EMPA-REG OUTCOME

After 2008, cardiovascular outcome trials of new diabetes drugs were designed mainly to show that the drugs did not raise cardiovascular risk. The 2008 FDA guidance requiring cardiovascular safety data for all new diabetes agents grew directly from the rosiglitazone episode, in which a widely used drug appeared to increase myocardial infarction risk. Drug makers responded by running large cardiovascular outcome trials, most of which showed neutral results. A neutral result for empagliflozin would have fit that pattern.

EMPA-REG OUTCOME enrolled 7,020 adults with type 2 diabetes and established cardiovascular disease across 42 countries, randomizing them to empagliflozin (10 mg or 25 mg) or placebo added to standard care. The primary composite endpoint was cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. Bernard Zinman of Mount Sinai Hospital in Toronto presented the results at the European Association for the Study of Diabetes meeting in Stockholm in September 2015, after a median observation time of 3.1 years. Empagliflozin cut the primary endpoint by 14%, cardiovascular mortality by 38%, and all-cause mortality by 32%; hospitalization for heart failure fell by 35%.

The magnitude of the mortality reduction surprised the field, partly because the HbA1c difference between the groups was modest. That mismatch suggested the benefit was not primarily glycemic. Debate over mechanism centered on the drug's osmotic diuretic effect, reduction in arterial stiffness, ketone body metabolism, and direct cardiac and renal effects. The renal analysis published in 2016, showing a 39% lower risk of new or worsening nephropathy (12.7% vs 18.8%), reinforced the view that SGLT2 inhibition was acting on hemodynamic and metabolic pathways beyond glucose disposal.

Rates of myocardial infarction and stroke did not differ significantly between the groups, which pointed away from slowed atherosclerosis and toward a hemodynamic or metabolic mechanism. Silvio Inzucchi was the report's senior author. Peer response ranged from enthusiasm to skepticism about whether the results could be generalized to lower-risk patients not yet carrying cardiovascular disease.

The clinical consequences arrived quickly. In the following years, SGLT2 inhibitors entered diabetes, cardiology and nephrology guidelines as preferred agents for patients with heart failure, chronic kidney disease, or established cardiovascular disease. Subsequent trials, CREDENCE for canagliflozin and DAPA-HF and DAPA-CKD for dapagliflozin, confirmed organ protection across the class, extending indications to patients without diabetes entirely. The SGLT2 inhibitor class is now listed in heart failure guidelines at the same level of evidence as beta-blockers and renin-angiotensin system agents.