Four pharmaceutical companies are racing to develop a new drug that can prevent migraines with fewer side effects by blocking a compound released in the brain.

For the millions of people who suffer from migraines, some relief may be on the way.

More than 100 drugs and other treatments are available for migraines, but they don’t work for everyone. And many have serious side effects, or can only be used after a migraine starts.

Several new experimental drugs currently under development could — once fully tested and approved — provide people with other options for early relief.

These drugs target molecules released by a hyperactive nerve system in the brain that is believed to be involved in triggering the pain and other debilitating symptoms of these intense headaches.

The drugs were formally unveiled in June at the annual meeting of the American Headache Society.

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Two recent clinical trials published in The Lancet found that this type of drug — known as a calcitonin gene-related peptide (CGRP) inhibitor — may work for both occasional and chronic migraines.

According to the Migraine Research Foundation, 36 million people in the United States suffer from migraines. Of those, 14 million have chronic migraines — experiencing 15 or more “headache days” per month.

In the clinical trials, people given the CGRP inhibitor experienced fewer days or hours per month with a headache, compared to people given an inactive placebo.

The most common side effects were mild pain at the site of the injection and itchy skin.

In an accompanying editorial, Dr. Julio Pascual, Ph.D., of University Hospital Marques de Valdecilla in Santander, Spain, wrote that the drug worked well and was well tolerated by most people, but when compared to the placebo the “overall efficacy of these antibodies does not seem to be dramatic.”

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The CGRP inhibitor is a type of monoclonal antibody – a common type of “biologic” medication – that blocks the activity of a molecule known as a calcitonin gene-related peptide.

The body uses this molecule to control the flow of blood to various tissues — including the brain — by constricting or dilating blood vessels.

Scientists believe that migraines trigger the release of this molecule — along with others — from the trigeminal nerve in the brain.

This leads to widening of the blood vessels and inflammation of the nerves. This can prolong migraines by causing the trigeminal nerve to become hyperactive and release more of these molecules.

Pain signals sent by the trigeminal nerve are thought to cause not only the severe headache pain associated with migraines but also the sensitivity to environmental triggers common among people with this condition.

Migraine attacks can last between four and 72 hours. They are often accompanied by sensitivity to light and sound, nausea or vomiting, tingling or numbness in the limbs or face and visual disturbances.

Other drugs, called triptans, also target CGRP, including sumatriptan and zolmitriptan.

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Because CGRP is used throughout the body, more research is needed to know if this drug is safe and effective over the long-term.

Also, other molecules may be involved in producing the pain and other symptoms of migraine, so blocking CGRP alone may not be enough for preventing a migraine attack in every person.

The results of the two Lancet trials, though, were promising enough that the researchers intend to test the drug in larger clinical trials.

These studies were supported by Teva Pharmaceuticals, which recently entered into a product development deal with Heptares Therapeutics, the company that discovered this potential migraine treatment.

Other drug companies are also pursuing treatments for preventing migraines using CGRP inhibitors. This includes Eli Lilly and Company, Amgen, and Alder Pharmaceuticals.

None of these drugs has gone through the final stages of clinical trials needed for approval by the Food and Drug Administration, so it could be at least a year before any of them hit the market.

In the meantime, migraine sufferers can continue to work with their doctor to find a treatment —or combination of treatments — that reduces their migraine symptoms.