WARRINGTON, Pa. (AP) — Discovery Laboratories Inc. said Monday the Food and Drug Administration again requested more information on the company's quality control data for the respiratory drug candidate Surfaxin. The agency has already asked the company once for more information in the regulatory application and Discovery Laboratories has responded. The latest letter focuses 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. Shares of Discovery Laboratories plunged $1.05, or 58 percent, to 75 cents in premarket trading. The stock closed at $1.80 during the regular session Friday. Surfaxin is being developed specifically as a treatment for respiratory distress syndrome in infants. "Discovery Labs believes that data already submitted to the FDA support the comparability of Surfaxin clinical drug product to commercial Surfaxin drug product," the company said in a statement. Discovery Laboratories has been seeking FDA approval of the drug for more than two years. It anticipates approval in 2009. Meanwhile, the company said it is taking measures to conserve cash and exploring "strategic" alternatives. The latter measure could include more financing and partnerships, according to the company.