Phase I dose-finding study of eribulin and capecitabine for metastatic breast cancer: JBCRG-18 cape study

Eribulin is a nontaxane microtubule inhibitor with activity in patients with metastatic breast cancer (MBC). We conducted a phase I dose-finding study of eribulin and capecitabine in patients with MBC pretreated with anthracycline and taxane.

Women with MBC aged ≤70 years were enrolled. A 3 + 3 dose escalation design was used: level 0 dosing, eribulin (1.4 mg/m² intravenously on days 1 and 8) plus capecitabine [825 mg/m² orally twice daily (BID)]; 2-weeks-on, 1-week-off in a 21-day cycle. If there were no dose-limiting toxicities (DLTs), level 1 capecitabine dose was 1000 mg/m² BID. The primary objective was to determine maximum tolerated dose, DLTs, and recommended dose (RD). Secondary objectives included pharmacokinetics, safety, and best overall response rate.

Nine women with MBC were enrolled; six at level 0, three at level 1. One patient had grade 4 DLTs at level 0 (serum creatinine 7.65 mg/dL and uric acid 13.4 mg/dL), considered associated with study drugs. Level 1 dosing was taken as the RD. Neutropenia was the most common ≥grade 3 toxicity. Pharmacokinetic parameters of eribulin were not influenced by co-administration of capecitabine. Of three patients in level 1, one achieved partial response and one had prolonged stable disease.

Eribulin with capecitabine in the level 1 dosing schedule was associated with manageable toxicities and promising clinical activity. This combination is recommended for phase II investigation.