FLT3-ITD measurable residual disease from the QuANTUM-First trial.

QuANTUM-First was a randomized trial that demonstrated that the addition of quizartinib, a potent and selective FMS-like tyrosine kinase 3 (FLT3) inhibitor, to induction and consolidation chemotherapy, followed by monotherapy maintenance, improved the survival for patients with newly diagnosed FLT3-internal tandem duplication (FLT3-ITD)-mutated acute myeloid leukemia. We conducted a post hoc analysis of the trial data focusing on measurable residual disease (MRD) as assayed using an amplicon-based next-generation sequencing assay, and on the impact of molecular biomarkers such as FLT3-ITD insertion length and comutations. This is, to our knowledge, the first prospective, randomized trial of an FLT3 inhibitor in newly diagnosed patients in which FLT3-ITD MRD data were collected throughout therapy. We established that quizartinib induces deeper remissions with respect to FLT3-ITD MRD vs placebo, and that the amount of MRD at the completion of induction correlates with relapse and survival. We found that longer FLT3-ITD insertion mutations correlated with worse outcome, quizartinib was beneficial irrespective of insertion mutation length, and the FLT3-ITD MRD assay was more sensitive when bone marrow was used vs peripheral blood. Regardless of the presence of NPM1 (nucleophosmin 1) comutation, quizartinib increased the rates of MRD negativity at the end of induction vs placebo. Finally, comparison of the FLT3-ITD mutation length between the polymerase chain reaction (PCR) with capillary electrophoresis assay obtained at screening and the PCR next-generation sequencing MRD assay performed at the end of induction showed a 96.2% concordance with the exact ITD length. This trial was registered at www.clinicaltrials.gov as #NCT02668653.