Tests of a new HIV drug on monkeys have shown promising results, scientists have said.
The research could lead to new therapies for HIV being developed
The drug targets the HIV enzyme called integrase, which helps the virus invade immune cells and replicate.
Researchers at the pharmaceutical company Merck & Co, which is developing the drug, published their results in Science.
UK experts said drugs which blocked the action of the enzyme were "a promising new generation of anti-HIV drugs".
Two other enzymes made by HIV, called reverse transcriptase and protease, are already
targeted by drugs used to fight the virus. Both enzymes help the virus insert its genetic material into infected cells.
Integrase instead helps the HIV genes bind with the patient's own DNA, which allows the virus to hide inside cells and avoid therapy.
Scientists have been attempting to find ways to block the enzyme's action for some time, but it had been difficult to find an effective method.
Researchers from Merck treated monkeys with an integrase inhibitor drug code-named L-870812.
The drug was given to six monkeys newly infected with a hybrid monkey-human
version of HIV.
In four monkeys, the virus dropped to undetectable levels, and all six saw only a slight decrease in numbers of CD4 white blood cells, which play a crucial role in the immune system.
This meant that the monkeys were able to fight the virus with a strong immune response.
Six untreated monkeys saw their CD4 levels plummet and viral levels soar.
Researchers found the treatment was most effective when used at the start of an infection before HIV had caused serious damage.
Further research is now being carried out examining the drug's effect on a small number of patients. If the results are promising, larger-scale studies will go ahead next year.
Dr Daria Hazuda, of Merck Research Laboratories in West Point, Pennsylvania, wrote in Science: "Integrase inhibitors represent a new class of agents to treat HIV-1 infection."
He said they could be particularly useful in patients who had not been exposed to other medications, and patients with viruses which were resistant to existing antiretroviral drugs.
Michael Carter, of the National Aids Manual, told BBC News Online: "Integrase inhibitors look like being a promising new generation of anti-HIV drugs, and these data from a study in monkeys are encouraging."
He said there was a need for new drugs which were easy to take and caused few side-effects.
"I've little doubt that some of the next generation of anti-HIV drugs, hopefully including integrase inhibitors, will revolutionise HIV treatment.
"In the meantime, the emphasis for people with HIV has to be using the drugs we have to their fullest potential."