When scientists in Texas reported in January that they had successfully used antiretroviral drugs (ARVs) to prevent HIV transmission in lab mice, colleagues received the news with great enthusiasm and no small amount of concern. Positive study results like these offer hope that ARVs may someday help stem the rate of new infections worldwide, but public-health experts in the U.S. worry that they may also prompt people in affluent at-risk communities to leapfrog the emerging science and self-medicate. "It's inevitable," says Dr. Warner Greene, director of the Gladstone Institute of Virology and Immunology at the University of California, San Francisco. "Nobody wants to wait."
Indeed, some people are already putting medical theory into practice. "There's a philosophy in parts of the gay community that says its okay to take some risks in having sex," says Dr. Dan Bowers, a senior partner in Pacific Oaks Medical Group in Beverly Hills, Calif., one of the country's largest private practices treating the HIV/AIDS community. Based on results of lab studies that suggest ARVs may confer some protective benefit when taken prior to virus exposure, some people have begun self-administering the drugs like a morning-after pill, in the hopes that the drugs' pre-exposure prophylactic benefits may apply after unsafe sex too.
The antiretroviral drug tenofovir, for example, which was used in the recent Texas study, is often packaged as a potent cocktail with Viagra and Ecstasy or Valium, and sold in dance clubs for $100. Studies in monkeys in 2004 that suggested tenofovir could diminish HIV infection rates appear to have boosted underground sales of the drug, public health officials fear, and other studies among African women in Cameroon and Ghana, although not as successful, have further bolstered sales. A 2006 study by the Centers for Disease Control found that 7% of men who attended gay pride events in four U.S. metro areas used tenofovir as a prophylactic, while 20% said they knew other gay men who did. A more recent survey of 1,819 gay or bisexual men in California, published in the Journal of AIDS, found a low rate of prophylactic ARV use less than 1% but concerns still exist.
"We have a considerable number of patients who are very well read," Bowers says "They find these studies faster than we do." Even though most of these PrEP (or pre-exposure prophylaxis) studies are conducted in animals, they often give people a "false sense of protection and lead to less condom usage," says Bowers, particularly among highly sexually active individuals. Last spring, following the buzz over studies of tenofovir and emtricitabine, the same drug combo used in the recent Texas mice study, in preventing transmission of SIV (the primate-specific cousin of HIV) in macaque monkeys, Bowers was compelled to respond in his column in HIV Plus magazine, warning that "society once again is moving ahead of science. ... This is definitely not the time to be leaving condoms behind."
Still, says Bowers, who is also a frequent contributor to the "Ask the Doc" forum on the AIDS Education Global Information System website, keeping the AIDS pandemic in the news is vital: "Any press is good press if they spell your name right," Bowers says, adding that the complex science needs to be explained to the public in easily understood ways. That message, however, is often conflicted. Some doctors have said they're willing to give tenofovir as a preventive to their very sexually active patients, even in the absence of conclusive scientific evidence that it works.
Though initial human studies of tenofovir alone have produced encouraging results, none have shown 100% protection, raising ethical issues and, in some cases, halting trials: In 2004 and 2005, AIDS activists notably, a Paris-based chapter of ACT UP protested ARV trials in Cameroon and Cambodia, questioning who would pay for long-term health care for the participants and whether the drugs would cause harmful side effects. Those trials were stopped.
Doctors also worry that over the long term, people may build up resistance to ARVs dangerous if a non-infected person takes the drugs prophylactically, then becomes infected later or that HIV itself will become drug resistant. Greene says individuals using a single antiretroviral drug run a higher risk of developing resistance combo drugs seem to lower the probability. Human trials of combined retrovirals are under way in high-risk groups such as sex workers and gay men, both in the U.S. and elsewhere but results of those studies won't be available for at least another year.
Meanwhile, physicians are seeing an increase in HIV infection rates among sexually active gay men in the U.S., accompanied by rising syphilis rates, which can complicate treatment. In Africa, Greene says, there are "some islands of success" but troubling increases in HIV transmission in other regions. Public-health experts acknowledge that there is no one magic bullet, no single approach to defeat AIDS, and that even the potential success of prophylactic antiretroviral drugs is only one arrow in the medical quiver. "There are all kinds of variables," Greene cautions, including drug-resistance issues, evolving viruses, individual patterns of infection and complications due to other diseases like herpes, not to mention human behavior and cultural traditions that can interfere with prevention and treatment.
And so the news out of Texas was good, but worldwide the battle against AIDS has many fronts, with no sign that the pandemic will be defeated soon. "I don't think drugs can give 100% protection," Dr. Bowers says. "Using HIV drugs may reduce the rate but they are not going to make that zero."