New Class of Antiretrovirals on the Horizon, Time Reports
In a special report on "The Future of Drugs," this week's issue of Time magazine features "the most promising new class of anti-HIV drugs under review" -- entry inhibitors. This class of molecules "prevents HIV's entry into healthy immune cells," thereby inhibiting infection. Unlike currently available antiretrovirals, which target the virus once it invades cells, entry inhibitors attack the virus before it enters healthy immune cells. Dr. David Ho, director of the New York-based Aaron Diamond AIDS Research Center, said, "Working outside the cell gives [entry inhibitors] in theory a major advantage because cell membranes can present barriers to some drugs, and some have molecules that pump out drugs that manage to get inside." This class of drugs would avoid these obstacles, and therefore could be effective at lower dosages than existing treatment options, which may be "safer for the patient in the long run." If proven successful in human trials, entry inhibitors could become "a welcome and badly needed addition to the HIV drug arsenal," as the "dual problems" of resistance and toxicity associated with current HIV drugs are "beginning to tarnish the promise they once held."
Coming Down the Pipeline
Pharmaceutical company Trimeris, based in Durham, N.C., is in the final stages of human testing with one entry inhibitor candidate, and is in the earliest phases of human trials with a second candidate. "Other biotech firms ... are right behind it," Time reports, including Tarrytown, N.Y.-based Progenics Pharmaceuticals. According to Trimeris' studies, neither drug has shown to cause "serious toxic side effects" associated with current HIV/AIDS therapies, such as nausea, vomiting and fat metabolism abnormalities. Among the 70 advanced AIDS patients participating in Trimeris' trials, 56% showed "sharp declines in the amount of HIV in their blood -- at least tenfold below their starting levels and in some cases to levels undetectable by current tests." Trimeris' product currently comes in the unwieldy form of a twice-daily injection, though the company is trying to develop an easier way to administer the molecule, perhaps through a skin patch.
Meanwhile, scientists are investigating other molecules that could interfere with HIV's reproductive cycle at "critical points," Time reports. Of particular interest would be a molecule that "could prevent HIV from inserting its genes into its host's genome," which would not only provide a new treatment option but also complement existing therapies. According to Ho, "Combination therapies will be where the action is for the foreseeable future, as no single drug is sufficient to keep HIV at bay" (Park, Time, 1/15).