In December 2018, the US Food and Drug Administration (FDA) approved olaparib (Lynparza®), a poly (ADP-ribose) polymerase (PARP) inhibitor, for the first-line maintenance treatment of adult patients with deleterious or suspected deleterious germline or somatic BRCA-mutated (gBRCAm or sBRCAm) advanced epithelial ovarian, fallopian tube or primary peritoneal cancer, who are in complete response (CR) or partial response (PR) to first-line platinum-based chemotherapy. To date, olaparib has not yet been approved by the European Medicines Agency (EMA) for the assessed indication.

The SOLO1 trial evaluated the efficacy and safety of an olaparib first-line maintenance therapy in patients with newly diagnosed advanced ovarian cancer, primary peritoneal cancer or fallopian tube cancer and a BRCA1/2 mutation, who had a CR or PR after platinum-based chemotherapy. Investigator-assessed analysis showed that the Kaplan-Meier estimate of the rate of freedom from disease progression and from death at three years was 60% in the olaparib group versus 27% in the placebo group (the Hazard Ratio [HR] for disease progression or death was 0.30). According to the analysis assessed by blinded independent central review, the Kaplan-Meier estimate of the rate of freedom from disease progression and from death at three years was 69% in the olaparib group versus 35% in the placebo group. A sensitivity analysis of investigator-assessed PFS showed that the median PFS was 36.1 months longer in patients of the olaparib group than in patients of the placebo group (HR was 0.31). An interim analysis of Overall Survival (OS) data showed a Kaplan-Meier estimate of the rate of freedom from death at three years of 84% (olaparib group) versus 80% (placebo group); HR for death was 0.95. The median time to the first subsequent therapy or death was longer in olaparib group patients (51.8 months) than in placebo group patients (15.1 months). Serious Adverse Events (AEs) occurred in 21% of patients receiving olaparib and 12% of patients who received placebo. No AEs that occurred during the study intervention (or up to 30 days after discontinuation) led to death.

SOLO1 trial results showed a benefit with olaparib first-line maintenance therapy in delaying the disease progression in patients with newly diagnosed ovarian cancer and BRCA1/2 mutation. However, the trial is currently ongoing, the presented data are the primary analysis data, and interim OS data are immature. Health-related quality of life data also derives from primary analysis and the detected between-group difference was not considered to be clinically meaningful. Final analysis data from the SOLO1 trial is pending and may confirm the clinical benefit of olaparib first-line maintenance therapy. Further investigation of olaparib first-line maintenance therapy in phase III trials, long-term data, as well as a direct comparison of olaparib with different PARP inhibitors are warranted to determine the optimal treatment for this patient population.