<qa>  What is the main efficacy variable?If the drug or study regime is efficient, the observed change after the transplantation surgery will have to be fast and objective. The increase of serum creatinine between 6 and 12 months post-transplant is a reliable marker of graft failure risk, and the magnitude of the serum creatinine change in these months is a marker of the relationship with long-term survival. For that reason, renal function serum creatinine is included as a main efficacy variable. 