Novel Pfizer AIDS drug shows promise
BANGKOK – July 14 – Reuters reported that a novel AIDS pill designed to exploit the discovery that some people appear naturally resistant to HIV has produced good results in early-stage clinical trials, researchers said. New York-based Pfizer Inc.'s experimental compound UK-427,857 belongs to a new class of medicines which block the virus before it can enter human cells, rather than fighting it once inside. Such drugs may keep patients healthy for longer with fewer side effects than conventional anti-retroviral therapies and provide a new option for people who have developed resistance to conventional AIDS drugs.
Data presented at the 15th International AIDS Conference showed a once-daily dose of the compound produced a 10 to 100-fold fall in the amount of human immunodeficiency virus (HIV) in patients' blood after 10 days. This is similar to results achieved with potent protease inhibitors. There was no significant difference in the result whether or not patients had just eaten. Many other AIDS drugs have strict dietary requirements.
Steve Felstead, head of the team developing the product, said Pfizer was conducting larger scale investigations following the good results from placebo-controlled monotherapy trials involving 80 patients. “It has enabled us to test once and twice-daily doses in later trials and remove restrictions on how patients take the medication,” he told Reuters. “It's very good news for the drug and for patients.”
Pfizer hopes to start a final Phase III study, which will involve hundreds of patients, before the end of the year.
Switzerland's Roche and U.S. biotech group Trimeris launched the first drug to block HIV's entry into healthy immune cells last year, but Fuzeon is expensive, must be injected twice daily and sales - $24 million in the first quarter of 2004 - have been disappointing.
Unlike Fuzeon, which is a so-called fusion inhibitor, Pfizer's drug is a different kind of entry blocker which locks a cellular doorway called CCR5 and which can be given as a tablet. The idea for blocking it followed the observation that people with a CCR5 mutation can resist HIV infection.
Researchers noticed long ago that some prostitutes in Nairobi, Kenya, and a small number of American men never became infected despite multiple high-risk exposures. Any successful CCR5 pill is likely to be used in combination with other medicines.
Pfizer is racing with Schering-Plough to be first to develop a CCR5 drug which, if successful, could generate sales of $500-700 million a year, according to industry analysts. Schering-Plough reported in February promising early-stage results with a compound called SCH-D, but doesn’t expect to start Phase III tests until next year. GlaxoSmithKline is working on a CCR5 product but is thought to be further behind in development.