HIV Prevention Pill
Clears Key Safety Hurdle
By MARILYN CHASE
August 12, 2006 9:54 a.m.
TORONTO -- A controversial prevention pill to shield people from infection by the AIDS virus cleared a key safety hurdle during a small test, which also offered intriguing hints that the drug could prove effective.
The pill's preventive effects could have been due to the play of chance, and scientists downplayed them until they see the results from larger trials now under way in sites around the world. Still, the latest findings are likely to garner widespread attention as attempts to outpace the spread of HIV infection continue to fall short and doctors place more hope in prevention.
Separately, Merck & Co. researchers here unveiled a late-breaking study showing that a new drug aimed at longtime AIDS patients with resistant virus may also work for new patients as well as a rival drug.
• The XIV International AIDS Conference will be held in Toronto, Aug. 13-18, 2006
The test of the prevention pill involved 400 women in Ghana, half taking the drug tenofovir, sold as Viread by Gilead Sciences Inc., for one year. The other half took a placebo, or dummy pill. Another 400 women in Cameroon and 136 in Nigeria took the pills for a short time before activist protests and lab glitches aborted those trials.
HIV infections occurred in two women taking Viread, and in six women taking the placebo -- a finding sure to stoke both hope and controversy. The study is being presented at the XVI International AIDS Conference here.
Despite prior concerns about drug toxicity to the kidney, liver or bones, Viread appeared safe and generally well tolerated. Volunteers reported stomach pains and headaches, along with malaria, an unrelated illness.
Researcher Ward Cates, president of research at Family Health International of Research Triangle Park, N.C., cautioned against reading too much into the lower rate of infections in the drug group.
"This isn't statistically significant," Dr. Cates stressed in an interview. "Because the numbers were low, we could have observed this [infection rate] by chance. It's important that we have additional studies to determine if it is effective and, if so, how effective."
Still, it's "encouraging that there were fewer infections in the tenofovir group than the control group," said Helene Gayle, CEO of CARE and a former official of the Bill and Melinda Gates Foundation, which funded the studies.
The Centers for Disease Control and Prevention (CDC) is funding further studies in Botswana, Thailand and the U.S. The National Institutes of Health is funding a study in Peru. The tests, involving a total of 4,600 people, could settle the efficacy question by 2008, Dr. Cates said.
With an AIDS vaccine widely believed to be at least a decade away, researchers are seeking other tools-from pills and gels to circumcision-to shield people at extreme risk of AIDS. Controversy has dogged the pill studies over an array of issues, chiefly a demand by Paris activists that infected volunteers get free lifelong treatment. Family Health International said it has contracted with local groups to give needed care to its volunteers.
The prospect of an AIDS preventative-known as known as PREP for pre-exposure prophylaxis-also raises the prospect of eroding safe behavior. Amid rumors of PREP use on the gay party circuit, some public health officials fear a prevention pill could inspire unsafe sex, and increase HIV. Viread and Truvada, a related combo pill also being tested as a preventative, already are big-selling AIDS treatments for Gilead, of Foster City, CA. But wary of appearing promotional, Gilead limited its role in the prevention studies to supplying free pills.
Now, amid fresh hopes, the International AIDS Society is holding a session at the Toronto meeting entitled "What if PREP works?" to hammer out the most safe and ethical and way to distribute a prevention pill to people at high risk of contracting HIV.
The Merck drug, code-named MK-0518, is the company's lead compound in a new family of drugs known as integrase inhibitors, because they block an enzyme needed by the virus to slip its genes inside the DNA of human cells and replicate.
Now MK-0518-already seen as promising for longtime patients-looks effective as an early treatment, a company scientist said. In a double-blind study, 160 volunteers were given MK-0518 as part of a drug cocktail, and to 38 were given Bristol-Myers Squibb Co.'s Sustiva in a cocktail.
After 24 weeks on the Merck cocktail, 85% to 95% of volunteers experienced a drop in blood levels of virus to undetectable levels. That's comparable to effects seen in 92% of volunteers on the Sustiva cocktail, said Robin Isaacs, Merck's executive director of clinical research on infectious diseases.
Merck plans a 2007 filing for market approval of MK-0518 to treat longtime patients, but will need to launch larger studies to clinch its approval as an early treatment for new patients, Dr. Isaacs added.
Write to Marilyn Chase at marilyn.chase@wsj.com |
