The introduction of the CGRP mAbs migraine prevention therapies five years ago has seen a decrease in prescriptions of older oral preventive therapies such as antiseizure, antihypertensive, and antidepressant medications, according to a US study.

A retrospective study comprised de-identified data from 6,595 patients treated at the Stanford Headache Clinic, California across pre-CGRP mAb years of 2015-2017 and post-approval years of 2019-2021.

Erenumab was the first CGRP mAb to be FDA-approved in May 2018 followed by fremanezumab in Sept 2018, which did not have wide uptake, galcanezumab in Sept 2018 then eptinezumab in February 2020.

The study, published in the journal Headache [link here] found 15.7% of patients were prescribed any one of the four CGRP mAbs during 2019-2021.

As well, they reported a statistically significant decrease in the proportion of patients receiving any of the previous top 10 most prescribed preventive medications for migraine after the introduction of the CGRP mAbs (46.3% v 43.1%; p=0.001).

In particular, statistically significant decreases were seen for amitriptyline and nortriptyline, valproate, duloxetine, memantine, onabotA, propranolol, and verapamil.

There was no statistically significant change in venlafaxine or gabapentin prescriptions.

The investigators said it was not unexpected that the CGRP mAbs would divert patients away from a second or third oral medication.

“Future work should continue to observe how the prescription patterns of CGRP mAbs evolves over time, including if the step therapy requirement for prior use of two oral therapies before initiation were to disappear and the CGRP mAbs could compete as first- line medication.”

In exploring the uptake of the new medications, they said comparative meta-analyses have suggested that CGRP mAbs have similar efficacy not only to each other, but also to the oral preventive medications.

“While the CGRP mAbs do not exhibit superior efficacy relative to the oral preventives and onabotA, they do appear to have a more tolerable side effect profile to the oral preventives,” they said.

“Topiramate and the tricyclic antidepressants, for example, are well known for their side effects, which can often limit their use, regardless of their efficacy.”

They noted that because of the favourable side effect profile there appeared to be greater adherence to CGRP mAbs which in turn “leads to an overall decrease in burden of migraine.”

“Yet, this substitution from the oral preventives to the CGRP mAbs carries a potentially large economic cost. For instance, a 1-year supply of galcanezumab can cost up to $10,000, while a year of propranolol only costs $1400,” they said.

“Extrapolated to the national scale, widespread usage of these medications has the potential to add exorbitant costs to the health-care system compared to their cheaper predecessors.”