Imatinib

Abstract

Imatinib is a protein-tyrosine kinase inhibitor with antitumour effects in patients with gastrointestinal stromal tumour (GIST) that is indicated for the treatment of unresectable and/or metastatic GIST and as adjuvant therapy in patients with KIT-positive GIST. Imatinib binds to and inhibits KIT and platelet-derived growth factor receptor (PDGFR)-α tyrosine kinases, interfering with their downstream tumourogenic processes. Cell lines with KIT mutations that are common in patients with GIST were sensitive to imatinib at low in vitro concentrations. Patients with exon 11 KIT mutations were significantly more likely to have partial tumour responses and longer overall survival (OS) and were significantly less likely to have progression of disease than patients with exon 9 KIT mutations or no detectable KIT or PDGFR mutations. In a large (n > 700) randomized, double-blind, placebo-controlled, multinational trial (ACOSOG [American College of Surgeons Oncology Group] Z9001), patients who received 1 year of adjuvant treatment with oral imatinib 400 mg/day after surgical resection of GIST had significantly longer recurrence-free survival than placebo recipients, with an overall hazard ratio of 0.35 (95% CI 0.22, 0.53) [primary endpoint]. At the time of reporting, there was no significant between-group difference in OS. In patients with GIST who received adjuvant imatinib in this trial, adverse events were mostly of mild or moderate severity; the imatinib treatment group had an almost 2-fold higher rate of US National Cancer Institute Common Toxicity Criteria grade 3 or 4 adverse events than the placebo group.