A new drug for HIV has produced highly promising results in trials, when combined with an existing treatment, researchers say.
New HIV drugs are needed
Darunavir was given by a Spanish team to patients with advanced HIV infection, in tandem with a low dose of the current antiretroviral ritonavir.
There is a need for new antiretroviral drugs, as current treatments often start to fail after several years.
The study by a Barcelona hospital team is published online by The Lancet.
Darunavir is a new protease-inhibitor, a class of drugs which stop HIV replicating by blocking the action of the protease enzyme.
Patients either received a current combination therapy alone, or the same combination augmented with twice daily doses of darunavir and ritonavir.
The researchers assessed the impact of the drugs by measuring the amount of HIV genetic material (RNA) in the patients' blood after 48 weeks.
They found that 61% of those taking the new drug achieved a 10-fold drop, compared with just 15% of those in the control group.
Almost half (45%) of those taking darunavir-ritonavir reduced their HIV RNA concentrations to below 50 copies per ml of blood - the lowest recordable value.
Only 10% of the control group achieved this.
The number of key CD4 immune system cells in patients taking the new drug combination also increased by an average of 102 cells per micro litre, compared to just a 19 cells per micro litre increase in the control group.
Previous studies have shown less than 10% of patients on regular combination therapy whose CD4 count increases by more than 100 cells per micro litre progressed to Aids or died within three years.
In comparison, 85% of those with a CD4 count increase of less than 25 cells per micro litre developed Aids, or died in the same time scale.
Dr Rodger MacArthur, of Wayne State University, Detroit, said further research was needed fully to establish the impact of the drug.
But he said: "For now, all of us treating HIV-infected individuals in clinical practice will probably rejoice in the availability of darunavir, since it seems to be a safe, well tolerated, and truly effective agent against multi-drug resistant HIV."
Roger Pebody, a treatment advisor at the Terrence Higgins Trust, said: "Darunavir can make a real difference to people with HIV who are resistant to other drugs.
"It's one of a handful of new treatments that are transforming the outlook for people who are unable to control their HIV with existing combination therapies.
"It is fantastic that treatments are moving forward and offering hope for people who may have previously found their treatment options severely limited."
Keith Alcorn, senior editor of the information service Aidsmap, said: "We can now begin to think in terms of three or four successive drug combinations for people with HIV, each of which will achieve undetectable virus levels for years at a time."