Figure 1. Likely Mode of Action of STI571.

The left-hand panel shows the BCR-ABL oncoprotein with a molecule of ATP in the kinase pocket. The relevant substrate is phosphorylated on a tyrosine residue and, in its phosphorylated state, can then interact with other downstream effector molecules. When STI571 occupies the kinase pocket (right-hand panel), the action of ATP is inhibited, and the substrate cannot be phosphorylated.