Olaparib in Patients With BRCA Mutated Platinum-Sensitive Relapsed Serous Ovarian Cancer: New Data Presented at ASCO

A retrospective subgroup analysis of a Phase II study (Study 19) shows the effect that an investigational drug, olaparib, has on progression-free survival (PFS) compared with placebo in platinum-sensitive relapsed serous ovarian cancer patients with BRCA mutations.

Study 19 was a randomized, double-blinded Phase II clinical trial evaluating the efficacy and safety of olaparib 400mg twice daily maintenance therapy compared with placebo in 265 platinum-sensitive, relapsed, high grade serous ovarian cancer patients who had received two or more previous platinum regimens and who were in a partial or complete response following their last platinum-containing regimen. The primary endpoint was PFS. Results from the full study population, first presented at American Society of Clinical Oncology (ASCO) 2011 and later published in the New England Journal of Medicine (NEJM) in 2012, showed that olaparib maintenance therapy significantly extended PFS compared with placebo (HR=0.35;95% CI 0.25–0.49 P

The initial pre-planned subgroup analysis of PFS and OS in patients with a BRCA mutation suggested an improved outcome compared to the overall study population. However, mutation status was known for only a minority of patients in the study (36.6%) at that time and additional biomarker work was therefore conducted to further investigate this signal. BRCA mutation status was subsequently determined for patients from either blood samples (taken pre-randomization) and/or archival tumor samples and BRCA mutation status was eventually documented for 254 (96%) of the 265 patients in Study 19 confirming that 136 (51%) patients in the study had a BRCA mutation (BRCAm).

Retrospective results, in the total BRCAm population showed that olaparib maintenance therapy prolonged PFS compared with placebo (HR 0.18; 95% CI 0.11-0.31; p

The most common adverse reactions occurring more frequently in the BRCAm patients treating with olaparib were low grade nausea, fatigue, vomiting and anemia, similar to those seen in patients without BRCA mutations.

Jonathan Ledermann, MD, UCL Cancer Institute, University College London and lead study investigator, said: “These are encouraging results for patients with ovarian cancer who carry a BRCA mutation. The statistically significant seven month difference in progression-free survival in the subgroup of patients with a BRCA mutation supports the hypothesis that a personalized therapeutic approach based on BRCA mutation status could preferentially benefit this patient population. This warrants further investigation of olaparib in a Phase III clinical trial.”

BRCA are human genes that belong to a type of genes known as tumor suppressors. Mutation of these genes has been linked to hereditary breast and ovarian cancer and a woman's risk of developing breast and/or ovarian cancer is greatly increased if she inherits a BRCA1 or BRCA2 mutation. Only 15% of ovarian cancers are found before the cancer has spread outside the ovary. Despite advances in treatment and diagnosis, for patients with ovarian cancer that has spread beyond the ovary, the 5-year survival rate is well below 50%.

As a result of these Phase II data, AstraZeneca has announced that it is developing Phase III clinical trial program to further evaluate olaparib in BRCA mutated ovarian cancer. AstraZeneca has submitted a Letter of Intent to file for approval with the European Medicines Agency for olaparib in ovarian cancer patients with BRCA mutations.

Jane Robertson, Global Product Vice President for olaparib at AstraZeneca, said: “We are committed to conducting further studies of olaparib in patients with BRCA mutated tumors and to assessing its full potential in these and other cancers. We look forward to continuing to work with our collaborators and partners to strengthen our understanding of which patients are likely to benefit most from olaparib through a program of translational science and pre-clinical research.”

Additional olaparib data to be presented at ASCO 2013 include:

• Abstract #4013 - Olaparib plus paclitaxel in patients with recurrent or metastatic gastric cancer: A randomized, double-blind phase II study (Study 39)
• Abstract #2579 - Phase I study of olaparib in combination with carboplatin and/or paclitaxel in patients with advanced solid tumors. (Study 4)
• Abstract #11024 - Olaparib monotherapy in patients with advanced cancer and a germ-line BRCA1/2 mutation: An open-label phase II study. (Study 42)