Randomized Study of Tenapanor Added to Phosphate Binders for Patients With Refractory Hyperphosphatemia

High-salt diets provoke phosphorus absorption from the small intestine in mice

BACKGROUND

Recent studies indicate that tenapanor, an inhibitor of sodium/proton exchanger-3 (NHE3), diminishes intestinal phosphorus (Pi) absorption. Given NHE3's pivotal role in sodium (Na+) metabolism, there is a suspected functional link between Na+ and Pi metabolism. High-salt diets (HSD) have been demonstrated to disrupt calcium (Ca2+) metabolism. Since Ca2+ and Pi share analogous metabolic pathways, it is yet to be determined whether HSD also impacts Pi metabolism.

METHODS

Male C57 mice were randomly assigned to three groups: a standard diet group, HSD groups for 1 week (HSD-1w) and 4 weeks (HSD-4w). Throughout the study, dietary intake and water consumption were monitored using metabolic cages, and urine and feces were collected. Blood pressure was measured using a noninvasive tail vein sphygmomanometer. Upon completion of the intervention, mice were euthanized under anesthesia for blood collection, and intestinal and renal tissues were harvested for molecular analysis.

RESULTS

Although plasma Pi levels were comparable between HSD groups and the control group, HSD groups exhibited increased urinary Pi excretion and decreased fecal Pi excretion. The HSD-4w group displayed elevated parathyroid hormone levels, reduced fibroblast growth factor 23 levels, and higher renal Cyp27b1 mRNA expression. The expression of sodium-dependent phosphate transporter 2b (Npt2b) and NHE3 was elevated in the intestine of HSD mice.

CONCLUSION

HSD disrupts Pi metabolism by enhancing urinary Pi excretion and altering hormonal levels. The decrease in fecal Pi excretion, coupled with the upregulation of intestinal Pi transporter expression, suggests that HSD promotes intestinal Pi absorption in mice.

Tenapanor: A novel therapeutic agent for dialysis patients with hyperphosphatemia

Patients on dialysis often develop hyperphosphatemia, contributing to an increased risk of cardiovascular events and mortality. Currently, several types of phosphate binders (PBs) exist for the treatment of hyperphosphatemia, but they are sometimes associated with drug-specific side effects and high pill burden, making it difficult to control serum phosphorus appropriately. Tenapanor, which has a novel mechanism to reduce serum phosphorus via selective sodium/proton exchange transporter 3 inhibition, was approved for hyperphosphatemia in Japan in 2023. Four phase 3 studies of tenapanor have been performed in Japan and have demonstrated its efficacy and safety as a single-agent drug, add-on effects to PBs for patients with refractory hyperphosphatemia that cannot be improved with PBs alone, and reduction of the pill burden associated with PBs. This review provides an overview of the characteristics and previous clinical studies of tenapanor and describes the clinical benefits of tenapanor over current therapy in patients on dialysis.

Efficacy and safety of tenapanor vs placebo in treating CKD patients on dialysis and with hyperphosphatemia: a systematic review and meta-analysis of 2251 patients

BACKGROUND

Hyperphosphatemia is common in chronic kidney disease (CKD) patients, especially patients on hemodialysis. Tenapanor is a novel drug with fewer side effects and high compliance compared to traditional phosphate binders. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of tenapanor.

METHODS

A comprehensive search was conducted on PubMed, Scopus, Web of Science, and Cochrane Library, from inception to June 25, 2024. Nine randomized controlled trials (RCTs) and three single-arm studies comparing tenapanor to placebo were included. By adopting a random-effect empirical Bayes model, STATA and RevMan were used to pool dichotomous and continuous data. The primary outcome assessed was serum phosphate. Secondary outcomes included intact parathyroid hormone (iPTH), serum calcium, potassium, and sodium, bowel movement frequency, stool consistency using BSFS score and safety outcomes.

RESULTS

Twelve studies with a total of 2,251 patients were included. Tenapanor was superior to placebo in reducing phosphate at all assessed end points, week 1 (MD = -1.28 mg/dL, P < 0.001), week 2 (MD = -1.07 mg/dL, P < 0.001), week 3 (MD = -1.22 mg/dL, P < 0.001), and week 4 (MD = -0.91 mg/dL, P < 0.001). In addition, iPTH was almost statistically significantly lower in the tenapanor group (MD = -36.53 ng/L, P = 0.07). Moreover, it led to a statistically significant reduction in sodium level (MD = -0.7 mmol/L, P = 0.0003). On the contrary, tenapanor had no statistically significant effect on calcium or potassium levels. Bowel movement frequency and stool consistency were significantly higher in the tenapanor group at all assessed end points. Regarding safety analysis, diarrhea and nausea were statistically significantly higher in the tenapanor group, (RR = 3.71, P < 0.001) and (RR = 1.97, P < 0.001), respectively. There were no significant differences in other adverse events.

CONCLUSION

Based on our meta-analysis, tenapanor can effectively reduce serum phosphate, iPTH, and sodium. Additionally, it improves bowel movement frequency and stool consistency. However, it is associated with a higher risk of GIT symptoms that should be considered and managed during treatment. We recommend conducting further RCTs to perform head-to-head comparisons against other active comparators such as phosphate binders.

Efficacy and safety of tenapanor in end-stage renal disease patients with hyperphosphatemia: a systematic review and meta-analysis

BACKGROUND

Hyperphosphatemia occurs universally in end-stage renal disease(ESRD), and the attainment of target serum phosphate levels remains suboptimal with currently available phosphate binders. This meta-analysis aimed to evaluate the efficacy and safety of tenapanor in end-stage renal disease patients with hyperphosphatemia.

METHODS

Data sources included PubMed, Embase, Web of Science, and Cochrane Library. This meta-analysis included randomized controlled trials evaluating both the efficacy of tenapanor in reducing serum phosphate levels and its safety profile. The risk of bias was assessed using the Cochrane risk of bias tool for RCTs. The GRADE system was used to assess the overall certainty of evidence. A meta-analysis was carried out by using fixed effects (I2 values < 50%) or random effects (I2 values ≥ 50%) models to calculate MD with 95% CI for continuous outcome variables and RR with 95% CI for dichotomous variables. Publication bias was evaluated using funnel plots.

RESULTS

A total of seven RCTs involving 877 individuals were included. The pooling analysis demonstrates that the reduction in mean serum phosphorus levels in the tenapanor group was significantly greater than that in the placebo group [MD= -1.06 mg/dl, 95% CI (-1.59, -0.53); I2 = 83%, p < 0.0001]. The proportion of patients achieving a serum phosphorus level of < 5.5 mg/dL, along with the incidence of any adverse events (AEs) and gastrointestinal disorders, was higher in the tenapanor group compared to the placebo group.

CONCLUSION

Tenapanor has the potential to significantly reduce serum phosphorus levels and enhance the rate of achieving target levels compared to placebo, all while maintaining an acceptable safety and tolerability profile.

REGISTRATION

PROSPERO registration number CRD42024544531.