VALOR-CKD: A Multicenter, Randomized, Double-Blind Placebo-Controlled Trial Evaluating Veverimer in Slowing Progression of CKD in Patients with Metabolic Acidosis

SIGNIFICANCE STATEMENT

Metabolic acidosis is a common complication of CKD and is associated with more rapid decline of kidney function, but well-powered controlled randomized trials testing the effect of treating metabolic acidosis on slowing CKD progression have not been conducted. The VALOR-CKD study randomized 1480 individuals with CKD and metabolic acidosis, across 320 sites to placebo or veverimer (a novel hydrochloric acid binder). The findings did not demonstrate the efficacy of veverimer in slowing CKD progression, but the difference in serum bicarbonate between placebo and drug arms was only approximately 1 mEq/L. Veverimer was safe and well tolerated.

BACKGROUND

Metabolic acidosis is common in CKD, but whether its treatment slows CKD progression is unknown. Veverimer, a novel hydrochloric acid binder that removes acid from the gastrointestinal tract, leads to an increase in serum bicarbonate.

METHODS

In a phase 3, double-blind, placebo-controlled trial, patients with CKD (eGFR of 20-40 ml/min per 1.73 m 2 ) and metabolic acidosis (serum bicarbonate of 12-20 mEq/L) from 35 countries were randomized to veverimer or placebo. The primary outcome was the composite end point of CKD progression, defined as the development of ESKD (kidney transplantation or maintenance dialysis), a sustained decline in eGFR of ≥40% from baseline, or death due to kidney failure.

RESULTS

The mean (±SD) baseline eGFR was 29.2±6.3 ml/min per 1.73 m 2 , and serum bicarbonate was 17.5±1.4 mEq/L; this increased to 23.4±2.0 mEq/L after the active treatment run-in. After randomized withdrawal, the mean serum bicarbonate was 22.0±3.0 mEq/L and 20.9±3.3 mEq/L in the veverimer and placebo groups at month 3, and this approximately 1 mEq/L difference remained stable for the first 24 months. A primary end point event occurred in 149/741 and 148/739 patients in the veverimer and placebo groups, respectively (hazard ratio, 0.99; 95% confidence interval, 0.8 to 1.2; P = 0.90). Serious and overall adverse event incidence did not differ between the groups.

CONCLUSIONS

Among patients with CKD and metabolic acidosis, treatment with veverimer did not slow CKD progression. The lower than expected bicarbonate separation may have hindered the ability to test the hypothesis.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

VALOR-CKD, NCT03710291 .

Magnesium decreases urine supersaturation but not calcium oxalate stone formation in genetic hypercalciuric stone-forming rats

BACKGROUND/AIMS

Hypercalciuria is the most common identifiable risk factor predisposing to CaOx stone formation. Increased oral magnesium intake may lead to decreased CaOx stone formation by binding intestinal Ox leading to decreased absorption and/or binding urinary Ox to decrease urinary supersaturation. This study assessed the effect of oral magnesium on 24-hour urine ion excretion, supersaturation, and kidney stone formation in a genetic hypercalciuric stone-forming (GHS) rat model of human idiopathic hypercalciuria.

METHODS

When fed the oxalate precursor, hydroxyproline, every GHS rat develops CaOx stones. The GHS rats were fed a normal calcium and phosphorus diet with hydroxyproline to induce CaOx , were divided into three groups of ten rats per group: control diet with 4.0 g/kg MgO, low MgO diet (0.5 g/kg), and high MgO diet (8 g/kg). At 6 weeks, twenty-four-hour urines were collected, and urine chemistry and supersaturation were determined. Stone formation was quantified.

RESULTS

The GHS rats fed the low and high Mg diets had a significant reduction and increase, respectively, in urinary Mg compared to those fed the control diet. Dietary Mg did not alter urine Ca excretion while the low Mg diet led to a significant fall in urinary Ox. Urine supersaturation with respect to CaOx was significantly increased with low Mg, whereas urine supersaturation was significantly decreased with high Mg. There was no effect of dietary Mg on stone formation within 6 weeks of treatment.

CONCLUSION

Dietary magnesium decreases urine supersaturation but not CaOx stone formation in GHS rats.

Association of serum bicarbonate with the development of kidney stones in patients with chronic kidney disease: a retrospective cohort study

BACKGROUND

Epidemiological studies demonstrate an association between kidney stones and risk of chronic kidney disease (CKD) and CKD progression. Metabolic acidosis, as a consequence of CKD, results in a reduced urine pH which promotes the formation of some types of kidney stones and inhibits the formation of others. While metabolic acidosis is a risk factor for CKD progression, the association of serum bicarbonate with risk of incident kidney stones is not well understood.

METHODS

We used an Integrated Claims-Clinical dataset of US patients to generate a cohort of patients with non-dialysis-dependent CKD with two serum bicarbonate values of 12 to <22 mmol/L (metabolic acidosis) or 22 to <30 mmol/L (normal serum bicarbonate). Primary exposure variables were baseline serum bicarbonate and change in serum bicarbonate over time. Cox proportional hazards models evaluated time to first occurrence of kidney stones during a median 3.2-year follow-up.

RESULTS

A total of 142 884 patients qualified for the study cohort. Patients with metabolic acidosis experienced post-index date kidney stones at greater frequency than patients with normal serum bicarbonate at the index date (12.0% vs 9.5%, P < .0001). Both lower baseline serum bicarbonate [hazard ratio (HR) 1.047; 95% confidence interval (CI) 1.036-1.057] and decreasing serum bicarbonate over time (HR 1.034; 95% CI 1.026-1.043) were associated with increased risk of kidney stone development.

CONCLUSIONS

Metabolic acidosis was associated with a higher incidence of kidney stones and shorter time to incident stone formation in patients with CKD. Future studies may investigate the role of correcting metabolic acidosis to prevent stone formation.

Patiromer Treatment in Patients With CKD, Hyperkalemia, and Hyperphosphatemia: A Post Hoc Analysis of 3 Clinical Trials

RATIONALE & OBJECTIVE

Patients with chronic kidney disease (CKD), hyperkalemia (serum potassium [sK+]>5.0 mEq/L), and hyperphosphatemia experience poor clinical outcomes. Patiromer, a potassium binder that uses calcium as the exchange ion, may also reduce serum phosphorus (sP). We characterized the effect of patiromer on sP in patients with CKD, hyperkalemia, and hyperphosphatemia.

STUDY DESIGN

A post hoc pooled analysis of individual-level data from the AMETHYST-DN, OPAL-HK, and TOURMALINE trials of patiromer.

SETTING & PARTICIPANTS

Patients with CKD and hyperkalemia.

EXPOSURE

Patients treated with patiromer (8.4-33.6 g/day).

OUTCOME

Mean changes from baseline in sP, sK+, serum calcium (sCa2+), and serum magnesium (sMg2+) after 2 and 4 weeks of treatment.

ANALYTICAL APPROACH

Descriptive statistics to summarize pooled data on the study outcomes from the 3 studies.

RESULTS

We included 578 patients in the analysis. Of these participants, 86 patients (14.9%) had baseline hyperphosphatemia of whom 75.6% (65 of 86) had CKD stage 4/5 and 31.1% (153 of 492) with sP≤4.5mg/dL had CKD stage 4/5. Among the patients with elevated sP and sK+at baseline, the mean±SD reduction in sP and sK+after 4 weeks of patiromer treatment was-0.62±1.09mg/dL and-0.71± 0.51 mEq/L, respectively. Additionally, the mean±SD reduction in sMg2+in these patients was -0.25±0.23mg/dL while sCa2+remained unchanged. Both sMg2+and sCa2+remained within the normal range. Patiromer was generally well tolerated, and no serious adverse events were considered related to patiromer.

LIMITATIONS

These were post hoc analyses, no placebo comparison was performed due to the design of the original studies, and the follow-up period was limited to 4 weeks.

CONCLUSIONS

Reductions in sP and sK+to the normal range were observed after 2 weeks of patiromer treatment, and the reduction was sustained during 4 weeks of treatment among patients with non-dialysis-dependent CKD, hyperkalemia, and hyperphosphatemia. Future controlled trials are needed to establish if patiromer is useful to reduce both sK+and sP in hyperkalemic patients with CKD and hyperphosphatemia.

Design and Population of the VALOR-CKD Study: A Multicenter, Randomized, Double-Blind Placebo-Controlled Trial Evaluating the Efficacy and Safety of Veverimer in Slowing Progression of Chronic Kidney Disease in Patients with Metabolic Acidosis

Background

Whether treating metabolic acidosis slows progression of chronic kidney disease (CKD) has not been established. Veverimer is a novel hydrochloric acid binder that removes acid from the gastrointestinal tract leading to an increase in serum bicarbonate; it is being developed to treat metabolic acidosis with the goal of slowing progression of CKD.

Methods

The VALOR-CKD trial is an international, randomized, multicenter, double-blind, placebo-controlled study designed to evaluate the effect of once-daily veverimer on kidney disease progression in patients with metabolic acidosis and CKD. Eligibility criteria include a serum bicarbonate in the range of 12-20 mmol/L and an estimated glomerular filtration rate (eGFR) of 20-40 mL/min/1.73 m2. The primary outcome is kidney disease progression defined as the development of end-stage kidney disease, a sustained decline in eGFR of &gt; 40% from baseline, or death due to kidney failure. Key secondary endpoints include effects on physical function.

Results

Between December 2018 and December 2021, 1480 participants were randomized. The mean age at baseline was 65.1 years and 42% of the patients were female. The mean baseline eGFR was 29.1 mL/min/1.73 m2 and mean serum bicarbonate was 17.5 mmol/L. The median urine albumin-to-creatinine ratio at screening was 201 mg/g and the median 5-year predicted risk of kidney failure was 24%. Diabetes and hypertension were present in 56% and 98% of participants, respectively.

Conclusions

VALOR-CKD has recruited a large population of people with metabolic acidosis at high risk for CKD progression to determine the effects of veverimer on the risk of progressive loss of kidney function.

Primary Medical Care Integrated with Healthy Eating and Healthy Moving is Essential to Reduce Chronic Kidney Disease Progression

Increasing adverse outcomes in patients with chronic kidney disease reflect growth of patients with early-stage chronic kidney disease and their increasing per population rates of these outcomes. Progression of chronic kidney disease, more than current level of kidney function, is the primary driver of adverse chronic kidney disease-related outcomes. Racial/ethnic minorities progress faster to end-stage kidney disease with greater risk for adverse outcomes. Diabetes and hypertension cause two-thirds of end-stage kidney disease, for which primary medical care integrated with healthy eating and increased physical activity (healthy moving) slows chronic kidney disease progression. Patients with early-stage chronic kidney disease are appropriately managed by primary care practices but most lack infrastructure to facilitate this integration that reduces adverse chronic kidney disease-related outcomes. Individuals of low socioeconomic status are at greater chronic kidney disease risk, and flexible regulatory options in Medicaid can fund infrastructure to facilitate healthy eating and healthy moving integration with primary medical care. This integration promises to reduce chronic kidney disease-related adverse outcomes, disproportionately in racial/ethnic minorities, and thereby reduce chronic kidney disease-related health disparities.

Modeling osteoporosis to design and optimize pharmacological therapies comprising multiple drug types

For the treatment of postmenopausal osteoporosis, several drug classes with different mechanisms of action are available. Since only a limited set of dosing regimens and drug combinations can be tested in clinical trials, it is currently unclear whether common medication strategies achieve optimal bone mineral density gains or are outperformed by alternative dosing schemes and combination therapies that have not been explored so far. Here, we develop a mathematical framework of drug interventions for postmenopausal osteoporosis that unifies fundamental mechanisms of bone remodeling and the mechanisms of action of four drug classes: bisphosphonates, parathyroid hormone analogs, sclerostin inhibitors, and receptor activator of NF-κB ligand inhibitors. Using data from several clinical trials, we calibrate and validate the model, demonstrating its predictive capacity for complex medication scenarios, including sequential and parallel drug combinations. Via simulations, we reveal that there is a large potential to improve gains in bone mineral density by exploiting synergistic interactions between different drug classes, without increasing the total amount of drug administered.

Effects of veverimer on serum bicarbonate and physical function in women with chronic kidney disease and metabolic acidosis: a subgroup analysis from a randomised, controlled trial

BACKGROUND

Globally, the prevalence of chronic kidney disease (CKD) is higher in women than in men; however, women have been historically under-represented in nephrology clinical trials. Metabolic acidosis increases risk of progressive loss of kidney function, causes bone demineralization and muscle protein catabolism, and may be more consequential in women given their lower bone and muscle mass. Veverimer, an investigational, non-absorbed polymer that binds and removes gastrointestinal hydrochloric acid, is being developed as treatment for metabolic acidosis.

METHODS

This was a Phase 3, multicenter, randomised, blinded, placebo-controlled trial in 196 patients with CKD (eGFR: 20-40 mL/min/1.73 m2) and metabolic acidosis who were treated for up to 1 year with veverimer or placebo. We present the findings from a pre-specified subgroup analysis evaluating the effects of veverimer on metabolic acidosis and physical function among women (N = 77) enrolled in this trial.

RESULTS

At week 52, women treated with veverimer had a greater increase in mean (± standard error) serum bicarbonate than the placebo group (5.4 [0.5] vs. 2.2 [0.6] mmol/L; P < 0.0001). Physical Function reported by patients on the Kidney Disease and Quality of Life - Physical Function Domain, a measure that includes items related to walking, stair climbing, carrying groceries and other activities improved significantly in women randomized to veverimer vs placebo (+ 13.2 vs. -5.2, respectively, P < 0.0031). Objectively measured performance time on the repeated chair stand test also improved significantly in the veverimer group vs. placebo (P = 0.0002).

CONCLUSIONS

Veverimer was effective in treating metabolic acidosis in women with CKD, and significantly improved how they felt and functioned.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03390842 . Registered on January 4, 2018.

Personalized Prediction of Short- and Long-Term PTH Changes in Maintenance Hemodialysis Patients

Background: Personalized management of secondary hyperparathyroidism is a critical part of hemodialysis patient care. We used a mathematical model of parathyroid gland (PTG) biology to predict (1) short-term peridialytic intact PTH (iPTH) changes in response to diffusive calcium (Ca) fluxes and (2) to predict long-term iPTH levels.

Methods: We dialyzed 26 maintenance hemodialysis patients on a single occasion with a dialysate Ca concentration of 1.75 mmol/l to attain a positive dialysate-to-blood ionized Ca (iCa) gradient and thus diffusive Ca loading. Intradialytic iCa kinetics, peridialytic iPTH change, and dialysate-sided iCa mass balance (iCaMB) were assessed. Patient-specific PTG model parameters were estimated using clinical, medication, and laboratory data. We then used the personalized PTG model to predict peridialytic and long-term (6-months) iPTH levels.

Results: At dialysis start, the median dialysate-to-blood iCa gradient was 0.3 mmol/l (IQR 0.11). The intradialytic iCa gain was 488 mg (IQR 268). Median iPTH decrease was 75% (IQR 15) from pre-dialysis 277 to post-dialysis 51 pg/ml. Neither iCa gradient nor iCaMB were significantly associated with peridialytic iPTH changes. The personalized PTG model accurately predicted both short-term, treatment-level peridialytic iPTH changes (r = 0.984, p < 0.001, n = 26) and patient-level 6-months iPTH levels (r = 0.848, p < 0.001, n = 13).

Conclusions: This is the first report showing that both short-term and long-term iPTH dynamics can be predicted using a personalized mathematical model of PTG biology. Prospective studies are warranted to explore further model applications, such as patient-level prediction of iPTH response to PTH-lowering treatment.

Metabolic Acidosis Regulates RGS16 and G-protein Signaling in Osteoblasts

Chronic metabolic acidosis stimulates cell-mediated net calcium efflux from bone mediated by increased osteoblastic cyclooxygenase 2 (COX2), leading to prostaglandin E2-induced stimulation of RANKL-induced osteoclastic bone resorption. The osteoblastic H⁺-sensing G-protein coupled receptor (GPCR), OGR1, is activated by acidosis and leads to increased bne resorption. As regulators of G protein signaling (RGS) proteins limit GPCR signaling, we tested whether RGS proteins themselves are regulated by metabolic acidosis. Primary osteoblasts were isolated from neonatal mouse calvariae and incubated in physiological neutral (NTL) or acidic (MET) medium. Cells were collected and RNA extracted for real time PCR analysis with mRNA levels normalized to RPL13a. RGS1, RGS2, RGS3, RGS4, RGS10, RGS11 or RGS18mRNA did not differ between MET and NTL; however by 30' MET decreased RGS16 which persisted for 60' and 3h. Incubation of osteoblasts with the OGR1 inhibitor CuCl₂ inhibited the MET induced increase in RGS16 mRNA. Gallein, a specific inhibitor of Gβγ signaling, was used to determine if downstream signaling by the βγ subunit was critical for the response to acidosis. Gallein decreased net Ca efflux from calvariae and COX2 and RANKL gene expression from isolated osteoblasts. These results indicate that regulation of RGS16 plays an important role in modulating the response of the osteoblastic GPCR, OGR1, to metabolic acidosis and subsequent stimulation of osteoclastic bone resorption.

Effects of Myo-inositol Hexaphosphate (SNF472) on Bone Mineral Density in Patients Receiving Hemodialysis: An Analysis of the Randomized, Placebo-Controlled CaLIPSO Study

BACKGROUND AND OBJECTIVES

In the CaLIPSO study, intravenous administration of SNF472 (300 or 600 mg) during hemodialysis significantly attenuated progression of coronary artery and aortic valve calcification. SNF472 selectively inhibits formation of hydroxyapatite, the final step in cardiovascular calcification. Because bone mineral is predominantly hydroxyapatite, we assessed changes in bone mineral density in CaLIPSO.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with coronary artery calcification at screening (Agatston score of 100-3500 U) were randomized 1:1:1 to receive placebo, 300 mg SNF472, or 600 mg SNF472 as an intravenous infusion during hemodialysis three times weekly for 52 weeks. Dual-energy x-ray absorptiometry (DXA) scans were obtained at baseline (screening) and end of treatment, and between-group changes from baseline were compared using analysis of covariance.

RESULTS

Among 274 randomized patients, 202 had evaluable DXA scans at baseline and postrandomization (the DXA-modified intention-to-treat population). Mean (95% confidence interval) changes in total-hip bone mineral density from baseline to week 52 were -1.5% (-2.7% to -0.3%), -1.5% (-2.7% to -0.4%), and -2.5% (-3.8% to -1.2%) in the placebo, 300 mg SNF472, and 600 mg SNF472 groups, respectively. Mean (95% confidence interval) changes in femoral-neck bone mineral density from baseline to week 52 were -0.3% (-1.6% to 1.0%), -1.0% (-2.3% to 0.2%), and -2.6% (-4.0% to -1.3%), respectively. Regression analyses showed no correlation between change in coronary artery calcium volume and change in bone mineral density at either location. Changes in serum alkaline phosphatase, calcium, magnesium, phosphate, and intact parathyroid hormone levels were similar across treatment groups. Clinical fracture events were reported for four of 90, three of 92, and six of 91 patients in the placebo, 300 mg SNF472, and 600 mg SNF472 groups, respectively.

CONCLUSIONS

Bone mineral density decreased modestly in all groups over 1 year. In the 600 mg SNF472 group, the reduction appeared more pronounced. Reported fractures were infrequent in all groups.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Effect of SNF472 on Progression of Cardiovascular Calcification in End-Stage-Renal-Disease (ESRD) Patients on Hemodialysis (HD), NCT02966028.

Chlorthalidone with potassium citrate decreases calcium oxalate stones and increases bone quality in genetic hypercalciuric stone-forming rats

To study human idiopathic hypercalciuria we developed an animal model, genetic hypercalciuric stone-forming rats, whose pathophysiology parallels that of human idiopathic hypercalciuria. Fed the oxalate precursor, hydroxyproline, every rat in this model develops calcium oxalate stones. Using this rat model, we tested whether chlorthalidone and potassium citrate combined would reduce calcium oxalate stone formation and improve bone quality more than either agent alone. These rats (113 generation) were fed a normal calcium and phosphorus diet with hydroxyproline and divided into four groups: diets plus potassium chloride as control, potassium citrate, chlorthalidone plus potassium chloride, or potassium citrate plus chlorthalidone. Urine was collected at six, 12, and 18 weeks and kidney stone formation and bone parameters were determined. Compared to potassium chloride, potassium citrate reduced urinary calcium, chlorthalidone reduced it further and potassium citrate plus chlorthalidone even further. Potassium citrate plus chlorthalidone decreased urine oxalate compared to all other groups. There were no significant differences in calcium oxalate supersaturation in any group. Neither potassium citrate nor chlorthalidone altered stone formation. However, potassium citrate plus chlorthalidone significantly reduced stone formation. Vertebral trabecular bone increased with chlorthalidone and potassium citrate plus chlorthalidone. Cortical bone area increased with chlorthalidone but not potassium citrate or potassium citrate plus chlorthalidone. Mechanical properties of trabecular bone improved with chlorthalidone, but not with potassium citrate plus chlorthalidone. Thus in genetic hypercalciuric stone-forming rats fed a diet resulting in calcium oxalate stone formation, potassium citrate plus chlorthalidone prevented stone formation better than either agent alone. Chlorthalidone alone improved bone quality, but adding potassium citrate provided no additional benefit.

One-year safety and efficacy of intravenous etelcalcetide in patients on hemodialysis with secondary hyperparathyroidism

BACKGROUND

Secondary hyperparathyroidism (sHPT), a common complication of chronic kidney disease, is characterized by elevated serum parathyroid hormone (PTH). Etelcalcetide is an intravenous calcimimetic that increases sensitivity of the calcium-sensing receptor to calcium and decreases PTH secretion. This open-label extension (OLE) trial evaluated the long-term effects of etelcalcetide for sHPT treatment in patients receiving hemodialysis.

METHODS

This 52-week, multicenter, single-arm OLE enrolled patients from three parent trials: two randomized, double-blind, placebo-controlled trials and one open-label, single-arm, 'switch' study from cinacalcet to etelcalcetide. The primary endpoint was to investigate the nature, frequency, severity and relation to treatment of all adverse events (AEs) reported throughout the trial. Secondary endpoints included the proportion of patients with >30% reduction from baseline in PTH and the percentage change from baseline in PTH, albumin-corrected calcium (Ca), phosphate (P) and the calcium-phosphate product (Ca × P).ClinicalTrials.gov identifier: NCT01785875; Amgen study: 20120231.

RESULTS

Overall, 89.8% of the patients experienced one or more treatment-emergent AE. The most common were decreased blood Ca (43.3%), diarrhea (10.8%), vomiting (10.4%) and nausea (9.6%); symptomatic hypocalcemia occurred in 3.7% of the patients. Approximately 68% of patients achieved >30% reduction in PTH, and ∼56% achieved PTH ≤300 pg/mL. Mean percent changes from baseline ranged from -25.4% to -26.1% for PTH, -8.3% to -9.1% for Ca, -3.6% to -4.1% for P and -12.0% to -12.6% for Ca × P.

CONCLUSIONS

Etelcalcetide effectively lowered PTH and its effect was sustained, while no new safety concerns emerged over a 1-year treatment period.

Identification of Novel Biomarkers and Pathways for Coronary Artery Calcification in Nondiabetic Patients on Hemodialysis Using Metabolomic Profiling

BACKGROUND

A better understanding of the pathophysiology involving coronary artery calcification (CAC) in patients on hemodialysis (HD) will help to develop new therapies. We sought to identify the differences in metabolomics profiles between patients on HD with and without CAC.

METHODS

In this case-control study, nested within a cohort of 568 incident patients on HD, the cases were patients without diabetes with a CAC score >100 (n=51), and controls were patients without diabetes with a CAC score of zero (n=48). We measured 452 serum metabolites in each participant. Metabolites and pathway scores were compared using Mann-Whitney U tests, partial least squares-discriminant analyses, and pathway enrichment analyses.

RESULTS

Compared with controls, cases were older (64±13 versus 42±12 years) and were less likely to be Black (51% versus 94%). We identified three metabolites in bile-acid synthesis (chenodeoxycholic, deoxycholic, and glycolithocholic acids) and one pathway (arginine/proline metabolism). After adjusting for demographics, higher levels of chenodeoxycholic, deoxycholic, and glycolithocholic acids were associated with higher odds of having CAC; comparing the third with the first tertile of each bile acid, the OR was 6.34 (95% CI, 1.12 to 36.06), 6.73 (95% CI, 1.20 to 37.82), and 8.53 (95% CI, 1.50 to 48.49), respectively. These associations were no longer significant after further adjustment for coronary artery disease and medication use. Per 1 unit higher in the first principal component score, arginine/proline metabolism was associated with CAC after adjusting for demographics (OR, 1.83; 95% CI, 1.06 to 3.15), and the association remained significant with additional adjustments for statin use (OR, 1.84; 95% CI, 1.04 to 3.27).

CONCLUSIONS

Among patients on HD without diabetes mellitus, chenodeoxycholic, deoxycholic, and glycolithocholic acids may be potential biomarkers for CAC, and arginine/proline metabolism is a plausible mechanism to study for CAC. These findings need to be confirmed in future studies.

Effects of SNF472, a Novel Inhibitor of Hydroxyapatite Crystallization in Patients Receiving Hemodialysis - Subgroup Analyses of the CALIPSO Trial

INTRODUCTION

Coronary artery calcium (CAC) is highly prevalent and linked with poor outcomes in patients receiving maintenance hemodialysis, and its reduction may improve patient prognosis. SNF472, a selective inhibitor of hydroxyapatite crystallization, slows CAC progression in patients receiving maintenance hemodialysis. In this analysis, we assessed the efficacy of SNF472 in prespecified patient subgroups.

METHODS

In a randomized clinical trial SNF472 300 mg, SNF472 600 mg, or placebo were infused thrice weekly in 91, 92, and 91 patients receiving maintenance hemodialysis and with CAC at baseline, respectively. In prespecified subanalyses, the percent change in CAC volume score (CACvs) from baseline to week 52 in modified intention-to-treat (mITT) and per-protocol (PP) populations was calculated in the following subgroups: age, sex, diabetes mellitus, dialysis vintage, prior atherosclerotic cardiovascular disease, baseline use of non-calcium and calcium-based phosphate binders, calcimimetics, activated vitamin D, warfarin, and statins.

RESULTS

In the main trial, SNF472 significantly reduced CACvs progression compared with placebo (11% versus 20% mITT analyses; P = 0.016; 8% vs. 24% PP analyses; P < 0.001). Treatment differences for CACvs progression were similar across all subgroups, and all interaction P values were non-significant in mITT and PP analyses.

CONCLUSIONS

SNF472 treatment for 52 weeks reduced CACvs progression compared with placebo in a broad range of patients receiving maintenance hemodialysis. Future studies will determine the impact of SNF472 on cardiovascular events in this population.

Kidney stone formation and the gut microbiome are altered by antibiotics in genetic hypercalciuric stone-forming rats

Antibiotics can alter the gut microbiome (GMB), which may be associated with stone disease. We sought to determine the effect that antibiotics have on the GMB, urine ion excretion and stone formation in genetic hypercalciuric stone-forming (GHS) rats. 116th generation GHS rats were fed a fixed amount of a normal calcium (1.2%) and phosphate (0.65%) diet, and divided into three groups (n = 10): control (CTL) diet, or supplemented with ciprofloxacin (Cipro, 5 mg/day) or Bactrim (250 mg/day). Urine and fecal pellets were collected over 6, 12 and 18 weeks. Fecal DNA was amplified across the 16S rRNA V4 region. At 18 weeks, kidney stone formation was visualized by Faxitron and blindly assessed by three investigators. After 18 weeks, urine calcium and oxalate decreased with Bactrim compared to CTL and Cipro. Urine pH increased with Bactrim compared to CTL and Cipro. Urine citrate increased with Cipro compared to CTL and decreased by half with Bactrim. Calcification increased with Bactrim compared to CTL and Cipro. Increased microbial diversity correlated with decreased urinary oxalate in all animals (R = - 0.46, p = 0.006). A potential microbial network emerged as significantly associated with shifts in urinary pH. Bactrim and Cipro differentially altered the GMB of GHS rats. The Bactrim group experienced a decrease in urine calcium, increased CaP supersaturation and increased calcification. The GMB is likely a contributing factor to changes in urine chemistry, supersaturation and stone risk. Further investigation is required to fully understand the association between antibiotics, the GMB and kidney stone formation.

Deletion of the proton receptor OGR1 in mouse osteoclasts impairs metabolic acidosis-induced bone resorption

Metabolic acidosis induces osteoclastic bone resorption and inhibits osteoblastic bone formation. Previously we found that mice with a global deletion of the proton receptor OGR1 had increased bone density although both osteoblast and osteoclast activity were increased. To test whether direct effects on osteoclast OGR1 are critical for metabolic acidosis stimulated bone resorption, we generated knockout mice with an osteoclast-specific deletion of OGR1 (knockout mice). We studied bones from three-month old female mice and the differentiated osteoclasts derived from bone marrow of femurs from these knockout and wild type mice. MicroCT demonstrated increased density in tibiae and femurs but not in vertebrae of the knockout mice. Tartrate resistant acid phosphatase staining of tibia indicated a decrease in osteoclast number and surface area/bone surface from knockout compared to wild type mice. Osteoclasts derived from the marrow of knockout mice demonstrated decreased pit formation, osteoclast staining and osteoclast-specific gene expression compared to those from wild type mice. In response to metabolic acidosis, osteoclasts from knockout mice had decreased nuclear translocation of NFATc1, a transcriptional regulator of differentiation, and no increase in size or number compared to osteoclasts from wild type mice. Thus, loss of osteoclast OGR1 decreased both basal and metabolic acidosis-induced osteoclast activity indicating osteoclast OGR1 is important in mediating metabolic acidosis-induced bone resorption. Understanding the role of OGR1 in metabolic acidosis-induced bone resorption will provide insight into bone loss in acidotic patients with chronic kidney disease.

Vitamin D receptor (VDR) contributes to the development of hypercalciuria by sensitizing VDR target genes to vitamin D in a genetic hypercalciuric stone-forming (GHS) rat model

Human idiopathic hypercalciuria (IH) is the most common cause of calcium oxalate nephrolithiasis with perturbed calcium metabolism with increased bone resorption and decreased renal calcium reabsorption, which can be phenotype-copied in the genetic hypercalciuric stone-forming (GHS) rat model. We previously demonstrated that high VDR expression plays important roles in the development of hypercalciuria in the GHS rats. However, the underlying mechanism through which VDR impact hypercalciuria development remains to be fully understood. Here, we sought to determine how VDR regulated its target genes that are implicated in calcium homeostasis and potentially hypercalciuria. We found that VDR expression in the GHS rats was elevated in the calcium transporting tissues, as well as in the thymus and prostate, but not in lung, brain, heart, liver and spleen, when compared with control SD rats. Snail expression in the GHS rats was significantly downregulated in kidney, intestine, thymus and testis. Intraperitoneal injection of 1,25(OH)₂D₃ significantly upregulated the expression of renal calcium sensing receptor (CaSR), intestinal calcium transporters transient receptor potential vanilloid type 6 (TRPV6), and VDR in GHS rats, compared with that in control SD rats. ChIP assays revealed that VDR specifically bound to the proximal promoters of target genes, followed by histone H3 hyperacetylation or hypermethylation. Collectively, our results suggest that elevated VDR expression may contribute to the development of hypercalciuria by sensitizing VDR target genes to 1,25(OH)₂D₃ through histone modifications at their promoter regions in a genetic hypercalciuric stone-forming (GHS) rat model.

Associations of Serum Calciprotein Particle Size and Transformation Time With Arterial Calcification, Arterial Stiffness, and Mortality in Incident Hemodialysis Patients

RATIONALE & OBJECTIVE

Characteristics of the transformation of primary to secondary calciprotein particles (CPPs) in serum, including the size of secondary CPP (CPP2) aggregates and the time of transformation (T₅₀), may be markers for arterial calcification in patients undergoing hemodialysis (HD). We examined the associations of CPP2 aggregate size and T₅₀ with arterial calcification in incident HD patients.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

Incident HD patients (n=402with available CPP2 measures and n=388with available T₅₀ measures) from the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease (PACE) Study PREDICTORS: Serum CPP2 size and T₅₀ at baseline.

OUTCOMES

Primary outcomes were baseline coronary artery and thoracic aorta calcifications. Exploratory outcomes included baseline arterial stiffness, measured by pulse wave velocity (PWV) and ankle brachial index, and longitudinally, repeat measures of PWV and all-cause mortality.

ANALYTICAL APPROACH

Tobit regression, multiple linear regression, Poisson regression, linear mixed-effects regression, and Cox proportional hazards regression.

RESULTS

Mean age was 55±13 years, 41% were women, 71% were Black, and 57% had diabetes mellitus. Baseline CPP2 size and T₅₀ were correlated with baseline fetuin A level (r=-0.59 for CPP2 and 0.44 for T₅₀; P<0.001 for both), but neither was associated with baseline measures of arterial calcification or arterial stiffness. Baseline CPP2 size and T₅₀ were not associated with repeat measures of PWV. During a median follow-up of 3.5 (IQR, 1.7-6.2) years, larger CPP2 was associated with higher risk for mortality (HR, 1.17 [95% CI, 1.05-1.31] per 100nm larger CPP2 size) after adjusting for demographics and comorbid conditions, but there was no association between baseline T₅₀ and risk for mortality.

LIMITATIONS

Possible imprecision in assays, small sample size, limited generalizability to incident HD populations with different racial composition, and residual confounding.

CONCLUSIONS

In incident HD patients, neither CPP2 size nor T₅₀ was associated with prevalent arterial calcification and stiffness. Larger CPP2 was associated with risk for mortality, but this finding needs to be confirmed in future studies.

Association between dietary zinc intake and abdominal aortic calcification in US adults

BACKGROUND

In animal studies, zinc supplementation inhibited phosphate-induced arterial calcification. We tested the hypothesis that higher intake of dietary zinc was associated with lower abdominal aortic calcification (AAC) among adults in the USA. We also explored the associations of AAC with supplemental zinc intake, total zinc intake and serum zinc level.

METHODS

We performed cross-sectional analyses of 2535 participants from the National Health and Nutrition Examination Survey 2013-14. Dietary and supplemental zinc intakes were obtained from two 24-h dietary recall interviews. Total zinc intake was the sum of dietary and supplemental zinc. AAC was measured using dual-energy X-ray absorptiometry in adults ≥40 years of age and quantified using the Kauppila score system. AAC scores were categorized into three groups: no AAC (AAC = 0, reference group), mild-moderate (AAC >0-≤6) and severe AAC (AAC >6).

RESULTS

Dietary zinc intake (mean ± SE) was 10.5 ± 0.1 mg/day; 28% had AAC (20% mild-moderate and 8% severe), 17% had diabetes mellitus and 51% had hypertension. Higher intake of dietary zinc was associated with lower odds of having severe AAC. Per 1 mg/day higher intake of dietary zinc, the odds of having severe AAC were 8% lower [adjusted odds ratio 0.92 (95% confidence interval 0.86-0.98), P = 0.01] compared with those without AAC, after adjusting for demographics, comorbidities and laboratory measurements. Supplemental zinc intake, total zinc intake and serum zinc level were not associated with AAC.

CONCLUSIONS

Higher intake of dietary zinc was independently associated with lower odds of having severe AAC among noninstitutionalized US adults.

Patients with advanced chronic kidney disease and vascular calcification have a large hydrodynamic radius of secondary calciprotein particles

BACKGROUND

The size of secondary calciprotein particles (CPP2) and the speed of transformation (T50) from primary calciprotein particles (CPP1) to CPP2 in serum may be associated with vascular calcification (VC) in patients with chronic kidney disease (CKD).

METHODS

We developed a high throughput, microplate-based assay using dynamic light scattering (DLS) to measure the transformation of CPP1 to CPP2, hydrodynamic radius (Rh) of CPP1 and CPP2, T50 and aggregation of CPP2. We used this DLS assay to test the hypothesis that a large Rh of CPP2 and/or a fast T50 are associated with VC in 45 participants with CKD Stages 4-5 (22 without VC and 23 with VC) and 17 healthy volunteers (HV). VC was defined as a Kauppila score >6 or an Adragao score ≥3.

RESULTS

CKD participants with VC had larger cumulants Rh of CPP2 {370 nm [interquartile range (IQR) 272-566]} compared with CKD participants without VC [212 nm (IQR 169-315)] and compared with HV [168 nm (IQR 145-352), P < 0.01 for each]. More CPP2 were in aggregates in CKD participants with VC than those without VC (70% versus 36%). The odds of having VC increased by 9% with every 10 nm increase in the Rh of CPP2, after adjusting for age, diabetes, serum calcium and phosphate [odds ratio 1.09, 95% confidence interval (CI) 1.03, 1.16, P = 0.005]. The area under the receiver operating characteristic curve for VC of CPP2 size was 0.75 (95% CI 0.60, 0.90). T50 was similar in CKD participants with and without VC, although both groups had a lower T50 than HV.

CONCLUSIONS

Rh of CPP2, but not T50, is independently associated with VC in patients with CKD Stages 4-5.

Increased Osteoclast and Decreased Osteoblast Activity Causes Reduced Bone Mineral Density and Quality in Genetic Hypercalciuric Stone-Forming Rats

To study human idiopathic hypercalciuria (IH), we developed an animal model, genetic hypercalciuric stone-forming (GHS) rats, whose pathophysiology parallels that in IH. All GHS rats form kidney stones and have decreased BMD and bone quality compared with the founder Sprague-Dawley (SD) rats. To understand the bone defect, we characterized osteoclast and osteoblast activity in the GHS compared with SD rats. Bone marrow cells were isolated from femurs of GHS and SD rats and cultured to optimize differentiation into osteoclasts or osteoblasts. Osteoclasts were stained for TRAcP (tartrate resistant acid phosphatase), cultured to assess resorptive activity, and analyzed for specific gene expression. Marrow stromal cells or primary neonatal calvarial cells were differentiated to osteoblasts, and osteoblastic gene expression as well as mineralization was analyzed. There was increased osteoclastogenesis and increased resorption pit formation in GHS compared with SD cultures. Osteoclasts had increased expression of cathepsin K, Tracp, and MMP9 in cells from GHS compared with SD rats. Osteoblastic gene expression and mineralization was significantly decreased. Thus, alterations in baseline activity of both osteoclasts and osteoblasts in GHS rats, led to decreased BMD and bone quality, perhaps because of their known increase in vitamin D receptors. Better understanding of the role of GHS bone cells in decreased BMD and quality may provide new strategies to mitigate the low BMD and increased fracture risk found in patients with IH. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Mechanisms of Metabolic Acidosis-Induced Kidney Injury in Chronic Kidney Disease

Retrospective analyses and single-center prospective studies identify chronic metabolic acidosis as an independent and modifiable risk factor for progression of CKD. In patients with CKD, untreated chronic metabolic acidosis often leads to an accelerated reduction in GFR. Mechanisms responsible for this reduction include adaptive responses that increase acid excretion but lead to a decline in kidney function. Metabolic acidosis in CKD stimulates production of intrakidney paracrine hormones including angiotensin II, aldosterone, and endothelin-1 (ET-1) that mediate the immediate benefit of increased kidney acid excretion, but their chronic upregulation promotes inflammation and fibrosis. Chronic metabolic acidosis also stimulates ammoniagenesis that increases acid excretion but also leads to ammonia-induced complement activation and deposition of C3 and C5b-9 that can cause tubule-interstitial damage, further worsening disease progression. These effects, along with acid accumulation in kidney tissue, combine to accelerate progression of kidney disease. Treatment of chronic metabolic acidosis attenuates these adaptive responses; reduces levels of angiotensin II, aldosterone, and ET-1; reduces ammoniagenesis; and diminishes inflammation and fibrosis that may lead to slowing of CKD progression.

Trial design and baseline characteristics of CaLIPSO: a randomized, double-blind placebo-controlled trial of SNF472 in patients receiving haemodialysis with cardiovascular calcification

Background

The objective of CaLIPSO, a Phase 2b, randomized, double-blind, placebo-controlled clinical trial, is to test the hypothesis that myo-inositol hexaphosphate (SNF472) attenuates the progression of cardiovascular calcification in patients receiving maintenance haemodialysis. Here we report the trial design and baseline characteristics of trial participants.

Methods

Adult patients on maintenance haemodialysis (≥6 months) with an Agatston coronary artery calcium score, as measured by a multidetector computed tomography scanner, of 100-3500 U were enrolled. Patients were stratified by Agatston score (100-<400, 400-1000 or >1000 U) and randomized in a 1:1:1 ratio to receive placebo, SNF472 300 mg or SNF472 600 mg administered intravenously three times weekly during each haemodialysis session.

Results

Overall, 274 patients were randomized. The mean age of trial participants was 63.6 (standard deviation 8.9) years and 39% were women. The coronary artery, aorta and aortic valve median (25th-75th percentile) Agatston scores at baseline were 730 U (315-1435), 1728 U (625-4978) and 103 U (31-262), respectively, and the median (25th-75th percentile) calcium volume scores at baseline were 666 (310-1234), 1418 (536-4052) and 107 (38-278), respectively. Older age and diabetes mellitus were associated with higher calcium scores at baseline.

Conclusions

The CaLIPSO trial enrolled patients on haemodialysis with pre-existent cardiovascular calcification to test the hypothesis that SNF472 attenuates its progression in the coronary arteries, aorta and aortic valve.

Long-term safety and efficacy of veverimer in patients with metabolic acidosis in chronic kidney disease: a multicentre, randomised, blinded, placebo-controlled, 40-week extension

BACKGROUND

Metabolic acidosis, a complication of chronic kidney disease, causes protein catabolism and bone demineralisation and is associated with adverse kidney outcomes and mortality. Veverimer, a non-absorbed, counterion-free, polymeric drug candidate selectively binds and removes hydrochloric acid from the gastrointestinal lumen.

METHODS

We did a multicentre, randomised, blinded, placebo-controlled, 40-week extension of a 12-week parent study at 29 sites (hospitals and specialty clinics) in seven countries (Bulgaria, Georgia, Hungary, Serbia, Slovenia, Ukraine, and the USA). Eligible patients were those with chronic kidney disease (estimated glomerular filtration rate 20-40 mL/min per 1·73 m²) and metabolic acidosis (serum bicarbonate 12-20 mmol/L), who had completed the 12-week parent study, for which they were randomly assigned (4:3) to veverimer (6 g/day) or placebo as oral suspensions in water with food. Participants in the extension continued with the same treatment assignment as in the parent study. The primary endpoint was safety; the four secondary endpoints assessed the long-term effects of veverimer on serum bicarbonate concentration and physical functioning. The safety analysis set was defined as all patients who received any amount of study drug. This trial is registered at ClinicalTrials.gov, number NCT03390842, and has now completed.

FINDINGS

Participants entered the study between Dec 20, 2017, and May 4, 2018. Of the 217 patients randomly assigned to treatment in the parent study (124 to veverimer and 93 to placebo), 196 patients (114 veverimer and 82 placebo) continued on their blinded randomised treatment assignment into this 40-week extension study. Compared with placebo, fewer patients on veverimer discontinued treatment prematurely (3% vs 10%, respectively), and no patients on veverimer discontinued because of an adverse event. Serious adverse events occurred in 2% of veverimer-treated patients and in 5% of placebo patients (two of whom died). Renal system adverse events were reported in 8% and 15% in the veverimer and placebo groups, respectively. More patients on veverimer than placebo had an increase in bicarbonate (≥4 mmol/L or normalisation) at week 52 (63% vs 38%, p=0·0015) and higher bicarbonate concentrations were observed with veverimer than placebo at all timepoints starting at week 1 (p<0·001). Veverimer resulted in improved patient-reported physical functioning (Kidney Disease and Quality of Life-Physical Function Domain) versus placebo with a mean placebo-subtracted change at end of treatment of 12·1 points (SE 3·3; p<0·0001). Time to do the repeat chair stand test improved by 4·3 s (1·2) on veverimer versus 1·4 s (1·2) on placebo (p<0·0001).

INTERPRETATION

In patients with chronic kidney disease and metabolic acidosis, veverimer safely and effectively corrected metabolic acidosis and improved subjective and objective measures of physical function.

FUNDING

Tricida.

Effects of Treatment of Metabolic Acidosis in CKD: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Metabolic acidosis is associated with progression of CKD and has significant adverse effects on muscle and bone. A systematic review and meta-analysis was conducted to evaluate the benefits and risks of metabolic acidosis treatment with oral alkali supplementation or a reduction of dietary acid intake in those with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

MEDLINE, Embase, and Cochrane CENTRAL were searched for relevant trials in patients with stage 3-5 CKD and metabolic acidosis (<22 mEq/L) or low-normal serum bicarbonate (22-24 mEq/L). Data were pooled in a meta-analysis with results expressed as weighted mean difference for continuous outcomes and relative risk for categorical outcomes with 95% confidence intervals (95% CIs), using a random effects model. Study quality and strength of evidence were assessed using Cochrane risk of bias and the Grading of Recommendations Assessment, Development and Evaluation criteria.

RESULTS

Fourteen clinical trials were included (n=1394 participants). Treatment of metabolic acidosis with oral alkali supplementation or a reduction of dietary acid intake increased serum bicarbonate levels (14 studies, 1378 patients, mean difference 3.33 mEq/L, 95% CI, 2.37 to 4.29) and resulted in a slower decline in eGFR (13 studies, 1329 patients, mean difference -3.28 ml/min per 1.73 m2, 95% CI, -4.42 to -2.14; moderate certainty) and a reduction in urinary albumin excretion (very-low certainty), along with a reduction in the risk of progression to ESKD (relative risk, 0.32; 95% CI, 0.18 to 0.56; low certainty). Oral alkali supplementation was associated with worsening hypertension or the requirement for increased antihypertensive therapy (very-low certainty).

CONCLUSIONS

Low-to-moderate certainty evidence suggest that oral alkali supplementation or a reduction in dietary acid intake may slow the rate of kidney function decline and potentially reduce the risk of ESKD in patients with CKD and metabolic acidosis.

Chlorthalidone Is Superior to Potassium Citrate in Reducing Calcium Phosphate Stones and Increasing Bone Quality in Hypercalciuric Stone-Forming Rats

BACKGROUND

The pathophysiology of genetic hypercalciuric stone-forming rats parallels that of human idiopathic hypercalciuria. In this model, all animals form calcium phosphate stones. We previously found that chlorthalidone, but not potassium citrate, decreased stone formation in these rats.

METHODS

To test whether chlorthalidone and potassium citrate combined would reduce calcium phosphate stone formation more than either medication alone, four groups of rats were fed a fixed amount of a normal calcium and phosphorus diet, supplemented with potassium chloride (as control), potassium citrate, chlorthalidone (with potassium chloride to equalize potassium intake), or potassium citrate plus chlorthalidone. We measured urine every 6 weeks and assessed stone formation and bone quality at 18 weeks.

RESULTS

Potassium citrate reduced urine calcium compared with controls, chlorthalidone reduced it further, and potassium citrate plus chlorthalidone reduced it even more. Chlorthalidone increased urine citrate and potassium citrate increased it even more; the combination did not increase it further. Potassium citrate, alone or with chlorthalidone, increased urine calcium phosphate supersaturation, but chlorthalidone did not. All control rats formed stones. Potassium citrate did not alter stone formation. No stones formed with chlorthalidone, and rats given potassium citrate plus chlorthalidone had some stones but fewer than controls. Rats given chlorthalidone with or without potassium citrate had higher bone mineral density and better mechanical properties than controls, whereas those given potassium citrate did not.

CONCLUSIONS

In genetic hypercalciuric stone-forming rats, chlorthalidone is superior to potassium citrate alone or combined with chlorthalidone in reducing calcium phosphate stone formation and improving bone quality.

Etelcalcetide Is Effective at All Levels of Severity of Secondary Hyperparathyroidism in Hemodialysis Patients

Introduction

Calcimimetics improve parameters of secondary hyperparathyroidism (sHPT) but are mostly initiated when patients have severe disease, potentially limiting effectiveness. We evaluated the effects of etelcalcetide on lowering intact parathyroid hormone, calcium, and phosphate at different disease severity levels.

Methods

This analysis examined data from 2 parallel, phase 3, randomized, placebo-controlled, 26-week trials conducted in 1023 adult (≥18 years old) patients with sHPT on maintenance hemodialysis. Etelcalcetide effects by baseline intact parathyroid hormone stratum (<600, 600-1000, and >1000 ng/l) on mean percentage change in intact parathyroid hormone; changes in calcium and phosphate; and achieving serum intact parathyroid hormone ≤300 ng/l, phosphate <1.78 mmol/l, and both combined, were assessed.

Results

Etelcalcetide reduced serum intact parathyroid hormone by a similar percentage across baseline strata. A similar proportion achieved >30% intact parathyroid hormone reduction across strata for the etelcalcetide arms. Parathyroid hormone increased modestly in each placebo-group stratum, most prominently in the lowest stratum. Serum calcium and phosphate concentrations decreased across strata in etelcalcetide-treated patients, with the most pronounced reductions in patients with highest baseline parathyroid hormone. However, the proportion of patients achieving parathyroid hormone, phosphate, and both targets was highest in the lowest baseline parathyroid hormone stratum, where etelcalcetide dose requirements were lowest. Etelcalcetide dose requirement was lowest among patients in the lowest intact parathyroid hormone stratum.

Conclusion

Etelcalcetide effectively lowered serum intact parathyroid hormone, calcium, and phosphate, irrespective of the severity of secondary hyperparathyroidism. The ability to achieve target goals was greatest, and dose requirement smallest, when etelcalcetide was initiated among patients with the lowest level of disease severity.

Veverimer versus placebo in patients with metabolic acidosis associated with chronic kidney disease: a multicentre, randomised, double-blind, controlled, phase 3 trial

BACKGROUND

Patients with advanced chronic kidney disease lose the capacity to fully excrete endogenous acid, resulting in chronic metabolic acidosis that increases the risk of disease progression and causes muscle catabolism and bone resorption. Veverimer, a non-absorbed, counterion-free, polymeric drug, selectively binds and removes hydrochloric acid from the gastrointestinal lumen, unlike current oral sodium bicarbonate therapy for metabolic acidosis that only neutralises accumulated acid. We assessed the efficacy and safety of veverimer as a treatment for metabolic acidosis in patients with chronic kidney disease.

METHODS

We did a multicentre, parallel, randomised, double-blind, placebo-controlled study at 37 sites (hospitals and specialty clinics) in Bulgaria, Croatia, Georgia, Hungary, Serbia, Slovenia, Ukraine, and the USA. Eligible participants were patients aged 18-85 years with non-dialysis-dependent chronic kidney disease (estimated glomerular filtration rate of 20-40 mL/min per 1·73 m²) and metabolic acidosis (serum bicarbonate concentration of 12-20 mmol/L). Patients were randomly assigned (4:3) to veverimer 6 g/day or placebo for 12 weeks while they consumed their typical diet. Both drugs were taken as oral suspensions in water with lunch. Randomisation was done by study site personnel with a computer-generated randomisation code with balanced permuted blocks (block size of seven) and stratified by baseline bicarbonate (≤18 mmol/L vs >18 mmol/L). Patients and investigators were masked to treatment allocation; however, because the appearance of placebo differed from veverimer, a non-masked site staff member who had no other role in the study dispensed, prepared, and supervised dosing of the study drugs. The composite primary efficacy endpoint was the difference (veverimer-placebo) in the proportion of patients achieving at week 12 either an increase of 4 mmol/L or more from baseline in serum bicarbonate concentration or serum bicarbonate in the normal range of 22-29 mmol/L, assessed in the modified intention-to-treat population (all patients with a baseline and at least one post-baseline serum bicarbonate value). Patients fasted for at least 4 h (consuming only water) before measurements of bicarbonate. Safety was assessed in all patients who received any amount of study drug. This trial is registered with ClinicalTrials.gov, number NCT03317444.

FINDINGS

Between Sept 26, 2017, and Feb 9, 2018, we randomly assigned 124 participants to veverimer and 93 to placebo. The composite primary endpoint was met by 71 (59%) of 120 patients in the veverimer group versus 20 (22%) of 89 patients in the placebo group (a difference of 37%, 95% CI 23-49; p<0·0001). The most common body system in which adverse events in the veverimer group occurred was gastrointestinal; of these, non-treatment limiting diarrhoea was the most common event (11 [9%] vs three [3%] in the veverimer and placebo groups, respectively). The most common treatment-related adverse events were gastrointestinal (diarrhoea, flatulence, nausea, and constipation) occurring in 16 (13%) patients with veverimer and five (5%) patients with placebo. Two deaths occurred during the study, both in the placebo group (unstable angina and pneumonia).

INTERPRETATION

Veverimer effectively and safely corrected metabolic acidosis. Longer-term studies are warranted to assess the effects of veverimer on physical functioning and to assess other deleterious consequences of metabolic acidosis including progression of chronic kidney disease and bone health.

FUNDING

Tricida.

Low Sodium Diet Decreases Stone Formation in Genetic Hypercalciuric Stone-Forming Rats

BACKGROUND

Urine (u) calcium (Ca) excretion is directly dependent on dietary sodium (Na) intake leading to the recommendation for Na restriction in hypercalciuric kidney stone formers. However, there is no direct evidence that limiting Na intake will reduce recurrent stone formation.

MATERIALS AND METHODS

We used genetic hypercalciuric stone-forming (GHS) rats, which universally form Ca phosphate (P) kidney stones, fed either a low Na (LNa, 0.05%) or normal Na (NNa, 0.4%) Na diet (D) for 18 weeks. Urine was collected at 6-week intervals. Radiographic analysis for stone formation and bone analyses were done at the conclusion of the study.

RESULTS

Mean uCa was lower with LNaD than NNaD as was uP and LNaD decreased mean uNa and uChloride. There were no differences in urine supersaturation (SS) with respect to calcium phosphate (CaP) or Ca oxalate (CaOx). However, stone formation was markedly decreased with LNaD by radiographic analysis. The LNaD group had significantly lower femoral anterior-posterior diameter and volumetric bone mineral density (vBMD), but no change in vertebral trabecular vBMD. There were no differences in the bone formation rate or osteoclastic bone resorption between groups. The LNaD group had significantly lower femoral stiffness; however, the ultimate load and energy to fail was not different.

CONCLUSION

Thus, a low Na diet reduced uCa and stone formation in GHS rats, even though SS with respect to CaP and CaOx was unchanged and effects on bone were modest. These data, if confirmed in humans, support dietary Na restriction to prevent recurrent Ca nephrolithiasis.

Tolerance to Sodium in Patients With CKD-Induced Metabolic Acidosis: Does the Accompanying Anion Matter?

Patients with chronic kidney disease (CKD) continue to produce endogenous acids but have a reduction in net acid excretion, resulting in a primary decrease in serum bicarbonate concentration, which is termed chronic metabolic acidosis. Recent prospective studies, along with retrospective cohort analyses, demonstrate a higher risk for CKD progression with untreated metabolic acidosis. To normalize serum bicarbonate levels, acidemic patients are often treated with sodium bicarbonate (NaHCO₃) or sodium citrate, which have been shown to slow the progression of CKD. However, studies using this approach have routinely excluded patients with common sodium-sensitive comorbid conditions, such as poorly controlled hypertension, congestive heart failure, volume overload, or edema. This article examines the effect of the anion that accompanies sodium delivered with these therapies. Do the negative effects on blood pressure (BP) and sodium retention, as measured by an increase in edema, weight gain, and congestive heart failure, observed with oral administration of sodium chloride (NaCl) differ when a similar amount of sodium is given with bicarbonate or citrate in this patient population? A review of the literature suggests that NaHCO₃ does not increase BP or sodium retention when administered to patients with CKD during a concurrent severe NaCl dietary restriction (∼10 mEq/d). However, this degree of NaCl restriction is feasible only under strict control in clinical research environments. In contrast, when NaHCO₃ is given to patients without severe dietary NaCl restriction, there is an increase in BP and sodium retention. Thus, unless patients with CKD can tolerate a diet virtually devoid of NaCl, additional sodium, regardless of the accompanying anion, appears to increase BP and sodium retention.

Effects of the Potassium-Binding Polymer Patiromer on Markers of Mineral Metabolism

BACKGROUND AND OBJECTIVES

Patiromer is a sodium-free, nonabsorbed, potassium-binding polymer that uses calcium as the counter-exchange ion and is approved for treatment of hyperkalemia. The 4-week TOURMALINE study in patients with hyperkalemia previously demonstrated that patiromer administered once daily reduces serum potassium similarly when given with or without food. We report a prespecified exploratory efficacy analysis as well as a post hoc efficacy and safety analysis of the TOURMALINE study on circulating markers of mineral metabolism.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Adults with hyperkalemia (potassium >5.0 mEq/L) were randomized to once-daily patiromer 8.4 g without/with food for 4 weeks, with doses adjusted to achieve and maintain serum potassium 3.8-5.0 mEq/L. Baseline and week 4 serum and 24-hour urine markers of mineral metabolism are reported for all patients combined (evaluable for efficacy, n=112; evaluable for safety, n=113). P values were calculated using a paired t test for change from baseline, unless otherwise specified.

RESULTS

Mean (SD) baseline eGFR was 41±26 ml/min per 1.73 m². Mean (SD) changes from baseline to week 4 were 0.0±0.5 mg/dl (P=0.78; n=100) for albumin-corrected serum calcium, -0.2±0.2 mg/dl (P<0.001; n=100) for serum magnesium, and -0.1±0.7 mg/dl (P=0.47; n=100) for serum phosphate. Median (quartile 1, quartile 3) changes in 24-hour creatinine-normalized urine calcium and phosphate from baseline to week 4 were 2.5 (-11.5, 23.7) mg/24 h (P=0.10; n=69) and -43.0 (-162.6, 35.7) mg/24 h (P=0.004; n=95), respectively. Median (quartile 1, quartile 3) changes in intact parathyroid hormone and 1,25-dihydroxyvitamin D from baseline to week 4 were -13 (-31, 4) pg/ml (P<0.001; n=97) and -2 (-9, 3) pg/ml (P=0.05; n=96), respectively. There were no changes in fibroblast growth factor-23 or 25-hydroxyvitamin D. In patients (n=16) with baseline serum phosphate >4.8 mg/dL, the mean (SD) changes in serum and 24-hour creatinine-normalized urine phosphate from baseline to Week 4 were -0.6±0.8 mg/dl (n=13) and -149.1±162.6 mg/24hr (n=9), respectively.

CONCLUSIONS

Patiromer lowered urine phosphate in all patients, and lowered both serum and urine phosphate in a small subset of patients with hyperphosphatemia. Intact parathyroid hormone and 1,25-dihydroxyvitamin D decreased, with no change in serum calcium.

Relationship of acid-base status with arterial stiffness in community-living elders: the Health ABC Study

Background

Animal studies suggest that acidosis protects against arterial calcification, which contributes to arterial stiffness. The goal of this study was to investigate the associations of serum bicarbonate and pH with arterial stiffness in community-living older adults.

Methods

We performed cross-sectional analyses among 1698 well-functioning participants 70-79 years of age. Bicarbonate and pH were measured by arterialized venous blood gas at the point of care. Bicarbonate was categorized into low (<23 mEq/L), normal (23-27.9) and high (≥28). Arterialized venous pH (AVpH) was categorized into tertiles: ≤7.40, >7.40-7.42 and >7.42. Arterial stiffness was evaluated by pulse wave velocity (PWV) and high ankle-brachial index (ABI; >1.3/incompressible). We used linear and logistic regression to evaluate the association of bicarbonate and AVpH with PWV and high ABI, respectively.

Results

The mean age was 76 years and 15% had an estimated glomerular filtration rate (eGFR)  <60 mL/min/1.73 m2. The mean bicarbonate was 25.2 ± 2.1 mEq/L and the mean AVpH was 7.41 ± 0.03. Compared with participants in the normal bicarbonate category, those in the low bicarbonate group had 8.8% higher PWV (P = 0.006) and 1.87 greater odds of high ABI (P = 0.04). However, the associations were not significant after adjusting for eGFR (P = 0.24 and 0.43, respectively). There was no difference in PWV or high ABI across AVpH tertiles. Results were similar in those with and without chronic kidney disease and after excluding participants on diuretics.

Conclusions

We did not observe an independent association of bicarbonate or AVpH with arterial stiffness measured by high PWV or ABI in community-living older individuals. Future studies evaluating patients with a greater severity of chronic kidney disease and with more extreme alterations in acid-base status are warranted.

An in silico method to predict net calcium transfer during hemodialysis

International guidelines for chronic hemodialysis patients suggest a dialysate calcium concentration between 1.25 and 1.5 mmol/L. However, it is not certain if these dialysate calcium levels result in net calcium transfer into the patient. With ubiquitous prevalence of vascular calcification in hemodialysis patients, it is pertinent to model the mass balance of calcium during dialysis. To this end, we developed a two compartmental patient model and spatiotemporal representation of dialyzer model to investigate and quantify the calcium mass balance during dialysis. The model accounts for calcium-albumin binding and varying protein concentration; the latter accounts for the Gibbs-Donnan effect. The model simulations suggest that despite a lower dialysate calcium concentration of 1.25 mmol/L, some of our patients may be loaded with calcium during dialysis. This net calcium flux from dialysate to blood side may be a potential contributor to vascular calcification, a primary cause of cardiovascular mortality in hemodialysis patients.

Long-term effects of patiromer for hyperkalaemia treatment in patients with mild heart failure and diabetic nephropathy on angiotensin-converting enzymes/angiotensin receptor blockers: results from AMETHYST-DN

AIMS

Chronic kidney disease (CKD) in heart failure (HF) increases the risk of hyperkalaemia (HK), limiting angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin receptor blocker (ARB) use. Patiromer is a sodium-free, non-absorbed potassium binder approved for HK treatment. We retrospectively evaluated patiromer's long-term safety and efficacy in HF patients from AMETHYST-DN.

METHODS AND RESULTS

Patients with Type 2 diabetes, CKD, and HK [baseline serum potassium >5.0-5.5 mmol/L (mild) or >5.5-<6.0 mmol/L (moderate)], with or without HF (New York Heart Association Class I and II, by investigator judgement), on ACE-I/ARB, were randomized to patiromer 8.4-33.6 g to start, divided twice daily. Overall, 105/304 (35%) patients had HF (75%, Class II). Mean (standard deviation) ejection fraction (EF) was 44.9% (8.2) (n = 81) in patients with HF; 26 had EF ≤40%. In HF patients, mean serum potassium decreased by Day 3 through Week 52. At Week 4, estimated mean (95% confidence interval) change in serum potassium was -0.64 mmol/L (-0.72, -0.55) in mild and -0.97 mmol/L (-1.14, -0.80) in moderate HK (both P < 0.0001). Most HF patients with mild (>88%) and moderate (≥73%) HK had normokalaemia at each visit from Weeks 12 to 52. Three HF patients were withdrawn because of high (n = 1) or low (n = 2) serum potassium. The most common patiromer-related adverse event was hypomagnesaemia (8.6%).

CONCLUSIONS

In patients with a clinical diagnosis of HF, diabetes, CKD, and HK on ACE-I/ARB, patiromer was well tolerated and effective for HK treatment over 52 weeks.

Evaluation of an individualized dose titration regimen of patiromer to prevent hyperkalaemia in patients with heart failure and chronic kidney disease

AIMS

Hyperkalaemia risk precludes optimal renin-angiotensin-aldosterone system inhibitor use in patients with heart failure (HF), particularly those with chronic kidney disease (CKD). Patiromer is a sodium-free, non-absorbed potassium (K+ )-binding polymer approved for the treatment of hyperkalaemia. In PEARL-HF, patiromer 25.2 g (fixed dose) prevented hyperkalaemia in HF patients with or without CKD initiating spironolactone. The current study evaluated the effectiveness of a lower starting dose of patiromer (16.4 g/day) followed by individualized titration in preventing hyperkalaemia and hypokalaemia when initiating spironolactone.

METHODS AND RESULTS

This open-label 8-week study enrolled 63 patients with CKD, serum K+ 4.3-5.1 mEq/L, and chronic HF, who, based on investigator opinion, should receive spironolactone. Eligible patients started spironolactone 25 mg/day and patiromer 16.8 g/day (divided into two doses), with patiromer titrated to maintain serum K+ 4.0-5.1 mEq/L. Mean (standard deviation) serum K+ was 4.78 (0.51) mEq/L at baseline; weekly values were 4.48-4.70 mEq/L during treatment. Serum K+ of 3.5-5.5 mEq/L at the end of study treatment (primary endpoint) was achieved by 57 (90.5%) patients; 53 (84.1%) had serum K+ 4.0-5.1 mEq/L. One patient (1.6%) developed hypokalaemia, and two patients (3.2%) developed hypomagnesaemia. Spironolactone was increased to 50 mg/day in all patients; 43 (68%) patients required one or more patiromer dose titration. Adverse events (AEs) occurred in 36 (57.1%) patients, with a low rate of discontinuations [four (6.3%) patients]. The most common AE was mild to moderate abdominal discomfort [four (6.3%) patients].

CONCLUSIONS

In this open-label study, patiromer 16.8 g/day followed by individualized titration maintained serum K+ within the target range in the majority of patients with HF and CKD, all of whom were uptitrated to spironolactone 50 mg/day, patiromer was well tolerated, with a low incidence of hyperkalaemia, hypokalaemia, and hypomagnesaemia.

Effect of Patiromer on Hyperkalemia Recurrence in Older Chronic Kidney Disease Patients Taking RAAS Inhibitors

BACKGROUND

Older people are predisposed to hyperkalemia because of impaired renal function, comorbid conditions, and polypharmacy. Renin-angiotensin-aldosterone system inhibitors (RAASi), which are recommended to treat chronic kidney disease and heart failure augment the risk. Patiromer, a nonabsorbed potassium binder, was shown in the phase 3 OPAL-HK study to decrease serum potassium in patients with chronic kidney disease taking RAASi. We studied the efficacy and safety of patiromer in a prespecified subgroup of patients aged ≥65 years from OPAL-HK.

METHODS

Chronic kidney disease patients with mild or moderate-to-severe hyperkalemia received patiromer, initially 8.4 g/d or 16.8 g/d, respectively, for 4 weeks (treatment phase, part A). Eligible patients entered an 8-week randomized withdrawal phase (part B) and continued patiromer or switched to placebo.

RESULTS

Mean ± standard error change in serum potassium from baseline to week 4 of part A (primary endpoint) in patients aged ≥65 years was -1.01 ± 0.05 mEq/L (P < .001); 97% achieved serum potassium 3.8-<5.1 mEq/L. The serum potassium increase during the first 4 weeks of part B was greater in patients taking placebo than in those taking patiromer (P < .001). Fewer patients taking patiromer (30%) than placebo (92%) developed recurrent hyperkalemia (serum potassium ≥5.1 mEq/L). Mild-to-moderate constipation occurred in 15% (part A) and 7% (part B) of patients aged ≥65 years. Serum potassium <3.5 mEq/L and serum magnesium <1.4 mg/dL were infrequent (4% each in patients aged ≥65 years in part A).

CONCLUSIONS

Patiromer reduced recurrent hyperkalemia and was well tolerated in older chronic kidney disease patients taking RAASi.

Randomized, Controlled Trial of TRC101 to Increase Serum Bicarbonate in Patients with CKD

BACKGROUND AND OBJECTIVES

Metabolic acidosis is common in patients with CKD and has significant adverse effects on kidney, muscle, and bone. We tested the efficacy and safety of TRC101, a novel, sodium-free, nonabsorbed hydrochloric acid binder, to increase serum bicarbonate in patients with CKD and metabolic acidosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

One hundred thirty-five patients were enrolled in this randomized, double-blind, placebo-controlled, multicenter, in-unit study (designated the TRCA-101 Study). Patients had a mean baseline eGFR of 35 ml/min per 1.73 m2, a mean baseline serum bicarbonate of 17.7 mEq/L, and comorbidities, including hypertension (93%), diabetes (70%), and heart failure (21%). Patients ate a controlled diet and were treated for 14 days with placebo or one of four TRC101 dosing regimens (1.5, 3, or 4.5 g twice daily or 6 g once daily). After treatment, patients were discharged and followed for 7-14 days.

RESULTS

All TRC101 treatment groups had a mean within-group increase in serum bicarbonate of ≥1.3 mEq/L (P<0.001) within 72 hours of the first dose and a mean increase in serum bicarbonate of 3.2-3.9 mEq/L (P<0.001) at the end of treatment compared with placebo, in which serum bicarbonate did not change. In the combined TRC101 treatment group, serum bicarbonate was normalized (22-29 mEq/L) at the end of treatment in 35% of patients and increased by ≥4 mEq/L in 39% of patients. After discontinuation of TRC101, serum bicarbonate decreased nearly to baseline levels within 2 weeks. All adverse events were mild or moderate, with gastrointestinal events most common. All patients completed the study.

CONCLUSIONS

TRC101 safely and significantly increased the level of serum bicarbonate in patients with metabolic acidosis and CKD.

Association of Serum Potassium with All-Cause Mortality in Patients with and without Heart Failure, Chronic Kidney Disease, and/or Diabetes

BACKGROUND

The relationship between serum potassium, mortality, and conditions commonly associated with dyskalemias, such as heart failure (HF), chronic kidney disease (CKD), and/or diabetes mellitus (DM) is largely unknown.

METHODS

We reviewed electronic medical record data from a geographically diverse population (n = 911,698) receiving medical care, determined the distribution of serum potassium, and the relationship between an index potassium value and mortality over an 18-month period in those with and without HF, CKD, and/or DM. We examined the association between all-cause mortality and potassium using a cubic spline regression analysis in the total population, a control group, and in HF, CKD, DM, and a combined cohort.

RESULTS

27.6% had a potassium <4.0 mEq/L, and 5.7% had a value ≥5.0 mEq/L. A U-shaped association was noted between serum potassium and mortality in all groups, with lowest all-cause mortality in controls with potassium values between 4.0 and <5.0 mEq/L. All-cause mortality rates per index potassium between 2.5 and 8.0 mEq/L were consistently greater with HF 22%, CKD 16.6%, and DM 6.6% vs. controls 1.2%, and highest in the combined cohort 29.7%. Higher mortality rates were noted in those aged ≥65 vs. 50-64 years. In an adjusted model, all-cause mortality was significantly elevated for every 0.1 mEq/L change in potassium <4.0 mEq/L and ≥5.0 mEq/L. Diuretics and renin-angiotensin-aldosterone system inhibitors were related to hypokalemia and hyperkalemia respectively.

CONCLUSION

Mortality risk progressively increased with dyskalemia and was differentially greater in those with HF, CKD, or DM.

Stimulation of fibroblast growth factor 23 by metabolic acidosis requires osteoblastic intracellular calcium signaling and prostaglandin synthesis

Serum fibroblast growth factor 23 (FGF23) increases progressively in chronic kidney disease (CKD) and is associated with increased mortality. FGF23 is synthesized in osteoblasts and osteocytes; however, the factors regulating its production are not clear. Patients with CKD have decreased renal acid excretion leading to metabolic acidosis (MET). During MET, acid is buffered by bone with release of mineral calcium (Ca) and phosphate (P). MET increases intracellular Ca signaling and cyclooxygenase 2 (COX2)-induced prostaglandin production in the osteoblast, leading to decreased bone formation and increased bone resorption. We found that MET directly stimulates FGF23 in mouse bone organ cultures and primary osteoblasts. We hypothesized that MET increases FGF23 through similar pathways that lead to bone resorption. Neonatal mouse calvariae were incubated in neutral (NTL, pH = 7.44, Pco₂ = 38 mmHg, [HCO₃^-] = 27 mM) or acid (MET, pH = 7.18, Pco₂ = 37 mmHg, [HCO₃^-] = 13 mM) medium without or with 2-APB (50 μM), an inhibitor of intracellular Ca signaling or NS-398 (1 μM), an inhibitor of COX2. Each agent significantly inhibited MET stimulation of medium FGF23 protein and calvarial FGF23 RNA as well as bone resorption at 48 h. To exclude the potential contribution of MET-induced bone P release, we utilized primary calvarial osteoblasts. In these cells each agent inhibited MET stimulation of FGF23 RNA expression at 6 h. Thus stimulation of FGF23 by MET in mouse osteoblasts utilizes the same initial signaling pathways as MET-induced bone resorption. Therapeutic interventions directed toward correction of MET, especially in CKD, have the potential to not only prevent bone resorption but also lower FGF23 and perhaps decrease mortality.