Documents recently posted to the FDA’s website say pharmaceutical company, Amylin, has not been completely forthcoming about its diabetes drug, Byetta, and related drug Bydureon, concerning their potential for cardiovascular complications.

The active ingredient is the same in the two drugs which are both used to treat type 2 diabetes. However, Bydureon is administered just once a week rather than twice a day, which is thought to make it more attractive and convenient to users.

Amylin asked the FDA to review the Byetta data as part of the Bydureon approval process. The FDA agreed but Amylin failed to tell the FDA of a safety study about Byetta and then delayed the review process. The study in question, the QT study, done for Canadian regulators, measured the heart rhythm cycles of patients on Byetta.

But Canadian regulators spilled the beans to the FDA that Amylin had not included the QT study of Byetta in the FDA inquiry which raised some red flags about the safety of Byetta on the heart.

When FDA regulators asked for the internal data, Amylin submitted other documents and stalled. After a first denial, Amylin submitted Bydureon for approval again. The agency rejected the drug a second time on October 18, 2010, because of the Canadian heart safety concerns.

The company submitted the drug for another review in 2011, and was approved for sale in January of 2012, but questions still remain as to why documents were withheld in the first place.

The timing is interesting in that during the stalled approval process, Amylin was being courted by several takeover companies. Late Friday, June 29, Bristol-Myers Squibb announced it was buying the pharmaceutical company and paying off some debt to Eli Lilly & Co for a reported deal worth $7 billion.