Guanylate cyclase-C Receptor Research Articles

Linaclotide (Linzess) for functional constipation.

The guanylate cyclase-C receptor agonist linaclotide (Linzess – Abbvie/Ironwood) was first approved by the FDA in 2012 for treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation in adults.

#3650 LINACLOTIDE IS PROTECTIVE AGAINST RENAL ISCHEMIA-REPERFUSION INJURY

Abstract Background and Aims Renal ischemia-reperfusion injury is associated with delayed graft function and poor long-term graft survival following transplantation. Linaclotide is a guanylate cyclase C (GC-C) receptor agonist that increases intracellular cGMP concentrations and promotes intestinal transport capacity by activating the GC-C receptor. Since CKD is a deficiency of cGMP in the kidney, increasing cGMP in the kidney by linaclotide would suppress fibrosis, protecting the kidney. Method An AKI rat model of unilateral nephrectomy plus contralateral ischaemia (30 min) and impaired reperfusion (up to 14 days) was used. Linaclotide was administered before and after surgery for 2 weeks, and blood and renal tissue samples were collected to determine its effect on renal function and whether it was protective against the progression of CKD. Results In the I/R injury+ group, creatinine levels were lower in the linaclotide-treated group than in the non-treated group. Sirius red staining showed significant improvement in fibrosis. The hydroxyproline content of kidneys was determined by the basic hydroxyproline method. RNA seq showed that genes down-regulated in I/R injury+ were the oxidative stress markers SOD3 and Gpx1. The expression of genes down-regulated in I/R injury+ was up-regulated to a degree similar to that in I/R injury- by treatment with linaclotide. These data suggest that linaclotide may ameliorate renal fibrosis by suppressing renal dysfunction through its antioxidant effects. Conclusion The antioxidant effect of linaclotide was found to suppress the decrease in renal function caused by I/R. We would like to apply this finding to human renal transplantation in the future to prevent renal function deterioration due to I/R.

The Effect of Acid Suppression Therapy on the Safety and Efficacy of Plecanatide: Analysis of Randomized Phase III Trials

PurposePlecanatide, an approved therapy for chronic idiopathic constipation (CIC) and irritable bowel syndrome with constipation, is an analogue of uroguanylin that replicates its pH-sensitive activity and binds to guanylate cyclase-C receptors expressed on intestinal epithelium, stimulating fluid secretion. This analysis explores concomitant acid suppression therapy's effect on the efficacy and safety of plecanatide in adults with CIC. MethodsData from 2 placebo-controlled, 12-week Phase III trials of plecanatide in CIC were pooled. Patients were randomized to receive placebo, plecanatide 3 mg, or plecanatide 6 mg. The primary endpoint was the durable, overall complete spontaneous bowel movement (CSBM) response rate (defined as ≥3 CSBMs in a given week and ≥1 CSBM increase from baseline within a week for ≥9 of 12 weeks, including ≥3 of the last 4 treatment weeks). Safety was also evaluated. Results were stratified by concomitant use or nonuse of acid suppression therapy. FindingsOf the pooled intent-to-treat population, 338 of 2639 patients (12.8%) received concomitant acid suppression medication. Efficacy response rates in patients using acid suppressors were 23.6% with plecanatide 3 mg (P = 0.001 vs placebo), 22.1% with plecanatide 6 mg (P = 0.002), and 7.6% with placebo. Responses were similar in patients not using acid suppressors: 20.4% (plecanatide 3 mg, P < 0.001), 19.6% (plecanatide 6 mg, P < 0.001), and 12.1% (placebo). Serious adverse events were experienced by 3.3% of patients who used concomitant acid suppression and 1.0% of those who did not. ImplicationsPlecanatide treatment is safe and efficacious for patients with CIC when administered with concomitant acid suppression medication. ClinicalTrials.gov identifiers: NCT02122471 and NCT01982240.

Intestinal Guanylate Cyclase-C mRNA Expression in Duodenum and Colon of Children.

Guanylate cyclase-C (GC-C) agonists, which increase intestinal secretion and accelerate transit, are used to treat chronic constipation and constipation-predominant irritable bowel syndrome and are being evaluated for pediatric use. Prior studies suggest GC-C receptor density may be higher in young children, potentially amplifying GC-C agonism with treatment implications. We aimed to quantitate duodenal and colonic GC-C mRNA expression in children. Mucosal biopsies were obtained from subjects aged 6 months to 18 years during clinically indicated upper, that is, esophago-gastro-duodenal, and/or colonic endoscopy. Tissue samples without histologic abnormalities were grouped by subject age (<24 months, 24 months to <6 years, 6 to <12 years, and 12 to <18 years) and analyzed for GC-C mRNA expression by qPCR. The relationship between GC-C mRNA levels and age was modeled using regression analyses. Ninety-nine subjects underwent upper endoscopy/colonoscopy; 93 had evaluable samples. Mean relative GC-C mRNA expression was 2.36 (range 2.21-2.46) for duodenal samples and 1.56 (range 1.22-1.91) for colonic samples. Predicted and observed normalized GC-C mRNA expression in each region were comparable among age groups. Pooled expression by region demonstrated lower expression in colonic versus duodenal samples. Uniform levels of GC-C mRNA expression were detected in children aged >6 months in the duodenum and >12 months in the colon. Higher expression was observed in all age groups in duodenal versus colonic samples, indicating regional variability in GC-C receptor density. These data are reassuring for further studies of GC-C agonists in children.

ID: 3519286 COMPARISON OF 1-L PEG PLUS ASCORBIC ACID WITH LINACLOTIDE VERSUS SENNOSIDE FOR COLON CLEANING IN CONSTIPATED PATIENTS

Background and Aim: The 2-L polyethylene glycol plus ascorbic acid (PEG-Asc) is an effective alternative to standard 4-L PEG for bowel preparation before colonoscopy. Several studies have reported the adjunctive laxative agents can effectively reduce the volume of PEG-Asc solution required and increase patient tolerability. We recently reported the efficacy of 1-L PEG-Asc plus sennoside for bowel preparation, but this regimen was insufficient for patients with chronic constipation (2020 GIE vol 91 S6). Linaclotide is a guanylate cyclase-C receptor agonist currently approved and available for the treatment of adults with chronic constipation in many countries. We hypothesized that addition of linaclotide to 1-L PEG-Asc would yield to better results than that of sennoside regimen in patients with chronic constipation.

S0506 Efficacy and Safety of Plecanatide in Patients With Chronic Idiopathic Constipation: Pooled Analysis of Two Phase 3 Trials Stratified by Concomitant Acid Suppression Use

INTRODUCTION: Plecanatide, an approved treatment for chronic idiopathic constipation (CIC), replicates the pH-sensitive activity of uroguanylin in binding to guanylate cyclase-C receptors on intestinal epithelium. Since many individuals with CIC experience reflux and use concomitant acid suppression therapy, we explored the impact of concomitant acid suppressor use on the efficacy and safety of plecanatide in adults with CIC. METHODS: Data on two 12-week, randomized, double-blind, placebo-controlled phase 3 clinical trials of plecanatide were pooled and results were stratified by concomitant acid suppressor use. For each group, durable overall complete spontaneous bowel movement (CSBM) response rates, changes from baseline in bowel movement frequency, stool consistency (Bristol Stool Form Scale), and daily CIC symptom scores (Likert Scale, 0 = none to 4 = very severe) were assessed. Safety was analyzed in patients who received ≥1 dose. RESULTS: The intention-to-treat population (N = 2639) included 12.6% of patients with concomitant acid suppressor use. Patients using acid suppressors were 54.8 years (mean), vs 43.9 years in those not using acid suppressors. Gastroesophageal reflux disease was more common in patients using acid suppressors (83.1%), compared to those not on acid suppressors (6.1%). Proton pump inhibitors (PPIs) were used by 86.4% of patients using acid suppressors with omeprazole as the most common PPI (45.1%); H2 blockers were used by 17.8% of subjects with ranitidine as the most common H2 blocker (9.8%). Regardless of acid suppressor use, plecanatide-treated patients demonstrated significant improvements in the durable overall CSBM responder rates (Figure 1) and greater efficacy across almost all reported endpoints (Table 1) vs placebo, with benefits observed as early as Week 1. Comparisons between acid suppressor use groups (yes vs no) were not significantly different for plecanatide-treated patients (both doses, Table 1). Of the plecanatide-treated patients on acid suppressors, 6.4% experienced diarrhea, 1.4% discontinued due to diarrhea, and 2.3% had ≥ 1 serious adverse event (SAE), compared to 5.0% (diarrhea), 2.1% (discontinued due to diarrhea), and 1.0% (SAE) of patients not using acid suppressors. CONCLUSION: Plecanatide is a safe and effective treatment for CIC when administered with acid suppression therapy. Regardless of acid suppressor use, efficacy responses in plecanatide groups were significantly greater than placebo.Figure 1.: Percentage of Patients With Durable Overall CSBM Response Stratified by Concomitant Acid Suppressor Use (ITT).Table 1.: Change From Baseline in Bowel Movement Frequency, Stool Consistency, and CIC Symptoms in Patients With and Without Concomitant Acid Suppression Therapy (ITT)

Plecanatide for the treatment of chronic idiopathic constipation in adult patients

ABSTRACTIntroduction. Chronic idiopathic constipation (CIC) is a functional gastrointestinal disorder that is associated with an increased healthcare cost and an abnormally poor quality of life. Plecanatide is a natural analog to the peptide agonist of the guanylate cyclase-C (GC-C) receptor, uroguanylin. The conversion of guanosine 5-triphosphate to cyclic guanosine monophosphate results in an increased bowel fluid secretion. Plecanatide is a promising new agent for CIC unresponsive to current therapeutic regimes.Areas covered. A comprehensive online search of Medline and the Science Citation Index was made using the keywords ‘plecanatide’, ‘guanylate cyclase-C agonists’, and ‘constipation’, in various combinations. We reviewed the pharmacodynamics, pharmacokinetics, and metabolism of this agent, and the most significant studies regarding the clinical efficacy and safety of plecanatide in CIC therapy.Expert opinion. Experimental studies showed that plecanatide was significantly better than placebo in reducing CIC severity, straining, stool consistency, bowel movements and quality of life. Apart from limited cases of diarrhea, no serious adverse events were reported. However, few data are available on its long-term safety. Furthermore, patients’ affordability of plecanatide can be limited by its costs. Finally, this new agent with a different way of action can be proposed in patients refractory to common therapy.

472 Impact of Plecanatide on Symptoms and Quality of Life for Patients With Chronic Idiopathic Constipation: Analysis of PAC-SYM and PAC-QOL From Two Phase III Clinical Trials

INTRODUCTION: Plecanatide, a 16-amino acid analog of human uroguanylin, activates guanylate cyclase-C receptors in the small intestine in a pH-sensitive manner to induce fluid secretion and peristalsis. This analysis looks at whether plecanatide improved global symptoms and health-related quality of life (HRQOL) in patients with chronic idiopathic constipation (CIC) from 2 large-scale, randomized, double-blind, placebo-controlled, phase 3 studies. METHODS: Patients (N = 2683) who met modified Rome III criteria were randomized to placebo, plecanatide 3mg, or 6mg QD for 12 weeks and included in the phase 3 intention-to-treat populations. Baseline characteristics were comparable between groups and across studies. CIC symptoms and HRQOL were evaluated using the Patient Assessment of Constipation–Symptoms (PAC-SYM) and Patient Assessment of Constipation–Quality of Life (PAC-QOL) scales, respectively. The PAC-SYM measured patients' constipation symptom experience and severity over time, including abdominal, rectal, and stool symptoms of constipation. The PAC-QOL evaluated patients' HRQOL perceptions with constipation and rated patients' worries and concerns, physical discomfort, psychosocial discomfort, satisfaction, and overall effects on HRQOL. Scales were rated from 0 to 4 with reductions in scores indicating improvement. Efficacy analyses evaluated each plecanatide dose vs placebo. RESULTS: Statistically and clinically significant improvements in PAC-SYM (∼ −0.75-point changes; Table 1) and PAC-QOL (∼ −1.0-point change; Table 2) were observed at Weeks 4, 8, and 12 for both plecanatide 3 mg and 6 mg vs placebo across both studies. Plecanatide-treated patients reported significant improvements vs placebo in all PAC-SYM domain scores, except in Study 2 for abdominal symptoms. Significant improvements in plecanatide arms vs placebo were seen in 3 of 4 PAC-QOL domain scores (worries and concerns, physical discomfort, satisfaction). The most common adverse event (AE) was diarrhea (3 mg, 4.6%; 6 mg, 5.1%; placebo, 1.3%). Discontinuation rates due to AEs were 4.1% (3 mg), 4.5% (6 mg), and 2.2% (placebo), with low discontinuation due to diarrhea (3 mg, 1.9%; 6 mg, 1.8%; placebo, 0.4%). CONCLUSION: Patients who received plecanatide 3mg and 6mg had statistically and clinically significant improvements in global constipation symptoms and HRQOL at all measured time points. Plecanatide treatment was associated with a low incidence of AEs and was well tolerated.

Guanylin, Uroguanylin and Guanylate Cyclase-C Are Expressed in the Gastrointestinal Tract of Horses.

Guanylate cyclase-C (GC-C) is a multifunctional receptor encoded by the GUCY2C gene, representing an attractive target for therapy in several gastrointestinal diseases in humans. Little is known about this system in horses. We investigated for the first time the gene expression of guanylin, uroguanylin and GC-C receptors in different horse’s gastrointestinal tracts. Tissue samples from stomach, duodenum, jejunum, ileum, head and body of cecum, left and right dorsal colon, left and right ventral colon, pelvic flexure, transverse colon, descending colon and rectum were collected from adult horses within 1 h post mortem. For each sample, total RNA was extracted from 100 mg of ground tissue, and qRT-PCR performed on GUCA2a, GUCA2b and GUCY2 transcripts on a CFX96 Touch instrument. Data analysis was carried out with Bio-Rad CFX Manager software, and genes of interest normalized relative to the abundance of the two reference genes (SDHA, HPRT). Additionally, the protein expression levels of GC-C receptor were analyzed through western blotting. A common pattern of expression throughout the gastrointestinal lumen for all three investigated transcripts was found. The expression of GUCA2a, GUCA2b and GUCY2 genes was higher in jejunum, ileum, descending colon and rectum. The levels of expression of GC-C protein confirmed these data. The findings of this study might open new scenarios for the therapeutic approach to enteric diseases of horse using selective agonists of GC-C.

Immunizations with Enterotoxigenic Escherichia coli Heat-Stable Toxin Conjugates Engender Toxin-Neutralizing Antibodies in Mice That Also Cross-React with Guanylin and Uroguanylin.

Infection with enterotoxigenic Escherichia coli (ETEC) is a common cause of childhood diarrhea in low- and middle-income countries, as well as of diarrhea among travelers to these countries. In children, ETEC strains secreting the heat-stable toxin (ST) are the most pathogenic, and there are ongoing efforts to develop vaccines that target ST. One important challenge for ST vaccine development is to construct immunogens that do not elicit antibodies that cross-react with guanylin and uroguanylin, which are endogenous peptides involved in regulating the activity of the guanylate cyclase-C (GC-C) receptor. We immunized mice with both human ST (STh) and porcine ST (STp) chemically coupled to bovine serum albumin, and the resulting sera neutralized the toxic activities of both STh and STp. This suggests that a vaccine based on either ST variant can confer cross-protection. However, several anti-STh and anti-STp sera cross-reacted with the endogenous peptides, suggesting that the ST sequence must be altered to reduce the risk of unwanted cross-reactivity. Epitope mapping of four monoclonal anti-STh and six anti-STp antibodies, all of which neutralized both STh and STp, revealed that most epitopes appear to have at least one amino acid residue shared with guanylin or uroguanylin. Despite this, only one monoclonal antibody displayed demonstrable cross-reactivity to the endogenous peptides, suggesting that targeted mutations of a limited number of ST residues may be sufficient to obtain a safe ST-based vaccine.

Linaclotide for the treatment of chronic constipation

ABSTRACTIntroduction: Chronic constipation (CC) is a common gastrointestinal disorder with limited treatment options. Linaclotide is a potent peptide agonist of the guanylate cyclase-C receptor. This action activates intracellular conversion of guanosine 5-triphosphate to cyclic guanosine monophosphate resulting in the stimulation of intestinal fluid secretion. Linaclotide is a promising new agent for refractory constipation.Areas covered: All published articles regarding the development, clinical efficacy, and safety of linaclotide in treating CC were reviewed. Pharmacodynamics, pharmacokinetics, and metabolism of this secretagogue agent were examined. Clinical studies showed that linaclotide increases the number of spontaneous bowel movements and stool consistency scores. Overall, patients reported relief from abdominal discomfort and severity of constipation. Finally, linaclotide has a good safety profile, with diarrhea being the main side effect.Expert opinion: Linaclotide appears to be a well-tolerated and effective agent for patients with CC, and could be effectively combined with other drugs in patients with refractory constipation. However, data on the efficacy and safety of linaclotide in pediatric patients and in opioid-induced constipation are currently limited and more studies need to be undertaken.

Guanylate Cyclase C: A Current Hot Target, from Physiology to Pathology.

Guanylate cyclase C (GC-C) receptor is a transmembrane receptor, predominantly expressed in intestinal epithelial cells, which is considered to play a main role in homeostasis and function of the digestive tract. The endogenous ligands for this receptor are the paracrine hormones uroguanylin and guanylin. Upon ligand binding, GC-C receptors increase cyclic guanosine monophosphate (cGMP) levels, regulating a variety of key cell-type specific processes such as chloride and bicarbonate secretion, epithelial cell growth, regulation of intestinal barrier integrity and visceral sensitivity. It has been suggested that GC-C acts as an intestinal tumor suppressor with the potential to prevent the initiation and progression of colorectal cancer. In fact, loss of ligand expression is a universal step in sporadic colorectal carcinogenesis. Interestingly, the role of GC-C is not limited to the digestive tract but it has been extended to several other systems such as the cardiovascular system, kidney, and the central nervous system, where it has been involved in a gut-hypothalamus endocrine axis regulating appetite. Objetive: In this review we summarize the physiology of the GC-C receptor and its ligands, focusing on newly developed drugs like linaclotide, and their suggested role to reverse/prevent the diseases in which the receptor is involved. Available data points toward a relationship between uroguanylin and guanylin and their receptor and pathological processes like gastrointestinal and renal disorders, colorectal cancer, obesity, metabolic syndrome and mental disorders among others. Recent pharmacological developments in the regulation of GC-receptor may involve further improvements in the treatment of relevant diseases.

Efficacy and safety of plecanatide in treating constipation predominant irritable bowel syndrome

ABSTRACTIntroduction: Uroguanylin interacting with intestinal Guanylate Cyclase C (GC-C) receptors plays an important role in gastrointestinal fluid and electrolyte homeostasis. Plecanatide is the first uroguanylin analog that stimulates GC-C receptors on gastrointestinal mucosa with pH-sensitive receptor binding. Binding to the GC-C receptor activates intracellular conversion of GTP to cGMP resulting in the stimulation of intestinal fluid secretion.Areas covered: Herein, all published research regarding the development of and clinical experience with plecanatide is reviewed. Clinical study results in patients with Chronic Idiopathic Constipation (CIC) and Irritable Bowel Syndrome with Constipation (IBS-C) are also reviewed. Success in the treatment of CIC and IBS-C is supported by beneficial effects on stool viscosity, Complete Spontaneous Bowel Movements and visceral sensation. Finally, the discussion within focuses on the importance of plecanatide in understanding the physiology of uroguanylin, the pathophysiology of IBS-C and the potential for development of uroguanylin and guanylin analogs.Expert opinion: Given this broad spectrum of potential activity for GC-C agonists, it would not be surprising to see that the use of agents such as plecanatide in new areas grow to a level even greater than the use for the present CIC and IBS-C indications.

Opioid-induced constipation

Opioids are commonly prescribed by oncology and pal­liative care physicians, with the intent of relieving suffering related to cancer pain. However, these medications have multiple side effects, opioid-induced constipation (OIC) being one of the most common adverse effects encountered in clinical practice. Several tools can be used to diagnose OIC, but asking patients about changes in bowel habits since starting opioids is essential, otherwise OIC may go undiagnosed. Multiple medications, briefly reviewed in this article, such as laxatives, peripherally acting mu-opio­id receptor antagonists, chloride channel activators, or guanylate cyclase-C receptor agonists, can be used to treat OIC once it occurs, but prevention is essential for the patient’s well-being and compliance with opioid therapy.

Therapeutically targeting guanylate cyclase-C: computational modeling of plecanatide, a uroguanylin analog.

Plecanatide is a recently developed guanylate cyclase‐C (GC‐C) agonist and the first uroguanylin analog designed to treat chronic idiopathic constipation (CIC) and irritable bowel syndrome with constipation (IBS‐C). GC‐C receptors are found across the length of the intestines and are thought to play a key role in fluid regulation and electrolyte balance. Ligands of the GC‐C receptor include endogenous agonists, uroguanylin and guanylin, as well as diarrheagenic, Escherichia coli heat‐stable enterotoxins (ST). Plecanatide mimics uroguanylin in its 2 disulfide‐bond structure and in its ability to activate GC‐Cs in a pH‐dependent manner, a feature associated with the presence of acid‐sensing residues (Asp2 and Glu3). Linaclotide, a synthetic analog of STh (a 19 amino acid member of ST family), contains the enterotoxin's key structural elements, including the presence of three disulfide bonds. Linaclotide, like STh, activates GC‐Cs in a pH‐independent manner due to the absence of pH‐sensing residues. In this study, molecular dynamics simulations compared the stability of plecanatide and linaclotide to STh. Three‐dimensional structures of plecanatide at various protonation states (pH 2.0, 5.0, and 7.0) were simulated with GROMACS software. Deviations from ideal binding conformations were quantified using root mean square deviation values. Simulations of linaclotide revealed a rigid conformer most similar to STh. Plecanatide simulations retained the flexible, pH‐dependent structure of uroguanylin. The most active conformers of plecanatide were found at pH 5.0, which is the pH found in the proximal small intestine. GC‐C receptor activation in this region would stimulate intraluminal fluid secretion, potentially relieving symptoms associated with CIC and IBS‐C.

Optimizing the Use of Linaclotide in Patients with Constipation-Predominant Irritable Bowel Syndrome: An Expert Consensus Report.

IntroductionIrritable bowel syndrome (IBS) is a functional bowel disorder characterized by chronic or recurrent abdominal pain in association with defecation or a change in bowel habits. A predominant disorder of bowel habits, IBS is classified into three main subtypes: constipation-predominant IBS (IBS-C), diarrhea-predominant IBS (IBS-D) and IBS alternating between constipation and diarrhea (IBS-M). Linaclotide is a first-in-class, oral, once-daily guanylate cyclase-C receptor agonist (GC-CA) that is licensed for the symptomatic treatment of moderate-to-severe IBS-C in adults. This review aims to facilitate and optimize clinical practices, establishing common guidelines to monitor patients with IBS-C that are treated with linaclotide.MethodsA group of experts in functional digestive disorders was convened to review the efficacy and safety of linaclotide and to develop an updated consensus report for the treatment of patients with IBS-C. A search was performed for English, French and Spanish language articles in PubMed. On the basis of the articles identified, an initial document was drafted addressing different issues frequently raised by general practitioners and GI specialists that are related to the prescription, efficacy and safety of linaclotide. This document was then reviewed and modified by the expert panel until a final text was agreed upon and validated.ResultsBased on the evidence, the panel addressed the following recommendations: (1) Linaclotide is indicated for the treatment of moderate to severe IBS-C in adults; (2) it is recommended that patients take linaclotide continuously and not sporadically; (3) patients should be warned about the risk of diarrhea and given choices concerning how to deal with this possible side effect; (4) the absence of tachyphylaxis or potential risks implies that linaclotide treatment can be maintained for long periods of time.ConclusionsThis document seeks to lay down a set of recommendations and to identify key issues that may be useful for the clinical management of IBS-C patients treated with linaclotide.

Safety and Tolerability of Plecanatide in Patients with Chronic Idiopathic Constipation: Long-term Evidence from an Open-Label Study

Introduction: Plecanatide is an orally administered 16 amino acid analog of the human GI peptide uroguanylin (UG). UG binds to and activates the guanylate cyclase-C (GC-C) receptor in the proximal small intestine in a pH-dependent manner, contributing to fluid secretion and normal bowel function. Plecanatide similarly binds to GC-C in a pH-dependent manner and is being developed for the treatment of CIC. Results are presented from the recently completed long-term, open-label study of plecanatide in CIC patients. Methods: The primary objective of this multicenter study was to assess the long term safety and tolerability of once daily plecanatide for the treatment of CIC. Patients who completed a previous double-blind study (Phase 2b or either of the two Phase 3 studies), select patients who had screen failed for either of the Phase 3 studies, or select patients who had not previously been treated with plecanatide may have been eligible for this study. Enrolled patients received 52 weeks (3mg) or up to 72 weeks (6mg) of plecanatide. Dose adjustments were not permitted. In addition to spontaneous adverse event (AE) reporting, patients completed Patient Global Assessment (PGA) questionnaires which included measures of patient satisfaction and desire to continue treatment on a scale of 1 to 5 (higher scores are better). Results: There were 2370 patient exposures in this study with the majority (90.5%) receiving treatment with the 6 mg dose; 1932 (81.5%) completed or were receiving study drug at the time the study met its enrollment goal and was ended. Treatment emergent adverse events (TEAEs) were qualitatively and quantitatively similar to those observed in prior double blindstudies. The most common AEs were diarrhea (7.1%) and urinary tract infection (2.2%). The remainder of the AEs occurred in < 2% of the patients. AEs leading to discontinuation occurred in 5.3% of patients; diarrhea leading to discontinuation occurred in 3.1%. The majority of TEAEs were mild or moderate in intensity and were generally considered not related to plecanatide treatment. The median score for treatment satisfaction was 4.0 (4=quite satisfied) and for continuation of treatment was 4.0 (4=quite likely). Conclusion: In this long term trial of CIC patients, plecanatide was well tolerated with low AE rates and low discontinuation rates. PGA assessments indicate that the patients were both satisfied with their treatment and likely to continue with plecanatide therapy.

Efficacy, Safety, and Tolerability of Linaclotide and Plecanatide for Treatment of IBS-C and Chronic Constipation: A Systematic Review and Pooled Analysis of RCT Data

Introduction: Linaclotide and plecanatide are guanylate cyclase-C receptor agonists which have demonstrated efficacy for IBS-C and Chronic Constipation (CC). The aim of this study is to assess the magnitude of benefit, safety and tolerability. Methods: MEDLINE, clinicaltrials.gov, and abstracts from DDW/ACG Annual Meetings were searched for double-blind, placebo-controlled RCTs. Study selection criteria were use of FDA-responder endpoints and medication doses approved for use and/or being studied in Phase III RCTs. Additional plecanatide data was extracted from publicly available SEC filings. Dichotomous results were pooled from RCT data to yield an unadjusted odds ratio with 95% CIs. Results: Two linaclotide Phase III RCTs in IBS-C, two linaclotide Phase III RCTs in CC, one plecanatide Phase IIb RCT in IBS-C, and one plecanatide Phase IIb RCT in CC were included. Analysis of Phase IIb plecanatide RCTs is limited to the 3.0mg dose which is being studied in Phase III RCTs. For CC, linaclotide 145ug (OR = 4.6; 95% CI = 2.7, 8.1) and plecanatide 3.0mg (OR = 2.2; 95% CI = 1.3, 3.8) were superior to placebo based on the FDA-responder endpoint. Both linaclotide (OR = 5.2; 95% CI = 3.0, 9.2) and plecanatide (OR= 8.3; 95% CI = 2.4, 43.5) were more likely than placebo to produce diarrhea. Linaclotide (OR = 10.3; 95% CI = 2.5, 91.2) was more likely than placebo to lead to discontinuing drug due to diarrhea and plecanatide trended toward this outcome (OR: = 7.1; 95% CI = 0.9, 319.5; Fisher's exact p = 0.07). For IBS-C, linaclotide 290ug (OR = 2.4; 95% CI = 1.9, 3.1) and plecanatide 3.0mg (OR = 2.6; 95% CI = 1.3, 5.5) were superior to placebo based on the 12-week FDA-responder endpoint. In a 12-week linaclotide trial (OR = 6.6, 95% CI = 3.6, 12.8), a 26-week linaclotide trial (OR = 9.6; 95% CI = 4.9, 21.1), and a 12-week plecanatide trial (OR=infinity; 95% CI: 2.25, infinity), treatment was more likely than placebo to produce diarrhea. Linaclotide led to more discontinuation of drug due to diarrhea in the 12-week trial (OR = 23.7; 95% CI = 3.8, 979.4) and 26-week trials (OR = 18.8; 95% CI = 2.9, 786.9). Plecanatide trended toward this outcome (OR=infinity, 95% CI=1.35, infinity; Fisher's Exact p = 0.06). Since zero placebo-treated patients had diarrhea in the plecanatide IBS-C RCT, ORs for diarrhea=infinity. Conclusion: Linaclotide and plecanatide both demonstrate efficacy for CC and IBS-C and report similarly increased rates of diarrhea and discontinuation due to diarrhea with IBS-C and CC.

Effect of guanylate cyclase-C activity on energy and glucose homeostasis.

Uroguanylin is a gastrointestinal hormone primarily involved in fluid and electrolyte handling. It has recently been reported that prouroguanylin, secreted postprandially, is converted to uroguanylin in the brain and activates the receptor guanylate cyclase-C (GC-C) to reduce food intake and prevent obesity. We tested central nervous system administration of two GC-C agonists and found no significant reduction of food intake. We also carefully phenotyped mice lacking the GC-C receptor and found them to have normal body weight, adiposity, and glucose tolerance. Interestingly, uroguanylin knockout mice had a small but significant increase in body weight and adiposity that was accompanied by glucose intolerance. Our data indicate that the modest effects of uroguanylin on energy and glucose homeostasis are not mediated by central GC-C receptors.

Guanylate Cyclase-C Receptor and Ligand Expression in Colonic Mucosa in Chronic Constipation

Introduction: Linaclotide is a synthetic oral peptide that binds guanylate cyclase C (GC-C) receptors in the intestinal epithelium and has demonstrated efficacy in chronic idiopathic constipation (CC). Guanylin and uroguanylin stimulate GC-C receptors which increases intracellular levels of cGMP resulting in intestinal fluid secretion and acceleration of transit time. Cyclic GMP (cGMP) transporter proteins function as an ATP-driven export pump for cyclic AMP and cGMP. The expression of GC-C receptor and ligand, uroguanylin, and guanylin, and the cGMP transporters in the human colon has not been well studied. Aims: 1) To compare the mRNA expression and protein levels of the GC-C receptor, guanylin and uroguanylin, cGMP transporter proteins, multidrug resistance protein 4 and 5 (MRP4 and MRP5) in the colonic mucosa of female patients with CC and healthy controls and, 2) To determine if there is an association with overall GI symptoms. Methods: Women between the ages of 18-55 were recruited mainly from advertisement with: 1) Rome III positive CC (30.7±11.8 years), and 2) healthy controls (34.6±10.1 years) (n=12 in each group). Subjects completed GI symptom questionnaires including overall GI symptom severity using a 21-point numeric rating scale (0-20). All subjects underwent a flexible sigmoidoscopy with random biopsies taken at 30 cm from the anal verge. RT-PCR, ELISA assays and Western blots were performed to measure mRNA expression and protein levels, respectively. Student t-tests or non-parametric Wilcoxon rank sum tests were used for group comparisons. Spearman correlation was also used. A p value of <0.05 was considered significant. Results: There were no significant group differences in mRNA expression of the GC-C receptor, GCC receptor agonists (guanylin and uroguanylin) and the cGMP transporter proteins. Similar findings were found with respect to protein levels, except for MRP4, which was significantly higher in CC patients (0.043 pg/μg) vs. controls (0.034 pg/μg) (p=0.01). The CC patients had a moderate GI symptom severity (mean 10.45±5.11 [0-20]). There was a significant negative correlation between guanylin protein levels and current overall GI symptom severity in CC patients (r= -0.701, p=0.024). Conclusion: Findings suggest that the GC-C signaling pathway plays a role in the pathogenesis and symptomatology in CC. Further studies in CC are needed to determine: 1) if mucosal guanylin levels are predictive of severity or treatment response to a GC-C agonist, and 2) the significance of increased expression of MRP4, e.g., if mucosal levels are predictive of the response to a constipation medication given that MRP4 is a drug transporter protein and confers resistance to a variety of drugs. Disclosure - Lin Chang- Consultant and Grant Support: Ironwood, Consultant: Forest. This research was supported by an industry grant from Ironwood Pharmaceuticals