Linaclotide in irritable bowel syndrome with constipation: A Phase 3 randomized trial in China and other regions

Nocebo effects and influencing factors in the randomized clinical trials of chronic constipation: A systematic review and meta-analysis

BACKGROUND

Nocebo effects are unavoidable in randomized clinical trials. We aimed to assess the magnitude of nocebo effects and explore the influencing factors in chronic constipation.

METHODS

We searched the PubMed, Embase, and Cochrane Library databases up to July 2022. Randomized, placebo-controlled trials investigating interventions in chronic constipation were included. We conducted a random effects meta-analysis of the proportion of adverse events (AEs) in placebo-treated participants and evaluated the effect of trial characteristics on nocebo effects.

KEY RESULTS

We identified 20,204 studies from the databases, of which 61 were included in the final analysis. The pooled placebo AE rate was 30.41%, and AE-related withdrawal rate was 1.53%. The most commonly reported AEs were headache (5.67%), diarrhea (4.45%), abdominal pain (3.98%), nasopharyngitis (3.39%), nausea (3.36%), and flatulence (2.95%). The placebo AE rate was lower in trials conducted in Asia compared to those in Europe, North America, and international trials. It was also lower in trials diagnosed by Rome III compared to clinician's opinion and Rome II. Additionally, the placebo AE rate was lower in single-center trials compared to multicenter trials, lower in 5-8 weeks therapy compared to 9-12 weeks therapy, lower in participants with FC compared to those with IBS-C and CC, lower in trials with 2 arms compared to 3 arms, and higher in trials with prokinetic drugs compared to secretagogues and laxatives.

CONCLUSIONS & INFERENCES

The placebo AE rate was 30.41% in patients with chronic constipation. Based on our findings, we recommend that researchers take the nocebo effects into consideration when designing and conducting clinical trials and adopt specific measures to mitigate the negative influence of nocebo effects.

The gut microbiota participates in the effect of linaclotide in patients with irritable bowel syndrome with constipation (IBS-C): a multicenter, prospective, pre-post study

BACKGROUND

Interindividual variation characterizes the relief experienced by constipation-predominant irritable bowel syndrome (IBS-C) patients following linaclotide treatment. Complex bidirectional interactions occur between the gut microbiota and various clinical drugs. To date, no established evidence has elucidated the interactions between the gut microbiota and linaclotide. We aimed to explore the impact of linaclotide on the gut microbiota and identify critical bacterial genera that might participate in linaclotide efficacy.

METHODS

IBS-C patients were administered a daily linaclotide dose of 290 µg over six weeks, and their symptoms were then recorded during a four-week posttreatment observational period. Pre- and posttreatment fecal samples were collected for 16S rRNA sequencing to assess alterations in the gut microbiota composition. Additionally, targeted metabolomics analysis was performed for the measurement of short-chain fatty acid (SCFA) concentrations.

RESULTS

Approximately 43.3% of patients met the FDA responder endpoint after taking linaclotide for 6 weeks, and 85% of patients reported some relief from abdominal pain and constipation. Linaclotide considerably modified the gut microbiome and SCFA metabolism. Notably, the higher efficacy of linaclotide was associated with enrichment of the Blautia genus, and the abundance of Blautia after linaclotide treatment was higher than that in healthy volunteers. Intriguingly, a positive correlation was found for the Blautia abundance and SCFA concentrations with improvements in clinical symptoms among IBS-C patients.

CONCLUSION

The gut microbiota, especially the genus Blautia, may serve as a significant predictive microbe for symptom relief in IBS-C patients receiving linaclotide treatment.

TRIAL REGISTRATION

This trial was registered with the Chinese Clinical Trial Registry (Chictr.org.cn, ChiCTR1900027934).

Nocebo response intensity and influencing factors in the randomized clinical trials of irritable bowel syndrome: A systematic review and meta-analysis

Objective

To estimate the magnitude of the nocebo response and explore its influencing factors in irritable bowel syndrome (IBS).

Methods

The PubMed, Embase, and Cochrane Library databases were searched up to March 2021. We performed a random effects meta-analysis of the proportion of adverse events (AEs) in placebo-treated patients with IBS who are involved in parallel-designed, randomized, placebo-controlled trials investigating pharmacological interventions and evaluated the effect of trial characteristics on the magnitude of the nocebo response rate.

Results

A total of 6,107 studies were identified from the databases. After evaluation, 53 met the eligibility criteria and were included. The overall pooled nocebo response rate was 32% (95% CI: 26-38%). The most commonly reported AEs were headache (9%), nasopharyngitis (7%), abdominal pain (4%), and nausea (4%). The nocebo response rate was low compared with that in the treatment group applying probiotics, antispasmodics, and Traditional Chinese medicine, but high compared with that in antibiotic treatment group. The nocebo rate in patients using diaries to record AEs was lower than the average, and was higher in patients recording through checkup.

Discussion

Patients with IBS have significant nocebo response intensity in clinical trials. Based on findings in this study, we recommend the researchers pay attention to the common AEs and carefully analyze the relation to the intervention.

Comparing probiotic and drug interventions in irritable bowel syndrome: a meta-analysis of randomised controlled trials

Clinical decisions made by health professionals to recommend either drug or probiotic interventions for irritable bowel syndrome (IBS) should be supported by proper knowledge of the efficacy rates of both types of interventions. In this article, we performed a systematic review and meta-analysis to examine the efficacy of both probiotic- and drug interventions in IBS. Medline was searched between January 2015 - January 2021. Randomised controlled trials (RCT) recruiting participants > 18 years old with IBS and examining the effect of probiotics or drugs were eligible for inclusion. The data of the primary outcome, i.e. the persistence of IBS symptoms (dichotomous symptom data), were pooled to obtain a relative risk (RR), with a 95% confidence interval (CI). Secondary outcomes, abdominal pain- and bloating scores (continuous data), were pooled using a standardised mean difference with a 95% CI. The search identified 269 citations of which 32 RCTs were eligible. Our meta-analysis indicated that both probiotic and drug interventions are able to improve the persistence of IBS symptoms (RR 0.60 [0.51; 0.92] versus 0.87 [0.81; 0.92], respectively) and abdominal pain scores (standardised mean difference (SMD) -0.35 [-0.56; -0.14] versus -0.10 [-0.20; 0.00], respectively). However, determining the overall efficacy of both intervention types is inherently complex and such results should be interpreted with care, due to the large diversity of probiotic- and drug types and doses, which is also complicated by variety in IBS subtypes. Hence, as a first step, more large scale randomised double blind placebo-controlled trials focussing on a specific IBS subtype targeted with specific probiotic strains or specific pharmaceutical modalities should be executed, enabling a more proper comparison between trials.

Inadequate safety reporting in the publications of randomised clinical trials in irritable bowel syndrome: drug versus probiotic interventions

Randomised controlled clinical trials (RCTs) offer a unique opportunity to obtain controlled efficacy and safety data to support clinical decisions. However, most RCT reporting has a stronger focus on efficacy rather than safety. This study aimed to identify the safety profile of both probiotic and drug interventions in irritable bowel syndrome (IBS). In connection to this paper, an accompanying paper was published in which a meta-analysis was conducted to evaluate the efficacy of probiotic interventions compared to that of drug interventions in IBS. Together, these two studies provide a first assessment regarding the feasibility to determine a burden to benefit ratio for both probiotic and drug interventions in IBS. RCTs including participants (>18 years old) with IBS and comparing probiotic or drugs interventions with control groups were identified by a systematic search of MEDLINE (January 2015 - Jan 2021). Reported safety profiles in drug studies were completer and more detailed as compared with studies on probiotics. Several inconsistencies in safety reporting were identified between and within drug and probiotic studies, such as: didn't report on safety; only reported adverse reactions (ARs) or adverse events (AEs) with a certain severity; didn't report the total number of AEs; didn't split in the control- or experimental arm; didn't specify AEs; and used different thresholds for 'common' AEs. Hence, it is difficult to compare safety data from drug and probiotic RCTs across and between different studies. On the current approaches to safety reporting, we could not establish an unambiguous safety profile for neither probiotic and drug interventions in IBS. These shortcomings hamper a critical comparison of the burden to benefit ratio for IBS intervention.

AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Constipation

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction associated with significant disease burden. This American Gastroenterological Association guideline is intended to support practitioners in decisions about the use of medications for the pharmacological management of IBS-C and is an update of a prior technical review and guideline.

METHODS

The Grading of Recommendations Assessment, Development and Evaluation framework was used to assess evidence and make recommendations. The technical review panel prioritized clinical questions and outcomes according to their importance for clinicians and patients and conducted an evidence review of the following agents: tenapanor, plecanatide, linaclotide, tegaserod, lubiprostone, polyethylene glycol laxatives, tricyclic antidepressants, selective serotonin reuptake inhibitors, and antispasmodics. The Guideline Panel reviewed the evidence and used the Evidence-to-Decision Framework to develop recommendations.

CONCLUSIONS

The panel agreed on 9 recommendations for the management of patients with IBS-C. The panel made a strong recommendation for linaclotide (high certainty) and conditional recommendations for tenapanor, plecanatide, tegaserod, and lubiprostone (moderate certainty), polyethylene glycol laxatives, tricyclic antidepressants, and antispasmodics (low certainty). The panel made a conditional recommendation against the use of selective serotonin reuptake inhibitors (low certainty).

Adverse events in trials of licensed drugs for irritable bowel syndrome with constipation or diarrhea: Systematic review and meta-analysis

BACKGROUND

Nocebo effects occurring in patients receiving placebo frequently impact on adverse events reported in randomized controlled trials (RCTs) in irritable bowel syndrome (IBS). Therefore, we conducted a systematic review and meta-analysis to assess the proportion of patients randomized to placebo or active drug experiencing any adverse event in trials of licensed drugs for IBS with constipation (IBS-C) or diarrhea (IBS-D), and to estimate the risk of developing adverse events among patients randomized to placebo.

METHODS

We searched MEDLINE, EMBASE CLASSIC and EMBASE, and the Cochrane central register of controlled trials (through June 2021) to identify RCTs comparing licensed drugs with placebo in adults with IBS-C or IBS-D. We generated Forest plots of pooled adverse event rates in both active drug and placebo arms and pooled risk differences (RDs) with 95% confidence intervals (CIs).

KEY RESULTS

There were 21 RCTs of licensed drugs versus placebo in IBS-C (5953 patients placebo) and 17 in IBS-D (3854 patients placebo). Overall, 34.9% and 46.9% of placebo patients in IBS-C and IBS-D trials, respectively, developed at least one adverse event, with a statistically significantly higher risk of any adverse event and withdrawal due to an adverse event with active drug. In IBS-C and IBS-D trials, rates of each individual adverse event were generally higher with active drug. However, in IBS-C trials, only diarrhea or headache was significantly more common with active drug (RD 0.066 (95% CI 0.043-0.088) and RD 0.011 (95% CI 0.002-0.021), respectively), and in IBS-D trials only constipation, nausea, or abdominal pain (RD 0.096 (95% CI 0.054-0.138), 0.014 (95% CI 0.002-0.027), and 0.018 (95% CI 0.002-0.034), respectively).

CONCLUSIONS & INFERENCES

Patients with IBS randomized to placebo have a high risk of reporting adverse events, which might relate to both nocebo and non-nocebo factors. Although patients' expectations and psychosocial factors may be involved, further understanding of the mechanisms are important to control or optimize these effects in RCTs, as well as in clinical practice.

Cost-Effectiveness of Linaclotide Compared to Osmotic Laxatives in the Treatment of Irritable Bowel Syndrome with Constipation in China

INTRODUCTION

Linaclotide, a selective agonist of guanylate cyclase C, was highly recommended for the treatment of irritable bowel syndrome with constipation (IBS-C). However, the cost-effectiveness of linaclotide in Chinese is not known, and this study aimed to assess the cost-effectiveness of linaclotide for patients with IBS-C.

METHODS

An economic evaluation was conducted with a Markov model from a societal perspective. The Markov model was structured to simulate the discontinuation and continuation of medication in IBS-C patients in clinical practice, as well as the revisit and non-visit of non-responding patients. The cycle of the model was 4 weeks, and the time horizon was 1 year. The efficacy data in the model was from the risk ratios obtained by the meta-analysis and the calculation of the response rate of the three medications. The utility, discontinuation rate of the medication, and revisit rate data were from published literature, while the cost data were obtained from experts' opinions and published literature. A series of sensitivity analyses was performed on parameters potentially having impact on the model outputs.

RESULTS

The QALYs (quality-adjusted life years) gained for 1-year treatment with linaclotide, polyethylene glycol, and lactulose were 0.821, 0.795, and 0.781, respectively. The corresponding total costs were CNY 7,721 (USD 1,120), CNY 8,797 (USD 1,276) and CNY 9,481 (USD 1,375). In both comparisons, linaclotide was dominant. Compared with polyethylene glycol and lactulose, the likelihood of linaclotide being cost-effective was 100% for both, using 1 times per capita GDP per QALY as willingness-to-pay threshold.

CONCLUSIONS

IBS-C seriously affects the quality of life of patients with IBS-C, and linaclotide can improve symptoms and quality of life at less cost.

Effects of linaclotide in the treatment of chronic constipation and irritable bowel syndrome with constipation: a meta-analysis

OBJECTIVE

Linaclotide is a guanylate cyclase-C (GCC) agonist that is found in intestinal epithelial cells and is used when treating chronic constipation (CC) and irritable bowel syndrome with constipation (IBS-C). Several randomized controlled trials (RCTs) were conducted for evaluating its efficacy and safety.

METHODS

The PubMed, EMBASE, and Cochrane databases and the Web of Science were searched to find multiple RCTs of patients with CC or IBS-C. The Jadad scoring system was used for evaluating each study's methodological quality, and RevMan5.3 was used for meta-analysis. The composite endpoint reaction approved by the FDA, abdominal pain and discomfort relief, symptom improvement, and diarrhea-related adverse reactions were chosen as observation indicators, and relative risk (RR) and 95% confidence interval (CI) were obtained for quantitative and comprehensive evaluation.

RESULTS

Eleven randomized controlled studies were included, consisting of 5 cases of CC and 6 cases of IBS-C. Linaclotide reached the composite endpoint response approved by FDA in the treatment of CC (RR = 3.26, 95% CI: 2.45-4.33), and the composite endpoint response approved by FDA for the treatment of IBS-C (RR = 2.26, 95% CI: 1.86-2.74) was greater than the placebo (both p < 0.00001). The main adverse reactions of linaclotide were gastrointestinal, mostly diarrhea, which was higher than that of the placebo when treating CC (RR = 3.56, 95% CI: 2.76-4.60) and IBS-C (RR = 8.23, 95% CI: 5.69-11.90) (both p < 0.00001).

CONCLUSION

Linaclotide proved to be effective and safe for the treatment of CC and IBS-C compared to the placebo. However, diarrhea is the primary adverse reaction.

Placebo Response Rates in Trials of Licensed Drugs for Irritable Bowel Syndrome With Constipation or Diarrhea: Meta-analysis

BACKGROUND & AIMS

There are several licensed drugs for irritable bowel syndrome (IBS) that have proven efficacy in randomized controlled trials (RCTs), but placebo response rates are high. We conducted a systematic review and meta-analysis of licensed drugs to estimate magnitude of placebo response rate according to Food and Drug Administration (FDA)-recommended endpoints and to assess how this varies with stringency of the endpoint used to define response.

METHODS

We searched MEDLINE, EMBASE CLASSIC and EMBASE, and the Cochrane central register of controlled trials (through January 2021) to identify RCTs comparing licensed drugs with placebo in adult IBS patients. Studies assessed efficacy according to at least one of composite response, abdominal pain response, or stool response. Data were extracted as intention-to-treat analyses, with dropouts assumed to be treatment failures and pooled using a random-effects model.

RESULTS

There were 17 RCTs of licensed drugs versus placebo in IBS with constipation (4603 patients placebo) and 17 trials in IBS with diarrhea (3908 patients placebo). In IBS with constipation, according to FDA criteria, pooled composite, abdominal pain, and stool response rates with placebo over ≥6 of 12 weeks were 18.9%, 34.6%, and 30.1%, respectively. Evaluating response rates over ≥9 of 12 weeks led to placebo response rates of 4.3% for the composite endpoint, 24.5% for abdominal pain, and 7.7% for stool. In IBS with diarrhea, pooled placebo response rates according to FDA criteria were 16.2% for the composite endpoint, 40.2% for abdominal pain, and 16.2% for stool. Increasing the threshold used to define abdominal pain response from ≥30% improvement to ≥40% or ≥50% led to lower placebo response rates of 34.5% and 23.4%.

CONCLUSIONS

Future RCTs should adhere to current FDA-recommended endpoints for IBS because these lead to lower placebo response rates. However, consideration should be given to further refining some of these to better differentiate between active drug and placebo.

Linaclotide for treating patients with irritable bowel syndrome with predominant constipation: a multicentre study of real-world data in China

INTRODUCTION

Linaclotide, a guanylate cyclase C agonist that improves the symptoms of irritable bowel syndrome with predominant constipation (IBS-C), has been recently approved for IBS-C treatment. This study aimed to report real-world data on linaclotide treatment in China.

METHODS

This was a prospective multicentre study of the effectiveness of linaclotide treatment in patients with IBS-C from 10 primary medical institutions. Changes in defecation, abdominal symptoms, the IBS symptom severity scale (IBS-SSS), IBS quality of life questionnaire (IBS-QOL), Zung Self-Rating Anxiety Scale and Self-Rating Depression Scale in patients were evaluated to determine the drug's clinical efficacy and safety.

RESULTS

We enrolled 97 patients (mean age: 52.39 ± 13.99 years), 55 of whom were women (56.7%). In terms of efficacy, the number of the patients' defecation per week and Bristol stool form scale scores significantly increased at week 4 and week 12 compared with the values at the baseline. The baseline average IBS-SSS score was 211.01 ± 81.23. Of the patients, 24 had severe IBS-C, and their IBS-SSS scores at week 4 (51.81 ± 54.42) and week 12 (9.3 ± 30.39) significantly decreased and showed a pronounced improvement. The IBS-QOL total scores at week 4 and week 12 gradually decreased compared with that at the baseline and the QOL significantly improved. Treatment satisfaction rate was 79.3% in week 4 and 100% in week 12, showing a gradually increased satisfaction and significant differences. However, 11 cases (11.3%) had diarrhoea.

CONCLUSION

Linaclotide has proved to be a safe and effective drug to improve IBS-C symptoms and severity.

Improvement in constipation and diarrhea is associated with improved abdominal pain in patients with functional bowel disorders

BACKGROUND

Abdominal pain is a bothersome and lifestyle limiting symptom in patients with functional bowel disorders. It is associated with decreased quality of life in affected individuals, as well as significant annual healthcare expenditure. Knowledge of specific factors that predict improvement in abdominal pain in those with functional bowel disorders is thus far limited.

METHODS

Consecutive patients presenting for outpatient care at a major academic medical center between October 2017 and March 2020 completed an electronic symptom survey prior to initial clinic visit, and again after 3 months. The Rome IV questionnaires for functional dyspepsia, irritable bowel syndrome, functional constipation, and functional diarrhea were all included. Additionally, all subjects completed the Patient Reported Outcomes Measurement Information System Anxiety, Depression, and sleep disturbance questionnaires. Patients with a diagnosis of a Rome IV functional gastrointestinal disorder without any organic cause for symptoms were identified based on both chart review as well as survey response data. Univariable and multivariable analysis was used to assess predictors of improved abdominal pain after 3 months.

KEY RESULTS

180 patients with a mean age of 45.3 years were included in the final analysis. 78.3% of patients were female, and 77.2% met Rome IV criteria for irritable bowel syndrome. On multivariable analysis, improvement in constipation and diarrhea were both independent predictors of improved abdominal pain after 3 months.

CONCLUSIONS AND INFERENCES

Improvement in constipation and diarrhea both predicted improvement in abdominal pain, suggesting that addressing these factors is central to the management of abdominal pain in functional gastrointestinal disorders.

Fabry disease - a multisystemic disease with gastrointestinal manifestations

Nonspecific gastrointestinal (GI) symptoms, such as postprandial cramping pain, diarrhea, nausea and vomiting are typical symptoms for irritable bowel syndrome or inflammatory bowel disease, but may also be the first symptoms of Fabry disease (FD). This review focus on GI manifestations in FD, by providing an overview of symptoms, a proper diagnosis, an appropriate management by FD-specific and concomitant medications and lifestyle interventions. We provide comprehensive literature-based data combined with personal experience in the management of FD patients. Since FD is rare and the clinical phenotype is heterogeneous, affected patients are often misdiagnosed. Consequently, physicians should consider FD as a possible differential diagnosis when assessing unspecific GI symptoms. Improved diagnostic tools, such as a modified GI symptom assessment scale can facilitate the diagnosis of FD in patients with GI symptoms of unknown cause and thus enable the timely initiation of a disease-specific therapy. Expansive intravenous enzyme replacement therapy with α-galactosidase A or oral chaperone therapy for patients with amenable mutations improve the disease burden including GI symptoms, but a timely start of therapy is crucial for the prognosis. A special diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) or pro- and prebiotics might improve FD-typical GI symptoms. Furthermore, preliminary success was reported with the oral administration of α-galactosidase A. In addition to a timely initiation of FD-specific therapy, affected patients with GI symptoms might benefit from a FODMAP-low diet, pro- and prebiotics and/or low-cost oral substitution with AGAL to support digestion and reduce dysbiosis.

Efficacy and safety of linaclotide in patients with irritable bowel syndrome with constipation: Chinese sub-cohort analysis of a phase III, randomized, double-blind, placebo-controlled trial

OBJECTIVE

To conduct a sub-cohort analysis to evaluate the efficacy and safety of linaclotide in Chinese patients with constipation-predominant irritable bowel syndrome (IBS-C) using data from a completed trial (NCT01880424).

METHODS

In this phase III, double-blind, placebo-controlled trial, IBS-C patients were randomized to receive linaclotide (290 μg/d) or placebo for 12 weeks. Efficacy was assessed with two co-primary responder end-points (12-wk abdominal pain/discomfort: ≥30% reduction in either score with neither deteriorating from baseline for ≥6 wks; 12-wk IBS degree of relief: score ≤2 for ≥ 6 wks), seven secondary endpoints and several additional end-points.

RESULTS

In total, 659 Chinese IBS-C patients received linaclotide (n = 327) or placebo (n = 332). The 12-week abdominal pain/discomfort end-point was met in 62.1% and 53.3% of the linaclotide-treated and placebo-treated patients, respectively (odds ratio [OR] 1.43, 95% confidence interval [CI] 1.05-1.96, P = 0.023); the 12-week IBS degree of relief end-point was achieved in 32.7% and 16.9% of the patients treated with linaclotide and placebo, respectively (OR 2.40, 95% CI 1.66-3.47, P < 0.001). The linaclotide-treated patients had a shorter time to the first spontaneous bowel movement than the placebo-treated patients (23.6 h vs 43.7 h, P < 0.001). Linaclotide produced significantly greater improvement than placebo in all secondary end-points from the first 2 weeks (all P < 0.001). Diarrhea was reported in 8.3% of linaclotide-treated patients and 1.2% of placebo-treated patients.

CONCLUSION

Linaclotide (290 μg/d) was efficacious and well-tolerated in Chinese IBS-C patients with a rapid onset of effect.

Guanylate cyclase-C agonists as peripherally acting treatments of chronic visceral pain

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder characterized by abdominal pain and altered bowel habit that affects ~11% of the global population. Over the past decade, preclinical and clinical studies have revealed a variety of novel mechanisms relating to the visceral analgesic effects of guanylate cyclase-C (GC-C) agonists. Here we discuss the mechanisms by which GC-C agonists target the GC-C/cyclic guanosine-3',5'-monophosphate (cGMP) pathway, resulting in visceral analgesia as well as clinically relevant relief of abdominal pain and other sensations in IBS patients. Due to the preponderance of evidence we focus on linaclotide, a 14-amino acid GC-C agonist with very low oral bioavailability that acts within the gut. Collectively, the weight of experimental and clinical evidence supports the concept that GC-C agonists act as peripherally acting visceral analgesics.

Cyclic peptide drugs approved in the last two decades (2001-2021)

In contrast to the major families of small molecules and antibodies, cyclic peptides, as a family of synthesizable macromolecules, have distinct biochemical and therapeutic properties for pharmaceutical applications. Cyclic peptide-based drugs have increasingly been developed in the past two decades, confirming the common perception that cyclic peptides have high binding affinities and low metabolic toxicity as antibodies, good stability and ease of manufacture as small molecules. Natural peptides were the major source of cyclic peptide drugs in the last century, and cyclic peptides derived from novel screening and cyclization strategies are the new source. In this review, we will discuss and summarize 18 cyclic peptides approved for clinical use in the past two decades to provide a better understanding of cyclic peptide development and to inspire new perspectives. The purpose of the present review is to promote efforts to resolve the challenges in the development of cyclic peptide drugs that are more effective.

Review article: current and future treatment approaches for IBS with constipation

BACKGROUND

Multiple efficacious therapies are currently available for treating irritable bowel syndrome with constipation (IBS-C). IBS-C specific survey tools that assess symptom relief, treatment satisfaction, and quality of life are important for gauging real-world effectiveness.

AIMS/METHODS

This article reviews clinical trial efficacy data as well as survey data on adequate relief and quality of life from pivotal trials for lubiprostone, linaclotide, plecanatide, tenapanor, and tegaserod. A brief discussion of agents in development with novel mechanisms of action is also provided.

RESULTS/CONCLUSIONS

Quality of life and symptom metrics should be standardized and continue to be represented in future IBS-C trials. The choice of agent should be tailored to probability of improving symptoms, safety, tolerability, and cost.

Diarrhea-Predominant and Constipation-Predominant Irritable Bowel Syndrome: Current Prescription Drug Treatment Options

Irritable bowel syndrome (IBS) is a heterogenous disease with a variety of therapeutic options, including eight prescription drugs approved for use in IBS in the USA. Choosing among the myriad treatment options requires attention to patient preferences both on clinical outcomes and costs associated with treatment. We performed a narrative review of the literature to summarize these important determinants of treatment choice including: labeled indications; clinical profiles of efficacy, safety, and tolerability of prescription drugs; and cost-effectiveness for diarrhea-predominant IBS drugs (IBS-D: alosetron, eluxadoline, and rifaximin) and constipation-predominant IBS drugs (IBS-C: linaclotide, lubiprostone, plecanatide, tegaserod, and tenapanor). We then review the standard model of shared decision-making aimed at guiding an informed, patient-centered discussion to integrate comparative clinical and cost outcomes toward choosing an IBS treatment in practice.

Focus on Pharmacotherapy for Irritable Bowel Syndrome with Constipation

Irritable bowel syndrome with constipation is a common disorder that significantly impairs quality of life. There are now multiple classes of therapeutics that have been shown via rigorous clinical testing to improve the abdominal and bowel symptoms attributed to irritable bowel syndrome with constipation. These include the secretagogues (lubiprostone, linaclotide, plecanatide, tenapenor) and the prokinetic agent tegaserod. This article highlights the pivotal evidence for these agents and most recent treatment guidance from the major North American gastroenterological societies. When pharmaceuticals are used, a patient-specific approach based on efficacy, safety, tolerability, access, and affordability is recommended.

Systematic review and network meta-analysis: efficacy of licensed drugs for abdominal bloating in irritable bowel syndrome with constipation

BACKGROUND

Although bloating is a highly prevalent and troublesome symptom in irritable bowel syndrome with constipation (IBS-C), treatment is empirical with no specific guidelines for its management.

AIM

To conduct a pairwise and network meta-analysis, using a frequentist approach, of Food and Drug Administration-licensed drugs for IBS-C comparing their efficacy for abdominal bloating as a specific endpoint.

METHODS

We searched the medical literature through December 2020 to identify randomised controlled trials (RCTs) in IBS-C, with abdominal bloating reported as a dichotomous assessment. Efficacy of each drug was reported as a pooled relative risk (RR) with 95% confidence intervals (CIs) to summarise effect of each comparison tested. Treatments were ranked according to their P-score.

RESULTS

We identified 13 eligible RCTs, containing 10 091 patients. Linaclotide 290 µg o.d., lubiprostone 8 µg b.d., tenapanor 50 mg b.d. and tegaserod 6 mg b.d. were all superior to placebo for abdominal bloating in patients with IBS-C, in both pairwise and the network meta-analyses. Linaclotide demonstrated the greatest improvement in abdominal bloating in both pairwise and network meta-analysis (RR of failure to achieve an improvement in abdominal bloating = 0.78; 95% CI 0.74-0.83, number needed to treat = 7, P-score 0.97). Indirect comparison revealed no significant differences between individual drugs.

CONCLUSIONS

We found all licensed drugs for IBS-C to be superior to placebo for abdominal bloating. Linaclotide appeared to be the most efficacious at relieving abdominal bloating. Further research is needed to assess long-term efficacy of these agents and to better understand the precise mechanism of improving bloating.

Irritable bowel syndrome in China: a review on the epidemiology, diagnosis, and management

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disease worldwide. Current guidelines of IBS are mostly based on the western populations and expected to vary in different communities. China has a large population and a vast literature is available on IBS. Due to linguistic variations in the literature, the studies are not widely known and their conclusions thus remain largely obscured to the western medical literature. In this article, we reviewed the published literatures on the investigations of IBS epidemiology, diagnosis, and management in the Chinese population and emphasized the different findings gleaned from the western publications. The detailed literature review will benefit understanding of and promote future study on IBS.

Review article: diagnosis, management and patient perspectives of the spectrum of constipation disorders

BACKGROUND

Chronic constipation is a common, heterogeneous disorder with multiple symptoms and pathophysiological mechanisms. Patients are often referred to a gastroenterology provider after laxatives fail. However, there is limited knowledge of the spectrum and management of constipation disorders.

AIM

To discuss the latest understanding of the spectrum of constipation disorders, tools for identifying a pathophysiologic-based diagnosis in the specialist setting, treatment options and the patient's perspective of constipation.

METHODS

Literature searches were conducted using PubMed for constipation diagnostic criteria, diagnostic tools and approved treatments. The authors provided insight from their own practices.

RESULTS

Clinical assessment, stool diaries and Rome IV diagnostic criteria can facilitate diagnosis, evaluate severity and distinguish between IBS with constipation, chronic idiopathic constipation and dyssynergic defecation. Novel smartphone applications can help track constipation symptoms. Rectal examinations, anorectal manometry and balloon expulsion, assessments of neuromuscular function with colonic transit time and colonic manometry can provide mechanistic understanding of underlying pathophysiology. Treatments include lifestyle and diet changes, biofeedback therapy and pharmacological agents. Several classes of laxatives, as well as prokinetic and prosecretory agents, are available; here we describe their mechanisms of action, efficacy and side effects.

CONCLUSIONS

Constipation includes multiple overlapping subtypes identifiable using detailed history, current diagnostic tools and smartphone applications. Recognition of individual subtype(s) could pave the way for optimal, evidence-based treatments by a gastroenterology provider.

The placebo response rate in pharmacological trials in patients with irritable bowel syndrome: a systematic review and meta-analysis

BACKGROUND

Clinical trials in irritable bowel syndrome are associated with high placebo response rates. We aimed to identify the magnitude of the placebo response and the contributing factors to this occurrence.

METHODS

We did a systematic review and meta-analysis with a search of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials between April 1, 1959, and April 30, 2020. We included all randomised controlled trials that compared an active pharmacotherapeutic agent with placebo and had a dichotomous outcome of response to therapy (in terms of global improvement or improvement in abdominal pain) in adults (aged ≥18 years) with irritable bowel syndrome. Exclusion criteria were trials reporting on treatment satisfaction as a dichotomous outcome of response to therapy or clinician-reported outcomes and a treatment duration of less than 4 weeks. Our main outcome was identification of the magnitude of the pooled placebo response rate for the following endpoints: global improvement, abdominal pain, and US Food and Drug Administration (FDA) endpoints. We extracted information from published reports and pooled proportions through meta-analysis with random effects. The study was registered with PROSPERO, CRD42020170908.

FINDINGS

Of the 6863 publications identified, 70 articles describing 73 randomised controlled trials were included in our analysis. The pooled placebo response rate was 27·3% (95% CI 24·3-30·9) using the global improvement endpoint, 34·4% (31·2-37·8) using the abdominal pain endpoint, and 17·9% (15·2-21·0) using the composite FDA endpoint responder definition, all with substantial heterogeneity between the trials. Studies published before 2006, and those done in Europe, with a parallel design, a run-in period of 2 weeks or less, a dose schedule of three times a day or more, or a smaller sample size of the control group were significantly associated with an increased pooled placebo response rate.

INTERPRETATION

More than a quarter of patients with irritable bowel syndrome had a placebo response in terms of global improvement, with multiple associated moderators. We recommend future trials apply a run-in period of at least 2 weeks and dose once or twice a day to minimise the placebo response rate.

FUNDING

None.

Fabry Disease: The Current Treatment Landscape

Fabry disease (FD) is a rare X-linked lysosomal storage disease based on a deficiency of α-galactosidase A (AGAL) caused by mutations in the α-galactosidase A gene (GLA). The lysosomal accumulation of glycosphingolipids, especially globotriaosylceramide (Gb₃) and globotriaosylsphingosine (lyso-Gb₃, deacylated form), leads to a multisystemic disease with progressive renal failure, cardiomyopathy with potentially malignant cardiac arrhythmias, and strokes, which considerably limits the life expectancy of affected patients. Diagnostic confirmation in male patients is based on the detection of AGAL deficiency in blood leukocytes, whereas in women, due to the potentially high residual enzymatic activity, molecular genetic detection of a causal mutation is required. Current treatment options for FD include recombinant enzyme replacement therapy (ERT) with intravenous agalsidase-alfa (0.2 mg/kg body weight) or agalsidase-beta (1 mg/kg body weight) every 2 weeks and oral chaperone therapy with migalastat (123 mg every other day), which selectively and reversibly binds to the active site of AGAL, thereby correcting the misfolding of the enzyme and allowing it to traffic to the lysosome. These therapies enable cellular Gb₃ clearance and improve the burden of disease. However, in about 40% of all ERT-treated men, ERT can lead to infusion-associated reactions and the formation of neutralizing antidrug antibodies, which reduces the efficacy of therapy. In chaperone therapy, there are carriers of amenable mutations that show limited clinical success. This article provides a brief overview of the clinical picture in FD patients, diagnostic confirmation, and interdisciplinary clinical management of FD. The focus is on current and future therapeutic options.

[Efficacy and Safety of Linaclotide in Elderly Patients]

The efficacy and safety of linaclotide in elderly patients are poorly understood. Herein, we aimed to assess the efficacy and safety of linaclotide in elderly patients in real-world setting. We retrospectively enrolled consecutive patients who started linaclotide therapy at Sapporo Medical University Hospital from October 1, 2017 to December 31, 2019. The efficacy and safety of linaclotide were examined in relation to various factors, including age (<65 or ≥65 years) and dose (0.25 or 0.5 mg/d). Fifty-two patients were enrolled, 60% of whom were over 65 years old and 40% were female. Thirty-six patients received a linaclotide dose of 0.25 mg/d. The most common side effect was diarrhea, but there was no difference in the incidence of diarrhea between the elderly (64.5%) and non-elderly patients (42.9%, p=0.130). No significant difference was observed with respect to improvement in constipation in the elderly (83.9%) and non-elderly patients (71.4%, p=0.318). Additionally, the difference in efficacy of linaclotide in patients who received a reduced dose (80.6%) vs. those who received the recommended dose (75.0%) was not statistically significant (p=0.719). Multivariate analysis revealed that age, gender, and dose were not associated with diarrhea induced by linaclotide treatment. However, concurrent treatment with constipation-inducing medications [odds ratio (OR) 5.79, p=0.047] and linaclotide monotherapy (OR 11.1, p=0.040) were both risk factors contributing to diarrhea. Linaclotide is effective and safe for use in elderly patients. The incidence of diarrhea may increase when linaclotide is administered alone or concurrently used with medications that cause constipation.

Multicentre, non-interventional study of the efficacy and tolerability of linaclotide in the treatment of irritable bowel syndrome with constipation in primary, secondary and tertiary centres: the Alpine study

OBJECTIVES

We evaluated the effectiveness and tolerability of linaclotide, a minimally absorbed guanylate cyclase-C agonist, in patients with irritable bowel syndrome with constipation (IBS-C) in routine clinical practice.

SETTING

A multicentre, non-interventional study conducted between December 2013 and November 2015 across 31 primary, secondary and tertiary centres in Austria and Switzerland.

PARTICIPANTS

The study enrolled 138 patients aged ≥18 years with moderate-to-severe IBS-C. Treatment decision was at the physician's discretion. Patients with known hypersensitivity to the study drug or suspected mechanical obstruction were excluded. The mean age of participants was 50 years, and >75% of the patients were women. 128 patients completed the study.

PRIMARY AND SECONDARY OUTCOME MEASURES

Data were collected at weeks 0 and 4 in Austria and weeks 0, 4 and 16 in Switzerland. The primary effectiveness endpoints included severity of abdominal pain and bloating (11-point numerical rating scale [0=no pain/bloating to 10=worst possible pain/bloating]), frequency of bowel movements and physicians' global effectiveness of linaclotide. Treatment-related adverse events (AEs) were recorded.

RESULTS

Following a 4-week treatment period, the mean intensity score of abdominal pain was reduced from 5.8 at baseline to 2.7, while the bloating intensity score was reduced from 5.8 at baseline to 3.1e (both indices p<0.001). The frequency of mean weekly bowel movements increased from 2.1 at baseline to 4.5 at week 4 (p<0.001). Global effectiveness and tolerability of linaclotide were assessed by the treating physicians as 'good' or 'excellent' in >70% of patients. In total, 31 AEs were reported in 22 patients, the most common being diarrhoea, reported by 6 (7%) and 8 (15.4%) patients in Austria and Switzerland, respectively.

CONCLUSIONS

Patients with IBS-C receiving linaclotide experienced effective treatment of moderate-to-severe symptoms in routine clinical practice. Linaclotide was safe and well tolerated and no new safety concerns were raised, supporting results from previous clinical trials.

Second Asian Consensus on Irritable Bowel Syndrome

BACKGROUND/AIMS

There has been major progress in our understanding of the irritable bowel syndrome (IBS), and novel treatment classes have emerged. The Rome IV guidelines were published in 2016 and together with the growing body of Asian data on IBS, we felt it is timely to update the Asian IBS Consensus.

METHODS

Key opinion leaders from Asian countries were organized into 4 teams to review 4 themes: symptoms and epidemiology, pathophysiology, diagnosis and investigations, and lifestyle modifications and treatments. The consensus development process was carried out by using a modified Delphi method.

RESULTS

Thirty-seven statements were developed. Asian data substantiate the current global viewpoint that IBS is a disorder of gut-brain interaction. Socio-cultural and environmental factors in Asia appear to influence the greater overlap between IBS and upper gastrointestinal symptoms. New classes of treatments comprising low fermentable oligo-, di-, monosacharides, and polyols diet, probiotics, non-absorbable antibiotics, and secretagogues have good evidence base for their efficacy.

CONCLUSIONS

Our consensus is that all patients with functional gastrointestinal disorders should be evaluated comprehensively with a view to holistic management. Physicians should be encouraged to take a positive attitude to the treatment outcomes for IBS patients.

Linaclotide increases cecal pH, accelerates colonic transit, and increases colonic motility in irritable bowel syndrome with constipation

BACKGROUND

Linaclotide is efficacious in the management of irritable bowel syndrome with constipation (IBS-C), yet relatively little is known regarding its effect on human gastrointestinal physiology. The primary aim of the study was to examine the effect of linaclotide on change in pH across the ileocecal junction (ICJ), a proposed measure of cecal fermentation, and its relationship to symptoms and quality of life (QoL) in IBS-C.

METHODS

A total of 13 participants with Rome III IBS-C underwent a standardized wireless motility capsule (WMC). Stool consistency was measured using the Bristol stool form scale (BSFS) and frequency with spontaneous bowel movements (SBM). Gastrointestinal symptoms and QoL were assessed using validated questionnaires. The WMC and questionnaires were repeated after 28 days of linaclotide 290 g po od.

KEY RESULTS

Linaclotide reduced the change in pH across the ICJ (-2.4 ± 0.2 vs -2.1 ± 0.4, P = 0.01) as a function of a relative alkalinization of the cecum (5.2 ± 0.2 vs 5.5 ± 0.3, P = 0.02). Linaclotide accelerated colonic transit time (2650 minutes (2171-4038) vs. 1757 (112-3011), P = 0.02), increased colonic log motility index (15 ± 1.8 vs. 16.5 ± 1.8, P = 0.004) but had no effect of gastric emptying or small bowel transit. Change in pH across the ICJ correlated with improvement in symptom intensity, unpleasantness, and visceral sensitivity index (r = 0.62, P = 0.03, r = 0.63, P = 0.02, r = 0.62, P = 0.02) and with increases in BSFS type and SBM (r = 0.9, P < 0.0001, r = 0.6, P = 0.02).

CONCLUSIONS & INFERENCES

Linaclotide's effects are confined to the colon where it increases cecal pH, potentially representing a reduction in cecal fermentation and accelerates colonic motility.

High-dose linaclotide is effective and safe in patients with chronic constipation: A phase III randomized, double-blind, placebo-controlled study with a long-term open-label extension study in Japan

BACKGROUND

A previous phase II dose-ranging study of linaclotide in a Japanese chronic constipation (CC) population showed that 0.5 mg was the most effective dose. This study aimed to verify the hypothesis that 0.5 mg of linaclotide is effective and safe in Japanese CC patients.

METHODS

This was a Japanese phase III randomized, double-blind, placebo-controlled (part 1), and long-term, open-label extension (part 2) study of linaclotide. CC patients (n = 186) diagnosed using the Rome III criteria were randomly assigned to linaclotide 0.5 mg (n = 95) or placebo (n = 91) for a 4-week double-blind treatment period in part 1, followed by an additional 52 weeks of open-label treatment with linaclotide in part 2. The primary efficacy endpoint was the change from baseline in weekly spontaneous bowel movement (SBM) frequency at the first week. Secondary endpoints included responder rate for complete SBM (CSBM), changes in stool consistency, and severity of straining.

KEY RESULTS

Part 1: Change in weekly mean SBM frequency in the first week of treatment with linaclotide (4.02) was significantly greater than that with placebo (1.48, P < 0.001). Linaclotide produced a higher CSBM responder rate (52.7%) compared to placebo (26.1%, P < 0.001). Part 2: Patients continued to show improved SBM frequency with linaclotide. Through parts 1 and 2, the most common drug-related adverse event was mild and occasionally moderate diarrhea.

CONCLUSIONS AND INFERENCES

The results of this study indicate that a linaclotide dose of 0.5 mg/day is effective and safe in Japanese CC patients.

Efficacy of Secretagogues in Patients With Irritable Bowel Syndrome With Constipation: Systematic Review and Network Meta-analysis

BACKGROUND & AIMS

Several secretagogues have been approved for the treatment of irritable bowel syndrome with constipation (IBS-C). However, their relative efficacy is unclear because there have been no head-to-head randomized controlled trials. We conducted a network meta-analysis to compare their efficacies in patients with IBS-C.

METHODS

We searched MEDLINE, EMBASE, EMBASE Classic, and the Cochrane Central Register of Controlled Trials through June 2018 to identify randomized controlled trials assessing the efficacy of secretagogues in adults with IBS-C. Trials included in the analysis reported a dichotomous assessment of overall response to therapy, and data were pooled using a random-effects model. Efficacy and safety of secretagogues were reported as a pooled relative risk with 95% confidence interval to summarize the effect of each comparison tested, and treatments were ranked according to their P score.

RESULTS

We identified 15 eligible randomized controlled trials of secretagogues that included 8462 patients. Linaclotide, lubiprostone, plecanatide, and tenapanor were superior to placebo for the treatment of IBS-C. Linaclotide (290 μg once daily) was ranked first in efficacy based on the end point recommended by the Food and Drug Administration for trials in IBS-C, the primary end point used in each trial, abdominal pain, and complete spontaneous bowel movements. Tenapanor (50 mg twice daily) was ranked first for decreasing bloating. Total numbers of adverse events were significantly larger with linaclotide (290 and 500 μg once daily) and plecanatide (3 mg once daily) compared with placebo. However, plecanatide 6 mg once daily ranked first for safety. Diarrhea was significantly more common with all drugs, except lubiprostone (8 μg twice daily). Nausea was significantly more common in patients who received lubiprostone.

CONCLUSIONS

In a network analysis of randomized controlled trials of secretagogues for IBS-C, we found all drugs to be superior to placebo. Efficacy was similar among individual drugs and dosages for most end points. However, data were extracted at the 12-week time point, so the long-term relative efficacy of these drugs is unknown.

The gastrointestinal symptoms present in patients with postural tachycardia syndrome: A review of the literature and overview of treatment

Orthostatic intolerance, including postural tachycardia syndrome, is often associated with gastrointestinal symptoms. In the vast majority of the cases, the gastrointestinal symptoms are not secondary to the orthostatic disorder, but rather just a comorbid condition. This concept is critical, since treatment aimed at the orthostatic condition will not improve the gastrointestinal symptoms. Only when the gastrointestinal symptoms develop in the upright position and improve or resolve in the supine position, they may be related to the orthostatic stress. The most common symptoms associated with orthostatic intolerance include nausea, dyspepsia, bloating and constipation. The majority of subjects do not have gastroparesis. The chapter discusses available treatments of these conditions.