The HIV virus

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[NEW DELHI] A vaginal gel containing the anti-HIV drug tenofovir is safe for daily use by women, a study shows.

The research was presented at Microbicides 2008, an international microbicides conference, in Delhi, India, this week (February 25).

Tenofovir is one of the primary antiretroviral drugs. It targets HIV by blocking the action of a key enzyme needed for the virus to replicate.

The Microbicides Trials Network (MTN) — sponsored by the US National Institutes of Health — conducted phase II trials on tenofovir gel in India and the United States in 2007, to test whether it is safe for women to use the gel daily instead of before having sex, and whether women complied with the procedure correctly and willingly.

The six-month study compared tenofovir with a placebo in 200 sexually active, uninfected women. It found the gel was safe — with no effects liver, blood or kidney function — both when it was used daily for a period of six months and before each act of sex.

The study also found high levels of compliance — over 80 per cent — Sharon Hillier, director at the Department of Obstetrics, Gynaecology and Reproductive Sciences at the University of Pittsburgh, and principal investigator of Microbicides MTN, said at the conference.

Over 90 per cent of the women involved said they would use such a gel if it were found to be effective against HIV.

A series of trials in Africa and the United States over the next two years will study if the drug is absorbed into the foetus during pregnancy, dose absorption in women and whether the drug is more effective as an oral pill or vaginal gel.

"The oral route versus topical application (of an anti-HIV drug) is the key scientific question," Hillier told SciDev.Net.

Between 70 and 90 per cent of HIV infections in women are due to heterosexual intercourse. Women are biologically more vulnerable to HIV infection as the cells in the lining of the female genital tract rupture more easily, making it easier for the virus to enter.

The tenofovir results will be encouraging to the microbicide research community who have faced a series of setbacks in recent years, including the early closure of trials for cellulose sulphate microbicide (see Safety concerns halt trials of HIV microbicide) and the announcement this month that a microbicide gel based on a seaweed extract, Carraguard, failed to prevent HIV transmission (see Anti-HIV gel fails to prevent infection).