Advances in management of chronic metabolic acidosis in CKD

Abstract

Purpose of review:

Chronic metabolic acidosis is a common complication of chronic kidney disease (CKD) and is associated with adverse consequences such as CKD progression and muscle wasting. We review the findings from recent clinical trials that have examined the effects of sodium bicarbonate therapy and veverimer in patients with CKD and chronic metabolic acidosis.

Recent findings:

There are 4 recent clinical trials on chronic metabolic acidosis of CKD. In a pilot, cross-over study, 6 weeks of sodium bicarbonate therapy improved vascular endothelial function, measured by brachial artery flow-mediated dilation. In a single-center, randomized, open label study, 6 months of sodium bicarbonate therapy increased muscle mass and lean body mass, and preserved kidney function. The other 2 clinical trials (phase 1/2 and phase 3 studies) examined the effects of veverimer, which is a hydrochloric acid binder. The phase 3 study showed that 12-weeks of veverimer increased serum bicarbonate levels and might improve physical function. The effects of veverimer on CKD progression, physical function and cardiovascular endpoints as well as its long-term safety are yet to be determined.

Summary:

Recent studies suggest that sodium bicarbonate therapy may improve vascular endothelial function and muscle mass and preserve renal function. Veverimer increases serum bicarbonate level and could be a potential new therapeutic option for treating chronic metabolic acidosis.

Introduction

As kidney function declines, the ability of the kidneys to excrete acid decreases leading to acid retention and the development of chronic metabolic acidosis.¹ Chronic metabolic acidosis is common in patients with advanced chronic kidney disease (CKD),^2,3 and is associated with several adverse consequences such as CKD progression, muscle wasting, bone loss and cardiovascular mortality.^4–6 In the past decade, several small interventional studies have examined the effects of alkali therapy using sodium bicarbonate or base-producing fruits and vegetables on these adverse consequences, especially on the progression of CKD, and demonstrated promising beneficial effects of alkali therapy.^7–9

The guidelines from the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) and Kidney Disease Improving Global Outcomes (KDIGO) suggest to treat chronic metabolic acidosis with alkali therapy;^10,11 however, the evidence supporting these guidelines is limited due to the small sample size of existing clinical trials and potential study biases resulting from the lack of blinding. Several research groups have reviewed the management of metabolic acidosis in CKD.^5,7,8,12,13 In this article, we focus on 4 clinical trials that were published in the past 18 months. Two of these studies tested the effect of sodium bicarbonate therapy, while the other 2 tested that of veverimer, which is a hydrochloric acid binder (Table 1).^14–17

Table 1.

Study design and findings of recent clinical trials on the treatment of chronic metabolic acidosis

	Effect of sodium bicarbonate therapy on vascular endothelial function (2018)14	Effect of sodium bicarbonate therapy on muscle mass and renal function (2018)15	Phase 1/2 study of veverimer (2018)16	Phase 3 study of veverimer (2019)17
Study design	Pilot study, open-label, randomized crossover	Single-center, open-label, randomized, prospective parallel-groups	Randomized, double-blind, placebo-controlled, parallel-design, six-arm, fixed dose, multicenter, in-unit	Randomized, double-blind, placebo-controlled, parallel, multicenter
Study population	eGFR 15–44 mL/min per 1.73m2 and serum bicarbonate 16–21 mEq/L	CKD stage 3 and 4 and bicarbonate levels <22 mEq/L	eGFR 20 to <60 mL/min per 1.73m2 and serum bicarbonate 12–20 mEq/L	Adults with eGFR 20–40 mL/min per 1.73m2 and serum bicarbonate 12–20 mEq/L
Notable exclusion criteria	Uncontrolled hypertension; overt congestive heart failure (New York Heart Association Class unspecified)	Decompensated heart failure; prior bicarbonate therapy for a duration of >2 weeks	Systolic blood pressure ≥170 mmHg; heart failure with New York Heart Association Class III & IV	Systolic blood pressure ≥170 mmHg; heart failure with New York Heart Association Class IV
Sample size	20	188: 94 (treatment), 94 (control)	135: 104 (treatment), 31 (placebo)	217: 124 (treatment), 93 (placebo)
Intervention	Oral sodium bicarbonate for 6 weeks to goal serum bicarbonate of ≥23 mEq/L	Sodium bicarbonate supplementation to maintain bicarbonate levels at 24–26 mEq/L in addition to standard care per KDIGO 2012 guidelines	Veverimer 1.5 g twice daily, 3g twice daily, 4.5 g twice daily or 6 g once daily	Veverimer 6 g once daily for 3 weeks, then titrated to a target bicarbonate of 22–29 mEq/L (0–9 g/day)
Control	No medication	Standard care per KDIGO 2012 guidelines	Placebo	Placebo
Diet	N/A	Participant received comprehensive nutritional counseling	Controlled, low protein diet (~0.7 g/kg/day)	Variable dietary protein intake; but participants received dietary counseling
Duration	14 weeks (including a 2-week washout period)	6 months	2 weeks	12 weeks
Endpoints	Primary: Change in brachial artery flow-mediated dilation Secondary: changes in markers of inflammation, bone turnover, mineral metabolism and calcification	Primary: change in mid-arm muscle circumference and lean body mass Secondary: change in eGFR from baseline	Primary: Change of serum bicarbonate from baseline to the end of treatment	Primary: the difference between the treatment and placebo in the proportion of patients achieving either an increase of ≥4 mEq/L serum bicarbonate from the baseline or achieving a serum bicarbonate between 22 and 29 mEq/L Secondary: change from baseline to week 12 in total score of the KDQoL physical function domain and the duration of the repeated chair-stand test
Findings	Primary: flow-mediated dilation improved during the treatment period (p=0.04) while there was no change in the control period Secondary: no change in bone markers or serum calcification propensity. Serum phosphorous and intake fibroblast growth factor 23 increased during the treatment period.	Primary: compared to the control group, participants in the treatment group had higher lean body mass and mid-arm muscle circumference Secondary: eGFR increased in the treatment group (from 29.2 to 32.7 ml/min per 1.73m2), but decreased in the control group (31.5 to 28.2 ml/min/1.73m2).	Primary: Mean increase in bicarbonate of 3.2–3.9 mEq/L (p<0.001) in the treatment groups while there was no change in the placebo group.	Primary: 59% in the treatment group vs. 22% in the placebo met the primary endpoint (p<0.001) Secondary: KDQoL physical function domain improved significantly in the treatment group vs. placebo (p=0.01); no change in chair-stand time (p=0.06)
Major limitations	Small sample size, short study duration, open-label, no placebo control	Open-label study, high prevalence of CKD of unidentified etiology	Short study duration, only endpoint was the change in serum bicarbonate	Primary endpoint was the change in serum bicarbonate level

Abbreviations: N/A, not available; KDIGO, Kidney Disease: Improving Global Outcome; KDQoL, Kidney Disease and Quality of Life.

Effects of sodium bicarbonate therapy on cardiovascular endpoints

Current clinical guidelines suggest to treat chronic metabolic acidosis with alkali therapy,^10,11 but animal studies suggest that alkalosis may actually worsen arterial calcification^18,19 and observational studies show that high serum bicarbonate levels were associated with subclinical cardiovascular disease and heart failure.^6,20 The effects of sodium bicarbonate therapy on cardiovascular endpoints had not been studied until recently by Kendrick et al.¹⁴ In a pilot, randomized cross-over study, Kendrick et al. examined the effect of sodium bicarbonate therapy on vascular endothelial function (measured by brachial artery flow-mediated dilation) in 20 patients with estimated glomerular filtration rate (eGFR) of 15–44 ml/min per 1.73m² and serum bicarbonate level of 16–21 mEq/L.¹⁴ During the treatment period, participants were treated with oral sodium bicarbonate for 6 weeks to a goal serum bicarbonate level of ≥23 mEq/L. During the 6-week control period, participants received no alkali therapy or placebo control. There was a 2-week washout period in between.

The serum bicarbonate level increased by 2.7 ± 2.9 mEq/L during the treatment period compared to baseline (p<0.001), but did not change in the control period. Compared to the control period, brachial artery flow-mediated dilation significantly increased during the treatment period with a mean increase of 1.8% (95% confidence interval (CI) 0.3 to 3.3%, p=0.02). The effects of sodium bicarbonate on other secondary cardiovascular endpoints were also explored. Sodium bicarbonate treatment did not change calcification propensity in the serum, but significantly increased serum phosphorous and fibroblast growth factor 23 (FGF-23). The findings of the pilot study suggest a potential beneficial effect of sodium bicarbonate therapy on vascular endothelial function. In a meta-analysis including 5,547 participants, every 1% increase in brachial flow-mediated diameter was associated with 13% reduction in pooled relative risks of cardiovascular events (relative risk=0.87, 95% CI 0.83–0.91).²¹ However, the overall cardiovascular effect of sodium bicarbonate remains unclear since sodium bicarbonate therapy also increased serum phosphorous and FGF-23 levels, which are also known risk factors for cardiovascular events and mortality.^22,23 In addition, the mechanism by which sodium bicarbonate might have improved vascular endothelial function is unclear.¹⁴

This study is limited by small sample size, short duration, lack of blinding and of placebo administration in the control period, but it is a step forward in investigating cardiovascular effects of sodium bicarbonate. Larger trials are needed to determine the long-term effect of sodium bicarbonate therapy on cardiovascular morbidity and mortality, and to investigate the contradictory effects of sodium bicarbonate on vascular endothelial function, serum phosphorus and FGF-23.

Effects of sodium bicarbonate therapy on muscle mass

Chronic metabolic acidosis is associated with muscle wasting in patients with CKD and may contribute to muscle wasting by impairing insulin and insulin-like growth factor-1 signaling, causing negative nitrogen balance and leading to skeletal muscle protein breakdown.⁸ Recently, Dubey et al. conducted a single-center, open-label, randomized, prospective parallel-group study to assess the effect of sodium bicarbonate on muscle mass.¹⁵ A total of 188 patient with CKD stage 3 and 4 and bicarbonate levels <22 mEq/L were randomized to receive oral sodium bicarbonate supplementation to maintain bicarbonate levels at 24–26 mEq/L while receiving standard care as per KDIGO guidelines or to receive the standard care alone. Muscle mass was assessed by mid-arm muscle circumference (calculated using mid-arm circumference and triceps skinfold thickness) and lean body mass (measured using Dual-energy X-ray absorptiometry). Only 2 participants in the treatment group did not reach the target bicarbonate levels. Consistent with the results from prior studies,^24,25 sodium bicarbonate therapy resulted in higher mid-arm muscle circumference (22.9 versus 22.6 cm, p=0.001) and lean body mass (36.8 vs. 36 kg, p=0.002) when compared with the control group. This is one of the largest studies to date to examine the musculoskeletal effects of sodium bicarbonate therapy.

Effects of sodium bicarbonate therapy on renal function

Dubey et al. also examined the change in eGFR as a secondary endpoint.¹⁵ Chronic metabolic acidosis may contribute to CKD progression by promoting tubulointerstitial injury via ammonia-induced complement activation and increased production of endothelin-1 and aldosterone.⁸ Several interventional studies have demonstrated that sodium bicarbonate therapy slowed CKD progression.^9,24,26 Consistent with these studies,^24,26,27 Dubey et al. found that eGFR increased in the treatment group (from 29.2 to 32.7 ml/min per 1.73m²) but decreased in the control group (31.5 to 28.2 ml/min per 1.73m²). Whereas most clinical trials on sodium bicarbonate therapy were performed in either a European country or the United States, where the etiology of CKD was mainly diabetes and hypertension,^24,28 the study by Dubey et al. was performed in India with CKD of unidentified etiology being most common (52%). The geographic area of the study had very hot and humid summers, so despite having a 4-week pre-recruitment observation period, the participants might have subclinical acute kidney injury resulting from dehydration.¹⁵ The high proportion of patients with CKD of unidentified etiology and the possible underdiagnosed acute kidney injury episodes might overestimate the reno-protective effect of sodium bicarbonate therapy in this study.

Ongoing or unpublished clinical trials on sodium bicarbonate therapy

Besides the above studies on sodium bicarbonate therapy,^14,15 which are recent, there are also 6 clinical trials that are ongoing or have not been published (Table 2).^29–33 The primary endpoints of these studies include changes in renal and physical function as well as safety and tolerability of sodium bicarbonate. Aspects of 2 of these studies are worth highlighting. First, in the study done in the United Kingdom, the study population is elderly CKD patients (age ≥60 years).³¹ It is important to study this patient population because elders make up the majority of people with advanced CKD,³⁴ and polypharmacy is prevalent in this population and is associated with negative clinical consequences.³⁵ Second, the Bicarbonate Administration to Stabilize eGFR (BASE) study³⁶ tests the safety and tolerability of sodium bicarbonate at different doses (0.8 versus 0.5 mEq/kg/day of lean body weight) and compares them with placebo. The primary objective of the BASE study is to determine the best dose of sodium bicarbonate to prescribe in a future trial. The results of these 3 trials will add important new information to the literature.

Table 2.

Ongoing or unpublished clinical trials of sodium bicarbonate therapy in CKD

Title	Design	Population	Site(s)	Sample size	Intervention	Control	Duration	Primary endpoint	Status
Placebo-controlled randomized clinical trial of alkali therapy in patients with CKD ()29	Randomized, placebo-controlled	eGFR 15–45 mL/min per 1.73m2 and serum bicarbonate 20–25 mEq/L	Bronx, New York and Cleveland, Ohio	149	Sodium bicarbonate 0.4 mEq/kg/day ideal body weight to be taken once a day	Placebo	12 months	Sit to stand to sit speed and bone mineral density at the wrist	Completed in 8/2016
A prospective, controlled, randomized, multicentric study: correction of metabolic acidosis with use of bicarbonate in chronic renal insufficiency ()30	Multicentric, prospective, cohort, randomized, open-label and controlled	CKD stage 3b-4 with serum bicarbonate ≥18 mEq/L*	Italy	728	Sodium bicarbonate therapy to keep serum bicarbonate above 24 mEq/L	Usual care (no bicarbonate)	36 months	Doubling of creatinine	Estimated completion date: 12/2017
Does oral sodium bicarbonate therapy improve function and quality of life in older patients with CKD and low-grade acidosis? (EudraCT# 2011–005271-16)31	A multicenter randomized placebo-controlled trial	Age 60 and older, CKD stage 4–5, serum bicarbonate<22 mEq/L	United Kingdom (27 centers)	300	Sodium bicarbonate 500mg 3 times a day, titrated up to 1 gram 3 times a day after 3 months if bicarbonate <22mmol/L	Placebo	12 months	Change in Short Physical Performance Battery score	Completed in 2/2018
Investigations of the Optimum Serum Bicarbonate Level in Renal Disease ()32	Randomized, placebo-controlled	Diabetic, CKD stage 2–4 and serum bicarbonate 22–28 mEq/L	Salt Lake City, Utah	74	Sodium bicarbonate 0.5 mEq/kg/day ideal body weight to be taken twice a day	Placebo	6 months	Change in urinary transforming growth factor beta 1	Completed in 5/2018
Oral sodium bicarbonate supplementation in patients with chronic metabolic acidosis and CKD (EUDRACT# 2012–001824-36)33	Randomized, controlled, open-label	CKD stage 3–4 and serum bicarbonate <21 mEq/L	Austria	200	Sodium bicarbonate with a target serum bicarbonate of 24±1 mEq/L	Rescue therapy with sodium bicarbonate with target serum bicarbonate of 20±1 mEq/L	24 months	eGFR	Ongoing
The BASE Study: Bicarbonate Administration to Stabilize eGFR ()36	Randomized, placebo-controlled	eGFR 20–24 mL/min per 1.73m2, or 45–59 mL/min per 1.73m2 plus urine albumin:creatinine ≥100 mg/gm	United states (6 centers)	194	Low dose sodium bicarbonate: 0.5 mEq/kg/day lean body weight; high-dose: 0.8 mEq/kg/day lean body weight	Placebo	28 weeks	Safety and tolerability: Percentage of participants in each dose arm who are prescribed (i) full randomized sodium bicarbonate dose per protocol at end of the study and (ii) ≥25% of randomized sodium bicarbonate dose	Estimated completion date: 6/2018

^*unclear whether there is an upper limit of serum bicarbonate level

Sodium bicarbonate therapy and sodium retention

Due to the concern of sodium retention associated with sodium bicarbonate therapy, the study by Kendrick et al.¹⁴ excluded participants with uncontrolled hypertension and/or overt congestive heart failure, and the study by Dubey et al.¹⁵ excluded those with decompensated heart failure. Every 650 mg of sodium bicarbonate introduces ~180 mg of sodium. Physiologic studies from 1970–1990’s suggest that sodium bicarbonate does not result in as clinically significant sodium retention as sodium chloride because sodium is more readily excreted as sodium bicarbonate than as sodium chloride.^37,38 However, all of these studies were limited by small sample size (n=5 to 10) and were performed under a very strict restriction of dietary sodium (~200 to 700 mg per day).³⁹ The dietary sodium restriction limits the generalizability of these findings, as in clinical settings it is difficult for CKD patients to conform to a dietary sodium restriction of even 2 g per day.³⁹ In the study by Kendrick et al.,¹⁴ 4 (20%) patients reported leg swelling and 1 patient required escalation of diuretic dose during the treatment period of sodium bicarbonate. The authors did not report any adverse events during the control period. In the open-label study by Dubey et al., the mean dose of sodium bicarbonate required for attaining the target bicarbonate level (i.e. 24–26 mEq/L) of the study was 2.3 g per day.¹⁵ Compared to the control group, more participants had increased requirement of diuretics (35% vs. 18%, p=0.008) in the sodium bicarbonate group.¹⁵ Hopefully, the BASE pilot study³⁶ will provide more definitive evidence on the effect of sodium bicarbonate on salt retention.

Emergence of a hydrochloric acid binder

In the past year, veverimer (formerly designated as TRC101), a hydrochloric acid binder, emerged as a potential therapeutic agent for chronic metabolic acidosis in CKD, especially for those who cannot tolerate the additional sodium load from sodium bicarbonate.^16,17 According to the pharmacological data published in the supplementary appendix of the phase 3 study,¹⁷ veverimer is a polyamine. It is protonated after ingestion and selectively binds to chloride anions resulting in a net reduction and removal of hydrochloric acid from the gastrointestinal tract. Veverimer is non-absorbable, and since it is not an ion-exchanger, it does not introduce counterions such as sodium and potassium.¹⁷

Short term effect of veverimer on serum bicarbonate levels and physical function

The effect of veverimer on serum bicarbonate levels was examined in a phase 1/2 and phase 3 study. In the phase 1/2 study, 135 participants with eGFR between 20 and <60 mL/min per 1.73m² and serum bicarbonate between 12–20 mEq/L were randomized to receive either placebo or one of the 4 treatment regimens (1.5 g, 3g, 4.5 g twice daily and 6 g once daily) for 2 weeks.¹⁶ During the 2 weeks of intervention, participants resided in a clinical research unit and ate a controlled diet with a mean dietary protein intake of 0.7 g/kg per day. Veverimer caused a steady rise in serum bicarbonate in all treatment groups. By the end of 2 weeks, mean serum bicarbonate increased by 3.2 to 3.9 mEq/L in the treatment groups, but did not change in the placebo group. In the combined veverimer treatment group, serum bicarbonate was normalized (i.e. to bicarbonate of 22–29 mEq/L) in 35% of participants and increased by 4 mEq/L or greater in 39% at the end of treatment. No apparent dose effect was observed among 4 treatment regimens.

The phase 3 trial was a 12-week, multicenter, parallel, randomized, double-blind, placebo-controlled study at 37 sites in 8 countries including the United States.¹⁷ The study population was similar to that of the phase 1/2 study but with a slightly lower eGFR (20–40 ml/min per 1.73m²). One hundred twenty-four participants were randomized to receive either 6 g of veverimer or placebo once daily. The dose of 6 g once daily was chosen due to dosing convenience and based on the efficacy and safety findings from the phase 1/2 study. This dose also provided the option to up or down titrate veverimer. Beginning at week 4, veverimer was titrated to a target bicarbonate of 22–29 mEq/L and a maximum dose of 9 g once daily. The study was conducted outpatient. All participants were provided with dietary counseling without controlling the intake of dietary protein. The primary end point was the difference between the treatment and placebo groups in the proportion of patients achieving either an increase of ≥4 mEq/L in serum bicarbonate level from the baseline or achieving a serum bicarbonate between 22 and 29 mEq/L. At the end of 12 weeks, more participants in the treatment group (59%) met the primary endpoint compared to the placebo group (22%, p<0.001). The mean increase in serum bicarbonate was 4.4 mEq/L in the treatment group compared to 1.8 mEq/L in the placebo group (p<0.001).

The phase 3 study also explored the effect of veverimer on physical function.¹⁷ In our small single-blinded pilot study of 20 adults with CKD and metabolic acidosis, 6 week treatment of oral sodium bicarbonate improved physical function, measured by sit-to-stand time.⁴⁰ Treatment with veverimer significantly increased physical function measured by the physical function domain from the Kidney Disease and Quality of Life Instrument, which quantifies the participants’ self-reported degree of limitation in doing daily activities such as climbing stairs and walking. Physical function, as measured by the repeated chair-stand test also improved in the treatment group (p=0.02); however, when compared to the placebo group, the difference was not significant (p=0.06).

Compared to the published clinical trials on sodium bicarbonate therapy,⁹ the phase 3 study on veverimer had several strengths, including its inclusion of multiple sites in different countries and a low risk of study biases, but there are also limitations.^41,42 First, the study duration was relatively short (i.e. ≤12 weeks). Second, because the appearance and weight of veverimer and placebo were not identical, certain site staff members had to be unblinded for dispensing the drug. These staff members did not have other responsibilities besides preparation and dispensing the study drug, but it is possible that other study team members and participants were able to differentiate veverimer from placebo based on the appearance. Third, the system used to automate randomization failed to stratify participants by screening eGFR as intended and this resulted in a higher mean eGFR in the treatment group (29.2 ml/min per 1.73m²) than the placebo group (27.8 ml/min per 1.73m²). Although the baseline serum bicarbonate levels were similar in both groups, it is possible that patients with higher eGFR were more likely to achieve a target serum bicarbonate level.⁴¹ Lastly, based on the pharmacology of veverimer,¹⁷ it should not lead to sodium retention as may occur with sodium bicarbonate. Patients with systolic blood pressure ≥170 mmHg or advanced heart failure were excluded from the 2 studies of veverimer. The inclusion of these patients in future studies would further address the potential benefit of vererimer compared with sodium bicarbonate in terms of sodium retention.

Ongoing long-term studies of veverimer

In patients with CKD and chronic metabolic acidosis, short-term studies of veverimer demonstrated its efficacy in increasing serum bicarbonate levels, which seems comparable to sodium bicarbonate therapy. According to the findings from a recent meta-analysis, sodium bicarbonate therapy increases serum bicarbonate level by 3.4 mEq/L (95% CI 1.9–4.9) in the studies with varied lengths of follow up (3 months to 5 years).²⁷ There were no serious adverse effects observed in the studies of veverimer. The most common treatment-related adverse events were diarrhea. Veverimer is not yet approved by the Food and Drug Administration.

To evaluate the long-term efficacy and safety of veverimer, there are 2 ongoing clinical studies. One is an extension of the phase 3 study, in which 196 participants who completed the study were randomized to receive either veverimer 6 g or placebo once daily on an outpatient basis for another 40 weeks.⁴³ The primary outcome is the incidence of adverse events leading to withdrawal of the medication and the secondary outcome is the change in bicarbonate level. Another study is a randomized, double-blind, placebo-controlled phase 3b study, in which 1,600 participants with eGFR of 20–40 ml/min per 1.73m² and serum bicarbonate of 12–20 mEq/L are randomized to veverimer (dose unclear) or placebo.⁴⁴ The average duration of follow up will be 3.5 years. The primary endpoint is the progression of CKD, defined by time to first occurrence of any event in the composite endpoint consisting of a confirmed ≥40% reduction in eGFR, end-stage renal disease and renal death. The secondary endpoints include time to end stage renal disease, physical function, cardiovascular mortality and hospitalization.

Conclusion

In patients with CKD and chronic metabolic acidosis, recent studies show that sodium bicarbonate therapy may improve vascular endothelial function and muscle mass and preserve renal function. Larger and longer clinical trials are needed to confirm these findings especially on the cardiovascular endpoints. Veverimer binds to hydrochloric acid in the gastrointestinal tract and increases serum bicarbonate levels. Veverimer is a potential new therapeutic option for treating chronic metabolic acidosis, especially for patients who have contraindications to sodium bicarbonate therapy. The effects of veverimer on clinical endpoints such as CKD progression, physical function and cardiovascular morbidity as well as its long-term safety still need to be determined. Future studies should also consider comparing the efficacy of veverimer with sodium bicarbonate, which is less costly, and to determine whether veverimer is superior to sodium bicarbonate in patients who cannot tolerate additional sodium load.

Key points.

• Sodium bicarbonate therapy may improve vascular endothelial function in patients with CKD and chronic metabolic acidosis, but larger and longer clinical trials are needed to confirm the finding.

• Sodium bicarbonate therapy may increase muscle mass and preserve renal function in patients with CKD and chronic metabolic acidosis.

• Short-term treatment with veverimer, which is a non-absorbable, hydrochloric acid binder, increases serum bicarbonate levels in patients with CKD and chronic metabolic acidosis.

• The effects of veverimer on clinical endpoints such as CKD progression, physical function and cardiovascular morbidity as well as its long-term safety are still need to be determined.