Long term results of a prospective multicenter obervational study on the use of anti-human T-lymphocyte immunoglobulin (ATLG) in unrelated donor transplantation (ATOS study)

Abstract ATOS is a prospective observational study evaluating the outcome of patients receiving anti-human T-lymphocyte immunoglobulin (ATLG) in unrelated donor transplantation. Primary endpoint was severe GvHD and relapse-free survival (SGRFS). GvHD prophylaxis consisted of ATLG and CSA/ MTX or MMF. Outcome was compared to the ATLG arm of our prospective randomized phase III multicenter trial trial (RCT).1, 2 165 patients with haematological malignancies were included. ATLG dose differed between centers (median total ATLG dose of 46 (IQR 32–60, range 15–91) mg/kg). Median follow-up was 70 months. As compared to the ATLG arm of our RCT, patients in ATOS were older, had a more advanced disease status, reduced intensity conditioning, HLA 10/10 match and PBSC transplantation were more frequent, given median ATLG dose was lower, and incidences of acute GvHD °III-IV (0.13), relapse (0.34), non-relapse mortality (0.23), and overall survival rates (0.52) were similar after 5 years. After adjusting for baseline differences, the largest difference in outcome was seen with respect to severe chronic GvHD (ATOS vs ATLG arm RCT: hazard ratio 2.79 [1.20, 6.51], p = 0.017). This long-term, multicenter, experience in routine clinical practice confirms the GvHD-protective effect of ATLG without compromising relapse and non-relapse mortality rates. Clinical Trial Registry: German clinical trials register DRKS00004581