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New data released today by the Tuberculosis Trials Consortium (TBTC) confirms that a once-weekly TB regimen, initiated after the first eight weeks of therapy, is a viable option for selected patients being treated for active TB disease.

Supported by the Centers for Disease Control and Prevention, the TBTC is a network of 23 clinical research facilities, including the Duke University Medical Center and Durham Veterans Affairs Medical Center (DVAMC).

In this TBTC study, published in the August 17, 2002 edition of The Lancet, investigators evaluated a regimen of once-weekly isoniazid and rifapentine given during the continuation phase of therapy (from the ninth to 24th week of treatment), as an alternative to the standard twice-weekly regimen of isoniazid and rifampin in a group of HIV-negative TB patients. TBTC researchers, including Carol Dukes Hamilton, M.D., at Duke/DVAMC, found the once-weekly regimen to be safe and effective for HIV-negative patients without signs of advanced tuberculosis (i.e. those with no lung cavities identifiable on chest x-ray).

To identify those patients in whom a weekly therapy would be possible, more than 1,000 HIV-negative patients with active TB disease completed eight weeks of intensive TB therapy with the four frontline TB drugs -- isoniazid, rifampin, pyrazinamide and ethambutol -- before being randomly assigned to one of two groups during the 16-week continuation phase of TB treatment. One trial group received isoniazid and rifapentine, the first new TB-specific drug approved by the Food and Drug Administration in 30 years, once a week. The other group received the standard therapy of twice-weekly isoniazid and rifampin.

Both groups of patients were then followed for two years. Nine percent (46 patients) of those who took the once-a-week regimen either relapsed or experienced treatment failure. Six percent (28 patients) who took the twice-weekly regimen relapsed or had a treatment failure.

Overall, the relapse rate in the once-weekly arm was slightly higher. However, when researchers reviewed data on those patients without lung cavities, they found that the relapse rates were comparable (about 3 percent in both treatment arms). Therefore, researchers were able to identify a group of HIV-negative patients in whom the once-a-week therapy would be as successful as other currently approved treatment regimens.

Since the once-weekly isoniazid and rifapentine regimen is administered less frequently than the standard regimen, adherence may be improved, helping to cure more HIV-negative TB patients and prevent further TB transmission. The once-weekly regimen is not recommended for HIV-infected TB patients.