The kinase inhibitor Gleevec (imatinib mesylate) has been granted regular approval by the FDA for use in adults following surgical removal of CD117-positive gastrointestinal stromal tumors (GIST), a rare form of cancer that originates in cells of the GI tract wall known as interstitial cells of Cajal (www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm289760.htm).
Gleevec, originally approved in May 2001 for use in patients with advanced Philadelphia chromosome–positive chronic myeloid leukemia, first received accelerated approval for the treatment of advanced or metastatic GIST in 2002. (The FDA’s accelerated approval program allows promising new drugs to be used while confirmatory clinical trials are being conducted.) In 2008, Gleevec gained accelerated approval for adjuvant use in patients with GIST who had potentially curative resection of GIST tumors but who were at increased risk of recurrence. Regular approval for the metastatic GIST indication was granted the same year.
The change in Gleevec’s approval status partially reflects a significant increase in overall patient survival exhibited when the pill is taken for 36 months rather than the standard 12 months. A large randomized clinical study comparing the two treatment periods demonstrated that at 60 months, 92% of patients who underwent Gleevec therapy for 36 months were alive, compared with 82% of patients in the 12-month treatment arm.
The most common side effects observed were edema, nausea, vomiting, muscle cramps, bone or muscle pain, diarrhea, rash, fatigue, and abdominal pain.