The fight against HIV/AIDS is costly, contentious and, for drug companies, a calculated risk. This year, five new antiretroviral drugs in different classifications made strong advances, offering hope to patients with drug-resistant strains of the virus. But there were also setbacks. Merck, for instance, was on the trail of a leading experimental AIDS vaccine when some patients during Phase II trials became infected with HIV, derailing the study.
“The vaccine arena is just incredibly difficult; on the other hand, there have been huge strides with more effective drugs,” says Graham Allaway, a research scientist and founder of Panacos Pharmaceuticals. “By chance, a lot of drug development taking place over the last few years came to fruition around the same time.”
In August, for the first time in more than a decade, the FDA approved a new class of antiretroviral drugs called entry inhibitors. Pfizer’s Selzentry (generic name, maraviroc), which went on sale in the United States in September, binds with host cell receptors to prevent the virus from attaching to and entering healthy host cells. Unfortunately, it requires a $1,960 test to determine whether patients have the right strain of virus, and monthly treatments cost $900.
Soon after, the FDA also approved Merck’s Isentress (raltegravir), the first integrase inhibitor, which stops viral DNA from incorporating into host cell chromosomes. Meanwhile, other drugs are showing promise: Schering-Plough’s vicriviroc, an entry inhibitor, is in Phase III trials; Gilead Sciences’ elvitegravir, an integrase inhibitor, and Panacos’ bevirimat, the first maturation inhibitor, are moving successfully through Phase II trials. Bevirimat targets the last stage of the virus life cycle by blocking a protein necessary for viral reproduction.
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