"SU11248 Shows Activity in Tough-to-Treat Breast Cancer: Presented at ECCO"
By Jill Stein
PARIS, FRANCE -- October 31, 2005 -- SU11248 has demonstrated single-agent activity in patients with metastatic breast cancer (MBC) that is refractory to prior therapies, researchers reported here at the 13[th Annual Meeting of the European Cancer Conference (ECCO).
SU11248 is an oral multitargeted tyrosine kinase inhibitor, which selectively inhibits vascular endothelial growth factor (VEGF) receptor, platelet-derived growth factor (PDGF) receptor, stem cell factor receptor, Fms-like tyrosine kinase-3 receptor, and glial cell-line-derived neurotrophic factor receptor.
In preclinical models, SU11248 demonstrated both antitumor and antiangiogenic activity.
Kathy Miller, MD, assistant professor of medicine, Indiana University School of Medicine, Indianapolis, Indiana, presented results of an open-label, phase 2 trial in which 64 patients with previously treated MBC received SU11248 50 mg qd orally for 4 weeks followed by 2 weeks without treatment.
The study included women with unresectable, histologically-confirmed breast adenocarcinoma that did not respond to prior anthracycline and taxane therapy and at least 2 other regimens. Subjects also had measurable disease, an ECOG performance score of 0/1, adequate organ function, normal left ventricular ejection fraction, and no dysrhythmias.
The primary endpoint was objective response rate according to Response Evaluation Criteria in Solid Tumours (RECIST) criteria including complete and partial response.
Tumor response was assessed at week 10 and then every 12 weeks. Dose reduction based on toxicity was permitted.
Efficacy data available in all patients showed that 11% achieved a partial response, and 5% achieved stable disease for at least 6 months.
Median time to progression for the study population was 10 weeks.
The researchers found no correlation between response to treatment and steroid receptor or HER2 status.
A response was observed in patients who had visceral as well as superficial disease at the time of enrollment.
Safety data available in all patients showed that fatigue was the most frequently reported nonhematologic treatment-related adverse effect. Grade 2 severity was reported in most patients who experienced fatigue.
"Overall, SU11248 was associated with acceptable tolerability," Dr. Miller said. "Treatment modifications to toxicity were required in about half of patients, and adverse events were manageable."
Nonhematologic toxicities included grade 1 to 2 diarrhea (56%), mouth pain distinct from mucositis (49%), fatigue (47%), nausea (44%), skin discoloration (27%), headache (26%), and hypertension (17%). Grade 3 hematologic toxicity included neutropenia (39%), anemia (2%), and thrombocytopenia (15%).
Dr. Miller said that the positive results obtained in this study indicate that further investigations with SU11248 in MBC are warranted.
The study was sponsored by Pfizer.
[Presentation title: Safety and Efficacy of Sunitinib Malate (SU11248) in Patients With Refractory Metastatic Breast Cancer (MBC): Preliminary Results from a Phase II Study. Abstract 406]
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