Research comparison
A side-by-side comparison of Semaglutide - a single-target GLP-1 receptor agonist - and Retatrutide, a triple agonist at the GLP-1, GIP and glucagon receptors. Mechanism, sequence, pharmacokinetics, lab handling, and how researchers select between them. Both compounds are supplied for in-vitro laboratory research only - not for human consumption.
| Semaglutide | Retatrutide | |
|---|---|---|
| Receptor profile | GLP-1 receptor agonist (single-target) | GLP-1 + GIP + glucagon receptor agonist (triple) |
| Residue count | 31 amino acids | 39 amino acids |
| Molecular weight | ~4,113.6 g/mol | ~4,731.4 g/mol |
| Reported half-life | ~165 hours (human serum) | ~6 days (primate models) |
| Clinical status | Approved (FDA 2017) | Phase 3 (ongoing 2024–2026) |
| Sizes stocked | 2–30 mg vials | 5–60 mg vials |
| Reference page | Semaglutide → | Retatrutide → |
Semaglutide is a synthetic 31-amino-acid peptide that shares approximately 94% sequence homology with native human glucagon-like peptide-1 (GLP-1). The molecule is acylated at Lys-26 with a long-chain fatty diacid linker (γGlu-2xOEG-C18), which dramatically extends its serum half-life by promoting reversible binding to albumin. This single modification shifts Semaglutide from native GLP-1's minute-scale pharmacokinetics into a once-weekly profile in human studies (~165 hours).
In the research literature, Semaglutide is characterised as a high-affinity, single-target agonist of the GLP-1 receptor (GLP-1R), a class B G-protein-coupled receptor expressed on pancreatic β-cells, central nervous system neurons, and gastrointestinal tissues. Activation drives glucose-dependent insulin secretion, suppresses glucagon release, and modulates satiety and gastric emptying pathways characterised in numerous published studies.
Retatrutide (research code LY3437943) is a synthetic 39-amino-acid peptide engineered as the first triple-receptor agonist progressed to late-stage clinical research. Unlike Semaglutide's single-target action, Retatrutide engages three incretin and counter-regulatory receptors simultaneously: glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon.
The molecule incorporates α-aminoisobutyric acid substitutions for enzymatic stability and a fatty-acid chain at Lys-17 for albumin binding. Reported half-life in primate pharmacokinetic studies is approximately 6 days, supporting a once-weekly dosing schedule in published Phase 2 trials. The triple-receptor approach is hypothesised in the literature to combine GLP-1's insulinotropic and satiety signalling with glucagon-driven energy expenditure and GIP's adipose-tissue effects, producing larger composite weight-loss outcomes than single- or dual-agonist comparators in published Phase 2 data.
The two compounds differ fundamentally in receptor engagement - this is the single most important distinction for researchers selecting between them.
| Pathway | Semaglutide | Retatrutide |
|---|---|---|
| GLP-1 receptor | High-affinity agonist | High-affinity agonist |
| GIP receptor | No direct activity | High-affinity agonist |
| Glucagon receptor | No direct activity | Agonist (intermediate affinity) |
| Primary research signal | Glucose-dependent insulin secretion, satiety pathway | Insulinotropic + adipose modulation + glucagon-driven energy expenditure |
| Reported research outcome (Phase 2) | ~15% weight reduction at 68 weeks (STEP-1) | ~24% weight reduction at 48 weeks (Jastreboff 2023) |
Both compounds are stocked as research-grade reference standards. Selection depends on the specific experimental hypothesis being tested.
Both Semaglutide and Retatrutide are supplied as lyophilised (freeze-dried) powder in sealed glass vials. For laboratory reconstitution, add the desired volume of bacteriostatic water slowly down the side wall of the vial. Swirl gently until fully dissolved - do not vortex or shake. Store reconstituted solutions at 2–8 °C and use within 4 weeks.
For reconstitution maths see our Reconstitution Volume Calculator, or read the full Research Handling Guide for stability and storage protocols.
| State | Temperature | Shelf life |
|---|---|---|
| Lyophilised (both) | 2–8 °C or −20 °C | 24+ months |
| Reconstituted (both) | 2–8 °C | ~28 days typical |
Both compounds are independently HPLC-verified by Janoshik Analytical at 99%+ purity. Where a Janoshik report has been issued for the current batch it is supplied with the order, and the verification record is also published on the Purity page so you can match the printed report to the public record.
Semaglutide is a single-target GLP-1 receptor agonist with ~94% sequence homology to native human GLP-1. Retatrutide is a triple agonist acting at the GLP-1, GIP, and glucagon receptors. Triple agonism in the published literature is associated with broader metabolic effects in preclinical and Phase 2 research.
Published research reports Semaglutide's serum half-life at approximately 165 hours in human pharmacokinetic studies, and Retatrutide at approximately 6 days (~144 hours) in primate models. Both are characterised in the literature as suitable for once-weekly dosing schedules in preclinical research protocols.
In published Phase 2 trial data, Retatrutide produced larger weight-loss outcomes than Semaglutide in comparable cohorts. However, direct head-to-head Phase 3 data are still emerging, and potency is dependent on the specific endpoint measured (HbA1c, body composition, hepatic outcomes).
Yes. Black & White Peptides Ltd supplies both compounds as lyophilised research-grade peptides for in-vitro laboratory characterisation. Every batch is independently HPLC-verified by Janoshik Analytical at 99%+ purity. Research use only - not for human consumption.
Both peptides are supplied as lyophilised powder in sealed vials. Reconstitute with bacteriostatic water added slowly down the side wall, swirling gently until fully dissolved. Use the on-site Reconstitution Volume Calculator to compute resulting mg/mL concentrations for your protocol.
References are independent peer-reviewed sources. Black & White Peptides Ltd is not affiliated with these publications.