Definition

The hydrochloride salt form of pexidartinib, a small-molecule receptor tyrosine kinase (RTK) inhibitor of proto-oncogene receptor tyrosine kinase (KIT), colony-stimulating factor-1 receptor (CSF1R) and FMS-like tyrosine kinase 3 (FLT3), with antineoplastic activity. Upon oral administration, pexidartinib targets, binds to and inhibits phosphorylation of KIT, CSF1R and FLT3 harboring an internal tandem duplication (ITD) mutation. This results in the inhibition of tumor cell proliferation. FLT3, CSF1R and FLT3 are overexpressed or mutated in many cancer cell types and play major roles in tumor cell proliferation and metastasis.