CagriSema: Molecular Structure

Molecular Structure and Properties#

CagriSema is a fixed-dose combination of two distinct acylated peptide analogs administered together in a single subcutaneous injection. The combination consists of cagrilintide (a long-acting amylin receptor agonist) and semaglutide (a long-acting GLP-1 receptor agonist), each at 2.4 mg per dose. Both peptides share a similar albumin-binding fatty acid modification strategy to achieve once-weekly dosing.

Cagrilintide Component#

Structure#

Cagrilintide is a 37-amino-acid synthetic peptide analog of human amylin (islet amyloid polypeptide, IAPP). The sequence is based on human amylin with modifications at multiple positions to improve stability, reduce amyloid aggregation potential, and enable albumin binding.

Key Structural Features#

• Cys2-Cys7 disulfide bond: Retained from native amylin; essential for receptor binding and the N-terminal loop structure
• Multiple amino acid substitutions: Modifications at several positions reduce the tendency for amyloid fibril formation, a problem that limits the stability of native amylin and pramlintide
• C18 fatty diacid at Lys1: Octadecanedioic acid conjugated at the N-terminal lysine via a linker, enabling albumin binding and a half-life of approximately 160 hours (6.7 days)
• C-terminal amidation: Retained from native amylin; required for full receptor activation

Receptor Pharmacology#

Cagrilintide is a nonselective agonist of amylin receptors (AMY1, AMY2, AMY3) and the calcitonin receptor (CTR). AMY receptors are heterodimers of the calcitonin receptor with receptor activity-modifying proteins (RAMPs). Research has shown that cagrilintide lowers body weight primarily through amylin receptors 1 and 3 (AMY1R and AMY3R) in the brainstem area postrema.

Semaglutide Component#

Structure#

Semaglutide is a 31-amino-acid peptide analog of human GLP-1(7-37) with an Aib substitution at position 2 and a C18 fatty diacid at Lys26. Its detailed molecular profile is covered in the semaglutide article.

Shared Design Principles#

Both cagrilintide and semaglutide employ C18 fatty diacid (octadecanedioic acid) modifications for albumin binding. This shared lipid modification strategy enables:

• Matched pharmacokinetics: Both peptides have approximately 7-day half-lives, supporting a single once-weekly co-administration
• Albumin binding: >99% protein binding for both components, creating circulating reservoirs
• Reduced renal clearance: Albumin-bound peptides are too large for glomerular filtration
• Stable plasma levels: Low peak-to-trough variation across the weekly dosing interval

Pharmacokinetics#

Co-Administration PK#

Phase 1 studies confirmed that co-administration of cagrilintide and semaglutide does not produce clinically meaningful pharmacokinetic interactions. Each peptide maintains its individual PK profile when administered together.

Formulation#

CagriSema is formulated as a single pre-filled pen device for subcutaneous injection, combining both peptides in one injection rather than requiring two separate injections. This co-formulation improves convenience and adherence compared to administering each component separately.

Structural Comparison with Other Combinations#

CagriSema is distinct from dual-agonist molecules like tirzepatide (which combines GIP and GLP-1 activity in a single peptide) or amycretin (which combines amylin and GLP-1 activity in a single molecule). Instead, CagriSema is a physical combination of two separate peptides:

The co-administration approach allows independent dose optimization of each component and leverages existing well-characterized peptides, while single-molecule approaches offer potentially simpler manufacturing and pharmacokinetics.

Related Reading#

• CagriSema overview and research guide
• Peptides similar to CagriSema
• CagriSema research evidence