The U.S. Food and Drug Administration on Monday approved a Johnson & Johnson tuberculosis drug that is the first new medicine to fight the deadly infection in more than four decades.

The agency approved J&J's pill, Sirturo, for use with older drugs to fight a hard-to-treat strain of tuberculosis that has not responded to other medications. However, the agency cautioned that the drug carries risks of potentially deadly heart problems and should be prescribed carefully by doctors.

Roughly one-third of the world's population is estimated to be infected with the bacteria causing tuberculosis. The disease is rare in the U.S., but kills about 1.4 million people a year worldwide. Of those, about 150,000 succumb to the increasingly common drug-resistant forms of the disease. About 60 percent of all cases are concentrated in China, India, Russia and Eastern Europe.

In November, the University of Saskatchewan contacted nearly 600 students to be tested for the disease after it was discovered at least one unidentified student had been diagnosed. The Saskatoon health region told CBC News earlier this month that only 244 out of the 589 contacted showed up for testing.

Bacteria more resistant to older drugs

Sirturo, known chemically as bedaquiline, is the first medicine specifically designed for treating multidrug-resistant tuberculosis. That's a form of the disease that cannot be treated with at least two of the four primary antibiotics used for tuberculosis.

The standard drugs used to fight the disease were developed in the 1950s and 1960s.

"The antibiotics used to treat it have been around for at least 40 years and so the bacterium has become more and more resistant to what we have," said Chrispin Kambili, global medical affairs leader for J&J's Janssen division.

'The antibiotics used to treat it have been around for at least 40 years and so the bacterium has become more and more resistant to what we have'—Chrispin Kambili, Johnson & Johnson

The drug carries a boxed warning indicating that it can interfere with the heart's electrical activity, potentially leading to fatal heart rhythms.

"Sirturo provides much needed treatment for patients who have don't have other therapeutic options available," said Edward Cox, director of the FDA's antibacterial drugs office. "However, because the drug also carries some significant risks, doctors should make sure they use it appropriately and only in patients who don't have other treatment options."

Nine patients taking Sirturo died in company testing compared with two patients taking a placebo. Five of the deaths in the Sirturo group seemed to be related to tuberculosis, but no explanation was apparent for the remaining four.

Despite the deaths, the FDA approved the drug under its accelerated approval program, which allows the agency to clear innovative drugs based on promising preliminary results.

Last week, the consumer advocacy group Public Citizen criticized that approach, noting the drug's outstanding safety issues.

"The fact that bedaquiline is part of a new class of drug means that an increased level of scrutiny should be required for its approval," the group states. "But the FDA had not yet answered concerns related to unexplained increases in toxicity and death in patients getting the drug."

The FDA said it approved the drug based on two mid-stage studies enrolling 440 patients taking Sirturo. Both studies were designed to measure how long it takes patients to be free of tuberculosis.

Results from the first trial showed most patients taking Sirturo plus older drugs were cured after 83 days, compared with 125 days for those taking a placebo plus older drugs. The second study showed most Sirturo patients were cured after 57 days.