Why does amylin co-agonism add to a GLP-1 effect rather than duplicate it?

I am asking mechanistically rather than practically — I want the model, not the protocol.

I can predict the outcome but I cannot explain it, which means I will get the next case wrong.

I would like to know how confident the field actually is about this.

Can someone derive this rather than assert it?

The short version: satiation rather than appetite suppression, mediated centrally, with a receptor built from calcitonin receptor plus a modifying protein.

The amylin receptor is not a single gene product: it is the calcitonin receptor in complex with one of the receptor-activity-modifying proteins, and the identity of that protein determines the pharmacology. That is why selective agonism is a hard medicinal-chemistry problem.

Amylin acts at the area postrema, the same circumventricular region implicated in incretin-mediated nausea, which is why the tolerability profiles overlap even though the receptors do not.

Pramlintide is the long-established amylin analogue and its three proline substitutions are the textbook solution to the aggregation problem.

The caveat is that combination pharmacology multiplies the tolerability questions as well as the efficacy, and the trials are the place those get answered.

The aggregation problem explains the sequence changes in every amylin analogue.

edited 15 Dec 2025 by harriet_lonsdale — removed a claim I could not source