On June 4 Eli Lilly and Company announced that the US Food and Drug Administration (FDA) had approved Emgality (galcanezumab), an anti-CGRP monoclonal antibody, for the treatment of episodic cluster headache.
Emgality was approved by the FDA in September of last year for the preventive treatment of migraine in adults, and along with Aimovig and Ajovy it is one of the three anti-CGRP monoclonal antibodies presently available for migraine prevention. Briefly, "CGRP" stands for calcitonin gene-related peptide, a protein that plays a major role in conducting the head pain signal through the migraine circuit. Emgality and Ajovy directly inactivate CGRP, while Aimovig blocks the receptor target CGRP must reach in order to complete the migraine circuit.
Cluster is a much less common headache disorder than is migraine. Whereas a whopping 12% of the American population - almost 40 million citizens - actively suffer from migraine, those who have had cluster attacks at any point in their lives number in the several 100s of thousands. Despite this lower prevalence, cluster headache is not to be taken lightly. Acute attacks are so notorious for their intolerable severity that cluster has been termed "the suicide headache,” and when cluster is active attacks may occur as often as 8 times within a single day.
There are two basic types of cluster headache: episodic and chronic. In the episodic form, the afflicted individual experiences multiple attacks on a daily or near-daily basis for a period that may last as little as one week or as long as an entire year. These miserable periods of frequent, severe headache attacks are separated by attack-free remissions that last 3 months or more. In the chronic form of cluster, remission periods are shorter, or there may be no remission whatsoever.
The relevant research accomplished to date has indicated that Emgality administered subcutaneously (under the skin) at a dose of 300 mg once-monthly reduces attack frequency in individuals with episodic cluster who are experiencing an active cycle. Results from that research did not indicate Emgality to be similarly effective in the clinical setting of chronic cluster.
The arsenal of therapies intended to prevent cluster attacks has contained only a few reasonable options. Even those options have lacked much in the way of a true scientific evidence base to support their use, and none of them has possessed an FDA indication for use specifically in treating cluster. While Emgality may not be a panacea for all cluster patients, its identification as a prevention therapy clearly effective in patients with episodic cluster represents a most welcome step forward.