Approximately 12% of Americans experience migraines. For some people, the attacks are so frequent and painful that episodes can be incapacitating. Historically, doctors have tried a variety of approaches to treating the condition, including drugs that numb nerves, medications that constrict blood flow, and as well as a variety of behavioral approaches. While some patients have found relief using these methods, many are not helped by current treatments.
A few of these patients may find relief in a new treatment recently produced by Amgen. The treatment was developed in response to the discovery of a molecule called CGRP, which may play a causal roll in migraines. CGRP increases the size of blood vessels, and transmits pain signals through the brain. CGRP is plentiful in the blood of migraine patients who come to the emergency room. Injecting CGRP into migraine sufferers has been shown to trigger an attack.
Early efforts to inhibit CGRP were hampered by side effects. Drug companies started by looking for a small chemical, no more than a few dozen atoms in total, that could make its way into the brain. Unfortunately, the chemicals originally designed caused liver damage and other unacceptable side effects. The alternative was to use a much larger molecule, called an antibody, that could recognize CGRP and cause fewer side effects. The downside is that antibodies typically can’t get into the brain.
Despite the difficulty of getting to the brain, several pharmaceutical companies started research on an antibody to target CGRP and relieve migraines around 2013. The new drugs had fewer side effects that earlier attempts, and seemed to decrease the number of migraines per month in many patients. For about 15% of patients, the drug stopped migraines altogether. Researchers aren’t sure how the antibody manages to be effective without accessing the brain, but it seems targeting the CGRP outside the brain is effective for some patients.
There are downsides to the choice to use an antibody. Our expert, Nick Warren, a PhD candidate in Experimental and Molecular Medicine at Dartmouth, points out that antibody treatments are expensive. This newly approved medication is predicted to cost more than $8000 dollars a year and patients will need to continue taking it indefinitely. Additionally, while the drug is great for the subset of patients it works for, the majority of patients continue to experience at least occasional migraines.
Managing Correspondent: Emily Kerr
Acknowledgements: Many thanks to Nick Warren, a PhD candidate in Experimental and Molecular Medicine at Dartmouth