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 The treatment involved standard HIV drugs, known as antiretroviral
therapy or ART, plus an experimental antibody that hits the same
target as Takeda Pharmaceutical's Entyvio, a drug approved in more
than 50 countries for ulcerative colitis and Crohn’s disease.
The findings, published Thursday in the journal Science, are
promising enough that scientists at the National Institutes of
Health, which funded the research, have already begun testing the
Takeda drug, known generically as vedolizumab, in people newly
infected with HIV.
“The experimental treatment regimen appears to have given the immune
systems of the monkeys the necessary boost to put the virus into
sustained remission," said Dr. Anthony Fauci, director of the
National Institute of Allergy and Infectious diseases, part of the
NIH, who co-led the study.
Sustained remission - known as a "functional cure" - could have
sweeping implications for people infected with the human
immunodeficiency virus or HIV, which attacks the immune system.
Highly effective treatments known as antiretroviral therapy push the
virus down to undetectable levels in the blood, but they must be
taken every day over a person's lifetime to remain effective, said
Aftab Ansari of Emory University School of Medicine who co-lead the
study.
Ansari said the study was based on the understanding that in the
early days of infection, HIV attacks a specific class of immune
cells that congregate in large quantities in the gut. They theorized
that if they could protect these immune cells, they could buy the
immune system enough time to mount an effective response.
To do this, the team tested an antibody that blocks a protein called
alpha-4/beta-7 integrin that HIV uses to attack immune cells in the
gut.
For the study, they infected 18 monkeys with simian immunodeficiency
virus or SIV, the monkey version of HIV. They then treated all of
the animals with ART for 90 days, and, as it does in humans, the ART
controlled the virus, reducing it to undetectable levels.
Antiretroviral drugs used in this stage of the experiment included
Gilead's tenofovir and emtricitabine, sold in a combination drug for
people as Truvada, and a Merck integrase inhibitor known as
L-870812.
In 11 monkeys, the scientists then gave infusions of the antibody
for 23 weeks, and seven monkeys got a placebo. Three of the 11
monkeys developed a reaction to the treatment and had to stop the
therapy.
In the eight monkeys that got the treatment, six initially showed
signs that SIV was rebounding, but eventually their immune systems
were able to control the virus. In two others, the virus never
rebounded. All eight have continued to suppress SIV to undetectable
levels for up to 23 months after all treatment stopped. In the
control group, SIV rebounded and all seven animals died.
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The study did not look at whether the monkeys were still able to
transmit the virus, but studies in people have shown that reducing
HIV to undetectable levels cuts transmission rates by nearly 100
percent.
Ansari said the study is promising because it could eventually lead
to a treatment for HIV in people that would not require a lifetime
of ART therapy.
Scientists have recently focused on efforts to cure HIV, reducing
the burden of lifelong treatment, but prior efforts have been
frustrated by the HIV virus' ability to form hidden reservoirs that
replenish the virus when treatments are halted.
In one dramatic case, Timothy Ray Brown, the so-called "Berlin
patient," was cured of HIV after an elaborate treatment for leukemia
in 2007 that involved the destruction of his immune system and a
stem cell transplant from a donor with a rare genetic mutation that
resists HIV infection.
Ansari cautioned that not all treatments that work in monkeys will
work in people. He said the findings are still very early, and said
many more experiments are needed to understand why the antibody
protected the monkeys.
Still, he said Takeda's antibody vedolizumab is "identical" to the
one the team used on the monkeys.
NIH researchers already have begun a study to see if a 30-week
course of Takeda's drug vedolizumab is safe and helps control HIV
when patients are temporarily taken off conventional ART treatments.
Preliminary results are expected by the end of 2017 with further
data becoming available into 2018.
If proven safe, the drug would need to be studied in larger trials
to prove it is also effective.
Takeda spokeswoman Elissa Johnsen said the company is "pleased to
support the trial and contribute to scientific discovery" but said
it was too early to comment on future development plans.
(Reporting by Julie Steenhuysen; Editing by Bernard Orr)
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