It is shown to effectively lower the amount of virus in the blood to undetectable levels in 62 percent of people taking it in combination with other anti-HIV medicines.

Only one in three people who received a placebo plus other anti-HIV medicines had the amount of virus in the blood reduced to similar levels.

Research co-authored by the University of New South Wales' (UNSW) National Centre in HIV Epidemiology and Clinical Research (NCHECR) shows that the majority of patients who have not responded to traditional treatments have had good results from the new combination therapy.

The drug raltegravir is already available in Australia and is listed on the Pharmaceutical Benefits Scheme. Clinical trials show that it is safe, effective and with minimal side-effects when used with other anti-HIV medicines.

"This is the first drug in a new class of antiretroviral drugs called integrase inhibitors," said UNSW Professor David Cooper AO, the Director of NCHECR.

"The drug has a different mechanism of action, is very potent, seems very safe and has helped patients who have a virus that is resistant to older drugs and classes," said Professor Cooper.

Raltegravir effectively decreases HIV viral loads after 24 weeks of use among HIV-positive people who have not responded to other treatments, according to a study published last year in Lancet.

Raltegravir works by blocking an HIV enzyme called integrase. Integrase is one of the three enzymes necessary for HIV to replicate in the body, and integrase inhibitors stop HIV from inserting its genes into uninfected DNA. The other two enzymes necessary for viral replication, reverse transcriptase and protease, already are targeted by a variety of antiretrovirals.