Migraine-receptor blocker (alpha-CGRP 8-37, rat fragment)
A synthetic peptide fragment that blocks the receptor linked to migraine headaches; used only as a lab research tool, not an approved drug.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Alpha-CGRP(8-37) is a 30-amino acid synthetic peptide that blocks the CGRP receptor — the molecular target responsible for the vasodilation and nerve signaling that underlies migraine headaches. It is a research tool compound, not a therapeutic agent. The stored sequence (VTHRLAGLLSRSGGVVKDNFVPTNVGSEAF) is the C-terminal 30 residues of rat alpha-calcitonin gene-related peptide (alpha-CGRP, residues 8–37 of the full 37-residue peptide); it lacks the N-terminal seven residues that form a Cys²–Cys⁷ disulfide-bonded ring — the structural feature required for receptor activation. Without that ring, the peptide can occupy the CGRP receptor without switching it on, making it a competitive antagonist rather than an agonist. The human version of this fragment differs at position 35 of full alpha-CGRP (Glu in rat, Lys in human), so the stored sequence is specifically the rat form.
Alpha-CGRP itself is co-produced with calcitonin from the same gene (CALCA) by tissue-specific alternative RNA splicing: thyroid C-cells splice the transcript to make calcitonin, while neurons splice it to make CGRP — one of the first examples of a single gene producing two functionally distinct peptides. The CGRP receptor is a heterodimeric class B GPCR consisting of CLR (calcitonin receptor-like receptor) and RAMP1 (receptor activity-modifying protein 1); CLR alone is pharmacologically silent and requires RAMP1 to reach the cell surface and bind CGRP (Hay et al. 2018; Barwell et al. 2012).
History
CGRP was discovered in 1982–1983 through molecular biology rather than classical biochemistry. Rosenfeld and colleagues at the Salk Institute found that the human calcitonin gene (CALCA) produces two distinct mRNAs by alternative RNA splicing: the exon-4-including transcript produces calcitonin in thyroid C-cells, while an exon-5-including transcript produces CGRP in neurons. This was one of the first demonstrations of tissue-specific alternative splicing generating functionally distinct proteins from a single gene, and the resulting 37-amino acid peptide (CGRP) had no known function at the time of its prediction. Human CGRP was subsequently isolated and its sequence confirmed.
The CGRP receptor's molecular identity resisted standard cloning approaches for years because it required co-expression of two proteins, CLR and RAMP1, to reconstitute activity. The discovery of RAMPs by McLatchie and colleagues in 1998 resolved this: RAMP1 is required for CLR to reach the plasma membrane and to configure the binding site for CGRP rather than adrenomedullin. This finding explained the earlier pharmacological characterization by establishing the molecular receptor complex that alpha-CGRP(8-37) targets (Barwell et al. 2012).
Alpha-CGRP(8-37) was developed as a pharmacological tool in the early 1990s by probing structure-activity relationships of CGRP: removing the N-terminal seven residues including the Cys²–Cys⁷ disulfide ring yielded a fragment that competitively blocked CGRP-induced vasodilation in isolated tissue preparations without itself producing vasodilation. It became the standard pharmacological probe for attributing biological responses to the CGRP receptor — preceding the small-molecule and antibody CGRP antagonists by approximately two decades.
The therapeutic relevance of CGRP receptor antagonism was established in part through work demonstrating that intravenous CGRP infusion provokes migraine attacks in susceptible individuals, and that CGRP levels rise in jugular venous blood during spontaneous migraine attacks. These findings — supported by mechanistic experiments using alpha-CGRP(8-37) in dural vasculature models — provided the pharmacological rationale for developing clinical CGRP antagonists. Small-molecule gepants (rimegepant, ubrogepant, atogepant) and monoclonal antibodies targeting CGRP or CLR/RAMP1 (erenumab, fremanezumab, galcanezumab, eptinezumab) have since received regulatory approval for migraine treatment and prevention, representing the clinical translation of biology first probed with alpha-CGRP(8-37).
What it does
Competitive antagonism at CLR/RAMP1 (CGRP receptor): Alpha-CGRP(8-37) competes with full-length CGRP for binding to the CLR/RAMP1 receptor complex. It binds with lower affinity than full-length CGRP — because the N-terminal ring is absent — but at sufficient concentrations, it occupies the receptor and blocks CGRP-induced Gs signaling (cAMP elevation), vasodilation, and neuropeptide co-release effects. In isolated vascular preparations such as rat mesenteric arteries and dural blood vessels, alpha-CGRP(8-37) antagonizes CGRP-induced vasodilation in a concentration-dependent manner, which was the original assay system in which it was characterized.
CGRP receptor pharmacology dissection: Alpha-CGRP(8-37) has been used to distinguish CLR/RAMP1 (CGRP receptor)-mediated effects from CALCR/RAMP1 (amylin receptor, AMY1R)-mediated effects. CGRP shows cross-reactivity at amylin receptors because CLR is structurally related to CALCR and both can associate with RAMP1. The affinity of alpha-CGRP(8-37) at amylin receptors differs from its affinity at the CGRP receptor, providing a pharmacological tool for receptor subtype attribution in systems where CGRP acts on multiple receptor complexes — relevant in pancreatic islets and in bone, where calcitonin, amylin, and CGRP receptor systems overlap (Hay et al. 2018).
Migraine neurovascular pharmacology: In dural vasculature models relevant to migraine pathophysiology, alpha-CGRP(8-37) inhibits trigeminal nerve-stimulation-induced vasodilation and blocks exogenously applied CGRP. These experiments in rat and cat models established the causal role of endogenous CGRP in trigemino-vascular activation — the proposed peripheral component of migraine. Alpha-CGRP(8-37) provided early mechanistic evidence that antagonizing the CGRP receptor could interrupt this pathway, preceding and motivating the development of clinical CGRP receptor antagonists.
RAMP1-dependent receptor selectivity: Because CLR requires RAMP1 to form the CGRP receptor, alpha-CGRP(8-37) is selective for CLR/RAMP1 over CLR/RAMP2 (the AM1 receptor). RAMP1 converts CLR's binding preference from adrenomedullin to CGRP — a receptor-subtype switch controlled by which RAMP is present. This selectivity makes alpha-CGRP(8-37) useful for characterizing RAMP1-specific CLR pharmacology in mixed-RAMP expression systems (Advances in Pharmacology 2020).
Evidence
- Human: No registered clinical trials for alpha-CGRP(8-37) as an intervention. The peptide is used exclusively as a research tool compound in pharmacological and mechanistic studies; it has not entered human clinical development. Clinical translation of CGRP receptor antagonism has occurred through gepants (rimegepant, ubrogepant, atogepant — FDA-approved for migraine) and monoclonal antibodies (erenumab, fremanezumab, galcanezumab, eptinezumab — FDA-approved for migraine prevention), which descend mechanistically from the biology established with alpha-CGRP(8-37) but are distinct molecular entities.
- In vitro / ex vivo: Hay and colleagues (2018) provided an IUPHAR consensus review of the calcitonin/CGRP receptor family — covering receptor nomenclature, molecular composition (CLR/RAMP1 = CGRP receptor; CLR/RAMP2 = AM1 receptor; CALCR/RAMP1 = AMY1 receptor), ligand pharmacology, and allosteric roles of RAMPs — and characterized alpha-CGRP(8-37) as the prototypic CGRP receptor-selective competitive antagonist peptide with defined affinity at CLR/RAMP1 and selectivity relative to calcitonin receptor complexes (Hay et al. 2018). Barwell and colleagues (2012) characterized the molecular basis of CLR function, explaining how RAMP1 converts CLR from an adrenomedullin-responsive receptor to a CGRP-responsive receptor, and established the framework for understanding why alpha-CGRP(8-37) binds without activating — the C-terminal region of CGRP provides binding affinity while the N-terminal ring provides the agonist trigger (Barwell et al. 2012). The allosteric role of RAMPs in determining receptor pharmacological identity and RAMP1-dependent selectivity of alpha-CGRP(8-37) was further characterized in a dedicated RAMP pharmacology review (Advances in Pharmacology 2020).
Myths and misconceptions
- "Alpha-CGRP(8-37) targets the calcitonin receptor (CALCR)." Alpha-CGRP(8-37) is an antagonist primarily at the CGRP receptor — the CLR/RAMP1 heterodimer. The calcitonin receptor (CALCR) is a distinct protein that associates with RAMP1, RAMP2, or RAMP3 to form amylin receptor subtypes. While alpha-CGRP(8-37) shows some cross-reactivity at amylin receptors (CALCR-based complexes) due to structural family similarity, its primary pharmacological use is for CLR/RAMP1 blockade. Misidentifying the target as CALCR rather than CLR leads to incorrect mechanistic interpretation of experimental results.
- "Rat and human alpha-CGRP(8-37) are identical and interchangeable in pharmacological studies." The stored sequence is rat alpha-CGRP(8-37), which differs from human alpha-CGRP(8-37) at position 35 of the 37-residue full sequence (Glu in rat, Lys in human). While this single-residue difference does not dramatically alter receptor binding affinity, pharmacological constants measured with rat alpha-CGRP(8-37) may differ quantitatively from those obtained with the human peptide. Studies comparing CGRP receptor pharmacology across species or using rat versus human analogs should account for this.
- "CGRP receptor antagonism with peptide tools like alpha-CGRP(8-37) directly predicts efficacy of clinical anti-CGRP therapies." The gepants and anti-CGRP monoclonal antibodies target the same receptor-ligand interaction that alpha-CGRP(8-37) probes. However, quantitative translation from peptide tool experiments to clinical outcomes is indirect: alpha-CGRP(8-37) has short half-life, poor CNS penetration, and no oral bioavailability — all of which are overcome in clinical agents (gepants designed for CNS penetration; monoclonal antibodies with weeks-long half-life). The mechanistic insight from alpha-CGRP(8-37) experiments informed clinical development, but the peptide's pharmacokinetics do not model the clinical drugs.
Common questions
Q: Why does removing the N-terminal ring of CGRP (generating alpha-CGRP[8-37]) convert an agonist into an antagonist? A: Full-length CGRP agonism requires two components: the C-terminal region (retained in alpha-CGRP[8-37]) binds to the CLR/RAMP1 extracellular domain, docking the peptide; the N-terminal ring structure (Cys²–Cys⁷ disulfide loop) then inserts into the receptor's transmembrane bundle and triggers the conformational change that activates Gs signaling. This two-step mechanism is common across class B GPCRs — the C-terminus provides binding affinity, the N-terminus provides agonist activity. Alpha-CGRP(8-37) retains the C-terminal binding contact but lacks the N-terminal activating trigger, resulting in a molecule that occupies the receptor without activating it.
Q: How did alpha-CGRP(8-37) contribute to developing clinical migraine treatments? A: Developing anti-CGRP therapies required demonstrating that CGRP is causally involved in migraine, not merely a correlate. Experiments with alpha-CGRP(8-37) in isolated dural vessel preparations showed that CGRP receptor antagonism blocked trigeminal stimulation-induced vasodilation, implicating the CGRP/CLR-RAMP1 axis in the neurogenic inflammation pathway proposed to underlie migraine. Combined with clinical observations (CGRP levels rise during migraine attacks; CGRP infusion provokes migraine), these mechanistic pharmacology experiments provided the dual experimental-clinical basis that justified pharmaceutical investment in gepants and anti-CGRP antibodies.
Q: What is the difference between alpha-CGRP and beta-CGRP? A: Alpha-CGRP and beta-CGRP are distinct peptides encoded by different genes: alpha-CGRP from CALCA (the calcitonin gene), beta-CGRP from CALCB. Both are 37 amino acids and differ by only 3 residues. Both activate the CLR/RAMP1 CGRP receptor with comparable potency and are vasodilatory neuropeptides expressed in sensory neurons. Alpha-CGRP is the predominant form in the trigeminal ganglia and perivascular sensory nerve terminals relevant to migraine; beta-CGRP is expressed more in enteric neurons. Clinical anti-CGRP antibodies target both forms. The stored card sequence is specifically rat alpha-CGRP(8-37).
Related peptides
- Peptide YY — Peptide YY: another gut peptide where N-terminal truncation (PYY[3-36] vs PYY[1-36]) creates a pharmacologically distinct variant with altered receptor selectivity — a parallel to alpha-CGRP(8-37)'s conversion from agonist (full CGRP) to antagonist by N-terminal truncation
- Corticotropin — ACTH/Corticotropin: illustrates how prohormone processing and N-terminal truncation can profoundly alter receptor pharmacology, converting full agonists into partial agonists or antagonists, as occurs in the calcitonin/CGRP receptor family context
- ACTH (7–39) — ACTH(7-39): a direct structural parallel — just as ACTH(7-39) loses the N-terminal pharmacophore residues of full ACTH to become a partial agonist/antagonist, alpha-CGRP(8-37) loses the N-terminal Cys²–Cys⁷ ring of CGRP to become an antagonist
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does this peptide shut down all receptor activity, or only some of it?
If true, researchers would understand why this tool peptide and clinical migraine drugs give different results in experiments. For drug developers, this could reveal new ways to fine-tune receptor blockade for better migraine treatment with fewer side effects.
Can scientists attach longer-lasting or targeting tags to this peptide without destroying its blocking ability?
If true, this peptide could be upgraded from a lab tool into a real drug candidate more quickly. For biotech companies, having a proven safe spot for modifications would cut years off development time for new migraine therapies.
Does this peptide block more than just the CGRP receptor?
If true, scientists would need to reconsider what past experiments actually measured. For migraine drug developers, knowing whether a tool compound is truly selective would improve confidence in early research findings before investing in clinical candidates.
Does the rat version last longer in the body than the human version would?
If true, researchers would know that rat experiments exaggerate how long the drug lasts in people. For migraine drug developers, this would mean building human-specific versions earlier in the pipeline to avoid surprises in clinical trials.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.6442910432815552 | openfold3-mlx |
| ranking score | 0.7807592153549194 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.950 | global PDE — lower = better |
| disorder | 0.262 | fraction disordered |
| chain pair ipTM (A, B) | 0.644 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | aedd8f3eb814e392… |
| hardware | apple_m4_base_16gb |
| mlx version | 0.31.1 |
| python | 3.14.3 |
| random seed | 42 |
| msa strategy | colabfold |
| diffusion samples | 1 |
| runtime | 445s |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
python3 openfold3/run_openfold.py predict --query_json {query.json} --runner_yaml examples/example_runner_yamls/mlx_runner.yml --output_dir {output_dir} --num_diffusion_samples 1 ▸citationbibtex
@peptide{pep10683,
sequence = {VTHRLAGLLSRSGGVVKDNFVPTNVGSEAF},
target = {calcr},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}