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 As a monotherapy, Keytruda halved the risk of disease progression
and cut overall deaths by 40 percent compared to chemotherapy alone
in pre-selected patients whose tumors had been tested using a
biomarker.
And when given with two older chemotherapy drugs in non-selected
patients, it was almost twice as likely to shrink tumors as
chemotherapy alone.
Another similar drug from Roche also demonstrated broad efficacy as
a so-called second-line option in patients who had received prior
treatment.
"Remember this day. It's a new day for lung cancer treatment,"
Stefan Zimmermann of Lausanne's University Hospital told reporters
at the European Society for Medical Oncology (ESMO) congress as the
results were presented.
An editorial in the New England Journal of Medicine, where the Merck
monotherapy results were published, said Keytruda could become "a
new standard of care".
The various findings suggest that treating lung cancer - the biggest
cancer killer globally - with powerful new immune system-boosting
medicines is going to involve more permutations than some experts
originally expected.
Rival drugmaker Bristol-Myers Squibb had tried a catch-all approach
with its Opdivo drug but it failed to help previously untreated
patients when given on its own in a trial that included people with
low levels of a protein called PD-L1.
Keytruda, as a sole agent, was targeted only at patients with high
PD-L1, making them more receptive to immunotherapy.
Lead researcher Martin Reck of Germany's Lung Clinic Grosshansdorf
predicted that testing for the PD-L1 biomarker would now become
standard "from today".
U.S. regulators are expected to decide whether to approve Keytruda
for first-line non-small cell lung cancer, the most common type, by
Dec. 24.
Merck had already said in June that Keytruda worked in the trial but
the scale of the benefit was only disclosed at ESMO.
COMBINATION THERAPY
The second trial, mixing Keytruda with chemotherapy, was much
smaller but was notable because it was the first time that a
combination of immunotherapy and chemotherapy has been shown to work
in a randomized Phase II study.
Many experts have been skeptical about this approach and investors'
expectations, up until now, have been quite low.
In the event, researchers reported that Merck's combination cut the
risk of disease progression or death by 47 percent compared to
chemotherapy alone after 10.6 months, while 55 percent of patients
saw their tumors shrink versus 29 percent.
Patients in this trial were not selected by PD-L1 expression but the
study did find that those with higher PD-L1 had a higher response.
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Roger Perlmutter, Merck's head of research, said both trials
suggested Keytruda could offer a broad array of patients meaningful
improvement over standard platinum-based chemotherapy, which is now
more than two decades old.
Drugs like Keytruda and Opdivo work by taking the brakes off the
immune system and allowing the body's natural killer cells to home
in on tumors.
They are expected to sell tens of billions of dollars in the years
ahead, with lung cancer the largest market.
Up until now, Bristol has dominated the field but investors have
started to shift their bets, with forecasts for Opdivo declining
while those for Keytruda have risen.
The current consensus forecast among analysts is for Keytruda sales
to reach $8 billion in 2021, with Opdivo selling $10.5 billion,
according to Thomson Reuters data.
Results of Bristol's failed Opdivo trial, which included patients
with tumors testing only 5 percent or higher for PD-L1 against the
50 percent cut-off used by Merck, were also presented at ESMO.
These showed progression-free survival was 4.2 months with Opdivo
and 5.9 months with chemotherapy, although the difference was not
statistically significant. Overall survival was 14.4 months with
Opdivo versus 13.2 months.
The failure of Opdivo to work for "all comers" in lung cancer was
first announced in August, without any details. It was a major
setback for Bristol, wiping out around a quarter of the company's
market value, and it has caused investors to rethink prospects for
immunotherapy treatments.
Many now believe that combination therapy is the way ahead, with
Bristol and AstraZeneca working primarily on using two
immunotherapies together, while Roche and Merck look at adding
chemotherapy.
(Reporting by Ben Hirschler; Editing by Stephen Powell and Susan
Fenton)
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