(Reuters) – The U.S. Food and Drug Administration on Friday approved Insmed Inc’s lead drug to treat a rare, chronic lung disease, making it the first approved treatment in the United States for the condition.

The drug’s label contains a boxed warning – the FDA’s strictest — of increased risk of respiratory conditions, including inflamed lungs and tightening of the airway, the agency said.

The approval was largely expected after the FDA’s advisory committee backed the drug, Arikayce, in a meeting early last month.

The company said it expects the product to be available in select specialty pharmacies in the coming weeks.

The drug targets adults with treatment-resistant nontuberculous mycobacterial (NTM) lung disease caused by exposure to a specific group of bacteria.

Although the drug’s labeling restricts use to treatment-resistant patients, analysts expect some off-label usage in previously untreated patients and those with other variations of NTM.

“We have spoken to a number of key opinion leaders who have every intention of using it in first-line, if they can get the insurance companies to pay for it,” Cowen analyst Ritu Baral said.

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