Stelljes, Matthias

Abstract We conducted a post hoc analysis of data from Blood and Marrow Transplant Clinical Trials Network 1506 (MORPHO), a randomized trial of gilteritinib vs placebo as posttransplantation maintenance for patients with FLT3-ITD–mutated acute myeloid leukemia (AML) undergoing allogeneic hematopoietic cell transplantation (HCT), focusing the interactions between conditioning regimen intensity, measurable residual disease (MRD), and NPM1 comutation status reported from diagnosis. Comparing FLT3-ITD MRD before and after conditioning, there was no difference between myeloablative conditioning (MAC) and reduced-intensity conditioning (RIC) in eradication or reduction of FLT3-ITD MRD. For participants who were FLT3-ITD MRD negative before HCT, there was no difference in the cumulative incidence of relapse during follow-up between those receiving MAC vs RIC. NPM1 comutation was associated with the largest magnitude of relapse-free survival benefit from post-HCT gilteritinib, and in these participants, post-HCT gilteritinib in the setting of RIC appeared to be as effective as MAC at preventing relapse. MAC appeared superior to RIC in preventing relapse only in participants who were NPM1 wild type at diagnosis and FLT3-ITD MRD positive before HCT. Our findings suggest that only a subset of patients with FLT3-ITD AML undergoing HCT may benefit from MAC and that, similar to AML therapy before HCT, the intensity of the HCT regimen should be adapted according to the molecular features of the disease. This trial was registered at www.clinicaltrials.gov as #NCT02997202.

Abstract BMT CTN (Blood and Marrow Transplant Clinical Trials Network) 1506 (“MORPHO”) was a randomized study of gilteritinib compared with placebo as maintenance therapy after hematopoietic cell transplantation (HCT) for patients with FLT3-ITD–mutated acute myeloid leukemia (AML). A key secondary end point was to determine the impact on survival of before and/or after HCT measurable residual disease (MRD), as determined using a highly sensitive assay for FLT3-ITD mutations. Generally, gilteritinib maintenance therapy was associated with improved relapse-free survival (RFS) for participants with detectable peri-HCT MRD, whereas no benefit was evident for those lacking detectable MRD. We conducted a post hoc analysis of the data and found that the level of MRD detected with this approach correlated remarkably with RFS and relapse risk, and that MRD detectable at any level negatively affected RFS. In the placebo arm, 42.2% of participants with detectable FLT3-ITD MRD relapsed compared with 13.4% of those without detectable MRD. We found that 14.8% of participants had multiple FLT3-ITD clones detected as MRD and had worse survival irrespective of treatment arm. Finally, we examined the kinetics of FLT3-ITD clonal relapse or eradication and found that participants on the placebo arm with detectable MRD relapsed rapidly after HCT, often within a few weeks. MRD-positive participants on the gilteritinib arm relapsed either with FLT3 wild-type clones (assessed by capillary electrophoresis), after cessation of gilteritinib with persistent MRD, or on progression of multiclonal disease. These data demonstrate the potential of FLT3-ITD MRD to guide therapy with gilteritinib for this subtype of AML. This trial was registered at www.clinicaltrials.gov as #NCT02997202.