* HRD-negative patients show PFS benefit of 3.1 months
* Growing interest in PARP inhibitor cancer drug class
By Ben Hirschler
COPENHAGEN, Oct 8 Tesaro's experimental
drug niraparib improved outcomes for a broad range of women with
recurrent ovarian cancer in a clinical study, boosting prospects
for the product, which belongs to a closely watched class of new
U.S. biotech company Tesaro had already cheered investors in
June by saying that the study had met the main goal of
prolonging survival without disease worsening, but full results
were only reported at the annual European Society for Medical
Oncology congress in Copenhagen.
The treatment helped patients live longer without their
disease progressing. Even those least likely to be helped by the
drug, because of their genetic profile, saw a benefit of just
over three months, researchers told the meeting on Saturday.
Niraparib is a so-called PARP inhibitor that blocks enzymes
involved in repairing damaged DNA, thereby helping to kill
AstraZeneca's Lynparza became first of the new class
to reach the market when it won U.S. approval at the end of
2014, but it was only cleared for patients whose cancer tested
positive for defective BRCA genes.
Tesaro aims to prove its drug can work more widely,
potentially across the entire population of women needing
maintenance therapy for ovarian cancer after chemotherapy.
"This is a breakthrough for patients with ovarian cancer,"
study leader Mansoor Raza Mirza of Copenhagen University told
the meeting. "We have never seen such large benefits in
progression-free survival (PFS) in recurrent ovarian cancer."
The latest findings showed that various patient populations
all responded, with the biggest median PFS of 15.5 months seen
in the BRCA mutation group. However, even those with no BRCA
mutation and who tested negative to another test called HRD
still saw a modest but significant benefit of 3.1 months.
There is now likely to be debate among doctors and investors
as to whether this is enough for Tesaro to win very broad
approval for its drug or whether it should be reserved for a
narrower group of patients based on genetic tests.
Myriad Genetics provided the diagnostic test that
was used to recruit patients into Tesaro's drug trial, results
of which were also published online in the New England Journal
Interest in PARP inhibitors has grown apace over the last
year as drug developers try to target DNA repair mechanisms
inside cells as a way to fight cancer.
Other companies with PARP inhibitors in development include
Clovis, AbbVie and Medivation, which was
recently bought by Pfizer for $14 billion.
(Editing by Alexander Smith)