LBA4Background: Olaparib is an oral PARP inhibitor with anti-tumor activity in HER2-negative mBC with a gBRCAm (NCT00494234). OlympiAD (NCT02000622) was a randomized, open-label, phase III study that assessed efficacy and safety of olaparib vs standard single agent chemotherapy treatment of physician’s choice (TPC) in pts with HER2-negative mBC and a gBRCAm. Methods: Pts aged ≥18 y with HER2-negative mBC (hormone receptor positive or triple negative [TN]) and a gBRCAm, who had received ≤2 chemotherapy lines for mBC, were randomized (2:1) to olaparib tablets (300 mg po bid) or TPC (21-day cycles of either capecitabine [2500 mg/m2 po days 1–14], vinorelbine [30 mg/m2 IV days 1 and 8] or eribulin [1.4 mg/m2IV days 1 and 8]). Treatment was continued until objective disease progression (RECIST v1.1) or unacceptable toxicity. The primary endpoint was progression-free survival (PFS) assessed by blinded independent central review (BICR). Results: 302 pts were randomized (median age 44 y; 50% TN; 71% prior chemoth...