The LEADER Trial: Liraglutide and Cardiovascular Outcomes in T2DM

The regulatory environment that created LEADER

After the FDA's 2008 guidance requiring dedicated cardiovascular outcomes trials for all new diabetes drugs, every manufacturer seeking a new T2DM approval had to demonstrate that their drug did not increase cardiovascular risk. Liraglutide (Victoza) had already been approved in the United States and European Union on the strength of glucose-lowering data, but the cardiovascular question required a post-approval study.

LEADER (Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Results, NCT01179048) was Novo Nordisk's answer. What made LEADER exceptional was not just that it satisfied the non-inferiority requirement; it crossed the superiority boundary, demonstrating that liraglutide actually reduced the rate of major adverse cardiovascular events in a high-risk population. It became the first GLP-1 receptor agonist to achieve this distinction, ahead of the SUSTAIN-6 result for semaglutide published in the same issue of the New England Journal of Medicine in September 2016.

Trial design

LEADER enrolled 9,340 adults with type 2 diabetes across 32 countries. Eligibility required either established cardiovascular disease (prior MI, stroke, revascularization, heart failure, or peripheral vascular disease) or multiple cardiovascular risk factors in adults aged 60 or older. This design intentionally enriched the trial for CV events, enabling a reasonably short event-driven study.^[1]

Participants were randomized 1:1 to liraglutide 1.8 mg subcutaneous once daily (dose-escalated from 0.6 mg) or matching placebo, added to usual standard-of-care diabetes and cardiovascular management. The primary endpoint was time to first occurrence of three-component MACE (cardiovascular death, non-fatal MI, or non-fatal stroke). The minimum follow-up was 3.5 years; median follow-up was approximately 3.8 years.

Primary and key secondary results

The primary MACE endpoint occurred in 13.0% of liraglutide-treated patients versus 14.9% of placebo-treated patients; hazard ratio 0.87 (95% CI 0.78 to 0.97, p < 0.001 for non-inferiority, p = 0.01 for superiority).^[1]This 13% relative risk reduction translated to an absolute risk reduction of approximately 1.9 percentage points over median 3.8 years.

Breaking down the composite by component:

• Cardiovascular death: HR 0.78 (95% CI 0.66 to 0.93); statistically significant and the primary driver of the composite benefit.
• Non-fatal myocardial infarction: HR 0.88 (95% CI 0.75 to 1.03); directionally favorable, not individually significant.
• Non-fatal stroke: HR 1.11 (95% CI 0.88 to 1.39); directionally unfavorable though not significant, a pattern opposite to what SUSTAIN-6 and SELECT would later show for semaglutide.

A pre-specified secondary endpoint of nephropathy (new or worsening kidney disease) also favored liraglutide, with a hazard ratio of 0.78 (95% CI 0.67 to 0.92), reported in a separate sub-study publication.^[2] This renal signal added to the clinical argument for using liraglutide in patients with early diabetic nephropathy and preceded the dedicated renal outcomes data later generated for semaglutide (FLOW).

Glycemic and weight effects in context

Over the course of LEADER, liraglutide produced a mean HbA1c reduction of approximately 0.4 percentage points greater than placebo at 36 months, with liraglutide-treated participants maintaining a mean HbA1c approximately 0.4 points lower than the placebo group. Body weight fell by approximately 2.3 kg more in the liraglutide group. Blood pressure was modestly lower as well.

These intermediate improvements are consistent with the general pharmacology of GLP-1 receptor agonists but are modest compared with the glycemic and weight effects seen in trials specifically designed to test glycemic efficacy at maximum dose (such as the SUSTAIN program). The cardiovascular benefit in LEADER must be interpreted in the context of background standard-of-care treatment that already included statins, antihypertensives, and antiplatelet therapy.

Legacy within the GLP-1 class

LEADER set a benchmark. By demonstrating that a GLP-1 receptor agonist could reduce cardiovascular death in diabetic patients already on optimal medical therapy, it reframed the clinical case for the entire class. Subsequent CVOT programs had to be compared against LEADER's template: SUSTAIN-6 (semaglutide) showed a larger relative stroke reduction; PIONEER-6 (oral semaglutide) achieved non-inferiority but not superiority; SELECT (semaglutide 2.4 mg in non-diabetics) demonstrated MACE reduction in obesity without diabetes.

LEADER also provided the first large-scale evidence for a renal benefit with a GLP-1 agonist, establishing a research thread that culminated in the FLOW trial (semaglutide in CKD) reporting in 2024.

The FDA label update for Victoza in August 2017 was the first time a GLP-1 receptor agonist received an explicit cardiovascular risk-reduction indication in the United States. That addition changed prescribing dynamics in patients with T2DM and established CVD, making liraglutide the preferred GLP-1 option in cardiology-influenced treatment guidelines until semaglutide's own CV label was approved.

Safety signals from LEADER

The most consequential safety question heading into LEADER was pancreatitis. Earlier observational data had raised concern that GLP-1-based therapies might increase pancreatic inflammation. LEADER found no statistically significant increase in pancreatitis events with liraglutide versus placebo; rates were low and numerically similar in both arms. The same absence of a signal had been observed in ELIXA (lixisenatide) and was subsequently confirmed in SUSTAIN-6 and EXSCEL (exenatide ER).

Gallbladder-related events (cholelithiasis and cholecystitis) were slightly more common with liraglutide, consistent with the general GLP-1 class effect of slowing gallbladder motility. Heart rate was modestly elevated with liraglutide (approximately 3 bpm), a finding common across GLP-1 receptor agonists whose clinical significance in populations with established heart disease requires monitoring. No excess of heart failure was observed.