Shorter, weekly, 2-drug TB regimen halves risk of active disease

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Carol Dukes Hamilton, MD, of FHI in Durham, North Carolina

Randomized clinical trial of high-risk clients finds three-month, once weekly, two-drug TB treatment outcomes exceed those of nine-month, once daily, one-drug regimen

Nine-month isoniazid treatment has been highly efficacious in the treatment of latent tuberculosis (TB) infection, but the low regimen completion rate – 30 to 60 percent – has hindered treatment success and a shorter regimen is needed, said Carol Dukes Hamilton, MD, of FHI Thursday morning at the 49th Annual Meeting of the Infectious Diseases Society of America.

She then presented the preliminary results of the Centers for Disease Control and Prevention (CDC)-funded “PREVENT TB Study” during a talk on latent TB infection and new options for short-course treatment. Aiming to increase tuberculosis (TB) treatment uptake and adherence – two key factors in treatment success, researchers at FHI and the TB Trials Consortium of the CDC looked at three months of once-weekly rifapentine plus isoniazid or INH, as compared to nine months of daily INH for treatment of latent TB infection.

The “3HP arm” received directly observed therapy (DOT) daily (12 doses), and those in the “9H arm” self-administered their weekly regimen (270 doses). The study was not placebo controlled and all subjects were followed for 33 months.

Researchers found that 3HP by DOT was at least as effective as 9H by self administration, and the TB rate among the 3HP group was approximately half that of 9H. Eighty-two percent of those in the 3HP arm completed treatment, versus 69 percent in the 9H arm, and 3HP was safe relative to 9H.

Participants in the study were tuberculin skin-test positive and close contacts with culture-positive TB patients. While HIV-positive persons were included in the cohort, the preliminary results only looked at HIV-negative adults older than two years of age.  Tolerability and efficacy among this population is in development, as is the assessment of complete tolerability among children.

People with lantent TB are infected with M. Tuberculosis but do not have active TB disease and are asymptomatic. Although they are not infectious, five to 10 percent of those with latent TB will develop active TB at some point in their lifetime.

The study manuscript has been submitted and is awaiting publication in a scientific journal, Hamilton said. She added that the 2,000 latent TB infection guidelines from the IDSA, American Thoracic Society and the CDC are currently being updated to reflect the recommendation that three-month, weekly therapy be used as an alternative therapy to nine months of INH.

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