SUMMIT: trial summary, limitations and UK relevance

Key findings

SUMMIT reported that tirzepatide reduced the composite of cardiovascular death or worsening heart-failure events versus placebo and improved patient-reported health status (KCCQ-CSS) in adults with heart failure with preserved ejection fraction (HFpEF) and obesity over 52 weeks. This is the first major incretin-class trial to demonstrate a clinical heart-failure benefit in the HFpEF + obesity intersection — a phenotype in which obesity is thought to drive part of the pathophysiology. Secondary endpoints on exercise-tolerance measures also improved with tirzepatide. The finding sits alongside STEP-HFpEF (semaglutide) as class-level HFpEF-in-obesity evidence, though the two trials differ in molecule, dose and endpoint framing. SUMMIT does not directly address HFpEF in non-obese individuals or HF with reduced ejection fraction. For precise numerical results consult the primary NEJM 2024 publication.

Safety summary

GI adverse events were the most common reported side effect. No novel safety signals in the primary publication beyond the established class profile.

Limitations

• HFpEF + obesity population — does not directly establish benefit in HFrEF or in non-obese HFpEF.
• 52-week duration relative to chronic heart-failure trajectory.

UK relevance

Highly UK-relevant evidence for the HFpEF + obesity intersection, informing UK cardiology and obesity-medicine pathways.