Mechanism — single, dual, triple receptor agonism
Semaglutide is a single-receptor GLP-1 agonist with no meaningful GIP or glucagon receptor activity. It is the cleanest published reference compound for isolating GLP-1 signalling in metabolic research.
Tirzepatide is a dual GLP-1 / GIP agonist — a single 39-amino-acid peptide engineered to activate both incretin axes simultaneously. The addition of GIP agonism produces a stronger composite metabolic signal than GLP-1 activation alone in the published preclinical and clinical literature.
Retatrutide is a balanced triple GLP-1 / GIP / glucagon agonist. The glucagon receptor arm is the headline distinction from tirzepatide — in published preclinical and phase 2 clinical research, triple-receptor activation has been associated with stronger hepatic-lipid oxidation and resting-energy-expenditure signals than either dual-incretin or single-GLP-1 activation.
Receptor profile at a glance
Semaglutide: GLP-1 selective. Receptor occupancy and potency profiles make it the published reference for single-axis GLP-1 work and the natural GLP-1-only arm in dual or triple comparator panels.
Tirzepatide: balanced GLP-1 / GIP agonism with engineering that favours sustained GIP receptor occupancy alongside GLP-1 signalling. Receptor-bias literature continues to characterise the precise downstream signalling differences vs semaglutide.
Retatrutide: balanced GLP-1 / GIP / glucagon agonism, with the glucagon arm contributing the hepatic-lipid and energy-expenditure signal that distinguishes the compound from tirzepatide. Receptor-balance literature is still maturing.
Clinical-trial programmes — SURPASS, SURMOUNT, TRIUMPH
Semaglutide is supported by the SUSTAIN (type 2 diabetes) and STEP (obesity) trial families, plus the SELECT cardiovascular-outcomes trial — the deepest published clinical-research dataset of the three compounds and the basis for most translational comparator work.
Tirzepatide is supported by the SURPASS (type 2 diabetes) and SURMOUNT (obesity) trial families, with SURMOUNT-MMO running for cardiovascular and all-cause-mortality endpoints. The SURPASS-2 head-to-head against semaglutide is the most cited direct dual-vs-single comparison in the public literature.
Retatrutide is supported by the TRIUMPH phase 2 / phase 3 trial programme, with TRIUMPH-1 (obesity), TRIUMPH-2 (type 2 diabetes with overweight), TRIUMPH-3 (cardiovascular) and TRIUMPH-4 (knee osteoarthritis with obesity) defining the published phase 2 data and the active phase 3 programme. The phase 2 readouts are the basis for the current research interest in the compound.
Pharmacokinetics and research half-life
Semaglutide carries a C18 fatty diacid modification that supports a multi-day research half-life — typical reported half-life is approximately 165 hours (around 7 days), suitable for weekly-cadence research protocols. Stable to DPP-4 degradation.
Tirzepatide carries a C20 fatty diacid modification with a comparable acylation-driven albumin-binding profile — typical reported half-life is approximately 120 hours (around 5 days), supporting weekly research cadence with a slightly shorter exposure tail than semaglutide.
Retatrutide carries a fatty-acid modification supporting an extended half-life in a similar range to tirzepatide — reported half-life is approximately 6 days, also supporting weekly research cadence. Pharmacokinetic comparisons in research models typically use matched weekly dosing across all three compounds.
Research applications by compound
Semaglutide is chosen when the protocol requires a clean GLP-1-only arm, when re-using the extensive published clinical literature is part of the project design, or when a comparator study explicitly needs all three receptor-class arms. It is the reference single-axis GLP-1 compound.
Tirzepatide is chosen when the protocol requires dual GLP-1 / GIP signalling without glucagon receptor activation — typically energy-expenditure, hepatic-lipid or composite-metabolic models where the GIP arm is expected to amplify the GLP-1 signal. It remains the dual-agonist reference compound.
Retatrutide is chosen when the protocol requires the additional hepatic-lipid and energy-expenditure signal driven by the glucagon arm, or when a three-arm comparator study explicitly needs single / dual / triple receptor agonism in matched arms under a single analytical specification window.
Analytical specification on every Regena batch
Semaglutide, tirzepatide and retatrutide ship from Regena only after independent third-party verification — Janoshik Analytical is the default verifier, with orthogonal independent laboratories used when batch chemistry calls for confirmation by a second method. Minimum release specification is ≥99.0% HPLC main-peak purity with matching mass-spectrometry molecular weight and water content within the published specification for each compound.
Batch COAs for all three compounds are published on the Regena lab reports page so a research-peptide buyer can audit the analytical detail before purchase. The /trust/how-to-read-a-coa reference walks through every field on a modern Regena COA.
Handling, reconstitution and stability
All three compounds ship lyophilised under nitrogen. Hold the unopened vial at 2–8 °C; freeze at −20 °C for long-term storage. Reconstitution with bacteriostatic water (0.9% benzyl alcohol) supports a 28-day in-use stability window under refrigeration for semaglutide, tirzepatide and retatrutide alike.
Aliquot before any freeze. The single most common cause of measurable potency loss in research peptides is repeat freeze-thaw cycling — all three compounds benefit from single-thaw aliquot workflows. Vortex gently, never shake aggressively, and keep reconstituted vials away from direct light. The /research/compound-storage-guide reference covers the per-compound stability windows in detail.
When researchers pick single vs dual vs triple
Single (semaglutide): translational research re-using the GLP-1 clinical literature, single-axis receptor-selectivity work, the GLP-1-only arm in dual- or triple-comparator panels.
Dual (tirzepatide): protocols requiring GLP-1 / GIP synergy without glucagon receptor activation — energy-expenditure, hepatic-lipid and composite-metabolic models where the GIP arm amplifies GLP-1 signalling.
Triple (retatrutide): protocols where the glucagon arm is part of the experimental design — hepatic-lipid oxidation, resting-energy-expenditure and composite-metabolic models where triple-receptor activation is the headline pharmacological question.
For three-arm comparator studies, the Regena consultations team will reserve matched-batch inventory of semaglutide, tirzepatide and retatrutide against a project timeline so the experimental panel is sourced under a single analytical specification window.
Regulatory and research-use framing
Semaglutide, tirzepatide and retatrutide are supplied strictly for in-vitro and preclinical research use. They are not medicines, are not approved for human consumption in Spain, the United Kingdom, the European Union or the United States, and are not dispensed against a prescription. The research-use declaration ships with every package alongside the independent third-party COA.
Comparison pages on the Regena site exist for laboratory-research reference. Nothing on this page constitutes a recommendation for human use of any of the three compounds.
Frequently asked questions
What is the main difference between retatrutide, tirzepatide and semaglutide?+
Receptor count. Semaglutide is a single GLP-1 agonist; tirzepatide is a dual GLP-1 / GIP agonist; retatrutide is a triple GLP-1 / GIP / glucagon agonist. The added receptor arms are the headline pharmacological distinctions and drive the differences in metabolic, hepatic-lipid and energy-expenditure signal in published research.
Which has the longest research half-life?+
Semaglutide, at approximately 165 hours (~7 days). Tirzepatide is approximately 120 hours (~5 days) and retatrutide approximately 6 days. All three support weekly-cadence research protocols and are stable to DPP-4 degradation thanks to fatty-acid acylation.
Which clinical trial programmes back each compound?+
Semaglutide: SUSTAIN, STEP and SELECT. Tirzepatide: SURPASS and SURMOUNT, including the SURPASS-2 head-to-head against semaglutide. Retatrutide: the TRIUMPH phase 2 / phase 3 programme (TRIUMPH-1 through TRIUMPH-4).
Is retatrutide stronger than tirzepatide or semaglutide?+
In published phase 2 research, triple-receptor activation has been associated with stronger metabolic and hepatic-lipid signals than dual or single agonism — but receptor-balance, signalling-bias and dose-equivalence remain active research topics. Direct head-to-head trials are still maturing.
Can I order matched batches of all three for a comparator study?+
Yes — the Regena consultations team will reserve matched-batch inventory of semaglutide, tirzepatide and retatrutide against a project timeline so the experimental panel is sourced under a single analytical specification window.
What HPLC purity does Regena release each compound against?+
≥99.0% HPLC main-peak purity for all three compounds, with matching mass-spectrometry molecular weight and water content within the published specification for each compound. Janoshik Analytical is the default independent verifier.
Are any of these peptides approved for human use?+
No. All three are supplied strictly for in-vitro and preclinical research use. They are not medicines, are not approved for human consumption, and are not dispensed against a prescription.
Where can I see the current batch COAs?+
On the /coa lab reports page, indexed by compound and batch number. New batches appear within 24 hours of independent release for semaglutide, tirzepatide and retatrutide.