Calcitonin Gene-Related Peptide in Migraine

Calcitonin gene-related peptide (CGRP) is a 37-amino-acid neuropeptide that functions as a potent vasodilator and pain mediator within the trigeminovascular system. Substantial evidence implicates CGRP as a central driver of migraine pathophysiology, making it a validated therapeutic target.

Role in Migraine Pathophysiology

During a migraine attack, trigeminal nerve activation releases CGRP from perivascular afferents, causing meningeal vasodilation, plasma protein extravasation, and mast cell degranulation. Elevated CGRP levels have been measured in jugular venous blood during spontaneous and provoked migraine attacks. CGRP activates receptor complexes composed of calcitonin-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1), expressed on vascular smooth muscle, endothelial cells, and trigeminal neurons.

Monoclonal Antibody Therapies

Four monoclonal antibodies targeting the CGRP pathway have achieved regulatory approval. Erenumab binds the CGRP receptor CLR subunit, while fremanezumab, galcanezumab, and eptinezumab bind the CGRP ligand itself. These antibodies demonstrate sustained target engagement over weeks to months, supporting once-monthly or once-quarterly dosing. Phase 3 trials demonstrate reductions of 50% or more in monthly migraine days for approximately 50% of treated patients.

Gepants

Small-molecule CGRP receptor antagonists, termed gepants, offer oral administration and shorter half-lives suitable for acute migraine treatment. Ubrogepant, rimegepant, and atogepant have received FDA approval. Ubrogepant and rimegepant serve as acute treatments, while atogepant is approved for preventive use. Gepants competitively block CGRP binding to CLR/RAMP1 without the immunogenicity concerns associated with biologic therapies.

Emerging Applications

CGRP-targeted therapies are being investigated for cluster headache, post-traumatic headache, and fibromyalgia. Combination strategies pairing monoclonal antibodies with gepants may address patients with inadequate response to monotherapy. Understanding of CGRP-independent migraine pathways continues to expand therapeutic possibilities.