Question 1

Why did EXSCEL miss superiority?

Accepted Answer

The primary three-point MACE hazard ratio in EXSCEL was 0.91 with a 95% confidence interval of 0.83 to 1.00 and a P-value of 0.06 for superiority — a near miss rather than a flat result. Several design and population factors contributed. EXSCEL was a pragmatic trial that enrolled both primary- and secondary-prevention patients, with about a quarter of participants having no prior cardiovascular disease at baseline, diluting the absolute event rate. The trial allowed open-label glucose-lowering therapy in both arms, including other GLP-1 receptor agonists and SGLT2 inhibitors, which narrowed the between-arm separation over time. Discontinuation of the assigned trial drug was high in both arms (about 43% on exenatide and 45% on placebo by end of follow-up), reducing the effective on-treatment exposure. Once-weekly extended-release exenatide also has a different pharmacologic profile than liraglutide or semaglutide — a shorter functional half-life, a microsphere depot that produces variable plasma concentrations, and weaker brain penetrance — which most reviewers now believe explains the bulk of the gap rather than trial design alone.

Question 2

Is exenatide still available?

Accepted Answer

Once-weekly extended-release exenatide (Bydureon and Bydureon BCise) was discontinued in the U.S. market by AstraZeneca in 2024. Twice-daily exenatide (Byetta) was discontinued in the U.S. years earlier. Outside the United States, exenatide-containing products remain available in some markets, but the molecule's commercial footprint has been replaced almost entirely by semaglutide, dulaglutide, liraglutide, and tirzepatide. For prescribers in the United States, there is no longer a branded exenatide product on the market, and there is no FDA-approved generic version of either the once-weekly or twice-daily formulation as of 2026.

Question 3

Why was Bydureon discontinued in the U.S.?

Accepted Answer

AstraZeneca cited commercial rather than safety reasons. Bydureon required a complex weekly mixing step with a microsphere suspension that patients found cumbersome compared with the prefilled liquid pens used for semaglutide and dulaglutide. Injection-site nodules — a known consequence of the depot formulation — were a persistent tolerability complaint. Weight loss with Bydureon (approximately 1 to 2 kg in EXSCEL) was modest compared with the 5-10% body-weight reductions clinicians and patients were by then seeing with semaglutide. The EXSCEL near-miss on cardiovascular superiority meant that exenatide could not match the cardioprotective labeling that competing GLP-1 agents had earned. Combined with patent expiry and an unfavorable head-to-head competitive position, the product became uneconomic to keep in the U.S. portfolio, and AstraZeneca announced withdrawal in 2024.

Question 4

How does EXSCEL inform GLP-1 class cardiovascular effects?

Accepted Answer

EXSCEL was the trial that ended the simple class-effect hypothesis for GLP-1 cardiovascular protection. Before EXSCEL reported in September 2017, the two completed superiority trials for the class — LEADER for liraglutide and SUSTAIN-6 for semaglutide — had both been positive, and many commentators expected exenatide to extend the pattern. Its near-miss result, in the largest GLP-1 cardiovascular trial completed at that time, established that cardioprotection is molecule-dependent. The current synthesis, supported by REWIND (dulaglutide, positive), AMPLITUDE-O (efpeglenatide, positive), and HARMONY OUTCOMES (albiglutide, positive), is that the longer-acting human-GLP-1-backbone agents tend to show cardiovascular benefit, while exendin-4-derived agents with shorter functional half-lives (exenatide, lixisenatide) tend not to. This distinction is now built into how the FDA and EMA evaluate cardiovascular labeling claims — each agent must be judged on its own outcomes trial rather than inherited from the class.

Question 5

Should patients on exenatide switch to a different GLP-1 for cardiovascular protection?

Accepted Answer

In the United States this is essentially a historical question because Bydureon and Byetta were both discontinued — patients who were on exenatide have already been transitioned, typically to semaglutide or dulaglutide. From a pure outcomes-evidence standpoint, a patient with type 2 diabetes and established cardiovascular disease is better served by an agent with a positive cardiovascular trial: liraglutide (LEADER), semaglutide (SUSTAIN-6), dulaglutide (REWIND), or efpeglenatide (AMPLITUDE-O), all of which now carry or supported labeled cardiovascular-risk-reduction claims in some form. Tirzepatide (the dual GIP/GLP-1 agonist used in Mounjaro and Zepbound) does not yet have a completed cardiovascular outcomes trial in type 2 diabetes — SURPASS-CVOT is ongoing — but its glycemic and weight-loss effects exceed those seen with any GLP-1 monotherapy. Any switch decision should be made with the prescribing clinician, weighing renal function, cost, coverage, injection burden, and the patient's full cardiovascular risk profile.

Endpoint	Treatment	Comparator	Difference
Cardiovascular death Directionally favorable but did not reach statistical significance and was not protected from multiplicity given the missed primary superiority test.	340 of 7,356 (4.6%)	383 of 7,396 (5.2%)	Hazard ratio 0.88 (95% CI 0.76 to 1.02)
Nonfatal myocardial infarction	354 of 7,356 (4.8%)	383 of 7,396 (5.2%)	Hazard ratio 0.95 (95% CI 0.82 to 1.10)
Nonfatal stroke	187 of 7,356 (2.5%)	218 of 7,396 (2.9%)	Hazard ratio 0.86 (95% CI 0.70 to 1.05)
Death from any cause (all-cause mortality) All-cause mortality crossed the nominal significance threshold, but per the prespecified hierarchical testing plan it was not formally significant because the primary superiority test had failed. Hypothesis-generating only.	507 of 7,356 (6.9%)	584 of 7,396 (7.9%)	Hazard ratio 0.86 (95% CI 0.77 to 0.97)
Hospitalization for heart failure No effect on heart-failure hospitalization, mirroring the broader GLP-1 class pattern and contrasting with the clear heart-failure benefit later seen with SGLT2 inhibitors.	219 of 7,356 (3.0%)	231 of 7,396 (3.1%)	Hazard ratio 0.94 (95% CI 0.78 to 1.13)
Hospitalization for acute coronary syndrome	Reported as supportive endpoint	Reported as supportive endpoint	Hazard ratio 0.97 (95% CI 0.87 to 1.07)
HbA1c change from baseline (least-squares mean difference vs placebo across the trial) Modest glycemic benefit in a real-world background-therapy population; smaller than in head-to-head exenatide vs comparator trials because of more permissive rescue-therapy use in EXSCEL.	Reduced	Reference	Between-group difference −0.53 percentage points (95% CI −0.57 to −0.50)
Body weight change from baseline (least-squares mean difference vs placebo) Weight reduction was clinically modest compared with semaglutide and tirzepatide trials, reflecting both exenatide's lower receptor-activation magnitude and the pragmatic trial design.	Reduced	Reference	Between-group difference −1.27 kg (95% CI −1.40 to −1.13)

Event	Treatment rate	Comparator rate
Injection-site reactions Once-weekly extended-release exenatide uses a microsphere depot formulation that produces visible subcutaneous nodules in a meaningful minority of patients; this was a known class-distinct tolerability issue versus liquid GLP-1 formulations.	Higher with exenatide	Lower with placebo
Confirmed acute pancreatitis No increased pancreatitis signal — consistent with other large GLP-1 CVOTs.	31 of 7,344 (0.4%)	39 of 7,389 (0.5%)
Pancreatic cancer No imbalance; addresses a regulatory concern that had been raised for the GLP-1 class.	20 of 7,344 (0.3%)	24 of 7,389 (0.3%)
Medullary thyroid carcinoma No cases observed in either arm during the trial.	0 of 7,344	0 of 7,389
Severe hypoglycemia Slightly higher with exenatide in absolute terms but not driven by the GLP-1 mechanism itself — concomitant insulin and sulfonylurea use in this pragmatic population was the dominant driver.	247 of 7,344 (3.4%)	219 of 7,389 (3.0%)
Permanent discontinuation of trial drug High discontinuation rates in both arms reflect the pragmatic design and the long follow-up; the gap between arms was small.	43.0%	45.2%

EXSCEL trial deep-dive: exenatide once-weekly CV outcomes in T2D (Holman 2017)

Primary endpoint

Secondary endpoints

Adverse events

Subgroup analyses

Clinical significance

Frequently Asked Questions

References

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