New drugs block AIDS, but a vaccine remains elusive

Two decades into the AIDS pandemic the world has two dozen drugs to fight the virus, and researchers have high hopes for new classes of medicine that block the virus before it can enter human cells. But an effective vaccine--the best hope for the developing world, where drugs remain out of reach for millions--is still only a distant hope. Pharmaceutical makers will showcase their latest advances at the International AIDS Conference in Bangkok, Thailand, from July 11 through 16. Joep Lange, president of the International AIDS Society, expects a focus on experimental compounds that stop HIV from entering cells rather than fighting it once inside. Such drugs may keep patients healthy for longer with fewer side effects. "The inhibition of HIV entry is the field with the most promise at the moment," said Lange, a professor of internal medicine at the University of Amsterdam. "One of the main problems with current drugs is their long-term toxicity and particularly their metabolic side effects. It is very unlikely that the entry inhibitors will give those sort of side effects." Switzerland's Roche and U.S. biotech group Trimeris last year launched the first drug of this type, known as a fusion inhibitor. Now Pfizer and Schering-Plough are racing to develop a different kind of entry inhibitor that blocks a cellular doorway called CCR5 and can be given as a pill. Schering-Plough reported promising early-stage results with a compound called SCH-D in February, and Pfizer is expected to report in Bangkok that its rival drug, UK-427,857, is at least as effective as existing antiretrovirals in short-term tests. Pfizer aims to start final Phase III tests later this year, putting it ahead in the race to develop a drug that, if successful, could generate sales of $500 million to 700 million a year, according to Cathay Financial analyst Sena Lund in New York. Little concrete news is expected to be presented in Bangkok on a safe and effective HIV vaccine. Trials of 30 vaccine candidates are currently under way in 19 countries--but there is only one pivotal Phase III trial, and hopes for this project, involving 16,000 volunteers in Thailand, are not high following the failure of a related study last year. "An effective AIDS vaccine promises to end the epidemic," said Seth Berkley, president and chief executive of the nonprofit International AIDS Vaccine Initiative. "A 50% effective vaccine given to two thirds of the adult population could reduce infections up to 60%." To get there, Berkley wants to see 10% of global AIDS spending devoted to finding a vaccine, up from between 2% and 3% now. (Reuters)