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New Weapon in Fight Against Multidrug-Resistant TB
  • Posted March 4, 2020

New Weapon in Fight Against Multidrug-Resistant TB

While the world's focus is trained on the new coronavirus, a groundbreaking clinical trial finds researchers battling a tough-to-treat form of an "old" infectious disease, tuberculosis.

TB is a bacterial infection that usually attacks the lungs. The disease does not get much attention in wealthy nations, where it's less common. The United States saw about 9,000 cases in 2018, according to the U.S. Centers for Disease Control and Prevention.

But worldwide, TB sickens about 10 million people a year and kills roughly 1.5 million. That makes it the leading cause of death from infectious disease -- surpassing HIV/AIDS, according to the World Health Organization (WHO).

The new trial, done in South Africa, offers what experts call a breakthrough in treating particularly deadly cases of TB -- those highly resistant to standard medications.

The researchers found that a three-drug regimen won a "favorable outcome" in 90% of patients. That meant six months after their treatment ended, they had no TB symptoms and tested negative for the bacteria.

Dr. Richard Murphy, a TB researcher not involved in the trial, called the result "extraordinary."

"For people who work in this field, it's surprising how well [the treatment] worked," said Murphy, a spokesperson for the Infectious Diseases Society of America. He is also a researcher with Harbor-UCLA Medical Center and the Lundquist Institute, in Los Angeles.

Dr. Francesca Conradie, the lead researcher on the trial, also used the word "extraordinary."

She said that going into the trial, the researchers had hoped they could achieve a favorable outcome for half the patients.

Instead, "we had nine out of 10 able to go back to their normal lives," said Conradie, of the University of Witwatersrand, in Johannesburg, South Africa.

Of the 10 million people who fall ill with TB each year, most have infections that can be treated with long-used medications. But about 400,000 cases in 2018 were multidrug-resistant, according to the WHO. That means the infections were resistant to at least two standard antibiotics.

A minority of those cases were "extensively drug-resistant" -- failing to respond to all four groups of antibiotics typically used to fight TB.

The current trial involved 38 patients with multidrug-resistant TB and 71 with extensively resistant disease; half also had HIV infection.

Conradie's team treated them with three oral medications -- bedaquiline, linezolid and pretomanid. The first two drugs have been used for a number of years against treatment-resistant TB. Pretomanid is a newer drug developed by the nonprofit TB Alliance, whose researchers worked on the trial.

Study patients took the three pills every day for six months. Six months after the end of that treatment, 98 had a favorable outcome. Of the remaining 11 patients, six died during treatment, and one died from an unknown cause after completing the regimen.

The trial results have already led the U.S. Food and Drug Administration to approve pretomanid, to be used in combination with the other two drugs.

However, there are still unknowns. The trial patients cannot yet be declared "cured," and the researchers continue to follow them. It's also unclear whether the results in these South African patients will generalize to those in other countries. Other studies are ongoing, Conradie said.

Then there are the treatment side effects. Some of the most common were nausea, headache, anemia and vision problems. But 81% of patients had peripheral neuropathy -- nerve damage that, Murphy said, may or may not go away.

The study results were published in the March 5 issue of the New England Journal of Medicine.

The WHO has set a goal of a TB-free world by 2035. To achieve that, it will take more than new drugs for resistant TB, experts say.

"The main reason TB remains a major public health problem is that we don't do a good job of treating old-fashioned, drug-sensitive cases," Murphy said.

Getting the medications to people in need -- and ensuring that they adhere to them for months, even in the face of side effects -- is no small task.

There is a major need for funding of "implementation research" -- the type that focuses on translating treatments that work well in clinical trials into the real world, Murphy said.

In October, the Global Drug Facility, a worldwide provider of TB drugs, announced a price of $364 for a full course of pretomanid. The full three-drug regimen costs just over $1,000 -- a price that some groups, like the nonprofit Doctors Without Borders, have criticized as too high.

More information

The World Health Organization has an overview on tuberculosis.

SOURCES: Francesca Conradie, M.B.B.Ch., researcher, University of Witwatersrand, Johannesburg, South Africa; Richard Murphy, M.D., M.P.H., attending physician, infectious diseases, Harbor-UCLA Medical Center, and investigator, Lundquist Institute, Los Angeles, and spokesperson, Infectious Diseases Society of America, Arlington, Va.; March 5, 2020, New England Journal of Medicine
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