includes reviewing potentially exacerbating medications and ruling out other reversible causes, achieving tighter glucose control in diabetics, and implementing dietary and lifestyle changes. While current available medications are limited, symptomatic control is aimed at improving gastric emptying, alleviating nausea and vomiting, and treating associated abdominal pain. Other potential therapies are aimed at reducing acid production, improving gastric accommodation or pyloric dysfunction, and treating bacterial overgrowth. Future studies should be aimed toward identification of subpopulations of gastroparetics who are better responders to the various medications based on differences in underlying pathophysiology and adopting standardized study end point measures that may allow for comparisons across trials. This chapter will review current treatment options, upcoming promising medications, and some of the hurdles in advancing the field forward.

Efficacy of Gum Chewing on Bowel Movement After Open Colectomy for Left-Sided Colorectal Cancer: A Randomized Clinical Trial

BACKGROUND

Prolonged intestinal paralysis can be a problem after gastrointestinal surgery. Several systematic reviews and meta-analyses have suggested the efficacy of gum chewing for the prevention of postoperative ileus.

OBJECTIVE

The purpose of this study was to examine the efficacy of gum chewing for the recovery of bowel function after surgery for left-sided colorectal cancer and to determine the physiological mechanism underlying the effect of gum chewing on bowel function.

DESIGN

This was a single-center, placebo-controlled, parallel-group, prospective randomized trial.

SETTINGS

The study was conducted at a general hospital in Japan.

PATIENTS

Forty-eight patients with left-sided colorectal cancer were included.

INTERVENTIONS

The patients were randomly assigned to a gum group (N = 25) and a control group (N = 23). Four patients in the gum group and 1 in the control group were subsequently excluded because of difficulties in continuing the trial, resulting in the analysis of 21 and 22 patients in the respective groups. Patients in the gum group chewed commercial gum 3 times a day for ≥5 minutes each time from postoperative day 1 to the first day of food intake.

MAIN OUTCOME MEASURES

The time to first flatus and first bowel movement after the operation were recorded, and the colonic transit time was measured. Gut hormones (gastrin, des-acyl ghrelin, motilin, and serotonin) were measured preoperatively, perioperatively, and on postoperative days 1, 3, 5, 7, and 10.

RESULTS

Gum chewing did not significantly shorten the time to the first flatus (53 ± 2 vs. 49 ± 26 hours; p = 0.481; gum vs. control group), time to first bowel movement (94 ± 44 vs. 109 ± 34 hours; p = 0.234), or the colonic transit time (88 ± 28 vs. 88 ± 21 hours; p = 0.968). However, gum chewing significantly increased the serum levels of des-acyl ghrelin and gastrin.

LIMITATIONS

The main limitation was a greater rate of complications than anticipated, which limited the significance of the findings.

CONCLUSIONS

Gum chewing changed the serum levels of des-acyl ghrelin and gastrin, but we were unable to demonstrate an effect on the recovery of bowel function.

Therapeutic applications of ghrelin agonists in the treatment of gastroparesis

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.

The treatment of gastroparesis, constipation and small intestinal bacterial overgrowth syndrome in patients with Parkinson's disease

INTRODUCTION

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.

AREAS COVERED

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.

EXPERT OPINION

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.

Gastroparesis: A Review of Current Diagnosis and Treatment Options

Gastroparesis (GP) is a chronic neuromuscular disorder of the upper gastrointestinal tract. The incidence of GP is not well described; however, the number of individuals affected by symptoms of GP in the United States is estimated to be over 4 million. The etiology of GP is diverse. Approximately 25% of cases are associated with diabetes, whereas nearly 50% are classified as idiopathic; many of these latter cases likely represent a postinfectious process. Connective tissue disorders, autoimmune disorders, prior gastric surgery, ischemia, and medications make up the vast majority of the remaining cases. The pathophysiology of GP is also diverse. Abnormalities in fundic tone, antroduodenal dyscoordination, a weak antral pump, gastric dysrhythmias, and abnormal duodenal feedback all contribute to delays in gastric emptying and symptom expression. Characteristic symptoms of GP include nausea, vomiting, epigastric pain, early satiety, and weight loss. The diagnosis of GP is made using a combination of characteristic symptoms in conjunction with objective evidence of delayed gastric emptying in the absence of mechanical obstruction. Once the diagnosis is made, treatment options include dietary modification, medications to accelerate gastric emptying, antiemetic agents, gastric electrical stimulation, and surgery. In the following sections we will provide an overview of the health care impact of GP, describe the underlying pathophysiology, and review treatment options using an evidence-based approach.

Peripheral mechanisms in appetite regulation

Peripheral mechanisms in appetite regulation include the motor functions of the stomach, such as the rate of emptying and accommodation, which convey symptoms of satiation to the brain. The rich repertoire of peripherally released peptides and hormones provides feedback from the arrival of nutrients in different regions of the gut from where they are released to exert effects on satiation, or regulate metabolism through their incretin effects. Ultimately, these peripheral factors provide input to the highly organized hypothalamic circuitry and vagal complex of nuclei to determine cessation of energy intake during meal ingestion, and the return of appetite and hunger after fasting. Understanding these mechanisms is key to the physiological control of feeding and the derangements that occur in obesity and their restoration with treatment (as shown by the effects of bariatric surgery).

Emerging drugs for functional dyspepsia

INTRODUCTION

Functional dyspepsia (FD) is a relatively common gastrointestinal clinical condition that remains poorly understood. Controversies remain regarding the definition, pathophysiology and optimum treatment. The current treatment of FD is limited and no established regimen is available.

AREAS COVERED

Recent advances have improved our understanding of the pathophysiology of the disease and have led to the development of newer tailored therapies. Novel agents such as the motilin receptor agonist camicinal and the muscarinic M1 and M2 receptor antagonist acotiamide appear promising; however, the need for a safe and efficacious treatment remains largely unmet. This review describes the currently available management options for FD and critically evaluates emerging therapies.

EXPERT OPINION

The optimal treatment for FD is yet to be determined. A proton pump inhibitor or a prokinetic agent constitutes primary treatment. Helicobacter pylori testing and eradication is recommended. Based on currently available data, acotiamide appears promising, particularly in postprandial distress syndrome. Further large-scale multicentered trials are required to define the duration of treatment and the side-effect profile.

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.

Relationship between ghrelin and abnormal gastric emptying in diabetes mellitus

In recent years, the morbidity of diabetes mellitus has increased rapidly in the world, and the harm of complications of diabetes mellitus has ranked third after cancer and cardiovascular and cerebrovascular diseases. Abnormal gastric emptying is one of the common complications of diabetic mellitus, which seriously influences the life quality of the patients. Therefore, it is important to investigate the pathogenesis of abnormal gastric emptying in diabetes mellitus. The role of ghrelin in the pathophysiology of abnormal gastric emptying in diabetes mellitus is a hot area of research now. In this paper, we review the relationship between ghrelin and abnormal gastric emptying in diabetes mellitus.

Combination of symptoms, syndrome and disease: Treatment of refractory diabetic gastroparesis

AIM: To assess effect of combination of symptoms, syndrome and disease on treatment of diabetic gastroparesis with severe nausea and vomiting.

METHODS: Professor Tong Xiaolin’s clinical electronic medical records of patients who were treated between January 1, 2006 and October 1, 2012 were used as a database. Patients who met the inclusion criteria were enrolled. General information (name, sex and age), symptoms and blood glucose levels were obtained from the clinic electronic medical record, which was supplemented by a telephone interview. The patient-rated Gastroparesis Cardinal Symptom Index (GCSI) was used to evaluate the severity of the symptoms of gastroparesis. The effects of the treatment were assessed by the change in the severity of the symptoms of gastroparesis and the change in blood glucose between the baseline levels and the post-treatment levels at 1, 2, 4, 8 and 12 wk.

RESULTS: Forty-five patients had a mean GCSI nausea and vomiting severity score of 4.21 ± 0.67 and a total GCSI score of 2.77 ± 0.63 before treatment. There was a significant improvement in the nausea and vomiting score at every return visit compared with the baseline score (1 wk: 3.02 ± 1.04 vs 4.18 ± 0.71, P < 0.001; 2 wk: 2.32 ± 1.25 vs 4.16 ± 0.73, P < 0.001; 4 wk: 2.12 ± 1.26 vs 4.12 ± 0.73, P < 0.001; 8 wk: 1.79 ± 1.09 vs 4.24 ± 0.77, P < 0.001; 12 wk: 0.69 ± 0.92 vs 4.25 ± 0.70, P < 0.001). Twenty-five of the 45 patients had complete resolution of vomiting during the observation period (mean time to resolution was 37.9 ± 27.3 d). The postprandial fullness and early satiety subscale, bloating subscale and total GCSI scores were also improved. Finally, the blood glucose levels improved after treatment, although the change was not significant.

CONCLUSION: Use of the combination of symptoms, syndrome and disease to treat diabetic gastroparesis with refractory nausea and vomiting may be a new treatment option.

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.

Treatment of refractory diabetic gastroparesis: Western medicine and traditional Chinese medicine therapies

Refractory diabetic gastroparesis (DGP), a disorder that occurs in both type 1 and type 2 diabetics, is associated with severe symptoms, such as nausea and vomiting, and results in an economic burden on the health care system. In this article, the basic characteristics of refractory DGP are reviewed, followed by a discussion of therapeutic modalities, which encompasses the definitions and clinical manifestations, pathogenesis, diagnosis, and therapeutic efficacy evaluation of refractory DGP. The diagnostic standards assumed in this study are those set forth in the published literature due to the absence of recognized diagnosis criteria that have been assessed by an international organization. The therapeutic modalities for refractory DGP are as follows: drug therapy, nutritional support, gastric electrical stimulation, pyloric botulinum toxin injection, endoscopic or surgical therapy, and traditional Chinese treatment. The therapeutic modalities may be used alone or in combination. The use of traditional Chinese treatments is prevalent in China. The effectiveness of these therapies appears to be supported by preliminary evidence and clinical experience, although the mechanisms that underlie these effects will require further research. The purpose of this article is to explore the potential of combined Western and traditional Chinese medicine treatment methods for improved patient outcomes in refractory DGP.

Emerging drugs for the treatment of gastroparesis

INTRODUCTION

Gastroparesis presents with symptoms of gastric retention with findings of delayed gastric emptying on diagnostic testing. Manifestations of gastroparesis are disabling in severe cases and lead to significant health resource utilization. Current therapies often are ineffective, may exhibit tolerance on chronic administration or produce prominent side effects in large patient subsets.

AREAS COVERED

This review assessed literature on drugs with theoretical efficacy in gastroparesis including medications that accelerate gastric emptying, reduce nausea and vomiting, or act as neuromodulators to reduce gastric sensitivity. Numerous agents exhibit diverse actions to modify gastric sensorimotor function in animal models; however, few medications are in controlled testing in gastroparesis. Prokinetic drugs with promise for this condition include investigational serotonin 5-HT4 agonists, motilin agonists, dopamine D2 antagonists, ghrelin agonists and an agent with combined muscarinic antagonist and acetylcholinesterase inhibitory effects. Other antiemetics and complementary and alternative formulations may be effective for some symptoms.

EXPERT OPINION

Development of effective novel therapies of gastroparesis without the neurotoxicity and cardiac arrhythmogenic effects of current agents will mandate a better definition of the gastric and extragastric factors responsible for the pathogenesis of the varied clinical manifestations of this disorder.

Diabetic gastroparesis: functional/morphologic background, diagnosis, and treatment options

The regulation of gastrointestinal motility mainly involves the smooth muscle, neural (extrinsic and intrinsic), and hormonal elements, the glial cells, and the interstitial cells of Cajal. An orchestrated function of all these components is required for the appropriate propulsive movement of the food in the gastrointestinal tract. Gastroparesis, a pathological slowing-down of gastric emptying, is a result of the damage to the tissue elements involved in the regulation of motility. Gastroparesis is one of the well-known complications of long-standing diabetes mellitus. Although it is rarely a life-threatening complication, it has a deteriorating effect on the quality of life, leads to unpredictable oscillation of the blood glucose level, and increases the time required for the absorption of food and medicines. This review describes the clinical characteristics of diabetic gastroparesis and summarizes the organic and functional motility abnormalities caused by this complication. Finally, the currently available and potential future therapeutic approaches are summarized.

A ghrelin agonist fails to show benefit in patients with diabetic gastroparesis: let's not throw the baby out with the bath water

Ghrelin is the endogenous ligand for the growth hormone secretagogue-1a receptor and is a potential target for treatment of gastroparesis. This viewpoint assesses the potential role of ghrelin agonists in the treatment of gastroparesis through a review of the early phase, randomized, controlled trials of ghrelin agonists in patients with diabetes and, either, delayed gastric emptying at the time of the trial or symptoms at the time of the trial, and prior documentation of delayed gastric emptying of solids. Whereas recent experience with ghrelin agonists that have a macrocycle structure (TZP-101, TZP-102) has not confirmed earlier promising results, there is little evidence that ghrelin receptors downregulate with repeated treatment, in contrast to motilin receptors. Phase IIa clinical trials performed with a different agent (RM-131, which is a small molecule ghrelin agonist) suggest that, as a class, ghrelin agonists may be efficacious in stimulating gastric emptying. It is premature to dismiss ghrelin agonists as potential therapies for gastroparesis.

Phase 2b, randomized, double-blind 12-week studies of TZP-102, a ghrelin receptor agonist for diabetic gastroparesis

BACKGROUND

TZP-102, a potent, oral, ghrelin receptor agonist, improved diabetic gastroparesis symptoms in Phase 2a.

METHODS

Patients with type 1 or 2 diabetes, delayed gastric half-emptying (T(1/2)), and ≥3 months gastroparesis symptoms randomized 1 : 1 : 1 to double-blind placebo, 10-mg, or 20-mg TZP-102 once daily for 12 weeks (Study TZP-102-CL-G003). Study TZP-102-CL-G004 patients randomized 1 : 1 to 10-mg TZP-102:placebo three-times-daily. Primary endpoint was change-from-baseline through Weeks 11-12 in Daily Diary of Gastroparesis Symptoms Questionnaire (GSDD) via electronic Patient Recorded Outcome device: worst severity of nausea, early satiety, bloating, and upper abdominal pain in 24 h (0 = none-to-5 = very severe). GSDD Composite Score for eligibility was ≥2.5 (Day-14-to-baseline). Patient Overall Treatment Evaluation (OTE) provided an anchor-based minimal clinically important difference (MCID) for GSDD Composite Score.

KEY RESULTS

Study TZP-102-CL-G003 enrolled 201 outpatients: females 72%; Caucasians 87%; type 2 diabetes 61%; insulin-dependent 65%; age mean ± SD 53 ± 11.3 years; HbA1c 7.8 ± 1.5%; GCSI 3.4 ± 0.7; GSDD Composite 3.6 ± 0.6; gastric T1/2 131 ± 32 min; n = 69 (10-mg), n = 66 (20-mg), n = 66 (placebo). Primary endpoint (GSDD): significant improvement in all arms, although not for TZP-102 vs placebo: mean change-from-baseline -1.7, -1.4, -1.5 (10-mg, 20-mg, placebo); Gastroparesis Cardinal Symptom Index -1.8, -1.6, -1.5, respectively. The OTE (all patients) at Week-12 was: Patient 3.7 ± 3.2 and Physician 3.6 ± 3.0 with median score for both of 5.0 = important on scale of improvement; individual MCID was 1.61 and 0.94 for group analyses, greater than expected. Study TZP-102-CL-G004 with similar demographic/disease characteristics was prematurely terminated for efficacy futility (n = 64 with Week-4 assessments).

CONCLUSIONS & INFERENCES

Efficacy of TZP-102 was not demonstrated compared with placebo in diabetic gastroparesis; however, there was substantial symptom improvement in all arms (ClinicalTrials.gov NCT01452815/NCT01664637).

The ghrelin agonist RM-131 accelerates gastric emptying of solids and reduces symptoms in patients with type 1 diabetes mellitus

BACKGROUND & AIMS

RM-131, a synthetic ghrelin agonist, greatly accelerates gastric emptying of solids in patients with type 2 diabetes and delayed gastric emptying (DGE). We investigated the safety and effects of a single dose of RM-131 on gastric emptying and upper gastrointestinal (GI) symptoms in patients with type 1 diabetes and previously documented DGE.

METHODS

In a double-blind cross-over study, 10 patients with type 1 diabetes (age, 45.7 ± 4.4 y; body mass index, 24.1 ± 1.1 kg/m(2)) and previously documented DGE were assigned in random order to receive a single dose of RM-131 (100 μg, subcutaneously) or placebo. Thirty minutes later, they ate a radiolabeled solid-liquid meal containing EggBeaters (ConAgra Foods, Omaha, NE), and then underwent 4 hours of gastric emptying and 6 hours of colonic filling analyses by scintigraphy. Upper GI symptoms were assessed using a daily diary, gastroparesis cardinal symptom index (total GCSI-DD) and a combination of nausea, vomiting, fullness, and pain (NVFP) scores (each rated on a 0-5 scale).

RESULTS

At screening, participants' mean level of hemoglobin A1c was 9.1% ± 0.5%; their total GCSI-DD score was 1.66 ± 0.38 (median, 1.71), and their total NVFP score was 1.73 ± 0.39 (median, 1.9). The t1/2 of solid gastric emptying was 84.9 ± 31.6 minutes when subjects were given RM-131 and 118.7 ± 26.7 when they were given a placebo. The median difference (Δ)was 33.9 minutes (interquartile range [IQR] -12, -49), or -54.7% (IQR, -21%,-110%). RM-131 decreased gastric retention of solids at 1 hour (P = .005) and 2 hours (P = .019). Numeric differences in t1/2 for gastric emptying of liquids, solid gastric emptying lag time, and colonic filling at 6 hours were not significant. Total GCSI-DD scores were 0.79 on placebo (IQR, 0.75, 2.08) and 0.17 on RM-131 (IQR, 0.00, 0.67; P = .026); NVFP scores were lower on RM-131 (P = .041). There were no significant adverse effects.

CONCLUSIONS

RM-131 significantly accelerates gastric emptying of solids and reduces upper GI symptoms in patients with type 1 diabetes and documented DGE.

Neurochemical mechanisms and pharmacologic strategies in managing nausea and vomiting related to cyclic vomiting syndrome and other gastrointestinal disorders

Nausea and vomiting are common gastrointestinal complaints which could be triggered by stimuli in both the peripheral and central nervous systems. They may be considered as defense mechanisms when threatening toxins/agents enter the gastrointestinal tract or there is excessive retention of gastrointestinal contents due to obstruction. The pathophysiology of nausea and vomiting is complex and much still remains unknown. Therefore, treatments are restricted or ineffective in many cases. Nausea and vomiting with functional etiologies including cyclic vomiting syndrome are challenging in gastroenterology. In this article, we review potential pathways, neurochemical transmitters, and their receptors which are possibly involved in the pathophysiology of nausea and vomiting including the entity cyclic vomiting syndrome.

Pharmacological agents currently in clinical trials for disorders in neurogastroenterology

Esophageal, gastrointestinal, and colonic diseases resulting from disorders of the motor and sensory functions represent almost half the patients presenting to gastroenterologists. There have been significant advances in understanding the mechanisms of these disorders, through basic and translational research, and in targeting the receptors or mediators involved, through clinical trials involving biomarkers and patient responses. These advances have led to relief of patients' symptoms and improved quality of life, although there are still significant unmet needs. This article reviews the pipeline of medications in development for esophageal sensorimotor disorders, gastroparesis, chronic diarrhea, chronic constipation (including opioid-induced constipation), and visceral pain.

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.

Treatments for severe gastroparesis

Severe gastroparesis is a kind of gastroparesis that is refractory to conventional drug therapy and requires nutritional support and frequently emergency hospitalization. The selection of treatment for severe gastroparesis has always been a dilemma for clinicians. Currently, there have been limited reports on the treatment of severe gastroparesis. This article sums up the primary treatments, drug treatments and other kinds of treatments for severe gastroparesis and discusses the prospects for the treatment of this refractory disease.

Ghrelin signaling in the gut, its physiological properties, and therapeutic potential

BACKGROUND

Ghrelin, an orexigenic hormone secreted from the stomach, was soon after its discovery hypothesized to be a prokinetic agent, due to its homology to motilin. Studies in animals and humans, using ghrelin and ghrelin receptor agonists, confirmed this hypothesis, suggesting a therapeutic potential for the ghrelin receptor in the treatment of gastrointestinal motility disorders. Precilinical studies demonstrated that ghrelin can act directly on ghrelin receptors on the enteric nervous system, but the predominant route of action under physiological circumstances is signaling via the vagus nerve in the upper gastrointestinal tract and the pelvic nerves in the colon. Different pharmaceutical companies have designed stable ghrelin mimetics that revealed promising results in trials for the treatment of diabetic gastroparesis and post-operative ileus. Nevertheless, no drug was able to reach the market so far, facing problems proving superiority over placebo treatment in larger trials.

PURPOSE

This review aims to summarize the road that led to the current knowledge concerning the prokinetic properties of ghrelin with a focus on the therapeutic potential of ghrelin receptor agonists in the treatment of hypomotility disorders. In addition, we outline some of the problems that could be at the basis of the negative outcome of the trials with ghrelin agonists and question whether the right target groups were selected. It is clear that a new approach is needed to develop marketable drugs with this class of gastroprokinetic agents.

Gastrointestinal complications of diabetes mellitus

Diabetes mellitus affects virtually every organ system in the body and the degree of organ involvement depends on the duration and severity of the disease, and other co-morbidities. Gastrointestinal (GI) involvement can present with esophageal dysmotility, gastro-esophageal reflux disease (GERD), gastroparesis, enteropathy, non alcoholic fatty liver disease (NAFLD) and glycogenic hepatopathy. Severity of GERD is inversely related to glycemic control and management is with prokinetics and proton pump inhibitors. Diabetic gastroparesis manifests as early satiety, bloating, vomiting, abdominal pain and erratic glycemic control. Gastric emptying scintigraphy is considered the gold standard test for diagnosis. Management includes dietary modifications, maintaining euglycemia, prokinetics, endoscopic and surgical treatments. Diabetic enteropathy is also common and management involves glycemic control and symptomatic measures. NAFLD is considered a hepatic manifestation of metabolic syndrome and treatment is mainly lifestyle measures, with diabetes and dyslipidemia management when coexistent. Glycogenic hepatopathy is a manifestation of poorly controlled type 1 diabetes and is managed by prompt insulin treatment. Though GI complications of diabetes are relatively common, awareness about its manifestations and treatment options are low among physicians. Optimal management of GI complications is important for appropriate metabolic control of diabetes and improvement in quality of life of the patient. This review is an update on the GI complications of diabetes, their pathophysiology, diagnostic evaluation and management.

The role of ghrelin in patients with functional dyspepsia and its potential clinical relevance (Review)

Functional dyspepsia (FD) is a functional gastrointestinal disorder (FGID). According to the Rome III consensus, FD is divided into 2 subgroups: epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS). Although multiple mechanisms of FD pathogenesis have been suggested, its underlying etiology and pharmacological therapy remain unclear. Ghrelin is a gut-derived peptide found in the stomach. It plays a role in the regulation of gastric motility and appetite. The ghrelin gene encodes 3 molecular forms, acyl ghrelin, des-acyl ghrelin and obestatin. Acyl ghrelin acts as an endogenous ligand for growth hormone secretagogue receptor; furthermore, it is orexigenic, with effects on food intake, energy homeostasis and gastrointestinal motility. Des-acyl ghrelin exerts an opposite effect to acyl ghrelin. Obestatin exerts an inhibitory effect on the motor activity of the antrum and duodenum in fed animals. These peptides exert differential effects on gut motility and food intake. The therapeutic potential of ghrelin has attracted attention due to its varied bioactivities. Certain studies have shown that total ghrelin levels are significantly lower in patients with FD compared with healthy volunteers and that the acyl ghrelin levels of patients with FD are higher compared with healthy volunteers. However, a recent study demonstrated that acyl ghrelin levels in patients with PDS were lower compared with healthy volunteers; the association between FD and other ghrelin family gene products also remains unclear. Although certain studies have demonstrated the beneficial effects of acyl ghrelin administration and its agonist in patients with FD, only a few clinical reports exist. Further studies are required in order to examine the effects of ghrelin on FD.

Recent advances in the pathophysiology and treatment of gastroparesis

Gastroparesis is a clinical disorder characterized by upper gastrointestinal symptoms related with delayed gastric emptying of solids and liquids in the absence of mechanical obstruction. Diabetes mellitus has been the most common cause of gastroparesis and idiopathic gastroparesis also accounts for a third of all chronic cases. The most important mechanisms of gastroparesis, as understood to date, are loss of expression of neuronal nitric oxide synthase and loss of the interstitial cells of Cajal. However, the pathogenesis of gastroparesis is poorly understood. There have been several studies on specific molecules related to the pathogenesis of gastroparesis. Additionally, the Gastroparesis Clinical Research Consortium of the National Institutes of Health has achieved several promising results regarding the pathophysiology of gastroparesis. As the progress in the pathophysiology of gastroparesis has been made, a promising new drug therapy has been found. The pathophysiology and drug therapy of gastroparesis are focused in this review. Until now, the real-world medication options for treatment of gastroparesis are limited. However, it is expected to be substantially improved as the pathophysiology of gastroparesis is elucidated.

Randomized controlled phase Ib study of ghrelin agonist, RM-131, in type 2 diabetic women with delayed gastric emptying: pharmacokinetics and pharmacodynamics

OBJECTIVE

To investigate the pharmacokinetics (PK), pharmacodynamics, and safety of single-dose RM-131 in type 2 diabetic patients with gastrointestinal cardinal symptoms (GCSI) and previously documented delayed gastric emptying (DGE).

RESEARCH DESIGN AND METHODS

In a randomized crossover study, 10 female patients received RM-131 (100 μg s.c.) or placebo and underwent scintigraphic gastric emptying (GE) and colonic filling at 6 h (CF6) of a solid-liquid meal administered 30 min postdosing. Adverse events, plasma glucose, and hormonal levels were assessed. GCSI daily diary (GCSI-DD) was completed during treatments. PK was assessed in this cohort and healthy volunteers (HVs).

RESULTS

At screening, HbA(1c) was 7.2 ± 0.4% (SEM) and total GCSI-DD score was 1.32 ± 0.21. RM-131 accelerated GE t(1/2) of solids (P = 0.011); mean difference (Δ) in solid GE t(1/2) was 68.3 min (95% CI 20-117) or 66.1%. There were numerical differences in GE lag time, CF6 solids, and GE t(1/2) liquids (all P < 0.14). With a significant (P < 0.014) order effect, further analysis of the first treatment period (n = 5 per group) confirmed significant RM-131 effects on GE t(1/2) (solids, P = 0.016; liquids, P = 0.024; CF6, P = 0.013). PK was similar in DGE patients and HVs. There were increases in 120-min blood glucose (P = 0.07) as well as 30-90-min area under the curve (AUC) levels of growth hormone, cortisol, and prolactin (all P < 0.02) with single-dose RM-131. Only light-headedness was reported more on RM-131.

CONCLUSIONS

RM-131 greatly accelerates the GE of solids in patients with type 2 diabetes and documented DGE. PK is similar in diabetic patients and HVs.