Gleevec (imatinib mesylate)

Gleevec has been approved for the treatment of patients with positive inoperable and/or metastatic malignant gastrointestinal stromal tumors (GISTs). This is not the first approval for Novartis' Gleevec; in May 2001, the drug received approval for the treatment of chronic myeloid leukemia (CML).

Gleevec is a signal transduction inhibitor that works by targeting the activity of enzymes called tyrosine kinases. The activity of one of these tyrosine kinases, known as c-kit, is thought to drive the growth and division of most GISTs.

Gleevec's approval was supported by data from an open-label, multinational study conducted in subjects with unresectable or metastatic malignant GISTs. In the trial, 147 subjects were randomized to receive 400 mg or 600 mg orally q.d. for up to 24 months. Subjects in the trial were between 18 and 83 years of age, and they had a pathologic diagnosis of Kit-positive unresectable and/or metastatic malignant GIST. Results showed an overall response rate of 38% (400mg=33%; 600mg=43%) based on confirmed partial responses at the time of data cut-off for submission.

In the GIST clinical trial, the most common adverse events included the following:

• Edema
• Nausea
• Diarrhea
• Abdominal pain
• Muscle cramps
• Fatigue
• Rash

Additionally, seven subjects in the trial were reported to have gastrointestinal bleeds and/or intratumoral bleeds.

Imatinib is an inhibitor of the receptor tyrosine kinases for platelet-derived growth factor (PDGF) and stem cell factor (SCF), c-kit, and inhibits PDGF- and SCF-mediated cellular events. In vitro, imatinib inhibits proliferation and induces apoptosis in GIST cells, which express an activating c-kit mutation. (from Gleevec Prescribing Information).

The brand name Gleevec is used in the United States, whereas the drug is referred to as Glivec outside the United States.

For additional information on Gleevec, please visit www.gleevec.com.