Cagrilintide structure explained: 37-amino-acid peptide, disulfide bridge, fatty acid side chain, molecular weight, pH, and why it resists fibril formation.
Cagrilintide is a synthetic, long-acting amylin analog built from 37 amino acids. Its structure includes a disulfide bridge between two cysteine residues, a C-terminal amide, and a fatty acid side chain that promotes albumin binding and extends its duration of action.
Understanding the cagrilintide structure helps explain why this peptide is studied for weight management and glycemic control. The molecular design also affects how the drug is formulated, how long it stays active, and how it avoids the fibril formation seen with native human amylin.
What Is Cagrilintide?
Cagrilintide is a peptide therapeutic developed by Novo Nordisk. It mimics amylin, a hormone co-secreted with insulin by pancreatic beta cells. Amylin slows gastric emptying, reduces glucagon secretion, and promotes satiety.
Unlike native amylin, cagrilintide is engineered for a much longer half-life. If you are new to this drug class, the guide on what is cagrilintide provides a helpful overview of its mechanism and development status.
Core Structural Features of Cagrilintide
The cagrilintide sequence is derived from human amylin but includes several amino acid substitutions. These changes improve solubility, stability, and receptor binding. The peptide also carries a fatty acid side chain that is absent in the natural hormone.
Peptide Backbone and Disulfide Bridge
Cagrilintide contains 37 amino acids, the same length as human amylin. A disulfide bridge connects cysteine residues at positions 2 and 7. This bridge constrains the peptide into a loop that is critical for receptor activation.
C-Terminal Amide
The C-terminus of cagrilintide is amidated. This modification protects the peptide from carboxypeptidase degradation and contributes to its metabolic stability. Human amylin also has a C-terminal amide, so this feature is conserved.
Fatty Acid Side Chain
A key difference is the fatty acid side chain attached to the peptide backbone. This lipid chain binds to serum albumin after injection. Albumin binding slows renal clearance and creates a depot effect, which supports once-weekly dosing.
Cagrilintide Acetate and Formulation
Cagrilintide is manufactured as cagrilintide acetate, the acetate salt form. Salt formation improves solubility and handling during production. The final drug product is a sterile solution for subcutaneous injection.
The formulation typically includes buffers, tonicity agents, and preservatives. The pH of the solution is kept near physiological levels, usually around 7.0 to 7.4. This range minimizes injection-site irritation and maintains peptide stability.
Cagrilintide Molecular Weight and pH
The cagrilintide molecular weight is approximately 4,400 Da. This value reflects the 37-amino-acid backbone plus the fatty acid side chain and the amide group. The molecular weight is large enough that the drug is not orally bioavailable and must be injected.
Table 1 summarizes key molecular properties.
| Property | Typical Value |
|---|---|
| Molecular weight | ~4,400 Da |
| pH of formulated solution | ~7.0–7.4 |
| Salt form | Acetate |
| Route | Subcutaneous injection |
| Dosing frequency | Once weekly (investigational) |
Fibril Formation and Structural Stability
Native human amylin is prone to forming amyloid fibrils, which are linked to pancreatic islet damage in type 2 diabetes. Cagrilintide fibrils are much less likely to form because of the amino acid substitutions in its sequence.
Structural studies show that the modified residues disrupt the beta-sheet-prone regions of amylin. This design reduces aggregation risk and improves shelf-life stability. Lower fibril formation also means fewer injection-site reactions and better long-term safety.
How Cagrilintide Compares to Other Peptide Therapies
Cagrilintide belongs to the amylin analog class, while tirzepatide is a dual GIP/GLP-1 receptor agonist and retatrutide is a triple agonist. A structural comparison of cagrilintide vs tirzepatide highlights different mechanisms: cagrilintide targets amylin receptors, while tirzepatide activates GIP and GLP-1 receptors.
Researchers are also exploring cagrilintide with retatrutide in combination strategies, though such use remains experimental. Table 2 compares basic structural features.
| Feature | Cagrilintide | Human Amylin |
|---|---|---|
| Amino acid length | 37 | 37 |
| Disulfide bridge | Yes (Cys2–Cys7) | Yes (Cys2–Cys7) |
| C-terminal amide | Yes | Yes |
| Fatty acid side chain | Yes | No |
| Fibril formation | Low | High |
| Half-life | Long (albumin-bound) | Short |
Safety and Clinical Considerations
Cagrilintide is not FDA-approved for human use in the United States. It remains an investigational drug. Clinical trials are still defining the optimal cagrilintide dosage for different patient populations.
Commonly reported adverse events include nausea, vomiting, diarrhea, and injection-site reactions. These effects are similar to other incretin-based therapies. Talk with your prescriber about cagrilintide side effects and monitoring.
Because cagrilintide affects gastric emptying and glucose control, it should be used under medical supervision. Self-dosing or using unregulated sources is unsafe and not recommended.
The Bottom Line on Cagrilintide Structure
The cagrilintide structure is defined by a 37-amino-acid amylin backbone, a conserved disulfide bridge, a C-terminal amide, and a fatty acid side chain that extends half-life. These features make it a long-acting, low-fibril-forming peptide.
Understanding the molecular design helps explain its once-weekly dosing potential and its investigational role in obesity and diabetes treatment. Always consult a healthcare professional before considering any experimental peptide therapy.
Frequently Asked Questions
What is the molecular weight of cagrilintide?
Cagrilintide has a molecular weight of approximately 4,400 Da. This includes the 37-amino-acid peptide backbone, the fatty acid side chain, and the C-terminal amide. The exact value depends on the specific salt and counterion.
Does cagrilintide form fibrils like human amylin?
Cagrilintide is designed to resist fibril formation. Unlike native human amylin, which readily aggregates into amyloid fibrils, cagrilintide has amino acid substitutions that disrupt beta-sheet formation. This makes it more stable for long-term use.
Is cagrilintide the same as tirzepatide or retatrutide?
No. Cagrilintide is an amylin analog, while tirzepatide is a dual GIP/GLP-1 agonist and retatrutide is a triple agonist. They target different receptors and have different structures. Cagrilintide is not FDA-approved for human use in the United States.
This page provides educational research information and does not replace medical advice, diagnosis, or treatment.