Definition

The fumarate salt form of gilteritinib, an orally bioavailable inhibitor of the receptor tyrosine kinases (RTKs) FMS-like tyrosine kinase 3 (FLT3; STK1; FLK2), AXL (UFO; JTK11), anaplastic lymphoma kinase (ALK; CD246), and leukocyte receptor tyrosine kinase (LTK), with potential antineoplastic activity. Upon administration, gilteritinib binds to and inhibits both the wild-type and mutated forms of FLT3, AXL, ALK and LTK. This may result in an inhibition of FLT3-, AXL-, ALK-, and LTK-mediated signal transduction pathways and reduced proliferation in cancer cells that overexpress these RTKs. FLT3, AXL, ALK, and LTK, which are overexpressed or mutated in a variety of cancer cell types, play key roles in tumor cell growth and survival.