The study was funded by ZonMw and conducted in a successful collaboration between six Dutch university medical centres (UMCG, Erasmus MC, Amsterdam UMC, LUMC, UMC Utrecht, Radboudumc) and the University Hospital Leuven. A total of 379 kidney transplant recipients aged 65 or older participated. The results will be presented today, Friday 7 November 2025, during Kidney Week in Houston (USA) and will be published simultaneously in the journal JASN (Journal of the American Society of Nephrology).
Older kidney transplant recipients generally have a lower risk of rejection due to an ageing immune system, but a higher risk of infections as a complication of immunosuppressive therapy. In addition, they often receive kidneys from older donors, who are more sensitive to the harmful effects of tacrolimus on the kidney. Since transplant loss in older people is usually due to patient death rather than rejection, it was assumed that older patients could benefit from less intensive immunosuppressive treatment with fewer side effects.
A total of 379 patients participated in the study. Half of them received the standard treatment with prednisolone, standard dose tacrolimus and mycophenolate mofetil after transplantation, while the other half received the modified treatment with prednisolone, low-dose tacrolimus and everolimus.
After the transplantation, the researchers continued to monitor the participants and after two years assessed how many successful transplants there were in both groups. A transplant was considered successful if the participant was alive with adequate kidney function. A distinction was made between transplants with a kidney from an older deceased donor (kidney function ≥30 ml/min) and a younger deceased donor or living donor (kidney function ≥45 ml/min).
Two years after transplantation, no difference was found between the two groups in the primary outcome measure, with 50% “successful transplantations” in the low-tacrolimus group and 57% in the standard group.
Kidney function, patient and transplant survival were also similar. The number of rejections was low and did not differ between the two treatment arms.
Overall, the outcomes in both groups were very good, with patient survival of 89% and loss of the donor kidney in only 6% (low dose) versus 5% (standard dose) of participants.
‘We have shown that lower doses and alternative combinations of immunosuppression can be safe in older patients, but do not automatically lead to better outcomes,’ say Prof. Stefan P. Berger and Prof. Jan-Stephan Sanders, nephrologists at the UMCG and principal investigators of the OPTIMIZE study. “The results help us to further personalise treatment and tailor it better to individual elderly patients.”
The OPTIMIZE study shows that a reduced immunosuppressive regimen in older kidney transplant patients is safe but not superior to standard treatment. The results form an important basis for future studies focused on personalised immunosuppression, in which age, comorbidity and immunological risk profiles are central.
