In 2008, the FDA suggested that drug companies should assess the cardiovascular hazards of Type 2 diabetes medications more thoroughly during development. AstraZeneca attempted to include a statement in Onglyza's prescribing information that saxagliptin could be related to a diminished risk of cardiovascular events, but the FDA declined this due to a lack of clinical evidence.
This same lack of data caused the FDA to demand additional post-approval testing of Onglyza, which was followed up with a New England Journal of Medicine (NEJM) study in 2012 that showed a heightened danger of heart failure in Onglyza users. Pre- and post-market testing of Onglyza demonstrate significant disparities. For instance, clinical trials had a median of 62 weeks (1.19 years) of testing, while the post-marketing study had patients for a median of 2.1 years. Instead of conducting more thorough testing of Onglyza prior to FDA approval, AstraZeneca waited until after the drug was authorized. As a result, thousands of patients may have been exposed to increased risks of heart failure and death and potentially other serious Onglyza side effects.