A new Forbes article published June 3, 2026, takes a timely look at one of the most pressing questions in obesity medicine: how does retatrutide — Eli Lilly’s investigational triple-hormone receptor agonist — compare with semaglutide, the current market leader sold as Ozempic and Wegovy? As retatrutide advances through Phase 3 trials and moves closer to regulatory submission, understanding the differences between these two medications matters for patients, clinicians, and policymakers alike.
Different mechanisms, different results
Semaglutide is a GLP-1 receptor agonist. It mimics the action of glucagon-like peptide-1, a hormone that slows gastric emptying, promotes satiety, and stimulates insulin secretion. Approved in Canada since 2018 for type 2 diabetes (as Ozempic) and 2021 for weight management (as Wegovy), semaglutide produces an average weight loss of approximately 15% of body weight in clinical trials.
Retatrutide takes a fundamentally different approach. It is a single molecule that activates three receptors: GLP-1, GIP (glucose-dependent insulinotropic polypeptide), and glucagon. This triple-agonist mechanism targets multiple metabolic pathways simultaneously. In the Phase 2 trial published in the New England Journal of Medicine, retatrutide produced mean weight loss of up to 24.2% at 48 weeks in the highest dose group — roughly 9 percentage points more than what semaglutide achieved in its pivotal STEP trials.
The recently announced TRIUMPH-1 Phase 3 results confirmed these findings at scale: participants receiving the highest retatrutide dose lost an average of 71.2 pounds (32.3 kg), representing approximately 27% of their starting body weight. Some participants achieved weight loss exceeding 30%.
Side effect profiles
Both medications carry gastrointestinal side effects — nausea, vomiting, diarrhea — that are most pronounced during dose escalation. The pattern is familiar to anyone who has taken a GLP-1 medication, but retatrutide’s triple-receptor action introduces additional considerations. Some trial participants experienced transient increases in heart rate, a known effect of glucagon receptor activation. Cardiac monitoring was part of the TRIUMPH-1 protocol, and no concerning safety signals emerged at the trial level.
Semaglutide’s safety profile is well-established after years of post-market surveillance. Retatrutide, still investigational, has a shorter safety track record. Long-term outcomes data — cardiovascular benefit, durability of weight loss, rare adverse events — will only emerge after regulatory approval and years of real-world use.
Availability and access
This is where the comparison becomes most relevant for Canadians. Semaglutide is available through Canadian pharmacies today, though access varies by province and insurance coverage. Wegovy was approved by Health Canada in 2021 but faced supply shortages that limited its real-world availability until late 2023. Ozempic, approved for diabetes but frequently prescribed off-label for weight loss, remains widely available but is not covered by most provincial drug plans for obesity treatment alone.
Retatrutide has not yet been submitted for regulatory review. Eli Lilly is expected to file for FDA approval following completion of the TRIUMPH program, with Health Canada review likely to follow. Realistically, Canadian patients are at least 18 to 24 months from seeing retatrutide on pharmacy shelves — and that timeline assumes successful completion of all remaining Phase 3 trials, regulatory approval, pricing negotiations with the Patented Medicine Prices Review Board, and provincial formulary listings.
Canadian context
For the approximately 30% of Canadian adults living with obesity, the semaglutide-to-retatrutide pipeline represents a genuine step-change in treatment options. The Canadian obesity pharmacotherapy landscape has historically lagged behind the United States, with fewer approved medications, slower formulary adoption, and limited public coverage.
The arrival of retatrutide could shift this dynamic — but only if provincial drug plans are prepared to cover it. At an estimated list price that may exceed current GLP-1 medications, cost will be a central barrier. The Canadian Agency for Drugs and Technologies in Health (CADTH) will play a pivotal role in determining whether retatrutide receives a positive reimbursement recommendation, which heavily influences provincial coverage decisions.
Canadian patients considering these medications should know that semaglutide is available now, while retatrutide remains investigational. Participation in clinical trials — several TRIUMPH program sites are active in Canada — represents the only current pathway to access retatrutide domestically.