Aradigm Corp. (NSDQ:ARDM) said today that its inhaled antibiotic failed in a late-stage clinical trial, sending the Hayward, Calif.-based company’s stock down -54% in premarket trading.

Pulmaquin is a once-daily formulation containing ciprofloxacin, a widely prescribed broad-spectrum antibiotic. The inhaled drug was being tested to treat patients with non-cystic fibrosis bronchiectasis (non-CF BE) who have chronic lung infections from the bacteria P. aeruginosa. The infection leads to the enlargement of the lungs’ airways.

The company was evaluating Pulmaquin in 2 late-stage trials: Orbit-3 and Orbit-4. The goal of both trials was to see an increase in the time taken until the 1st instance of pulmonary exacerbation. In Orbit-3, Pulmaquin outperformed the placebo but the difference wasn’t statistically significant. In Orbit-4, however, Pulmaquin did have a statistically significant benefit over the placebo, as patients given Pulmaquin recorded a median time of 230 days until the 1st pulmonary exacerbation, whereas patients given a placebo took 163 days.

While there were 8 deaths in Orbit-3 and 6 in Orbit-4, Aradigm said none of the deaths were related to the inhaled antibiotic.

Pulmaquin, which was awarded orphan drug and fast track status by the FDA, and other inhaled ciprofloxacin formulations are also being evaluated to treat cystic fibrosis and non-tuberculous mycobacteria. The antibiotic is also being looked at as a possible candidate to prevent and treat bioterrorism infections, including inhaled tularemia and pneumonic plague.

ARDM shares were trading at $2.27 in early afternoon activity, down -56.7%.