*Purpose: Antibody-mediated rejection (AMR) is cause of significant morbidity and mortality in lung transplant recipients (LTRs). An optimal therapeutic regimen is still lacking. Recent evidence suggests that belatacept, a costimulation blockade antibody, could prevent the generation of donor-specific antibodies (DSAs) in kidney transplant recipients. However, its use in LTRs has not been evaluated. We hypothesized that a multimodal approach including belatacept could have a beneficial impact on LTRs with AMR.

*Methods: In the current study, we retrospectively analyzed the clinical outcomes of LTRs with AMR who received as first-line intervention a combination of plasmapheresis (PLEX), IVIG, rituximab, and carfilzomib with belatacept (group 1, n=10) or without (group 2, n=9). LTRs who received previous therapeutic interventions were excluded. Changes in forced expiratory volume at 1 second (FEV1) and circulating DSAs 90 days post-treatment were collected. Kaplan-Meier method was used to analyze survival using composite endpoint of death or re-transplantation at 30, 90 days, and 1 year.

*Results: The two groups were similar in age, sex, and underlying disease as shown in table 1. All patients received a bilateral lung transplant (BOLT) and were on triple-drug maintenance immunosuppression. No difference in pre-transplant calculated panel-reactive antibody was noted. There was no difference in FEV1 at baseline (p=0.6) and at AMR diagnosis (figure 1) (p= 0.8, respectively). AMR was diagnosed at a median of 14.5 months (interquartile range[IQR], 2-26) in group 1 and of 16 months (IQR, 7-53) in group 2. All LTRs developed class II DSAs. There was no significant difference in FEV1 at 90 days post-treatment between the 2 groups (figure 1) (p=0.6). In each group 3 patients obtained clearance of circulating DSAs at 90 days. There was no difference in survival between the 2 groups (log-rank p= 0.3). A total of 7 LTRs developed chronic lung allograft dysfunction (CLAD), 4 died and 3 received second BOLT (table 1)

*Conclusions: Our study suggests that belatacept might not have a significant impact on the management of AMR in LTRs. However, additional prospective studies are needed to define optimal therapeutic interventions.

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