A gel that has been shown to reduce the risk of HIV infection in women during vaginal sex has also shown promise towards preventing transmission during anal sex, according to US researchers.

“HIV was significantly inhibited in tissue samples from participants who used tenofovir gel daily for one week compared to tissue from participants who used the placebo gel,” the study said.

The results came from the first clinical trial of tenofovir gel for rectal use, and were released at a medical conference in Boston.

The study size was small, comprising just 18 men and women who were sexually abstinent and HIV negative and who used the rectally applied gel for a week.

Researchers at the University of California, Los Angeles and the University of Pittsburgh then took biopsies of rectal tissue from the subjects and exposed the tissue to HIV in a lab to see how the product protected against infection.

They also tested an oral tablet and a single daily dose of rectal gel, and found those methods provided no protection against HIV.

“We are very encouraged about these findings that indicate applying tenofovir gel topically to the rectum could be a promising approach to HIV prevention,” said lead author Peter Anton, director of the Centre for Prevention Research at UCLA.