16 May 2011 - Denver, Colorado, USA - The results of a US government trial suggest that latent tuberculosis (TB) infection in countries with low-to-medium incidence of the disease can be treated with a much simpler and shorter course of drugs than the one currently recommended.
The results showed that a supervised once-weekly regimen of rifapentine and isoniazid taken for three months was just as effective as the standard self-administered nine-month daily regimen of isoniazid and was completed by more participants.
"Although the standard regimen is very effective in treating latent TB infection, ensuring that those who need treatment both begin and complete the lengthy, cumbersome isoniazid regimen is challenging," said Dr Thomas Frieden, the director of the US Centers for Disease Control and Prevention (CDC). "New, simpler ways to prevent TB disease are urgently needed, and this breakthrough represents one of the biggest developments in TB treatment in decades."
The trial tested the effectiveness of this new preventive TB treatment among people with latent TB infection who are at high risk for progression to TB disease. It lasted approximately 10 years and included 8053 participants over the age of two who lived in countries with low or medium TB incidence, with the majority from the USA or Canada. Additional participants were recruited in Brazil and Spain. Because of a known drug interaction between some anti-HIV drugs and rifapentine, HIV-infected persons taking antiretroviral drugs were not eligible for enrolment in the study.
In the randomized trial, participants received one of two preventive treatment options. The first consisted of a weekly dose of rifapentine and isoniazid given under supervision and the second - the current standard treatment - consisted of a daily dose of isoniazid for nine months, without supervision.
Each participant was evaluated for adverse effects, adherence to treatment, survival, and development of TB disease for a total of 33 months after the date of their enrolment.
The new regimen was found to be safe and as effective as the standard regimen in preventing new cases of TB disease, with very few cases of TB disease developing in either study arm. Seven cases occurred among those receiving the new treatment regimen compared to 15 among those receiving the standard treatment. In addition, 82 percent of the participants completed the new, shorter regimen, compared to 69% who completed the standard regimen.
The CDC is reviewing the data and will begin work on new guidelines for using the new course of treatment in the USA. Researchers caution that these results are only directly applicable to countries with low-to-medium incidence of TB.
The CDC says that additional studies will be needed before the new treatment can be recommended in countries with a high incidence of TB, especially those with high HIV prevalence and where the risk of TB re-infection is greater.
The research was conducted through the TB Trials Consortium (TBTC), a CDC-funded partnership of domestic and international clinical investigators who conduct research on the prevention and treatment of TB.