FDA staff question validity of benefit seen with AstraZeneca drug

June 23 (Reuters) - Staff reviewers at the U.S. Food and Drug Administration said AstraZeneca Plc (NYSE: AZN - news) 's experimental ovarian cancer drug olaparib showed an 83 percent reduction in the risk of disease progression but questioned whether the result could be reproduced.

The drug, olaparib, is designed as a maintenance treatment for certain women with relapsed ovarian cancer whose tumors are responding completely or in part to platinum-based chemotherapy.

Olaparib blocks the activity of Poly (ADP (Frankfurt: W7L.F - news) -ribose) polymerase (PARP), an enzyme that plays a key role in cell repair. The drug is aimed at women with a BRCA gene mutation. Patients in a clinical trial had a seven-month median improvement in progression-free survival.

The staff report, published on the FDA's website on Monday, comes two days ahead of a meeting of outside experts who will discuss whether the drug's benefits outweigh its risks and whether further data is needed before approval. (Reporting by Toni Clarke in Washington; Editing by Bill Trott)