Purpose: As monotherapies, eribulin (chemotherapy) and pembrolizumab (immunotherapy) have shown promise for patients with metastatic triple-negative breast cancer (mTNBC). This phase Ib/II study examined eribulin plus pembrolizumab as a potential mTNBC treatment in first-line and later-line settings.
Patients and methods: In this open-label, single-arm, phase Ib/II study, eligible patients had mTNBC, measurable disease, and ≤2 prior systemic anticancer therapies in the metastatic setting. Patients were enrolled by number of prior systemic anticancer therapies (stratum 1: 0 vs stratum 2: 1-2) in the metastatic setting and further analyzed by tumor programmed death-ligand 1 (PD-L1) expression status. All patients received intravenous eribulin 1.4 mg/m2 on day 1 and day 8, plus intravenous pembrolizumab 200 mg on day 1, of 21-day cycles. The primary objectives were the safety, tolerability, and objective response rate (ORR) of this combination.
Results: The study included 167 patients (phase Ib, n = 7; phase II, n = 160). The most common treatment-emergent adverse events were fatigue (66%), nausea (58%), peripheral sensory neuropathy (41%), alopecia (40%), and constipation (37%). ORRs were 25.8% [95% confidence interval (CI): 15.8-38.0] for stratum 1 (n = 66) and 21.8% (95% CI: 14.2-31.1) for stratum 2 (n = 101). Patients with PD-L1-positive tumors (combined positive score ≥1) had numerically higher ORR than those with PD-L1-negative tumors, particularly in stratum 1 [stratum 1: 34.5% (95% CI: 17.9-54.3) vs 16.1% (95% CI: 5.5-33.7); stratum 2, 24.4% (95% CI: 12.9-39.5) vs 18.2% (95% CI: 8.2-32.7)].
Conclusions: Eribulin plus pembrolizumab was generally well tolerated and showed promising antitumor activity in mTNBC. Efficacy outcomes appeared influenced by line of therapy and PD-L1 status.
©2021 American Association for Cancer Research.