(Adds analysts' comments, shares)
PARIS, Sept 11 (Reuters) - Shares of Regeneron Inc and Sanofi SA slid on Monday after late-stage trial data for their asthma drug, dupilumab, fell short of investor expectations.
The drug, which is approved for atopic dermatitis, met its two main goals in patients with uncontrolled, persistent asthma. But analysts said the data appeared less impressive than the drug's mid-stage data.
At 52 weeks, dupilumab reduced severe asthma attacks by 46 percent in the overall population in the late-stage trial. This is significantly lower than about 71 percent reduction shown in mid-stage data, according to Morgan Stanley analysts.
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.
Last week, AstraZeneca and Amgen reported positive mid-stage data for their asthma drug.
Efficacy of Regeneron's drug in patients with high eosinophils looks competitive, though it appears less effective than AstraZeneca Plc and Amgen Inc's tezepelumab, Cowen & Co said in a note.
The asthma opportunity could be more limited than prior expectations, SunTrust Robinson Humphrey analyst Yatin Suneja said, adding that he expects the drug to be used mainly for patients with higher levels of eosinophils.
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.
Shares of Regeneron were down 4.5 percent to $450.09, while Sanofi's U.S.-listed shares were down about 1 percent at $48.92. (Reporting by Manas Mishra, Sudip Kar-Gupta and Ben Hirschler; Editing by John Stonestreet and Arun Koyyur)