Vascular endothelial growth factor tyrosine kinase inhibitors

Tyrosine kinase inhibitors of the vascular endothelial growth factor (VEGF) receptor remain an attractive area of research in cancer. Merck has had an ongoing programme related to small-molecule inhibitors of the VEGF receptor kinase and has filed numerous applications in this area. The present application relates to a salt of a compound claimed explicitly in a previous application from Merck. The present application is focused on hydrochloride salts of this compound and claims several polymorphs of this salt. Such applications directed to specific polymorphs usually indicate a compound that may be of significant interest to the Merck VEGF programme.