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TB Notes 4, 2002

Update from the Research and Evaluation Branch

Update on Study 22

The major report from TB Trials Consortium (TBTC) Study 22 was published in the August 17 edition of The Lancet. The article presents the findings from the HIV-negative arm of this important trial,1 which evaluated a regimen of once-weekly isoniazid and rifapentine given during the continuation phase of therapy (from week 9 to week 24 of treatment), as an alternative to the standard twice-weekly regimen of isoniazid and rifampin. TBTC investigators found the once-weekly regimen to be safe and effective for HIV-negative patients without signs of advanced TB (i.e., those with no lung cavitation identifiable on chest x-ray).

Study 22 enrolled 1,004 HIV-negative patients with active TB disease who had completed 8 weeks of intensive TB therapy with the four frontline TB drugs – isoniazid, rifampin, pyrazinamide, and ethambutol. Enrolling sites were located in New York City, NY; Newark, NJ; Baltimore, MD; Atlanta, GA; San Diego, CA; Los Angeles, CA; Phoenix, AZ; Chicago, IL; Fort Worth, TX; Winnipeg, Canada; Denver, CO; Washington, DC; Durham, NC; Miami, FL; Little Rock, AR; Hines, IL; Houston, TX; San Antonio, TX; San Francisco, CA; Charlotte, NC; and Nashville, TN. Patients were randomly assigned to one of two groups during the 16-week continuation phase of TB treatment. One trial group received once-weekly isoniazid and rifapentine, the first new TB-specific drug approved by the Food and Drug Administration in 30 years. The other group received the standard therapy of twice-weekly isoniazid and rifampin.

Both groups of patients were then followed for 2 years. Forty-six (9.2%) patients who took the once-a-week regimen either relapsed or experienced treatment failure. Twenty-eight (5.6%) patients who took the twice-weekly regimen relapsed or had a treatment failure. In a life table analysis, these rates were 10.3% and 5.9%, respectively. In a proportional hazards regression model, which adjusted for imbalances in key risk factors at enrollment, five factors were significantly associated with risk of failure or relapse: 1) positive sputum culture at 2 months, 2) cavitation on chest x-ray, 3) being more than 10% underweight at diagnosis, 4) having bilateral disease on chest x-ray, and 5) being of white race/ethnicity. The difference between treatment arms was not statistically significant in this regression analysis. Importantly, the rates of failure or relapse among patients with no cavitation on x-ray were quite similar in the two treatment arms (2.9% vs. 2.5%, respectively). Mortality and toxicity were similar in the two groups. The study investigators concluded that the once-weekly regimen was not as efficacious as the twice-weekly regimen, but that the once-weekly isoniazid and rifapentine regimen performed well in HIV-negative TB patients who did not have cavitation on chest x-ray. These investigators recommend that this regimen be considered for use in such patients. Revised ATS/CDC treatment recommendations are expected to appear in late 2002, and will address the use of this regimen.

Since the once-weekly isoniazid and rifapentine regimen is administered less frequently than the standard regimen, costs associated with directly observed therapy are diminished,2 and 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. CDC is interested in learning of programmatic experience with this regimen in appropriately selected HIV-negative TB patients.

—Reported by Andrew Vernon, MD, MHS
Div of TB Elimination


Findings from the HIV-positive arm were published in Lancet in 1999 (Vernon A, Burman W, Benator D, Khan A, Bozeman L. Relapse with rifamycin mono-resistant tuberculosis in HIV-infected patients treated with supervised once-weekly rifapentine and isoniazid. Lancet 1999;353:1843-1847).

Taylor Z, Qualls N, Vernon A, Villarino E, O'Brien R. A prevention effectiveness study of rifapentine in the continuation phase of therapy for active pulmonary tuberculosis. Abstract. Am J Respir Crit Care Med 2000; 161: A524.


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
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