Meta-regression
A meta-regression was conducted for placebo response, with the percentage of patients with ≥2 treatment failures as a covariate for both episodic and chronic migraine for SC trials. This step was intended to assess whether the percentage of patients with ≥2 treatment failures was significant and whether the coefficient estimate was similar between two types of migraine across several SC trials. A similar assessment was not feasible for IV trials, as there was only one trial for episodic migraine and one trial for chronic migraine. Consequently, we conducted a meta-regression including placebo data from all the anti-CGRP (SC and IV) clinical trials identified in the systematic literature review to understand the impact on placebo MMD response of the following variables: type of migraine (episodic or chronic), percentage of patients with ≥2 prior treatment failures in each trial, and the route of administration for treatment (i.e., SC or IV). To assess whether the route of administration impacted MMD reduction in the placebo arms differently in episodic or chronic migraine, an interaction term between the route of administration and type of migraine was introduced into the meta-regression. Finally, we assessed whether the IV effect differed between episodic and chronic migraine.