Chinese researchers said Monday they have discovered an HIV-blocking agent that could be developed into a gel to limit the sexual transmission of AIDS.

Scientists from Hong Kong University said joint research with Shanghai Targetdrug Co., Nanjing University and City University of Hong Kong had discovered a molecule that blocks HIV from entering human cells.

Zhiwei Chen, director of the AIDS Institute of the University of Hong Kong Li Ka Shing Faculty of Medicine, said the potency of the TD-0680 molecule against sexually transmitted HIV was "encouraging".

The new molecule could be developed into a microbicide gel to "prevent HIV sexual transmission" by killing off the virus as it tries to enter the body.

This would give people, especially women, an "alternative method to protect themselves from the virus, in addition to condoms", Chen said.

"The ideal solution is to develop an effective vaccine. Since such a vaccine remains elusive, we must explore other strategies such as topical microbicide," he said.

The TD-0680 molecule is several times more potent than Maraviroc, a Pfizer-developed equivalent which has been approved by the US Food and Drug Administration for clinical treatment, the Chinese scientists said.

Unprotected sex accounts for more than 90 percent of AIDS infections in China, the researchers said in a statement.

Their work was published recently in the peer-reviewed Journal of Biological Chemistry.