Tirzepatide Research: SURPASS, SURMOUNT & SURMOUNT-OSA Trial Data
A trial-by-trial look at the tirzepatide clinical programmes — SURPASS, SURMOUNT and SURMOUNT-OSA — with study designs, headline numbers and links to the original publications.
Mechanism of action
Tirzepatide is a synthetic 39-amino-acid peptide that activates two incretin receptors: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Single-agonist GLP-1 compounds engage only the second of these.
A C20 fatty di-acid moiety attached to the backbone drives albumin binding, slowing renal clearance and extending the half-life to roughly five days — the basis for once-weekly dosing.
Dual agonism appears to be more than additive: GIP receptor activity contributes to insulin sensitivity and adipose-tissue handling of nutrients, while GLP-1 activity drives satiety, delayed gastric emptying and glucose-dependent insulin secretion. The SURPASS and SURMOUNT programmes were designed to test whether this translates into larger measurable effects than GLP-1 agonism alone.
The studies
The tirzepatide evidence base rests on two large phase 3 programmes plus a dedicated sleep-apnoea trial. Each card states the objective, the design, the headline result and the source publication.
SURPASS programme
SURPASS-2 — tirzepatide versus semaglutide in type 2 diabetes
To compare the efficacy and safety of once-weekly tirzepatide (5, 10 and 15 mg) against once-weekly semaglutide 1 mg in adults with type 2 diabetes inadequately controlled on metformin.
1,879 adults with type 2 diabetes · 40 weeks · randomised, open-label, active-comparator controlled
- 2.30%
- HbA1c reduction (15 mg)
- 11.2 kg
- Mean weight loss (15 mg)
- 46%
- Reached HbA1c < 5.7%
vs 1.86% semaglutide
vs 5.7 kg semaglutide
on 15 mg vs 19% semaglutide
- SURPASS-2 was the first head-to-head trial showing a dual GIP/GLP-1 agonist outperforming a GLP-1-only comparator on both glucose and weight endpoints.
- The effect was dose-dependent across the 5, 10 and 15 mg arms.
- Gastrointestinal adverse events were the most common issue in both arms and were broadly comparable in frequency.
SURMOUNT programme
SURMOUNT-1 — obesity and weight management
To evaluate once-weekly tirzepatide for chronic weight management in adults with obesity, or overweight with at least one weight-related complication, and without diabetes.
2,539 adults · 72 weeks · randomised, double-blind, placebo-controlled
- 20.9%
- Mean weight loss (15 mg)
- 15.0%
- Mean weight loss (5 mg)
- 57%
- Participants losing ≥ 20% body weight
vs 3.1% placebo
vs 3.1% placebo
on 15 mg
- SURMOUNT-1 produced the largest average weight reduction recorded for a once-weekly injectable in a non-surgical trial at the time of publication.
- Waist circumference, blood pressure, insulin and lipid measures all improved alongside weight.
- Weight loss had not fully plateaued by week 72, suggesting the ceiling was not reached within the trial period.
SURMOUNT-OSA — obstructive sleep apnoea
To determine whether tirzepatide reduces the severity of moderate-to-severe obstructive sleep apnoea in adults with obesity, both with and without concurrent CPAP therapy.
469 adults across two parallel trials · 52 weeks · randomised, double-blind, placebo-controlled
- up to 29.3 events/hr
- Reduction in apnoea-hypopnoea index
- 17.7% – 19.6%
- Mean weight reduction
- ~50%
- Participants reaching remission or mild OSA
vs 5.5 placebo
- SURMOUNT-OSA was the first trial to show a pharmacological agent meaningfully reducing sleep-apnoea severity rather than only managing symptoms mechanically.
- Benefit was seen both in participants using CPAP and those who were not.
- Improvements in hypoxic burden and patient-reported sleep disturbance tracked with the reduction in body weight.
SURPASS programme
SURPASS-CVOT — cardiovascular outcomes
To assess cardiovascular outcomes with tirzepatide compared with dulaglutide in adults with type 2 diabetes and established atherosclerotic cardiovascular disease.
13,299 adults · median follow-up ~4.5 years · randomised, double-blind, active-comparator controlled
- Non-inferior
- Primary MACE endpoint
- Lower
- All-cause mortality
- Greater reduction
- HbA1c and weight
vs dulaglutide
numerically vs comparator
vs dulaglutide
- SURPASS-CVOT compared tirzepatide against an active GLP-1 agonist rather than placebo — a more demanding design than most outcome trials.
- Cardiovascular safety was established alongside superior metabolic control.
- Read the primary publication directly for the full endpoint definitions before citing individual numbers.
Storage & handling
Tirzepatide research material is supplied as a lyophilised powder. Store sealed vials refrigerated or frozen, protected from light and moisture.
Reconstitute with bacteriostatic water added slowly down the inner wall of the vial; swirl gently until fully dissolved — do not shake.
Keep reconstituted solution at 2-8 °C and use within the stability window defined by your lab's standard operating procedures. Avoid repeated freeze-thaw cycles.
All information on this page is provided for laboratory and educational reference only. Peptides Lab SA (PTY) Ltd supplies compounds strictly for in-vitro research use. Nothing here is medical advice, a dosing recommendation, or a claim of human safety or efficacy.