Trial review
SUMMIT Trial: Tirzepatide and HFpEF
Tirzepatide in heart failure with preserved ejection fraction and obesity
SUMMIT was a phase 3, randomised, double-blind, parallel-group, placebo-controlled, multicentre funded by Eli Lilly and Company. A 38% reduction in the combined endpoint of cardiovascular death and worsening heart-failure events, with improvement in symptoms, physical limitations and exercise capacity.
| Design | Phase 3, randomised, double-blind, parallel-group, placebo-controlled, multicentre |
|---|---|
| Population | Adults with heart failure with preserved ejection fraction and obesity (BMI 30 or above), with or without type 2 diabetes |
| Sample size | 731 randomised 1:1 |
| Intervention | Tirzepatide once weekly at maximum tolerated dose |
| Comparator | Placebo |
| Duration | 52 weeks to the symptom endpoint, with event follow-up |
| Primary endpoint | Co-primary: time to first occurrence of a heart-failure outcome, and change in heart-failure symptoms and physical limitations at 52 weeks |
| Main result | A 38% reduction in the combined endpoint of cardiovascular death and worsening heart-failure events, with improvement in symptoms, physical limitations and exercise capacity |
Show this figure as a table
| Step | Stage | What happens |
|---|---|---|
| 1 | Who was eligible | Adults with heart failure with preserved ejection fraction and obesity (BMI 30 or above), with or without type 2 diabetes |
| 2 | What they received | Tirzepatide once weekly at maximum tolerated dose |
| 3 | What it was compared against | Placebo |
| 4 | For how long | 52 weeks to the symptom endpoint, with event follow-up |
| 5 | What was measured first | Co-primary: time to first occurrence of a heart-failure outcome, and change in heart-failure symptoms and physical limitations at 52 weeks |
| 6 | What the group average was | A 38% reduction in the combined endpoint of cardiovascular death and worsening heart-failure events, with improvement in symptoms, physical limitations and exercise capacity |
| 7 | What it does not tell you | A group average is not a prediction for any individual reader. |
Show this figure as a table
| Item | Weight change | Evidence |
|---|---|---|
| Intervention group | not captured | — |
| Comparator group | not captured | — |
| Question | Position |
|---|---|
| Average effect in the studied population | Reported once captured |
| Your individual outcome | Not predicted by any trial |
| Effect of a compounded preparation | Not studied here |
| Effect at doses outside the protocol | Not studied here |
| Effect after stopping | Only if the trial included a withdrawal phase |
| Long-term safety beyond the trial | Outside the observation window |
Who was studied?
Adults with heart failure with preserved ejection fraction and obesity (BMI 30 or above), with or without type 2 diabetes
Registry and publication identifiers: NCT04847557. Sponsor: Eli Lilly and Company. Checked against the source on 2026-08-03.
What was given, and what was it compared against?
| Field | What the record states |
|---|---|
| Design | Phase 3, randomised, double-blind, parallel-group, placebo-controlled, multicentre |
| Intervention | Tirzepatide once weekly at maximum tolerated dose |
| Dose | 5 mg, 10 mg or 15 mg |
| Comparator | Placebo |
| Duration | 52 weeks to the symptom endpoint, with event follow-up |
| Primary endpoint | Co-primary: time to first occurrence of a heart-failure outcome, and change in heart-failure symptoms and physical limitations at 52 weeks |
A placebo comparator is what allows a trial to claim the drug caused the difference. An active comparator answers a weaker question — whether the drug is at least as good as one already shown to work — and the two are routinely reported in the same words.
What did it find?
A 38% reduction in the combined endpoint of cardiovascular death and worsening heart-failure events, with improvement in symptoms, physical limitations and exercise capacity
A trial result is a mean across a population, not a prediction for an individual. The same trial that produces an average contains people who did far better and people who did not respond, and a page quoting only the average is quoting the part that flatters it.
What were the adverse events and discontinuations?
Adverse events are reported in the primary publication.
What are the limitations?
Industry-funded. Restricted to obesity-related HFpEF, a specific phenotype, so the result should not be generalised to heart failure broadly or to HFpEF without obesity. Relative risk reduction without the absolute event rate overstates the effect to most readers.
How should this be read, and how should it not?
- It describes the product that was studied. Every figure here was collected on the FDA-approved product. No compounded preparation has a trial of its own, and no figure on this page transfers to one.
- It describes the dose that was studied. A microdose sits below the range trialled here, so no result on this page applies to one at any price.
- It describes the population that was studied. A result in people with established cardiovascular disease does not transfer to primary prevention, and a result in diabetes does not transfer to weight management.
- It is not a dosing instruction. Your prescriber sets your regimen.
How does it compare with the other trials on this site?
| Trial | Intervention | Reported result | Duration |
|---|---|---|---|
| SUMMIT | Tirzepatide once weekly at maximum | A 38% reduction in the combined endpoint of cardiovascular death and worsening heart-failu | 52 weeks to the sympto |
| ATTAIN-1 | Orforglipron, once-daily oral non- | Approximately 11% to 12.4% mean weight reduction at the highest dose over 72 weeks. Lilly | 72 weeks |
| OASIS 4 | Oral semaglutide 25 mg once daily, | 13.6% mean weight reduction on the treatment-policy estimand versus 2.2% placebo; 16.6% ve | 64 weeks of treatment |
| SELECT | Semaglutide | Approximately a 20% relative reduction in the primary composite; event rate fell from roug | Mean follow-up approxi |
| STEP-1 | Semaglutide | Mean weight change of −14.9% against −2.4% on placebo; about 86% reached 5% or more, about | 68 weeks |
| STEP-8 | Semaglutide 2.4 mg weekly | Mean weight change approximately −15.8% on semaglutide against approximately −6.4% on lira | 68 weeks |
| SURMOUNT-1 | Tirzepatide once weekly | Treatment-regimen estimand: −15.0% (5 mg), −19.5% (10 mg), −20.9% (15 mg) versus −3.1% pla | 72 weeks |
| SURMOUNT-1, three-year prediabetes analysis | Tirzepatide once weekly | Three years of tirzepatide produced substantial sustained weight reduction and a markedly | 176 weeks of treatment |
| SURMOUNT-3 | not stated | −18.4% additional reduction versus +2.5% with placebo, on top of lead-in weight loss | 72 weeks |
| SURMOUNT-4 | not stated | Participants who continued lost a further 5.5%. Participants withdrawn to placebo regained | 88 weeks total, 36-wee |
Separate trials with different populations, durations and endpoints. Only a head-to-head supports a direct comparison between two drugs; the rest sit side by side here for reference, not for subtraction.
Frequently asked questions
Does this mean I would lose that much weight?
No. Trials report group averages under controlled conditions with specific eligibility criteria. Individual results vary widely, and the trial population may not resemble you.
Do these results apply to compounded tirzepatide?
Not automatically. Trials studied the approved product at studied doses. A compounded preparation at a different concentration, formulation or route has not been through those trials.
Related on this site
- Research hubResearch
- SURMOUNT-1 Tirzepatide Trial ExplainedResearch
- SURMOUNT-3 Tirzepatide Trial ExplainedResearch
- SURMOUNT-4: Weight Maintenance and Tirzepatide WithdrawalResearch
- The 100-point rubricCore & Trust
- Cost calculatorTools
- The underlying price recordsData
- Tirzepatide and PCOS: What Evidence Exists?Research
- Tirzepatide and Fatty Liver / MASHResearch
- Tirzepatide and Chronic Kidney DiseaseResearch
Related coverage
GLP-1 Semaglutide Rx. “SUMMIT Trial: Tirzepatide and HFpEF.” S.J Partners LLC, 2026-08-03. https://glp1semaglutiderx.com/research/summit-hfpef/
Quote the capture date beside a figure, not the date you read this page. Why.