Allogeneic hematopoietic cell transplantation(allo-HCT) is a curative therapy for
hematological disorders and the ATG is commonly used as prophylaxis for GVHD. Previous
studies have indicated that there is an optimal dosage for ATG administration, if the
dosage is too high, it may affect engraftment and increase the risk of infection and
relapse, whereas an inadequate dosage may increase the risk of acute or chronic GVHD,
there is still controversy about the optimal dose of ATG, its pharmacologic effects on
clinical outcomes of HSCT are associated with donor source, human leukocyte antigen (HLA)
disparity, conditioning intensity, and GVHD prophylaxis, so although has been
investigated for decades, the optimal dosage of ATG in allogeneic hematopoietic stem cell
transplantation remains undetermined.
ATG exerts pharmacologic effects in its active form upon binding to lymphocytes, and its
exposure is presented as the area under the concentration-time curve (AUC). To obtain
plasma active ATG concentrations, investigators developed an active ATG concentration
detection method based on flow-cytometry with HUT-78 T-cells. In previous study,
investigators quantified active ATG exposure in 106 haploidentical peripheral blood stem
cell transplantation (haplo-PBSCT) recipients, who received a conventional fixed dose of
10 mg/kg ATG during conditioning, the optimal concentration range of active ATG-AUC was
determined through the application of machine learning methods, was found to be 100-148.5
× 10^3 UE·d/L. This concentration range was associated with a reduction in CMV/EBV
reactivation, without an increase in acute GVHD or malignant disease relapse.
Mathematical function was then exploited to determine the total targeted ATG dose on
-3days to -2days based on concentrations of active ATG on -5daysto -4days. Based on this
function, a dosing strategy was established that aimed to maintain the active ATG-AUC
within the optimal range. To validate this individualized dosing strategy, investigators
conducted a single-arm, phase 2 trial, demonstrating that this strategy could reduce
CMV/EBV reactivation and improve survival without increasing the incidence of GVHD after
haplo-PBSCT. Given the similarity between unrelated donor hematopoietic stem cell
transplantation (URD-HSCT) and haploidentical hematopoietic stem cell transplantation
(haplo-HSCT) in terms of conditioning regimens, GVHD prophylaxis, and supportive
therapies, as well as the conventional fixed dose of 10mg/kg employed in both settings,
investigators have designed and conducted a single-center, prospective, single-arm
clinical trial. The aim of this trial is to translate the individualized ATG dosing
strategy, which was originally developed based on ATG concentration monitoring in
haplo-HSCT patients, to URD-HSCT, with the goal of further validating its effectiveness.