Study design and population
The DARE-ESKD-2 study (NCT05685394) is an ongoing randomized, phase 3, controlled, open-label trial aimed at assessing the cardiovascular effects of dapagliflozin vs. standard treatment in individuals with ESKD who are undergoing dialysis. The study protocol received ethical approval from the local ethics committee, and it complies with the principles outlined in the Declaration of Helsinki.11 Eligible participants are adults aged 18 years or older who have been on regular hemodialysis or peritoneal dialysis for at least three months prior to enrollment. Exclusion criteria encompass hypersensitivity to any components of the study drug, pregnancy, impaired liver function, recent use of SGLT2i, or experiencing acute coronary syndrome within the three months preceding randomization.
Clinical care protocol
The study protocol, outlined in Fig. 1, begins with patient referrals from local dialysis clinics to our research center, where undergo their initial medical assessment to determine eligibility. During this visit, a certified physician presents the informed consent form and conducts a thorough interview to gather medical history register, followed by a comprehensive physical examination. Then, participants are randomly assigned in a 1:1 ratio either dapagliflozin (10mg/day) plus standard treatment or standard treatment alone (control group) using an automated system.
Furthermore, peripheral blood samples are collected for biochemical analysis, and a 12-lead electrocardiogram is obtained. Blood pressure readings are taken in triplicate after 3 minutes of rest in a seated position and repeated after 1 minute of standing to assess orthostatic changes, using the Omron Hbp-1120 device (Omron Healthcare, Japan). Additionally, assessments through dual X-ray absorptiometry (DXA), bioimpedance, echocardiography, gait speed measurement, and six-minute walk test are performed during this visit.
Once the baseline evaluation is completed, patients in the dapagliflozin group receive the necessary pills for a 24-week treatment period, and all participants are thereupon contacted monthly to report outcomes and monitor medical adherence until study’s conclusion, at which baseline evaluations are repeated.
Echocardiography
Transthoracic echocardiogram is performed by experienced cardiologists blinded to patients allocation and comply with the latest recommendation from the American Society of Echocardiography.12 Heart ultrasound images are obtained by an equipment with three-dimensional (3D) technology (Philips EPIQ CVX ultrasound system, Philips Medical Systems, Andover, MA, USA) and a transducer for real time multiplanar volumetric analysis (X5-1 xMATRIX array transducer with PureWave crystal technology, 3040 elements, 5 − 1 MHz). Cardiac chambers diameters, volumes, indexed left ventricle (LV) mass estimation and LV ejection fraction are analyzed by both 2D and 3D methods (HeartModelA.I., Philips Medical Systems, Andover, MA, USA).
Complete echocardiographic analysis included appearance of the thoracic aorta, analysis of cardiac flows and presence of valvular heart disease. Diastolic function analysis followed the latest guidelines and included the E/e’ ratio, calculated from mitral inflow E velocity and mean tissue Doppler myocardial e’ velocity from mitral annulus (septal, lateral, anterior, and inferior) as an indirect estimation of the left atrium pressure. Global longitudinal strain by speckle tracking used a dedicated automated tool (Automated Cardiac Motion QuantificationA.I., aCMQA.I.,Philips Medical Systems, Andover, MA, USA).13,14
Body Composition
Body composition is evaluated using a DXA device (Lunar iDXA enCore version 13.60, GE Healthcare, USA) administered by an accredited anthropometrist who is blinded to participant allocation. Image acquisition and standardization of region of interest comply with the latest guidelines set forth by the International Society for Clinical Densitometry. The equipment undergoes weekly calibration for accuracy.15 This examination yields data on lean and fat mass as well as bone mineral density with the respective scores at specific anatomical sites including the femoral neck, Ward's triangle, trochanter, and lumbar spine.. In case where patient find it challenging to fit into the equipment, an image mirroring technique is employed.16
During the same assessment, we utilize bioimpedance analysis (Model-450, Biodynamics Corporation, Seattle, WA, USA) to obtain information on resistance, reactance, estimated basal metabolic rate, fat mass percentage, lean mass, body water, and phase angle. These measurements are analyzed inconsideration of body mass, age, and gender.17 As part of our comprehensive evaluation, we also obtain data on weight, height, and arm circumference according to validated protocols.18,19
Cardiopulmonary functional testing
The 6-minutes’ walk test (6MWT) adheres to the guidelines set forth by the American Thoracic Society.20 Briefly, participants are instructed to maintain their swiftest walking pace without running in a demarcated corridor for precisely 6 minutes, with supervision provided by a researcher responsible for registering the distance traversed.4 Readings for pulse oximetry, blood pressure, and heart rate are registered prior to commencing the test and immediately after it is terminated. Following the conclusion of the test, patients convey their perceived effort level using the Borg Scale.4 The 6MWT is contraindicated for patients with a resting heart rate exceeding 120 beats per minute, or a systolic or diastolic blood pressure exceeding 180mmHg and 100mmHg, respectively. Subsequently, patients are instructed to walk at their maximum pace within the same corridor, while the evaluator register the time taken to cover a precisely marked 4-meter distance. This evaluation is conducted three times, and the best time out of the three trials is utilized for analyzing 4-meter gait speed.
Additionally, handgrip strength is assessed in triplicate using a hand dynamometer (SH5001, Saehan Corporation, Dangjin-gun, South Korea), and the best result out of the three measurements (in Kg) is employed in our analysis.21
Kansas City Cardiomyopathy Questionnaire
The Kansas City Cardiomyopathy Questionnaire (KCCQ) comprises a 23 self-administered questions, addressing a wide range of physical, psychological, and social symptoms that may arise from heart failure.22 The KCCQ yields scores on a scale of 0 to 100 points, where higher scores correspond to a better quality of life.22 Study participants fill the Portuguese-validated KCCQ prior to randomization and at the study conclusion.23
Biochemical analysis
Peripheral blood samples are collected and dispatched to the clinical analysis laboratory for a comprehensive panel of tests. These tests include a complete blood count (flow cytometry and impedance – DXH 800), urea (urease with GLDH), creatinine (kinetic – IFCC), sodium, calcium, phosphate, and potassium (Selective Electrode), venous blood gases (Sensor-OMNI), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (kinetic – IFCC), and alkaline phosphatase (Abcam, Cambridge, UK).
To facilitate enzyme immunoassays, blood samples are collected and centrifuged at 3,500 rpm for 10 minutes. Plasma aliquots are cryopreserved in liquid nitrogen for subsequent measurements of N-terminal pro-B natriuretic peptide (NT-proBNP, Human pro-BNP Georgia, USA), fibroblast growth factor-23 (FGF-23; Abcam, Cambridge, UK), and parathyroid hormone (Sigma-Aldrich, San Luis, Missouri, EUA), α-Klotho (Quidel, San Diego, USA), and MILLIPLEX MAP Human Bone Magnetic Bead Panel - Bone Metabolism Multiplex Assay (Merck, Darmstadt, Germany). These quantitative measurements are performed in accordance with the manufacturer’s recommendations, and the absorbance is determined using a microplate reader (Biotek EPOCH 2).
Follow-up
Following randomization, participants receive monthly phone calls over a six-month period. During each contact, they are queried about various aspects, including changes in their dry weight, alterations in bowel and urinary habits, their overall well-being during daily activities, blood pressure measurements, occurrences of fractures, any medical procedures undergone, initiation of new treatments, surgeries, hospitalizations, infections, and clinical incidents. Additionally, participants in the dapagliflozin group are required to report the number of study drug pills taken in the past 30 days to track medication adherence, which is registered as a percentage.
Efficacy endpoints
The primary endpoint of our study is the between-groups differences in posttreatment changes in plasma levels of NT-proBNP. Secondary endpoints encompass the differences between groups in the changes of LV mass, EF, E/e’ ratio, KCCQ points, 6-min walk test distance, gait speed, lean to fat mass ratio, and handgrip strength.
In addition, an exploratory analysis will be conducted, in which participants with residual diuresis will be inquired about changes in their urinary output. Furthermore, the incidence of a composite outcome comprising cardiovascular death, hospitalization for heart failure, and stroke will be compared between the dapagliflozin and control groups. Changes in serum levels of bone metabolism markers, such as FGF-23 and a-Klotho, as well as on bone mineral density, will be compared between groups as an exploratory analysis.
Safety endpoints
For safety assessments, we are diligently monitoring adverse events at each visit, following the guidelines outlined in the Patient Reported Outcomes version of the Common Terminology Criteria for Adverse Events from the National Cancer Institute24,25. Safety Endpoints in this clinical trial encompass the following: (i) Time to the first occurrence of the adverse events (AE): (a) Liver injury, evaluated both overall and individually by causative factors (defined as ALT or AST levels ≥ 5x Upper Limit of Normal [ULN], or the combination of ALT or AST ≥ 3x ULN with bilirubin ≥ 2x ULN measured in the same blood sample); (b) Ketoacidosis, assessed both overall† and categorized by baseline diabetes status; (c) Lower limb amputations, considered overall† and differentiated by level (toe, forefoot, foot, below knee, or above knee); (ii) Time to the first occurrence of another AE relevant to the study's objective: (a) Bone fracture, examined both overall and categorized by site (long bones versus non-long bones) and etiology (distinguishing those resulting from high and low impact trauma, and other causes); (b) Symptomatic dehydration, defined by whether participants experience symptoms attributable to dehydration, such as feeling faint or fainting; (iii) Time to the first occurrence of hospitalization, categorized by specific causes according to the MedDRA Primary System Organ Class (SOC); (iv) Time to the first occurrence of Serious Adverse Events (SAEs), both overall† and separately, by Primary SOC category; (v) Discontinuation of study treatment, assessed overall and categorized by various causes, including SAEs, non-serious adverse events, and other reasons, using Primary SOC categories for SAEs and non-serious adverse events.
Power and sample size
Based on previous trials involving dapagliflozin, the sample size was meticulously calculated, considering an expected between-groups difference of 9% in the primary endpoint of the relative change of NT-proBNP. With a significance level (alpha). Set at 0.05 and a statistical power (beta) of 80%, the calculation indicated a requirement of 26 patients in each arm, totaling 52 participants. However, in anticipation of potential dropouts and with consideration for secondary outcomes, researchers opted for a more robust sample size of 80 patients. The calculations were performed using G*Power 3.1 Mac version (Heinrich-Heine-Universität, Germany).
Data management
Data management in our study relies on the utilization of the Research Electronic Data Capture tool (REDCap, Nashville, TN), which is a web-based and secure platform. REDCap serves the critical function of facilitating the auditing of data collection processes and the seamless export of data. This ensures the creation of de-identified datasets, which is a paramount for safeguarding the confidentiality of our study participants.26 The principal investigator assumes the pivotal role of compiling a comprehensive summary of examination results, which is the distributed to all participants involved in the study. Additionally, the principal investigator is responsible for delineating the specific roles of sub-investigators within the research team.
Statistical analysis
Unless specified otherwise, all analyses will entail an intention-to-treat comparison involving all randomized participants. The groups will be compared in terms of their differences from baseline using analysis of covariance (ANCOVA) or rank analysis of covariance (RANKOVA) according to the data distribution and considering baseline values and study arm as covariates. Continuous variables will be expressed as mean ± standard deviation (SD) for normally distributed, or as median (interquartile range) for non-normally distributed data. Categorical data will be presented as counts and percentages. We will employ Student’s t and Mann-Whitney tests to compare means and medians between groups, respectively, while categorical data will be assessed using the chi-square test. Continuous variables may undergo ranking or log-transformation as needed to achieve normality. Adjustments by covariates will be made when appropriate. A statistical significance will be defined as a p-value less than 0.05. The statistical analysis will be carried out using SPSS version 28.00 for Mac, and it will be performed by an accredited statistician.