July 26, 2012
New Drug Combo Shows Promise against TB, HIV Co-Infections
WASHINGTON — There may be a powerful new weapon in the fight against tuberculosis, a bacterial respiratory disease that kills an estimated 1.4 million people around the world each year. Early results of a clinical trial show a novel triple-drug combination destroys nearly 100 percent of the TB bacteria in infected patients -- within two weeks. While full treatment would take longer, the regimen promises to cut in half the duration of TB therapy for drug-resistant cases of the disease. And it could be a life-saver for hard-to-treat HIV-positive individuals who are co-infected with TB.
An estimated 25 percent of people infected with HIV, the virus that causes AIDS, die of tuberculosis because they cannot withstand the nausea, vomiting and loss of appetite that can be the debilitating side effects of the rigorous antibiotic regimen now used to treat TB.
The standard treatment now involves four doses of antibiotic drugs each day for as long as six months. If an HIV-positive patient is infected with multi-drug resistant TB, they face two to three years of treatment, including a daily injection for six months.
The new therapy consists of three drugs: an experimental compound called PA-824, an established antibiotic called moxifloxacin and pyrazinamide, the most powerful anti-TB drug now in use.
Daniel Everitt, co-researcher on the drug trial, is senior medical officer with the Global Alliance for TB Drug Development, which funded the study. He says HIV-positive patients co-infected with tuberculosis currently must take up to twelve pills per day -- if they can even tolerate the TB treatment.
“It’s a huge amount of drugs with all their interactions and side effects. So...we hope this will be a four-month regimen of just three drugs, which will be a major step forward for patients with HIV who have to take so many drugs currently,” Everitt said.
Everitt says, ideally, the three-drug anti-TB cocktail could be combined into a single pill.
The clinical trial involved a group of 85 TB-infected patients in Cape Town, South Africa. The cocktail's effectiveness was measured by comparing the amount of tuberculosis bacteria in the sputum of patients on the experimental combination therapy and those on a variety of other standard therapies within the first two weeks of the trial.
Researchers found the drug cocktail killed more than 99 percent of TB bacteria in the triple-combination group.
Because all but one of the three compounds is new in the treatment of TB, there is no drug resistance -- yet -- to the triple-combination therapy. Experts say that it could be used to treat regular TB as well as drug-resistant cases, in a fraction of current treatment times.
Everitt says the drug cocktail could have important cost-saving benefits as well: “For patients with drug-resistant TB, we’re expecting the cost of that to come down about ten-fold, to be one-tenth of the current drug-resistant treatment regimen -- which is very expensive because it (involves) so many medicines and it has to be taken for 18 to 24 months,” Everitt said.
Researchers caution the cocktail must still go through additional, larger trials before it becomes available as a treatment for TB.
An article on the triple-drug combination treatment for tuberculosis is published in The Lancet. The results of the drug trial were presented at the International AIDS Conference in Washington DC.