Study to Evaluate the Efficacy and Safety of Eribulin Mesylate in Combination With Pembrolizumab in Participants With Metastatic Triple-Negative Breast Cancer (mTNBC)

Eribulin Mesylate will be administered as a 1.4 milligram per square meter (mg/m\^2) IV (intravenous) infusion on Day 1 and Day 8 of each 21-day cycle in the presence of clinical benefit until intercurrent illness, unacceptable toxicity, or disease progression occurs, or until the participant withdraws consent.

Pembrolizumab will be administered as a 200 milligram (mg) IV infusion on Day 1 of each 21-day cycle in the presence of clinical benefit until intercurrent illness, unacceptable toxicity, or disease progression occurs, or until the participant withdraws consent.