Antibiotic Found Effective On Drug-Resistant Tuberculosis

Mycobacterium tuberculosis bacteria (CDC)

Researchers in the U.S. and Korea found the antibiotic linezolid largely effective in treating patients with extensively drug-resistant tuberculosis, who had not responded to previous treatments. The findings of the team led by Clifton Barry of the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, and Sang-Nae Cho at Yonsei University in Korea, published their findings in today’s issue of the New England Journal of Medicine.

Extensively drug-resistant tuberculosis is a form of that disease resistant to at least four of the drugs most often used to treat TB. While total numbers of cases are small, the authors cite World Health Organization data showing 77 countries reporting at least one case by the end of 2011, with 57 cases reported in the U.S. between 1993 and 2010.

The study enrolled 39 adult patients with chronic extensively drug-resistant tuberculosis in two Korean hospitals in a clinical trial tested linezolid, marketed by Pfizer as Zyvox, who received the antibiotic in a daily 600-mg dose along with their existing treatments. The group was split between patients who received the drug immediately and those who were delayed by two months. After no longer testing positive for the bacterium or after four months of therapy, participants were then randomly assigned for the next 18 months to continue taking either a daily 600-mg dose of linezolid or a daily 300-mg dose.

The drug showed an effect after four months, 15 where of the 19 patients in the immediate start-group and 7 of 20 patients in the delayed-start group no longer tested positive for tuberculosis. After six months of treatment with the drug, 87 percent (34 of 39 patients) no longer tested positive for tuberculosis.

A large percentage of the patients, 31 of 39 or 82 percent, reported adverse effects from the drug. The authors report that most of these events were resolved quickly after briefly stopping the drug or using the lower 300-mg dose. While 13 patients completed treatment and have not had a relapse in the 12 months after treatment ended, 4 of the 38 patients (11 percent) who used the drug for six months or more acquired resistance to linezolid.

Linezolid was approved in 2000 to treat drug-resistant bacterial infections. The authors report that earlier lab tests showed activity by linezolid against multi- and extensively drug-resistant tuberculosis, as did case reports and retrospective studies.

Read more:

• GlaxoSmithKline to Open its Clinical Trial Data
• Latent Tuberculosis Test Devised for Single Chip
• Companies Among Gates Foundation TB Biomarkers Awardees
• Commercial TB Tests Turn Up High False-Positive Rates

*     *     *