CGRP

A 37-amino-acid sensory neuropeptide and one of the most potent vasodilators described in humans; every FDA-approved drug in this space blocks CGRP rather than supplying it, and the peptide itself has no approved product.

Also referenced as: Calcitonin Gene-Related Peptide, Calcitonin Gene Related Peptide, alpha-CGRP, α-CGRP, hα-CGRP, Human Alpha CGRP, CGRP (1-37)

Also appears in: Cardiovascular

What is CGRP?

Calcitonin gene-related peptide is a 37-residue neuropeptide produced by alternative processing of the primary RNA transcript of the calcitonin gene — the same gene that encodes calcitonin, spliced differently in neurons than in thyroid C cells (Amara et al., Nature, 1982, 298(5871):240–244; Rosenfeld et al., Nature, 1983, 304(5922):129–135). The molecule carries an N-terminal ring closed by a disulfide bridge between Cys2 and Cys7, an alpha-helical midsection, and an amidated C-terminal phenylalanine; opening that ring abolishes receptor activation, which is why the linear derivatives are sold as separate, non-agonist reagents. Humans make two closely related forms — alpha-CGRP from the CALCA gene and beta-CGRP from the adjacent CALCB gene, differing at three positions — and both are stored in and released from sensory and perivascular nerve fibers (Russell et al., Physiological Reviews, 2014, 94(4):1099–1142).

Its position in the research-compound market is unusual, and it is worth stating plainly: CGRP is the target of eight FDA-approved migraine drugs, and none of those drugs contain CGRP. Four are antibodies against the peptide or its receptor and four are small-molecule receptor antagonists. There is no approved product that supplies CGRP. The peptide itself circulates in catalogs as an analytical and receptor-assay reference reagent, and appears in the clinic only as an experimental infusion used to provoke headache under a research protocol. Most consumer-facing interest in the term “CGRP” is really interest in the drugs that block it.

How it works

• The receptor is a three-protein assembly, not a single GPCR — the calcitonin receptor-like receptor (CLR) only becomes a CGRP receptor when it is chaperoned to the surface by receptor activity-modifying protein 1; pairing the same CLR with RAMP2 or RAMP3 produces adrenomedullin receptors instead (McLatchie et al., Nature, 1998, 393(6683):333–339). A separate intracellular receptor component protein is required for efficient signal transduction at the complex (Evans et al., Journal of Biological Chemistry, 2000, 275(40):31438–31443), and the assembled, agonist-bound, Gs-coupled complex has since been resolved by cryo-electron microscopy (Liang et al., Nature, 2018, 561(7724):492–497)
• Vasodilation runs through cAMP and potassium channels — receptor occupancy raises cAMP and opens ATP-sensitive potassium channels in arterial smooth muscle, hyperpolarizing the cell and relaxing the vessel; in some beds an endothelium-dependent component contributes as well (Nelson et al., Nature, 1990, 344(6268):770–773; Brain & Grant, Physiological Reviews, 2004, 84(3):903–934)
• The potency is the headline finding — intradermal CGRP in femtomole doses induces microvascular dilatation and increased blood flow (measured in the rabbit by ¹³³Xe clearance), while in human skin the same injections produce persistent local reddening (Brain et al., Nature, 1985, 313(5997):54–56). Infusing human CGRP into six volunteers dropped diastolic pressure from 64 to 55 mmHg while heart rate rose from 61 to 87 beats/min, leading the authors to describe it as more potent than any other vasodilator then known (Struthers et al., Clinical Science, 1986, 70(4):389–393)
• In sensory nerves it is a nociceptive signal, not just a vascular one — CGRP is concentrated in trigeminal fibers innervating cranial vessels, and levels rise in external jugular but not cubital venous blood during migraine attacks, while the other vasoactive neuropeptides measured at the same time — neuropeptide Y, vasoactive intestinal polypeptide, and substance P — do not change (Goadsby et al., Annals of Neurology, 1990, 28(2):183–187)

Two pharmacological details shape everything downstream. First, CGRP is cleared fast: when synthetic CGRP was infused into humans, immunoreactive peptide disappeared bi-exponentially with a fast-phase plasma half-life of 6.9 ± 0.9 minutes and a slow phase of 26.4 ± 4.7 minutes (Kraenzlin et al., Regulatory Peptides, 1985, 10(2–3):189–197 — rat-sequence CGRP). Second, the receptor family is promiscuous — CGRP also activates the AMY1 amylin receptor built from the calcitonin receptor plus the same RAMP1 subunit (Cao et al., Biochemistry, 2024, 63(9):1089–1096), which is why the amylin analog pramlintide provokes migraine-like attacks much as CGRP does (Ghanizada et al., Annals of Neurology, 2021, 89(6):1157–1171).

Research status

The evidence base splits cleanly in two. Blocking CGRP is one of the better-documented successes in modern neurology. Administering CGRP has almost no therapeutic literature at all.

What human infusion actually does. A systematic review of intravenous human alpha-CGRP pooled 11 studies covering 61 healthy participants and 177 people with migraine: flushing occurred in 99% and a warm sensation in 97%, palpitations in 63%, heart rate rose 14–58%, mean arterial pressure fell 7–12%, superficial temporal artery diameter increased 41–43%, and middle cerebral artery mean flow velocity fell 9.5–21%, with the vascular changes lasting from 20 minutes to more than 2 hours. The authors reported universal vasodilation without serious adverse events (Al-Karagholi et al., Frontiers in Neurology, 2023, 14:1204734).

It reliably provokes headache. In a double-blind crossover study, human alpha-CGRP at 2 µg/min for 20 minutes was given to 12 patients with migraine without aura. Three were excluded — two for severe hypotension and one for an intercurrent infection. Over the following 11 hours every remaining participant developed headache after CGRP versus one after placebo (P = 0.0004), and in three the delayed headache met formal diagnostic criteria for migraine without aura (Lassen et al., Cephalalgia, 2002, 22(1):54–61). This is the basis for the provocation model, and it is also a documented harm.

The one therapeutic trial of CGRP itself. Ten patients with severe Raynaud’s phenomenon secondary to connective tissue disease were randomized to intravenous CGRP (0.6 µg/min for 3 hours daily over 5 days) or saline. Hand blood flow rose to a median 179% of baseline versus 102% with saline, and all ulcers healed in four of five CGRP-treated patients versus none on saline (Bunker et al., The Lancet, 1993, 342(8863):80–83). The result was never developed into an approved product; a peptide with a several-minute half-life that must be infused for hours is a difficult drug. Earlier human work using rat-sequence CGRP had also shown that low-dose infusion suppresses pentagastrin-stimulated gastric acid output by 29% and lowers circulating gastrin, gastric inhibitory peptide, enteroglucagon, and neurotensin — an effect that outlasted the infusion (Kraenzlin et al., Regulatory Peptides, 1985).

Blocking CGRP: proof of concept, one failure, then approvals. The intravenous antagonist olcegepant (BIBN 4096 BS) was tested in 126 patients with acute migraine; the selected 2.5 mg dose produced a 66% response rate versus 27% for placebo (Olesen et al., New England Journal of Medicine, 2004, 350(11):1104–1110). The first oral follow-on failed on safety, not efficacy: a 12-week prevention trial of telcagepant was halted on its safety monitoring board’s recommendation over hepatotoxicity concerns, with 660 patients randomized at termination and 13 — all in the telcagepant arms — showing alanine aminotransferase elevations at least 3× the upper limit of normal, 7 of them with matching aspartate aminotransferase elevations (Ho et al., Neurology, 2014, 83(11):958–966). A related compound, MK-3207, was abandoned over the same concern, and ubrogepant was subsequently selected for structural modifications making it less prone to forming the reactive metabolites implicated in both (Smith et al., Toxicological Sciences, 2020, 177(1):84–93). The antibody route then worked: erenumab, which binds the receptor, cut monthly migraine days by 3.2 (70 mg) and 3.7 (140 mg) versus 1.8 on placebo across 955 randomized patients (Goadsby et al., New England Journal of Medicine, 2017, 377(22):2123–2132). FDA approvals followed for erenumab (May 17, 2018), fremanezumab (September 14, 2018), galcanezumab (September 27, 2018), eptinezumab (February 21, 2020), and for the next-generation oral and nasal antagonists ubrogepant (December 23, 2019), rimegepant (February 27, 2020), atogepant (September 28, 2021), and zavegepant (March 9, 2023).

Registry picture. A ClinicalTrials.gov search on interventions named for calcitonin gene-related peptide returns roughly 150 records as of August 2026, but the overwhelming majority are trials of the antibodies and gepants, or observational studies measuring CGRP as a biomarker. Narrow it to studies that actually administer the peptide and the count falls to about a dozen, all mechanistic provocation work: headache induction in familial hemiplegic migraine (NCT00358839, NCT00687947), functional MRI during CGRP-induced attacks (NCT00363532, NCT03143465), sumatriptan tested against CGRP-induced headache (NCT03542357), post-traumatic headache pathophysiology (NCT03791515), and attack induction in migraine with aura (NCT07021859). No registered trial tests exogenous CGRP for recovery, body composition, cardiovascular performance, longevity, or any other indication that drives research-peptide demand.

Common dosage forms

• Research-grade lyophilized peptide — human alpha-CGRP, most often supplied as the trifluoroacetate salt in sub-milligram to low-milligram quantities for receptor binding, immunoassay calibration, and tissue-bath work. Human beta-CGRP and rat CGRP are stocked as separate items because their sequences differ, and species mismatch matters in assay work.
• Fragments and analogs — the truncated CGRP(8–37) antagonist fragment, linear Cys(Acm)2,7 derivatives, and biotinylated or radiolabeled versions exist as distinct reagents. These are not CGRP and behave differently; CGRP(8–37) blocks the receptor rather than activating it.
• Assay kits — ELISA and radioimmunoassay kits that measure CGRP in plasma or tissue are a separate product class from the peptide itself and are often what a catalog listing actually refers to.
• No approved human product in any format. Every clinical administration in the literature has been an intravenous infusion prepared under a research protocol and dosed in micrograms per minute, not as a fixed-strength vial. The peptide is not orally bioavailable.
• What pharmacies actually stock is the opposite pharmacology — oral tablets and orally disintegrating tablets (ubrogepant, rimegepant, atogepant), a nasal spray (zavegepant), subcutaneous autoinjectors and prefilled syringes (erenumab, fremanezumab, galcanezumab), and an intravenous infusion (eptinezumab). All are antagonists.

Key considerations

• The naming trap is the main hazard here. In consumer conversation “CGRP” almost always means the anti-CGRP drug class, not the peptide. Related confusions worth separating: alpha- versus beta-CGRP; CGRP(8–37), an antagonist fragment; calcitonin, a different peptide made from the same gene by a different splice; procalcitonin, the calcitonin prohormone used as a sepsis biomarker, which is a separate molecule and dominates naive database searches on the calcitonin family; and adrenomedullin and amylin, which share receptor components with CGRP but are distinct peptides.
• Regulatory status is unambiguous. No FDA-approved product contains CGRP, and no compounding pathway supplies it. Its only established human roles are as a laboratory reagent and as an investigational provocation agent.
• The documented human effects are cardiovascular and unpleasant. Near-universal flushing and warm sensation, tachycardia of 14–58%, and a 7–12% drop in mean arterial pressure are the expected response to infusion, and one provocation study excluded 2 of 12 participants for severe hypotension. In people prone to migraine, CGRP reliably triggers attacks — that is the whole point of the provocation model.
• Blocking CGRP produces vascular signals in the other direction, which is informative but not a rationale. The erenumab label carries warnings for hypertension, Raynaud’s phenomenon, and constipation with serious complications. That tells you CGRP has a tonic physiological role in vascular tone and gut motility; it does not establish that administering CGRP is beneficial for anything.
• The core evidence gap is delivery. A fast-phase plasma half-life near 7 minutes means any effect is confined to the infusion window, which is why the one positive therapeutic result — five days of multi-hour infusions in Raynaud’s phenomenon, published in 1993 — never became a product. Engineering a long-acting CGRP agonist remains an unsolved problem, not an available one.