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May 8, 2007: The U.S. Food and Drug
Administration’s (FDA) is likely to approve a
novel HIV drug Maraviroc that blocks the virus
from entering a fresh cell.
Maraviroc, brand-named Celsentri, can be used
along with other antiretroviral agents for
treatment-experienced patients infected with
CCR5-tropic HIV-1. Rather than fighting HIV inside
white blood cells, as conventional drugs do, it
prevents the virus from entering uninfected cells
by blocking its predominant entry route, the CCR5
co-receptor.
If approved, maraviroc would be the first member
of a new class of oral HIV medicines in more than
a decade.
The Antiviral Drugs Advisory Committee that
recommend the approval of maraviroc the drug would
offer patients resistant or intolerant to the
current inventory of HIV drugs an alternative
treatment option.
Pfizer said that maraviroc will be used for
treatment-experienced patients, but its label
could eventually be expanded for the
treatment-naive.
The FDA has, however, asked Pfizer to conduct
further studies to investigate liver toxicity and
other side effects, as well as the treatment's
efficacy in patient populations hitherto untested,
specifically females and non-caucasians.
The earning potential of Celsentri may not be
initially that great for Pfizer, as patients will
have to submit to a diagnostic test to verify they
have the HIV virus type which can be treated with
the drug.
Discovered by Pfizer scientists in 1997, maraviroc
works by blocking viral entry to human cells. In
the pivotal MOTIVATE trials, nearly twice as many
treatment-experienced CCR5-tropic HIV-1 infected
patients treated with maraviroc plus optimized
background therapy (OBT) achieved undetectable
viral loads at 24 weeks compared to those
receiving placebo plus OBT.
There were no significant increases in
hepatotoxicity, malignancy or mortality in
maraviroc’s treatment arms, while there were
slight increases in upper respiratory and herpes
simplex virus infections as well as with ischemic
events, consistent with the rate observed in
treatment experienced HIV/AIDs patients.
Preliminary safety data beyond 24 weeks from the
ongoing MOTIVATE trials were shared with the
advisory panel today and the 48-week study
outcomes will be submitted for presentation at a
scientific forum later this year.
Maraviroc is currently undergoing expedited
regulatory review. While the FDA is not bound by
the Advisory Committee recommendations, in most
cases, the FDA does follow the recommendations.
In 2005, the market for HIV was worth USD 7.1bn
and is likely to undergo significant changes over
the next several years. A Datamonitor report
published on 11 April revealed that the value of
the HIV market could grow to USD 10.6bn by 2015.
Celsentri will make a significant contribution to
the predicted growth in the HIV market, but Merck
& Co's integrase inhibitor, Isentress (raltegravir),
and Tibotec's non-nucleoside reverse transcriptase
inhibitors, TMC125 and TMC278, will also add
value. Gilead and Bristol-Myers Squibb's (BMS)
Atripla (efavirenz/ tenofovir/ emtricitabine) has
already been launched in the US and should reach
the EU market in 2007.
Datamonitor adds that Celsentri and Isentress
should capture market share from Roche's
injectable fusion-inhibitor, Fuzeon, which
currently dominates late-stage salvage therapy in
cross-resistance patients, as Celsentri and
Isentress can be taken orally. Fuzeon will
probably be restricted for use in patients who
have exhausted all other treatment options.
Datamonitor's report projects Celsentri sales to
reach USD 350m in 2015, while Isentress should
make USD 400m. Atripla, which is experiencing
rapid uptake, could bring in sales for Gilead and
BMS of USD 1.7bn by 2015.
Tibotec's TMC125 is set to reach market in 2008
followed by TMC278 in 2009. TMC125 may be limited
to late-stage use, but TMC278 has been touted for
use in early-line therapy and may have a greater
impact on the market, according to the report.
TMC125 sales could reach USD 200m by 2015, while
TMC278 is expected to exceed USD 500m by the same
year, according to reports.
BY OUR PHARMA CORRESPONDENT
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