Semaglutide vs Tirzepatide vs Retatrutide vs Cagrilintide: A Research Sourcing Comparison
An identity, receptor-pharmacology, and analytical-verification comparison of the four most-sourced GLP-1 and metabolic research peptides — with CAS numbers, molecular weights, and per-lot documentation priorities.
Published May 30, 2026 · 8 min read · By Lyochem Regulatory Team
GLP-1 and metabolic research peptides are often sourced as a group, but Semaglutide, Tirzepatide, Retatrutide, and Cagrilintide are four distinct molecules with different receptor targets, different sizes, and different analytical-verification demands. Qualifying the right reference standard means matching each molecule's chemistry to the verification depth the study actually needs.
Which GLP-1 research peptide should a lab source, and how do they differ?
Semaglutide is a selective GLP-1 mono-agonist; Tirzepatide is a GIP / GLP-1 dual agonist; Retatrutide is a GIP / GLP-1 / glucagon tri-agonist; Cagrilintide is a long-acting amylin analog studied alongside Semaglutide (the combination referenced in the literature as CagriSema). All four should be verified by RP-HPLC purity plus ESI-MS identity, with LC-MS/MS sequence confirmation added for the longer 39-residue peptides (Tirzepatide, Retatrutide) and for any first-time supplier qualification. All are supplied as research reagents only.
Identity reference
| Peptide | CAS | Formula | Avg MW | Length | Receptor target |
|---|---|---|---|---|---|
| Semaglutide | 910463-68-2 | C187H291N45O59 | 4113.58 g/mol | 31 aa | GLP-1 (mono-agonist) |
| Tirzepatide | 2023788-19-2 | C225H348N48O68 | 4813.45 g/mol | 39 aa | GIP / GLP-1 (dual) |
| Retatrutide | 2381089-83-2 | Per batch COA | Per batch COA | 39 aa | GIP / GLP-1 / glucagon (tri) |
| Cagrilintide | 1415456-99-3 | Per batch COA | Per batch COA | amylin analog | Amylin receptor |
Every Lyochem lot confirms identity by ESI-MS against the theoretical mass for the supplied form and reproduces the value on the batch COA so it can be cited directly in a methods section. Retatrutide and Cagrilintide are investigational; their precise formula and salt mass are best read from the lot COA rather than a single catalog value.
Receptor pharmacology: a mono- to tri-agonist series
These molecules form a useful receptor-pharmacology progression. Semaglutide engages a single incretin receptor (GLP-1). Tirzepatide adds GIP-receptor agonism for a dual mechanism. Retatrutide adds a third arm, glucagon-receptor agonism, on top of the GIP / GLP-1 pair. Cagrilintide sits outside the incretin axis entirely, acting through the amylin pathway, which is why it is studied in combination with a GLP-1 agonist rather than as a substitute for one.
In the published metabolic-research literature, the progression from mono- to dual- to tri-agonism corresponds to increasing effects on glucose handling and body composition, which is why the four are frequently studied side by side as a receptor-pharmacology series rather than as interchangeable compounds.
Why longer peptides need deeper verification
Sequence length drives verification difficulty. Semaglutide is 31 amino acids; Tirzepatide and Retatrutide are 39. A longer solid-phase synthesis produces more closely-related deletion and aspartimide by-products that co-elute near the target peak on RP-HPLC and cannot be separated by intact mass alone.
That is the core reason mass spec is necessary but not sufficient. ESI-MS confirms the molecular weight matches theory; it does not confirm residue order, and isobaric substitutions can pass a mass check while still being wrong for a sequence-sensitive assay. For first-lot qualification of Tirzepatide or Retatrutide, request the LC-MS/MS b/y-ion ladder, which demonstrates the synthesized sequence matches the labelled sequence.
Counter-ion, water, and stability
For all four, the practical handling questions are the same: counter-ion form (acetate by default; TFA suppresses some cell-based readouts), water content by Karl Fischer (which affects the true peptide mass per vial), and lyophilized stability at minus 20 degrees Celsius protected from light. For in vivo metabolic-model work, request bacterial endotoxin (LAL) on the specific lot, since endotoxin contamination confounds many metabolic and inflammatory readouts.
Sourcing scale and framing
Lyochem supplies all four as reference-grade research standards at milligram scale, characterized lot-by-lot, and labelled strictly Research Use Only. That is a different scope from compounding-grade or kilogram-scale API supply intended for finished-dose preparation. For the CagriSema combination, Lyochem supplies Cagrilintide and Semaglutide as separate characterized lots rather than a pre-mixed blend, so each component can be confirmed against its own analytical packet before the combination is prepared in-protocol.
Talk to our regulatory team
Sourcing a GLP-1 or metabolic reference standard?
Send the molecule, target purity, intended assay, and whether this is first-lot qualification. Lyochem will map the analytical packet before quote.
Frequently asked questions
- What is the difference between Semaglutide, Tirzepatide, and Retatrutide?
- They differ by receptor target and size. Semaglutide (CAS 910463-68-2, 31 amino acids) is a selective GLP-1 mono-agonist. Tirzepatide (CAS 2023788-19-2, 39 amino acids) is a GIP / GLP-1 dual agonist. Retatrutide (CAS 2381089-83-2, 39 amino acids) is a GIP / GLP-1 / glucagon tri-agonist. In the published metabolic-research literature the progression from mono- to dual- to tri-agonism corresponds to increasing effects on glucose handling and body composition.
- Which of these GLP-1 peptides need LC-MS/MS sequence verification?
- Sequence-level verification is most important for the longer 39-residue peptides, Tirzepatide and Retatrutide, and for any first-time supplier qualification of any of them. A longer solid-phase synthesis produces closely-eluting deletion by-products that co-elute near the target on RP-HPLC and cannot be separated by intact mass alone, so the LC-MS/MS b/y-ion ladder is the test that confirms the synthesized sequence matches the labelled sequence.
- What CAS numbers identify these GLP-1 and metabolic research peptides?
- Semaglutide is CAS 910463-68-2 (C187H291N45O59, 4113.58 g/mol). Tirzepatide is CAS 2023788-19-2 (C225H348N48O68, 4813.45 g/mol). Retatrutide is CAS 2381089-83-2. Cagrilintide is CAS 1415456-99-3. For the two investigational compounds (Retatrutide, Cagrilintide), the precise formula and salt mass are best read from the batch COA for the specific lot.
- Are these GLP-1 peptides finished drugs?
- No. Lyochem supplies all four as bulk research reagents for Research Use Only, characterized lot-by-lot at milligram scale, not labelled for human administration and not finished dosage forms. Some GLP-1 analogues exist as approved finished drugs under separate brand names, but the material supplied here is a research reagent; buyers are responsible for institutional biosafety review and verifying import eligibility in the destination market.