Short- and long-term outcomes of anti-thymocyte globulin-based regimen for acute antibody-mediated rejection after lung transplantation

BACKGROUND: Antibody-mediated rejection (AMR) remains a major barrier to successful lung transplantation (LTx). Despite advances in donor-specific alloantibody (DSA) detection, effective treatments are limited, with current management largely empirical. Acute clinical AMR, marked by rapid graft dysfunction, demands urgent intervention. In Japan, where approved therapies for AMR were historically limited, rabbit anti-thymocyte globulin (rATG) has been adopted as a treatment option. METHODS: This retrospective study analyzed 11 patients who developed acute AMR within three months after LTx at Okayama University Hospital between 2013 and 2023. Diagnosis (ISHLT possible AMR) was based on acute graft dysfunction unresponsive to steroids, positive DSA, and exclusion of infection, without histological confirmation due to procedural risk. rATG (1.5 mg/kg/day for 7 days) was administered, along with intravenous immunoglobulin (IVIG), plasma exchange (PLEX), and rituximab when indicated. Outcomes included DSA clearance, clinical response, survival, and adverse events. RESULTS: Remission was achieved in 64% of patients, with 36% not requiring PLEX and 64% not receiving rituximab. Early rATG treatment correlated with favorable outcomes, whereas delayed therapy resulted in poorer responses. Six patients (55%) survived without chronic lung allograft dysfunction (CLAD) for over one year. Adverse events included cytomegalovirus infection (91%), bacterial pneumonia (36%), fungal infection (18%), and malignancy (18%). CONCLUSIONS: rATG was effective for acute possible AMR management, particularly when initiated early. Some patients achieved remission without adjunct therapy, indicating rATG's potent immunosuppressive activity. However, frequent infectious complications emphasize the need for optimized dosing and further studies to validate its safety and long-term efficacy.