U.S. health regulators have approved a new Johnson & Johnson drug for patients with tuberculosis who do not respond to other treatments, the company said.

The drug is the first in 40 years to tackle the disease using a new mechanism of action, according to J&J. The drug blocks an energy-producing enzyme that tuberculosis bacteria need to survive.

The U.S. Food and Drug Administration approved the drug, chemically known as bedaquiline and called Sirturo, on Monday following a positive review by an advisory panel last month.

The advisers found the drug to be effective, though they noted that more deaths were seen in the group of patients who took bedaquiline in combination with standard treatments than in the group that took standard drugs alone.

Chrispin Kambili, medical affairs leader for bedaquiline at J&J’s Janssen Therapeutics unit, said in a recent interview that the company is studying the difference in death rates but has so far seen no common pattern.

Almost every death was due to a different cause, including a motor vehicle accident. What was unusual, he said, was the low rate of death in the placebo group.

Advisers to the FDA expressed concern that a greater number of patients had elevated liver enzymes, a potential sign of liver toxicity, and elongated QT levels — an electrical irregularity in the heart that can cause sudden death.

But Kambili said none of the patients died due to serious QT prolongation and there was no unifying findings in the data.

In 2011, nearly 9 million people around the world became sick with tuberculosis, according to the Centers for Disease Control and Prevention, and there were 1.4 million TB-related deaths.

Kambili said J&J’s drug is designed for a relatively small portion of patients – some 650,000 – who do not respond to existing therapies.

And while investment analysts at Cowen and Co have forecast peak annual sales of the product at a relatively modest $300 million, the drug is important from a public health standpoint, Kambili said.

Multidrug-resistant tuberculosis is caused by strains of the bacterium that have become resistant to at least isoniazid and rifampin, the two most potent drugs for TB.

(Reuters)