We assessed the activity and tolerability of a cisplatin, epirubicin, and lonidamine combination regimen as first-line chemotherapy in 28 advanced breast cancer patients. The schedule of treatment was as follows: 60 mg/ m2 epirubicin followed by 40 mg/m2 cisplatin given on days 1 and 2 every 21 days, with 450 mg lonidamine being given per os (three tablets) on days of chemotherapy administration and in the period intervening between one cycle and the next. Patients received a median of 5 (range 1-6) cycles. Overall, 22 patients were evaluable for response and 28, for toxicity. Four patients refused to continue the treatment after the first course, one was lost to follow-up, and one died due to toxicity (septic shock). The incidence of grade 3/4 nausea and vomiting was found to be greater than that expected with epirubicin and lonidamine alone. The addition of cisplatin resulted in an increase in platelet and hemoglobin toxicities, whereas the WBC toxicity did not differ from that expected with epirubicin and lonidamine. The hematological toxicity was found to be cumulative, leading to treatment delay in about 50% of patients at the fifth and sixth courses. The activity of this cytotoxic regimen was noteworthy, with the overall response rate being 81.8% (31.8% complete responses and 50.0% partial responses) in evaluable patients. This response rate decreased to 64.2% when all registered patients were included according to an intent-to-treat analysis. In conclusion, the association of cisplatin, epirubicin, and lonidamine given on the schedule described herein, appears to be very active but substantially toxic. We are now testing this combination in a randomized comparison, with the cisplatin dose being reduced to 30 mg/m2 given on days 1 and 2.