Hope for new drugs for resistant TB
25 July 2012, 08:50
A new combination of three drugs killed 99% of patients' tuberculosis bacteria in two weeks, raising hope for a new weapon against increasingly resistant forms of TB, researchers said at the International AIDS Conference in Washington.
The combination of drugs includes the existing TB drug pyrazinamide, the Bayer AG antibiotic moxifloxacin that is now used off-label for patients with drug-resistant TB, and a new drug called PA-824 being developed by the New York-based TB Alliance, a non-profit research group that conducted the study.
What the combination lacks are any drugs in the rifamycins class, which pose the greatest threat of side effects for patients who also are being treated for infections with HIV.
The midstage study, reported also online in The Lancet to coincide with the presentation at the meeting, needs to be confirmed in larger and longer trials, but scientists say the drug cocktail could speed treatment and help reduce the emergence of resistant forms of tuberculosis.
"TB is the largest killer of Aids patients, and so in order to contain the Aids epidemic, we have to contain TB to a much greater extent," said Dr Mel Spigelman, chief executive officer of the TB Alliance.
"The results of this clinical trial give us the first indication that a new TB drug regimen - a combination of drugs - could be more effective than any of the existing TB drug regimens," Dr Spigelman said.
He said the combination is especially promising because it could be used to treat patients with both treatment-sensitive TB and TB strains that are resistant to two or more of the common drugs.
The findings come as mycobacterium tuberculosis is rapidly developing resistance to the world's most effective tools.
Study in South Africa
According to the World Health Organisation, in some parts of the world, one in four people with TB has a form of the disease that can no longer be treated with standard drug cocktails.
Even more deadly forms of TB are emerging. Dr Zarir Udwadia of the National Hospital in Mumbai, India, has identified more than a dozen cases of TB that cannot be killed by any existing form of treatment.
In the new midstage study conducted at two sites in South Africa, researchers tested the drug combination on 85 patients with TB. After two weeks, the new treatment combination was 99% effective at killing off TB bacteria in these patients.
A follow-up study of the treatment testing the drug combination over a two-month period already has begun and should be completed next year, Dr Spigelman said. Once that study is done, the group hopes to start large-stage clinical trials.
"The results look strongly promising from this early trial," Dr Mario Raviglione, director of the World Health Organisation's Stop TB Partnership, said in a statement.
"If further trials hold up, we may have a major solution for drug-sensitive TB and drug-resistant TB."
The study was funded by the Bill & Melinda Gates Foundation, the U.S. Agency for International Development and the British and Irish governments.