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Retatrutide vs Semaglutide — Canada Research Comparison

By Dr. Elena Morozova, PhDReviewed by Dr. Elena Morozova, PhDPublished April 11, 2026Last reviewed April 11, 20262 min read
Quick answer

Retatrutide is an investigational GLP-1 / GIP / glucagon triple agonist in Phase 3, while semaglutide is a Health Canada approved single GLP-1 receptor agonist sold as Ozempic, Rybelsus, and Wegovy.

At a glance

Retatrutide and semaglutide sit at opposite ends of the incretin evidence curve. Semaglutide is the most extensively studied GLP-1 receptor agonist in modern medicine, with a complete Phase 3 programme, two cardiovascular outcomes trials, and Health Canada approval across three brand names. Retatrutide is the newest and most mechanistically ambitious member of the class — a triple agonist with one Phase 2 obesity readout and an ongoing Phase 3 programme.

Key facts

FeatureRetatrutide (LY3437943)Semaglutide
ClassGLP-1 / GIP / glucagon triple agonistGLP-1 receptor agonist (single)
Receptors activatedGLP-1R, GIPR, GCGRGLP-1R only
DeveloperEli LillyNovo Nordisk
Approval (Canada)None — Phase 3Ozempic, Rybelsus, Wegovy
Key obesity trialPhase 2, Jastreboff NEJM 2023STEP 1, Wilding NEJM 2021
Reported weight loss~24.2% at 48w (12 mg)~14.9% at 68w (2.4 mg)
CV outcomes dataNoneSUSTAIN-6 (2016), SELECT (2023)
DosingOnce weekly SCOnce weekly SC (or oral Rybelsus)
Half-life~6 days (reported)~165 hours (~7 days)

Mechanism contrast

Semaglutide is a 31-amino-acid GLP-1 analogue with a C18 fatty-acid chain on Lys26 that binds plasma albumin and extends its half-life to roughly a week. The downstream biology is the canonical GLP-1 profile: glucose- dependent insulin secretion, glucagon suppression from pancreatic α-cells, delayed gastric emptying, and hypothalamic appetite suppression.

Retatrutide keeps the GLP-1 arm and layers on two additional pathways. GIP receptor agonism potentiates insulin release and modulates adipose fatty-acid handling. Glucagon receptor agonism — counterintuitively, the same receptor that raises blood glucose — contributes hepatic fat oxidation and increased resting energy expenditure when paired with a GLP-1 counterweight.

Evidence quality

Semaglutide is supported by eight Phase 3 STEP trials, the SUSTAIN programme in type 2 diabetes, and two cardiovascular outcomes trials. Retatrutide rests on a single published Phase 2 obesity trial with 338 randomised participants and 48 weeks of follow-up. Until the TRIUMPH Phase 3 results report, any claim about retatrutide's long-term safety or vascular effects is an extrapolation from Phase 2 data.

Regulatory status

Semaglutide is Health Canada approved under multiple brand names. Retatrutide has no marketing authorisation from any regulator.

Frequently asked questions

What is the core mechanistic difference between retatrutide and semaglutide?
Semaglutide is a single-pathway GLP-1 receptor agonist. Retatrutide activates three receptors simultaneously — GLP-1, GIP, and glucagon. The glucagon receptor arm is associated in preclinical models with increased energy expenditure and decreased hepatic lipid content, effects that semaglutide's pure GLP-1 mechanism does not directly produce.
How do reported weight reductions compare?
In STEP 1 (Wilding et al., NEJM 2021), once-weekly semaglutide 2.4 mg produced mean weight reduction of approximately 14.9% at 68 weeks. In the Phase 2 trial by Jastreboff et al. (NEJM 2023), retatrutide 12 mg produced mean weight reduction of approximately 24.2% at 48 weeks. These are cross-trial figures and should be interpreted cautiously — no head-to-head trial has been published.
Does retatrutide have cardiovascular outcomes data like semaglutide?
No. Semaglutide has two major cardiovascular outcomes datasets — SUSTAIN-6 (type 2 diabetes, Marso et al., NEJM 2016) and SELECT (overweight/obesity with established CVD, Lincoff et al., NEJM 2023). Retatrutide has no published cardiovascular outcomes trial. This is a substantial evidence-base gap in favour of semaglutide for any question involving long-term vascular risk.
Is retatrutide approved in Canada?
No. Retatrutide is an Eli Lilly investigational compound currently in Phase 3 (the TRIUMPH programme). Semaglutide is Health Canada approved as Ozempic and Rybelsus for type 2 diabetes and as Wegovy for chronic weight management. Research-grade material of either peptide is sold in Canada as a laboratory reagent only.

References

  1. [1]Jastreboff AM, Kaplan LM, Frías JP, et al.. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine, 2023. DOI: 10.1056/NEJMoa2301972
  2. [2]Wilding JPH, Batterham RL, Calanna S, et al.. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine, 2021. DOI: 10.1056/NEJMoa2032183
  3. [3]Lincoff AM, Brown-Frandsen K, Colhoun HM, et al.. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). New England Journal of Medicine, 2023. DOI: 10.1056/NEJMoa2307563
  4. [4]Marso SP, Bain SC, Consoli A, et al.. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes (SUSTAIN-6). New England Journal of Medicine, 2016. DOI: 10.1056/NEJMoa1607141

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