Study on the Safety and Efficacy of a Time-of-Day-Based Individualized Tacrolimus Dosing Regimen in Kidney Transplant Recipients

The goal of this clinical trial is to evaluate whether chronopharmacokinetic model-guided individualized unequal twice-daily tacrolimus dosing improves renal allograft function and reduces acute rejection in stable kidney transplant recipients. The main questions it aims to answer are: Does chrono-individualized tacrolimus dosing preserve graft renal function (eGFR) compared with conventional equal twice-daily dosing? Does chrono-individualized tacrolimus dosing lower the incidence of acute rejection in kidney transplant recipients? Researchers will compare recipients receiving chronopharmacokinetic-guided "low morning, high evening" individualized tacrolimus doses to recipients receiving conventional equal twice-daily tacrolimus doses to see if the chrono-individualized regimen improves renal function and reduces acute rejection risk. Participants will: Be randomly assigned to one of two tacrolimus dosing groups at a 1:1 ratio Receive routine immunosuppressive therapy and follow-up for 12 months Undergo blood sampling for tacrolimus concentration, calcineurin activity and multi-omics biomarker detection Complete regular clinical assessments of graft function, adverse events and rejection episodes

Inclusion Criteria: * Sex not restricted, age 18-70 years (inclusive) * First living-donor or deceased-donor kidney transplantation * For deceased-donor transplantation, kidneys from donation after brain death (DBD) * ABO blood type compatibility between donor and recipient * Negative panel reactive antibody (PRA) result within 6 months before surgery * Post-transplant immunosuppressive regimen must be the triple regimen of TAC + mycophenolate mofetil (MMF)/mycophenolate sodium (MPS) + glucocorticoids * More than 3 months after kidney transplantation, with stable graft function * Stable TAC dose regimen and Ctrough results, and stable concomitant medication regimen * Voluntarily participate in the clinical study, fully understand the study and voluntarily sign the informed consent form (ICF), and be able to complete all study procedures Exclusion Criteria: * Multiple organ combined transplantation * History of prior organ transplantation other than the kidney * History of acute rejection after transplantation, or currently receiving treatment for acute rejection * Evidence of active systemic or localized infection * Currently severe diarrhea, vomiting, active peptic ulcer, or other gastrointestinal diseases affecting TAC absorption * Allergy to TAC or its ingredients, or other contraindications precluding the use of TAC * Pregnant women, or women of childbearing potential who plan to become pregnant * Use of strong CYP3A inhibitors or strong inducers within 2 weeks before first dosing, or short-term use during the study * Poor recipient compliance, or other conditions judged by the investigator to make the participant unsuitable for enrollment