(CBS/AP)-- Federal drug regulators on Tuesday affirmed landmark study results showing that a popular HIV-fighting pill can also help healthy people avoid contracting the virus that causes AIDS in the first place. While the pill appears safe and effective for prevention, scientists stressed that it only works when taken on a daily basis.
FDA favors first drug for HIV prevention
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The Food and Drug Administration will hold a meeting Thursday to discuss whether Truvada should be approved for people who are at risks of contracting HIV through sexual intercourse. The agency's positive review posted Tuesday suggests the daily pill will become the first drug approved to prevent HIV infection in high-risk patients.
FDA reviewers conclude that taking Truvada pre-emptively could spare patients "infection with a serious and life-threatening illness that requires lifelong treatment."
Despite the positive results, reviewers said that patients must be diligent about taking the pill every day. Adherence to the medication was less than perfect in clinical trials, and reviewers said that patients in the real world may forget to take their medication even more than those in clinical studies.
More than one million people in the U.S. are living with HIV, according to AIDS.gov. About 20 percent of them are unaware that they have the disease. Men who have sex with men in the African American community are the most affected by the disease. More than 619,000 people with AIDS have died in the U.S. since the epidemic began in June 1981.
HIV attacks the immune system and, unless treated with antiviral drugs, develops into AIDS, a fatal condition in which the body cannot fight off foreign infections.
First announced in 2010, Truvada's preventive ability was hailed as a breakthrough in the 30-year campaign against the AIDS epidemic. A three-year study found that daily doses cut the risk of infection in healthy gay and bisexual men by 44 percent, when accompanied by condoms and counseling. Another study found that Truvada reduced infection by 75 percent in heterosexual couples in which one partner was HIV infected and the other was not.
The FDA's panel of advisers will take separate votes on whether Truvada should be approved for:
gay and bisexual men
men or women in relationships with HIV-positive partners
other people at risk of acquiring HIV through sexual activity
The FDA is not required to follow the advice of its panels, though it usually does.
Because Truvada is already on the market to manage HIV, some doctors currently prescribe it as a preventive measure. FDA approval would allow the drugmaker Gilead Sciences to formally market its drug for the new use.
But support for FDA approval is not unanimous. Some researchers stress that condoms remain the best weapon against AIDS, and a prevention pill is not the chemical equivalent.
"We know that if the person doesn't take the medication every day they will not be protected," said Dr. Rodney Wright, director of HIV programs at Montefiore Medical Center in New York. "So the concern is that there may not be adequate adherence to provide protection in the general population."
Wright, who is also chairman of the AIDS Health Foundation, added that some upcoming medications may be more effective at preventing infection than Truvada.
Researchers also worry about Truvada's mixed success rate in preventing infection among women. Last year a study in women was stopped early after researchers found that women taking the drug were more likely to become infected than those taking placebo. Researchers speculated that women may need a higher dose of the drug to prevent infection. They also said the disappointing results may have resulted from women not taking the pills consistently.
Still, many HIV patient advocacy groups say the drug should be a prescribing option to prevent HIV, alongside condoms, counseling and other measures.
"If we're going to reduce the more than 50,000 new HIV infections in this country each year, we need to increase the available options for people," said Ronald Johnson, vice president of AIDS United. He added that more studies are needed to determine the drug's effectiveness in women and other patient subgroups.
"The current state of the data warrants going forward, but we believe additional clinical trials should also go forward to broaden the use of Truvada."
Last month, AIDS United and more than a dozen other advocacy groups sent a letter to the FDA, urging approval of Truvada.
Foster City, Calif.-based Gilead Sciences Inc. has marketed Truvada since 2004. The drug is a combination of two older HIV drugs, Emtriva and Viread. Doctors usually prescribe the medications as part of a drug cocktail that makes it harder for the virus to reproduce. Patients with low viral levels are far less likely to develop AIDS.
Side effects with Truvada include diarrhea, dizziness, nausea and vomiting. More serious problems can include liver toxicity, kidney problems and bone thinning.