Additional Studies Needed to Assess Effectiveness of Tenofovir for Prevention

At the XVI International AIDS Conference held August 12, 2006 in Toronto, Canada, Family Health International presented clinical trial data showing that the drug tenofovir is safe for use among HIV-uninfected West African women at high risk of infection. Additional studies are needed to determine whether or not tenofovir — which is currently widely used to treat HIV infection — may also prevent infection.

"These results are good news for HIV prevention," said Dr. Willard Cates, Jr., Family Health International's President for Research and principal investigator for the study. "Now that tenofovir has been demonstrated to be safe and acceptable for this population of HIV-negative African women, it is crucial to determine if tenofovir can effectively reduce risk for HIV infection. Our study lays a foundation for further studies involving more participants that can answer that effectiveness question. We need to move forward quickly to determine if use of tenofovir or other oral antiretroviral drugs — in conjunction with other proven prevention strategies — can reduce HIV risk."

Current HIV prevention programs stress abstinence, being faithful to uninfected partners, and — if neither is possible — using condoms. Despite knowledge of these prevention strategies, some 14,000 people are infected with HIV each day. Moreover, many sexually active individuals, especially women, have difficulty ensuring faithfulness of partners or negotiating condom use in their relationships, and additional prevention strategies are needed. If tenofovir were shown to be effective in protecting against HIV infection, it could substantially reduce the number of people who become infected worldwide. This could have an especially large impact in sub-Saharan Africa, where 65 percent of all new HIV infections occur.

The study, supported by a grant awarded to FHI by the Bill & Melinda Gates Foundation, tested a daily oral form of tenofovir among 936 women at high risk of HIV infection in Ghana, Cameroon, and Nigeria. Half of the women were randomized to receive daily tenofovir and half were randomized to receive a daily placebo (a tablet that looked and tasted like tenofovir but did not contain any drug). The women were then followed for up to a year.

The study raised no safety concerns for tenofovir use in this specific population of West African women. Of particular interest was the possible effect of tenofovir on the liver and kidneys, but no significant differences in severe liver or kidney abnormalities were found between women in the tenofovir group and those in the placebo group. The numbers of other side effects or health changes were also similar between the two groups.

Overall, a total of eight HIV infections occurred among the women in the study, including both those randomized to receive either tenofovir or placebo. These infections were fewer than initially estimated to occur in the study, and resulted in data insufficient to determine tenofovir's effectiveness against HIV infection. Additional studies with more participants are required to determine efficacy.

HIV prevention services provided within the trials may have contributed to the low HIV infection rate. At monthly visits during the study, all participants received HIV prevention counseling, were provided with and encouraged to use male condoms during all sexual acts, and were treated for sexually transmitted infections, as medically indicated. All these measures have been shown to reduce the risk of HIV infection.

Tenofovir is being studied as a possible HIV prevention tool because, in infected individuals, it stops HIV from invading healthy cells. It is long-lasting, has relatively few side effects, and most strains of HIV only slowly develop resistance to it. Tenofovir is approved by regulatory agencies and already used in many countries as part of a drug combination to treat HIV. Treatment with tenofovir and other antiretroviral drugs is gradually increasing; however, for every person treated in 2005, another seven became infected. Thus, HIV prevention efforts remain crucial.

The study findings were presented by FHI at an oral abstract session at the International AIDS Conference.

Source:

Peterson L, Taylor D, Clarke EEK, et al. Safety and preliminary effectiveness of tenofovir disoproxil fumarate (TDF) for prevention of HIV infection in women [abstract]. XVIth International Conference on AIDS, Toronto, Canada, August 12, 2006.