The US Food and Drug Administration (FDA) on Wednesday approved a new drug for highly drug-resistant tuberculosis, the world's leading infectious cause of death.

Tuberculosis kills 1.6 million people a year, about 500,000 of whom suffer from drug-resistant strains of the disease.

The antibiotic, called pretomanid, was developed by a nonprofit group called TB Alliance at a time when few companies are investing in the expensive and unprofitable endeavor of creating next-generation antibiotics.

Some researchers hope TB Alliance can serve as a model for antibiotic drug development as health authorities warn about the growing danger of drug-resistant infections. The United Nations has projected such infections could cause 10 million deaths each year by 2050 if nothing is done.

"We can have a huge impact on the lives of people who are afflicted and also take a major step ultimately toward, really, the eradication of a disease like TB," said Mel Spigelman, president and chief executive of TB Alliance.

"One definite advantage of a not-for-profit is you don't have to look at things like returning your profits into shareholders."

Drug companies have largely abandoned development of antibiotics because they can cost upward of US$1 billion to bring to market but yield far less revenue than drugs for chronic conditions, such as high blood pressure and high cholesterol, or specialty drugs that can reap hundreds of thousands of dollars or more in revenue per dose.

Antibiotics are often inexpensive and are taken for days or weeks at a time, whereas drugs for cancer and chronic diseases are taken for months or years.

All antibiotics approved in the last decade have had disappointing sales, and Achaogen, a company that had an antibiotic approved last year, filed for bankruptcy in April.

Pretomanid is part of a three-drug regimen against highly resistant forms of TB and is the third FDA-approved anti-TB drug in more than 40 years. TB Alliance said 95 of its first 107 patients in its clinical trial had a successful outcome after six months of treatment with the three-drug regimen. The historical treatment success rate is 34 percent.

Drug-resistant TB is treated with myriad drugs and can require thousands of pills. It has been reported by more than 120 countries, according to the World Health Organization.

Bacterial infections develop resistance to the antibiotics used against them, meaning once-treatable infections, including some forms of tuberculosis, have become extraordinarily difficult to treat. Experts have warned of a looming post-antibiotic era, where many infections may become untreatable.

TB Alliance said it hopes the FDA's approval will enable other countries, such as China, India and South Africa, to okay the drug and to make it available to their residents. The disease is highly contagious and spreads through coughing, sneezing or even talking.

In the New England Journal of Medicine this month, researchers and infectious disease physicians argued the current model for antibiotic development is broken, especially because the few companies that do develop them end up competing with each other to develop drugs for the same infections.

Instead, they propose nonprofit organizations, including TB Alliance, take on a larger role because they do not face pressure from shareholders to develop revenue-generating drugs.

Some experts say governments need to step up and offer more financial incentives for companies. Such efforts by the US government have led to an increase in development - 42 antibiotics were in development in March 2019, compared with six in 2004 - but many of the drugs have been redundant or have not addressed some of the most urgent threats, according to the Pew Charitable Trusts.

"TB is much more narrow and focused and has a precedent in the not-for-profit world," said Helen Boucher, a professor of medicine at Tufts Medical Center and director of the Tufts Center for Integrated Management of Antimicrobial Resistance.

"Economists have told us and others that a nonprofit model would not be adequate to meet the needs for the robust and renewable pipeline we need in America."

The nonprofit model is promising for neglected diseases and those that primarily affect residents in poorer countries, Boucher said.

"There isn't a market to sell [a TB drug] to make money, so it was imperative that a nonprofit take that on," Boucher said. "Any progress is good progress."

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