Immunomonitoring of stable renal transplantation patients receiving triple immunosuppressive therapy

Kidney transplantation is a successful treatment option for patients with
end-stage renal disease. To prevent allograft rejection, renal transplant
patients need long-term immunosuppressive therapy with tacrolimus,
mycophenolate mofetil (MMF) and prednisolone. The disadvantages of this
maintenance treatment regimen, however, is the large intra- and interpatient
variability in clinical outcome, especially for tacrolimus. Too little exposure
leads to a risk of acute rejection and formation of donor-specific antibodies,
while too much exposure leads to an increased risk of infection and
nephrotoxicity.

To minimize adverse effects and improve effectiveness of the current treatment
regimen, therapeutic drug monitoring (TDM) is routinely performed. For
tacrolimus, the most common method of TDM is measuring pre-dose trough
concentration (C0) in whole blood. These trough concentrations, however, are
highly variable and the correlation with clinical outcome is still debatable.
TDM is not standardly performed for MMF and prednisolone treatment, and therapy
is usually not individualized. To improve dosing strategies and minimize
adverse effects, the current TDM should be optimized. We advocate that PD-based
instead of PK-based therapeutic drug monitoring, by using clinically relevant
immune tests to quantify the immunosuppressive state of the individual patient,
may improve the clinical outcome.

For that reason, we have developed several whole blood-based PD readout
measures for the quantification of immunosuppression. These readout measures
(PHA-induced cytokine production, T cell proliferation and T cell activation
marker expression) were previously tested in healthy volunteers and have shown
to be suitable for quantification of the immunosuppressive effect of a single
dose of tacrolimus, cyclosporine A and mycophenolic acid. In the current
clinical study we aim to evaluate if the selected PD readout measures are also
suitable for immunomonitoring of renal transplantation patients receiving
long-term triple immunosuppressive therapy. We will evaluate the relationship
between drug concentrations and cellular PD measures, and between the PD
measures in vitro and ex vivo.

Besides the high variability and small therapeutic window of tacrolimus, the
patient*s age also affects clinical outcome. Elderly transplantation patients
are generally prescribed lower doses of tacrolimus, while the dose-normalized
C0 concentrations are higher than in the younger patients. Moreover, aging
causes the number of effector lymphocytes to decrease, which result in a
reduced immune response to the transplanted organ. These age-related changes
are one of the reasons that elderly transplant recipients are more likely to
suffer from side effects of over-immunosuppression, such as diabetes and de
novo malignancies. To investigate if the relationship between drug
concentration and cellular PD measures changes with age, we aim to include
kidney transplantation patients with a wide range in age (>18 years).

1. To monitor the level of immunosuppression in individual renal
transplantation patients, based on cell-based ex vivo PD readout measures over
a short time window (one day);
2. To evaluate the relationship between the pre-dose in vitro PD effect and the
post-dose ex vivo PD effect in renal transplantation patients;
3. To evaluate the relationship between the different PD readout measures (T
cell activation, proliferation, cytokine production) in renal transplantation
patients;
4. To evaluate the variability in PD readout measures between stable renal
transplantation patients;
5. To evaluate the effect of age on the PK and PD profiles of renal
transplantation patients;
6. To evaluate circulating regulatory T and B cell subsets in renal
transplantation patients;
7. To evaluate the relationship between drug concentrations (tacrolimus, MPA
and prednisolone) and PD readout measures in renal transplantation patients,
based on a semi-mechanistic modelling approach.

Observational study in young and elderly renal transplantation patients on a
combination of tacrolimus, MMF and corticosteroid treatment.
Patients will be in-house for a single visit to take PK and PD blood samples
before and after their medication intake.

This study does not involve the use of investigational medical products. Renal
transplantation patients enrolled in this study will be on triple
immunosuppressive therapy (tacrolimus, MMF and prednisolone), which is the
standard treatment for these patients and is prescribed by their treating
nephrologist. The dose and regimen of these drugs will not be adjusted for
their participation to this study. The main intervention that the study
participants will undergo is blood withdrawal for PD measures. There is no
benefit for the patients participating in this study. The only risk associated
with participation is bruising from the blood sampling.