FDA documents detailing its review of the diabetes drug Bydureon exenatide indicate the agency delayed approval by a year and a half after concluding the drug's sponsor, Amylin Pharmaceuticals Inc., had intentionally and deceptively withheld data from a QT study that agency officials believed raised serious concerns about the product's safety.

According to documents previously made public, and new documents released last week at BioCentury's request, FDA learned about the QT study shortly before it planned to approve Bydureon. The regulators reversed course, holding up approval until the company demonstrated QT safety.