Research comparison
Semaglutide vs tirzepatide vs retatrutide
Semaglutide, tirzepatide and retatrutide are the three most discussed molecules in incretin research, and they form a clean progression: one receptor, two receptors, three. They also sit at very different points of the regulatory map, which matters more than any other difference between them.
This page compares the three research profiles. The profiles carry the citations; nothing here is a claim about effects in people.
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Category | Peptide analogue | Peptide analogue | Peptide analogue |
| Highest evidence | Clinical — evidence level 4 of 4: Established clinical evidence Findings come from adequately powered, replicated controlled trials in humans, generally supported by regulatory assessment or systematic review. | Clinical — evidence level 4 of 4: Established clinical evidence Findings come from adequately powered, replicated controlled trials in humans, generally supported by regulatory assessment or systematic review. | Early human — evidence level 3 of 4: Early human evidence Findings come from small, early-phase or observational human studies. These are typically short, sparsely replicated, and designed to examine tolerability or signal rather than to establish effect. |
| UK regulatory status | Prescription only — UK regulatory status: Prescription-only medicine (UK) A medicine that may lawfully be supplied in the UK only against a prescription from an appropriate practitioner. | Prescription only — UK regulatory status: Prescription-only medicine (UK) A medicine that may lawfully be supplied in the UK only against a prescription from an appropriate practitioner. | Experimental — UK regulatory status: Experimental — not authorised for human use in the UK A compound appearing in research literature that holds no UK authorisation for human use in any indication. |
| Research areas | Metabolic research; Incretin biology | Metabolic research; Incretin biology | Metabolic research; Incretin biology |
| Verified citations | 4 | 4 | 3 |
Semaglutide
A long-acting synthetic analogue of glucagon-like peptide-1. A prescription-only medicine in the UK.
Semaglutide is an analogue of human GLP-1 with three deliberate modifications: a substitution at position 8 that protects it from degradation by DPP-4, a C18 fatty diacid attached via a spacer at position 26 that binds albumin tightly, and a substitution at position 34 to direct where the fatty acid attaches. The design paper reports that these changes raise albumin affinity while preserving receptor potency, producing a half-life of around a week. GLP-1 receptor activation increases glucose-dependent insulin secretion, suppresses glucagon, slows gastric emptying and reduces appetite through receptors in the brain.
Tirzepatide
A synthetic dual agonist of the GIP and GLP-1 receptors. A prescription-only medicine in the UK.
Tirzepatide is a 39-amino-acid synthetic peptide built on the GIP sequence, engineered to activate both the glucose-dependent insulinotropic polypeptide receptor and the glucagon-like peptide-1 receptor, and carrying a C20 fatty diacid moiety that binds albumin and extends its half-life to around five days. The discovery work characterises it as an imbalanced agonist — closer to native potency at the GIP receptor than at the GLP-1 receptor — which its developers argue contributes to the metabolic effects observed. Receptor activation increases glucose-dependent insulin secretion, slows gastric emptying and reduces food intake.
Retatrutide
An investigational synthetic peptide studied as an agonist at the GIP, GLP-1 and glucagon receptors.
Retatrutide is a synthetic single-peptide agonist reported to act at three receptors: the glucose-dependent insulinotropic polypeptide receptor, the glucagon-like peptide-1 receptor and the glucagon receptor. Structurally it is a GIP-based peptide backbone carrying a fatty-acid modification that extends its half-life. Published receptor pharmacology reports sub-nanomolar potency at all three human receptors, with relatively greater activity at the GIP receptor than at the other two.
How the research differs
One receptor, two, three
Semaglutide is an analogue of human GLP-1 acting at the GLP-1 receptor. Tirzepatide is built on the GIP sequence and engineered to activate both the GIP and GLP-1 receptors. Retatrutide is reported to act at three: GIP, GLP-1 and the glucagon receptor. The receptor count is the defining structural difference, and each step is the subject of its own research literature.
Shared engineering, different backbones
All three use the same half-life trick — a fatty-acid moiety that binds serum albumin — but on different backbones: semaglutide on GLP-1 with a position-8 substitution protecting it from DPP-4 degradation, tirzepatide and retatrutide on GIP-based sequences. The profiles describe each modification precisely.
Very different regulatory positions
Semaglutide and tirzepatide are prescription-only medicines in the UK; their profiles exist here because the research literature is substantial, and both pages state that status plainly. Retatrutide is different: an investigational compound in clinical development, not an authorised medicine anywhere. The three pages should be read with that distinction in front of you.
Evidence maturity tracks the same order
Semaglutide and tirzepatide carry established clinical literatures. Retatrutide is at the early-human stage — published trial data exists but the programme is ongoing, and the profile grades it accordingly.