Individualized dose of anti-thymocyte globulin based on weight and pre-transplantation lymphocyte counts in pediatric patients: a single center experience

Anti-thymocyte globulin (ATG) has become a standard in preventing GVHD in related and unrelated donor transplantation, but there is no consensus on the best administration schedule. The PARACHUTE trial reported excellent CD4 immune reconstitution (CD4 IR) using a dosing schedule based on the patient's weight and pre-conditioning absolute lymphocyte count (ALC). In 2015 we introduced the PARACHUTE dosing schedule for pediatric patients at our center. One hundred one patients were transplanted for malignant and non-malignant diseases. In this non-concurrent cohort CD4 IR+, defined by a single CD4 count >50/µL on day 90, was seen in 81% of patients. The incidence of grade II-IV and III to IV aGvHD was 26.6% and 15.3% and 5% for cGvHD with no severe cases. We found no difference in aGvHD between donor type and stem cell sources. Five-year EFS and OS were 77.5% and 83.5%. Grade III-IV GFRS was 75.2%. CD4 IR+ patients had better EFS (93.1% vs. 77.7%, p = 0.04) and lower non-relapse mortality (2.7% vs. 22.2%, p = 0.002). The PARACHUTE ATG dosing schedule individualized by weight and ALC results in good early immune reconstitution, low incidence of cGvHD, and favorable survival for patients with different disease groups, donor types, and stem cell sources.