Proteasome inhibitor (PI) containing regimens treat mixed acute rejection (MAR) at least in part due to elimination of donor specific antibody (DSA) and via effects on T cells. Rabbit anti-thymocyte globulin (rATG) is a polyclonal antibody that results in T and B cell depletion and is used in the treatment of acute cellular rejection (ACR). There may be a role in combination therapy with these two agents in the setting of MAR. The purpose of this evaluation was to assess whether the addition of rATG enhanced PI-based therapy in patients with late MAR.

Methods:

Renal transplant recipients experiencing late MAR (>6 months post-RTx) from 1/2005 – 08/2015 treated with a PI-based regimen +/- rATG were assessed. Patients not receiving rATG received steroid pulse therapy and a single dose of rituximab. The Banff Criteria was utilized to diagnose AMR and ACR. MAR was defined as having both ACR and AMR. Post-treatment Banff component score responses and serum creatinine changes were assessed with the Mann Whitney U test. Kaplan Meier curves with logrank comparisons assessed death-censored graft survival (DCGS).

Results:

39 patients were included (adjunct rATG = 25; no adjunct rATG = 14): female (71.8%) and Caucasian (66.7%) with a mean age of 39.9 years (+14.2 years). Baseline demographics were similar between groups. Results presented in Table 1, Figure 1, Figure 2.

Conclusions:

1) No difference in Banff component score reduction, percent iDSA reduction, and DCGS with the addition of rATG to a PI-based regimen.

2) Late MAR remains a difficult clinical entity to effectively treat and merits additional clinical research.

CITATION INFORMATION: Lichvar A, Leino A, Tremblay S, Shields A, Paterno F, Govil A, Anand M, Diwan T, Kremer J, Alloway R, Woodle E. Adjunctive Thymoglobulin with Proteasome Inhibitor Based Treatment of Late Mixed Acute Rejection. Am J Transplant. 2017;17 (suppl 3).

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