FLT3 and leukemia: Next-generation sequencing of paired samples (drug-naïve sensitive and relapse drug-resistant samples) from R/R FLT3-ITD AML patients who relapsed from FLT3 inhibitors crenolanib [33] or gilteritinib [34] demonstrated the emergence or expansion of leukaemia clones either as subclones of the FLT3-ITD clone or new wildtype FLT3 clones.