New Data Support the Efficacy and Safety Profile of Single-Agent Sunitinib in the Treatment of Imatinib-Resistant GIST

Pfizer recently announced new follow-up data from a worldwide expanded access program supporting the efficacy and safety of single-agent, oral sunitinib malate (Sutent) in the treatment of imatinib (Gleevec)-resistant or intolerant gastrointestinal stromal tumor (GIST). These data were presented at the annual ASCO meeting in Chicago (abstract 10548).

As of December 2007, 1,117 patients in this open-label study had received treatment with sunitinib:

• Sunitinib was generally well tolerated in patients with advanced GIST who were resistant to or intolerant of imatinib, with a safety profile consistent with that observed with sunitinib in other GIST trials.

• Median estimated time to progression was 41 weeks.

• Median estimated overall survival was 75 weeks, with 50% of patients alive at time of data cutoff.

• In patients less than 59 years, median estimated overall survival was 85 vs 65 weeks in patients 59 years or older.

Sunitinib vs High-Dose Imatinib in Low-Dose Imatinib–Resistant GIST

While many patients initially benefit from treatment with imatinib mesylate, the current first-line treatment for advanced GIST, many develop either primary or secondary resistance to the agent during the course of treatment. Pfizer has initiated a multicenter, head-to-head, phase IIIB trial, to evaluate the efficacy and safety of sunitinib (37.5 mg/d given on a continuous dosing schedule) compared with high-dose (800 mg) imatinib in GIST patients whose cancer progressed on the lower dose (400 mg) of imatinib.

Results from the lead-in safety portion of this study, which included six patients, were presented at ASCO (abstract 10557). The data show that sunitinib administered 24 hours after the last dose of imatinib appears to be generally well tolerated. No treatment related adverse events at or above grade 3 were observed at day 7 and day 14 of sunitinib therapy following transition from imatinib within 24 hours.