Prospective donor-specific Cellular alloresponse assessment for Immunosuppression Minimization in de novo renal transplantation

The current immunosuppressive therapy consists mainly from combination of three
to four immunosuppressant agents. This therapy is not only costly, but leads
also to many undesirable side effects, which not only limit its efficacy
(impossibility to titrate to the required dose) but decrease also the patients
adherence to therapy. Intensive research is currently ongoing to improve the
treatment complexity and thus improve the adherence of patients, reduce the
burden of side effects and decrease the cost of therapy. Minimizing
immunosuppression (IS), e.g. monotherapy, as early as possible without losing
control of acute/chronic rejections would be of great benefit and could reduce
adverse effects and costs. However, this is only possible in a minority of
patients yet. Therefore, a precise evaluation of the anti-donor alloimmune
response in order to identify patients likely to accept the graft with no or
very low IS would be of great value. One of possible approaches is the
tacrolimus (TAC) monotherapy avoiding corticosteroids and antiproliferative
agents (mycophenolate mofetil - MMF), which may lead to substantial reduction
of the immunosuppressive load and improve the cardiovascular risk profile.
Several papers about TAC monotherapy were already published in the area of
kidney transplantation. Although most of them reported relatively positive
results with monotherapy, BPAR rates were significantly higher as compared to
standard of care IS, despite using relatively high TAC trough levels which also
negatively impacted to the 6-month allograft function. Other attempts for TAC
monotherapy have been done in non-randomized, single centre pilot studies,
especially using T-cell depleting agents such as Alemtuzumab with rather
contradictory and inconclusive results.
In humans, the assessment of the immunologic risk is exclusively based on the
detection of preformed circulating alloantibodies, with the assumption that
humoral allosensitization also illustrates the allospecific T-cell
effector/memory immune response. This is of great importance, as it is well
known that cellular memory may occur without humoral activation and that
alloreactive cellular responses are key players in initiating and mediating
allograft rejection. In fact, with the current accurate screening of humoral
sensitization, rates of antibody-mediated rejection (ABMR) have significantly
been reduced but T-cell mediated acute and chronic rejection (TCMR) is still
observed after renal transplantation, especially among patients not receiving
CNI-based IS. This fact is in line with in vitro studies showing that
alloreactive T-cell responses are particularly sensitive to CNI drugs as
compared to other immunosuppressants. Noteworthy, in the last years, attempts
trying to immune-monitor the T-cell alloimmune response using novel immune
assays have been done in kidney transplantation. Among the most robust
functional assays measuring T-cell alloreactivity the IFN-γ enzyme-linked
immunosorbent spot (ELISPOT) assay has been shown in multiple reports to be
capable of accurately assess the presence of highly alloreactive circulating
memory/effector T-cells with donor-antigen specificity, both before and after
transplantation, discriminating patients with increased risk for TCMR and worse
graft function evolution, even in absence of humoral allosensitization.
Furthermore, 2 recent reports performed in the context of the European RISET
consortium, showed on the one hand, the cross-validation among different
laboratories of the IFN-γ ELISPOT assay to accurately assess anti-donor
alloreactive T-cell frequencies in the context of kidney transplantation, and
on the other, that prospectively monitoring donor and non donor-specific T-cell
alloreactivity using the IFN-γ ELISPOT before and after transplantation may
allow safe individualization for induction and maintenance of CNI-free IS in
renal transplant recipients, discriminating patients with the better 1-year
graft function as well as individuals with preserved graft parenchyma at
6-month protocol biopsies.
Therefore, pre-transplant assessment of anti-donor T-cell alloresponses using
the IFN-γ ELISPOT may help to accurately discriminate patients that may safely
benefit from receiving low IS based on induction therapy with basiliximab and
low doses TAC monotherapy, from others that should stay on higher IS such as
the current standard

The main objective of the study is to demonstrate the utility and safety
of the IFN-γ ELISPOT marker for the stratification of kidney transplant
recipients into low and high IS regimens. The enrichment study will test
non-inferiority of low IS regimen compared to high IS regimen,
assuming 10% of BPAR at 6-months in the control group, and allowing a
non-inferiority limit of maximum 15%.

This is a biomarker strategy design randomized trial, whereby only pre-TX
ELISPOT negative patients will be enrolled into the study and randomized 1:1 to
either low or high IS regimen. The study will test non-inferiority of low IS
regimen compared to high IS regimen, assuming 10% of BPAR at 6-months in the
control group, and allowing a non-inferiority limit of maximum 10%. First
kidney transplant recipients that provide consent to participate in the study
will be evaluated for their anti-donor T-cell alloresponse using the IFN-γ
ELISPOT assay before kidney transplantation (TX). Patients with a positive
anti-donor IFN-γ ELISPOT assay result (>25 spots/300.000 PBMC) will be ruled
out of the study and patients with negative anti-donor IFN-γ ELISPOT test (<25
spots/300.000 PBMC) will be randomized in 2 different groups (1:1): GROUP A:
STANDARD OF CARE: Standard of care immunosuppressive regimen based on TAC
(achieving 4-8ng/ml trough levels), MMF (1gr bid) and steroids (according to
KDIGO guidelines). GROUP B: *Low* Immunosuppression regimen (based on TAC
monotherapy to achieve 8-10 ng/ml trough levels during the first 4 weeks after
transplantation and 6-8 ng/ml thereafter, MMF (1g bid) during the first 7 days
post-transplant and stopped thereafter) and steroids (tapering until
discontinuation on month 2 post-transplant). All patients will homogenously
receive 2 doses of Basiliximab (day 0 and day 4 after transplantation). In
addition to the decision-making ELISPOT, several other biomarkers* will be
analyzed during follow-up in all randomized kidney transplant patients. The
trial will need to recruit 301 patients allowing for 10% drop-out rate, having
271 patients with complete follow up for primary outcome. Considering that
approximately 45% of patients are ELISPOT negative, 669 patients will need to
be screened. Patients will be followed up for a total of 12 months for
secondary outcome measures.

Most visits will be intertwined with the regular follow-up visits. Extra is a
renal transplant biopsy performed at three months after transplantation. The
patient will have to be admitted to the hospital for half a day. This biopsy is
< 5% complicated by a small hematoma around or in the kidney.