1018 Background: Triple negative breast cancer (TNBC) shares molecular characteristics with BRCA1-/- breast cancer (BC). Preclinical and clinical data show that BRCA1-/- BC and TNBC are sensitive to inhibition of PARP1, an enzyme necessary for DNA repair and other critical cell functions. This phase 1 study evaluated the tolerability of olaparib, a potent PARP1 inhibitor, combined with weekly paclitaxel in patients with metastatic TNBC. This trial served as a safety evaluation to be followed by a phase II trial after tolerability was determined. Methods: Eligible patients (pts) had ≤ 1 prior cytotoxic regimens for ER-, PR-, and HER2- metastatic BC. Pts were treated with olaparib 200mg capsules PO BID continuously combined with paclitaxel 90mg/m2 IV weekly for 3 of 4 weeks. At this dose, a significant number of pts had delays due to neutropenia, thus a second cohort of 10 pts was enrolled with an amendment to the protocol to allow for GCSF (300 μ g SC days 3-5) as secondary prophylaxis following weekly pac...