Salivary CGRP and Erenumab Treatment Response: Towards Precision Medicine in Migraine

Objective We aimed (1) to analyze salivary calcitonin gene-related peptide (CGRP) levels in patients with migraine, (2) to predict erenumab response from baseline CGRP levels, and (3) to evaluate CGRP change post-treatment. Methods This is a prospective observational study that measured salivary CGRP levels in healthy controls (HCs), patients with episodic migraine (EM) and patients with chronic migraine (CM). Participants collected saliva samples at baseline and, the patients who were candidates to receive erenumab, also collected saliva after 3 doses of treatment. We quantified CGRP-like immunoreactivity (CGRP-LI) by enzyme-linked immunosorbent assay (ELISA) and we performed an analysis at baseline and post-treatment through generalized linear mixed models. Results At baseline, a higher headache frequency was associated with higher CGRP levels, those being even higher in the presence of depressive symptoms. A cutoff point (mean, 95% confidence interval [CI]) of 103.93 (95% CI = 103.35-104.51) pg/ml was estimated to differentiate migraine from controls with an area under the receiver operating characteristic (ROC) curve (AUC, 95% CI) of 0.801 (95% CI = 0.798-0.804). We also found that higher pretreatment salivary CGRP levels were statistically significantly associated to a higher probability of having 50% or greater reduction in headache frequency in patients with EM, but not in patients with CM. After 12 weeks of treatment with erenumab, salivary CGRP levels from patients within all spectrum of migraine frequency converged to similar CGRP values. In contrast, in patients with concomitant depressive symptoms, this convergence did not happen. Interpretation Patients with migraine not only have higher CGRP levels compared with HCs, but also the presence of depressive symptoms seems to increase salivary CGRP levels and we have evidence, for the first time, that baseline salivary CGRP concentration is associated with treatment response to erenumab. ANN NEUROL 2022