GSK2646264 (Compound 44) is a highly effective and specific inhibitor of spleen tyrosine kinase (SYK) with a pIC50 of 7.1. It also inhibits multiple kinases, including LCK (pIC50 5.4), LRRK2 (pIC50 5.4), GSK3beta (pIC50 5.3), JAK2 (pIC50 5), VEGFR2 (pIC50 4.5), Aurora B (pIC50 <4.6), and Aurora A (pIC50 <4.3). Notably, GSK2646264 demonstrates skin penetrability, reaching both the epidermis and dermis [1].