Purpose: To determine the efficacy and safety of ZD6474, an orally available inhibitor of vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase with additional activity against the epidermal growth factor receptor (EGFR) tyrosine kinase, in patients with previously treated metastatic breast cancer.
Patients and methods: Eligible patients had histologically confirmed metastatic breast cancer and had received prior treatment with an anthracycline and taxane; measurable disease was required. Patients were enrolled sequentially into one of two dose cohorts, 100 or 300 mg orally once daily; 28 days defined one cycle. The primary end point was objective response rate; pharmacokinetics and serial pharmacodynamic studies were obtained.
Results: Forty-six patients were enrolled between May 2002 and April 2003, and 44 were evaluable for response. Diarrhea was the most commonly reported toxicity and seemed dose related (grade >/=2: 4.5% and 37.5% in the 100 and 300 mg cohorts, respectively). Rash was reported by 26% of patients but was never worse than grade 2. Seven patients in the 300 mg cohort had asymptomatic grade 1 prolongation of the QTc interval. Hypertension requiring treatment was not reported. There were no objective responses; one patient in the 300 mg cohort had stable disease >/=24 weeks. All patients in the 300 mg cohort and 90% of patients in the 100 mg cohort achieved steady-state concentrations exceeding the IC(50) for VEGF inhibition in preclinical models.
Conclusion: ZD6474 monotherapy was generally well tolerated but had limited monotherapy activity in patients with refractory metastatic breast cancer.