Cisplatin and carboplatin have antitumor activity in breast cancer. Satraplatin, an orally bioavailable platinum analog, offers a potential alternative to intravenous chemotherapy. We conducted a multicenter phase II study of this agent as first- or second-line treatment of metastatic breast cancer. Satraplatin 80 mg/m(2) was taken PO Days 1-5 q 21 days in cycles 1 and 2, and if tolerated, increased to 100 mg/m(2) for subsequent cycles. Restaging studies to assess response were performed after every 2 cycles. Between November 2005 and March 2006, 40 patients were enrolled. Baseline characteristics: 48% prior adjuvant chemotherapy, 60% prior chemotherapy for MBC; median age, 62 years (ranges 43-83), 58% ER+/PR+, 23% ER+/PR-, 18% ER-/PR-/HER2-, and 5% HER2+. In 31 patients with measurable disease, there were two partial responses (PR; 6%; 95% CI 0, 15.2); and four patients (13%) had SD > or =6 months for a clinical benefit rate of 19%. Among the subanalysis of seven triple-negative patients with measurable disease, there were 2 SD and 2 PD. Median survival was 15 months and median progression-free survival was 2.7 months. The most common grade 3-4 toxicities were neutropenia (28%) and thrombocytopenia (25%). AEs leading to treatment discontinuation were nausea (n = 3), thrombocytopenia (n = 3), fever (n = 2), and vomiting (n = 2). This phase II study demonstrates oral satraplatin has limited activity as a single agent for MBC. Satraplatin, at a lower dose used in this study, could be combined with other chemotherapy agents in future trials in breast cancer.