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The effects of tenapanor on serum fibroblast growth factor 23 in patients receiving hemodialysis with hyperphosphatemia.

ABSTRACT: Background:Elevated serum fibroblast growth factor 23 (FGF23) is strongly associated with cardiovascular risk and mortality. Tenapanor, an inhibitor of gastrointestinal sodium/hydrogen exchanger isoform 3, decreased serum phosphate in a randomized, double-blind, placebo-controlled Phase 2 trial (ClinicalTrials.gov identifier NCT02081534) of patients receiving hemodialysis with hyperphosphatemia. Here, we report a secondary analysis of effects on serum FGF23 during that study. Methods:After 1-3 weeks of washout of phosphate binders, 162 patients were randomized to receive 4 weeks of treatment with placebo or one of six tenapanor regimens (3 or 30 mg once daily, or 1, 3, 10 or 30 mg twice daily). Intact FGF23 concentrations were determined from serum samples collected at screening, post-washout and end of treatment, assayed in duplicate in a single batch at the end of the study. Results:After phosphate-binder washout, serum FGF23 concentrations increased in all groups [range of geometric means: 1430-2605 pg/mL before, to 2601-6294 pg/mL after washout (P?

SUBMITTER: Block GA

PROVIDER: S-EPMC6365767 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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The effects of tenapanor on serum fibroblast growth factor 23 in patients receiving hemodialysis with hyperphosphatemia.

Block Geoffrey A GA Rosenbaum David P DP Yan Andrew A Greasley Peter J PJ Chertow Glenn M GM Wolf Myles M

Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association 20190201 2

<h4>Background</h4>Elevated serum fibroblast growth factor 23 (FGF23) is strongly associated with cardiovascular risk and mortality. Tenapanor, an inhibitor of gastrointestinal sodium/hydrogen exchanger isoform 3, decreased serum phosphate in a randomized, double-blind, placebo-controlled Phase 2 trial (ClinicalTrials.gov identifier NCT02081534) of patients receiving hemodialysis with hyperphosphatemia. Here, we report a secondary analysis of effects on serum FGF23 during that study.<h4>Methods< ...[more]

PMID: 29617976

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Project description:IntroductionPhosphate binders are used to treat hyperphosphatemia. Some patients have inappropriately controlled serum phosphorus levels, which may occur for many reasons, including a high pill burden and adverse events (AEs). Tenapanor selectively inhibits the passive paracellular transfer of phosphate in the gastrointestinal tract, thereby reducing serum phosphorus levels. This novel mechanism of action may contribute to improved phosphate management. The efficacy and safety of tenapanor have not been evaluated in Japanese patients with high serum phosphorus levels despite treatment with phosphate binders. This study aimed to assess the efficacy and safety of add-on tenapanor therapy for reducing serum phosphorus levels in this population.MethodsThis multicenter, double-blind, randomized, placebo-controlled trial enrolled patients with refractory hyperphosphatemia undergoing hemodialysis. Patients were randomly assigned in a 1:1 ratio to receive tenapanor or placebo as an add-on to their phosphate binder regimen for 6 weeks. Change in serum phosphorus levels at week 6 (day 43) compared with the baseline value (day 1, week 0) (primary endpoint), achievement of target serum phosphorus levels (serum phosphorus level ≤6.0 or ≤5.5 mg/dL), and safety, based on all AEs and drug-related AEs, were among the outcomes evaluated.ResultsIn total, 24 patients were randomly assigned to the placebo group and 23 to the tenapanor group. The mean serum phosphorus level decreased from 7.01 mg/dL on day 1 to 6.69 mg/dL on day 43 in the placebo group and from 6.77 mg/dL on day 1 to 4.67 mg/dL on day 43 in the tenapanor group. In the placebo and tenapanor groups (modified intent-to-treat population), the mean (standard deviation) change in the serum phosphorus level at day 43 (last observation carried forward [LOCF]) was 0.08 (1.52) mg/dL and -1.99 (1.24) mg/dL, respectively, with a between-group difference of -2.07 (95% confidence interval: -2.89, -1.26; p < 0.001). The target achievement rate (serum phosphorus level ≤6.0 mg/dL at week 6 [LOCF]) was 37.5 and 87.0% in the placebo and tenapanor groups, respectively. Diarrhea was the most common drug-related AE, and it occurred in 8.3 and 65.2% of patients in the placebo and tenapanor groups, respectively. No specific AEs were observed with add-on tenapanor or with phosphate binders.Discussion/conclusionTherapy with existing phosphate binders and add-on tenapanor resulted in a significant decrease in serum phosphorus level compared with the placebo group in patients with refractory hyperphosphatemia despite treatment with phosphate binders. No new safety signals were raised, and add-on tenapanor was generally well tolerated.

Project description:BackgroundFibroblast growth factor 23 (FGF-23) is a hormone that increases the rate of urinary excretion of phosphate and inhibits renal production of 1,25-dihydroxyvitamin D, thus helping to mitigate hyperphosphatemia in patients with kidney disease. Hyperphosphatemia and low 1,25-dihydroxyvitamin D levels are associated with mortality among patients with chronic kidney disease, but the effect of the level of FGF-23 on mortality is unknown.MethodsWe examined mortality according to serum phosphate levels in a prospective cohort of 10,044 patients who were beginning hemodialysis treatment and then analyzed FGF-23 levels and mortality in a nested case-control sample of 200 subjects who died and 200 who survived during the first year of hemodialysis treatment. We hypothesized that increased FGF-23 levels at the initiation of hemodialysis would be associated with increased mortality.ResultsSerum phosphate levels in the highest quartile (>5.5 mg per deciliter [1.8 mmol per liter]) were associated with a 20% increase in the multivariable adjusted risk of death, as compared with normal levels (3.5 to 4.5 mg per deciliter [1.1 to 1.4 mmol per liter]) (hazard ratio, 1.2; 95% confidence interval [CI], 1.1 to 1.4). Median C-terminal FGF-23 (cFGF-23) levels were significantly higher in case subjects than in controls (2260 vs. 1406 reference units per milliliter, P<0.001). Multivariable adjusted analyses showed that increasing FGF-23 levels were associated with a monotonically increasing risk of death when examined either on a continuous scale (odds ratio per unit increase in log-transformed cFGF-23 values, 1.8; 95% CI, 1.4 to 2.4) or in quartiles, with quartile 1 as the reference category (odds ratio for quartile 2, 1.6 [95% CI, 0.8 to 3.3]; for quartile 3, 4.5 [95% CI, 2.2 to 9.4]; and for quartile 4, 5.7 [95% CI, 2.6 to 12.6]).ConclusionsIncreased FGF-23 levels appear to be independently associated with mortality among patients who are beginning hemodialysis treatment. Future studies might investigate whether FGF-23 is a potential biomarker that can be used to guide strategies for the management of phosphorus balance in patients with chronic kidney disease.

Project description:Rationale & objectivePatients with chronic kidney failure have markedly elevated fibroblast growth factor 23 (FGF-23) levels and decreased soluble Klotho levels. However, no studies have examined the effects of hemodialysis initiation on the levels of these hormones and other parameters of mineral metabolism.Study designProspective single-arm study.Setting & participants20 individuals with incident kidney failure initiating hemodialysis.ExposureInitiation of hemodialysis. Dose adjustments of phosphate binders and vitamin D receptor activators and use of calcimimetics, erythropoiesis-stimulating agents, and intravenous iron were prohibited.OutcomesChanges in serum levels of FGF-23, soluble Klotho, and other biochemical parameters of mineral metabolism, measured before and after each hemodialysis session, for a total of 4 sessions over 5 days.Analytical approachRepeated-measures analysis of variance.ResultsAt baseline, participants had 18-fold higher median FGF-23 levels and 1.6-fold lower mean soluble Klotho levels compared with age- and sex-matched healthy individuals. Initiation of hemodialysis led to progressive reductions in serum phosphorus, intact parathyroid hormone, and FGF-23 levels, with dialysis-related fluctuations. No reductions were observed in levels of α1-microglobulin, which has molecular weight comparable to FGF-23. The magnitude of the FGF-23 level reductions was strongly associated with concomitant changes in serum phosphorus levels but not with the changes in intact parathyroid hormone levels. Soluble Klotho levels did not change after the initiation of hemodialysis.LimitationsSingle-arm design, small sample size, short follow-up period.ConclusionsInitiation of hemodialysis in patients with chronic kidney failure led to progressive reductions in FGF-23 levels in association with reductions in serum phosphorus levels. These results suggest that phosphorus is a strong inducer of FGF-23 production and that regulation of FGF-23 production is a rapid process.

Project description:Hyp mice possess a mutation that inactivates the phosphate-regulating gene, which is homologous to the endopeptidases of the X-chromosome (PHEX). The mutation is associated with severe hypophosphatemia due to excessive urinary phosphate wasting. Such urinary phosphate wasting in Hyp mice is associated with an increased serum accumulation of fibroblast growth factor (FGF) 23. We wanted to determine the biological significance of increased serum FGF23 levels and concomitant hypophosphatemia in Hyp mice and to evaluate whether FGF23 activity could be modified by manipulating klotho (a cofactor of FGF23 signaling). We generated Hyp and klotho double-mutant mice (Hyp/klotho(-/-)). Severe hypophosphatemia of Hyp mice was reversed to hyperphosphatemia in Hyp/klotho(-/-) double mutants, despite the fact that the double mutants showed significantly increased serum levels of FGF23. Hyperphosphatemia in Hyp/klotho(-/-) mice was associated with increased renal expression of sodium/phosphate cotransporter 2a (NaPi2a) protein. Exogenous injection of bioactive parathyroid hormone 1-34 down-regulated renal expression of NaPi2a and consequently reduced serum levels of phosphate in Hyp/klotho(-/-) mice. Moreover, in contrast to the Hyp mice, the Hyp/klotho(-/-) mice showed significantly higher serum levels of 1,25-dihydroxyvitamin D and developed extensive calcification in soft tissues and vascular walls. Furthermore, compared with the Hyp mice, Hyp/klotho(-/-) mice were smaller in size, showed features of generalized tissue atrophy, and generally died by 15-20 wk of age. Our in vivo studies provide genetic evidence for a pathological role of increased FGF23 activities in regulating abnormal phosphate homeostasis in Hyp mice. Moreover, these results suggest that even when serum levels of FGF23 are significantly high, in the absence of klotho, FGF23 is unable to regulate systemic phosphate homeostasis. Our in vivo observations have significant clinical implications in diseases associated with increased FGF23 activity and suggest that the functions of FGF23 can be therapeutically modulated by manipulating the effects of klotho.

Dataset Information

The effects of tenapanor on serum fibroblast growth factor 23 in patients receiving hemodialysis with hyperphosphatemia.

Publications

The effects of tenapanor on serum fibroblast growth factor 23 in patients receiving hemodialysis with hyperphosphatemia.

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