Imatinib has exceptional activity in controlling gastrointestinal stromal tumor (GIST) due to inhibition of the constitutively active conformation of KIT and PDGFRA which is found in the majority of patients with GIST.
Gastrointestinal stromal tumor (GIST) is the most frequent sarcoma of the intestinal tract and often shows constitutive activation of either the KIT or PDGFRA receptor tyrosine kinases because of gain-of-function mutation.