(Reuters) -The U.S. Food and Drug Administration has approved British drugmaker GSK's asthma drug to treat some patients with a chronic lung disease commonly known as "smoker's lung", the company said on Thursday.

The approval expands the use of the drug, Nucala, as an add-on treatment for patients with a type of chronic obstructive pulmonary disease.

Sanofi and Regeneron's blockbuster drug Dupixent and Verona Pharma's inhaled therapy Ohtuvayre are also approved for the condition, which affects the lungs, causing restricted airflow and breathing problems.

GSK's Nucala is a monoclonal antibody that inhibits interleukin-5, which helps regulate eosinophils, a type of white blood cell that causes inflammation in the lungs when overproduced.

The regulator had set a target action date of May 7 for its decision on the drug. The approval, however, came two weeks later.

This is the latest instance where the drug regulator has missed its deadline after mass layoffs as part of a major overhaul of federal health agencies under Secretary of Health and Human Services Robert F. Kennedy Jr.

The approval was based on a late-stage trial, in which patients treated with Nucala and an inhaled maintenance therapy for up to 104 weeks had significantly reduced exacerbations by 21% compared to placebo.

"There's a very high burden when you have severe exacerbations and end up being hospitalized. The aim is to keep patients out of the hospital, keep them stable, and keep them at home," GSK's Chief Commercial Officer Luke Miels said ahead of the approval.

Nucala recorded 1.78 billion pounds ($2.38 billion) in total sales last year.

The disease commonly affects cigarette smokers but can also be caused by air pollution and related occupational hazards. It is the fourth leading cause of death worldwide, according to the World Health Organization.