– 5-Iodotubercidin (Itu) has been shown to inhibit mitogen-activated protein kinase (ERK2) (Ki = 525 nM), adenosine kinase (ADK) (Ki = 30 nM), casein kinases 1 & 2 (CSNK1A1 & CSNK2A1), protein kinase A (PKA) and insulin receptor kinase (IC50 ranging from 0.