Effect Measure

For whatever reason, TB control is back on the front burner. TB remains a worldwide scourge and has always had a dedicated cadre of public health professionals battling it. Now they are getting some new ammunition and reinforcements. The Bill and Melinda Gates Foundation is weighing in with a substantial $280 million five year program, most of which goes to vaccine development. An effective TB vaccine is the Holy Grail of TB control. We know much more about the immune system than in the past, so maybe soon we’ll see the breakthrough everyone in the field has been hoping for. Until preventive efforts have reduced the disease, however, we’ll have to rely on anti-TB drugs and the Gates support will also be directed at better diagnostic tests and new drugs. In the drug area, there is news that a new combination of existing drugs might hasten TB cures. Current drug regimens require intensive therapy with four drugs for 6 months or more. Some of these drugs have unpleasant side effects and are costly so there is a serious compliance problem, which causes failed cures and in turn can lead to development of drug resistant forms of TB.

At a recent meeting of the American Society for Microbiology in Chicago a team from Johns Hopkins reported they had shortened the time to negative cultures to four months in active TB cases in Brazil by replacing the old line anti-TB drug ethambutol with a different drug, moxifloxacin. After only two months, 85% of the moxifloxacin group were negative compared to 68% of the ethambutol group and the treatment advantage was evident as early as two weeks. Development of new TB regimens seems to be finally making progress. The Hopkins team also reported that experiments in mice produced a “cure” in 10 weeks by using moxifloxacin with a higher dose of another drug in the combination, rifapentene. But another study in Africa showed less of an advantage. When moxifloxacin was substituted for yet another drug in the usual combination, isoniazid, the advantage at two months was 60% versus 55%. Moxifloxicin is much more expensive than either ethambutol or isoniazid so to make this work for global TB control will require a better understanding of what should be used with what and a confirmation of the effect.

But the possibility that two months can be shaved off the treatment regimen is a big deal. It’s not the end of TB but it’s an important tactical advance in a battle against an ancient and implacable foe. And if there is an effective TB vaccine in the next decade, well that is a Big Deal.

The threat of a catastrophic influenza pandemic is (rightly) occupying the attention of the public health community. But TB is a also a catastrophe, in slow motion. Winning a small battle isn’t winning the Big War. But we’ll take what we can get at this point and be grateful.


  1. #1 Liz
    September 20, 2007

    Thomas Goetz at Wired just reported on promising TB diagnostic advances, including a portable device that rivals the accuracy of cultures but takes hours rather than weeks.

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