New HIV Drug To Move Into Wider Trials, Could Offer Hope to People With Drug-Resistant Strains

An experimental antiretroviral drug developed by Watertown, Mass.-based Panacos Pharmaceuticals -- which has been shown to reduce HIV viral loads by as much as 90% -- will enter further human trials this month, BBC News reports (BBC News, 6/8). The drug -- which is called PA-457 and is made from the bark of the European plane tree -- is the first in a new class of antiretroviral drugs called maturation inhibitors, which block formation of a protein that coats HIV, according to the company. Without the coating of the protein capsid, viral copies are released from the host cell but are unable to infect other cells. The drug targets strains of HIV that have become resistant to other antiretroviral drugs, according to Panacos. In an earlier trial, HIV-positive volunteers who took high doses -- 100 milligrams and 200 milligrams -- of PA-457 showed significant viral load reduction. In addition, genetic tests conducted on 21 of the 33 participants showed no evidence of resistance to the drug (Kaiser Daily HIV/AIDS Report, 8/24/05). In the trials, scheduled to being this month, researchers will analyze how the drug performs in combination with other HIV drugs in 48 HIV-positive people who have developed resistance to existing antiretroviral treatment, AFP/Yahoo! News reports (AFP/Yahoo! News, 6/7). In the study, participants will be given PA-457 or a placebo along with their existing medication. If the results from the trial are positive, larger studies will be required to see what combination of treatment works best, according to BBC News. The earliest the drug could be on the market is 2009 (BBC News, 6/8). PA-457 has been granted fast-track status by FDA (Kaiser Daily HIV/AIDS Report, 8/24/05).