Deciphering ion transporters, kinases and PDZ-adaptor molecules that mediate guanylate cyclase C agonist-dependent intestinal fluid loss in vivo.

BACKGROUND: The molecular basis for heat-stable Escherichia coli enterotoxin (STa) action and its synthetic analogue linaclotide is well understood at the enterocyte level. Pharmacologic strategies to prevent STa-induced intestinal fluid loss by inhibiting its effector molecules, however, have achieved insufficient inhibition in vivo. AIMS AND EXPERIMENTAL APPROACH: To investigate whether the currently discussed effector molecules and signaling mechanisms of STa/linaclotide-induced diarrhea have similar relevance in vivo than at the enterocyte level, we studied the effect of 10-7M of the STa analogue linaclotide on short circuit current (Isc) of chambered isolated jejunal mucosa, and on the in vivo action on fluid transport in a perfused segment of proximal jejunum of anesthetized mice. The selected mice were deficient of transport (NHE3, CFTR, Slc26a3/a6), adaptor (NHERF1-3), or signal transduction molecules [cGMP-dependent kinase II (GKII)] considered to be downstream effectors after STa/linaclotide binding to guanylate cyclase C (GCC). Selective NHE3 inhibition by tenapanor was also employed. KEY RESULTS, CONCLUSIONS AND IMPLICATIONS: The comparison allowed the separation of effectors for stimulation of electrogenic anion secretion and for inhibition of electrolyte/fluid absorption in response to STa/linaclotide. The cGKII-NHERF1-CFTR and cGKII-NHERF2-NHE3 interactions are indeed major effectors of small intestinal fluid loss downstream of GCC activation in vitro and in vivo, but 50% of the linaclotide-induced fluid loss in vivo, while dependent on CFTR activation and NHE3 inhibition, does not involve cGKII, and 30% does not depend on NHERF1 or NHERF2. A combined NHERF1 and NHERF2 inhibition appears nevertheless a good pharmacological strategy against STa-mediated fluid loss.

Plecanatide for the treatment of chronic idiopathic constipation in adult patients.

Introduction. 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.

Safety and tolerability of linaclotide for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation: pooled Phase 3 analysis.

BACKGROUND: Linaclotide is approved for treating irritable bowel syndrome with constipation (IBS-C; 290 µg QD) and chronic idiopathic constipation (CIC; 145 µg or 72 µg QD). These analyses aimed to assess linaclotide safety in a large, pooled Phase 3 population. METHODS: In six randomized controlled trials (RCTs), patients received linaclotide (72 µg, 145 µg, 290 µg) or placebo daily for 12-26 weeks; in two long-term safety (LTS) studies, patients received open-label linaclotide for ≤78 additional weeks. Laboratory values, vital signs, and treatment-emergent adverse events (TEAEs) were assessed. RESULTS: Overall, 3853 patients received ≥1 dose of linaclotide. The most common TEAE was diarrhea (majority [90.5% in RCTs] mild/moderate). Linaclotide patients experienced 1.1 diarrhea TEAE per patient-year in the RCTs (0.2 in placebo), and 0.3 in the LTS studies. In RCTs, 6.9% linaclotide and 3.0% placebo patients discontinued due to any adverse event (AE); 4.0% linaclotide and 0.3% placebo patients discontinued due to diarrhea. In LTS studies, 9.4% patients discontinued due to any AE, and 3.8% due to diarrhea. Serious AEs (SAEs) were rare and similar across treatment groups; there were no SAEs of diarrhea. CONCLUSION: These pooled analyses of patients treated for ≤104 weeks confirm linaclotide's overall safety.

Efficacy and Tolerability of Guanylate Cyclase-C Agonists for Irritable Bowel Syndrome with Constipation and Chronic Idiopathic Constipation: A Systematic Review and Meta-Analysis.

OBJECTIVES: Linaclotide and plecanatide are guanylate cyclase-C (GCC) agonists for the treatment of chronic idiopathic constipation (CIC) and irritable bowel syndrome with constipation (IBS-C). Our objective is to evaluate the efficacy and tolerability of GCC agonists based on data from multiple randomized controlled trials (RCTs). METHODS: We searched PubMED, EMBASE, Cochrane databases, clinicaltrials.gov, major conference abstracts, Food and Drug Administration (FDA) websites, and United States Securities and Exchange Commission filings of drug sponsors to identify RCTs of CIC or IBS-C patients. We assessed efficacy based on FDA-approved composite responder endpoints, diarrhea as an adverse event, and study withdrawal owing to diarrhea for each therapy. Trial results were pooled using DerSimonian and Laird random effects model of meta-analysis and exact logistic regression when appropriate with 95% confidence intervals. Meta-regression was performed to compare outcomes between therapies adjusting for placebo event rate. RESULTS: Eight linaclotide trials (five CIC; three IBS-C) and seven plecanatide trials (four CIC; three IBS-C) evaluating 10,369 patients met inclusion criteria. FDA publications documented that different definitions for diarrhea were used in linaclotide vs. plecanatide trials. Both drugs were efficacious in treating CIC (linaclotide 72 µg (Odds ratio (OR)=3.11, 95% CI 1.81-5.34); linaclotide 145 µg (OR=3.25, 2.15-4.91); plecanatide 3 mg (OR=1.99, 1.57-2.51)) and IBS-C (linaclotide 290 µg (OR=2.43, 1.48-3.98); plecanatide 3 mg (OR=1.87, 1.47-2.38); plecanatide 6 mg (OR=1.92, 1.48-2.48)). Diarrhea occurred in excess of placebo in treating CIC (linaclotide 72 µg (OR=3.07, 1.97-4.77); linaclotide 145 µg (OR=3.70, 2.69-5.10); plecanatide 3 mg (OR=3.86, 1.83-8.12)) and IBS-C (linaclotide 290 µg (OR=8.02, 5.20-12.37); plecanatide 3 mg (OR=5.55, 1.62-19.00); plecanatide 6 mg (OR=4.13, 1.57-10.83)). Based on meta-regression, there were no statistically significant differences between therapies in odds ratios for efficacy, diarrhea, or diarrhea-related study withdrawals. CONCLUSIONS: Both linaclotide and plecanatide demonstrate similar efficacy and tolerability in treating IBS-C and CIC. No differences in odds of diarrhea were seen between linaclotide and plecanatide.

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

BACKGROUND AND AIM: Linaclotide is a guanylate cyclase-C agonist approved in multiple countries to treat irritable bowel syndrome with constipation (IBS-C). China has unmet need for well-tolerated therapy that is effective in treating both bowel and abdominal symptoms of IBS-C. This trial evaluated linaclotide's efficacy and safety in IBS-C patients in China and other regions. METHODS: This Phase 3, double-blind trial randomized IBS-C patients to once-daily oral 290-µg linaclotide or placebo at centers in China, North America, and Oceania. Patients reported bowel and abdominal symptoms daily; adverse events were monitored. Co-primary and secondary endpoints were tested using a predefined three-step serial gatekeeping multiple comparisons procedure. RESULTS: The intent-to-treat population included 839 patients (mean age = 41 years; 82% female; 81% Asian). The trial met all co-primary and secondary endpoints. Co-primary responder criteria were met by 60.0% of linaclotide patients versus 48.8% of placebo patients for abdominal pain/discomfort (≥ 30% decrease for ≥ 6/12 weeks; P < 0.05), and 31.7% of linaclotide versus 15.4% of placebo patients for IBS degree of relief (score ≤ 2 for ≥ 6/12 weeks; P < 0.0001). Secondary 12-week change-from-baseline endpoints (spontaneous bowel movement/complete spontaneous bowel movement frequency, stool consistency, straining, abdominal pain, abdominal discomfort, and abdominal bloating) were significantly improved with linaclotide versus placebo (all P < 0.0001). Diarrhea was the most common adverse event (9.4% linaclotide, 1.2% placebo). Discontinuation rates due to diarrhea were low (0.7% linaclotide, 0.2% placebo). CONCLUSIONS: Once-daily 290-µg linaclotide improved bowel habits, abdominal symptoms, and global measures in a predominantly Chinese IBS-C population.