Pharmacological interactions of phosphate binders

Recommendations of the Spanish Society of Nephrology for the management of mineral and bone metabolism disorders in patients with chronic kidney disease: 2021 (SEN-MM)

As in 2011, when the Spanish Society of Nephrology (SEN) published the Spanish adaptation to the Kidney Disease: Improving Global Outcomes (KDIGO) universal Guideline on Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD), this document contains an update and an adaptation of the 2017 KDIGO guidelines to our setting. In this field, as in many other areas of nephrology, it has been impossible to irrefutably answer many questions, which remain pending. However, there is no doubt that the close relationship between the CKD-MBD/cardiovascular disease/morbidity and mortality complex and new randomised clinical trials in some areas and the development of new drugs have yielded significant advances in this field and created the need for this update. We would therefore highlight the slight divergences that we propose in the ideal objectives for biochemical abnormalities in the CKD-MBD complex compared to the KDIGO suggestions (for example, in relation to parathyroid hormone or phosphate), the role of native vitamin D and analogues in the control of secondary hyperparathyroidism and the contribution of new phosphate binders and calcimimetics. Attention should also be drawn to the adoption of important new developments in the diagnosis of bone abnormalities in patients with kidney disease and to the need to be more proactive in treating them. In any event, the current speed at which innovations are taking place, while perhaps slower than we might like, globally drives the need for more frequent updates (for example, through Nefrología al día).

New Directions in Phosphorus Management in Dialysis

Current phosphate management strategies in end-stage renal disease (dietary phosphate restriction, dialysis, and phosphate binders) are inadequate to maintain target phosphate levels in most patients. Dietary phosphate restriction is challenging due to "hidden phosphates" in processed foods, and dialysis and phosphate binders are insufficient to match average dietary phosphate intake. As phosphate binders must be taken with each meal, patients need to ingest many, large pills several times a day, negatively impacting quality of life. Recent advances in our understanding of phosphate absorption pathways have led to the development of new nonbinder therapies that block phosphate absorption. This review describes the limitations of current phosphate management strategies and discusses new therapies in development that inhibit phosphate absorption pathways. These new therapies present an opportunity to rethink phosphate management, potentially by prescribing phosphate absorption inhibitors as a primary therapy and adding phosphate binders if needed.

Safety and effectiveness of sucroferric oxyhydroxide in Spanish patients on dialysis: sub-analysis of the VERIFIE study

BACKGROUND AND AIMS

In this study, we show the results of the subset of Spanish patients of the VERIFIE study, the first post-marketing study assessing the long-term safety and effectiveness of sucroferric oxyhydroxide (SFOH) in patients with hyperphosphatemia undergoing dialysis during clinical practice.

PATIENTS AND METHODS

Patients undergoing hemodialysis and peritoneal dialysis with indication of SFOH treatment were included. Follow-up duration was 12-36 months after SFOH initiation. Primary safety variables were the incidence of adverse drug reactions (ADRs), medical events of special interest (MESIs), and variations in iron-related parameters. SFOH effectiveness was evaluated by the change in serum phosphorus levels.

RESULTS

A total of 286 patients were recruited and data from 282 were analyzed. Among those 282 patients, 161 (57.1%) withdrew the study prematurely and 52.5% received concomitant treatment with other phosphate binders. ADRs were observed in 35.1% of patients, the most common of which were gastrointestinal disorders (77.1%) and mild/moderate in severity (83.7%). MESIs were reported in 14.2% of patients, and 93.7% were mild/moderate. An increase in ferritin (386.66ng/mL vs 447.55ng/mL; p=0.0013) and transferrin saturation (28.07% vs 30.34%; p=0.043) was observed from baseline to the last visit (p=0.0013). Serum phosphorus levels progressively decreased from 5.69mg/dL at baseline to 4.84mg/dL at the last visit (p<0.0001), increasing by 32.2% the proportion of patients who achieved serum phosphorus levels ≤5.5mg/dL, with a mean daily SFOH dose of 1.98 pills/day.

CONCLUSIONS

SFOH showed a favorable effectiveness profile, a similar safety profile to that observed in the international study with most adverse events of mild/moderate severity, and a low daily pill burden in Spanish patients in dialysis.

Exploring co-dispensed drug use in patients on sevelamer or polystyrene sulfonate to identify potential novel binding interactions: a cross sectional in silico study : Potential novel binding interactions with resins

Background Sevelamer and polystyrene sulfonate are used for treating hyperphosphatemia and hyperkalaemia in chronic kidney disease patients. Because of their binding properties, these resins potentially bind other drugs in the gastrointestinal tract, thereby decreasing their bioavailability and clinical effectiveness. Aim The aim of this study was to explore co-dispensed drug use in patients on sevelamer or polystyrene sulfonate to identify potential novel binding interactions. Method In this in silico study, the 100 drugs most frequently co-dispensed with sevelamer/polystyrene sulfonate in the period 2000-2018 were extracted from the University Groningen IADB.nl database. Drugs dispensed to < 5% of patients, drugs not orally administered, drugs administered once daily before bedtime and drugs for which information on binding interactions with sevelamer or polystyrene was already available were excluded. The likelihood of an interaction (yes or no) of the included drugs was assessed based on pKa- and Log P values. For sevelamer, drugs with a pKa (acid) between 1.5 and 7.4 and or a Log P value > 2.0 were identified as potential interacting drug. For polystyrene sulfonate, drugs with a pKa (base) > 1.5 were identified as potential interacting drug. Results Of the top 100 drugs most frequently co-dispensed with sevelamer/polystyrene sulfonate, 22 and 27 potentially clinically relevant new interacting drugs were identified for sevelamer and polystyrene sulfonate respectively. Conclusion Several potentially relevant novel binding interactions for sevelamer and polystyrene sulfonate were identified based on dispensing data and assessment of chemical properties for which further interaction research is warranted.

A safety evaluation of sucroferric oxyhydroxide for the treatment of hyperphosphatemia

INTRODUCTION

Hyperphosphatemia is a common complication as chronic kidney disease (CKD) progresses and most patients undergoing dialysis are prescribed oral phosphate binder therapy to control serum phosphate concentrations. Sucroferric oxyhydroxide is an iron-based phosphate binder approved for the treatment of hyperphosphatemia in CKD patients on dialysis.

AREAS COVERED

This article reviews key safety and effectiveness data for sucroferric oxyhydroxide from both prospective clinical trials and real-world observational studies.

EXPERT OPINION

Sucroferric oxyhydroxide potently binds dietary phosphate in the gastrointestinal (GI) tract, resulting in effective reduction of serum phosphate concentrations with a relatively low daily pill burden. Data from clinical trials and real-world observational studies show sucroferric oxyhydroxide has a favorable safety and tolerability profile. The most frequent side effects observed with sucroferric oxyhydroxide are GI-related, mainly discolored (black) stools and mild or moderate transient diarrhea, both of which are manageable. There is minimal systemic iron absorption from sucroferric oxyhydroxide, and therefore the drug is associated with a low risk of iron accumulation. Sucroferric oxyhydroxide also displays low potential for drug-drug interactions with other commonly prescribed oral medications. Overall, sucroferric oxyhydroxide offers an effective and well-tolerated treatment option for the management of hyperphosphatemia.

Small Intestinal Phosphate Absorption: Novel Therapeutic Implications

BACKGROUND

Chronic kidney disease (CKD) affects approximately 15% of adults in the USA. As CKD progresses, urinary phosphate excretion decreases and results in phosphate retention and, eventually, hyperphosphatemia. As hyperphosphatemia is associated with numerous adverse outcomes, including increased cardiovascular mortality, reduction in phosphorus concentrations is a guideline-recommended, established clinical practice. Dietary phosphate restriction, dialysis, and phosphate binders are currently the only options for phosphate management. However, many patients with hyperphosphatemia have phosphorus concentrations >5.5 mg/dL, despite treatment.

SUMMARY

This review pre-sents recent advances in the understanding of intestinal phosphate absorption and therapeutic implications. Dietary phosphate is absorbed in the intestine through two distinct pathways, paracellular absorption and transcellular transport. Recent evidence indicates that the paracellular route accounts for 65-80% of total phosphate absorbed. Thus, the paracellular pathway is the dominant mechanism of phosphate absorption. Tenapanor is a first-in-class, non-phosphate binder that inhibits the sodium-hydrogen exchanger 3 or solute carrier family 9 member 3 (SLC9A3) encoded by the SLC9A3 gene, and blocks paracellular phosphate absorption. Key Messages: Targeted inhibition of sodium-hydrogen exchanger 3 effectively reduces paracellular permeability of phosphate. Novel therapies that target the paracellular pathway may improve phosphate control in chronic kidney disease.

Binding interactions with sevelamer and polystyrene sulfonate in vitro

This study explored the binding of 28 drugs, which were selected based on frequency of concomitant use and chemical properties, to sevelamer and polystyrene sulfonate in vitro. The relative binding was determined by dissolving the investigated drugs alone (=control), together with 800 mg of sevelamer and 15 g of polystyrene sulfonate at different pH levels (1.5, 5.5, and 7.4), respectively. After incubation at 37℃ and shaking for 60 min, the solutions were diluted and centrifuged, and the drug concentrations were quantified with validated analytical assays. The binding assays were performed in threefold. The mean relative binding (MRB) at each pH level was calculated, with a MRB >20% for at least one pH level to be considered as relevant binding. Fourteen and 23 potentially new binding interactions were identified with sevelamer and polystyrene sulfonate, respectively. These potentially new binding interactions have to be studied in vivo to assess their clinical relevance.

Phosphate Balance and CKD-Mineral Bone Disease

Chronic kidney disease–mineral bone disorder (CKD-MBD) is a common comorbidity in patients with CKD. Characterized by laboratory abnormalities, bone abnormality, and vascular calcification, CKD-MBD encompasses a group of mineral and hormone disturbances that are strongly associated with increased cardiovascular (CV) morbidity and mortality. Abnormal serum phosphate concentrations are an independent risk factor for CV morbidity and mortality, and overall mortality. Phosphate retention plays a central role in initiating and driving many other disturbances in CKD-MBD (e.g., increased parathyroid hormone and fibroblast growth factor 23 concentrations, hypocalcemia, low vitamin D) that are also linked to increased CV risk. Thus, effective phosphate control is a logical therapeutic target for CKD-MBD treatment. Current phosphate management strategies (dietary restrictions, dialysis, phosphate binders) are insufficient to consistently achieve and maintain target phosphate concentrations in patients on dialysis. Phosphate binders reduce available phosphate for intestinal absorption but do not impair the dominant phosphate absorption pathway. Novel therapies that consider new mechanistic understandings of intestinal phosphate absorption are needed. One such therapy is tenapanor, a targeted sodium-hydrogen exchanger isoform 3 inhibitor that has been shown to reduce serum phosphate concentrations in multiple clinical trials. Tenapanor has a novel mechanism of action that reduces intestinal phosphate absorption in the primary paracellular phosphate absorption pathway.

Phosphate, Microbiota and CKD

Phosphate is a key uremic toxin associated with adverse outcomes. As chronic kidney disease (CKD) progresses, the kidney capacity to excrete excess dietary phosphate decreases, triggering compensatory endocrine responses that drive CKD-mineral and bone disorder (CKD-MBD). Eventually, hyperphosphatemia develops, and low phosphate diet and phosphate binders are prescribed. Recent data have identified a potential role of the gut microbiota in mineral bone disorders. Thus, parathyroid hormone (PTH) only caused bone loss in mice whose microbiota was enriched in the Th17 cell-inducing taxa segmented filamentous bacteria. Furthermore, the microbiota was required for PTH to stimulate bone formation and increase bone mass, and this was dependent on bacterial production of the short-chain fatty acid butyrate. We review current knowledge on the relationship between phosphate, microbiota and CKD-MBD. Topics include microbial bioactive compounds of special interest in CKD, the impact of dietary phosphate and phosphate binders on the gut microbiota, the modulation of CKD-MBD by the microbiota and the potential therapeutic use of microbiota to treat CKD-MBD through the clinical translation of concepts from other fields of science such as the optimization of phosphorus utilization and the use of phosphate-accumulating organisms.