*Purpose: There is limited information on effectiveness of treatment and predictors of graft survival following chronic active antibody mediated rejection (cABMR) in kidney transplant recipients (KTR).

*Methods: We describe response to therapy in 82 consecutive kidney transplant recipients diagnosed with cABMR between 01/2017 and 08/2020. Treatment consisted of pulse steroids/IVIG ± rituximab. A positive response was defined if eGFR returned within 10% of baseline, proteinuria (UPC) decline > 25%, DSA decline > 50%, or MVI (ptc + g) score = 0 at three months. We further identified predictors of graft survival using univariate and multivariable analyses.

*Results: The study included 82 patients. Mean time from transplant to cABMR was 10 ± 7.1 years. Mean ptc, g, C4d, and cg Banff scores at index biopsy were 1.1, 2.1, 0.2, and 2, respectively. Mean eGFR and UPC were 38 mL/min and 1.6 g/g. Thirty (37%) patients lost their allograft during the mean follow-up of 2.4 yrs. At 3-month, eGFR, UPC, DSA, and MVI response rates were 27%, 49%, 7%, and 19% respectively, in the group which received treatment with pulse steroids and IVIG (n=41). The eGFR, UPC, DSA, and MVI response was 66%, 61%, 20%, and 69%, respectively in the group that received steroids, IVIG and rituximab. Univariate analysis identified rituximab (HR=0.13, p=0.0001, 95%Cl 0.05 to 0.34), response in eGFR (HR=0.03, p=0.001, 95% Cl 0.004 to 0.26), UPC (HR=0.38, p=0.01, 95%Cl 0.18 to 0.82), and DSA (HR=0.11, p=0.004, 95%Cl 0.02 to 0.49) as predictors of death-censored graft survival. Multivariate analysis only retained eGFR response (HR=0.12, p=0.01, 95%Cl 0.02 to 0.64).

*Conclusions: Our study suggests that eGFR response at 3-month after initial biopsy is the best predictor of graft survival in patients with cABMR. Short-term histological and immunological response were not independently associated with graft survival.

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