Randomised clinical trials: linaclotide phase 3 studies in IBS-C - a prespecified further analysis based on European Medicines Agency-specified endpoints

Modern Management of Irritable Bowel Syndrome: More Than Motility

In the treatment of irritable bowel syndrome (IBS), loperamide seems efficacious for diarrhea and ispaghula for constipation, while musculotropic spasmolytics may relieve abdominal pain. Antidepressants were found to be efficacious for abdominal pain, but their tolerance may be problematic and the therapeutic effect varied largely between trials. While meta-analyses suggest efficacy of probiotics as a group, the quality of the trials is often suboptimal and there is large variability. Lubiprostone, a chloride channel activator, and linaclotide, a guanylyl cyclase-C agonist, showed favorable effects on multiple symptoms in IBS with constipation. For IBS with diarrhea (IBS-D), the 5-HT3 receptor antagonist ramosetron showed efficacy in men and women, but is currently only approved in Japan. A multicenter study with the anti-emetic 5-HT3 receptor antagonist ondansetron showed efficacy on stool pattern in IBS-D. The poorly absorbable antibiotic rifaximin and eluxadoline, a mu opioid receptor agonist and delta antagonist, both showed efficacy in phase III trials in IBS-D and were approved by the FDA. Eluxadoline was associated with increased occurrence of sphincter of Oddi spasm and biliary pancreatitis. The non-pharmacological treatment of IBS, with dietary interventions (mainly gluten elimination and low FODMAP (fructose, oligo-, di-, monosaccharides and polyols)) has received a lot of attention lately. While responder rates vary across studies, perhaps based on regional variations in dietary intake of FODMAPs, the dietary approach seems to have acquired recognition as a valid therapeutic alternative. Long-term studies and comparative studies with pharmacotherapy, as well as elucidation of the underlying mechanisms of action, are needed.

New and emerging therapies for the treatment of irritable bowel syndrome: an update for gastroenterologists

Irritable bowel syndrome is a functional bowel disorder with gastrointestinal symptoms (e.g. abdominal pain, straining, urgency, incomplete evacuation, nausea, and bloating) that occur alongside bowel function alterations (i.e. constipation, diarrhea, or both). Patients with irritable bowel syndrome may also experience comorbid anxiety and depression. Irritable bowel syndrome is common, with a prevalence estimated between 3% and 28%, affecting patient health and quality of life. Patients with moderate or severe irritable bowel syndrome generally seek medical care, whereas those with milder symptoms may choose self-management. Most patients with irritable bowel syndrome receive outpatient care, but irritable bowel syndrome-related hospitalizations do occur. The pathophysiology of irritable bowel syndrome is multifactorial (i.e. genetics, immune components, changes in the gut microbiota, disturbances in physiologic stress response systems, and psychosocial factors). Management of irritable bowel syndrome can include lifestyle changes, dietary interventions, counseling, psychologic medication, and agents that affect gastrointestinal motility. A number of therapies have emerged in recent years with clinical trial data demonstrating efficacy and safety for patients with irritable bowel syndrome, including agents that target gastrointestinal motility (i.e. linaclotide), gastrointestinal opioid receptors (i.e. asimadoline, eluxadoline), and gut microbiota (i.e. rifaximin). Linaclotide has been shown to significantly improve stool frequency and abdominal pain compared with placebo in constipation-predominant irritable bowel syndrome (number needed to treat, 5.1). Asimadoline shows efficacy in patients with moderate-to-severe irritable bowel syndrome-related pain. Rifaximin provided adequate relief of global irritable bowel syndrome symptoms versus placebo for a significantly greater percentage of patients with diarrhea-predominant irritable bowel syndrome (p < 0.001). Management that encompasses all aspects of irritable bowel syndrome (gastrointestinal symptoms) and comorbid psychologic symptoms (e.g. anxiety or depression) is important for improving overall patient health and well-being.

GUCY2C ligand replacement to prevent colorectal cancer

Despite advances in screening and prevention strategies, colorectal cancer (CRC) remains the second-leading cause of cancer-related death in the United States. Given this continued public health burden of CRC, there is a clear need for improved disease prevention. CRC initiates and progresses over decades, canonically proceeding via a series of stepwise molecular events that turn a normal epithelium into a dysfunctional epithelium, then subsequently into an adenoma, and finally an invasive adenocarcinoma. An emerging paradigm suggests that guanylyl cyclase C (GUCY2C) functions as a tumor suppressor in the intestine, and that the loss of hormone ligands for this receptor causes epithelial dysfunction and represents an important step in the disease process. In that context, GUCY2C ligand replacement therapy has been proposed as a strategy to prevent colorectal cancer, a translational opportunity that is underscored by the recent regulatory approval of the oral GUCY2C ligand linaclotide (Linzess™, Forest Laboratories and Ironwood Pharmaceuticals, Inc.).

Histamine Receptor H1-Mediated Sensitization of TRPV1 Mediates Visceral Hypersensitivity and Symptoms in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Histamine sensitizes the nociceptor transient reporter potential channel V1 (TRPV1) and has been shown to contribute to visceral hypersensitivity in animals. We investigated the role of TRPV1 in irritable bowel syndrome (IBS) and evaluated if an antagonist of histamine receptor H1 (HRH1) could reduce symptoms of patients in a randomized placebo-controlled trial.

METHODS

By using live calcium imaging, we compared activation of submucosal neurons by the TRPV1 agonist capsaicin in rectal biopsy specimens collected from 9 patients with IBS (ROME 3 criteria) and 15 healthy subjects. The sensitization of TRPV1 by histamine, its metabolite imidazole acetaldehyde, and supernatants from biopsy specimens was assessed by calcium imaging of mouse dorsal root ganglion neurons. We then performed a double-blind trial of patients with IBS (mean age, 31 y; range, 18-65 y; 34 female). After a 2-week run-in period, subjects were assigned randomly to groups given either the HRH1 antagonist ebastine (20 mg/day; n = 28) or placebo (n = 27) for 12 weeks. Rectal biopsy specimens were collected, barostat studies were performed, and symptoms were assessed (using the validated gastrointestinal symptom rating scale) before and after the 12-week period. Patients were followed up for an additional 2 weeks. Abdominal pain, symptom relief, and health-related quality of life were assessed on a weekly basis. The primary end point of the study was the effect of ebastine on the symptom score evoked by rectal distension.

RESULTS

TRPV1 responses of submucosal neurons from patients with IBS were potentiated compared with those of healthy volunteers. Moreover, TRPV1 responses of submucosal neurons from healthy volunteers could be potentiated by their pre-incubation with histamine; this effect was blocked by the HRH1 antagonist pyrilamine. Supernatants from rectal biopsy specimens from patients with IBS, but not from the healthy volunteers, sensitized TRPV1 in mouse nociceptive dorsal root ganglion neurons via HRH1; this effect could be reproduced by histamine and imidazole acetaldehyde. Compared with subjects given placebo, those given ebastine had reduced visceral hypersensitivity, increased symptom relief (ebastine 46% vs placebo 13%; P = .024), and reduced abdominal pain scores (ebastine 39 ± 23 vs placebo 62 ± 22; P = .0004).

CONCLUSIONS

In studies of rectal biopsy specimens from patients, we found that HRH1-mediated sensitization of TRPV1 is involved in IBS. Ebastine, an antagonist of HRH1, reduced visceral hypersensitivity, symptoms, and abdominal pain in patients with IBS. Inhibitors of this pathway might be developed as a new treatment approach for IBS. ClinicalTrials.gov no: NCT01144832.

[Current issues on the treatment of chronic constipation]

Chronic constipation is a very common clinical problem with its prevalence of up to 14% in the general population. It is not a life-threatening disease, but since patient's satisfaction to the treatment is known to be as low as 50%, chronic constipation still remains a clinically challenging problem. Fortunately, many new treatments have been introduced or are to be introduced in the near future. This article will review the basic concepts and the results of recent studies on the new treatments for chronic constipation.

Bowel Disorders

Functional bowel disorders are highly prevalent disorders found worldwide. These disorders have the potential to affect all members of society, regardless of age, gender, race, creed, color or socioeconomic status. Improving our understanding of functional bowel disorders (FBD) is critical as they impose a negative economic impact to the global health care system in addition to reducing quality of life. Research in the basic and clinical sciences during the past decade has produced new information on the epidemiology, etiology, pathophysiology, diagnosis and treatment of FBDs. These important findings created a need to revise the Rome III criteria for FBDs, last published in 2006. This manuscript classifies the FBDs into five distinct categories: irritable bowel syndrome (IBS); functional constipation (FC); functional diarrhea (FDr); functional abdominal bloating/distention (FAB/D); and unspecified FBD (U-FBD). Also included in this article is a new sixth category, opioid induced constipation (OIC) which is distinct from the functional bowel disorders (FBDs). Each disorder will first be defined, followed by sections on epidemiology, rationale for changes from prior criteria, clinical evaluation, physiologic features, psychosocial features and treatment. It is the hope of this committee that this new information will assist both clinicians and researchers in the decade to come.

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.

The Pharmacology of Visceral Pain

Visceral pain describes pain emanating from the internal thoracic, pelvic, or abdominal organs. Unlike somatic pain, visceral pain is generally vague, poorly localized, and characterized by hypersensitivity to a stimulus such as organ distension. While current therapeutics provides some relief from somatic pain, drugs used for treatment of chronic visceral pain are typically less efficacious and limited by multiple adverse side effects. Thus, the treatment of visceral pain represents a major unmet medical need. Further, more basic research into the physiology and pathophysiology of visceral pain is needed to provide novel targets for future drug development. In concert with chronic visceral pain, there is a high comorbidity with stress-related psychiatric disorders including anxiety and depression. The mechanisms linking visceral pain with these overlapping comorbidities remain to be elucidated. However, persistent stress facilitates pain perception and sensitizes pain pathways, leading to a feed-forward cycle promoting chronic visceral pain disorders. We will focus on stress-induced exacerbation of chronic visceral pain and provide supporting evidence that centrally acting drugs targeting the pain and stress-responsive brain regions may represent a valid target for the development of novel and effective therapeutics.

Effective Constipation Treatment Changes More Than Bowel Frequency: A Systematic Review and Meta-Analysis

BACKGROUND/AIMS

The marketing of newer agents for treatment of constipation and irritable bowel syndrome with constipation (IBS-C) emphasize improvements in abdominal pain. However, it is not clear whether this observation reflects a unique visceral analgesic effect of these agents or is a general feature of effective laxation. We sought to determine the relationship between improvements in bowel frequency and decreases in abdominal pain in clinical trials of patients with constipation or IBS-C.

METHODS

We searched "PubMed" and "Embase" databanks for clinical trials in patients with constipation or IBS-C, targeting publications that provided detailed data on bowel movement frequency and pain intensity before and after an intervention. We abstracted the results and performed meta-analytic and meta-regression analyses.

RESULTS

Twenty-seven trials (16 constipation and 11 IBS) met entry criteria. Baseline weekly bowel movement frequency was low with 2.35 (2.07-2.64) with differences between constipation (2.00 [1.62-2.38]) and IBS-C (2.77 [2.40-3.14]; Q = 8.18; P = 0.002). Studies reported moderate pain levels (2.12 [1.81-2.42]) with comparable baseline levels in constipation (2.02 [1.63-2.42]) and IBS-C (2.35 [2.10-2.60]; Q = 1.92; P = 0.167). Treatments increased bowel frequency by 2.17 [1.88-2.47] and lowered pain ratings by 0.58 [0.49-0.68]. Meta-regression demonstrated a significant correlation between treatment-induced increases in bowel frequency and decreased pain ratings.

CONCLUSIONS

Our analysis suggests that reduction of abdominal pain observed in clinical trials of constipation and IBS-C is associated with laxation, and may not require specific drug mechanisms, thus arguing against a unique advantage of newer agents over traditional laxatives in the treatment of constipation and IBS-C.

Irritable bowel syndrome and chronic constipation: Fact and fiction

Irritable bowel syndrome (IBS) and functional constipation (FC) are the most common functional gastrointestinal disorders. According to the Rome III Criteria these two disorders should be theoretically separated mainly by the presence of abdominal pain or discomfort relieved by defecation (typical of IBS) and they should be mutually exclusive. However, many gastroenterologists have serious doubts as regards a clear separation. Both IBS-C and FC, often associated with many other functional digestive and non digestive disorders, are responsible for a low quality of life. The impact of the media on patients’ perception of these topics is sometimes disruptive, often suggesting a distorted view of pathophysiology, diagnosis and therapy. These messages frequently overlap with previous subjective opinions and are further processed on the basis of the different culture and the previous experience of the constipated patients, often producing odd, useless or even dangerous behaviors. The aim of this review was to analyze the most common patients’ beliefs about IBS-C and CC, helping physicians to understand where they should focus their attention when communicating with patients, detecting false opinions and misconceptions and correcting them on the basis of scientific evidence.

Recent Updates on the Treatment of Constipation

The treatment of constipation aims to regulate the frequency and quantity of stool in order to promote successful defecation. Numerous studies on pharmacologic treatments and non-pharmacologic therapies for constipation have attempted to overcome limitations such as temporary and insufficient efficacy. Conventional laxatives have less adverse effects and are inexpensive, but often have limited efficacy. Recently developed enterokinetic agents and intestinal secretagogues have received attention owing to their high efficacies and low incidences of adverse events. Studies on biofeedback and surgical treatment have focused on improving symptoms as well as quality of life for patients with refractory constipation.

Change in Quality of Life for Patients with Irritable Bowel Syndrome following Referral to a Gastroenterologist: A Cohort Study

BACKGROUND

Irritable bowel syndrome (IBS), a chronic functional condition, considerably reduces quality of life (QoL) and referral to gastroenterology is common. Until now, however, the impact of seeing a gastroenterologist for IBS on patients' QoL and utility has not been assessed.

METHODS

Patients referred with "probable IBS" to the Nottingham Treatment Centre between October 2012 and March 2014 were invited to complete a QoL questionnaire (EuroQol-5 Dimension) before their first appointment. Patients with confirmed IBS who completed this baseline assessment were sent follow-up questionnaires three and twelve months later. Global QoL and utility were measured at each time point and change from baseline calculated. Paired t-tests analysed the significance of any change.

RESULTS

Of 205 invited patients, 69 were eligible and recruited. Response at three and twelve months was 45% and 17% respectively. Median global QoL at baseline was 67.5 (Interquartile range [IQR] 50.0 to 80.0), with a mean increase of 3.25 (95% confidence interval [CI] -5.38 to 11.88) three months later and a mean decrease of -1.82 (95% CI -16.01 to 12.38) after one year. The median utility at baseline was 0.76 (IQR 0.69 to 0.80), with a mean increase of 0.06 (95%CI -0.01 to 0.14) at three months and no change, 0.00 (-0.16 to 0.16), after one year.

CONCLUSION

Patients experienced a small but not statistically significant increase in QoL and utility three months after seeing a gastroenterologist for IBS, which was not maintained. Gastroenterology referral does not appear to appreciably improve Qol for most people with IBS.

Systematic review: dietary fibre and FODMAP-restricted diet in the management of constipation and irritable bowel syndrome

BACKGROUND

Dietary fibre supplements have been advocated for the management of chronic constipation (CC) and irritable bowel syndrome (IBS). Recently, a fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) restricted diet has been recommended for IBS.

AIM

To systematically examine recent evidence for dietary interventions with fibre in CC and IBS and FODMAP-restricted diet in IBS, and provide recommendations.

METHODS

We searched PUBMED, MEDLINE, OVID and COCHRANE databases from 2004 to 2014. Published studies in adults with CC and IBS and constipation-predominant IBS (IBS-C) that compared fibre with placebo/alternative and FODMAP-restricted diet with alternative were included.

RESULTS

Of 550 potentially eligible clinical trials on fibre, 11 studies were found and of 23 potentially eligible studies on FODMAPs, six were found. A meta-analysis was not performed due to heterogeneity and methodological quality. Fibre was beneficial in 5/7 studies in CC and 3/3 studies in IBS-C. FODMAP-restricted diet improved overall IBS symptoms in 4/4 and IBS-C symptoms in 1/3 studies and three studies did not meet inclusion criteria. There were significant disparities in subject selection, interventions and outcome assessments in both fibre and FODMAPs studies.

CONCLUSIONS

Fibre supplementation is beneficial in mild to moderate CC and IBS-C, although larger, more rigorous and long-term RCTs are needed (Fair evidence-Level II, Grade B). Although the FODMAP-restricted diet may be effective in short-term management of selected patients with IBS (Fair evidence-Level II, Grade C) and IBS-C (Poor evidence-Level III, Grade C), more rigorous trials are needed to establish long-term efficacy and safety, particularly on colonic health and microbiome.

Linaclotide improves quality of life in patients with irritable bowel syndrome with constipation: A Meta-analysis

AIM: To perform a meta-analysis to determine the efficacy and the safety of linaclotide, compared with placebo, for patients with irritable bowel syndrome with constipation (IBS-C).

METHODS: CNKI, CBM, Wanfang, VIP, PubMed, EMBASE, clinical trials.gov and the Cochrane library were searched for randomized, placebo controlled trials examining the effect of linaclotide in adults with IBS-C. Dichotomous results were pooled by using the RevMan v.5.2 software to yield relative risks (RRs) and 95% confidence intervals (CIs).

RESULTS: The search identified three randomized controlled trials of linaclotide in patients with IBS-C published in four papers. Meta-analysis suggested that linaclotide significantly improved abdominal pain (RR = 1.58, 95%CI: 1.02-2.46), complete spontaneous bowel movements (CSBMs) (RR = 3.19, 95%CI: 2.40-4.25) and quality of life (RR = 1.38, 95%CI: 1.09-1.74). Linaclotide also improved stool form and reduced the severity of abdominal pain, bloating and overall symptoms in patients with IBS-C. Diarrhoea was the most frequent adverse event (AE) in the group of linaclotide.

CONCLUSION: Our study suggests that linaclotide significantly improves bowel function, reduces abdominal pain and improves quality of life in patients with IBS-C.

Optimal management of constipation associated with irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common chronic functional disorder of the gastrointestinal tract, meanly characterized by recurrent abdominal pain or discomfort and altered bowel habit. It is a complex disorder involving biological, environmental, and psychosocial factors. The diagnosis is achieved according to the Rome III criteria provided that organic causes have been excluded. Although IBS does not constitute a life-threatening condition, it has a remarkable prevalence and profoundly reduces the quality of life with burdening socioeconomic costs. One of the principal concerns about IBS is the lack of effective therapeutic options. Up to 40% of patients are not satisfied with any available medications, especially those suffering from chronic constipation. A correct management of IBS with constipation should evolve through a global approach focused on the patient, starting with careful history taking in order to assess the presence of organic diseases that might trigger the disorder. Therefore, the second step is to examine lifestyle, dietary habits, and psychological status. On these bases, a step-up management of disease is recommended: from fiber and bulking agents, to osmotic laxative drugs, to new molecules like lubiprostone and linaclotide. Although new promising tools for relief of bowel-movement-related symptoms are being discovered, a dedicated doctor-patient relationship still seems to be the key for success.

Advances in the management of constipation-predominant irritable bowel syndrome: the role of linaclotide

Constipation-predominant irritable bowel syndrome (IBS-C) is a commonly prevalent and clinically challenging disorder to treat. Until recently, most therapeutic agents had limited ability to address the complexity of symptoms inherent to the syndrome. The development of linaclotide provides a physiologically sound approach to treatment of the multiple symptoms of IBS-C. Clinical trials demonstrate the efficacy of linaclotide, and a platform to better understand the symptomatology of IBS-C. Based on recent clinical evidence, linaclotide should be considered for patients with IBS-C because it improves abdominal pain and bowel symptoms. In phase III trials, linaclotide met the US Food and Drug Administration responder endpoint with a number needed to treat (NNT) of 5.1-7.9, and European Medicines Agency coprimary endpoints at 12 weeks with a NNT of 4.39-7.69, and at 26 weeks with a NNT of 4.93-5.68. It is safe and effective, with diarrhea reported as the most common adverse effect, which leads to discontinuation of the medication in approximately 5% of patients.

Irritable bowel syndrome: A disease still searching for pathogenesis, diagnosis and therapy

Irritable bowel syndrome (IBS) is the most frequently diagnosed functional gastrointestinal disorder in primary and secondary care. It is characterised by abdominal discomfort, pain and changes in bowel habits that can have a serious impact on the patient’s quality of life. The pathophysiology of IBS is not yet completely clear. Genetic, immune, environmental, inflammatory, neurological and psychological factors, in addition to visceral hypersensitivity, can all play an important role, one that most likely involves the complex interactions between the gut and the brain (gut-brain axis). The diagnosis of IBS can only be made on the basis of the symptoms of the Rome III criteria. Because the probability of organic disease in patients fulfilling the IBS criteria is very low, a careful medical history is critical and should pay particular attention to the possible comorbidities. Nevertheless, the severity of the patient’s symptoms or concerns sometimes compels the physician to perform useless and/or expensive diagnostic tests, transforming IBS into a diagnosis of exclusion. The presence of alarming symptoms (fever, weight loss, rectal bleeding, significant changes in blood chemistry), the presence of palpable abdominal masses, any recent onset of symptoms in patient aged over 50 years, the presence of symptoms at night, and a familial history of celiac disease, colorectal cancer and/or inflammatory bowel diseases all warrant investigation. Treatment strategies are based on the nature and severity of the symptoms, the degree of functional impairment of the bowel habits, and the presence of psychosocial disorders. This review examines and discusses the pathophysiological aspects and the diagnostic and therapeutic approaches available for patients with symptoms possibly related to IBS, pointing out controversial issues and the strengths and weaknesses of the current knowledge.

Recent advances in pharmacological treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent functional disorder that reduces patients’ quality of life. It is a chronic disorder characterized by abdominal pain or discomfort associated with disordered defecation in the absence of identifiable structural or biochemical abnormalities. IBS imposes a significant economic burden to the healthcare system. Alteration in neurohumoral mechanisms and psychological factors, bacterial overgrowth, genetic factors, gut motility, visceral hypersensitivity, and immune system factors are currently believed to influence the pathogenesis of IBS. It is possible that there is an interaction of one or more of these etiologic factors leading to heterogeneous symptoms of IBS. IBS treatment is predicated upon the patient’s most bothersome symptoms. Despite the wide range of medications and the high prevalence of the disease, to date no completely effective remedy is available. This article reviews the literature from January 2008 to July 2013 on the subject of IBS peripherally acting pharmacological treatment. Drugs are categorized according to their administration for IBS-C, IBS-D or abdominal pain predominant IBS.

Emerging Pharmacologic Therapies for Constipation-predominant Irritable Bowel Syndrome and Chronic Constipation

Irritable bowel syndrome with constipation and chronic functional constipation are common digestive disorders that negatively impact quality of life and account for billions of dollars in health care costs. Related to the heterogeneity of pathogenesis that underlie these disorders and the failure of symptoms to reliably predict underlying pathophysiology, traditional therapies provide relief to only a subset of affected individuals. The evidence surrounding new and emerging pharmacologic treatments, which include both luminally and systemically acting drugs, is discussed here. These include agents such as lubiprostone, bile acid modulations, guanylate cyclase-C receptor agonists, serotonin receptor modulators and herbal therapies.

Linaclotide: A new drug for the treatment of chronic constipation and irritable bowel syndrome with constipation

INTRODUCTION

Linaclotide is the first member of a novel class of drugs to be extensively evaluated for the treatment of chronic constipation (CC) and irritable bowel syndrome with constipation (IBS-C).

AIM

To provide a comprehensive overview of the current state of knowledge on linaclotide, its pharmacological properties, mode of action and efficacy in clinical trials to date.

METHODS

We conducted a systematic review of the literature.

RESULTS

The survey revealed that linaclotide is a minimally absorbed, 14-amino acid peptide which acts in the intestinal lumen on guanylate cyclase-C (GC-C). This results in generation of cyclic guanosine monophosphate (cGMP), which stimulates chloride secretion, resulting in increased luminal fluid secretion and an acceleration of intestinal transit. In animal models, linaclotide also decreased visceral hypersensitivity. Linaclotide softened stool and increased transit in CC and in IBS-C. Phase II and phase III clinical studies established efficacy of linaclotide in CC (linaclotide 145 µg daily approved in the United States for CC) and in IBS-C (linaclotide 290 µg daily US Food and Drug Administration-approved for IBS-C, with favourable recommendation for the European Medicines Agency Committee for Medicinal Products for Human Use (CHMP). Linaclotide showed a favourable safety profile, and the main treatment-emerging adverse event was diarrhea, leading to discontinuation rates of up to 5%. Linaclotide is an important addition to the therapeutic possibilities for treating IBS-C and CC.

Evaluating the functional net value of pharmacologic agents in treating irritable bowel syndrome

BACKGROUND

The recent FDA provisional endpoint incorporates a one-tailed measure of improvement for IBS based on the underlying motility complaint. However, motility exists along a spectrum. Patients may experience diarrhoea resulting from therapy for their constipation-predominant IBS (IBS-C) or constipation during treatment for diarrhoea-predominant IBS (IBS-D), but still meet a unidirectional motility-based FDA endpoint.

AIM

To weigh the reported efficacy of existing therapies based on patient-reported outcomes with negative intestinal side effects in controlled clinical trial data.

METHODS

We analysed the difference between 'attributable risk' of efficacy based on number needed to treat (NNT) in the literature and percentage of adverse events (AE) of opposite intestinal complaints in placebo-controlled trials identified through a literature search of IBS trials. This calculation was coined 'functional net value' (FNV) or net benefit of the given drug.

RESULTS

For treating IBS-C, lubiprostone caused diarrhoea in excess of placebo in 3.9% of patients, leading to a FNV of 3.9 percentage units. Linaclotide caused diarrhoea in 15.3% resulting in negative FNV (-1.0 percentage unit). For IBS-D, alosetron and tricyclic anti-depressants caused constipation among a respective 16.9% and 13.0% resulting in a FNV of -3.6 and -0.5 percentage units. Among all therapies, only rifaximin did not cause the adverse event opposite the underlying motility complaint and the drug only had benefit, not detriment.

CONCLUSIONS

Functional net value (FNV) offers a method of evaluating the net benefit of a drug in IBS. Most IBS treatments have a negative effect on IBS that exceeds the benefits.

Effect of linaclotide in irritable bowel syndrome with constipation (IBS-C): a systematic review and meta-analysis

BACKGROUND

Treatment options for constipation-predominant irritable bowel syndrome (IBS-C) are limited. While linaclotide improved IBS-C symptoms in randomized controlled trials (RCTs), results vary among studies and the magnitude of benefit is unclear.

METHODS

Two investigators independently extracted data on study participants, methods and outcomes (i.e., symptoms, quality of life, and adverse events) from eligible articles i.e., RCTs comparing linaclotide with placebo in adult patients with IBS-C with a follow-up of 12 weeks or longer. The grading of recommendations assessment, development and evaluation (GRADE) methodology was used to rate the quality of evidence.

KEY RESULTS

Of 182 identified citations, three RCTs enrolling 1773 patients met the inclusion criteria. Compared with placebo, fewer patients on linaclotide failed to achieve responses i.e., FDA endpoint (1604 patients, risk ratio [RR] = 0.80; 95%CI 0.76-0.85), adequate IBS symptom relief (1773 patients, RR = 0.73; 95%CI 0.65-0.82), and clinically meaningful improvement in IBS-QOL (1659 patients, RR = 0.78; 95%CI 0.72-0.86). The incidence of diarrhea leading to discontinuation of treatment was higher for linaclotide (1773 patients, RR = 14.75; 95%CI 4.04-53.81). The quality of evidence was rated as moderate for FDA endpoint and adequate relief response, high for diarrhea, and low for IBS-QOL. Generalizability may be limited by the study population (i.e., predominantly white female patients), lack of data regarding prior therapy, and availability of few RCTs. The number of patients is insufficient to identify rare adverse events.

CONCLUSIONS & INFERENCES

Linaclotide is moderately effective in improving symptoms of IBS-C with diarrhea being the major side effect. Further studies are needed to evaluate the long-term efficacy and safety of linaclotide for IBS-C.

The safety of novel drugs used to treat irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome (IBS) is a chronic gastrointestinal (GI) disorder with a high prevalence. Besides efficacy, the safety of each drugs used to treat GI disorders is an important issue in the drug development process.

AREAS COVERED

This article reviews all Phase I to IV clinical trials or case reports with results related to the safety of novel GI drugs. The drugs are currently approved or under evaluation for approval.

EXPERT OPINION

Most of the reported adverse events were related to the GI tract with mild-to-moderate severity. Diarrhea was significantly higher versus placebo following use of linaclotide and renzapride, similar to that of constipation with ramosetron. Lubiprostone, linaclotide and rifaximin with low systemic bioavailability have less adverse events and exert more advantageous results. Asimadoline acts peripherally on κ-opioid receptors and is not associated with CNS side effects. As lubiprostone and linaclotide cause dose-dependent adverse events, starting the treatment with the lowest effective doses is advised. Ramosetron is under evaluation for diarrhea-predominant IBS due to its acceptable safety and tolerability, besides its efficacy. Rifaximin, asimadoline and renzapride are still in need of more long-term studies regarding their safety.

New pharmacological treatment options for chronic constipation

INTRODUCTION

A number of new medications were recently demonstrated to be more effective than placebo in treating chronic constipation, including the intestinal chloride channel activator lubiprostone, the prokinetic selective 5-HT4 receptor agonist prucalopride and the guanylate cyclase-C agonist linaclotide. Recent publications have also revisited traditional laxatives like PEG. Moreover, a number of pharmacological treatments are in development and these include another guanylate cyclase-C agonist, plecanatide and an ileal bile acid transporter inhibitor, elobixibat.

AREAS COVERED

This review focuses on the pharmacology, efficacy and safety profile of prucalopride, linaclotide, plecanatide and elobixibat.

EXPERT OPINION

The possible present or future clinical application of prucalopride, linaclotide, plecanatide and elobixibat in both chronic constipation and irritable bowel syndrome with constipation is reported, and some considerations on the possible role of PEG taking into account recent literature are advanced.

New treatment targets for the management of irritable bowel syndrome

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) and chronic idiopathic constipation (CIC) are highly prevalent medical conditions that reduce quality of life and represent a substantial economic burden on healthcare cost. Until recently, no specific treatment options were available. This review will provide an update of the most recent randomized clinical trials data showing efficacy and safety of novel, targeted treatment modalities in IBS and CIC with gastrointestinal receptor and ion channel agonists.

RECENT FINDINGS

Recent discoveries of peptides and small molecules targeting gastrointestinal receptors and ion channels resulted in novel, specific pharmacological therapies of IBS and CIC. The bicyclical fatty acid lubiprostone and the synthetic 14-amino acid peptide linaclotide were identified to selectively activate a Chloride Channel-2 and the Guanylin Cyclase-C receptor, respectively, and demonstrate efficacy in the treatment of IBS with constipation and CIC.

SUMMARY

Novel molecules including the bicyclical fatty acid lubiprostone and the synthetic 14-amino acid peptide linaclotide represent new treatment modalities for IBS with constipation and CIC with proven efficacy and acceptable side-effect profiles.

Review article: Linaclotide for the management of irritable bowel syndrome with constipation

BACKGROUND

Irritable bowel syndrome with constipation (IBS-C) represents a significant burden to patients and healthcare systems due to its prevalence and lack of successful symptomatic resolution with established treatment options. Linaclotide 290 μg has recently been approved by the European Medicines Agency (EMA) for moderate-to-severe IBS-C and by the US Food and Drug Administration for IBS-C (290 μg dose) and for chronic constipation (145 μg dose).

AIM

To summarise data leading to the approval of linaclotide for IBS-C, with focus on EMA-pre-specified outcome measures.

METHODS

Literature search of a peer-review database (PubMed) and review of congress abstracts on linaclotide preclinical and clinical trial data in IBS-C.

RESULTS

Preclinical studies suggest that the guanylate cyclase C agonist (GCCA) linaclotide acts through elevation of cyclic guanosine monophosphate (cGMP) levels, leading to accelerated gastrointestinal (GI) transit through increased fluid secretion and reduced visceral hypersensitivity. Clinical trial data demonstrate that linaclotide improves abdominal symptoms (pain, bloating) and bowel symptoms (constipation) compared with placebo in patients with IBS-C. The most frequent side effect, diarrhoea, results from the therapeutic action of linaclotide. Linaclotide acts locally in the GI tract with minimal systemic exposure, resulting in low oral bioavailability and thus a low risk of relevant systemic adverse effects.

CONCLUSION

Linaclotide, a first-in-class GCCA, is a promising new drug with a novel, dual mechanism of action that, unlike more well-established agents, can relieve the abdominal pain, bloating and constipation associated with IBS-C and has a low propensity for systemic side effects.

Medication management of irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a complex syndrome that is difficult to manage. Here we present the evidence supporting medication treatments for specific IBS symptoms, discuss evidence-based management of IBS with medications including dose regimens and adverse effects and review progress on research for new IBS treatments.

SUMMARY

Currently, there is evidence to support improvements in specific IBS symptoms following treatment with loperamide, psyllium, bran, lubiprostone, linaclotide, amitriptyline, trimipramine, desipramine, citalopram, fluoxetine, paroxetine, dicyclomine, peppermint oil, rifaximin, ketotifen, pregabalin, gabapentin and octreotide and there are many new medications being investigated for the treatment of IBS. Key Message: Of the medications with demonstrated improvements for IBS symptoms, rifaximin, lubiprostone, linaclotide, fiber supplementation and peppermint oil have the most reliable evidence supporting their use for the treatment of IBS. Onset of efficacy for the various medications has been noted to be as early as 6 days after initiation; however, the efficacy of most medications was not assessed prospectively at predefined periods. Additional studies of currently available and new medications are ongoing and are needed to better define their place in therapy and expand therapeutic options for the treatment of IBS. The most promising new medications for IBS include a variety of novel pharmacologic approaches, most notably the dual μ-opioid receptor agonist and δ-opioid antagonist, JNJ-27018966.

Linaclotide for constipation-predominant IBS

Irritable bowel syndrome is a chronic relapsing disorder characterised by abdominal pain or discomfort associated with defaecation, abdominal bloating and a change in bowel habit. IBS may be classified by the change in bowel function as 'diarrhoea predominant' (IBS-D), 'constipation predominant' (IBS-C) or mixed, or may be unclassified. Although it is not thought to be associated with the development of serious disease, IBS is a debilitating condition often resulting in reduced quality of life and significant use of healthcare resources. Current drug treatment strategies target the patient's predominant symptoms and typically involve the use of an antispasmodic and either a laxative or antidiarrhoeal agent. Linaclotide (Constella-Almirall) is an oral guanylate cyclase-C receptor agonist licensed for the symptomatic treatment of moderate to severe IBS-C in adults. In this article, we consider the evidence for linaclotide and how its use fits with current management strategies for IBS-C.

Linaclotide: new mechanisms and new promise for treatment in constipation and irritable bowel syndrome

Chronic idiopathic constipation (CIC) and irritable bowel syndrome (IBS) are functional disorders of the lower gastrointestinal tract. Their prevalence in the general population is between 5% and 20%. Both disorders are chronic, with a relapsing and remitting natural history. The medical treatment of both conditions is unsatisfactory at present, and they represent a huge burden to the health service. Linaclotide is a first-in-class minimally adsorbed, 14-amino-acid peptide agonist of guanylate cyclase C. The drug acts on the intestinal enterocyte. As a consequence of this, intestinal fluid secretion is increased and intestinal transit is accelerated. The efficacy of linaclotide has been studied in both CIC and constipation-predominant IBS (IBS-C). Randomized controlled trials consistently demonstrate that the drug is effective in the treatment of CIC and IBS-C, across a wide range of continuous and dichotomous endpoints. The number needed to treat with linaclotide to prevent one patient with CIC or IBS-C failing to respond to therapy is between 5 and 8 in studies that have reported these data. Overall, in the majority of trials, total numbers of adverse events have been no more frequent with linaclotide, but rates of diarrhoea have been consistently higher. While the drug is clearly effective in the treatment of CIC, there are other evidence-based therapies available, and head-to-head efficacy and cost-effectiveness studies are therefore required to further delineate the role of linaclotide in the treatment of the condition. In IBS-C there are no other licensed therapies available, and linaclotide therefore represents a novel treatment with great promise.

[Functional gastrointestinal diseases]

Functional dyspepsia (FD) and irritable bowel syndrome (IBS) are the most important functional gastrointestinal diseases (FGID), and both affect about 5-15 % of the German population. The patients' symptoms are caused by disturbances of gastrointestinal (GI) motility, secretion and sensitivity. Central processing of visceral afferences is disturbed, and the course of the disease and individual symptom perception are influenced by psychosocial factors. Diagnosis of FD and IBS is based on a compatible symptom pattern, absence of alarm symptoms and exclusion of relevant differential diagnoses. The diagnosis of FD requires a normal upper GI endoscopy. Current German guidelines also demand a normal colonoscopy for diagnosis of IBS. Basic therapeutic measures include explanation of the nature of the disease and its harmlessness quo ad vitam . Individual trigger factors should be identified and eliminated if possible. Drug therapy of persisting complaints is guided by the dominant symptom.

Abdominal bloating: pathophysiology and treatment

Abdominal bloating is a very common and troublesome symptom of all ages, but it has not been fully understood to date. Bloating is usually associated with functional gastrointestinal disorders or organic diseases, but it may also appear alone. The pathophysiology of bloating remains ambiguous, although some evidences support the potential mechanisms, including gut hypersensitivity, impaired gas handling, altered gut microbiota, and abnormal abdominal-phrenic reflexes. Owing to the insufficient understanding of these mechanisms, the available therapeutic options are limited. However, medical treatment with some prokinetics, rifaximin, lubiprostone and linaclotide could be considered in the treatment of bloating. In addition, dietary intervention is important in relieving symptom in patients with bloating.

Translating colorectal cancer prevention through the guanylyl cyclase C signaling axis

Colorectal cancer (CRC) is a major public health concern, ranking among the leading causes of cancer death in both men and women. Because of this continued burden there is a clear need for improved treatment, and more importantly prevention of this disease. In recent years there is significant evidence to support the hypothesis that guanylyl cyclase C (GCY2C) is a tumor suppressor in the intestine, and that the loss of hormone ligands for this receptor is an important step in the disease process. Thus, ligand replacement therapy has been proposed as a strategy to prevent CRC. Until recently this strategy was not clinically plausible; however, the recent regulatory approval of linaclotide (LINZESS™, Forest Laboratories and Ironwood Pharmaceuticals, Inc.), an oral GUCY2C ligand, has raised the possibility of utilizing this strategy clinically to prevent CRC.

Constella™(EU)-Linzess™(USA): the last milestone in the long journey of the peptide linaclotide and its implications for the future of peptide drugs

Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are highly prevalent gastrointestinal disorders associated with health, economical and social problems. Recently, after a long journey of preclinical studies and clinical trials, linaclotide, a first-in-class GC-C receptor peptide agonist, has received the approval in the USA and Europe for the treatment of IBS-C and CIC. This article provides an overview of clinical, economic and biological aspects of IBS-C and CIC and covers the current and emerging therapeutic agents for treating these conditions. Particularly, the pharmacodynamic and pharmacokinetic properties of linaclotide, a small, disulfide-rich peptide, and its implications in the future of peptide drug discovery and development are discussed.

Emerging treatments for chronic constipation

INTRODUCTION

Chronic constipation (CC) is a common problem worldwide and, for some sufferers, a cause of considerable morbidity. Recent definitions of CC have moved from the former emphasis on stool frequency alone to a broader concept that strives to encompass the various symptoms that may bother afflicted individuals. Accordingly, new therapies attempt to not only increase frequency of defecation but also to address such symptoms as satisfaction with bowel action, straining, bloating, and distension.

AREAS COVERED

To provide context the relative merits and problems related to conventional laxative-based approaches to constipation are first reviewed and then more recent novel pharmacological approaches to the management of constipation assessed. The focus is on two classes of compounds, selective prokinetics and prosecretory agents, and studies on their efficacy and safety in chronic idiopathic constipation were retrieved and evaluated.

EXPERT OPINION

While undoubtedly effective, high-quality evidence to support laxatives, the traditional remedies for constipation, is remarkably scarce due, in large part, to the absence, until very recently, of high-quality randomized controlled clinical trials. The selective prokinetic agent prucalopride and the prosecretory agents lubiprostone and linaclotide have shown efficacy and been associated with a good safety record in large well-conducted clinical studies. Other novel approaches, such as the inhibition of ileal bile salt absorption, offer particular promise.

Linaclotide: a new option for the treatment of irritable bowel syndrome with constipation and chronic idiopathic constipation in adults

Chronic idiopathic constipation (CC) and irritable bowel syndrome with predominant constipation (IBS-C) are the 2 most common conditions among functional gastrointestinal disorders. Despite current multiple therapeutic options, treatment remains challenging and dissatisfactory to many patients. Linaclotide is a novel therapeutic agent, which is a guanylate cyclase receptor agonist that stimulates water secretion from the intestinal epithelium by promoting chloride and bicarbonate efflux into the lumen through activation of the cystic fibrosis transmembrane conductance regulator. Clinical trials have demonstrated that linaclotide is effective, safe and well tolerated in patients with CC and IBS-C. This review article highlights the mechanism of action of linaclotide, reviews published literature based on a search of databases, including MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL), up to February 2013, and compares its utility with other currently available agents.

Emerging receptor target in the pharmacotherapy of irritable bowel syndrome with constipation

Preclinical experiments in rodent models have recently provided new information on the mechanisms underlying pain sensation in chronic visceral hypersensitivity, as well as insights into the mechanism of action of new drugs targeting abdominal pain in irritable bowel syndrome (IBS). This article describes the evidence base supporting the role of guanylate cyclase C (GC-C) activation in the modulation of gastrointestinal transit and, in particular, in visceral hypersensitivity. We propose that GC-C activation represents an important emerging target for pharmacotherapy in IBS with constipation (IBS-C), particularly given the recent regulatory approval of the GC-C agonist linaclotide as a treatment for IBS-C. More specifically, we address the following questions: "How is pain transmitted from the colon?"; "How is abdominal pain increased in IBS-C?"; "How can we reduce IBS-related abdominal pain - what drugs have been developed?"; "Does linaclotide reduce abdominal pain in animals and humans?"; and "How does linaclotide reduce abdominal pain?".

How can we achieve relief of bowel and abdominal symptoms for patients with irritable bowel syndrome with constipation?

Current interventions for irritable bowel syndrome with constipation tend to target single symptoms of the disorder, with multiple symptom relief only achieved through the use of combinations of therapies. Hence, there remains an unmet need for well-tolerated and effective treatments for irritable bowel syndrome with constipation that target abdominal symptoms, including abdominal pain and bowel symptoms.

Management of irritable bowel syndrome with constipation: a flexible approach to treating a complex condition with multiple symptoms

Irritable bowel syndrome is a heterogeneous disease with a complex underlying pathophysiology and multiple symptoms - that is, clinical manifestation patterns. As such, management of irritable bowel syndrome requires a flexible approach tailored to the individual patient. This article reviews rational, evidence-based management strategy and treatment options for this variable condition.

FDA and EMA end points: which outcome end points should we use in clinical trials in patients with irritable bowel syndrome?

Trial design and endpoints for the evaluation of drug efficacy in irritable bowel syndrome (IBS) underwent major changes over the last two decades. A systematic review in the early 1990s concluded that there were few well-designed and well-executed treatment trials in IBS. Over the next decade, the so-called binary endpoints were used in several clinical trials in IBS in the US, Europe and other parts of the world. In 2006, the Food and Drug Administration (FDA) published a general guidance for the evaluation of symptom benefit in clinical trials based on patient-reported outcome (PRO) measures, which had a major impact on trial design in IBS. In May 2012, the FDA recommended to use as provisional endpoint the quantification of two major IBS aspects, abdominal pain and disordered defecation, to assess the efficacy of pharmacological treatments in IBS. In the present issue of Neurogastroenterology & Motility, the performance of the FDA Responder Endpoint for clinical trials in irritable bowel syndrome with constipation was evaluated using data from two large Phase III clinical trials of linaclotide. The FDA interim endpoints are clinically relevant as they are also able to capture the smallest patient-reported difference in the domain of Abdominal Pain intensity and Abnormal Defecation with good diagnostic accuracy. The FDA responder definition and the European Medicines Agency responder definitions generate similar response rates, while binary endpoints generate higher responder rates. The implications for optimalization and harmonisation are discussed.

Cyclic nucleotide signaling in intestinal epithelia: getting to the gut of the matter

The intestine is the primary site of nutrient absorption, fluid-ion secretion, and home to trillions of symbiotic microbiota. The high turnover of the intestinal epithelia also renders it susceptible to neoplastic growth. These diverse processes are carefully regulated by an intricate signaling network. Among the myriad molecules involved in intestinal epithelial cell homeostasis are the second messengers, cyclic AMP (cAMP) and cyclic GMP (cGMP). These cyclic nucleotides are synthesized by nucleotidyl cyclases whose activities are regulated by extrinsic and intrinsic cues. Downstream effectors of cAMP and cGMP include protein kinases, cyclic nucleotide gated ion channels, and transcription factors, which modulate key processes such as ion-balance, immune response, and cell proliferation. The web of interaction involving the major signaling pathways of cAMP and cGMP in the intestinal epithelial cell, and possible cross-talk among the pathways, are highlighted in this review. Deregulation of these pathways occurs during infection by pathogens, intestinal inflammation, and cancer. Thus, an appreciation of the importance of cyclic nucleotide signaling in the intestine furthers our understanding of bowel disease, thereby aiding in the development of therapeutic approaches.

Drug development for the irritable bowel syndrome: current challenges and future perspectives

Medications are frequently used for the treatment of patients with the irritable bowel syndrome (IBS), although their actual benefit is often debated. In fact, the recent progress in our understanding of the pathophysiology of IBS, accompanied by a large number of preclinical and clinical studies of new drugs, has not been matched by a significant improvement of the armamentarium of medications available to treat IBS. The aim of this review is to outline the current challenges in drug development for IBS, taking advantage of what we have learnt through the Rome process (Rome I, Rome II, and Rome III). The key questions that will be addressed are: (a) do we still believe in the "magic bullet," i.e., a very selective drug displaying a single receptor mechanism capable of controlling IBS symptoms? (b) IBS is a "functional disorder" where complex neuroimmune and brain-gut interactions occur and minimal inflammation is often documented: do we need to target gut motility, visceral sensitivity, or minimal inflammation? (c) are there validated biomarkers (accepted by regulatory agencies) for studies of sensation and motility with experimental medications in humans? (d) do animal models have predictive and translational value? (e) in the era of personalized medicine, does pharmacogenomics applied to these medications already play a role? Finally, this review will briefly outline medications currently used or in development for IBS. It is anticipated that a more focused interaction between basic science investigators, pharmacologists, and clinicians will lead to better treatment of IBS.