Serum Alpha and Beta‐CGRP Levels in Chronic Migraine Patients Before and After Monoclonal Antibodies Against CGRP or its Receptor

OBJECTIVE: The objective of this study was to analyze the evolution of alpha and beta-CGRP circulating levels throughout CGRP monoclonal antibodies (mAbs) treatment in patients with chronic migraine (CM). METHODS: We recruited patients with CM beginning mAbs along with sex and age paired healthy controls (HCs). Blood was extracted before, 2 weeks (M0.5) and 3 months (M3) after the first dose of mAbs, always in free-migraine periods, and once for HCs. Alpha and beta-CGRP serum levels were measured using enzyme-linked immunosorbent assays (ELISAs) specific for each isoform. RESULTS: Baseline alpha-CGRP levels were significantly elevated in 103 patients with CM (median = 50.3, 95% confidence interval [CI] = 40.5-57.0 pg/ml) compared to 78 HCs (median = 37.5, 95% CI = 33.9-45.0 pg/ml; 95% CI of differences = 2.85-17.08 pg/ml) and significantly decreased (n = 96) over the course of mAb treatment (M0.5: median = 40.4, 95% CI = 35.6-48.2 pg/ml; and M3: median = 40.9, 95% CI = 36.3-45.9 pg/ml). Absolute decrease of alpha-CGRP throughout the treatment positively correlated with the decrease in MMDs. Negative modulation of alpha-CGRP significantly associated with positive scores at the Patient Global Impression of Change scale and with analgesic overuse reversal. Beta-CGRP did not differ at baseline between patients with CM (median = 4.2, 95% CI = 3.0-4.8 pg/ml) and HCs (median = 4.4, 95% CI = 3.4-5.6 pg/ml; -1.09 to 0.60) nor was modulated by mAb treatment (n = 96; M0.5: median = 4.5, 95% CI = 3.5-5.2 pg/ml; and M3: median = 4.6, 95% CI = 3.7-5.2 pg/ml). INTERPRETATION: Treatment with mAbs, regardless of its target, is able to progressively normalize basally increased alpha-CGRP levels in CM and this effect correlates with efficacy measures, which supports a role of this neuropeptide as the first CM biomarker. ANN NEUROL 2023;94:285-294.