Shares of Discovery Laboratories Inc. fell to their lowest point in a decade today after the company said a Food and Drug Administration review standard places in doubt the approval of Surfaxin, a respiratory treatment for premature infants.

The stock plunged 54 cents, or 51.43 percent, to reach 51 cents in afternoon trading, but earlier fell as low as 46 cents, marking a 10-year low point.

Late Wednesday, the Warrington-based company said the respiratory drug candidate Surfaxin would likely face a difficult obstacle with the FDA after the agency said it would use a new standard to review the drug application. Discovery Laboratories is still deciding its next move, but said current data in the drug application would likely not meet the FDA's new standard.

The company has been trying to gain approval for Surfaxin, aimed at treating respiratory distress syndrome in infants.

Surfaxin is a synthetic lung substance for premature babies who are born with insufficient natural surfactant in their lungs and are prone to life-threatening diseases. Surfactant is a critical substance that helps breathing and prevents tiny air sacs in the lungs from collapsing. Treatments for the disorder are limited.

The FDA has made several requests for more information, with the last focused on the test used to determine the drug's shelf-life and whether the commercial product would be comparable to the product used in the studies.

Discovery Laboratories said it would shift focus and resources to aerosolized treatments for respiratory distress syndrome.

Wedbush Morgan analyst Kimberly Lee downgraded shares to "sell" from "hold," and said the Surfaxin respiratory distress syndrome is "dead."

"As we anticipated, issues in the Complete Response Letter [FDA request] were not able to be fully addressed at the end-of-review meeting with the FDA on June 2," she said, in a note to investors.

Funding remains an issue for the company, she added, adding that she expects management to explore potential partnerships or alliances to stay afloat.

"In addition, we view the remaining pipeline as early stage with inherent significant development risks," she said.