MediciNova, which is testing MN-221 as a treatment for acute asthma attacks not responsive to standard therapy, said the drug showed no improvement when compared with a placebo.

MN-221 looks to treat the condition by bypassing constricted airways to deliver the drug directly into the lungs. It aims to improve FEV1 ratio when compared with a placebo.

FEV1 ratio measures volume of air exhaled in the first second.

The trial, however, demonstrated a reduction in hospital admissions when MN-221 was added to standard treatments, the company said in a statement.

MediciNova, which said there were three serious adverse events in the trial, plans to continue development of the drug.

Shares in the San Diego, California-based company fell 51 percent to $1.35 in extended trade. They closed at $2.75 on Wednesday on the Nasdaq.

(Reporting by Balaji Sridharan in Bangalore; Editing by Sriraj Kalluvila)

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