Nov. 9, 1999 (Gaithersburg, Md.) -- An FDA advisory panel is contemplating the possibility of stepping up the role of tests to make sure that new strains of HIV are not resistant to drugs designed to fight the virus. The agency's Antiviral Drugs Advisory Committee recently began a two-day session on the subject.
There are close to 15 FDA-approved HIV drugs available, but resistant strains of the virus are emerging. Studies published in September in the JournaloftheAmericanMedicalAssociation found that the transmission of HIV strains that are resistant to drugs is becoming common among gay men in U.S. cities. Meanwhile, recent research has suggested that blood tests can be helpful when doctors are trying to choose drugs that an individual's particular strain of HIV won't resist.
Committee members expressed strong support for increasing the testing of viral resistance to anti-HIV drugs throughout the development of the drugs. Douglas Richman, MD, a pathology/medicine professor at the University of California at San Diego, presented recommendations for drug manufacturers' testing of HIV medications. He tells WebMD that although not all companies currently test during development, it will become standard. "It's on track," he says.
Panel chairman Scott Hammer, MD, emphasized that a key goal is better sensitivity among tests. He was optimistic. "Personally, I think that's coming," he said.
But challenges abound. Although knowledge on the utility of testing is growing rapidly, the field is rapidly evolving. There is no consensus on what degree of resistance to medications is considered to be normal and how much resistance will lead to negative outcomes. Additionally, there are often significant variations among different laboratories, and there is currently only a tiny public database of viral types that are known to be resistant. Guest panelist expert Douglas Mayers, MD, said that defining what degree of resistance would be acceptable "will be the real challenge."
There are other notable gray areas. For example, committee member Roger Pomerantz, MD, noted that modest resistance to a drug seen in the laboratory shouldn't necessarily prevent the therapy from clinical use, especially in combination with other medications. Mayers also explained that although resistant viral strains might appear in the laboratory, they don't always turn up in later research. And Richman noted that several studies have found both resistant and nonresistant HIV strains in the same patient.
The committee appeared to accept that resistance tests on combination HIV therapies are not likely to be feasible technically and economically.
FDA medical officer Andrew Dayton, MD, conceded that the agency's regulatory approach to tests is still emerging. "We're always kind of behind the times," he said.
Meanwhile, CDC Assistant Director for Infectious Diseases Jonathan Kaplan, MD, said recently that resistance monitoring is a "priority" for his agency. He said that the CDC is focusing on HIV patients who have never received prior treatment, while the National Institutes of Health is looking at patients who have previously been exposed to anti-HIV drugs.