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 The company's shares fell 30 percent to a two-year low of $20.00 in
early trading.
Portola's betrixaban, designed for the prevention of venous
thromboembolism (VTE), or blood clots, was tested against an
injectable standard therapy in patients hospitalized for serious
conditions such as heart failure, stroke, and pulmonary disease.
In the study, patients were divided into three groups. The first
with a high risk of VTE, the second with high VTE risk and aged
above 75, and the last included the overall population.
The trial was designed such that the primary efficacy analysis of
the first group was to be done initially and had to be successful,
before the other groups could be evaluated.
The first group narrowly missed the required threshhold, Portola
said, but management went ahead and analyzed the remaining groups,
which threw up data in favor of betrixaban.
On safety, there isn't much to argue about, but on efficacy the
study has failed, Morgan Stanley analysts wrote, adding that without
meeting the required threshhold in the first group, all of the other
analyses are exploratory.
"We are not yet ready to completely rule out betrixaban, but we
acknowledge there is a long road ahead."
There was no statistical difference in major bleeding between the
patients who were treated with betrixaban and those given the
injectable, enoxaparin, in the 7,513-patient trial, the company
said.
The number of fatal bleeds was balanced between the two therapies,
but the number of brain hemorrhages was numerically lower in
patients on betrixaban. Overall, a "positive net clinical benefit"
with betrixaban was observed, Portola said.
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Chief Executive Bill Lis said the totality of the efficacy and
safety data in such a high-risk patient population was robust enough
to support the submission of marketing application for the drug
later this year.
Although more than half of all VTE events occur after the patient is
discharged, no anticoagulant, including any of the marketed oral
Factor Xa inhibitors, is approved for the prevention of VTE in both
the hospital setting or after discharge, the company said.
Betrixaban is also designed to inhibit the activity of Factor Xa, a
protein involved in the blood-clotting process. Factor Xa inhibitors
include Xarelto from Johnson & Johnson and Bayer AG, and Eliquis,
sold by Bristol-Myers Squibb Co and Pfizer Inc.
(Reporting by Natalie Grover in Bengaluru; Editing by Maju Samuel)
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