Galcanezumab, a calcitonin gene-related peptide (CGRP) antagonist, is the first agent to receive FDA approval for the treatment of cluster headaches. The product was accorded a priority review in March and a ruling had been expected later this year. Galcanezumab is marketed as Emgality in the U.S. and received approval for the prevention of migraine last year. It is the third CGRP-targeted monoclonal antibody for migraine prophylaxis after erenumab (Aimovig) and fremanezumab (Ajovy). Aimovig, which uniquely targets the CGRP receptor, has also received approval by Health Canada for migraine prevention.
The label extension for galcanezumab was based on the results of a placebo-controlled study of 106 patients with episodic or chronic cluster headache, according to an FDA media release. Galcanezumab-treated patients experienced 8.7 fewer cluster headaches compared to baseline over a three-week treatment period compared to 5.2 fewer headaches with placebo. Full trial results have not been published. The biologic does not appear to be effective in chronic cluster headache (Tepper SJ. Headache 2018;58 Suppl 3:276-290).
Fremanezumab has also been studied in patients with cluster headache; after a failed interim analysis, the manufacturer announced that it no longer plans to pursue this indication.
In chronic migraine, galcanezumab is administered as a loading dose of two consecutive 120-mg subcutaneous injections followed by monthly 120-mg injections. For cluster headaches, dosing is expected to be 300 mg s.c. at the onset of the cluster-headache period, with monthly injections for the duration of the episode.
Among the CGRP class of agents, the longest-term safety data are available for erenumab. After a median exposure of three years, there was a low rate of serious adverse events (4.2/100 patient-years) (Ashina et al. Cephalalgia; epublished May 2019). The most common adverse effects were viral upper respiratory tract infection, sinusitis, influenza and back pain.
CGRP-targeted therapies have grown rapidly since their introduction less than a year ago. In the first quarter of 2019, U.S. sales were USD$59 million for Aimovig, $20 million for Ajovy and $14 million for Emgality.