Background: Eribulin mesylate is a structurally simplified, synthetic, macrocyclic ketone analogue of Halichondrin B. We investigated the efficacy and safety of eribulin monotherapy versus eribulin plus the oral anti-angiogenesis inhibitor anlotinib in patients with advanced or metastatic breast cancer. Methods: This Phase II study included adult Chinese patients with locally advanced or metastatic breast cancer previously treated with at least two chemotherapy regimens, including both anthracycline- and taxane-based therapy (NCT05206656). Patients were randomized (1:1) to receive eribulin (1.4 mg/m², intravenously, on days 1−8), alone or in combination with anlotinib (12 mg orally once daily), in 21-day cycles. The primary endpoint was investigator-assessed disease control rate (DCR), per RECIST version 1.1. Key secondary endpoints included objective response rate (ORR), progression-free survival (PFS) and safety. Results: Between February 12, 2020, and July 22, 2021, 56 patients were randomized to eribulin (n=32) or eribulin plus anlotinib (n=24) (Table). Sites of metastasis were: bone (60.7%), lung (52.7%), liver (53.6%), lymph nodes (73.2%) and soft tissue (7.1%). Among all patients, the DCR was 66.7% versus 100% (treatment difference, 33.3%; P=0.007), the ORR was 37.0% versus 38.9%, and the median PFS was 3.7 months versus 9.7 months (adjusted hazard ratio, 0.20; 95% CI, 0.04 to 0.91; P=0.04) for patients receiving eribulin versus eribulin plus anlotinib, respectively. Among 36 (64.3%) patients with triple-negative breast cancer, the DCR was 55.6% versus 72.2% (treatment difference, 16.7%; P=0.300) and the median PFS was 3.6 months versus 9.7 months (log rank P=0.030) with eribulin alone versus eribulin plus anlotinib, respectively. The most frequent grade 3-4 adverse events in the eribulin and eribulin plus anlotinib groups were decreased neutrophil count (25.0% [n=8] vs. 29.2% [n=7]) elevated transaminase (6.3% [n=2] vs. 0.0%) and decreased thrombocyte count (3.1% [n=1] vs. 0.0%), respectively. Conclusions: Eribulin plus anlotinib was associated with a significantly better DCR, ORR and PFS than eribulin monotherapy in patients with locally advanced or metastatic breast cancer previously treated with anthracyclines and taxanes. Clinical trial information: NCT05206656.