The Shifting Paradigm in Diabetic Cardiometabolic Care
The management of type 2 diabetes (T2D) has undergone a profound transformation over the last decade, transitioning from a glucocentric approach to a multifaceted strategy that prioritizes organ protection, particularly for the heart and kidneys. The emergence of glucagon-like peptide-1 (GLP-1) receptor agonists has been central to this shift, with multiple trials demonstrating significant reductions in major adverse cardiovascular events (MACE). However, the introduction of tirzepatide—a first-in-class dual agonist of both the GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptors—has raised new questions regarding whether dual agonism offers superior cardiovascular protection compared to selective GLP-1 receptor agonism.
The Mechanistic Rationale for Dual Agonism
Tirzepatide’s unique pharmacology combines the well-established benefits of GLP-1 receptor activation—such as enhanced glucose-dependent insulin secretion, slowed gastric emptying, and appetite suppression—with the metabolic actions of GIP. While GIP was historically thought to be less relevant in T2D due to a diminished insulinotropic effect, research has shown that when combined with GLP-1 agonism, it may synergistically improve lipid metabolism, reduce systemic inflammation, and enhance adipose tissue insulin sensitivity. These pleiotropic effects suggest a potentially more robust impact on atherosclerotic pathways than GLP-1 agonism alone.
SURPASS-CVOT: Study Design and Methodology
The SURPASS-CVOT trial (NCT04255433) was a landmark, active-comparator-controlled, double-blind, noninferiority trial. Unlike previous CVOTs that compared new agents to a placebo, SURPASS-CVOT utilized dulaglutide (1.5 mg weekly) as the comparator. Dulaglutide is an established GLP-1 receptor agonist with proven cardiovascular benefits, as demonstrated in the REWIND trial. This choice of an active comparator set a high bar for tirzepatide, aiming to determine if the dual agonist could match or exceed the standard of care for cardiovascular risk reduction.
The trial enrolled 13,299 patients with T2D and established atherosclerotic cardiovascular disease (ASCVD). Participants were randomized 1:1 to receive either a weekly subcutaneous injection of tirzepatide (escalated to a maintenance dose of up to 15 mg) or dulaglutide (1.5 mg). The primary end point was a composite of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke (3-point MACE). The noninferiority margin was set at 1.05 for the upper limit of the 95.3% confidence interval for the hazard ratio.
Patient Population and Baseline Characteristics
The study population reflected a high-risk clinical cohort. The mean age was 64.1 years, and the mean duration of diabetes was nearly 15 years, indicating a population with significant disease progression. Approximately 29% of participants were women, and the mean BMI was 32.6, categorized as obese. Baseline glycated hemoglobin (HbA1c) was 8.4%, and all patients had documented ASCVD, ensuring that the trial adequately tested the drugs’ effects on secondary cardiovascular prevention.
Primary and Secondary Outcomes
The results of the modified intention-to-treat population, which included 13,165 patients, provided clear evidence of cardiovascular safety. A primary end-point event occurred in 801 patients (12.2%) in the tirzepatide group and 862 patients (13.1%) in the dulaglutide group. The resulting hazard ratio (HR) was 0.92, with a 95.3% confidence interval of 0.83 to 1.01.
Statistical Significance and Interpretation
With the upper limit of the confidence interval (1.01) falling well below the pre-specified margin of 1.05, tirzepatide successfully met the primary objective of noninferiority (P = 0.003). However, when tested for superiority, the p-value was 0.09, meaning that while there was a numerical trend favoring tirzepatide, it did not reach the threshold for statistical significance over dulaglutide. This suggests that in the context of cardiovascular protection, tirzepatide is at least as effective as one of the most potent GLP-1 receptor agonists currently in use.
Metabolic Gains and Clinical Observations
While the primary focus was cardiovascular outcomes, the metabolic data from SURPASS-CVOT reinforced findings from earlier SURPASS trials. Tirzepatide demonstrated robust efficacy in lowering HbA1c and promoting weight loss. Although the 1.5 mg dose of dulaglutide is effective, the dual agonism of tirzepatide typically results in more substantial reductions in body mass, which may provide long-term benefits for heart failure and other weight-related comorbidities not fully captured by the 3-point MACE endpoint.
Safety and Tolerability Profile
The safety profile was largely consistent with the known effects of incretin-based therapies. Both groups experienced similar rates of serious adverse events. However, gastrointestinal (GI) side effects, including nausea, vomiting, and diarrhea, were reported more frequently in the tirzepatide group, particularly during the dose-escalation phase. These events were mostly mild to moderate but are a key consideration for clinicians when initiating therapy and Titrating doses to the 15 mg maximum.
Expert Commentary and Clinical Implications
The SURPASS-CVOT trial is a significant addition to the medical literature because it validates the cardiovascular safety of GIP/GLP-1 dual agonism against a high-performing active comparator. For clinicians, this means that the impressive glucose-lowering and weight-loss capabilities of tirzepatide do not come at the expense of cardiovascular safety; rather, it provides a level of protection comparable to established GLP-1 RAs.
Some experts note that the 1.5 mg dose of dulaglutide, while the dose used in the REWIND trial, is now lower than the 3.0 mg and 4.5 mg doses often used in clinical practice for glycemic control. However, for the purpose of a CVOT, the 1.5 mg dose remains the evidence-based standard for cardioprotection. The fact that tirzepatide trended toward superiority (HR 0.92) suggests that with longer follow-up or in different populations, a distinct advantage might emerge.
Conclusion
In patients with type 2 diabetes and established atherosclerotic cardiovascular disease, tirzepatide is noninferior to dulaglutide regarding the risk of major adverse cardiovascular events. These findings support the use of tirzepatide as a potent tool in the cardiometabolic armamentarium, offering significant glycemic and weight benefits alongside proven cardiovascular safety. As we move forward, the results of this trial will likely influence clinical guidelines, positioning dual agonists as a preferred option for high-risk patients who require intensive metabolic management.
Funding and ClinicalTrials.gov
The SURPASS-CVOT trial was funded by Eli Lilly and Company. ClinicalTrials.gov number: NCT04255433.
References
1. Nicholls SJ, et al. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes. N Engl J Med. 2025 Dec 18;393(24):2409-2420. doi: 10.1056/NEJMoa2505928.
2. Gerstein HC, et al. Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND): a double-blind, randomised placebo-controlled trial. Lancet. 2019;394(10193):121-130.
3. Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216.
