NHE3 inhibitor tenapanor maintains intestinal barrier function, decreases visceral hypersensitivity, and attenuates TRPV1 signaling in colonic sensory neurons.

The pathogenesis of irritable bowel syndrome (IBS) is multifactorial, characterized in part by increased intestinal permeability, and visceral hypersensitivity. Increased permeability is associated with IBS severity and abdominal pain. Tenapanor is FDA-approved for the treatment of IBS with constipation (IBS-C) and has demonstrated improvements in bowel motility and a reduction in IBS-related pain; however, the mechanism by which tenapanor mediates these functions remains unclear. Here, the effects of tenapanor on colonic pain signaling and intestinal permeability were assessed through behavioral, electrophysiological, and cell culture experiments. Intestinal motility studies in rats and humans demonstrated that tenapanor increased luminal sodium and water retention and gastrointestinal transit versus placebo. A significantly reduced visceral motor reflex (VMR) to colonic distension was observed with tenapanor treatment versus vehicle in two rat models of visceral hypersensitivity (neonatal acetic acid sensitization and partial restraint stress; both P < 0.05), returning VMR responses to that of nonsensitized controls. Whole cell voltage patch-clamp recordings of retrogradely labeled colonic dorsal root ganglia (DRG) neurons from sensitized rats found that tenapanor significantly reduced DRG neuron hyperexcitability to capsaicin versus vehicle (P < 0.05), an effect not mediated by epithelial cell secretions. Tenapanor also attenuated increases in intestinal permeability in human colon monolayer cultures caused by incubation with proinflammatory cytokines (P < 0.001) or fecal supernatants from patients with IBS-C (P < 0.005). These results support a model in which tenapanor reduces IBS-related pain by strengthening the intestinal barrier, thereby decreasing permeability to macromolecules and antigens and reducing DRG-mediated pain signaling.NEW & NOTEWORTHY A series of nonclinical experiments support the theory that tenapanor inhibits IBS-C-related pain by strengthening the intestinal barrier. Tenapanor treatment reduced visceral motor responses to nonsensitized levels in two rat models of hypersensitivity and reduced responses to capsaicin in sensitized colonic nociceptive dorsal root ganglia neurons. Intestinal permeability experiments in human colon monolayer cultures found that tenapanor attenuates increases in permeability induced by either inflammatory cytokines or fecal supernatants from patients with IBS-C.

Abdominal Symptom Improvement During Clinical Trials of Tenapanor in Patients With Irritable Bowel Syndrome With Constipation: A Post Hoc Analysis.

INTRODUCTION: This post hoc analysis evaluated the efficacy of tenapanor on abdominal symptoms in patients with irritable bowel syndrome with constipation. Abdominal symptoms assessed included pain, discomfort, bloating, cramping, and fullness. METHODS: The abdominal symptom data were pooled from 3 randomized controlled trials (NCT01923428, T3MPO-1 [NCT02621892], and T3MPO-2 [NCT02686138]). Weekly scores were calculated for each abdominal symptom, and the Abdominal Score (AS) was derived as the average of weekly scores for abdominal pain, discomfort, and bloating. The overall change from baseline during the 12 weeks was assessed for each symptom weekly score and the AS. The AS 6/12-week and 9/12-week response rates (AS improvement of ≥2 points for ≥6/12- or ≥9/12-week) were also evaluated. The association of weekly AS response status (reduction of ≥30%) with weekly complete spontaneous bowel movement (CSBM) status (=0 and >0) was assessed. RESULTS: Among 1,372 patients (684 tenapanor [50 mg twice a day] and 688 placebo), the least squares mean change from baseline in AS was -2.66 for tenapanor vs -2.09 for placebo ( P < 0.0001). The 6/12-week AS response rate was 44.4% for tenapanor vs 32.4% for placebo ( P < 0.0001), and for 9/12-week AS, 30.6% for tenapanor vs 20.5% for placebo ( P < 0.0001). A significant association between weekly CSBM status and weekly AS response status was observed each week ( P < 0.0001), with a greater proportion achieving an AS reduction in patients with >0 CSBMs in a week. DISCUSSION: Tenapanor significantly reduced abdominal symptoms in patients with irritable bowel syndrome with constipation, particularly pain, discomfort, and bloating measured by AS, compared with placebo.

Tenapanor: A Phosphate Absorption Inhibitor for the Management of Hyperphosphatemia in Patients With Kidney Failure.

Because of increased risks of cardiovascular disease and death, patients with hyperphosphatemia receiving maintenance dialysis are advised to limit phosphorus consumption and are prescribed phosphate binders in an effort to better control serum phosphate concentrations. Because of large pill size, pill burden, and tolerability issues, phosphate binder adherence is relatively poor. On ingestion, phosphate is absorbed from the intestine via transcellular or paracellular transport. Data show that inhibiting sodium-hydrogen exchanger 3 modulates paracellular phosphate absorption (the predominant pathway in humans). Tenapanor is a first-in-class, minimally absorbed, phosphate absorption inhibitor that selectively inhibits sodium-hydrogen exchanger 3, with a mechanism distinct from, and complementary to, that of phosphate binders. In phase 3 and postregistrational studies, tenapanor conferred statistically significant and clinically meaningful reductions in serum phosphate in patients receiving maintenance dialysis with hyperphosphatemia. Here, we review the available preclinical and clinical data on the effects of tenapanor on controlling intestinal phosphate absorption.

Intestinal Permeability, Irritable Bowel Syndrome with Constipation, and the Role of Sodium-Hydrogen Exchanger Isoform 3 (NHE3).

Increased intestinal permeability has been identified as one of the many pathophysiological factors associated with the development of irritable bowel syndrome (IBS), a common disorder of gut-brain interaction. The layer of epithelial cells that lines the intestine is permeable to a limited degree, and the amount of paracellular permeability is tightly controlled to enable the absorption of ions, nutrients, and water from the lumen. Increased intestinal permeability to macromolecules can be triggered by a variety of insults, including infections, toxins from food poisoning, or allergens, which in turn cause an inflammatory response and are associated with abdominal pain in patients with IBS. This review article discusses increased intestinal permeability in IBS, focusing on IBS with constipation (IBS-C) through the lens of a patient case with a reported prior diagnosis of "leaky gut syndrome" upon initial contact with a gastrointestinal specialist. We review advantages and disadvantages of several methods of measuring intestinal permeability in patients and discuss when measuring intestinal permeability is appropriate in the therapeutic journey of patients with IBS-C. Furthermore, we discuss a possible mechanism of restoring the intestinal barrier to its healthy state through altering intracellular pH by inhibiting sodium-hydrogen exchanger isoform 3 (NHE3). Tenapanor is a minimally absorbed, small-molecule inhibitor of NHE3 that has been approved by the US Food and Drug Administration for the treatment of IBS-C in adults. Preclinical studies showed that tenapanor may restore the intestinal barrier in IBS-C by affecting the conformation of tight junction proteins via NHE3 inhibition to block the paracellular transport of macromolecules from the intestinal lumen. Testing for increased permeability in patients with IBS-C who experience abdominal pain may help inform the choice of therapeutics and alter patients' misconceptions about "leaky gut syndrome".

Review of the Patient Burden and Therapeutic Landscape of Irritable Bowel Syndrome with Constipation in the United States.

Irritable bowel syndrome (IBS) is a common disorder of the gut-brain axis. IBS with constipation (IBS-C) accounts for approximately one-third of IBS cases and is associated with substantial burden of illness and decreased quality of life. This narrative review provides an overview of the current and upcoming treatment options and disease management for IBS-C from a US perspective and discusses the importance of the relationship between patient and health care provider in diagnosis and treatment. A positive diagnostic strategy for IBS-C is recommended, based on clinical history, physical examination, and minimal laboratory tests. An effective communication strategy between patients and health care professionals is essential to ensure early diagnosis and reduce both health care costs and overall disease burden. Treatment typically begins with lifestyle interventions and nonpharmacologic options, such as dietary interventions, fiber supplements, and osmotic laxatives. In patients with inadequate response to these therapies, 4 currently available therapies (lubiprostone, linaclotide, plecanatide, and tenapanor) approved by the US Food and Drug Administration may relieve IBS-C symptoms. These agents are generally well tolerated and efficacious in improving IBS-C symptoms, including constipation and abdominal pain. In patients with persistent abdominal pain and/or psychological symptoms, brain-gut behavioral therapy or neuromodulator therapy may be beneficial.

An Overview of the Effects of Tenapanor on Visceral Hypersensitivity in the Treatment of Irritable Bowel Syndrome with Constipation.

Background: Patients with irritable bowel syndrome with constipation (IBS-C) experience persistent abdominal pain, a common symptom leading to greater healthcare utilization and reports of treatment non-response. Clinically significant improvements in abdominal pain were observed in clinical trials of tenapanor, a first-in-class inhibitor of sodium/hydrogen exchanger isoform 3 (NHE3), for the treatment of IBS-C in adults. Aim: This narrative review reports the current knowledge about visceral hypersensitivity as a mechanism for abdominal pain in patients with IBS-C and explores the published evidence for hypothesized mechanisms by which tenapanor may reduce visceral hypersensitivity leading to the observed clinical response of decreased abdominal pain. Findings: Abdominal pain is experienced through activation and signaling of nociceptive dorsal root ganglia that innervate the gut. These sensory afferent neurons may become hypersensitized through signaling of transient receptor potential cation channel subfamily V member 1 (TRPV1), resulting in reduced action potential thresholds. TRPV1 signaling is also a key component of the proinflammatory cascade involving mast cell responses to macromolecule exposure following permeation through the intestinal epithelium. Indirect evidence of this pathway is supported by observations of higher pain in association with increased intestinal permeability in patients with IBS. Tenapanor reduces intestinal sodium absorption, leading to increased water retention in the intestinal lumen, thereby improving gastrointestinal motility. In animal models of visceral hypersensitivity, tenapanor normalized visceromotor responses and normalized TRPV1-mediated nociceptive signaling. Conclusion: By improving gastrointestinal motility, decreasing intestinal permeability and inflammation, and normalizing nociception through decreased TRPV1 signaling, tenapanor may reduce visceral hypersensitivity, leading to less abdominal pain in patients with IBS-C. Therapies that have demonstrated effects on visceral hypersensitivity may be the future direction for meaningful abdominal pain relief for patients with IBS-C.

Long-term safety of tenapanor in patients with irritable bowel syndrome with constipation in the T3MPO-3 study.

BACKGROUND: Tenapanor, a first-in-class, minimally systemic inhibitor of intestinal sodium/hydrogen exchanger isoform 3 (NHE3), is approved for the treatment of irritable bowel syndrome with constipation (IBS-C) in adults based on two randomized, placebo-controlled, phase III studies (T3MPO-1 [NCT02621892], T3MPO-2 [NCT02686138]). The open-label T3MPO-3 extension study (NCT02727751) enrolled patients who completed these studies to investigate long-term safety and tolerability of tenapanor. METHODS: Patients who completed T3MPO-1 (16 weeks) or T3MPO-2 (26 weeks) were eligible for enrollment in T3MPO-3. Patients in T3MPO-3 received open-label tenapanor 50 mg twice a day for up to an additional 39 (T3MPO-1) or 26 (T3MPO-2) weeks. Treatment-emergent adverse events (TEAEs) were evaluated in the entire T3MPO-3 safety population and in patients who received a total of ≥52 weeks of tenapanor. KEY RESULTS: A total of 312 patients were enrolled in T3MPO-3; 90 received ≥52 weeks of tenapanor. TEAEs were reported in 117 (37.5%) patients in the safety population and in 52 (57.8%) patients who received ≥52 weeks of tenapanor. Diarrhea was the most common TEAE, occurring in 10.6% of the safety population and in 11.1% of patients who received ≥52 weeks of tenapanor. Most cases were mild or moderate in severity, with only two severe cases reported in the safety population. No deaths occurred during the T3MPO-3 study. CONCLUSIONS: Tenapanor was tolerable over ≥52 weeks of treatment and showed similar safety to that seen in shorter studies. Combined results of the T3MPO studies indicate that tenapanor is a valuable new treatment option for patients with IBS-C.

Tenapanor improves long-term control of high phosphate concentrations in the blood in patients receiving maintenance dialysis: a plain language summary of the NORMALIZE study.

What is this summary about?This is a summary of an article that was published in the medical journal Kidney360 describing results from the NORMALIZE study. The NORMALIZE study looked at how well tenapanor tablets reduced higher-than-normal levels of phosphate in the blood of persons with kidney disease who are on maintenance dialysis. These persons are unable to keep their blood phosphate levels in a normal range, and high levels of phosphate can contribute to several serious health consequences.Tenapanor is approved as an add-on treatment for high levels of phosphate in the blood of adults with chronic kidney disease who are on maintenance dialysis and whose disease does not respond adequately to treatment with phosphate binders or who are not able to take phosphate binders. In earlier clinical studies, tenapanor was studied alone or studied together with phosphate binders. In a 1-year clinical study called PHREEDOM, researchers learned that when tenapanor was used alone, it lowered blood phosphate levels, and treated patients experienced acceptable safety and tolerability as determined by the doctors running the study. In the NORMALIZE study, adult patients took a 30-mg tenapanor tablet twice a day, either alone or with sevelamer, for up to 18 months after they completed the PHREEDOM study.What were the main conclusions reported by the researchers?The researchers found that one-third of patients taking tenapanor, either alone or with sevelamer, achieved normal blood phosphate levels. This is an improvement from the current standard of care with sevelamer alone to reduce blood phosphate levels. As seen in the earlier studies of tenapanor, the most common adverse event experienced by patients was softer or loose stools. No new safety concerns were reported in the NORMALIZE study.What are the key takeaways?The researchers concluded that tenapanor, used alone or combined with sevelamer, can be used long-term by adult patients receiving maintenance dialysis to reduce the phosphate levels in their blood to within the normal range. Patients who take tenapanor may experience softer or loose stools.This summary was developed by the authors to help adult patients with chronic kidney disease receiving dialysis, and their family members and/or caregivers, better understand the effects of taking tenapanor.[Box: see text]Link to original article here.

Effectiveness of tenapanor for treating hyperphosphatemia in patients receiving dialysis: a plain language summary of the OPTIMIZE study.

What is this summary about?This summary provides a review of the OPTIMIZE study, the results of which were published in Kidney360 in February 2024. The OPTIMIZE study looked at how well tenapanor tablets work to treat patients receiving dialysis who have high levels of phosphate in their blood, a condition called hyperphosphatemia. In the OPTIMIZE study, researchers wanted to understand if tenapanor would decrease phosphate levels in the blood to the target range. They also tested different ways of starting tenapanor treatment in patients.In the human body, kidneys are organs that filter blood and remove waste products. In chronic kidney disease, sometimes referred to as CKD, a patient's kidneys do not work as well at filtering their blood and removing waste products. This can allow phosphate to build up in the blood. Phosphate levels may remain high despite patients receiving treatment such as dialysis, using pills that keep phosphate in the intestines (called phosphate binders) to prevent phosphate from being absorbed into the blood, and eating a low-phosphate diet. Phosphate levels may remain high despite these treatments because they can be difficult to follow. Most people receiving dialysis take 7­8 phosphate binder pills every day, and over half of those people have reported skipping at least one dose in the past month. Additionally, low-phosphate diets can be difficult to follow and people often struggle to meet their other nutritional needs.What are the key takeaways?Tenapanor used in combination with phosphate binders led to lower phosphate levels in the blood with the use of fewer phosphate-lowering pills. Tenapanor also lowered phosphate levels in patients who were not previously on phosphate binders but needed phosphate-lowering treatment.What were the main conclusions reported by the researchers?Tenapanor can help patients receiving dialysis better control their hyperphosphatemia.[Box: see text]Link to original article here.

Infectious enteritis after intestinal transplantation: incidence, timing, and outcome.

BACKGROUND: The study reviews the incidence, timing, and outcome of infectious enteritis (IE) after intestinal transplantation (ITx). METHODS: A retrospective review of all patients who underwent ITx at a single institution between 1991 and 2003 was undertaken using database and medical records. Standard statistical analyses were performed. RESULTS: Of 33 ITx recipients, 13 (39%) developed 20 culture- or biopsy-proven episodes of IE. Recipient demographics included the following: 10 males, median age 34 (10-585) months, 11 liver + intestine grafts, and two isolated intestine grafts. Infections were diagnosed a median of 76 days (32-1,800 days) after ITx. There were 14 viral (one cytomegalovirus, eight rotavirus, four adenovirus, one Epstein-Barr virus), three bacterial (Clostridium difficile), and three protozoal (one Giardia lamblia, two Cryptosporidium) infections. The bacterial infections tended to present earlier than the viral infections, and the most frequent presenting symptom was diarrhea. Complete resolution was achieved in 17 (94%) incidences with the appropriate antimicrobial or conservative therapy. It was interesting that there were seven rejection episodes documented by biopsy at the approximate time of diagnosis of IE. There were two graft losses: one because of adenoviral enteritis and one because of rejection after rotavirus enteritis. Three-year patient survival is 74% with no deaths directly attributable to IE. CONCLUSIONS: IE can occur in 39% of recipients after ITx. Viral agents are the cause in two thirds of the cases. With supportive care and appropriate treatment, resolution is possible in the majority of cases. Differentiating rejection and infection on histopathology can be difficult and relies on cultures and immunostaining.

Older children in preadoptive homes: issues before termination of parental rights.

In many jurisdictions, after the end of reunification services to birthparents, but before termination of parental rights, children are placed with parents who are licensed as foster parents but are committed to adopting the child. Using case examples, this article discusses the emotional and psychological difficulties often encountered by children and their prospective adoptive parents when birthparent visitation takes place and legal uncertainties exist. In addition, this article offers clinical and policy recommendations to help both the children and families in these situations as well as the professionals who work with them.

Varicella in pediatric liver transplant patients: a retrospective analysis of treatment and outcome.

BACKGROUND: Varicella is a common childhood disease that can cause morbidity and mortality among immunosuppressed patients. There have been few previous studies monitoring the course of pediatric liver transplant patients with acute varicella. The aim of this study was to evaluate the treatment, outcomes, and complications of pediatric liver transplant patients admitted with acute varicella infection. METHODS: A retrospective chart review was carried out based on discharge diagnoses of orthotopic liver transplant and varicella among pediatric patients (age range, birth-18 years) admitted to the UCLA Medical Center between 1985 and 2001. RESULTS: Five hundred fifty-six pediatric patients received liver transplantations between 1985 and 2001. Twenty-two of these patients were admitted to the UCLA Medical Center with varicella (11 females, 11 males). No patients were treated on an outpatient basis. Mean age of the patients was 6 years (range, 1-16 years). None of these patients received the varicella vaccine before hospitalization. On admission, 5 of 22 patients (23%) had received varicella zoster immunoglobulin within 96 hours of exposure. The mean length of hospitalization was 6 days (range, 2-11 days). All immunosuppression dosages were reduced during the admissions. None of the patients had been treated with high-dose corticosteroids for acute rejection before the onset of the varicella infection. Patients were treated until defervescence with intravenous acyclovir and until their varicella lesions crusted. Patients were discharged with oral acyclovir to complete a 10-day course (including the intravenous treatment). No patients had complications from the varicella infection. A complication of an elevated serum creatinine for one patient was noted with the intravenous acyclovir treatment. This patient had associated headache and nausea that resolved when the creatinine level returned to normal. CONCLUSIONS: There were no complications or dissemination of varicella infection among our pediatric liver transplant patients. Further prospective randomized trials are required to evaluate the management of pediatric liver transplant patients infected with varicella.