Variability in response to albuminuria-lowering drugs: true or random?

Optimization of Albuminuria-Lowering Treatment in Diabetes by Crossover Rotation to Four Different Drug Classes: A Randomized Crossover Trial

OBJECTIVE

Renin-angiotensin system (RAS) inhibitors decrease the urinary albumin to creatinine ratio (UACR) but are ineffective in up to 40% of patients. We hypothesized that rotation through different drug classes overcomes RAS inhibitor resistance and tested this in a randomized crossover trial.

RESEARCH DESIGN AND METHODS

We assigned 26 adults with type 1 diabetes and 37 with type 2 diabetes and UACR between 30 and 500 mg/g and estimated glomerular filtration rate >45 mL/min/1.73 m2 to 4-week treatment periods with telmisartan 80 mg, empagliflozin 10 mg, linagliptin 5 mg, and baricitinib 2 mg in random order, separated by 4-week washout periods. Each participant was then re-exposed for 4 weeks to the drug that induced that individual's largest UACR reduction. Primary outcome was the difference in UACR response to the best-performing drug during the confirmation period versus UACR response to the other three drugs.

RESULTS

There was substantial variation in the best-performing drug. Telmisartan was best performing for 33 participants (52%), empagliflozin and linagliptin in 11 (17%), and baricitinib in 8 participants (13%). The individuals' best-performing drug changed UACR from baseline during the first and confirmatory exposures by a mean of -39.6% (95% CI -44.8, -33.8; P < 0.001) and -22.4% (95% CI -29.7, -12.5; P < 0.001), respectively. The Pearson correlation for first versus confirmatory exposure was 0.39 (P = 0.017). The mean change in UACR with the other three drugs was +1.6% (95% CI -4.3%, 8.0%; P = 0.593 versus baseline; difference versus individuals' best-performing drug at confirmation, 30.9% [95% CI 18.0, 45.3]; P < 0.001).

CONCLUSIONS

We demonstrated a large and reproducible variation in participants' responses to different UACR-lowering drug classes. These data support systematic rotation through different drug classes to overcome therapy resistance to RAS inhibition.

Up-Date on Diabetic Nephropathy

Diabetes is one of the leading causes of kidney disease. Diabetic kidney disease (DKD) is a major cause of end-stage kidney disease (ESKD) worldwide, and it is linked to an increase in cardiovascular (CV) risk. Diabetic nephropathy (DN) increases morbidity and mortality among people living with diabetes. Risk factors for DN are chronic hyperglycemia and high blood pressure; the renin-angiotensin-aldosterone system blockade improves glomerular function and CV risk in these patients. Recently, new antidiabetic drugs, including sodium-glucose transport protein 2 inhibitors and glucagon-like peptide-1 agonists, have demonstrated additional contribution in delaying the progression of kidney disease and enhancing CV outcomes. The therapeutic goal is regression of albuminuria, but an atypical form of non-proteinuric diabetic nephropathy (NP-DN) is also described. In this review, we provide a state-of-the-art evaluation of current treatment strategies and promising emerging treatments.

Impact of random variation in albuminuria and estimated glomerular filtration rate on patient enrolment and duration of clinical trials in nephrology

AIM

To test whether a screening approach with more flexible urinary albumin creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) thresholds would decrease screen failure rate without negatively impacting on the event rate and overall study duration.

METHODS

We performed a post-hoc analysis of the ALTITUDE trial. We selected participants randomized to placebo with a UACR of >300 mg/g and an eGFR between 30 mL/min/1.73 m² and 60 mL/min/1.73 m² at the first visit (pre-screening) for the trial. We then used less stringent lower UACR and higher eGFR thresholds for the following qualifying visit. For each scenario we calculated the number of eligible participants, the number of renal and cardiovascular endpoints, and the event rates. Based on this, we performed simulations for a future trial and estimated the duration of enrolment and total duration of this trial.

RESULTS

The base scenario consisted of 848 participants (median UACR 1239 mg/g; median eGFR 44 mL/min/1.73 m² ). Lowering the UACR and/or raising eGFR qualification thresholds increased the number of eligible participants, decreased screen failures and resulted in only a modest decrease in renal and cardiovascular event rates. For example, relaxing the UACR criterion from 300 mg/g to 210 mg/g at the qualifying visit, increased the number of eligible patients from 848 to 923, and increased the number of renal events from 117 to 122 events. The event rate showed a moderate decrease from 5.6 (4.6-6.7) events per 100 patient-years to 5.3 (4.4-6.4) events per 100 patient-years. In simulations, lowering the UACR and raising eGFR thresholds for inclusion accelerated patient enrolment and did not increase in the overall trial duration.

CONCLUSION

More flexible albuminuria and eGFR-based inclusion criteria, in participants who met the inclusion criteria of a trial based on pre-screening values prior to the clinical trial, decreases screen failure rates and accelerated patient enrolment leading to more efficient trial conduct without impacting the overall trial duration.

Biological variation in the serum and urine kidney injury markers of a healthy population measured within 24 hours

BACKGROUND AND AIMS

To explore the biological variation (BV) of kidney injury markers in serum and urine of healthy subjects within 24 hours to assist with interpretation of future studies using these biomarkers in the context of known BV.

MATERIALS AND METHODS

Serum and urine samples were collected every 4 hours (0, 4, 8, 12, 16 and 20 hours) from 31 healthy subjects within 24 hours and serum creatinine (s-Crea), serum β2-microglobin (s-β2MG), serum cystatin C (s-CYSC), serum neutrophil gelatinase-associated lipoprotein (s-NGAL), urine creatinine (u-Crea), urine β2-microglobin (u-β2MG), urine cystatin C (u-CYSC), urine neutrophil gelatinase-associated lipoprotein (u-NGAL) were measured. Outlier and variance homogeneity analyses were performed, followed by CV-ANOVA analysis on trend-corrected data (if relevant), and analytical (CV_A), within-subject (CV_I), and between-subject (CV_G) biological variation were calculated.

RESULTS

The concentration of kidney injury markers in male was higher than that in female, except for u-CYSC and u-NGAL. There were no significant difference in serum and urine kidney injury markers concentration at different time points. Serum CV_I was lower than urine CV_I, serum CV_G was higher than CV_I, and urine CV_G was lower than CV_I. The individual index (II) of serum kidney injury markers was less than 0.6, while the II of urinary kidney injury markers was more than 1.0.

CONCLUSIONS

This study provides new short-term BV data for kidney injury markers in healthy subjects within 24 hours, which are of great significance in explaining other AKI / CKD studies.

Precision Nephrology in Patients with Diabetes and Chronic Kidney Disease

Diabetes is the leading cause of kidney failure and specifically, diabetic kidney disease (DKD) occurs in up to 30% of all diabetic patients. Kidney disease attributed to diabetes is a major contributor to the global burden of the disease in terms of clinical and socio-economic impact, not only because of the risk of progression to End-Stage Kidney Disease (ESKD), but also because of the associated increase in cardiovascular (CV) risk. Despite the introduction of novel treatments that allow us to reduce the risk of future outcomes, a striking residual cardiorenal risk has been reported. This risk is explained by both the heterogeneity of DKD and the individual variability in response to nephroprotective treatments. Strategies that have been proposed to improve DKD patient care are to develop novel biomarkers that classify with greater accuracy patients with respect to their future risk (prognostic) and biomarkers that are able to predict the response to nephroprotective treatment (predictive). In this review, we summarize the principal prognostic biomarkers of type 1 and type 2 diabetes and the novel markers that help clinicians to individualize treatments and the basis of the characteristics that predict an optimal response.

OMICS in Chronic Kidney Disease: Focus on Prognosis and Prediction

Chronic kidney disease (CKD) patients are characterized by a high residual risk for cardiovascular (CV) events and CKD progression. This has prompted the implementation of new prognostic and predictive biomarkers with the aim of mitigating this risk. The ‘omics’ techniques, namely genomics, proteomics, metabolomics, and transcriptomics, are excellent candidates to provide a better understanding of pathophysiologic mechanisms of disease in CKD, to improve risk stratification of patients with respect to future cardiovascular events, and to identify CKD patients who are likely to respond to a treatment. Following such a strategy, a reliable risk of future events for a particular patient may be calculated and consequently the patient would also benefit from the best available treatment based on their risk profile. Moreover, a further step forward can be represented by the aggregation of multiple omics information by combining different techniques and/or different biological samples. This has already been shown to yield additional information by revealing with more accuracy the exact individual pathway of disease.

Early Response in Albuminuria and Long-Term Kidney Protection during Treatment with an Endothelin Receptor Antagonist: A Prespecified Analysis from the SONAR Trial

BACKGROUND

Whether early reduction in albuminuria with atrasentan treatment predicts its long-term kidney-protective effect is unknown.

METHODS

To assess the long-term effects on kidney outcomes of atrasentan versus placebo in the SONAR trial, we enrolled patients who had type 2 diabetes and CKD (stage 2-4) and a urinary albumin creatinine ratio (UACR) of 300-5000 mg/g; participants were receiving maximum tolerated renin-angiotensin system inhibition. After 6 weeks exposure to 0.75 mg/day atrasentan (enrichment period), participants were randomized (stratified by UACR response during enrichment, ranging from ≤60% to >0%) to continue atrasentan or transition to placebo. Primary kidney outcome was a composite of sustained serum creatinine doubling or ESKD.

RESULTS

UACR response to atrasentan during enrichment persisted throughout the double-blind treatment phase and predicted the primary kidney outcome, whereas UACR levels with placebo remained below pre-enrichment values in the two highest UACR response strata, and exceeded pre-enrichment values in the two lowest strata. As a result, early UACR response to atrasentan during enrichment was also associated with the primary kidney outcome during placebo. Accordingly, the predictive effect of early albuminuria changes during atrasentan was eliminated after placebo correction, leading to a consistent relative risk reduction for the primary kidney outcome with atrasentan compared with placebo, irrespective of the initial UACR response. The difference between atrasentan and placebo in UACR during double-blind treatment was also consistent across UACR response strata.

CONCLUSIONS

Our findings do not support UACR response as a causal predictor of atrasentan's treatment effect. However, the variable trajectory in UACR with placebo, aspects of the trial design, day-to-day variability in albuminuria, and potential long-lasting effects of atrasentan may have contributed.

The Role of Prognostic and Predictive Biomarkers for Assessing Cardiovascular Risk in Chronic Kidney Disease Patients

Chronic kidney disease (CKD) is currently defined as the presence of proteinuria and/or an eGFR < 60 mL/min/1.73m² on the basis of the renal diagnosis. The global dimension of CKD is relevant, since its prevalence and incidence have doubled in the past three decades worldwide. A major complication that occurs in CKD patients is the development of cardiovascular (CV) disease, being the incidence rate of fatal/nonfatal CV events similar to the rate of ESKD in CKD. Moreover, CKD is a multifactorial disease where multiple mechanisms contribute to the individual prognosis. The correct development of novel biomarkers of CV risk may help clinicians to ameliorate the management of CKD patients. Biomarkers of CV risk in CKD patients are classifiable as prognostic, which help to improve CV risk prediction regardless of treatment, and predictive, which allow the selection of individuals who are likely to respond to a specific treatment. Several prognostic (cystatin C, cardiac troponins, markers of inflammation, and fibrosis) and predictive (genes, metalloproteinases, and complex classifiers) biomarkers have been developed. Despite previous biomarkers providing information on the pathophysiological mechanisms of CV risk in CKD beyond proteinuria and eGFR, only a minority have been adopted in clinical use. This mainly depends on heterogeneous results and lack of validation of biomarkers. The purpose of this review is to present an update on the already assessed biomarkers of CV risk in CKD and examine the strategies for a correct development of biomarkers in clinical practice. Development of both predictive and prognostic biomarkers is an important task for nephrologists. Predictive biomarkers are useful for designing novel clinical trials (enrichment design) and for better understanding of the variability in response to the current available treatments for CV risk. Prognostic biomarkers could help to improve risk stratification and anticipate diagnosis of CV disease, such as heart failure and coronary heart disease.

Overcoming Compensatory Mechanisms toward Chronic Drug Administration to Ensure Long-Term, Sustainable Beneficial Effects

Chronic administration of drugs leads to the activation of compensatory mechanisms that may inhibit some of their activity and induce unwanted toxicity. These mechanisms are an obstacle for maintaining a sustainable effect for many chronic medications. Pathways that adapt to the burden induced by chronic drugs, whether or not related to the underlying disease, can lead to a partial or complete loss of effect. Variability characterizes many biological systems and manifests itself as large intra- and inter-individual differences in the response to drugs. Circadian rhythm-based chronotherapy is further associated with variability in responses noted among patients. This paper reviews current knowledge regarding the loss of effect of chronic medications and the range of variabilities that have been described in responses and loss of responses. Establishment of a personalized platform for overcoming these prohibitive mechanisms is presented as a model for ensuring long-term sustained medication effects. This novel platform implements personalized variability signatures and individualized circadian rhythms for preventing and opposing the prohibitive effect of the compensatory mechanisms induced by chronic drug administration.

Proteinuria and cholesterol reduction are independently associated with less renal function decline in statin-treated patients; a post hoc analysis of the PLANET trials

Background

Statins have shown multiple effects on different renal risk factors such as lowering of total cholesterol (TC) and lowering of urine protein:creatinine ratio (U_PCR). We assessed whether these effects of statins vary between individuals, the extent of discordance of treatment effects on both TC and U_PCR within an individual, and the association of responses in TC and U_PCR with estimated glomerular filtration rate (eGFR) decline.

Methods

The PLANET I and II (Renal effects of Rosuvastatin and Atorvastatin in Patients Who Have Progressive Renal Disease) trials examined effects of atorvastatin and rosuvastatin on proteinuria and renal function in patients with proteinuria. We post hoc analysed 471 therapy-adherent proteinuric patients from the two trials and assessed the individual variability in U_PCR and TC response from 0 to 14 weeks and whether these responses were predictive of eGFR decline during the subsequent 9 months of follow-up.

Results

U_PCR and TC response varied between individuals: mean U_PCR response was −1.3% (5th–95th percentile −59.9 to 141.8) and mean TC response was −93.9 mg/dL (−169.1 to −26.9). Out of 471 patients, 123 (26.1%) showed a response in U_PCR but not in TC, and 96 (20.4%) showed a response in TC but not in U_PCR. eGFR (mL/min/1.73 m²) did not decrease significantly from baseline in both U_PCR responders [0.4; 95% confidence interval (CI) −1.6 to 0.9; P = 0.54] and TC responders (0.3; 95% CI −1.8 to 1.1; P = 0.64), whereas U_PCR and TC non-responders showed a significant decline in eGFR from baseline (1.8; 95% CI 0.6–3.0; P = 0.004 and 1.7; 95% CI 0.5–2.9; P = 0.007, respectively). A lack of response in both parameters resulted in the fastest rate of eGFR decline (2.1; 95% CI 0.5–3.7; P = 0.01). These findings were not different for rosuvastatin or atorvastatin.

Conclusions

Statin-induced changes in cholesterol and proteinuria vary between individuals and do not run in parallel within an individual. The initial fall in cholesterol and proteinuria is independently associated with a reduction in eGFR decline. This highlights the importance of monitoring both cholesterol and proteinuria after initiating statin therapy.

The Association of Matrix Metalloproteinases with Chronic Kidney Disease and Peripheral Vascular Disease: A Light at the End of the Tunnel?

: Chronic Kidney Disease (CKD) represents a risk factor for fatal and nonfatal cardiovascular (CV) events, including peripheral vascular disease (PVD). This occurs because CKD encompasses several factors that lead to poor prognoses, mainly due to a reduction of the estimated glomerular filtration rate (eGFR), the presence of proteinuria, and the uremic inflammatory milieu. The matrix metalloproteinases (MMPs) are a group of zinc-containing endopeptidases implicated in extracellular matrix (ECM) remodeling, a systemic process in tissue homeostasis. MMPs play an important role in cell differentiation, angiogenesis, inflammation, and vascular damage. Our aim was to review the published evidence regarding the association between MMPs, PVD, and CKD to find possible common pathophysiological mechanisms. MMPs favor ECM deposition through the glomeruli, and start the shedding of cellular junctions and epithelial-mesenchymal transition in the renal tubules. MMP-2 and -9 have also been associated with the presence of systemic vascular damage, since they exert a pro-inflammatory and proatherosclerotic actions. An imbalance of MMPs was found in the context of PVD, where MMPs are predictors of poor prognoses in patients who underwent lower extremity revascularization. MMP circulating levels are increased in both conditions, i.e., that of CKD and PVD. A possible pathogenic link between these conditions is represented by the enhanced production of transforming growth factor-β that worsens vascular calcifications and atherosclerosis and the development of proteinuria in patients with increased levels of MMPs. Proteinuria has been recognized as a marker of systemic vascular damage, and this may explain in part the increase in CV risk that is manifest in patients with CKD and PVD. In conclusion, MMPs can be considered a useful tool by which to stratify CV risk in patients with CKD and PVD. Further studies are needed to investigate the causal-relationships between MMPs, CKD, and PVD, and to optimize their prognostic and predictive (in response to treatments) roles.

Unraveling Cardiovascular Risk in Renal Patients: A New Take on Old Tale

Chronic kidney disease (CKD), defined by an estimated glomerular filtration rate <60 ml/min/1.73 m² and/or an increase in urine protein excretion (i.e., albuminuria), is an important public health problem. Prevalence and incidence of CKD have risen by 87 and 89%, worldwide, over the last three decades. The onset of either albuminuria and eGFR reduction has found to predict higher cardiovascular (CV) risk, being this association strong, independent from traditional CV risk factors and reproducible across different setting of patients. Indeed, this relationship is present not only in high risk cohorts of CKD patients under regular nephrology care and in those with hypertension or type 2 diabetes, but also in general, otherwise healthy population. As underlying mechanisms of damage, it has hypothesized and partially proved that eGFR reduction and albuminuria can directly promote endothelial dysfunction, accelerate atherosclerosis and the deleterious effects of hypertension. Moreover, the predictive accuracy of risk prediction models was consistently improved when eGFR and albuminuria have been added to the traditional CV risk factors (i.e., Framingham risk score). These important findings led to consider CKD as an equivalent CV risk. Although it is hard to accept this definition in absence of additional reports from scientific Literature, a great effort has been done to reduce the CV risk in CKD patients. A large number of clinical trials have tested the effect of drugs on CV risk reduction. The targets used in these trials were different, including blood pressure, lipids, albuminuria, inflammation, and glucose. All these trials have determined an overall better control of CV risk, performed by clinicians. However, a non-negligible residual risk is still present and has been attributed to: (1) missed response to study treatment in a consistent portion of patients, (2) role of many CV risk factors in CKD patients not yet completely investigated. These combined observations provide a strong argument that kidney measures should be regularly included in individual prediction models for improving CV risk stratification. Further studies are needed to identify high risk patients and novel therapeutic targets to improve CV protection in CKD patients.

Efficacy of a novel inhibitor of vascular adhesion protein-1 in reducing albuminuria in patients with diabetic kidney disease (ALBUM): a randomised, placebo-controlled, phase 2 trial

BACKGROUND

Many patients with diabetic kidney disease have residual albuminuria and are at risk of disease progression. The ALBUM trial investigated the efficacy of a novel, orally active inhibitor of vascular adhesion protein-1, ASP8232, compared with placebo for reducing albuminuria in individuals with type 2 diabetes and chronic kidney disease.

METHODS

In this randomised, double-blind, placebo-controlled phase 2 trial, we randomly assigned individuals (aged 18-85 years) from 64 clinical sites in nine European countries to receive ASP8232 40 mg or placebo orally once daily for 12 weeks using a web-based randomisation schedule (block size 4), stratified by country. Eligible patients had a urinary albumin-to-creatinine ratio (UACR) of 200-3000 mg/g, an estimated glomerular filtration rate of at least 25 mL/min per 1·73 m² but lower than 75 mL/min per 1·73 m², HbA_1c less than 11·0% (97 mmol/mol), and stable treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and antidiabetic medication for 3 months or more. The primary endpoint was mean change from baseline to week 12 in log-transformed first morning void UACR, which was assessed in all patients who received at least one dose of study drug and had at least one post-baseline UACR measurement (full analysis set). Safety was assessed in all patients who received at least one dose of study drug. Participants and investigators were masked to treatment allocation. This trial is registered with ClinicalTrials.gov, number NCT02358096.

FINDINGS

125 participants were randomly assigned to receive ASP8232 (n=64) or placebo (n=61), of whom 120 (60 in each group) were included in the full analysis set; all participants were assessed for safety endpoints. At 12 weeks, UACR decreased by 17·7% (95% CI 5·0 to 28·6) in the ASP8232 group and increased by 2·3% (-11·4 to 18·1) in the placebo group; the placebo-adjusted difference between groups was -19·5% (95% CI -34·0 to -1·8; p=0·033). 39 (61%) patients in the ASP8232 group and 34 (56%) patients in the placebo group had a treatment-emergent adverse event, of which 16 in the ASP8232 group and four in the placebo group were drug-related. The most frequently reported adverse events that were possibly drug-related in the ASP8232 group were renal impairment (five patients) and decreased eGFR (three patients); in the placebo group, no single drug-related treatment-emergent adverse event was reported by more than one participant.

INTERPRETATION

ASP8232 is effective in reducing albuminuria in patients with diabetic kidney disease and is safe and well tolerated. These findings warrant further research to ascertain the effect of ASP8232 on delaying progression of diabetic kidney disease.

FUNDING

Astellas.

New clinical trial designs for establishing drug efficacy and safety in a precision medicine era

Despite advances in pharmacotherapy, diabetic kidney disease (DKD) remains associated with a high burden of micro- and macrovascular complications often leading to premature mortality. New therapies are highly desirable to mitigate the burden of this disease. However, there are a number of barriers that hamper drug development in DKD. These include, amongst others, the lengthy and complex clinical trials required to prove drug efficacy and safety, inefficiencies in clinical trial conduct, and the high costs associated with these development programs. In this review a number of aspects are discussed, aiming to identify opportunities to transform and innovate drug development for DKD. Many clinical trials in DKD, as well as in other areas, face difficulties in timely and efficient enrolment of participants. To address this issue a network of sites should be created that are continuously recruiting individuals with DKD and collecting crucial information that can be used to understand prognosis and prognostic factors, and more importantly to serve as a pool of participants for recruitment to randomized trials. Second, the current clinical endpoints are late events in the progression of DKD. Endpoints based on lesser declines in estimated glomerular filtration rate (eGFR) or changes in albuminuria can shorten follow-up and/or lead to smaller and cheaper trials. Enrichment by enrolling clinical trial populations based on biomarker profiles is another approach that may facilitate clinical trial efficiency and conduct. Biomarkers can be used to individualize treatment by targeting populations more likely to respond leading to smaller and more efficient trials. Finally, using new trial design such as basket, umbrella or more broadly platform trials to assess a number of therapies simultaneously offers the potential to transform the drug development process in DKD. There are a number of opportunities to transform development approaches for new therapies for DKD. Platform trials along with appropriate biomarker-based enrichment strategies offer the possibility to foster drug development in a precision medicine era.

Biological Variability of Estimated GFR and Albuminuria in CKD

RATIONALE & OBJECTIVE

Determining whether a change in estimated glomerular filtration rate (eGFR) or albuminuria is clinically significant requires knowledge of short-term within-person variability of the measurements, which few studies have addressed in the setting of chronic kidney disease.

STUDY DESIGN

Cross-sectional study with multiple collections over less than 4 weeks.

SETTING & PARTICIPANTS

Clinically stable outpatients with chronic kidney disease (N=50; mean age, 56.8 years; median eGFR, 40mL/min/1.73m²; median urinary albumin-creatinine ratio (UACR), 173mg/g).

EXPOSURE

Repeat measurements from serially collected samples across 3 study visits.

OUTCOMES

Measurements of urine albumin concentration (UAC), UACR, and plasma creatinine, cystatin C, β₂-microglobulin (B2M), and beta trace protein (BTP).

ANALYTICAL APPROACH

We calculated within-person coefficients of variation (CV_w) values and corresponding reference change positive and negative (RCV_pos and RCV_neg) values using log-transformed measurements.

RESULTS

Median CV_w (RCV_pos; RCV_neg) values of filtration markers were 5.4% (+16%; -14%) for serum creatinine, 4.1% (+12%; -11%) for cystatin C, 7.4% (+23%; -18%) for BTP, and 5.6% (+17%; -14%) for B2M. Results for albuminuria were 33.2% (+145%; -59%) for first-morning UAC, 50.6% (+276%; -73%) for random spot UAC, 32.5% (+141%; -58%) for first-morning UACR, and 29.7% (124%; -55%) for random spot UACR. CV_w values for filtration markers were comparable across the range of baseline eGFRs. CV_w values for UAC and UACR were comparable across the range of baseline albuminuria values.

LIMITATIONS

Small sample size limits the ability to detect differences in variability across markers. Participants were recruited and followed up in a clinical and not research setting, so some preanalytical factors could not be controlled.

CONCLUSIONS

eGFR markers appear to have relatively low short-term within-person variability, whereas variability in albuminuria appears to be high, making it difficult to distinguish random variability from meaningful biologic changes.

How to measure and monitor albuminuria in healthy toddlers?

OBJECTIVE

Urinary albumin:creatinine ratio (UACR) in first morning void (FMV) urine samples collected over three days is the recommended method for measuring and monitoring albuminuria in adults in the clinical setting. Such a guideline is not available for toddlers and young children. We tested several urine collection strategies for albuminuria measurement in toddlers in a prospective observational study.

MAIN OUTCOMES MEASURES

Both a FMV and a random daytime urine sample were collected on three consecutive days at week 0, 4, and 8 in toddlers aged 12-48 months. Intra-individual coefficients of variation (CV) of urinary albumin (UAC) and UACR were compared using only the first measurement and using all three measurements per time point. In addition, these were compared with published CV of adults.

RESULTS

A total of 80 toddlers (mean age 26.6 months, 53% male) were included. Intra-individual CV of FMV samples appeared lower than with random samples. The intra-individual CV in UAC or UACR was smaller using multiple compared to single samples. The lowest intra-individual CV was observed when UAC was measured in FMV over three consecutive days (38.3%). CV of UAC was similar to values published for adults. However, UACR CV was considerably higher in toddlers.

CONCLUSIONS

These data show that-in analogy with adult data-multiple first morning void urine samples should be preferred to single or random urine samples for establishing and monitoring albuminuria in toddlers. Further studies are needed to investigate why creatinine correction for differences in urine dilution is less effective in children.

Does SGLT2 inhibition with dapagliflozin overcome individual therapy resistance to RAAS inhibition?

Individual patients show a large variation in their response to renin-angiotensin-aldosteron system (RAAS) inhibition (RAASi), both in surrogates such as albuminuria and in hard renal outcomes. Sodium-glucose co-transporter 2 inhibitors (SGLT2) have been shown to lower albuminuria and to confer cardiovascular and, possibly, renal protection. To establish whether individual therapy resistance to RAASi can be overcome by adding an SGLT2 inhibitor, we assessed individual albuminuria responses in patients exposed to both RAASi and the SGLT2 inhibitor dapagliflozin. We used data from a randomized controlled cross-over trial designed to assess the albuminuria-lowering effect of 6-week treatment with dapagliflozin 10 mg/d. We extracted from the electronic medical records data on the albuminuria response upon initiation of RAASi before the trial period, and analysed individual albuminuria responses to RAASi and to dapagliflozin. We retrieved data on RAASi for 26 patients (age, 62 years [SD, 8]; female gender, 6 [23%]; 24-hour urinary albumin excretion, 521 [187-921] mg/24 h). The mean albuminuria-lowering response to RAASi was 26.5% (range, -76.1% to 135.1%). The addition of dapagliflozin res in a further reduction of 34.9%, (range, -83.9 to 94.2). Interestingly, the albuminuria response to RAASi significantly correlated with the response to dapagliflozin (Pearson correlation coefficient, 0.635 [95% CI, 0.328-0.821]; P < .001), indicating that patients who did not respond to RAASi also did not respond to dapagliflozin. We concluded that individual therapy resistance to RAASi cannot be overcome with the addition of a completely different class of drugs, SGLT2 inhibitors. These data suggest that the individual drug response is an intrinsic individual characteristic, possibly unrelated to the type of intervention, unless the mode of action of dapagliflozin on albuminuria is through the RAAS.

The albuminuria-lowering response to dapagliflozin is variable and reproducible among individual patients

AIMS

Albuminuria reduction is essential for renal and cardiovascular protection. We characterized the efficacy of dapagliflozin, a sodium-glucose co-transporter 2 inhibitor, on albuminuria. Secondly, we assessed whether the albuminuria-lowering effect varies among patients, and whether this variability in response is reproducible.

MATERIAL AND METHODS

A double-blind, randomized, placebo controlled crossover trial was conducted. Patients with type 2 diabetes and albumin:creatinine ratio > 100 mg/g on a stable dose of an angiotensin-converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) were enrolled. Patients were assigned to 6-week treatment periods with dapagliflozin 10 mg/d or placebo in random order, separated by 6-weeks wash-out periods. After the 2 treatment periods, half of the patients were re-exposed for 6 weeks to dapagliflozin 10 mg/d. Primary outcome was change in 24-hour urinary albumin excretion rate (24 h UAE). To assess reproducibility in individual albuminuria response, responses from the first and second exposure to dapagliflozin were correlated.

RESULTS

A total of 33 patients (age, 61 years; female gender, 24.2%; median 24 h UAE, 470 mg/24 h) completed the study. Dapagliflozin, as compared to placebo, reduced 24 h UAE by 36.2% (95% CI, 22.9-47.2; P  < .001). Systolic blood pressure fell by 5.2 mm Hg (95% CI, 0.5-10.0) and eGFR by 5.3 (95% CI, 2.7-8.0). All effects were reversible directly after treatment discontinuation. In a subgroup of 15 patients who were exposed twice to dapagliflozin, 24 h UAE responses showed a large variation among individuals: first exposure (range, -76% to +52%) and second exposure (-90% to +95%) and first and second individual response were significantly correlated (r = 0.69 [95% CI, 0.27-0.89]; P  < .004).

CONCLUSION

Dapagliflozin significantly reduces albuminuria when given as adjunct to ACEi or ARB. The albuminuria response to dapagliflozin markedly varies among patients. This variation is not a random phenomenon, but is reproducible upon re-exposure. These data support personalized therapy approaches to optimize diabetic kidney disease.

Variability in response to albuminuria-lowering drugs: true or random?

AIMS

Albuminuria-lowering drugs have shown different effect size in different individuals. Since urine albumin levels are known to vary considerably from day-to-day, we questioned whether the between-individual variability in albuminuria response after therapy initiation reflects a random variability or a true response variation to treatment. In addition, we questioned whether the response variability is drug dependent.

METHODS

To determine whether the response to treatment is random or a true drug response, we correlated in six clinical trials the change in albuminuria during placebo or active treatment (on-treatment) with the change in albuminuria during wash-out (off-treatment). If these responses correlate during active treatment, it suggests that at least part of the response variability can be attributed to drug response variability. We tested this for enalapril, losartan, aliskiren, atrasentan and paricalcitol.

RESULTS

No correlation between the on- and off-treatment albuminuria change was observed in the placebo arm of all clinical trials (R²  < 0.01). However, we observed significant associations between the on- and off-treatment response (R² 0.14 to 0.57; all P < 0.015) for different albuminuria lowering drugs. Additionally, the albuminuria responses strongly correlated when the same individual was re-exposed to the same drug at the same dose: lisinopril 10 mg day^-1 (R²  = 53%; P < 0.01), losartan 50 mg day^-1 (R²  = 63%; P < 0.01).

CONCLUSION

The degree of albuminuria lowering with antialbuminuric drugs varies between patients. This variability in response appears drug-class independent. Identifying which factors determine this initial short-term variation in drug response appears important since the degree of albuminuria lowering is related to subsequent long-term renoprotection.