Pfizer ( PFE) said Friday that the Food and Drug Administration will need an extra three months to review its application for the inhaled insulin Exubera. No explanation was given by Pfizer or its marketing partner Sanofi-Aventis ( SNY). The agency needs more time to review "additional technical chemistry data" from the companies. Pfizer and Sanofi-Aventis said they will "continue to work closely with the FDA so that this important medicine can be made available for patients." Exubera is one of several inhaled insulin products in development, and it's far ahead of competitors in the regulatory review process. The FDA had been expected to act today. Shares of both companies weren't affected. Pfizer's stock was up 16 cents to $21.26, while Sanofi-Aventis' stock was up 1 cent to $39.54. However, shares of Nektar Therapeutics ( NKTR), the company that developed the inhalation technology, dropped 45 cents, or 3.1%, to $14.31 in heavy trading. The stock dipped as low as $13.63. "This appears to be a minor delay, with approval likely delayed to the end of January 2006," according to a research note from Sagient Research Systems of San Diego, whose BioMedTracker report analyzes biotechnology issues. "We continue to believe that the FDA will accept the advisory committee recommendations to approve Exubera for patients without underlying lung abnormalities." Last month, an FDA advisory committee recommended approval of Exubera for treating adults with type 1 and type 2 diabetes. Type 1 diabetes is caused by the body's inability to produce insulin, the protein hormone that helps turn sugar into fuel for the body's cells. Type 2 diabetes, which is much more common, is caused by cells ignoring insulin or the body's failure to produce enough insulin. The advisory panel vote was 7-2. Although the FDA isn't bound by panels' recommendations, it usually follows their advice.