NEW YORK (AP) — Shares of Savient Pharmaceuticals Inc. tumbled Monday after the FDA declined to approve its chronic gout treatment Krystexxa at this time, saying the company must tighten its manufacturing procedures and update safety data, among other items, before the agency can further review of the drug. Shares fell $5.89, or 38 percent, to $9.70 in premarket trading. Krystexxa, the proposed brand name of the drug pegloticase, is an enzyme intended to treat chronic gout in patients for whom other treatments have failed. Gout, a very painful form of arthritis, is caused by excess uric acid crystallizing and collecting around joints and tendons, causing debilitating inflammation. Savient said Sunday it will immediately request a meeting with the FDA to discuss the agency’s concerns and believes it can resubmit its application by early next year. In a letter, the FDA cited deficiencies with the chemistry, manufacturing and controls section of the company’s application. One issue addressed a change made by Savient in the proposed process for making Krystexxa. The FDA said comparability data submitted didn’t adequately show that the drug manufactured under the altered process was equivalent to the drug used in late-stage studies which established its safety and effectiveness. The FDA has given the company the option of reverting to and validating the manufacturing process used to produce the Krystexxa used in the Phase 3 trials, or conducting new clinical trials with the drug made with the altered process. Savient said it expects to revert to the original process. Savient said the agency also said the drug’s approval would require the company to compile a medication guide to ensure the safe and effective use of Krystexxa by patients, and devise a plan to make sure health care providers prescribing the drug would disclose the risks of severe infusion reactions and possible anaphylaxis, or severe allergic shock, as well as other severe adverse reactions in patients with other medical conditions. The FDA will require Savient’s resubmitted application to include an update of safety data from all ongoing studies. Additionally, a satisfactory inspection report showing that Savient’s manufacturer, BTG-Israel, has addressed certain FDA concerns is required. “While our timeline for resubmission to the FDA is subject to a number of uncertainties, we currently believe that we can target completion of our resubmission for early 2010. We hope to have more clarity on the expected timeline after we meet with the FDA to discuss the complete response letter,” said Paul Hamelin, president of Savient, in a statement. The FDA’s action comes even after a panel of experts in June recommended the drug’s approval. The FDA normally follows the opinions of its advisers, though that is not a requirement. Savient shares had been rising as some analysts considered the company a potential buyout target because of Krystexxa’s potential.