A new combination drug treatment has had amazing success in treating extensively drug-resistant tuberculosis (XDR-TB). The rare but serious form of the disease kills more than 70% of the patients it infects.
“XDR-TB cannot be treated with the conventional drugs”
As many countries lack the capacity to accurately diagnose XDR-TB, the full-scale of the disease is unknown. 49 countries have had confirmed cases of XDR-TB, with an estimated 40,000 cases per year worldwide. Treatment misuse and transmission among vulnerable populations such as migrant workers, refugees or HIV-positive people mean that the disease prevalence is expected to increase.
XDR-TB cannot be treated with the conventional drugs used to treat non-resistant TB. Alternative XDR-TB treatments take up to 2.5 years to take effect, have low efficacy and often have toxic side effects.
“All 34 patients were declared ‘infection-free’ after the 6 month trial”
The restricted treatment options have raised concerns of a future TB epidemic, fears temporarily put on hold by this latest breakthrough.
The unique combination treatment was trialled on 34 South Africans diagnosed with XDR-TB, with half also diagnosed with HIV. TB is a leading killer of HIV-positive people, with 35% of HIV deaths caused by TB in 2015.
All 34 patients were declared ‘infection-free’ after the 6 month trial. Three antibiotics (bedaquiline, pretomanid and linezolid) were used to treat the XDR-TB-positive patients in the treatment named ‘Nix-TB’.
Bedaquiline is a medication currently used to treat TB but has not been widely used. Pretomanid is also a TB-specific drug but is still experimental. Linezolid is mainly used for skin infections and pneumonia but has been shown to have efficacy in treating a range of infections caused by antibiotic-resistant bacteria such as XDR-TB. All three can be taken in pill form in a simple treatment regime.
After the six-month trial TB bacillus could not be cultured from any of the 34 patients’ sputum, a sign that the infection had been totally cleared. 20 of the patients could entirely stop taking the drugs. Just a single patient relapsed into XDR-TB and had to return to the treatment, an impressive and unprecedented result.
The effectiveness of the novel multi-drug treatment on a large-scale drug-resistant disease could prove promising for other multi-drug resistant diseases such as MRSA. The repurposing of approved drugs such as bedaquiline with no or minimal previous use reduces the risk of drug resistance and avoids potential toxic side effects.
“and save millions of lives every single year.”
Due to the high co-infection rate of HIV and XDR-TB, future studies must pay particular attention to the interactions between the antiretroviral drugs prescribed for HIV and the new Nix-TB combination.
It is unclear how quickly the treatment will be able to have widespread use as pretomanid is currently awaiting regulatory approval. It is possible that Nix-TB could be approved as a distinct treatment. If so, it is likely that the amazing results seen in the South African trial would be replicated across larger studies.
This could be the beginning of a very exciting age of combination treatments curing drug resistant diseases and save millions of lives every single year.