Mortality Reduction in EMPA-REG OUTCOME Trial: Beyond the Antidiabetes Effect

Two recent large-scale cardiovascular outcome trials, a now common tool in assessing the safety of pharmacological treatments for type 2 diabetes, reported significant reductions in all-cause mortality. In EMPA-REG OUTCOME [BI 10773 (Empagliflozin) Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients], patients who received the SGLT2 inhibitor empagliflozin had a notable reduction of 9.2 deaths per 1,000 per year, while LEADER (Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Resultsd-A Long Term Evaluation) found that the patients receiving the GLP-1 receptor agonist liraglutide had a reduction of 3.7 deaths per 1,000 per year. The hypotheses to explain the sizable mortality reduction in EMPA-REG OUTCOME have mainly focused on the potential cardiovascular mechanisms of empagliflozin, but none considered its expected antidiabetes effects. I estimated the portion of the reduction in mortality observed in EMPA-REG OUTCOME expected to be a result of its antidiabetes effects, as measured by glycemic control and the need for additional antidiabetes medication, and contrasted it with LEADER. With use of themean 0.45% reduction in HbA1c with empagliflozin compared with placebo in EMPA-REG OUTCOME, the rate reduction of 9.2 deaths per 1,000 per year would be expected to be at most 4.5 deaths per 1,000 per year, leaving 4.7 deaths per 1,000 per year otherwise explained. On the other hand, LEADER's rate reduction of 3.7 deaths per 1,000 per year with liraglutide would be expected to be 3.5 by virtue of its effect on HbA1c, leaving 0.2 deaths per 1,000 per year explained otherwise. Similar results were found using the need for additional antidiabetes treatment during follow-up tomeasure the antidiabetes impact. In conclusion, the expected antidiabetes effects of empagliflozin and liraglutide on the reduction in mortality are important. However, empagliflozin appears to have significant additional effects on survival, possibly due to specific cardiovascular mechanisms, which merit further investigation.