This study that showed one-month TB preventive therapy is as effective as longer duration ones, was funded by the National Institutes of Health (NIH) in US, in which over 3000 people (with HIV and no active TB disease) participated in several countries globally (such as India, Thailand, Haiti, Peru, Brazil, and many sub-saharan African nations like South Africa, Botswana, Kenya, Uganda, among others). One group of people in this study, received one-month shorter regimen, and the other group received the standard six-months isoniazid TB preventive therapy. This study also showed that the protective effect of one-month therapy lasted at least for 3 years.
More potent drug is not yet available everywhere: Why?
"Rifapentine which is a more potent drug than rifampin or rifampicin unfortunately is not yet available everywhere. I believe the approval in India is pending as we speak. It is approved in a few countries, but right now it is a lot more expensive than the standard therapy" said Dr Swindells. Dr Ishwar Gilada, who is a member of government of India's Technical Working Group on latent TB infection, informed that very recently 3HP (rifapentine and isoniazid, given once weekly for 3 months) has been approved and will be soon made available in national TB programme.
Dr Swindells called for dual actions for improving access to rifapentine to those in need: 1) lobby with the manufacturer to reduce the cost; and 2) and ideally, getting the generic drug manufacturers in India to make a combination tablet that will be easier for patients.
She said as per current evidence and guidelines, people living with HIV will benefit from TB preventive therapy whether they have latent TB infection or not (with or without test for latent TB).
Dr Srikant Tripathy, Director of National Institute for Research in Tuberculosis (NIRT) of the Indian Council of Medical Research (ICMR) said in ASICON 2019 that there are 3 new studies about to begin on TB preventive therapy in NIRT. One study with The Aurum Institute in South Africa will evaluate if giving 3HP (rifapentine and isoniazid, given once weekly for 3 months) once in a year, and repeating it in the second year, will provide any additional protection. But getting rifapentine was a problem for this study. Second new study on TB preventive therapy at NIRT will evaluate feasibility of introducing 3HP in national TB programme of India (formally called the Revised National TB Control Programme). Third new study on TB preventive therapy at NIRT will assess if we can reduce transmission of TB by providing 3HP to all household contacts regardless of age.
Speaking on side effects of TB preventive therapy (TPT), Dr Susan Swindells shared that "There are two important side effects of TPT: it can cause inflammation of the liver and hepatitis which can be quite severe rarely this is something we need to be watchful about to make sure that people do not get liver inflammation. The other side effect is peripheral neuropathy which effects the nerves mostly of the hands and feet and starts with numbness and tingling before it can progress to a painful condition - if it is not recognized then it could become irreversible. These are the 2 most serious side effects that can happen in a very small number of people who take TPT."
Dr Swindells shares her concern on alarming diabetes rates in several countries including India. Research needs to answer lot more questions on drug-drug interactions and best treatment options for people with multiple conditons such as diabetes, TB, HIV among others.