Background: Cediranib, a pan-vascular endothelial growth factor receptor tyrosine kinase inhibitor, suppresses expression of BRCA1, BRCA2, and RAD51 and increases sensitivity of tumors to poly-(ADP-ribose) polymerase (PARP) inhibitors in vitro. Olaparib, a PARP inhibitor, demonstrates clinical efficacy in patients with germline BRCA1/2 mutations and HER2-negative metastatic breast cancer. We therefore tested the anti-tumor activity of the combination of cediranib and olaparib in patients (pts) with metastatic triple-negative breast cancer (TNBC). Methods: This multi-institutional, two-stage, phase II study enrolled patients with metastatic TNBC previously treated with a minimum of one prior line of systemic therapy in the advanced setting. Patients were treated with cediranib 30mg po daily plus olaparib 200mg po BID until disease progression or unacceptable toxicity. The primary endpoint was objective response rate by RECIST v1.1. Baseline tumor biopsies were obtained for biomarker analyses. Results: Baseline characteristics of the 37pts enrolled are summarized below. The overall objective response rate was 14% (95% CI: 0.025, 0.2453). Median duration of response was 2.0 months (mos) with a range of 1.8 to 6.3 mos. Disease control rate ((# of pts with CR, PR or SD)/(# of evaluable pts)) was 81% (95% CI: 0.6846, 0.937). Median PFS was 3.7 mos (95% CI: 2.1, 4.3). Grade 3/4 adverse events (G3/4 AEs), irrespective of attribution, occurred in 25 of 38 (66%).G3/4 AEs occurring in > 5% of pts were hypertension (24%) and dyspnea (11%), diarrhea (8%) vomiting (8%). Conclusions: The cediranib/olaparib combination resulted in promising objective responses in 14% of biomarker-unselected patients with heavily pre-treated, metastatic TNBC. The regimen required prompt initiation of antihypertensives, but AEs were overall manageable. Analyses of mutation status in homologous recombination DNA repair genes are ongoing and will be correlated with clinical outcome. Clinical trial information: NCT02498613.