http://www.cbc.ca/health/story/2007/04/04/hiv-drug.html

New HIV drug shows promise
Last Updated: Wednesday, April 4, 2007 | 6:55 PM ET
CBC News
For people with advanced HIV infections, a new drug seems to suppress
the virus better than existing treatments.

Antiviral drugs called protease inhibitors have been the gold standard
for treating HIV since the mid-1990s, but the virus is becoming
increasingly resistant.

The new drug, darunavir, also called Prezista, is like other protease
inhibitors designed to lock up an enzyme that the virus needs to make
more copies of itself.

In the study, researchers studied 100 people who took darunavir in
combination with a low dose of an older protease inhibitor called
ritonavir, and a control group of 120 people who took an existing
combination therapy.

People in both groups had advanced HIV infection and their current
therapies were failing, said Dr. Bonaventura Clotet of Barcelona and
colleagues in an upcoming issue of the medical journal the Lancet.

About 45 per cent of those taking darunavir-ritonavir showed the
lowest recordable level of HIV genetic material in their blood
compared with 10 per cent in the control group.

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People taking darunavir-ritonavir also showed an increase in the
immune system's CD4 cells that was five times higher than among those
in the other group (19 cells per microlitre versus 102 cells per
microlitre).

Doctors use the amount of HIV in the blood, or viral load, and the
levels of infection-fighting CD4 cells to track progression to AIDS
and to measure if antiretroviral therapy is working.

New option for HIV resistance
To prove darunavir works, patients will need to be tracked, ideally
for another two or three years, said Dr. Rodger MacArthur, of Wayne
State University in Detroit, in a journal commentary.

"For now, all of us treating HIV-infected individuals in clinical
practice will probably rejoice in the availability of darunavir, since
it seems to be a safe, well-tolerated, and truly effective agent
against multi-drug resistant HIV," MacArthur wrote.

Darunavir-ritonavir also needs to be compared with an existing
therapy, tipranavir-ritonavir, since resistance to one could fuel
resistance to the other.

The virus mutates quickly and may resist medications, especially if
drug regimens are not followed closely.

Failure rates for antiretroviral drugs range from 21 per cent among
patients already taking the medications to 11 per cent in those just
starting treatment, the researchers said.

Prezista is approved for sale by the U.S. Food and Drug
Administration, and with conditions by Health Canada and European
regulators.

At the International AIDS Conference in Toronto in 2006, researchers
reported early results of a new class of drugs, called integrase
inhibitors, that stop the genetic material's ability to integrate with
the host chromosome.

Integrase inhibitors would tackle the third and final step that HIV
undergoes to copy itself.