Imatinib (Glivec, Novartis Pharmaceuticals UK) is a signal-transduction inhibitor that selectively inhibits tyrosine kinases, including the KIT (CD117) receptor that is expressed in GISTs. Imatinib binds to activated KIT (CD117) receptors and blocks the cell-signalling pathway to inhibit uncontrolled cell proliferation. Imatinib has a UK marketing authorisation for the treatment of adults with KIT (CD117)-positive unresectable and/or metastatic malignant GISTs.
The most commonly reported adverse events in trials of imatinib were oedema, fatigue, myalgia, muscle cramps, rash, abdominal pain, vomiting, diarrhoea and nausea. For full details of adverse effects and contraindications, see the summary of product characteristics.
Imatinib is administered orally. The summary of product characteristics recommends 400 mg/day imatinib for the treatment of unresectable and/or metastatic GISTs. It states that there are limited data on the effect of increasing the dose of imatinib from 400 mg/day to 600 or 800 mg/day in people whose disease has progressed at the lower imatinib dose.
Imatinib is available in strengths of 100 mg (60-tablet pack) and 400 mg (30-tablet pack) at a cost of £802.04 and £1,604.08 per pack respectively (excluding VAT; BNF, edition 59). The annual acquisition costs for treatment with imatinib are approximately £19,500 (400 mg/day), £29,300 (600 mg/day) and £39,100 (800 mg/day). Costs may vary in different settings because of negotiated procurement discounts.