Comparison of Different Rabbit Anti-Thymocyte Globulin Formulations in Allogeneic Stem Cell Transplantation: Systematic Literature Review and Network Meta-Analysis

Since 2000, various phase III randomized controlled trials (RCTs) have investigated the efficacy of rabbit antithymocyte globulin (ATG) in patients following allogeneic stem cell transplantation (allo-SCT). Comparisons of different ATG formulations are lacking, however. Our aim was to synthesize all published efficacy evidence to enable a comparison of all available formulations of rabbit ATG in the allo-SCT setting. We performed a systematic literature review to identify all available phase III RCT evidence. We searched the Cochrane Library, MEDLINE, MEDLINE In-Process, and the website www.ClinicalTrials.gov. In addition, a trial presented at the Annual Meeting of the American Society of Hematology 2016 was added to include the most recent evidence. We identified a total of 6 RCTs, including 2 formulations: anti-T lymphocyte globulin (ATLG; Grafalon, Neovii Biotech, Lexington, MA) and polyclonal globulin immunized with human thymocytes (Thymoglobulin [Thymo]; Genzyme-Sanofi, Cambridge, MA). The evidence was synthesized using a conventional network meta-analysis (NMA). The best treatment for preventing graft-versus-host disease (GVHD) was ATLG, which had a more favorable hazard ratio (HR) compared with standard treatment (chronic GVHD: HR, .42; 95% confidence interval [CI], .31 to .56; acute GVHD grade II-IV: HR, .54; 95% CI, .39 to .73; acute GVHD grade III-IV: HR, .50; 95% CI, .29 to .86), whereas both ATLG and Thymo were at least similarly effective in terms of transplantation-related mortality (TRM) (ATLG: HR, .90; 95% CI, .61 to 1.32; Thymo: HR, .90; 95% CI, .56 to 1.44). Thymo tended to be the better treatment option regarding overall survival (OS) (HR, .86; 95% CI, .59 to 1.26). Our NMA provides the first report of the relative efficacy of all available rabbit ATG formulations in patients undergoing allo-SCT. Until additional data from randomized head-to-head comparisons are available, based on the present analysis, ATLG seems to be the best option to prevent chronic and acute GVHD. Both formulations show similar efficacy in terms of TRM, whereas Thymo appears to be the better treatment option in terms of OS.