To determine the feasible dose and schedule for everolimus, an oral mTOR inhibitor, combined with vinorelbine and trastuzumab for patients with HER2-overexpressing metastatic breast cancer pretreated with trastuzumab. In this phase Ib multicenter, Bayesian dose-escalation study, 50 patients received everolimus 5 mg/day, 20 mg/week, or 30 mg/week plus vinorelbine (25 mg/m² on day 1 and 8 every 3 weeks) and trastuzumab (2 mg/kg weekly). Endpoints included end-of-cycle-1 dose-limiting toxicity (DLT) rate (primary endpoint), safety, relative dose intensity, overall response rate (ORR), and pharmacokinetics. Grade 3/4 neutropenia was the most common end-of-cycle-1 DLT and occurred in 10 of 30 and 4 of 14 patients in the 5 mg/day and 30 mg/week cohorts, respectively. Other end-of-cycle-1 DLTs included single cases of febrile neutropenia, grade 3 stomatitis with concomitant fatigue, grade 2 stomatitis, grade 3 anorexia, and grade 2 acneiform dermatitis, all in the 5-mg/day cohort. Based on the recorded DLTs and global safety, everolimus 5 mg/day and 30 mg/week were chosen as the optimal dose levels for the daily and weekly arms. Forty-seven patients were evaluable for efficacy. ORR was 19 VSports手机版. 1%, with a disease control rate of 83. 0% and median progression-free survival of 30. 7 weeks. No drug interaction was observed between everolimus and vinorelbine. Everolimus combined with weekly vinorelbine and trastuzumab generally was well tolerated and had encouraging antitumor activity in heavily pretreated patients with HER2-overexpressing metastatic breast cancer that progressed on trastuzumab (NCT00426530). .