A subanalysis of primary outcomes of two distinct phase 2b/3 studies showed that the anti-calcitonin gene-related peptide (CGRP) monoclonal antibody fremanezumab has an early onset of action in decreasing migraine days and headache days of at least moderate severity in episodic migraine people and chronic migraine people respectively. Takao Takeshima et al. sought to determine fremanezumab's onset of action in Korean and Japanese people suffering from migraine.

In episodic migraine people (n = 357), both quarterly fremanezumab and monthly fremanezumab resulted in a greater decline in weekly migraine days (days/week) compared to placebo from the 1st week following initial injection and thereafter during the remainder of the study period. When compared to placebo, fremanezumab use exhibited a greater decline in headache days of at least moderate severity (days/week) in chronic migraine people (n = 571).

The proportion of people with a migraine day (episodic migraine) or headache day at least moderate severity (chronic migraine) was reduced in fremanezumab recipients when compared to placebo recipients. This effect was noted to be apparent from as early as day 2 (one day following 1st injection). Thus, the early onset of fremanezumab's effectiveness in migraine patients offers the potential to decrease barriers to adherence.