Abstract BACKGROUND AND AIMS Conversion to a belatacept regimen after transplant seems to be safe. However, no studies have reported the long-term efficacy and safety outcomes after conversion to a belatacept regimen and compared it with patients treated with a CNI-based regimen in kidney transplantation. This study aims to investigate the long-term outcomes of patients converted to a belatacept regimen compared with matched patients under a CNI regimen. METHOD Kidney transplant recipients transplanted between 1998 and 2019 from two French academic transplant canters were recruited. We used a propensity score to match with a 1:1 ratio of patients at the time of the biopsy, which indicates the conversion to a belatacept regimen to control patients under a CNI regimen with a biopsy after transplant. We used 11 parameters associated with graft survival for the matching, 4 baseline transplant characteristics (recipient age, prior transplant status, donor type and dgf) and 7 at time of the biopsy (time after transplant, eGFR, proteinuria, DSA and Banff scores cv, ah, IFTA). Transplant outcomes defined by graft and patient survival, as well as safety outcomes, were compared between the matched patients. RESULTS From 3215 kidney transplant recipients transplanted during the study period with the inclusion criteria (311 patients under belatacept and 2904 patients under CNI). A total of 243 patients under belatacept were matched with 243 controls under CNI. All prognostic parameters were well-balanced before conversion between the two groups, with a mean age of 54.7 ± 15.1 years (P = .4543), a mean time of 2.2 ± 3.2 years after transplant (P = .586), a mean eGFR of 33.0 ± 13.3 mL/min/1.73 m2 (P = .976), a median proteinuria of 0.23 (0.12–0.50) g/g (P = .278) and 30.9% of positive anti-HLA DSA (P = 1.0) in the belatacept group. After a mean follow-up time after conversion of 4.4 ± 2.5 years, 36 (14.8%) patients lost their grafts and 39 (16.0%) patients died in the belatacept cohort. After conversion to a belatacept regimen, the graft survival was significantly improved when we compared with the matched patients’ under CNI P < .0001 (Fig. 1). Patients converted to Belatacept showed a lower death rate of 16.0% compared with 30.0% for the CNI treated patients (P < .001). The safety outcomes showed a similar rate of biopsy proven rejection (P = .08), major adverse cardiovascular events and cancer between the two groups, while a significant higher rate of CMV disease was observed among the belatacept treated patients P < .01). CONCLUSION This study confirms that conversion to belatacept post-transplant is associated with improved long-term graft outcome and acceptable safety. Conversion to belatacept after transplant should be considered as a valuable therapeutic option for kidney recipients.