Efficacy and Safety of a Novel Nicotinamide Modified-Release Formulation in the Treatment of Refractory Hyperphosphatemia in Patients Receiving Hemodialysis-A Randomized Clinical Trial

Citrate-Buffered, Magnesium-Enriched Dialysate on Calcification Propensity in Hemodialysis Patients - The CitMag Study

Introduction

Serum calcification propensity (T50 time) is associated with mortality in patients on dialysis. Several solitary interventions improve T50. However, whether a combination of interventions yields further increases in T50 is unknown. We hypothesized that a combination of 2 interventions, namely increasing magnesium concentration while simultaneously substituting acetate for citrate in the dialysis fluid, leads to increases in T50 values.

Methods

In a randomized controlled trial, 60 patients on chronic hemodialysis were allocated to either continue on standard (S) dialysate (3 mmol/l acetate, 0.5 mmol/l magnesium) or a sequence of magnesium-enriched (Mg0.75) dialysate (3 mmol/l acetate, 0.75 mmol/l magnesium) for 2 weeks followed by combination treatment using citrate-buffered, magnesium-enriched (Cit+Mg0.75) dialysate (1 mmol/l citrate, 0.75 mmol/l magnesium) for 3 weeks. The primary end point was the difference in T50 times between the S group and the Cit+Mg0.75 group.

Results

There was no significant difference in T50 time between the S group and the Cit+Mg0.75 group (236 ± 77 vs. 265 ± 97 min, P = 0.23). The size (hydrodynamic radius) of secondary calciprotein particles did not differ between the S group and the Cit+Mg0.75 group (294 ± 95 vs. 309 ± 91 nm, P = 0.56). In longitudinal analyses, serum magnesium concentrations increased from 1.07 ± 0.17 to 1.24 ± 0.17 mmol/l with the Mg0.75 dialysate (P < 0.0001) but decreased again to 1.19 ± 0.16 mmol/l with the Cit+Mg0.75 dialysate (P < 0.0001).

Conclusion

The combination of citrate buffer with increased magnesium concentration in dialysate does not improve T50.

The Effect of Niacinamide Supplementation on Phosphate Concentrations in Dutch Dialysis Patients: A Randomized Crossover Trial

OBJECTIVE

Hyperphosphatemia is a common complication in patients with kidney failure, despite the use of phosphate binders. Vitamin B3, either in the form of niacin or niacinamide (NAM), shows potential as "add-on" treatment to reduce serum phosphate concentrations in this population. NAM seems to lack many of the side effects that are observed with niacin. The aim of this study was to investigate whether NAM is an effective and acceptable treatment in reducing serum phosphate concentrations in patients with kidney failure.

METHODS

DiaNia was a double-blind placebo-controlled randomized crossover trial, comparing NAM (250-500 mg/day) to placebo as "add-on" treatment to an individual treatment with approved phosphate binders for 12 weeks in patients receiving hemodialysis. The primary outcome was serum phosphate concentrations, and the secondary outcomes were platelet counts as well as drop-outs due to side effects. Data were analyzed using both per-protocol and intention-to-treat analyses.

RESULTS

Mean age of the per-protocol population (n = 26) was 63.6 ± 17.2 years and 53.8% were men. NAM treatment significantly reduced serum phosphate with 0.59 mg/dL (p = .03). Linear mixed-effects models demonstrated superiority of 12 weeks NAM over 12 weeks placebo with a between-treatment difference of 0.77 mg/dL (95% CI 0.010, 1.43; P = .03). Similar results, although not significant, were found in the intention-to-treat population. We found no between-treatment differences in platelet counts and during the NAM treatment we observed 3 drop-outs due to side effects (8.6%).

CONCLUSION

NAM is effective in reducing serum phosphate concentrations in patients with kidney failure receiving hemodialysis. In addition, NAM is well-tolerated and seems not to increase the risk of thrombocytopenia. Thus, NAM can be valuable as "add-on" treatment to combat hyperphosphatemia in patients with kidney failure. However, more research in larger populations is needed to confirm this.

Pharmacology of Mammalian Na+-Dependent Transporters of Inorganic Phosphate

Inorganic phosphate (Pi) is an essential component of many biologically important molecules such as DNA, RNA, ATP, phospholipids, or apatite. It is required for intracellular phosphorylation signaling events and acts as pH buffer in intra- and extracellular compartments. Intestinal absorption, uptake into cells, and renal reabsorption depend on a set of different phosphate transporters from the SLC20 (PiT transporters) and SLC34 (NaPi transporters) gene families. The physiological relevance of these transporters is evident from rare monogenic disorders in humans affecting SLC20A2 (Fahr's disease, basal ganglia calcification), SLC34A1 (idiopathic infantile hypercalcemia), SLC34A2 (pulmonary alveolar microlithiasis), and SLC34A3 (hereditary hypophosphatemic rickets with hypercalciuria). SLC34 transporters are inhibited by millimolar concentrations of phosphonoformic acid or arsenate while SLC20 are relatively resistant to these compounds. More recently, a series of more specific and potent drugs have been developed to target SLC34A2 to reduce intestinal Pi absorption and to inhibit SLC34A1 and/or SLC34A3 to increase renal Pi excretion in patients with renal disease and incipient hyperphosphatemia. Also, SLC20 inhibitors have been developed with the same intention. Some of these substances are currently undergoing preclinical and clinical testing. Tenapanor, a non-absorbable Na+/H+-exchanger isoform 3 inhibitor, reduces intestinal Pi absorption likely by indirectly acting on the paracellular pathway for Pi and has been tested in several phase III trials for reducing Pi overload in patients with renal insufficiency and dialysis.

Intact FGF23 predicts serum phosphate improvement after combined nicotinamide and phosphate binder treatment in hemodialysis patients

Background

Hyperphosphatemia is associated with increased mortality and cardiovascular morbidity of end-stage kidney failure (ESKF) patients. Managing serum phosphate in ESKF patients is challenging and mostly based on limiting intestinal phosphate absorption with low phosphate diets and phosphate binders (PB). In a multi-centric, double-blinded, placebo-controlled study cohort of maintenance hemodialysis patients with hyperphosphatemia, we demonstrated the efficacy of nicotinamide modified release (NAMR) formulation treatment in addition to standard PB therapy in decreasing serum phosphate. Here we aimed to assess the relationship between phosphate, FGF23, inflammation and iron metabolism in this cohort.

Methods

We measured the plasma concentrations of intact fibroblast growth factor 23 (iFGF23) and selected proinflammatory cytokines at baseline and Week 12 after initiating treatment.

Results

We observed a strong correlation between iFGF23 and cFGF23 (C-terminal fragment plus iFGF23). We identified iFGF23 as a better predictor of changes in serum phosphate induced by NAMR and PB treatment compared with cFGF23. Recursive partitioning revealed at baseline and Week 12, that iFGF23 and cFGF23 together with T50 propensity were the most important predictors of serum phosphate, whereas intact parathyroid hormone (iPTH) played a minor role in this model. Furthermore, we found serum phosphate and iPTH as the best predictors of iFGF23 and cFGF23. Sex, age, body mass index, and markers of inflammation and iron metabolism had only a minor impact in predicting FGF23.

Conclusion

Lowering serum phosphate in ESKF patients may depend highly on iFGF23 which is correlated to cFGF23 levels. Serum phosphate was the most important predictor of plasma FGF23 in this ESKF cohort.

The open system of FGF-23 at the crossroad between additional P-lowering therapy, anemia and inflammation: how to deal with the intact and the C-terminal assays?

Fibroblast growth factor 23 (FGF-23) has been associated with increased cardiovascular risk and poor survival in dialysis patients. It is well established that FGF-23 synthesis is directly induced by positive phosphate (P) balance. On the other hand, P-lowering treatments such as nutritional P restriction, P binders and dialysis are capable of reducing FGF-23 levels. However, there are many uncertainties regarding the possibility of adopting FGF-23 to guide the clinical decision-making process in the context of chronic kidney disease-mineral bone disorder (CKD-MBD). Furthermore, the best assay to adopt for measurement of FGF-23 levels (namely the intact vs the C-terminal one) remains to be determined, especially in conditions capable of altering the synthesis as well as the cleavage of the intact and biologically active molecule, as occurs in the presence of CKD and its complications. This Editorial discusses the main insights provided by the post hoc analysis of the NOPHOS trial, with particular attention given to evidence-based peculiarities of the intact and the C-terminal assays available for measuring FGF-23 levels, especially in patients receiving additive P-lowering therapy in the presence of inflammation, anemia and iron deficiency.

[Research Progress in Niacinamide in the Prevention and Treatment of Mouth and Systemic Diseases]

Nicotinamide (NAM) is the amide form of niacin and one of the precursors of nicotinamide adenine dinucleotide (NAD +). NAM can be used as a dietary supplement or clinical therapeutic drug to replenish NAD + levels in the human body and participate in key bodily functions such as cellular metabolism and DNA repair. NAM has the advantage of low cost, wide availability, and sound biosafety. It also has multiple biological functions, including antibacterial effect, anti-inflammatory effect, and modulation of cellular immunity, producing significant ameliorative effects on skin and neurodegenerative diseases. However, most studies on NAM are still at the laboratory stage. Herein we reviewed the role and mechanism of NAM in the prevention and treatment of oral and systemic diseases, explored its potential as clinical therapeutic medication, provided some basis and references for the clinical application of nicotinamide in the prevention and treatment of various diseases, and discussed its prospects for future research and application.

NAD+ Metabolism and Interventions in Premature Renal Aging and Chronic Kidney Disease

Premature aging causes morphological and functional changes in the kidney, leading to chronic kidney disease (CKD). CKD is a global public health issue with far-reaching consequences, including cardio-vascular complications, increased frailty, shortened lifespan and a heightened risk of kidney failure. Dialysis or transplantation are lifesaving therapies, but they can also be debilitating. Currently, no cure is available for CKD, despite ongoing efforts to identify clinical biomarkers of premature renal aging and molecular pathways of disease progression. Kidney proximal tubular epithelial cells (PTECs) have high energy demand, and disruption of their energy homeostasis has been linked to the progression of kidney disease. Consequently, metabolic reprogramming of PTECs is gaining interest as a therapeutic tool. Preclinical and clinical evidence is emerging that NAD⁺ homeostasis, crucial for PTECs' oxidative metabolism, is impaired in CKD, and administration of dietary NAD⁺ precursors could have a prophylactic role against age-related kidney disease. This review describes the biology of NAD⁺ in the kidney, including its precursors and cellular roles, and discusses the importance of NAD⁺ homeostasis for renal health. Furthermore, we provide a comprehensive summary of preclinical and clinical studies aimed at increasing NAD⁺ levels in premature renal aging and CKD.

Serum Calcification Propensity Represents a Good Biomarker of Vascular Calcification: A Systematic Review

Vascular calcification contributes to cardiovascular morbidity and mortality. A recently developed serum calcification propensity assay is based on the half-transformation time (T50) from primary calciprotein particles (CPPs) to secondary CPPs, reflecting the serum’s endogenous capacity to prevent calcium phosphate precipitation. We sought to identify and review the results of all published studies since the development of the T50-test by Pasch et al. in 2012 (whether performed in vitro, in animals or in the clinic) of serum calcification propensity. To this end, we searched PubMed, Elsevier EMBASE, the Cochrane Library and Google Scholar databases from 2012 onwards. At the end of the selection process, 57 studies were analyzed with regard to the study design, sample size, characteristics of the study population, the intervention and the main results concerning T50. In patients with primary aldosteronism, T50 is associated with the extent of vascular calcification in the abdominal aorta. In chronic kidney disease (CKD), T50 is associated with the severity and progression of coronary artery calcification. T50 is also associated with cardiovascular events and all-cause mortality in CKD patients, patients on dialysis and kidney transplant recipients and with cardiovascular mortality in patients on dialysis, kidney transplant recipients, patients with ischemic heart failure and reduced ejection fraction, and in the general population. Switching from acetate-acidified dialysate to citrate-acidified dialysate led to a longer T50, as did a higher dialysate magnesium concentration. Oral administration of magnesium (in CKD patients), phosphate binders, etelcalcetide and spironolactone (in hemodialysis patients) was associated with a lower serum calcification propensity. Serum calcification propensity is an overall marker of calcification associated with hard outcomes but is currently used in research projects only. This assay might be a valuable tool for screening serum calcification propensity in at-risk populations (such as CKD patients and hemodialyzed patients) and, in particular, for monitoring changes over time in T50.

Phosphate balance during dialysis and after kidney transplantation in patients with chronic kidney disease

PURPOSE OF REVIEW

In patients with chronic kidney disease (CKD), hyperphosphatemia is associated with several adverse outcomes, including bone fragility and progression of kidney and cardiovascular disease. However, there is a knowledge gap regarding phosphate balance in CKD. This review explores its current state, depending on the stage of CKD, dialysis modalities, and the influence of kidney transplantation.

RECENT FINDINGS

Adequate phosphate control is one of the goals of treatment for CKD-mineral and bone disorder. However, ongoing studies are challenging the benefits of phosphate-lowering treatment. Nevertheless, the current therapy is based on dietary restriction, phosphate binders, and optimal removal by dialysis. In the face of limited adherence, due to the high pill burden, adjuvant options are under investigation. The recent discovery that intestinal absorption of phosphate is mostly paracellular when the intraluminal concentration is adequate might help explain why phosphate is still well absorbed in CKD, despite the lower levels of calcitriol.

SUMMARY

Future studies could confirm the benefits of phosphate control. Greater understanding of the complex distribution of phosphate among the body compartments will help us define a better therapeutic strategy in patients with CKD.

Modified-release nicotinamide for the treatment of hyperphosphataemia in haemodialysis patients: 52-week efficacy and safety results of the phase III randomised controlled NOPHOS trial

BACKGROUND

We previously reported that modified-release nicotinamide (NAMR) was superior to placebo in reducing serum phosphate concentrations over 12 weeks in a large cohort of haemodialysis patients with hyperphosphataemia. Here, we report outcomes after 52 weeks of treatment.

METHODS

NOPHOS was a phase III, international, randomised, controlled, double-blind trial in parallel group design. NAMR (250-1500 mg/d) was investigated in comparison to placebo as an add-on therapy to an individual therapy with approved phosphate binders.

RESULTS

In the intention-to-treat population (NAMR: N = 539, placebo: N = 183), serum phosphate was significantly lower in the NAMR group compared to the placebo group at W24 (5.40 ± 1.55 mg/dl vs. 5.79 ± 1.37 mg/dl,  P < 0.001) with a mean difference of -0.39 mg/dl [95% CI -0.66, -0.13], but was comparable between the groups at W52 (mean difference -0.08 [95% CI -0.36, 0.20]). In the completer population (N = 358), statistical significance in favour of NAMR was reached at W24 and W52. The treatment effect was reduced in patients with high baseline serum intact parathyroid hormone (iPTH) compared to patients with low baseline serum iPTH. Compliant patients in the NAMR group had a more pronounced and sustained reduction in serum phosphate than non-compliant patients. NAMR treatment was associated with a significantly increased risk of thrombocytopenia, pruritus, anaemia, and diarrhoea. Herpes zoster occurred exclusively in patients randomised to NAMR.

CONCLUSIONS

NAMR combined with phosphate binders significantly reduced serum phosphate over the first 24 weeks of treatment, but the treatment effect was not maintained up to W52. Non-compliance may have contributed to reduced long-term efficacy. Several newly identified safety signals warrant further evaluation.

Effects of pharmacological inhibition of the sodium-dependent phosphate cotransporter 2b (NPT2b) on intestinal phosphate absorption in mouse and rat models

An excess phosphate burden in renal disease has pathological consequences for bone, kidney, and heart. Therapies to decrease intestinal phosphate absorption have been used to address the problem, but with limited success. Here, we describe the in vivo effects of a novel potent inhibitor of the intestinal sodium-dependent phosphate cotransporter NPT2b, LY3358966. Following treatment with LY3358966, phosphate uptake into plasma 15 min following an oral dose of radiolabeled phosphate was decreased 74% and 22% in mice and rats, respectively, indicating NPT2b plays a much more dominant role in mice than rats. Following the treatment with LY3358966 and radiolabeled phosphate, mouse feces were collected for 48 h to determine the ability of LY3358966 to inhibit phosphate absorption. Compared to vehicle-treated animals, there was a significant increase in radiolabeled phosphate recovered in feces (8.6% of the dose, p < .0001). Similar studies performed in rats also increased phosphate recovered in feces (5.3% of the dose, p < .05). When used in combination with the phosphate binder sevelamer in rats, there was a further small, but not significant, increase in fecal phosphate. In conclusion, LY3358966 revealed a more prominent role for NPT2b on acute intestinal phosphate uptake into plasma in mice than rats. However, the modest effects on total intestinal phosphate absorption observed in mice and rats with LY3359866 when used alone or in combination with sevelamer highlights the challenge to identify new more effective therapeutic targets and/or drug combinations to treat the phosphate burden in patients with renal disease.

Nicotinamide and acute kidney injury

In a recent issue of ckj, Piedrafita et al. reported that urine tryptophan and kynurenine are reduced in cardiac bypass surgery patients that develop acute kidney injury (AKI), suggesting reduced activity of the kynurenine pathway of nicotinamide (NAM) adenine dinucleotide (NAD+) synthesis from tryptophan. However, NAM supplementation aiming at repleting NAD+ did not replete kidney NAD+ and did not improve glomerular filtration or reduce histological injury in ischaemic-reperfusion kidney injury in mice. The lack of improvement of kidney injury is partially at odds with prior reports that did not study kidney NAD+, glomerular filtration or histology in NAM-treated wild-type mice with AKI. We now present an overview of research on therapy with vitamin B3 vitamers and derivate molecules {niacin, Nicotinamide [NAM; niacinamide], NAM riboside [Nicotinamide riboside (NR)], Reduced nicotinamide riboside [NRH] and NAM mononucleotide} in kidney injury, including an overview of ongoing clinical trials, and discuss the potential explanations for diverging reports on the impact of these therapeutic approaches on pre-clinical acute and chronic kidney disease.