Efficacy and safety of an innovative prolonged-release combination drug in patients with distal renal tubular acidosis: an open-label comparative trial versus standard of care treatments

Cystinuria in children: diagnosis and treatment

PURPOSE

Cystinuria is the predominant hereditary factor leading to kidney stone formation in the pediatric population. The aim of this manuscript is to provide an overview of cystinuria in children.

METHODS

The authors performed a literature review on studies regarding cystinuria in children. A narrative synthesis for analysis of the studies was used.

RESULTS

Cystine is a homodimeric amino acid formed by the disulfide bonding of two cysteine molecules. The problem with this autosomal recessive condition arises from a malfunction in the process of reabsorption. Cystine filtered from the renal glomerulus cannot be reabsorbed from the proximal tubules. Therefore, due to its extremely low solubility at normal urine pH, it precipitates and causes stone formation. Recurrent stone formation is the most prominent clinical presentation of cystinuria. The patients usually present with a renal colic episode with concomitant nausea and hematuria. The aim of medical treatment is to maintain the solubility of cystine in urine. The main strategies are to increase urine volume and urinary pH. Potassium citrate or potassium bicarbonate can be used to raise the pH of the urine to 7.5 to increase cystine solubility. If the treatment with alkalinization and higher urine output fails, cystine binding agents such as tiopronin and D-penicillamine can be added to the treatment. Surgical management of pediatric patients with cystine stones is similar to that in the adult population. However, cystine stones can be resistant to ESWL. Retrograde ureteroscopy with semirigid and flexible instruments is a good option for ureteral stones and also for renal stones less than 20 mm in diameter. The golden standard option for high-volume stones larger than 20 mm in diameter is percutaneous nephrolithotomy (PCNL).

CONCLUSIONS

Cystinuria is the primary hereditary factor contributing to the formation of kidney stones throughout childhood. It is a genetic disorder that typically manifests as recurrent stone formations. The aim of the treatment of genetically caused pediatric stone diseases is to prevent stone formation with medical treatments, remove existing stones through surgical treatments, and mitigate the risk of developing chronic kidney disease in the future.

Primary renal tubular acidosis during pregnancy, what about the perinatal prognosis? A case report and literature review

Renal tubular acidosis (RTA) is a group of disorders caused by tubular defects leading to defective reabsorption of bicarbonate (HCO3-) and/or secretion of protons (H+). It is known that pregnancy can induce or worsen some forms of RTA. To date, no systematic data exist on the course of pregnancy in hereditary RTA-affected mothers, nor on the outcome of both mothers and children. A 35-year-old female patient attends her routine obstetric follow-up consultation at 32-weeks' pregnancy. From the 6th week of gestation, she has been complaining of general malaise, accompanied by paraesthesia in both hands. She is known to have renal tubular acidosis type 1, carrying a mutation in the SLC4A1 gene encoding for the bicarbonate-chloride exchanger located in the alpha-intercalated cell of the renal collecting tubule. At week 32, serum bicarbonate levels appeared to be 11mEq/l. The patient was hospitalised and treated with intravenous sodium bicarbonate and potassium chloride. After 5 days, the symptoms resolved, and her bicarbonate level had normalised. A healthy infant was born with a normal Apgar score. Carriage of the same mutation was found in the child at 16 months. Our literature study shows that 12 of the 13 reported infants born from a mother with primary RTA were healthy at delivery. One neonate revealed signs of hyperparathyroidism at day 2, but those signs resolved at 1 month of age. RTA during pregnancy is often associated with decompensation and worsening of acidosis. More attention should be paid to patients with RTA suffering from hyperemesis gravidas, in particular regarding therapy adherence. Our literature review focusses on foetal prognosis, which seems to be favourable in most of the reported pregnancies.

[What is confirmed in the treatment of metabolic acidosis in chronic kidney disease?]

Precise regulation of the acid-base balance is essential for the functioning of various organs and physiological processes. Acid retention and metabolic acidosis (MA) are frequent complications of chronic kidney disease (CKD) and can also occur following kidney transplantation. In addition to dietary modifications, pharmacological interventions, most notably sodium bicarbonate, are employed to correct MA. While several studies have reported a beneficial effect of MA correction on the progression of CKD, the results remain inconsistent and the magnitude of the treatment effect may be limited. Importantly, no beneficial effect on graft function has been demonstrated after kidney transplantation. The MA is associated with impaired bone quality and although alkali treatment has generally shown positive effects on markers of bone metabolism, consistent changes in bone density have not been observed. Additionally, MA is linked to an increased incidence of cardiovascular events but so far there is a lack of interventional studies with definitive cardiovascular endpoints. Sodium bicarbonate may lead to sodium retention, potentially increasing blood pressure, although the data on this are inconclusive. One interventional study with notable limitations reported a positive effect of alkali treatment on mortality. Correction of MA has been suggested to positively impact protein and muscle catabolism, although no improvement in physical performance was observed in a geriatric population. Limited studies exist on the endocrinological effects of alkali treatment but these indicate a favorable impact on glucose metabolism and potential benefits for thyroid function in predialysis CKD patients. Given the overall low to moderate level of evidence supporting the benefits of alkali treatment, the current guidelines from Kidney Disease: Improving Global Outcomes (KDIGO) propose alkali treatment to prevent serum bicarbonate levels < 18 mmol/l (prior < 22 mmol/l) in adults and the resulting complications.

Recent Developments in the Treatment of Pediatric Distal Renal Tubular Acidosis

Distal renal tubular acidosis (dRTA) is characterized by a primary defect in proton secretion by α-intercalated cells of the collecting duct, leading to impaired urine acidification and resulting in metabolic acidosis, hypokalemia, and hypercalciuria. Inherited forms of dRTA are currently associated with variants in five genes (SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, and WDR72), each being associated with specific extra-renal manifestations. Acquired forms can result from autoimmune diseases or drug side effects. Classical complications include nephrolithiasis, nephrocalcinosis, reduced glomerular filtration rate (GFR), bone demineralization, and growth failure. Treatment focuses on correcting the acid-base imbalance through alkali supplementation (potassium, sodium, or magnesium bicarbonate or citrate) to reduce renal disease progression and promote normal growth and mineralization. Traditional treatments (alkali and potassium supplementation) often suffer from poor adherence due to frequent day and night administrations, gastrointestinal discomfort, and unpleasant taste. A novel investigational drug, ADV7103, which contains potassium citrate and potassium bicarbonate in an extended-release formulation, has recently been approved by the European Medicine Agency (EMA) for dRTA. Recent studies support its use as a first-line treatment, given its efficacy and safety profile.

Primary Distal Renal Tubular Acidosis: Toward an Optimal Correction of Metabolic Acidosis

The term classic, type 1 renal tubular acidosis or primary distal renal tubular acidosis is used to designate patients with impaired ability to excrete acid normally in the urine as a result of tubular transport defects involving type A intercalated cells in the collecting duct. The clinical phenotype is largely characterized by the complications of chronic metabolic acidosis (MA): stunted growth, bone abnormalities, and nephrocalcinosis and nephrolithiasis that develop as the consequence of hypercalciuria and hypocitraturia. All these manifestations are preventable with early and sustained correction of MA with alkali therapy. The optimal target for plasma bicarbonate should be as close as possible to the range considered normal by current standards (between 23 and 28 mEq/L.). Most of the benefits of alkali therapy are tangible early in the course of the disease in childhood, but life-long treatment is required to prevent the vast array of complications attributable to chronic MA.

Renal calcification in children with renal tubular acidosis: What a paediatrician ‎should ‎know‎

Renal tubular acidosis (RTA) can lead to renal calcification in children, which can cause various complications and impair renal function. This review provides pediatricians with a comprehensive understanding of the relationship between RTA and renal calcification, highlighting essential aspects for clinical management. The article analyzed relevant studies to explore the prevalence, risk factors, underlying mechanisms, and clinical implications of renal calcification in children with RTA. Results show that distal RTA (type 1) is particularly associated with nephrocalcinosis, which presents a higher risk of renal calcification. However, there are limitations to the existing literature, including a small number of studies, heterogeneity in methodologies, and potential publication bias. Longitudinal data and control groups are also lacking, which limits our understanding of long-term outcomes and optimal management strategies for children with RTA and renal calcification. Pediatricians play a crucial role in the early diagnosis and management of RTA to mitigate the risk of renal calcification and associated complications. In addition, alkaline therapy remains a cornerstone in the treatment of RTA, aimed at correcting the acid-base imbalance and reducing the formation of kidney stones. Therefore, early diagnosis and appropriate therapeutic interventions are paramount in preventing and managing renal calcification to preserve renal function and improve long-term outcomes for affected children. Further research with larger sample sizes and rigorous methodologies is needed to optimize the clinical approach to renal calcification in the context of RTA in the pediatric population.

Pediatric renal lithiasis in Spain: research, diagnostic and therapeutic challenges, and perspectives

Incidence and prevalence of urolithiasis is apparently increasing worldwide, also among children and adolescents. Nevertheless, robust data have only been obtained in a few countries. In Spain, a voluntary Registry for Pediatric Renal Lithiasis has been active since 2015. Irregular participation limits its applicability, as well as its limitation to patients with a stone available for morphocompositional study, to obtain data about incidence and prevalence. On the other hand, findings about typology of stones and clinical and analytical characteristics of these subjects have been communicated in several meetings. Other valuable efforts in this field are the elaboration of guidelines for the collection and processing of urine samples for the study of urolithiasis in pediatric patients with the consensus of the Spanish Society for Pediatric Nephrology (AENP) as well as the Spanish Society for Laboratory Medicine (SEQC), the collaborative network RenalTube for the diagnosis of primary tubulopathies and the registry of patients with Primary Hyperoxaluria (OxalSpain). In many hospitals from the public healthcare system, pediatric nephrologists are the specialists in charge of the management of children with kidney stones, but there is no formal regulation on this competence. Other specialists, such as urologists, pediatric surgeons or pediatric urologists, in many cases do not offer a complete insight into the etiopathogenic mechanisms and the consequent medical treatment. Access to medication according to standards of treatment is warranted, provided a correct diagnosis is achieved, but criteria for the reimbursement of certain therapies, such as RNAi drugs for primary hyperoxaluria, are arguable.

2022 Recommendations of the AFU Lithiasis Committee: Medical management - from diagnosis to treatment

The morphological-compositional analysis of urinary stones allows distinguishing schematically several situations: dietary, digestive, metabolic/hormonal, infectious and genetic problems. Blood and urine testing are recommended in the first instance to identify risk factors of urinary stone disease in order to avoid recurrence or progression. The other objective is to detect a potential underlying pathology associated with high risk of urinary stone disease (e.g. primary hyperparathyroidism, primary or enteric hyperoxaluria, cystinuria, distal renal tubular acidosis) that may require specific management. Lifestyle-diet measures are the basis of the management of all stone types, but pharmacological treatments may be required. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendation (CPR) method and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis) [EAU 2022] and their adaptability to the French context.

Bone mineral density and growth changes in patients with distal renal tubular acidosis after two-years treatment with a new alkalizing drug (ADV7103)

BACKGROUND AND OBJECTIVES

ADV7103 is a new prolonged-release treatment for distal renal tubular acidosis (dRTA), containing potassium citrate and potassium bicarbonate. Since acidosis may affect bone mineral contents, the effects of ADV7103 on bone mineral density (BMD) and growth in patients with dRTA over 24 months were evaluated.

PATIENTS AND METHODS

Thirty patients (24 paediatric patients and 6 adults) were included in an open-label extension study after a phase II/III trial. BMD, measured by densitometry, was assessed at baseline and at 24 months. Growth was evaluated throughout the study. Plasma bicarbonate, parathyroid hormone, 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, bone alkaline phosphatase, calciuria and citraturia, were also determined. Safety and treatment compliance were evaluated as well.

RESULTS

After 24 months of treatment with ADV7103, mean spine BMD z-score values significantly increased as compared with baseline (p=0.024). In adults, spine and whole-body densitometry z-scores showed a significant correlation with plasma bicarbonate levels (rS=0.82 and rS=0.97, respectively, p<0.005). There was an increase>0.5 units in z-scores for height and weight in 18% and 36% of the paediatric patients, respectively. With treatment, plasma bicarbonate concentration and calciuria at the different visits were normal in 69-86% and 93-96% patients, respectively. Only nine treatment-related gastrointestinal AEs of mild/moderate severity, were reported in five patients.

CONCLUSIONS

Two years of ADV7103 treatment improved growth and increased spine BMD. These results suggest that control of acidosis by ADV7103 treatment improves bone parameters.

The pathophysiology of distal renal tubular acidosis

The kidneys have a central role in the control of acid-base homeostasis owing to bicarbonate reabsorption and production of ammonia and ammonium in the proximal tubule and active acid secretion along the collecting duct. Impaired acid excretion by the collecting duct system causes distal renal tubular acidosis (dRTA), which is characterized by the failure to acidify urine below pH 5.5. This defect originates from reduced function of acid-secretory type A intercalated cells. Inherited forms of dRTA are caused by variants in SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, WDR72 and probably in other genes that are yet to be discovered. Inheritance of dRTA follows autosomal-dominant and -recessive patterns. Acquired forms of dRTA are caused by various types of autoimmune diseases or adverse effects of some drugs. Incomplete dRTA is frequently found in patients with and without kidney stone disease. These patients fail to appropriately acidify their urine when challenged, suggesting that incomplete dRTA may represent an intermediate state in the spectrum of the ability to excrete acids. Unrecognized or insufficiently treated dRTA can cause rickets and failure to thrive in children, osteomalacia in adults, nephrolithiasis and nephrocalcinosis. Electrolyte disorders are also often present and poorly controlled dRTA can increase the risk of developing chronic kidney disease.

Pediatric Chronic Kidney Disease

Chronic kidney disease (CKD) in children has a significant impact on morbidity, mortality, and quality of life. The degree of renal dysfunction should be calculated using pediatric-specific formulas and the degree of CKD staged; this allows for appropriate dosing of medications based on renal function and monitoring for progression and comorbid conditions including metabolic acidosis, bone disease, anemia, cardiovascular complications, malnutrition and electrolyte abnormalities, growth failure, and psychosocial issues. Treatment strategies include treating the underlying disease and using general renal protective measures. Effective management of these complex issues requires a specialized multidisciplinary team approach.

Lived experiences of patients with distal renal tubular acidosis treated with ADV7103 and of their caregivers: a qualitative study

Background

Consequences of distal renal tubular acidosis (dRTA) on growth, bone and kidney, sometimes associated with hearing loss, may significantly affect quality of life (QoL). This descriptive qualitative study explores QoL linked to dRTA and gathers the impressions of patients with this rare disease (and caregivers) 5 years after enrolment in a clinical study, during which patients were treated with ADV7103, a prolonged-release granule formulation combining potassium citrate and potassium bicarbonate. Semi-structured, one-hour interviews with 6 adult and 13 paediatric patients with a confirmed diagnosis of dRTA and with parents of paediatric patients were performed using an interview guide. Qualitative analysis of anonymized interview transcripts based on grounded theory was conducted.

Results

The main QoL domains impacted by dRTA and its treatment were education/work, social/family life, and emotional and physical well-being. ADV7103 (administered twice daily) was compared with the standard of care (SoC) taken before study entry (more than twice daily). Patients/parents reported that switching from previous SoC to ADV7103 had changed their lives:

Difficulties at school due to burdensome administrative issues and need to explain disease and treatment affecting all families of paediatric patients (n = 13) disappeared, facilitating parents who had stopped working (to deal with their child’s treatment) to return to work,

Family functioning was improved (n = 18), as travel and holidays became easier to organise and patients/parents stopped thinking about managing treatment daily/nightly, reducing tension in the family or couple,

The emotional burden of disease perceived was relieved (n = 12) in the absence of treatment-related invasive questions from others,

Gastro-intestinal adverse events and taste problems improved with ADV7103 (n = 18) and better compliance led to milder physical impacts and less need to be hospitalised.

The mean satisfaction score with ADV7103 compared to SoC was 9 out of 10 (10 = very satisfied). ADV7103 exceeded or met the expectations of 14 out of 17 patients that commented on that.

Conclusions

Qualitative interviews show that dRTA and its treatment have a significant impact on QoL of patients and parents and that ADV7103 helps improve daily-life and reduces treatment burden, resulting in greater overall satisfaction of the patients and their families.

Trial registration EU Clinical Trials Register, EudraCT 2013-003828-36 on the 3rd of September 2013.

Distal renal tubular acidosis: a systematic approach from diagnosis to treatment

Renal tubular acidosis (RTA) comprises a group of disorders in which excretion of hydrogen ions or reabsorption of filtered HCO₃ is impaired, leading to chronic metabolic acidosis with normal anion gap. In the current review, the focus is placed on the most common type of RTA, Type 1 RTA or Distal RTA (dRTA), which is a rare chronic genetic disorder characterized by an inability of the distal nephron to secrete hydrogen ions in the presence of metabolic acidosis. Over the years, knowledge of the molecular mechanisms behind acid secretion has improved, thereby greatly helping the diagnosis of dRTA. The primary or inherited form of dRTA is mostly diagnosed in infancy, childhood, or young adulthood, while the acquired secondary form, as a consequence of other disorders or medications, can happen at any age, although it is more commonly seen in adults. dRTA is not as “benign” as previously assumed, and can have several, highly variable long-term consequences. The present review indeed reports and summarizes both clinical symptoms and diagnosis, long-term outcomes, genetic inheritance, epidemiology and current treatment options, with the aim of shedding more light onto this rare disorder. Being a chronic condition, dRTA also deserves attention in the transition between pediatric and adult nephrology care, and as a rare disease it has a place in the European and Italian rare nephrological diseases network.

Safety, efficacy, and acceptability of ADV7103 during 24 months of treatment: an open-label study in pediatric and adult patients with distal renal tubular acidosis

BACKGROUND

A new prolonged-release formulation of potassium citrate and potassium bicarbonate, ADV7103, has been shown to improve metabolic control, palatability, and gastrointestinal safety in patients with distal renal tubular acidosis (dRTA) when compared to standard of care (SoC) treatments. The present work evaluates safety and efficacy of ADV7103 during 24 months.

METHODS

Thirty pediatric and adult patients were included in an open-label extension study after a phase II/III trial. Safety and tolerability were assessed. Plasma bicarbonate and potassium levels, as well as urine parameters, were evaluated over time. Acceptability, adherence, and quality of life were also assessed. The evolution of clinical consequences of dRTA in the cohort was explored.

RESULTS

There were 104 adverse events (AEs) reported, but only 9 gastrointestinal events observed in five patients (17%) were considered to be related to ADV7103 treatment. There were no AEs leading to treatment discontinuation. Plasma bicarbonate and potassium levels were in the normal ranges at the different visits, respectively, in 69-86% and 83-93% of patients. Overall adherence rates were ≥ 75% throughout the whole study in 79% patients. An average improvement of quality of life of 89% was reported at 24 months of study.

CONCLUSIONS

Common AEs concerned metabolism and gastrointestinal disorders; the former being related to the disease. Less than half of the gastrointestinal AEs were related to ADV7103 treatment and they were mostly mild in severity. Metabolic parameters were maintained in the normal ranges in most patients. Patient satisfaction was high and adherence to treatment was good and remained stable.

TRIAL REGISTRATION NUMBER

Registered as EudraCT 2013-003828-36 on the 3rd of September 2013.