StOPping Hypertension and imprOving Children's Lives After KidnEy TranSplantation
Phase: NA
Conditions: Arterial Hypertension, Kidney Transplant; Complications
Sponsor: Hannover Medical School

 
SOPHOCLES 
 
StOPping Hypertension and imprOving Children's Lives after 
KidnEy TranSplantation 
 
Studie zur Verbesserung der Herz-Kreislauf-Gesundheit nach 
Nierentransplantation im Kindesalter durch intensivierte 
Therapie des Blutdrucks 
 
 
 
Study Protocol 
 
Version 1.1, 5.6.2024 

 
SOPHOCLES - StOPping Hypertension and imprOving Children's Lives after KidnEy TranSplantation 
 
SOPHOCLES Study protocol v1.1, 5.6.2024 
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Table of Contents 
 
1. 
Summary.......................................................................................................................................... 3 
2. 
Responsibilities ................................................................................................................................ 3 
3. 
Scientific Background ...................................................................................................................... 3 
4. 
Aim of the study .............................................................................................................................. 5 
5. 
Outcome parameter ........................................................................................................................ 5 
6. 
Design of the Trial............................................................................................................................ 6 
7. 
Study Population ............................................................................................................................. 6 
7.1. 
Inclusion and exclusion criteria ............................................................................................. 6 
7.2. 
Patient numbers .................................................................................................................... 6 
7.3. 
Patient recruitment ............................................................................................................... 6 
8. 
Study Procedures............................................................................................................................. 7 
8.1. 
Informed consent .................................................................................................................. 7 
8.2. 
Study procedures .................................................................................................................. 7 
8.3. 
Investigational plan, assessment of endpoints ..................................................................... 7 
8.4. 
Study timeline, study duration .............................................................................................. 8 
8.5. 
Adherence / Rate of Loss to Follow-Up ................................................................................. 9 
9. 
Methods .......................................................................................................................................... 9 
9.1. 
Measurement of Cardiovascular Endpoints .......................................................................... 9 
9.2. 
Blood samples ....................................................................................................................... 9 
10. Statistical analysis .......................................................................................................................... 10 
10.1. Sample size calculation ........................................................................................................ 10 
10.2. Primary analysis ................................................................................................................... 10 
10.3. Secondary and exploratory analysis .................................................................................... 11 
10.4. Measures against Bias ......................................................................................................... 11 
11. Stopping Rules ............................................................................................................................... 11 
12. Risk-benefit assessment ................................................................................................................ 12 
13. Data Security ................................................................................................................................. 12 
14. Biobanking ..................................................................................................................................... 13 
15. Insurance ....................................................................................................................................... 13 
16. Publication rules ............................................................................................................................ 13 
17. References ..................................................................................................................................... 14 
 
 
 

 
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1. 
Summary 
Cardiovascular (CV) disease is a major morbidity in children after kidney transplantation (KTx), 
limiting life expectancy and impairing graft function. Arterial hypertension (AH) is the 
dominant CV risk factor, and highly abundant in this patient group. AH can cause left 
ventricular hypertrophy (LVH), which is predictive of CV death. LVH can be non-invasively 
assessed by measuring left ventricular mass index (LVMI). Analyses of observational data 
showed that blood pressure (BP) levels <75th percentile (pct) were associated with a 
significant reduction of LVMI. Guidelines give BP goals for children with chronic kidney disease 
(CKD). No guidelines, however, exist on the treatment of AH in pediatric KTx patients. In the 
proposed multicenter, randomized, parallel group trial with blinded endpoint evaluation we 
aim to assess n=500 pediatric patients >12 months after KTx at several KTx centers. Patients 
will be randomly assigned 1:1 to an intensified BP management group (BP target ≤60th pct) 
and a standard BP management group (BP target <90th pct). The primary endpoint is LVMI 
after 24 months. Secondary endpoints are estimated glomerular filtration rate (eGFR), pulse 
wave velocity (PWV) and intima media thickness (IMT) after 24 months. BP control will be 
guaranteed for both groups through BP telemonitoring, which will be transmitted in real time 
to the treating physician and the trial’s centralized BP office. By defining the adequate BP goal, 
the results of the proposed study will have direct implications for the care of children after 
KTx. The results will define an important element of post-KTx care and help to lower CV 
morbidity and subsequently CV mortality of pediatric KTx patients. 
2. 
Responsibilities 
Principal investigator:  Anette Melk, MD PhD 
Dept. of Pediatric Kidney, Liver, and Metabolic Diseases 
Hannover Medical School (MHH) 
Carl-Neuberg-Str. 1, 30625 Hannover 
Email: melk.anette@mh-hannover.de 
Statistician: 
Anika Großhennig, PhD 
Inst. of Biostatistics, MHH 
Carl-Neuberg-Str. 1, 30625 Hannover 
Central laboratory: 
Synlab Heidelberg 
Wasserturmstraße 71, 69214 Eppelheim 
Biobanking:  
Hannover Unified Biobank (HUB) 
Feodor-Lynen-Str.15, 30625 Hannover 
Funding: 
The study is funded by the DFG clinical trials program.  
Förderkennzeichen: ME 3696/6-1 
Registration: 
The study will be registered at ClinicalTrials.gov.  
3. 
Scientific Background 
Life expectancy in children with chronic kidney disease (CKD) after KTx has improved steadily1. 
Therefore, factors affecting long-term health, especially cardiovascular (CV) disease, carry 
increased relevance. CV morbidity is caused by a variety of risk factors. Of those, arterial 
hypertension (AH) is of particular importance, as it is strongly correlated with CV organ 
damage2, 3. CV events are among the most common causes of death in pediatric KTx 

 
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recipients4-6. Registry studies demonstrated a high prevalence of AH in pediatric KTx 
recipients7, 8 with more than 70% requiring antihypertensive medication9 and more than one 
third showing actual BP levels higher than the 95th percentile (pct)8. Our longitudinal analysis 
from the Cooperative European Pediatric Renal Transplant Initiative (CERTAIN) Registry of 336 
pediatric KTx recipients showed a prevalence of AH of 84% at discharge after KTx that declined 
only slightly to 77% after three years of follow-up8. We extended this finding, demonstrating 
sharply increased odds for AH for patients after pediatric KTx when compared to matched 
healthy children in a case-control study10. Long-term data report AH in more than 60% of 
pediatric KTx recipients after 10 years11. Several studies demonstrated the negative impact of 
AH on CV health and transplant survival in children after KTx12, 13.  
Left ventricular hypertrophy (LVH) is the most prominent manifestation of CV organ damage 
as a result of AH14. LVH is associated with death due to major CV events15. It affects about 40% 
of children one year after KTx16, 17. We have previously shown that the left-ventricular mass 
index (LVMI), an echocardiographic parameter to quantify LVH, increases in the early course 
after pre-emptive KTx and is mainly determined by BP and not by the mode of kidney 
replacement therapy18. LVH is a strong predictor of CV morbidity and mortality19-22, therefore 
measurement of left ventricular mass is a cornerstone of CV risk assessment14, 23.  
In children with CKD not yet requiring kidney replacement therapy, we have shown in the 
randomized controlled ESCAPE trial that intensified BP control using angiotensin-converting-
enzyme (ACE) inhibition reduces CKD progression24. This pivotal study has led to the 
implementation of BP goals for patients prior to kidney replacement therapy. However, 
currently no specific recommendations or guidelines exist on BP management in pediatric 
patients after KTx that are based on prospective data. To discern the effect of different BP 
levels and thereby the importance of BP control on LVH in KTx patients we analyzed long-term 
follow up data from the 4C-T study25, a sub-study of the 4C study (www.4c-study.eu)26, which 
prospectively assessed CV morbidity in children prior to and after KTx. We analyzed LVMI 
depending on blood pressure (BP) control in 94 pediatric KTx recipients. The cumulative 
systolic/diastolic BP exposure was calculated as time-averaged area under the curve and 
categorized according to pct ranges (≤50th, >50th-≤75th, >75th-≤90th, >90th pct). We show that 
a cumulative exposure to systolic BP values ≤75th pct is associated with lower LVMI: Compared 
to patients with a cumulative systolic BP exposure >90th pct, a significant LVMI reduction 
of -5.24g/m2.16 is seen in patients exposed to systolic BP between 50th to ≤75th pct (p=0.007). 
A similar tendency is observed in those exposed to ≤50th pct (ß=-3.70 g/m2.16; p=0.067), while 
no LVMI reduction is found in patients with cumulative systolic BP exposure between 75th to 
≤90th pct. The cumulative exposure to lower diastolic BP levels was also associated with lower 
LVMI with no large differences in the magnitude of the effect on LVMI across the three strata. 
Patients exposed to systolic BP ≤50th or between 50th to ≤75th pct had a significant risk 
reduction of 79% or 83% lower odds for the development of LVH, respectively. A similar 
tendency was seen for diastolic BP with patients exposed ≤50th pct showing 82% lower odds 
for LVH25.  
These findings substantiate that continuous exposure to high BP levels leads to LVH 
progression in pediatric KTx recipients, but also clearly point out that the conservative BP goal 
<90th pct is most likely insufficient to lower LVMI, especially for systolic BP. This further 
supports the hypothesis that a lower BP goal will be beneficial with regard to LVH, leading to 

 
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a reduction in CV disease and improved long-term patient survival. However, as these 
observations are inferred from observational data only a randomized controlled trial (RCT) 
prospectively evaluating the effect of different BP goals on LVMI (primary endpoint) is 
warranted. In fact, the KDIGO (Kidney Disease: Improving Global Outcomes) guideline on BP 
in patients with CKD recommends performing an RCT on the adequate BP goal in children, 
ideally using home- or office-based BP measurements27.  
Measurements for subclinical vascular damage as well as for early kidney injury will comprise 
our secondary endpoints. The surrogate markers for vascular damage will be aortic pulse-
wave velocity (PWV) and carotid intima-media thickness. Both have been shown to be 
predictive of CV mortality in adults28, 29 and are recommended parameters to be used as CV 
endpoints in studies by the American Heart organization 30. We have demonstrated in a variety 
of both single-center and multi-center observational studies that both PWV and IMT can be 
non-invasively and reprodicubly assessed in a variety of pediatric cohorts 17, 31-34. We will 
assess albuminuria and the estimated glomerular filtration rate (eGFR) as measures of kidney 
injury, as, again both can be easily measured. 
4. 
Aim of the study 
The proposed trial will confirmatory test whether intensified treatment of AH (i.e BP control 
≤60th pct, compared to standard BP control <90th pct) will lead to a lower LVMI in KTx 
recipients. Reducing LVMI will reduce long-term morbidity, improving quality of life and life 
expectancy in this population particularly vulnerable to CV disease. SOPHOCLES targets a 
central clinical problem that is highly relevant for the studied patient population, and 
addresses a major gap of knowledge. Its results have great potential to change future clinical 
practice. 
5. 
Outcome parameter 
Primary outcome parameter 
 
SOPHOCLES’ primary endpoint is LVMI at 24 months after randomization.  
  
In children and young adults after KTx, the incidence of CV events (e.g. myocardial infarction 
or stroke), despite being 100-fold higher compared to the normal population, is still too low 
to provide adequate power for an RCT with reasonable duration. LVH has not only been shown 
to predict the incidence of CV events and CV mortality 19, but more importantly, a decrease in 
left ventricular mass is associated with a decrease of CV risk 35-38. This makes LVMI a unique 
endpoint that ideally reflects CV risk 14. Furthermore, LVH assessment is also recommended 
in the European guidelines for pediatric hypertension 23. Therefore, LVMI is the most suitable 
endpoint for our trial. 
Secondary outcome parameter 
 
Secondary endpoints will be eGFR as a measure of kidney function, IMT as measure of 
atherosclerosis and PWV as measure of arteriosclerosis. eGFR will be calculated using the 
Schwartz bedside formula 39. IMT will be assessed from the recordings of the common carotid 
arteries, following the Mannheim consensus 40. PWV will be provided from Vicorder readings 
following established standardized operating procedures 3. 

 
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6. 
Design of the Trial 
The trial is a multicenter, randomized, controlled, parallel group trial with blinded endpoint 
evaluation comparing the effect of intensified vs. standard BP control on left ventricular mass. 
The flow chart (Fig. 1) illustrates the trial design and depicts the patient numbers from 
enrolment to analysis. 
 
 
Fig. 1 Patient flow chart 
7. 
Study Population 
7.1. 
Inclusion and exclusion criteria 
Inclusion criteria: 
Age between 6 and 18 years 
Kidney transplantation >12 months ago 
AH, i.e. systolic and/or diastolic BP >95th percentile (pct) or on antihypertensive treatment 
Exclusion criteria: 
Cardiac malformation 
Treatment for a rejection episode within three months prior to inclusion 
7.2. 
Patient numbers 
The planned patient numbers are depicted in Figure 1. 
7.3. 
Patient recruitment 
The participating centers provide care to a large number of pediatric KTx recipients allowing 
to screen more than 500 patients for eligibility. As highlighted in the trial’s flow chart (Fig. 1), 
we expect patients to be excluded because of age or not suffering from AH. Past experience 
taught us that pediatric KTx patients have a close relationship to their treating physicians, and 
show a high willingness to participate in clinical studies. We expect to screen no more than 
250 patients assuring the recruitment of the necessary number of patients within 24 months. 
Less than 20% of patients will come from study sites outside of Germany. No additional 
measures are planned to recruit patients. 
Drop-out 
~ n=3
Control group (n=85)
standard BP control (<90th pct)
Intervention group (n=85)
intensified BP control (≤60th pct)
Allocation
Continuously: BP Telemonitoring
Yearly: Endpoint assessment
Continuously: BP Telemonitoring
Yearly: Endpoint assessment
Follow up
To be analyzed
85 (ITT), 82 (PP)
To be analyzed
85 (ITT), 82 (PP) 
Analysis
Enrollment
n ~ 330 will not meet inclusion criteria 
Assessed for eligibility 
at 10 study-sites (n~500)
Drop-out 
~ n=3
Abbreviations: 
BP
blood pressure
ITT 
intention-to-treat
PP 
per protocol
pct
percentile
Randomized
(n=170)

 
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8. 
Study Procedures 
8.1. 
Informed consent 
Each family will receive detailed information on the purpose and procedures of the trial. In 
addition to thorough verbal information, a patient information form (provided in German, 
English, Turkish, Kurdish, Farsi, Ukrainian, and Russian) adapted to the respective age of the 
child will be handed out (see appendix), and any questions arising will be answered. Signature 
will be given by the legal guardians (“Sorgeberechtigte”) and if possible by the child itself. In 
the case a teenager reaches the age of 18 during the course of the study, he or she will give 
informed consent at the following study visit, again. No study specific tasks will be performed 
before reaching informed consent. The signed informed consent forms will be filed by the 
local investigators. 
8.2. 
Study procedures 
This trial will compare two different BP treatment goals. Pediatric KTx recipients will be 
randomly assigned to the intensified BP group or the standard BP group. Treatment goal in 
the intensified group will be lowering BP ≤60th pct. Data justifying this treatment goal are 
discussed in the introduction. The treatment goal for the standard group is to achieve BP levels 
<90th pct in accordance with pediatric guidelines for AH23, 41. The chosen antihypertensive drug 
regimen is in the discretion of the treating physician. 
All patients will measure BP at home using a telemonitoring device (Tel-O-Graph, IEM GmbH, 
Aachen, Germany) providing current BP data and allowing for the patients’ accustomed mode 
of documentation. The device enables telemonitoring through real-time transmission of BP 
data, which will be accessible to the MHH trial physician at the trial’s centralized BP office and 
to the treating physician on-site allowing for timely interventions and as an important safety 
feature. 
Physicians caring for the patients will have no restrictions in treating medical conditions (e.g. 
intercurrent infections or rejections) or changing any medication as part of the regular clinical 
care. Changes in medication and any adverse events (AE) or serious adverse events (SAE) will 
be recorded in the electronic case report form (eCRF).  
8.3. 
Investigational plan, assessment of endpoints 
The primary endpoint is LVMI at 24 months after randomization.  
Secondary endpoints will be eGFR as a measure of kidney function, IMT as measure of 
atherosclerosis and PWV as measure of arteriosclerosis. Table 1 provides the timepoints at 
which the endpoints will be assessed. 
Table 1. Frequency and scope of patients’ trial visits 
 
Screening 
Inclusion 
Month 
1 
3 
6 
9 
12 
15 
18 
24 
Informed consent 
X 
 
 
 
 
 
 
 
 
 
Inclusion/exclusion criteria 
X 
X 
 
 
 
 
 
 
 
 
Past medical history 
X 
 
 
 
 
 
 
 
 
 
Anthropometrics* 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Documentation of medication 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Local routine lab documentation 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Office BP measurement 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
AE assessment 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
Echocardiography 
 
X 
 
 
 
 
X 
 
 
X 

 
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Echocardiography will follow a standardized operating procedure established during the 4C 
study in accordance with the American Society of Echocardiography guidelines42. LVMI will be 
calculated by dividing left-ventricular mass in grams (according to Devereux43) by height in 
meters to the 2.16th with a correction factor of 0.0944. LVH is defined as an LVMI ≥45 g/m2.16 
independent of sex or age. eGFR will be calculated using the Schwartz bedside formula39. IMT 
will be assessed using ultrasound with a high-resolution linear probe, by averaging five 
measurements from the far wall of the common carotid artery 1-2 cm proximal of the carotid 
bulb, following the Mannheim consensus40. PWV will be provided from oscillometric 
measurements using the Vicorder device (Skidmore Medical Ltd, Bristol, United Kingdom) 
following established standardized operating procedures3. Appropriate normative data allow 
for PWV and IMT to be normalized by age and sex and to be expressed as z-scores. Blood and 
urine samples will be analyzed. eGFR will be calculated using the modified pediatric Schwartz 
formula Schwartz 2012], albuminuria will be measured in spot urine and given a albumin-to-
creatinine ratio.  
8.4. 
Study timeline, study duration 
Trial duration will be 24 months for each patient (Fig. 2). This time span is sufficient to reach 
the BP goal and to induce changes in LVMI. The stringent BP monitoring allows for a fast 
adaption of antihypertensive treatment with the aim to reach the target within three months. 
A shorter trial duration is not advisable as LVMI changes need time45. We expect the first 
visible changes to occur no sooner than after 6 months in the intensified BP group. As the 
magnitude of these changes increases over time, a longer trial duration allows for the 
recruitment of a smaller number of patients. Our analysis of 4C-T data25 demonstrated a 
robust difference in LVMI dependent of BP control after a median follow-up of 26 months. 
Hence, we based the trial duration on these data.  
Pediatric patients >12 month after KTx are routinely seen every 4-6 weeks in the outpatient 
clinic. The proposed quarterly trial visits (Tab. 1) can therefore be easily implemented without 
additional strain on patients. The annual evaluation will take approximately 45 minutes per 
patient. The non-invasive measurements include evaluation of LVMI by echocardiography, 
ambulatory blood pressure monitoring (ABPM) and assessment of secondary endpoints that 
will be executed by the same investigator team. Moreover, collected biomaterial (plasma, 
serum, urine) will be analyzed centrally to guarantee standardization of laboratory values. 
The duration of the whole study will be five years. 
PWV 
 
X 
 
 
 
 
X 
 
 
X 
IMT 
 
X 
 
 
 
 
X 
 
 
X 
ABPM 
 
X 
 
 
 
 
X 
 
 
X 
Centralized lab** 
 
X 
 
 
 
 
X 
 
 
X 
Biosampling (blood, urine) 
 
X 
 
 
 
 
X 
 
 
X 
*height, weight; **creatinine, cystatin C, urea, electrolytes, blood count, lipids, bone metabolism (PTH, AP, 25-OH-D3), urine 
analysis (protein/creatinine ratio). Abbreviations: ABPM, ambulatory blood pressure monitoring; AE, adverse event; BP, 
blood pressure; IMT, intima media thickness; PWV, pulse wave velocity 

 
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Fig. 2 Study timeline  
8.5. 
Adherence / Rate of Loss to Follow-Up 
From our experience from previous studies including RCTs, we expect an excellent follow-up 
adherence resulting in a low number of drop-outs24, 46. This is facilitated as all pediatric KTx 
recipients are under close, continuous surveillance at the participating centers; generally seen 
every 4-6 weeks. Thereby, the additional burden through the study is very low. The number 
of visits to the outpatient clinic essentially remains unchanged; only during the annual visits 
patients and their families will have to take extra time for the CV examinations. 
Echocardiography and the other CV examinations are non-invasive and known to be well-
tolerated. Blood samples will be collected in context of a routine blood draw. The trial’s design 
using telemonitoring approach will also facilitate superior protocol adherence.  
9. 
Methods 
9.1. 
Measurement of Cardiovascular Endpoints 
Echocardiography will follow a standardized operating procedure established during the 4C 
study in accordance with the American Society of Echocardiography guidelines42. LVMI will be 
calculated by dividing left-ventricular mass in grams (according to Devereux43) by height in 
meters to the 2.16th with a correction factor of 0.0944. LVH is defined as an LVMI ≥45 g/m2.16 
independent of sex or age. In a sub-cohort perfusion of the kidney transplant will be assessed 
by abdominal doppler ultrasound. IMT will be assessed using ultrasound with a high-resolution 
linear probe, by averaging five measurements from the far wall of the common carotid artery 
1-2 cm proximal of the carotid bulb, following the Mannheim consensus40. PWV will be 
provided from oscillometric measurements using the Vicorder device (Skidmore Medical Ltd, 
Bristol, United Kingdom) following established standardized operating procedures3. 
Appropriate normative data allow for PWV and IMT to be normalized by age and sex and to 
be expressed as z-scores. Blood and urine samples will be analyzed. eGFR will be calculated 
using the Schwartz bedside formula39, albuminuria will be measured in spot urine and given a 
albumin-to-creatinine ratio.  
9.2. 
Blood samples 
The amount of blood needed at the annual visits is 10-15 ml, the amount of urine will be 10-
30 ml. DNA analysis will require only 5 ml at one timepoint. The analyses of biochemical 
parameters will be performed in a centralized laboratory in Germany to guarantee 
comparability. Blood and urine samples will be stored in the Hannover Unified Biobank for 
future analysis with novel analytical methods (e.g. new biomarkers, proteomics). 
Year 1
Year 2
Year 3
Year 4
Year 5
Year 6
1st visit
2nd visit
3rd visit
Recruitment of patients
Site 
initiations
Data
structure
Data 
closure
Publications
75% visits
1st pat. in
last pat. out
25% visits

 
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10. Statistical analysis 
10.1. Sample size calculation 
Our data from the 4C-T study25 is the best fundament for sample size calculation. To simulate 
SOPHOCLES, we performed an additional analysis on a sub-group of 37 patients very closely 
resembling the inclusion and exclusion criteria for our planned trial. At baseline, these patients 
were 6-16 years old, were transplanted ≥9 months ago and presented with AH. We observed 
the lowest LVMI corrected mean value in patients who were exposed to cumulative systolic 
BP of ≤75th pct (47.4±12.0 g/m2.16) when compared to patients exposed to values >90th pct 
(52.3±11.5 g/m2.16) or patients between >75th and ≤90th pct (52.7±11.4 g/m2.16). We consider 
the observed difference of 5.3 g/m2.16 in LVMI achieved between the ≤75th pct and the >75th-
≤90th pct as clinically relevant. A closer look at patients below ≤75th pct showed a skewed 
distribution with a median systolic BP exposure of 57.5th pct (IQR: 51st-66th pct, maximum: 71st 
pct) supporting our proposed BP target of ≤60th pct.  
A sample size calculation based on the corrected means of the sub-group analysis (47.4 vs. 
52.7 g/m2.16), a common standard deviation of 12 g/m2.16, an unpaired t-test with a two-sided 
type-one error of 5% and a power of 80% resulted in a sample size of at least 82 patients for 
each group (nQuery® 9.2.1.0.). We expect only few drop-outs and therefore only added 3 
patients per group to account for withdrawal of consent. This results in an overall sample size 
of 170 patients. Importantly, it is assumed that the planned mixed model approach in the 
primary analysis will increase power compared to the t-test used for sample size calculation 
because of stratification, highlighting our conservative approach in setting up this trial. 
10.2. Primary analysis 
According to the intention-to-treat (ITT) principle, analysis of the primary endpoint will include 
all randomized patients. A linear mixed model for repeated measures (MMRM) will be used 
to analyze the contrast in LVMI (least squares means at month 24 after randomization) 
between groups. Treatment group, LVMI at baseline, visit, the stratification factors (center, 
sex, age group) and treatment-by-visit interaction will be included as fixed effects. Patient will 
be included as random effect, an unstructured covariance pattern is assumed to model the 
within-patient errors. Restricted maximum likelihood (REML) in combination with the 
Newton-Raphson algorithm will be used to obtain parameter estimates. The Kenward-Rogers 
method will be used for estimation of the denominator degrees of freedom. Superiority of 
intensified treatment will be concluded, if the upper boundary of the 95% confidence interval 
for the estimated treatment effect (contrast of intensified minus control group at month 24) 
is below 0. In the unlikely situation that the model does not converge, a simplified model (i.e. 
simplified covariance pattern, such as compound symmetry, or a fixed effects model) will be 
used for the primary analysis. Missing values will be implicitly imputed by the MMRM. 
To assess the robustness of the model, various sensitivity analyses will be performed. 
Specifically, the impact of missing values (e.g. replacement by last-observation-carried-
forward in an ANCOVA model) will be examined. Nature and extent of missing values will be 
compared between treatment groups and a per-protocol analysis, which consists of all 
patients who complete the study in accordance to the study protocol, will be conducted. 
Furthermore, subgroup analyses will be performed for age group, sex and center. 

 
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10.3. Secondary and exploratory analysis 
Analysis of the three secondary endpoints (eGFR, IMT, PWV at month 24 after randomization) 
will be in line with the primary analysis. 
AEs and SAEs will be documented and recorded. We will calculate relative and absolute 
frequencies of AEs per intervention arm at the event level and at the patient level. A two-sided 
chi-squared test will be used to compare the intervention and control group. Expected AE 
related to the study intervention can occur due to lowering of BP per se (dizziness, nausea, 
weakness, but also acute worsening of kidney function) and due to side effects of the 
antihypertensive medications (e.g. edema from calcium antagonists, cough from ACE 
inhibitors, electrolyte disorders from diuretics). 
10.4. Measures against Bias 
Permuted block randomization with variable block length will be used to allocate patients 1:1 
to both groups. The following strata will be used: study-center, sex (male or female), age group 
(<11 or ≥11 years) and left ventricular hypertrophy (<45 g/m2.16 vs ≥45 g/m2.16). The 
randomization list is generated centrally by the Institute of Biostatistics, allocation is 
performed via the eCRF system. During the trial only the statistician and the unblinded data 
manager will have access to the randomization list.  
All echocardiographic and secondary endpoint readings will be performed by the same 
investigators who will be uniformly trained according to the standards established as part of 
the 4C study26. The analyses of these readings will be performed centrally by investigators 
blinded with regard to the patient’s intervention group and time point of the measurement.  
As a result of an increased awareness for BP control by treating physicians on site, we expect 
an improvement in BP levels also in the standard group during the trial. The telemonitoring 
approach, however, will assure clear differentiation between both groups. The transmission 
of BP data and the close contact between MHH trial physician and treating physicians will 
assure strict target control and immediate corrections, if targets are not met. For 
generalizability, we aim to recruit a representative patient population. In consequence, the 
only exclusion criterion are cardiac abnormalities that very rarely occur, but would impede 
measurement of the primary endpoint. 
11. Stopping Rules 
On the individual level, the patients receive no specific treatment but are assigned to different 
treatment goals. In this setting, we believe that any stopping rules carry the risk of inducing 
bias into our study. Patients’ safety is guaranteed by telemonitoring of blood pressure values 
allowing for timely reaction if blood pressure levels are too low. This situation then will prompt 
adaption of treatment but not exclusion from the study. The only reason for early stopping of 
the study is withdrawal of patients’ consent, unforeseeable new ethical or medical aspects. A 
single center might wish to stop the study due to logistic reasons. 
In context of the whole study the primary endpoint is left ventricular mass measured after 
two years. The recruitment period also spans two years (see Fig. 2 Study timeline). Hence a 
meaningful preliminary endpoint assessment of e.g. half of the patients would only be possible 
very late in the trial. Therefore, stopping the trial at this time point e.g. due to an 
overwhelming positive result would not be reasonable.  

 
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12. Risk-benefit assessment 
The principle study aim is ethically justified because of the scientific uncertainty which of 
the two interventions (standard vs. intensified BP management) will result in a more favorable 
risk-benefit profile. While observational data suggest that stricter BP control will translate into 
a reduction of left ventricular mass and better patient survival, the intensified protocol might 
have disadvantages as well. These may be due to worsening of overall treatment adherence 
because of an increased drug burden, but also due to potential side effects of lowering BP 
(such as dizziness or even acute worsening of kidney function), or side effects coming from 
antihypertensive medication itself (e.g. edema from calcium antagonists, cough from ACE 
inhibitors, electrolyte disorders from diuretics). In conclusion, we believe that clinical 
equipoise is assured.  
Both groups will benefit from improved monitoring of BP between outpatient visits based on 
telemonitoring and timely response to BP levels outside the target range. Thereby, the 
standard treatment group will profit as well due to greater awareness of their AH, as in every 
day practice AH is not treated sufficiently, with one third of KTx patients displaying BP values 
>95th pct8, 17. 
Before and during the clinical trial, regular risk management will be performed according to 
ICH-GCP. Every subject participating in the trial will be insured against any trial-related 
illness/injuries. An independent data safety monitoring board (DSMB) will be established, 
consisting of three independent experts, that oversees patient safety and assure the 
risk/benefit assessment while the trial is ongoing. Throughout the trial, the DSMB will monitor 
safety data according to a pre-specified plan (DSMB charter). DSMB members are 
independent from the PIs, the trial’s investigators and the medical institutions involved. 
Together, the DSMB members form an independent multidisciplinary group of clinicians and 
biostatisticians that, collectively, have experience in the management of pediatric KTx 
recipients and the conduct, monitoring and statistical analysis of RCTs. The DSMB will give 
advice to PIs and the trial steering committee (TSC) whether to continue, modify, or stop the 
trial. Importantly, this will include the assessment whether the separation of BP values 
between the intensified and the standard group is sufficient. If not, the DSMB will discuss the 
issue with the trial steering committee. This will allow to take additional measures to reinforce 
BP goals early enough during the course of the trial. Detailed rules on the flow of data and 
communication between the parties involved in the trial and the DSMB will be set forth in a 
separate DSMB charter. The TSC also involves independent external experts that will review 
the trial’s recruitment and progress 
13. Data Security 
An eCRF will be used by employing an electronic data capture system. The system has been 
fully validated according to the applicable criteria and regulations (e.g. GCP). Personal data of 
all participating patients will be handled in accordance with the General Data Protection 
Regulation (GDPR) of the European Union, all respective patient rights will be granted (Art. 
12-23- DSGVO). Pseudonymized data will be entered only by authorized and trained staff. A 
clinical trial data base allows data entries remotely via the eCRF. Data quality will be verified 
by centralized and on-site monitoring as well as via range, validity and consistency checks 
programmed in the system. All changes of data entered in the eCRF will be documented by an 

 
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audit trail. A quality control will be performed and documented before the database is closed. 
The complete data set will be archived in the central electronic MHH archive in compliance 
with the corresponding regulations. After data transfer, data analyses will be performed by 
the responsible biostatistician.  
Responsible for data management will be the principal investigator, Prof. Melk. The data 
safety manager at MHH is Joachim Barke. 
14. Biobanking 
Collected biomaterials will be stored at Hannover Unified Biobank (HUB), which follows 
highest quality standards and is certified according to DIN EN ISO 9001:2015.  
Samples from this study in this pediatric cohort with long-term follow-up are unique as they 
will never be retrieved again in a similar set-up. Because these samples are extremely 
precious, the patients and parents will be asked to allow us to store them without time 
restriction. 
15. Insurance 
The subjects participating in the trial will be insured against any trial-related illness/injuries 
(“Jahresvertrag zur Probanden- und Wege-Unfall-Versicherung” Nr. 79 153194 03016/03192, 
Insurance company: HDI Global SE, Customer number: 2330 99 0302 / 1502, application 
number 03022024301). 
16. Publication rules 
We intend to publish the results of the trial. The publication rights are with the principal 
investigator. The principal investigator will assure that contributions of participating 
individuals and centers are acknowledged.  
 
 
 

 
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