Two experimental AIDS drugs designed to fight resistant HIV strains are showing promising preliminary results, researchers said Wednesday.
One, called elvitegravir, is part of a new class of drugs known as integrase inhibitors and has shown evidence of being more potent than currently used drugs.
The second, called TMC278, is a variation of an existing class of drugs known as reverse transcriptase inhibitors, but shows fewer side effects and appears to work against some resistant strains of HIV, researchers reported at the Conference on Retroviruses and Opportunistic Infections at the Los Angeles Convention Center.
The preliminary findings on the two drugs followed presentations Tuesday about two other HIV drugs that are closer to receiving federal approval -- raltegravir, an integrase inhibitor from Merck & Co., and maraviroc, a drug from Pfizer Inc. known as a CCR5 inhibitor. Both drugs were hailed as potentially among the biggest developments in HIV therapy since the mid-1990s.
Together, the presentations on all four drugs seemed to herald a long-awaited blossoming in new ways to treat the estimated 15% to 20% of patients who face full-blown AIDS because their viruses have grown resistant to other drugs.
Dr. Daniel Kuritzkes, director of AIDS research at Brigham and Women's Hospital in Boston who was not involved in any of the research, said he was excited by the possibility of so many new drugs that could attack the virus with a variety of methods. More methods mean less chance for the virus to mutate into a resistant strain, he said.
"We have every expectation we can suppress the virus in the vast majority of patients," Kuritzkes said.
Elvitegravir, developed by Foster City, Calif.-based Gilead Sciences Inc., works like other integrase inhibitors by blocking one of three enzymes crucial to HIV for replication inside human cells.
Because the drugs use a different strategy than other drugs, doctors hope they will be effective in patients whose virus has become resistant to the 20-odd approved drugs.
Dr. Andrew Zolopa of Stanford University studied 278 patients who were already receiving standard HIV drugs. In addition to those drugs, one group received a 50-milligram dose of elvitegravir, one received a 125-milligram dose and a third received a protease inhibitor.
