Background: In Study 19 (NCT00753545), olaparib capsules demonstrated improvement in progression-free survival (PFS) vs placebo in the PSR OC maintenance setting, irrespective of BRCAm status (Ledermann et al. Lancet Oncol 2014). LIGHT is the first prospective study to evaluate olaparib tablet treatment in PSR OC pts by BRCAm and HRD status. Methods: This is an open-label, non-randomized study (NCT02983799) that assessed efficacy and safety of olaparib monotherapy (300 mg BID) in pts with PSR, high-grade serous/endometrioid epithelial OC and ≥1 prior line of platinum chemotherapy. Pts were assigned to one of four cohorts: germline (g) BRCAm; somatic (s) BRCAm; HRD+ve (non-BRCAm); HRD–ve; by Myriad BRACAnalysis CDx and myChoice tests. HRD+ve was a score ≥42. Primary endpoint was objective response rate (ORR). Secondary endpoints included: disease control rate (DCR) and investigator-assessed PFS (RECIST v1.1). Primary analysis was to be ~6 months (mo) after the last pt was enrolled. Results: Data cut off was 8/27/19. Of 271 pts treated (median of 31.7 weeks [2.1–96.0]), 270 had measurable disease at baseline and were included in efficacy analyses (Table). The most common treatment-emergent adverse events (AEs) were nausea (66%) and fatigue (62%).Serious AEs and Grade ≥3 AEs were experienced by 25% and 44% of pts, respectively. AEs leading to olaparib dose interruptions, reductions and discontinuations occurred in 33%, 24% and 4% of pts, respectively. Conclusions: Olaparib treatment demonstrated activity across all cohorts. As observed in the maintenance setting, similar efficacy was seen in the gBRCAm and sBRCAm cohorts. For non-BRCAm pts, longer median PFS and higher ORR were observed in the HRD+ve cohort. Olaparib treatment was well tolerated with no new safety signals identified and a safety profile consistent with that seen in the PSR and first-line settings. Clinical trial information: NCT02983799

*13 pts with a Myriad test result of failed or missing were included in the overall population. CI, confidence interval; NE, not estimable