Furthermore, response to gilteritinib, as defined by leukemia growth delay (LGD) [27, 29, 50], was correlated with bulk FLT3 surface protein and gene expression (Figs. 6B and S10B), suggesting that FLT3 could be used as a predictive marker of response to gilteritinib in ETP-ALL. Here, FLT3 is linked to leukemia.