Guanylate cyclase-C Signaling Axis as a theragnostic target in colorectal cancer: a systematic review of literature.

Introduction: Colorectal cancer (CRC) is a devastating disease that affects millions of people worldwide. Recent research has highlighted the crucial role of the guanylate cyclase-C (GC-C) signaling axis in CRC, from the early stages of tumorigenesis to disease progression. GC-C is activated by endogenous peptides guanylin (GU) and uroguanylin (UG), which are critical in maintaining intestinal fluid homeostasis. However, it has been found that these peptides may also contribute to the development of CRC. This systematic review focuses on the latest research on the GC-C signaling axis in CRC. Methods: According to the aim of the study, a systematic literature search was conducted on Medline and PubMed databases. Ultimately, a total of 40 articles were gathered for the systematic review. Results: Our systematic literature search revealed that alterations in GC-C signaling compartments in CRC tissue have demonstrated potential as diagnostic, prognostic, and therapeutic markers. This research highlights a potential treatment for CRC by targeting the GC-C signaling axis. Promising results from recent studies have explored the use of this signaling axis to develop new vaccines and chimeric antigen receptors that may be used in future clinical trials. Conclusion: The findings presented in this review provide compelling evidence that targeting the GC-C signaling axis may be an advantageous approach for treating CRC.

Microbiota-derived butyrate dampens linaclotide stimulation of the guanylate cyclase C pathway in patient-derived colonoids.

BACKGROUND & AIMS: Disorders of gut-brain interaction (DGBI) are complex conditions that result in decreased quality of life and a significant cost burden. Linaclotide, a guanylin cyclase C (GCC) receptor agonist, is approved as a DGBI treatment. However, its efficacy has been limited and variable across DGBI patients. Microbiota and metabolomic alterations are noted in DGBI patients, provoking the hypothesis that the microbiota may impact the GCC response to current therapeutics. METHODS: Human-derived intestinal organoids were grown from pediatric DGBI, non-IBD colon biopsies (colonoids). Colonoids were treated with 250 nM linaclotide and assayed for cGMP to develop a model of GCC activity. Butyrate was administered to human colonoids overnight at a concentration of 1 mM. Colonoid lysates were analyzed for cGMP levels by ELISA. For the swelling assay, colonoids were photographed pre- and post-treatment and volume was measured using ImageJ. Principal coordinate analyses (PCoA) were performed on the Bray-Curtis dissimilarity and Jaccard distance to assess differences in the community composition of short-chain fatty acid (SCFA) producing microbial species in the intestinal microbiota from pediatric patients with IBS and healthy control samples. KEY RESULTS: Linaclotide treatment induced a significant increase in [cGMP] and swelling of patient-derived colonoids, demonstrating a human in vitro model of linaclotide-induced GCC activation. Shotgun sequencing analysis of pediatric IBS patients and healthy controls showed differences in the composition of commensal SCFA-producing bacteria. Butyrate exposure significantly dampened linaclotide-induced cGMP levels and swelling in patient-derived colonoids. CONCLUSIONS & INFERENCES: Patient-derived colonoids demonstrate that microbiota-derived butyrate can dampen human colonic responses to linaclotide. This study supports incorporation of microbiota and metabolomic assessment to improve precision medicine for DGBI patients.

Plecanatide Improves Symptoms of Irritable Bowel Syndrome with Constipation: Results of an Integrated Efficacy and Safety Analysis of Two Phase 3 Trials.

Purpose: Patients with irritable bowel syndrome with constipation (IBS-C) experience abdominal pain with altered bowel movements. Plecanatide is indicated as IBS-C treatment in adults. This integrated analysis further characterizes plecanatide efficacy and safety in IBS-C. Patients and Methods: Data pooled from 2 identically designed phase 3 trials included adults with IBS-C randomized to plecanatide 3 mg or 6 mg, or placebo once daily for 12 weeks. A daily diary recorded stool frequency/symptoms, with abdominal pain, bloating, cramping, discomfort, fullness, and straining intensity individually rated. Overall response (primary endpoint) was defined as ≥30% improvement from baseline in average worst abdominal pain severity and increase of ≥1 complete spontaneous bowel movement, during same week (composite), for ≥6 of 12 weeks. Secondary endpoints included sustained response (overall response, plus meeting weekly composite criteria during ≥2 of last 4 treatment weeks) and changes from baseline in individual symptoms. Safety assessments included adverse event monitoring. Results: Overall, 2176 patients (74.0% female; mean [SD] age, 43.5 [14.1] years) were included in efficacy analyses (plecanatide 3 mg [n = 724], 6 mg [n = 723], placebo [n = 729]). A significantly greater percentage of patients achieved overall response with plecanatide 3 mg (25.6%) and 6 mg (26.7%) versus placebo (16.0%; both P < 0.001 vs placebo). A significantly greater percentage of patients were sustained responders with plecanatide 3 mg (24.3%) and 6 mg (25.6%) versus placebo (15.6%; both P < 0.001 vs placebo). Significant improvements from baseline in abdominal discomfort, abdominal fullness, abdominal pain, bloating, and cramping occurred as early as Week 1 (Week 2 for abdominal pain) with plecanatide and were maintained through Week 12 versus placebo. Diarrhea, the most common adverse event, occurred in 4.3% (3 mg), 4.0% (6 mg) and 1.0% (placebo) of patients, leading to study discontinuation in 1.2%, 1.4%, and 0 patients, respectively. Conclusion: Plecanatide is safe and effective for treating global and individual IBS-C symptoms.

Decoding signaling mechanisms: unraveling the targets of guanylate cyclase agonists in cardiovascular and digestive diseases.

Soluble guanylate cyclase agonists and guanylate cyclase C agonists are two popular drugs for diseases of the cardiovascular system and digestive systems. The common denominator in these conditions is the potential therapeutic target of guanylate cyclase. Thanks to in-depth explorations of their underlying signaling mechanisms, the targets of these drugs are becoming clearer. This review explains the recent research progress regarding potential drugs in this class by introducing representative drugs and current findings on them.

Role of uroguanylin's signalling pathway in the development of ischaemic stroke.

Stroke is one of the leading causes of mortality and disability worldwide. By affecting bradykinin function, activation of guanylate cyclase (GC)-A has been shown to have a neuroprotective effect after ischaemic stroke, whereas the same has not been confirmed for GC-B; therefore, we aimed to determine the possible role of GC-C and its agonist, uroguanylin (UGN), in the development of stroke. In this study, middle cerebral artery occlusion (MCAO) was performed on wild-type (WT), GC-C KO and UGN KO mice. MR images were acquired before and 24 h after MCAO. On brain slices 48 h after MCAO, the Ca2+ response to UGN stimulation was recorded. Our results showed that the absence of GC-C in GC-C KO mice resulted in the development of smaller ischaemic lesions compared with WT littermates, which is an opposite effect compared with the effects of GC-A agonists on brain lesions. WT and UGN KO animals showed a stronger Ca2+ response upon UGN stimulation in astrocytes of the peri-ischaemic cerebral cortex compared with the same cortical region of the unaffected contralateral hemisphere. This stronger activation was not observed in GC-C KO animals, which may be the reason for smaller lesion development in GC-C KO mice. The reason why GC-C might affect Ca2+ signalling in peri-ischaemic astrocytes is that GC-C is expressed in these cells after MCAO, whereas under normoxic conditions, it is expressed mainly in cortical neurons. Stronger activation of the Ca2+ -dependent signalling pathway could lead to the stronger activation of the Na+ /H+ exchanger, tissue acidification and neuronal death.

Guanylin ligand protects the intestinal immune barrier by activating the guanylate cyclase-C signaling pathway.

Inflammatory bowel disease (IBD) impacts patient quality of life significantly. The dysfunction of intestinal immune barrier is closely associated with IBD. The guanylate cyclase-C (GC-C) signaling pathway activated by the guanylin (Gn) ligand is involved in the occurrence and development of IBD. However, how it regulates the intestinal immune barrier is still unclear. To investigate the effect of the GC-C pathway on intestinal mucosal immunity and provide experimental basis for seeking new therapeutic strategies for IBD, we focused on Caco-2 cells and intestinal intra-epithelial lymphocytes (IELs), which displayed inflammatory responses induced by lipopolysaccharide (LPS). GC-C activity was modulated by transfection with Gn overexpression or GC-C shRNA plasmid. Levels of Gn, GC-C, and CFTR; transepithelial electrical resistance (TER); paracellula r permeability; and levels of IL-2, IFN-γ, and secretory IgA (sIgA) were examined. The study found that after stimulation with LPS, Gn, GC-C, CFTR, TER, and sIgA levels were all significantly reduced, IL-2 and IFN-γ levels as well as paracellular permeability were significantly increased. These indicators changed inversely and significantly after transfection with the Gn overexpression vector. Compared to the vector controls, GC-C-silenced cells displayed significantly decreased levels of GC-C, CFTR, and TER and increased levels of IL-2, IFN-γ, and paracellular permeability stimulated by LPS. The results show that Gn ligand can protect the intestinal immune barrier by activating the GC-C signaling pathway, which may be helpful for the development of new treatments for IBD. DATA AVAILABILITY STATEMENT: The data used to support the findings of this study are available from the corresponding author upon request.

Diarrheal pathogens trigger rapid evolution of the guanylate cyclase-C signaling axis in bats.

The pathogenesis of infectious diarrheal diseases is largely attributed to enterotoxins that cause dehydration by disrupting intestinal water absorption. We investigated patterns of genetic variation in mammalian guanylate cyclase-C (GC-C), an intestinal receptor targeted by bacterially encoded heat-stable enterotoxins (STa), to determine how host species adapt in response to diarrheal infections. Our phylogenetic and functional analysis of GC-C supports long-standing evolutionary conflict with diarrheal bacteria in primates and bats, with highly variable susceptibility to STa across species. In bats, we further show that GC-C diversification has sparked compensatory mutations in the endogenous uroguanylin ligand, suggesting an unusual scenario of pathogen-driven evolution of an entire signaling axis. Together, these findings suggest that conflicts with diarrheal pathogens have had far-reaching impacts on the evolution of mammalian gut physiology.

The shifting paradigm of colorectal cancer treatment: a look into emerging cancer stem cell-directed therapeutics to lead the charge toward complete remission.

Introduction: Colorectal cancer (CRC) is one of the most common forms of cancer worldwide and is the second leading cause of cancer-related death in the United States. Despite advances in early detection, ~25% of patients are late stage, and treated patients have <12% chance of survival after five years. Tumor relapse and metastasis are the main causes of patient death. Cancer stem cells (CSCs) are a rare population of cancer cells characterized by properties of self-renewal, chemo- and radio-resistance, tumorigenicity, and high plasticity. These qualities make CSCs particularly important for metastasic seeding, DNA-damage resistance, and tumor repopulating.Areas Covered: The following review article focuses on the role of CRC-SCs in tumor initiation, metastasis, drug resistance, and tumor relapse, as well as on potential therapeutic options for targeting CSCs.Expert Opinion: Current studies are underway to better isolate and discriminate CSCs from normal stem cells and to produce CSC-targeted therapeutics. The intestinal receptor, guanylate cyclase C (GUCY2C) could potentially provide a unique therapeutic target for both non-stem cells and CSCs alike in colorectal cancer through immunotherapies. Indeed, immunotherapies targeting CSCs have the potential to break the treatment-recurrence cycle in the management of advanced malignancies.

[Changes of guanylate cyclase C in colon tissues of rats with intestinal injury associated with severe acute pancreatitis].

OBJECTIVE: To explore the dynamic changes of guanylate cyclase C (GC-C) in the colon tissues of rats with intestinal injury associated with severe acute pancreatitis (SAP). OBJECTIVE: Thirty-six SD rats were randomized equally into two groups to receive either sham operation or retrograde pumping of 5% sodium taurocholate (0.1 mL/100 g) into the pancreaticobiliary duct following laparotomy to induce SAP. At 12, 24, and 48 h after modeling, 6 rats from each group were euthanized and the colon tissues were collected for Western blotting, immunohistochemistry and RT-PCR to determine the changes in GC-C expression, and the lowest GC-C expression was deemed to indicate the most serious intestinal injury and the time window for intervention. Another 18 SD rats were randomized into 3 groups for sham operation, SAP modeling or intragastric administration of linaclotide (a GC-C agonist) solution once daily at the dose of 10 µg/kg. At 12 h after modeling, the pathological changes in the pancreas and colon were observed with HE staining; the serum level of AMY, DAO, D-Lac and TNF-α were measured with ELISA, and the expressions of GC-C and claudin-1 were detected using Western blotting, immunohistochemical and transmission electron microscopy. OBJECTIVE: The expression of GC-C was significantly reduced in the colon of rats in SAP group, and its lowest expression occurred at 12 h after modeling (P < 0.05) followed by gradual increase over time. Claudin-1 showed a similar trend in the colon. Compared with the sham-operated rats, the rats in SAP and Linaclotide groups showed significantly increased pathological scores of the colon tissues (P < 0.05) and serum levels of AMY, DAO, D-Lac and TNF-α and decreased expressions of GC-C and claudin-1 in the colon (P < 0.05). Compared with those in SAP group, the rats in linaclotide group had significantly lower colonic histopathological scores, lower serum levels of AMY, DAO, D-Lac and TNF-α, and higher expression levels of GC-C and claudin-1 in the colon tissue. OBJECTIVE: In rats with SAP-related intestinal injury, the expression of GC-C in the colon tissue decreases to the lowest level at 12 h after SAP onset followed by gradual increase. activating GC-C can increase the expression levels of GC-C and claudin-1 and alleviate intestinal injury, suggesting the role of GC-C in maintaining intestinal barrier integrity by regulating the expression of tight junction proteins.

Peripheral Guanylate Cyclase-C modulation of corticolimbic activation and corticotropin-releasing factor signaling in a rat model of stress-induced colonic hypersensitivity.

BACKGROUND: Psychological stress is a risk factor for irritable bowel syndrome, a functional gastrointestinal pain disorder featuring abnormal brain-gut connectivity. The guanylate cyclase-C (GC-C) agonist linaclotide has been shown to relieve abdominal pain in IBS-C and exhibits antinociceptive effects in rodent models of post-inflammatory visceral hypersensitivity. However, the role GC-C signaling plays in psychological stress-induced visceral hypersensitivity is unknown. Here, we test the hypothesis that GC-C agonism reverses stress-induced colonic hypersensitivity via inhibition of nociceptive afferent signaling resulting in normalization of stress-altered corticotropin-releasing factor (CRF) expression in brain regions involved in pain perception and modulation. METHODS: Adult female rats were exposed to water avoidance stress or sham stress for 10 days, and the effects of linaclotide on stress-induced changes in colonic sensitivity, corticolimbic phospho-extracellular signal-regulated kinase (pERK), and CRF expression were measured using a combination of behavioral assessments, immunohistochemistry, and qRT-PCR. KEY RESULTS: Stressed rats exhibited colonic hypersensitivity and elevated corticolimbic pERK on day 11, which was inhibited by linaclotide. qRT-PCR analysis revealed dysregulated CRF expression in the medial prefrontal cortex, paraventricular nucleus of the hypothalamus, and central nucleus of the amygdala on day 28. Dysregulated CRF expression was not affected by linaclotide treatment. CONCLUSIONS AND INFERENCES: Our results demonstrate that exposure to repeated stress induces chronic colonic hypersensitivity in conjunction with altered corticolimbic activation and CRF expression. GC-C agonism attenuated stress-induced colonic hypersensitivity and ERK phosphorylation, but had no effect on CRF expression, suggesting the analgesic effects of linaclotide occur independent of stress-driven CRF gene expression in corticolimbic circuitry.

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 constipation-predominant irritable bowel syndrome.

Introduction: As an analogue of uroguanylin plecanatide binds to the Guanylate Cyclase-C receptor activating fluid and ion secretion in the small intestine with the same pH-dependent binding kinetics as the natural ligand. Plecanatide has been FDA approved as safe and effective for the indications of Chronic Idiopathic Constipation (CIC) and Irritable Bowel Syndrome with Constipation (IBS-C).Areas covered: All clinical trial results supporting approval of plecanatide in IBS-C are reported, evaluated and interpreted in the context of the complex pathophysiology of functional diseases and the barriers that must be overcome for appropriate protocol design and conduct.Expert opinion: The Expert Opinion section discusses safety and efficacy of plecanatide for IBS-C. Broader consideration of some of the inherent challenges in understanding and treating functional gastrointestinal disorders includes: 1. the difficulty of understanding diseases with complex pathophysiology that clinically present with a few simple symptoms, 2. exploring the pathophysiology of functional diseases using pharmacophysiology, 3. value of 'Set Theory' in the evaluation of complex clinical data and 4. physiologic and pathophysiologic insight gained by evaluation 'physiologic redundancy' and 'conservation of function'.

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.

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.

NHERF3 is necessary for Escherichia coli heat-stable enterotoxin-induced inhibition of NHE3: differences in signaling in mouse small intestine and Caco-2 cells.

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of childhood death from diarrhea and the leading cause of Traveler's diarrhea. E. coli heat-stable enterotoxin (ST) is a major virulence factor of ETEC and inhibits the brush border Na/H exchanger NHE3 in producing diarrhea. NHE3 regulation involves multiprotein signaling complexes that form on its COOH terminus. In this study, the hypothesis was tested that ST signals via members of the Na/H exchanger regulatory factor (NHERF) family of scaffolding proteins, NHERF2, which had been previously shown to have a role, and now with concentration on a role for NHERF3. Two models were used: mouse small intestine and Caco-2/BBe cells. In both models, ST rapidly increased intracellular cGMP, inhibited NHE3 activity, and caused a quantitatively similar decrease in apical expression of NHE3. The transport effects were NHERF3 and NHERF2 dependent. Also, mutation of the COOH-terminal amino acids of NHERF3 supported that NHERF3-NHERF2 heterodimerization was likely to account for this dual dependence. The ST increase in cGMP in both models was partially dependent on NHERF3. The intracellular signaling pathways by which ST-cGMP inhibits NHE3 were different in mouse jejunum (activation of cGMP kinase II, cGKII) and Caco-2 cells, which do not express cGKII (elevation of intracellular Ca2+ concentration [Ca2+]i). The ST elevation of [Ca2+]i was from intracellular stores and was dependent on NHERF3-NHERF2. This study shows that intracellular signaling in the same diarrheal model in multiple cell types may be different; this has implications for therapeutic strategies, which often assume that models have similar signaling mechanisms.

Silencing the GUCA2A-GUCY2C tumor suppressor axis in CIN, serrated, and MSI colorectal neoplasia.

Colorectal cancers (CRCs) initiate through distinct mutations, including in APC pathway components leading to tubular adenomas (TAs); in BRAF, with epigenetic silencing of CDX2, leading to serrated adenomas (SAs); and in the DNA mismatch repair machinery driving microsatellite instability (MSI). Transformation through the APC pathway involves loss of the hormone GUCA2A that silences the tumor-suppressing receptor GUCY2C. Indeed, oral hormone replacement is an emerging strategy to reactivate GUCY2C and prevent CRC initiation and progression. Moreover, retained expression by tumors arising from TAs has established GUCY2C as a diagnostic and therapeutic target to prevent and treat metastatic CRC. Here, we defined the potential role of the GUCA2A-GUCY2C axis and its suitability as a target in tumors arising through the SA and MSI pathways. GUCA2A hormone expression was eliminated in TAs, SAs, and MSI tumors compared to their corresponding normal adjacent tissues. In contrast to the hormone, the tumor-suppressing receptor GUCY2C was retained in TA and MSI tumors. Surprisingly, GUCY2C expression was nearly eliminated in SAs, reflecting loss of the transcription factor CDX2. Changes in the GUCA2A-GUCY2C axis in human SAs and MSI tumors were precisely recapitulated in genetic mouse models. These data reveal the possibility of GUCA2A loss silencing GUCY2C in the pathophysiology of, and oral hormone replacement to restore GUCY2C signaling to prevent, MSI tumors. Also, they highlight the potential for targeting GUCY2C to prevent and treat metastases arising from TA and MSI tumors. In contrast, loss of GUCY2C excludes patients with SAs as candidates for GUCY2C-based prevention and therapy.

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.

Genetic and transcriptional analysis of inflammatory bowel disease-associated pathways in patients with GUCY2C-linked familial diarrhea.

OBJECTIVE: Activating mutations in the GUCY2C gene, which encodes the epithelial receptor guanylate cyclase C, cause diarrhea due to increased loss of sodium chloride to the intestinal lumen. Patients with familial GUCY2C diarrhea syndrome (FGDS) are predisposed to inflammatory bowel disease (IBD). We investigated whether genes in the guanylate cyclase C pathway are enriched for association with IBD and reversely whether genetic or transcriptional changes associated with IBD are found in FGDS patients. METHODS: (1) A set of 27 genes from the guanylate cyclase C pathway was tested for enrichment of association with IBD by Gene Set Enrichment Analysis, using genome-wide association summary statistics from 12,882 IBD patients and 21,770 controls. (2) We genotyped 163 known IBD risk loci and sequenced NOD2 in 22 patients with FGDS. Eight of them had concomitant Crohn's disease. (3) Global gene expression analysis was performed in ileal tissue from patients with FGDS, Crohn's disease and healthy individuals. RESULTS: The guanylate cyclase C gene set showed a significant enrichment of association in IBD genome-wide association data. Risk variants in NOD2 were found in 7/8 FGDS patients with concomitant Crohn's disease and in 2/14 FDGS patients without Crohn's disease. In ileal tissue, downregulation of metallothioneins characterized FGDS patients compared to healthy controls. CONCLUSIONS: Our results support a role of guanylate cyclase C signaling and disturbed electrolyte homeostasis in development of IBD. Furthermore, downregulation of metallothioneins in the ileal mucosa of FGDS patients may contribute to IBD development, possibly alongside effects from NOD2 risk variants.

A randomized controlled and long-term linaclotide study of irritable bowel syndrome with constipation patients in Japan.

BACKGROUND: Clinical testing was required to verify the effect of linaclotide 0.5 mg/d in patients with irritable bowel syndrome with constipation (IBS-C) in Japan. METHODS: This was a randomized, double-blind, placebo-controlled (Part 1) and long-term, open-label extension (Part 2) study of linaclotide at 60 hospitals and clinics in Japan. Patients with IBS-C diagnosed using Rome III criteria (n = 500) were randomly assigned to linaclotide 0.5 mg (n = 249) or placebo (n = 251) for a 12-week treatment period followed by open-label treatment with linaclotide (n = 324) for an additional 40 weeks. The primary endpoints were the responder rate of global improvement of IBS symptoms and complete spontaneous bowel movement (CSBM) during 12 weeks. The secondary endpoints included responder rates of SBM and abdominal pain/discomfort relief. KEY RESULTS: Part 1: The responder rates for global improvement and for CSBM frequency were significantly higher for linaclotide compared to placebo (P < 0.001). Secondary endpoints including responder rates for SBM and abdominal pain/discomfort relief in the linaclotide group were also significantly greater than those in the placebo group. Part 2: Patients switched from placebo to linaclotide showed similar responder rates for global improvement and CSBM frequency to those in patients who continued to receive linaclotide, supporting sustained efficacy. Diarrhea was seen in 14.5% of patients; all cases were mild or moderate. CONCLUSIONS AND INFERENCES: This study suggests that a linaclotide dose of 0.5 mg is effective and safe for IBS-C patients in Japan.