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 They will unveil results of studies for rival drugs to block a
cancer's ability to repair its genetic code, presenting their
findings at the European Society For Medical Oncology's (ESMO)
annual conference in Barcelona over the weekend.
Both companies have already flagged that their respective drug
candidates, part of a class known as PARP inhibitors, did well in
staving off a return of ovarian cancer in women that had responded
to initial standard treatment.GSK and Astra, which are also
competing in respiratory drugs, have held back full trial details
for the ESMO event.
Analysts and investors will be looking for clues as to how large a
patient group will likely benefit in the future.
Many cancer cells have a limited ability to make DNA repairs during
cell division, as healthy cells would. This feature, one of the
hallmarks of cancer, makes tumors genetically volatile and helps
them develop resistance to treatment over time.
Drugmakers try to use that to their advantage with PARP inhibitors
that block what is left of the DNA repair mechanism so cancer cells
fail to replicate and a tumor cannot sustain itself.
The drug class was initially targeted at patients that had a
mutation in BRCA genes but the two British drugmakers are keen to
add to evidence that wider patient groups can be helped with their
respective drugs.
"The utility of the PARP inhibitors could be much broader than just
patients that have a tumor with the BRCA mutation," said John
Bowler, who manages more than $300 million in healthcare and biotech
stocks at asset manager Schroders.
"That becomes relevant when you start thinking about the drugs' role
in other tumor types like prostate cancer and breast cancer where
the incidence of new patients each year is much greater than in
ovarian cancer," he said.
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GlaxoSmithKline cancer treatment Zejula slowed the progression of
ovarian cancer in a late-stage study called PRIMA, the British
drugmaker said in a release of headline data in July.
The drug originated in the labs of U.S. cancer specialist Tesaro,
which GSK acquired for $5.1 billion in December. The deal,
masterminded by Chief Scientific Officer Hal Barron, was seen as too
pricey by many analysts.
"The outcome of this trial is the key test of Hal Barron saying this
will justify the deal on its own if it comes good. This would be
vindication for the first big acquisition that he has done for Glaxo,"
said Bowler of Schroders.
Astra and its U.S. development partner Merck & Co announced on Aug.
14 that their joint drug Lynparza was shown to slow the progression
of ovarian cancer that had started to spread in the body, in the
so-called PAOLA-1 trial.
An inclusion requirement for trial participants had been a
successful initial treatment with chemotherapy and Roche's Avastin
following a diagnosis of advanced ovarian cancer.
Analysts see Astra and Merck's Lynparza in the lead with an average
annual sales estimate of $3.1 billion in 2023. GSK's Zejula is seen
at about 870 million pounds ($1.1 billion) in revenues that year.
Two more PARP inhibitors, Pfizer's Talzenna and Clovis Oncology's
Rubraca, are seen as further behind.
(Editing by Edmund Blair)
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