Background

The evolution of immunosuppressive regimens over the past few decades has led to considerable improvement in acute rejection rates and short-term graft survival [1]. Patient and graft survival at 1 year post transplantation now exceed 95 % in the case of living donation and 90 % after deceased donation. However, the long-term outcomes post kidney transplantation do not show a similar trend of improvement. At 10 years, graft survival remains about 50 % after deceased donation in the US and in Europe, with approximately 30 % of patients returning to dialysis and one of four patients dying with a functioning graft [1, 2]. The lack of improvement in long-term outcomes is further reflected by the fact that the number of re-transplants among adult kidney transplant patients has remained almost unchanged over the last decade [1].

Currently, calcineurin inhibitors (CNIs), cyclosporine, and tacrolimus are the cornerstone of immunosuppressive therapy post kidney transplantation [1]. However, their long-term use may be associated with non-reversible nephrotoxicity, morphologically characterised by striped fibrosis, progressive arteriolar hyalinosis, and ischemic glomerulosclerosis, which is a well-recognised cause of morbidity in transplant patients [3–5]. Chronic allograft injury alone accounts for two thirds of kidney graft failures [6]. Clinical data has shown that lowering the dose of CNI can improve renal function [5–7]. In this regard, the focus should be on optimising the currently available immunosuppressive regimens with the aim of preserving long-term renal function while maintaining the efficacy [8]. Several studies with a reduced-dose CNI and everolimus regimen have shown that it maintained efficacy and preserved renal function (Table 1) [9–33]. In the large randomised A2309 trial, pre-emptive everolimus therapy was associated with a greater than 60 % reduction in cyclosporine exposure while preserving renal function with comparable efficacy to mycophenolic acid and standard-exposure cyclosporine in de novo kidney transplant patients [16, 17]. In the ASSET study, an everolimus-facilitated tacrolimus minimisation strategy achieved good renal function with an acceptable safety profile without compromising efficacy [23]. Moreover, everolimus exerts other non-immunosuppressive properties, including potential cardioprotective, anti-malignancy, and antiviral effects [34–41]. These non-immunosuppressive benefits further suggest that everolimus-based regimens may be a preferred approach as cardiovascular disease, malignancy, and infections account for nearly four out of the five deaths occurring with functioning grafts [6].

Table 1 Everolimus in kidney transplantation
Full size table

The ATHENA trial is designed to further increase our knowledge and seek answers relating to the use of everolimus in CNI minimisation protocols in de novo kidney transplant patients. The ATHENA study assesses the change in renal function at 12 months post transplant as the primary objective. The design of the trial is described here.

Methods/Design

Study design

ATHENA (Clinicaltrials.gov: NCT01843348; EUDRACT number: 2011-005238-21) is a 12-month, multicentre, randomised, international, prospective, controlled, open-label study with three parallel treatment groups in de novo kidney transplant recipients receiving renal allografts from deceased or living donors (protocol version 3, 29 July 2014). Eligible patients are randomised before transplantation using a validated system to ensure an unbiased treatment assignment in a 1:1:1 ratio to receive either everolimus with a reduced dose of cyclosporine, or everolimus with tacrolimus, or a standard regimen of mycophenolic acid with tacrolimus (Fig. 1). All patients receive induction therapy with basiliximab and maintenance steroids. At the time of randomisation, patients are stratified based on the donor type (living donor, deceased standard criteria donor, or deceased expanded criteria donor) and the participation of the recipient in the European Senior Program. The study protocol and the proposed informed consent form were reviewed and approved by the national institutional review boards or independent ethics committees at each centre and the federal institute for drugs and medical devices (Additional file 1). Written informed consent was obtained from all patients. The clinical study was designed and is conducted in accordance with the ethical principles laid down in the Declaration of Helsinki.

Fig. 1
figure 1

Study design. Steroid dose will be at least 5 mg prednisolone or equivalent, according to centre practice. EC-MPS enteric-coated mycophenolate sodium. M month, MMF mycophenolate mofetil, MPA mycophenolic acid, RND randomisation, Tx transplantation

Full size image

Study population

The study population comprises de novo adult patients receiving a primary or secondary kidney transplant from a deceased or living donor. In the case of second kidney transplants, patients could be enrolled only if the first graft loss is due to non-immunological reasons. Patients are not eligible for the study if they are recipients of an ABO-incompatible transplants, have pre-existing donor-specific antibodies (DSA), or have an organ cold ischemia time longer than 30 h. Patients with pre-existing human leukocyte antigen (HLA)-antibodies not directed against the donor and less than 20 % panel reactivity at the time of transplant were included in the study. Detailed inclusion and exclusion criteria are shown in Table 2.

Table 2 Key inclusion and exclusion criteria
Full size table

Study objectives

The primary objective at month 12 post transplantation is to demonstrate non-inferiority in renal function assessed by the glomerular filtration rate (Nankivell formula) [41] in at least one of the everolimus treatment regimens compared with the standard treatment group receiving mycophenolic acid and tacrolimus. The key secondary objective at month 12 is to evaluate the incidence of treatment failure defined as biopsy-proven acute rejection (BPAR), graft loss, or death among the treatment groups. Other objectives include assessment of individual components of treatment failure, incidence and severity of viral infections (cytomegalovirus (CMV), BK-virus (BKV)), incidence and duration of delayed graft function (DGF), incidence of indication biopsies, incidence of slow graft function, incidence of wound healing complications, and duration of healing. Incidence of viral infections (CMV and BKV) and changes to the viral load are closely monitored throughout the study. In addition, a patient subgroup analysis of CMV-specific T-cells and NK-cells is conducted in a central laboratory. Overall, the safety objectives include assessment of adverse events (AEs) and serious AEs (SAEs), infections and discontinuations due to AEs, and laboratory abnormalities. Exploratory objectives include evaluation of the incidence of HLA-antibodies and among those DSA and non-HLA antibodies (AT1R, ETAR) by treatment group and its association with acute rejection. HLA-antibodies including DSA were analysed using single antigen Luminex technology at baseline and month 12. In addition, left ventricular (LV) changes are measured by LV hypertrophy (LVH) assessment by echocardiography measurements. Detailed objectives of the study are outlined in Table 3.

Table 3 Objectives of the ATHENA study
Full size table

Immunosuppression

All patients receive induction therapy with basiliximab dosed at 20 mg intravenously on the day of transplantation and on day 4 post transplantation, as per label recommendations. Patients are randomised to receive everolimus at an initial dose of 1.5 mg/day with a reduced dose of cyclosporine and 3 mg/day with tacrolimus within the first 24 h post transplantation. Thereafter, the dose of everolimus is adjusted to the target trough concentration of 3–8 ng/mL throughout the study period. Treatment with CNI, tacrolimus, or cyclosporine, is initiated within the first 24 h post transplantation, and the dose of CNI is adjusted to maintain the target trough levels, as shown in Fig. 1. In the control group, patients receive mycophenolic acid at a dose of 1.44 g/day enteric-coated mycophenolate sodium or at a dose of 2 g/day mycophenolate mofetil with a standard dose of tacrolimus. Dose adjustments and interruptions are allowed for tolerability reasons as defined in the protocol and are recorded. All patients receive corticosteroids at a minimum dose of 5 mg/day prednisolone or equivalent until month 12. Acute rejections are treated according to local practice and physicians’ discretion. All patients who prematurely withdraw from the study are provided with follow-up medical care/referred for appropriate ongoing care, as per the local practice.

Concomitant medication

Mandatory CMV prophylactic therapy with valganciclovir is recommended for at least 3 months in the case of high- to moderate-risk patients (CMV-positive donor/CMV-negative recipients or CMV-positive donor/CMV-positive recipients). All patients receive prophylactic treatment for Pneumocystis jirovecii pneumonia with trimethoprim/sulfamethoxazole for a period of 6 months. All medications and significant non-drug therapies administered after the initiation of the study drug are recorded.

Data collection

Patient visits are scheduled at baseline, and at months 1, 3, 6, 9, and 12 post transplantation. A detailed list of all study assessments and visits is shown in Table 4. Patients who discontinue the study drug and those who prematurely withdraw from the study are scheduled for a visit and all the assessments listed for visit 6 are performed.

Table 4 Assessment schedule
Full size table

Renal function

Renal function is assessed by determining the glomerular filtrate rate using serum creatinine values according to the Nankivell formula [42] and used as the primary outcome measure in the study. In addition, as a secondary efficacy variable, the glomerular filtration rate is calculated using the Cockcroft-Gault method [43], the modification of diet in renal disease (MDRD) method [44–46], and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) method [47]. Serum creatinine levels are analysed using venous blood drawn and analysed in the local laboratory.

Outcome measures

BPAR is defined as rejections that are acute and proven by biopsy. The time to BPAR is the time from randomisation to the date of first documented BPAR. Graft loss is defined as a failure to discontinue dialysis or if the patient undergoes graft nephrectomy. Overall survival is defined as time from date of randomisation to death due to any cause. Delayed graft function is defined as the need for dialysis within the first 7 days post transplantation excluding the first day, and the duration is defined from the first dialysis day up to the last. Slow graft function is defined as serum creatinine >3.0 mg/dL at day 5.

Kidney allograft biopsy

Optional allograft biopsies are performed intra-operatively at the time of transplantation and at month 12. A control biopsy at month 6 may be performed according to centre practice. In all cases of suspected acute rejection, a graft biopsy is performed prior to, or within 24 h of initiation of anti-rejection therapy. All biopsies are read by the local pathologist according to the updated Banff 2009 criteria. Optional biopsies are assessed for the presence of interstitial fibrosis and tubular atrophy using the Banff 2007 criteria.

Non-HLA and HLA antibodies

The presence and evolution of non-HLA and HLA antibodies, and among those especially DSA antibodies in the serum, is evaluated at a central laboratory. Blood samples (5 mL) are collected for all patients at baseline, month 6, and month 12.

LVH and diastolic dysfunction

The echocardiographic analysis included assessments of the end-diastolic interventricular septum, LV end-diastolic posterior wall thickness, LV end-diastolic diameter, LV end-systolic diameter, LV end-diastolic volume, LV end-systolic volume, LV ejection fraction, relative wall thickness, and LV mass also expressed as LV mass index [48]. LVH was defined as an LV mass index exceeding 110 g/m2 in women and 125 g/m2 in men, and a value of 0.44 was taken as cut-off point for abnormal relative wall thickness [49]. Diastolic dysfunction was assessed and graded according to the guidelines of the American Society of Echocardiography [50].

CMV substudy

In this optional substudy, 4.7 mL of whole blood is drawn into a lithium heparin-containing tube at baseline and at month 12 or at the end of study/treatment, and shipped on the same day to a central laboratory at 4 °C. This substudy prospectively monitors the incidence of viraemia by analysis of viral load, CMV-specific T-cell frequency, phenotype and functionality, and regulatory T-cells, and T- and NK-cell subsets.

Data Monitoring Board

An external and independent Data Safety Monitoring Board was instituted before the start of the study. The board reviews safety-related issues on an ongoing basis and is entitled to make recommendations for changes in study conduct.

Statistical analysis

The primary efficacy variable, i.e., renal function at month 12 after randomisation between the treatment groups will be compared with the analysis of covariance (ANCOVA) model, using the treatment and centre as factors, and the estimated glomerular filtration rate at baseline as a covariate. Missing estimated glomerular filtration values will be handled within the ANCOVA analysis by multiple imputations by the last available post-baseline observation carried forward (LOCF) approach. Assuming a common dropout rate of 20 %, a sample size of 612 patients (204 patients in each treatment arm) is required in the study, so as to have at least 80 % power to demonstrate non-inferiority (2.5 % margin, one-sided t test) for the primary endpoint.

The primary analysis is based on the full analysis set that consists of all patients who receive at least one dose of the study drug. The per-protocol set includes all patients in the full analysis set who do not have any major deviations from the protocol procedures that may impact the study outcomes. The safety set consists of all patients who receive at least one dose of the study drug and had at least one post-baseline safety assessment.

Discussion

ATHENA is one of the largest European multicentre kidney transplant studies. It is the first study evaluating the non-inferiority of renal function as a primary objective in a de novo everolimus-based immunosuppressive protocol, and will determine whether an everolimus-based regimen can preserve renal function versus the current standard of care. The study will also provide insights into the evolution of HLA and non-HLA antibodies, occurrence of viral infections post transplantation, surveillance of cardiovascular comorbidities, and the incidence of wound healing complications [51]. In addition, the trial explores a regimen of everolimus with reduced-dose cyclosporine while the dose of tacrolimus in the everolimus arm and the standard arm is the same. These unique features will further enable the study to provide a direct comparison between the two arms, which will in turn help in optimising the immunosuppressive protocols. As the study addresses a wide range of issues that clinicians face today, its results are awaited with interest.

Trial status

The study is currently ongoing and actively recruiting patients across 27 sites, 15 centres in Germany and 12 centres in France. The study is expected to be complete by March 2016.