A Comparative Analysis of Low Dose Grafalon Versus Thymoglobuline As Serotherapy in Hematopoietic Stem Cell Transplant in Pediatric and Young Adult Population

Anti-thymocyte globulin (ATG) forms an essential component of conditioning in hematopoietic stem cell transplantation (HSCT). Due to the shift of donor preference to alternate donors, reliance on rabbit-ATG (rATG) has increased. Two different forms of rATG (Thymoglobuline and Grafalon) are available for clinical use but data to support the use of one over the other is sparse. We retrospectively analyzed data of 144 patients who underwent allogenic-HSCT for benign hematological conditions at our center, from August 2019 to August 2023. Of these, 87 received Grafalon and 57 received Thymoglobuline. The majority (77.7%) underwent HSCT for hemoglobinopathies and all received pre-transplant immunosuppression. Engraftment kinetics was similar in 2 cohorts. Six patients had primary graft failure (PGF). There was no difference in the incidence of PGF stratified by serotherapy. Overall survival(OS) for the cohort was 74.9%. Kaplan-Meier estimate of OSand EFSwas significantly better in Grafalon group than Thymoglobuline (84.4 ± 0.04% vs 64.1% ±0.065%) (-value= 0.04%) and (84.4 ± 0.04% and 61.2%±0.065% (-value = 0.01)). Extensive chronic GVHD was (14%) higher in Thymoglobuline group and (2.3%) in Grafalon. Immune reconstitution at day + 100 was not statistically different between the two groups. On univariate analysis, Thymoglobuline serotherapy (OR (95% CI) =4.665 (1.2-18.04))was associated with increased risk of acute grade III-IV GvHD. In our study, Grafalon tended to have better OS, decreased incidence of acute grade III-IV GvHD, and extensive cGVHD. There was no difference in engraftment kinetics, PGF, and immune reconstitution between 2 cohorts of serotherapy.