#3148 proteinuria and type of kidney allograft injury identify kidney transplant recipients benefiting most from belatacept conversion

Abstract Background and Aims Belatacept conversion is associated with an improvement in kidney allograft function. Yet, not all kidney transplant recipients (KTRs) seem to benefit equally from this alteration of maintenance immunosuppression. Both type (alloimmune vs. non-alloimmune) and severity (assessed by proteinuria) of kidney allograft injury may impact the functional response to a belatacept conversion. Method We studied 37 KTRs from belatacept conversion to 1-year post-conversion. KTRs were categorized concerning pre-conversion proteinuria: 21 KTRs with low proteinuria (<500 mg/day), 12 KTRs with moderate proteinuria (500–1000 mg/day), and 4 KTRs with high proteinuria (>1000 mg/day). KTRs were analyzed concerning the change of kidney allograft function, change of proteinuria, and type of allograft injury (alloimmune vs. non-alloimmune). Results 17 of 21 KTRs (81%) showed low proteinuria pre- and post-conversion, and 5 of 16 KTRs (31%) with moderate/severe proteinuria pre-conversion showed low proteinuria post-conversion (group 1, n = 22). 8 of 12 KTRs (67%) showed moderate proteinuria pre- and post-conversion, and 1 of 21 KTRs (5%) with low proteinuria pre-conversion developed moderate proteinuria post-conversion (group 2, n = 9). 3 of 4 KTRs (75%) showed high proteinuria pre- and post-conversion, and 3 of 21 KTRs (14%) with low proteinuria pre-conversion developed high proteinuria post-conversion (group 3, n = 6). 16 of 22 KTRs with low proteinuria post-conversion (73%; group 1) showed an increase in eGFR at 1-year post-conversion (≥10% from pre-conversion baseline eGFR) compared to 6 of 9 KTRs (66%, group 2) with moderate proteinuria post-conversion, and 1 of 6 KTRs (17%, group 3) with high proteinuria post-conversion (p = 0.008). Alloimmune injury was assumed in 5 of 22 KTRs (23%, group 1), 3 of 9 KTRs (33%, group 2), and 4 of 6 KTRs (75%, group 3), respectively. Conclusion KTRs with low proteinuria and non-alloimmune injury benefit most from belatacept conversion concerning the improvement of kidney allograft function. While aggravation of proteinuria post-conversion is rare, some KTRs may show improvement of proteinuria post-conversion. If belatacept conversion is still beneficial compared to calcineurin inhibitor-based immunosuppression among KTRs with high proteinuria and alloimmune injury needs to be studied.