PARIS (Reuters) - Sanofi and Regeneron's biotech drug dupilumab scored a hit in treating severe asthma, clinical trial data showed on Monday, raising competition in an expected multibillion-dollar market.

The companies said the drug - which is already approved under the brand name Dupixent for atopic dermatitis - met its two primary endpoints in a late-stage Phase III clinical study of patients with uncontrolled, persistent asthma.

GlaxoSmithKline's is currently leading the field in the treatment of asthma using injectable antibody drugs but rivals are closing in, with Sanofi and AstraZeneca both seen as strong contenders.

At 52 weeks, dupilumab reduced severe asthma attacks by 46 percent in the overall population. In patients with high levels of so-called eosinophilic cells, reductions were between 60 and 67 percent. The drug also improved lung function.

Sanofi and Regeneron plan to submit an application to use the medicine in severe asthma to the U.S. Food and Drug Administration by the end of this year.

Elias Zerhouni, managing director and president of global research and development at Sanofi, said the results underscored the benefits of focusing on specific molecular pathways behind diseases.

"The positive data from this large second pivotal trial in uncontrolled persistent asthma, following the positive results of dupilumab in atopic dermatitis, further support this view in our opinion," he said.

(Reporting by Sudip Kar-Gupta and Ben Hirschler; Editing by Biju Dwarakanath and John Stonestreet)