GlaxoSmithKline Plc’s new respiratory treatment for chronic breathing problems is under review to determine the safety of increasing its use to treat asthma patients, according to Reuters.

The U.S. Food and Drug Administration says they are reviewing the treatment and discussing whether the combination treatment, Breo Ellipta, should be approved to treat asthma.

The inhaled drug combination of vilanterol and corticosteroid is already approved to treat chronic obstructive pulmonary disease, a breathing disability that gets worse over time and usually only affects smokers.

Vilanterol is in a class of long-acting beta-adrenoceptor agonists (LABA) that have historically been linked to asthma-related deaths. Corticosteroids smooth the inner surface of breathing pathways.

The data shows that Breo Ellipta’s LABA component can delay the worsening of asthma symptoms. This information is what could sway the FDA panel in its favor.

But observations after a preliminary review only looked at data from clinical studies conducted by GSK, according to its report. They also said that the benefit of adding a LABA compound to a steroid was not demonstrated consistently in the trials.

But the FDA did find that the medication did not cause any asthma-related fatalities in a series of clinical studies conducted by the drugmaker that the FDA reviewed.

Glaxo already has three respiratory treatments on the market with a LABA compound. Each of these carry a warning that the drug could possibly increase the risk of asthma-related deaths.

This possible side-effect was verified in a study that tested another one of Glaxo’s LABA compounds, salmeterol, against a placebo.