MariTide: Molecular Structure
Chemical properties, amino acid sequence, and structural analysis
📌TL;DR
- •Molecular formula: Complex antibody-peptide conjugate
- •Molecular weight: 153514 Da
- •Half-life: Approximately 21 days (~3x longer than weekly GLP-1 agonists), enabling monthly or less frequent dosing
Amino Acid Sequence
114 amino acids
Formula
Complex antibody-peptide conjugate
Molecular Weight
153514 Da
Half-Life
Approximately 21 days (~3x longer than weekly GLP-1 agonists), enabling monthly or less frequent dosing
Molecular Structure and Properties#
MariTide (maridebart cafraglutide, AMG 133) is a first-in-class antibody-peptide conjugate with a molecular weight of 153,514 Da. It represents a fundamentally different molecular format from standard peptide-based anti-obesity therapies. Rather than being a single peptide, MariTide combines a full-length monoclonal antibody with two conjugated GLP-1 agonist peptides.
Structural Architecture#
MariTide is composed of three functional components:
- Anti-GIPR monoclonal antibody: A fully human monoclonal antibody that binds to and antagonizes the GIP receptor
- Two GLP-1 analogue peptides: GLP-1 receptor agonist peptides conjugated to the antibody
- Amino acid linkers: Connect the GLP-1 peptides to the antibody backbone
Component Details#
| Component | Function | Properties |
|---|---|---|
| Anti-GIPR antibody | GIPR antagonism | Fully human IgG, long half-life |
| GLP-1 peptides (x2) | GLP-1R agonism | Analogue peptides, conjugated |
| Linkers | Connection | Amino acid-based |
Chemical Properties#
| Property | Value |
|---|---|
| Chemical class | Antibody-peptide conjugate |
| Molecular weight | 153,514 Da (~153.5 kDa) |
| Molecular formula | Not publicly disclosed |
| CAS number | Not publicly disclosed |
| Receptor targets | GLP-1R (agonist) and GIPR (antagonist) |
| Half-life | ~21 days |
| Dosing frequency | Monthly or less frequent |
| Administration | Subcutaneous injection |
Half-Life and Dosing#
MariTide's ~21-day half-life is approximately 3 times longer than the longest-acting FDA-approved weekly medications for obesity (semaglutide and tirzepatide have half-lives of ~7 days and ~5 days, respectively). This extended half-life is derived from the antibody component, which confers the typical IgG antibody pharmacokinetic profile.
| Therapy | Half-Life | Dosing |
|---|---|---|
| MariTide | ~21 days | Monthly or less |
| Semaglutide | ~7 days | Weekly |
| Tirzepatide | ~5 days | Weekly |
| Liraglutide | ~13 hours | Daily |
Comparison with Tirzepatide#
MariTide and tirzepatide both target GLP-1R and GIPR but with opposite GIP strategies:
| Feature | MariTide | Tirzepatide |
|---|---|---|
| Format | Antibody-peptide conjugate | Acylated peptide |
| Molecular weight | ~153.5 kDa | ~4.8 kDa |
| GLP-1R | Agonism (via peptides) | Agonism |
| GIPR | Antagonism (via antibody) | Agonism (GIP-biased) |
| Half-life | ~21 days | ~5 days |
| Dosing | Monthly | Weekly |
| Developer | Amgen | Eli Lilly |
Receptor Pharmacology#
MariTide's unique mechanism:
- GLP-1 receptor: The two conjugated GLP-1 analogue peptides activate GLP-1 receptors, producing appetite suppression, insulin secretion, and gastric emptying delay
- GIP receptor: The antibody component binds to and blocks GIPR, preventing GIP-mediated signaling
A mechanistic study showed that when both GLP-1R and GIPR are expressed on the same cell, MariTide binds both receptors simultaneously, triggering receptor internalization and amplifying endosomal cAMP signaling. This dual engagement may contribute to its efficacy.
The GIP Agonism vs Antagonism Debate#
A central question in obesity pharmacology is whether GIP receptor agonism (tirzepatide) or antagonism (MariTide) is superior. Both approaches produce ~20% weight loss when combined with GLP-1 agonism. This suggests that the key effect may be modulation of GIP signaling (either direction) rather than its specific direction. Phase 3 data and potential head-to-head studies will help resolve this question.
Drug Delivery#
MariTide is expected to be delivered via a patient-friendly autoinjector device, providing a single-injection monthly administration. The subcutaneous route of administration is consistent with other antibody therapeutics.
Related Reading#
Frequently Asked Questions About MariTide
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Disclaimer: For educational purposes only. Not medical advice. Read full disclaimer