Rabbit Anti-Thymocyte Globulin for Treatment of Corticosteroid Refractory Acute Cellular Rejection After Lung Transplantation

Abstract

<h3>Purpose</h3> Chronic Lung Allograft Dysfunction (CLAD) is the major cause of graft failure and death after the first-year post-transplant. Acute Cellular Rejection (ACR) of grade A2 or higher is a major risk factor for CLAD. Rabbit anti-thymocyte globulin (rATG) is often used when ACR is nonresponsive to pulse-dose corticosteroids. Data is lacking regarding the impact of rATG on steroid refractory ACR (rACR) after lung transplantation. The objective of this retrospective study was to evaluate the use of rATG for rACR in lung transplant recipients and define its success in improving or resolving ACR. <h3>Methods</h3> Adult patients were included if they had received a single or double lung transplant as identified by ICD 9 and 10 procedure codes between January 2010 and August 2019 and had received rATG after the date of transplantation through September 2020. rATG treatment was identified using medication charge data. Patients were included if rATG was administered for ACR. The primary endpoint was the incidence of ACR on follow-up transbronchial biopsy. ACR was classified by complete resolution, improvement but not complete resolution, or no response in A grade. Secondary endpoints included freedom from ACR at one-year post-rATG, CLAD incidence or progression at one-year post-rATG, and all-cause mortality at one-year post-rATG. <h3>Results</h3> 112 patients were included in the primary outcome analysis. 60.2% of patients had a complete resolution, 22.1% had an improvement but not complete resolution, and 17.8% had no response on follow-up biopsy. Mean A grade one-year post-rATG was 0.51 in complete responders, 1.01 in partial responders, and 2.19 in non-responders (p < 0.001). There was no statistical difference in new or worsening CLAD depending on response to rATG (17% vs 40% vs 30%; p = 0.09). All-cause mortality was significantly lower in patients who had a complete histologic response to rATG (14.9% vs 40% in partial responders, and 30% in non-responders (p < 0.01). <h3>Conclusion</h3> rATG appears to be an effective treatment of rACR in lung transplant recipients. Response to rATG appears to be sustained at one-year post-rATG. Patients that do not respond to rATG for rACR may have an increased risk of mortality.