Amylin vs β-CGRP

How they're alike

Amylin and β-CGRP sit in the same peptide superfamily — the calcitonin/CGRP family — and the IUPHAR review by Hay and colleagues (2018) groups them with calcitonin, adrenomedullin, and intermedin as ligands of a small set of class B (secretin-like) GPCRs. Both peptides in this dossier are 37 amino acids long, both carry a C-terminal amide, and both close an N-terminal ring through a disulfide bridge between Cys2 and Cys7 (per the chemistry tables in each card's readme). A BLOSUM62 local alignment of the two card sequences shows 50% identity across 36 of the 37 residues, with the disulfide-ring region (CNTATC) fully conserved. At the receptor level, both peptides signal through complexes that combine a class B GPCR — the calcitonin receptor (CTR) or the related calcitonin receptor-like receptor (CLR) — with one of three receptor activity-modifying proteins (RAMP1, RAMP2, or RAMP3), and this RAMP-dependent receptor architecture is the central organizing principle of the family's pharmacology (Barwell 2012; Hay 2018). Cross-talk between the two ligands at the receptor level is well documented: splice variants of the calcitonin receptor produce amylin-receptor isoforms that "can be potently activated by CGRP," as summarized in the IUPHAR Guide to Pharmacology family entry, and the structural basis for shared peptide–receptor recognition has been examined for the two ligands together (Lee 2016, the one reference cited in both cards).

How they differ

The peptides' physiological niches are different even where their receptor systems overlap. β-CGRP is a sensory-neuron neuropeptide: Russell and colleagues (2014) describe it as a 37-amino-acid product of alternative RNA processing of the calcitonin gene, "a highly potent vasodilator" released from perivascular sensory fibers, with established roles in cardiovascular regulation, neurogenic inflammation, and pain signaling. Amylin, by contrast, is an islet hormone — Betsholtz and colleagues (1989) characterize it as a 37-residue islet amyloid polypeptide co-secreted with insulin from pancreatic beta cells, where in humans and cats (but not in common rodents) it deposits as islet amyloid in association with type 2 diabetes. The receptor preference differs accordingly: the canonical CGRP receptor is CLR paired with RAMP1, while the amylin receptors are CTR paired with RAMP1, RAMP2, or RAMP3 (the AMY₁/AMY₂/AMY₃ subtypes), per the IUPHAR family review (Hay 2018). At the sequence level, the divergence is concentrated in a specific region of the molecule that Betsholtz and colleagues (1989) identified as the determinant of inter-species differences in islet amyloid formation — the same paper that produced the Chinese hamster IAPP sequence stored on this amylin card. That region (roughly residues 20–29 in the alignment shown in the dossier) is also where amylin and β-CGRP diverge most from each other, while their shared N-terminal disulfide ring and C-terminal amidation are conserved.

A second source of divergence is the species variant captured in each card. The amylin card represents the Chinese hamster (Cricetulus griseus) IAPP sequence rather than human amylin, and Betsholtz and colleagues (1989) note that rodent IAPP sequences diverge enough from human that synthetic peptides from the divergent region behave differently in amyloid-formation assays. The β-CGRP card represents the human β isoform — distinct from α-CGRP by a small number of residues — and its readme notes that the catalog source describes the two isoforms as having "similar biological activities" without attaching primary data on potency differences between them. In other words: each card represents a particular species/isoform pick, and findings from the broader human-amylin or α-CGRP literature do not transfer to these specific sequences without additional verification.

Head-to-head clinical evidence

No head-to-head clinical trial directly comparing amylin and β-CGRP in humans is present in this dossier. The PubMed search for papers naming both peptides in the title returns a 1992 Annals of the New York Academy of Sciences review (Cooper 1992) titled "The physiology of calcitonin gene-related peptide in the islet compared with that of islet amyloid polypeptide (amylin)" — a review-level comparison rather than a controlled clinical study — and a 1999 plasma-levels report that concerns CGRP and endothelin-1 rather than amylin. Mechanistically, the closest thing to a head-to-head reference in the dossier is the Journal of Biological Chemistry paper by Lee and colleagues (2016) titled "Calcitonin and Amylin Receptor Peptide Interaction Mechanisms," which is the single shared reference between the two cards and which examines how peptide ligands of this family engage CTR-based receptors. For pharmacological context across the whole family — including direct comparisons of amylin, calcitonin, CGRP, and adrenomedullin binding profiles at CLR/CTR–RAMP combinations — the IUPHAR review (Hay 2018) and the more recent allosteric-modulator review on RAMPs (2020) are the broadest sources cited in either card. No randomized trial data and no exogenous-administration human pharmacology data are attached to either card.

Safety profile comparison

Neither card carries a clinical safety dataset. The β-CGRP readme notes "no human trial or clinical data" and "no animal experiment data" identified for exogenous β-CGRP (human) administration in the literature attached to that card; the amylin readme similarly reports "no human evidence," "no animal evidence," and "no assay evidence" identified for the Chinese hamster IAPP variant. There is, accordingly, no adverse-event comparison to draw from this dossier. The Betsholtz and colleagues (1989) paper does raise one mechanistic safety-adjacent point that distinguishes amylin from CGRP: amylin's amyloidogenic propensity is sequence-dependent and varies by species, with human IAPP forming islet amyloid in association with type 2 diabetes while rodent IAPP — including the hamster variant — does not in the assays they examined. β-CGRP has no analogous amyloid-formation literature attached to its card. Granholm and colleagues (2008) and Davey and colleagues (2008), the two bone/osteoclast-context references on the amylin card, address calcitonin-receptor biology in bone resorption rather than amylin or β-CGRP safety per se, so they are not safety data either. In short, the safety profile of both peptides as exogenous agents is unestablished in this dossier.

Indication overview

Neither peptide as represented in these two cards has an approved therapeutic indication. The β-CGRP card states explicitly that "no approved therapeutic status" is identified for β-CGRP (human) as an exogenous therapeutic agent, and notes that approved drugs in the CGRP pathway — anti-CGRP monoclonal antibodies and small-molecule receptor antagonists used for migraine — are distinct molecules whose regulatory status does not transfer to the endogenous peptide itself. The amylin card likewise records "no approved therapeutic status identified" for the Chinese hamster IAPP sequence, and does not assert any indication. The broader calcitonin/CGRP-family receptor system is described in the cited reviews (Barwell 2012; Hay 2018) as therapeutically relevant for conditions including osteoporosis, diabetes, obesity, lymphatic insufficiency, migraine, and cardiovascular disease — but those indications belong to other ligands in the family (e.g., synthetic amylin analogs, anti-CGRP antibodies, calcitonin) and to other molecular forms, not to the specific Chinese hamster IAPP or human β-CGRP sequences compared here. Readers looking for clinical context should treat both of these cards as catalog/sequence entries rather than as profiles of approved medicines.