(Updates with share price reaction, details from report)
By Toni Clarke
June 23 AstraZeneca Plc's experimental
ovarian cancer drug, olaparib, showed an 83 percent reduction in
the risk of disease progression, but a U.S. Food and Drug
Administration staff review has questioned whether the result
could be reproduced.
The company's shares fell 1.8 percent to 43.89 pounds on the
London Stock Exchange.
Olaparib, one of several cancer drugs AstraZeneca has
flagged as having strong potential in its defense of a $118
billion take-over bid by Pfizer Inc, is designed as a
maintenance therapy for relapsed ovarian cancer in which tumors
have responded completely or partially to platinum-based
"AstraZeneca has put up some pretty lofty expectations,"
said Damien Conover, an analyst at Morningstar.
The FDA staff report, published on the agency's website on
Monday, comes two days ahead of a meeting of outside experts who
will discuss whether olaparib's benefits outweigh its risks and
whether further data is needed before approval.
The FDA is not obligated to follow the recommendations of
its advisory panels but typically does so.
Olaparib, which would be sold under the brand name Lynparza
if approved, blocks the activity of Poly (ADP-ribose) polymerase
(PARP), an enzyme that plays a key role in cell repair.
Patients in a clinical trial had a seven-month median
improvement in progression-free survival, a benchmark that
measures the amount of time a patient lives without the disease
The drug is aimed at women with certain hereditary BRCA gene
mutations that account for an estimated 10-15 percent of all
cases of ovarian cancer, or about 2,000 cases a year in the
Patients with the mutations tend to respond better to
chemotherapy so they are likely to undergo multiple rounds.
Periods away from chemotherapy allow the patient to recover from
side effects before undergoing a new round.
In theory, olaparib would extend that period of recovery
The way the company conducted its data analysis, however,
has created some uncertainty about the validity of the results,
the FDA review said. AstraZeneca collected some of the data
retrospectively using archived blood samples, calling into
question "the reliability of the estimation of treatment
effect," the review said.
Data suggests most patients will experience some degree of
progression-free survival but the benefit may be due in part to
a control arm that performed unusually poorly, the review said,
adding there was no difference on overall survival between the
two treatment arms.
AstraZeneca has said sales of olaparib could reach $2
billion a year, although some Wall Street estimates peg the
potential sales at half that figure.
Ovarian cancer is the fifth leading cause of cancer death in
women, with an estimated 22,000 new cases diagnosed and 14,270
deaths in the United States in 2014.
Olaparib's most common side effects were nausea, fatigue,
abdominal pain, vomiting, diarrhea and anemia.
(Reporting by Toni Clarke in Washington; Editing by Bill Trott
and Paul Simao)