Inspire fell $4.86 to $3.54 at 10:05 a.m. New York time in Nasdaq Stock Market composite trading. It earlier reached as low as $3.45 for the biggest intraday decline for the Durham, North Carolina-based company since January 2002.

Cystic fibrosis is an inherited disease that leads to buildup of mucus in the lungs and pancreas, causing infections. Patients taking Inspire’s drug, called denufosol, for 48 weeks showed no improvement in a measure of breathing called forced expiratory volume, the company said in a statement. The results contradict a mid-stage study in June 2008 that sparked a single- day gain of 35 percent for Inspire shares.

“Results were both disappointing and unexpected,” said Adrian Adams, chief executive officer of Inspire, in a conference call with investors. “We plan to provide a more detailed corporate update on plans going forward by the middle of February.”

The 466-patient trial also failed to achieve improvement in secondary goals, according to the statement. Analysis of subgroups of patients with varying characteristics failed to identify any population whose symptoms improved after taking the drug.