Besides SYK/ZAP70, fostamatinib also targets FLT3, LCK, and LYN (according to the manufacturer; Fostamatinib (R788), Syk/FLT3 Inhibitor, MedChemExpress), which might explain the residual sensitivity of T-ALL cells to the inhibitor. This evidence concerns the gene ZAP70 and acute lymphoblastic leukemia.