Two New AIDS Drugs Offer Advances, Hope

by Kilian Melloy
Tuesday Mar 10, 2009

There's new hope for people living with HIV/AIDS whose medications have begun to stop working against the always-adapting virus: two new classes of drugs have come onto the market.

A Feb. 28 story in The New York Times cited the University of Pittsburgh's Dr. John W. Mellors, who serves as a consultant to pharmaceuticals firms, as drawing parallels between the new drugs and the advent of the so-called "cocktail" of medications that dramatically improved survival rates, adding quality years to the lives of HIV positive people in the 1990s.

Mellors, speaking at the 14th Annual Conference on Retroviruses and Opportunistic Infections, said, "This is really a remarkable development in the field," the article reported.

Another consultant, Dr. Scott Hammer, was quoted as saying that the new treatment options would "provide extended years of meaningful survival to patients." Dr. Hammer is Columbia University Medical Center's chief of infectious diseases, the article noted.

The new medications are called maraviroc and raltegravir.

The pharmaceutical firm Pfizer has seen its new drug, maraviroc, attain FDA approval and become available. Maraviroc works not by attacking the virus directly, but rather by blocking the proteins on human cells that the virus uses to gain access to the cells' interiors, where it hijacks the cell's own reproductive machinery, turning the cell into a factory for new copies of the virus.

If the virus cannot use those sites to attach to and enter the cell, its reproductive process is interrupted. The article noted that maraviroc is the first drug to use this approach to be developed that does not seem to entail grave side effects, following the 1996 discovery of the protein in question, known as CCR5.

In a minority of cases, the article noted, a strain of the HIV virus will use a different protein, CXCR4, instead of CCR5 to gain access to the cells' interiors; a test will be required to ensure that the patient's particular strain of HIV uses CCR5 before maraviroc will be prescribed.

Other firms had attempted to exploit the same protein-blocking approach, but the drugs they developed seemed to involve dangerous side effects.

No such consequences have been noted thus far with maraviroc, though trials are ongoing to determine whether there might be a risk of longer-term side effects.

In maraviroc's clinical trials, 40% of trial participants saw their viral loads diminish to undetectable levels after four months on maraviroc, despite the virus having become resistant to the participants' previous drug regimens.

The other new drug, raltegravir, was developed by Merck. At present, the FDA has approved raltegravir for some patients who are already taking other medications in cases where the virus has become resistant to antiretrovirals. A future approval from the FDA would clear the way for patients who are new to treatment to begin taking raltegravir; an application to the FDA is under review to allow this.

The Merck drug also acts to interrupt the virus' reproductive cycle: in this case, by blocking the action of a crucial enzyme that allows the virus to insinuate its own genetic sequence into the host cell's DNA, causing the host cell to create more HIV.

Two Merck studies resulted in undetectable levels of HIV in 60% of trial participants in whom the virus had adapted to older medications, the article reported.

The article noted that in many cases, the virus' adaptation to older medications was accelerated by individuals neglecting to take their medications on schedule.

Both raltegravir and maraviroc would be taken in conjunction with older drugs, the article reported.

Kilian Melloy serves as EDGE Media Network's Assistant Arts Editor. He also reviews theater for WBUR. His professional memberships include the National Lesbian & Gay Journalists Association, the Boston Online Film Critics Association, The Gay and Lesbian Entertainment Critics Association, and the Boston Theater Critics Association's Elliot Norton Awards Committee.


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