Emgality (galcanezumab) is a prescription medication used to prevent migraine headaches in adults and to treat episodic cluster headaches. It was approved by the FDA in September 2018 and works by blocking a protein involved in triggering head pain. It’s given as a monthly injection, either at a doctor’s office or self-administered at home.
How Emgality Works
During a migraine or cluster headache attack, your body releases a signaling protein called CGRP (calcitonin gene-related peptide). This protein dilates blood vessels around the brain and triggers inflammation and pain signaling in the nervous system. Emgality is a lab-made antibody that latches onto CGRP before it can reach its receptors, essentially intercepting the pain signal before it starts.
Because Emgality targets the protein itself rather than the receptor, it neutralizes CGRP circulating in your system around the clock. This is what makes it a preventive treatment rather than something you take during an attack. It doesn’t stop a migraine that’s already happening, but it reduces how often they occur in the first place.
Migraine Prevention
Emgality’s primary use is reducing the number of migraine days per month in adults. In clinical trials (EVOLVE-1, EVOLVE-2, and REGAIN), patients with both low-frequency and high-frequency migraines saw statistically significant drops in monthly migraine days compared to placebo. The benefit held across people with episodic migraine (fewer than 15 headache days per month) and chronic migraine (15 or more).
Across these trials, significantly more patients on Emgality achieved at least a 50% reduction in monthly migraine days, and a meaningful proportion hit 75% or even 100% reductions. Some patients notice improvement as early as one week after the first injection, though it can take longer for the full effect to build. The medication is currently approved for adults only.
Episodic Cluster Headache Treatment
Cluster headaches are a distinct condition from migraines. They cause intense, stabbing pain on one side of the head, usually around the eye, and arrive in “cluster periods” lasting weeks or months. Emgality is the first FDA-approved treatment specifically for reducing the frequency of episodic cluster headache attacks.
Real-world data from the GRASP study group gives a useful picture of what patients can expect. People with episodic cluster headaches averaged about 2.6 attacks per day before treatment. After four weeks on galcanezumab, that dropped to 1.2 attacks per day. Roughly 63% of patients were classified as treatment responders, meaning their attack frequency fell by at least half. About a third of responders saw reductions of 75% or more.
It’s worth noting that Emgality is approved only for episodic cluster headaches, not the chronic form. However, early real-world evidence has shown promising results in chronic cluster headache patients as well, with daily attacks dropping from 2.8 to 1.5 over four weeks and a 65% response rate.
How It’s Taken
Emgality is injected under the skin (subcutaneously), typically in the thigh, abdomen, or back of the upper arm. The dosing schedule differs depending on the condition being treated.
For migraine prevention, treatment starts with a loading dose of 240 mg, which is two back-to-back injections of 120 mg each. After that, you give yourself one 120 mg injection once a month. The loading dose is designed to get enough of the antibody into your system quickly so you don’t have to wait weeks for protection to kick in.
For episodic cluster headaches, the dose is higher: 300 mg at the start of a cluster period, given as three consecutive 100 mg injections. You then continue with 300 mg monthly until the cluster period ends. The injections come in prefilled syringes or autoinjectors, and most people manage them at home after initial guidance from a healthcare provider.
Common Side Effects
Emgality is generally well tolerated. Across the major clinical trials, the rate of side effects in patients taking the drug was only slightly higher than in those taking a placebo, ranging from about 51% to 66% experiencing at least one side effect (compared to 50% to 62% on placebo). Fewer than 3% of patients experienced a serious adverse event, and fewer than 4% stopped treatment because of side effects.
The most frequently reported issues were:
- Injection site reactions: Pain, redness, or itching at the injection site was the most common complaint, reported by up to 16% of patients in one trial. This tends to be mild and short-lived.
- Upper respiratory symptoms: Nasopharyngitis (a common cold), sinus infections, and upper respiratory infections appeared in roughly 3% to 9% of patients across studies.
- Other occasional effects: Dizziness, nausea, back pain, neck pain, constipation, and diarrhea each showed up in small percentages, generally in the 2% to 4% range.
Injection site pain is the side effect most directly tied to the medication itself. The respiratory infections occurred at rates only slightly above placebo, so they may not be caused by the drug at all. Overall, Emgality’s safety profile is one reason it has become a widely used option for people whose migraines haven’t responded well to older preventive medications like blood pressure drugs or antidepressants.
Who Emgality Is Typically Prescribed For
Emgality tends to be recommended for adults who experience four or more migraine days per month and haven’t gotten adequate relief from, or can’t tolerate, other preventive treatments. Many insurance plans require you to have tried and failed at least one or two older preventive medications before they’ll cover a CGRP inhibitor like Emgality.
For cluster headaches, it fills a gap that previously had no FDA-approved preventive option. People who experience recurring cluster periods, particularly those with predictable seasonal patterns, are the primary candidates.
Emgality is not approved for use in children or adolescents. The only listed contraindication is a known serious hypersensitivity to galcanezumab or any of its inactive ingredients, which is rare.