Evidence Trace, complete trial record

In plain terms

In plain terms: Tirzepatide shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.

Tirzepatide

C Limited: small, mixed or unreplicated trials

Category Longevity Rx

Class Dual GIP and GLP-1 receptor agonist · Prescription only

Evidence Randomized controlled trials

Reviewed August 2026

PMIDs 39536238 · 41406444

The endpoint this grade is based on: Hard clinical endpoint (mortality, major event), Prevention of progression to type 2 diabetes in obesity with prediabetes, and weight reduction. Its cardiovascular trial was designed to show it is not worse than another drug, not that it beats placebo.

The evidence as the record states it

Evidence record

PMID 39536238 PMID 41406444

Jastreboff et al., SURMOUNT-1 three-year analysis (New England Journal of Medicine, 2025; PMID 39536238): phase 3, 2,539 participants with obesity of whom 1,032 had prediabetes, 176 weeks of treatment. Onset of type 2 diabetes 1.3% on tirzepatide versus 13.3% on placebo, hazard ratio 0.07. Mean weight change at 176 weeks was -12.3% to -19.7% by dose versus -1.3%. Nicholls et al., SURPASS-CVOT (New England Journal of Medicine, 2025; PMID 41406444): 13,299 adults with type 2 diabetes and atherosclerotic disease randomized to tirzepatide or dulaglutide, an ACTIVE comparator already shown to reduce events. The primary composite occurred in 12.2% versus 13.1%. That is a non-inferiority result against another drug, not a demonstration of benefit against placebo. Incident diabetes is a hard clinical outcome, but the SURMOUNT-1 result is a single trial, which under Rule 03 is C until a second trial repeats it.

PMID 39536238 PMID 41406444

Why Grade C and not Grade B

Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.

What this grade covers and what it does not

Grade C on onset of type 2 diabetes in obesity with prediabetes, resting on one trial: in SURMOUNT-1's three-year analysis, diabetes developed in 1.3 percent on tirzepatide against 13.3 percent on placebo (Jastreboff et al., 2025; PMID 39536238). The result is large and the outcome is clinical, but under Rule 03 a single positive trial nobody has independently repeated is C however large or well run, the rule that moved retatrutide to C in October. The cardiovascular trial, SURPASS-CVOT (Nicholls et al., 2025; PMID 41406444), compared tirzepatide with dulaglutide, an active drug, and showed it was not worse; it is not a placebo-controlled benefit. WHAT THIS GRADE DOES NOT COVER: weight loss as its own endpoint, a surrogate; cardiovascular events against placebo, which no trial has tested; and healthy adults taking it for longevity, which no trial has studied. It returns to B when a second trial reports diabetes onset as a prespecified outcome.

What would move this grade

A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.

How this was studied

Tirzepatide subcutaneously once weekly, dose-escalated to 5, 10 or 15 mg, for 176 weeks in SURMOUNT-1. SURPASS-CVOT compared tirzepatide against dulaglutide rather than placebo.

How to track whether this is working Prescription only; requires physician management. Weight, HbA1c and lean mass.