WASHINGTON -- Erenumab (Aimovig) became the first of a new class of preventive drug candidates for migraine treatment to gain , with the agency's announcement late Thursday.
A fully humanized monoclonal antibody, erenumab is designed to block the calcitonin gene-related peptide (CGRP) receptor. CGRP is a potent vasodilator and vascular dysfunction is believed to play a significant role in migraine. Triptan drugs, which have long been the staple of migraine treatment, also modulate vascular tone but in a different way. Most other drugs used in migraine that are not simply painkillers, such as beta blockers, are also vasoactive in some fashion.
The drug "provides patients with a novel option for reducing the number of days with migraine," said Eric Bastings, MD, the FDA's deputy director of neurology drugs, in a statement. "We need new treatments for this painful and often debilitating condition."
Erenumab's effectiveness was evaluated in three clinical trials in which patients who used the drug had an average of 1 to 2.5 fewer monthly migraine days than those who received placebo. The drug also showed efficacy in the phase IIIb LIBERTY trial.
"The LIBERTY trial was important because it was the first prospective, placebo-controlled randomized trial of one of the new antibodies in patients who had previously had a complete lack of efficacy from 2 to 4 prior preventive migraine treatments," said Stewart Tepper, MD, of the Geisel School of Medicine at Dartmouth in Hanover, New Hampshire, who has been involved in clinical trials of erenumab and other CGRP inhibitors.
"The fact that this designer migraine preventive medication erenumab is effective in patients who are really most impaired and difficult to treat is both exciting and encouraging," Tepper told 鶹ý.
Erenumab is one of four monoclonal antibodies in development that target CGRP to prevent migraine. These drugs have a mechanism of action that seems different from existing treatments and may work well in people who cannot tolerate other migraine medications, noted Elizabeth Loder, MD, of Brigham and Women's Hospital in Boston.
But they will be expensive, she said. Last month, the (ICER) prepared a draft report suggesting that while CGRP inhibitors are more effective than placebo, they may not be more effective than existing treatments like topiramate (Topamax) or propranolol.
Amgen and Novartis, which are marketing erenumab in partnership, set an for the drug, and some CGRP inhibitors may cost even more if and when they are approved, according to estimates from industry analysts.
Loder suggested that the price of the drug could exceed most commonly accepted cost-effectiveness thresholds. "This, along with the lack of information about long-term safety, means that they will not be first-line treatments." And safety in pregnancy is unknown, which is something doctors who prescribe CGRP inhibitors need to consider since the burden of migraine is highest in women of reproductive age, she added.
"From a clinical perspective, the initial role for these antibody treatments will be for patients with frequent, disabling migraine that cannot be adequately or safely treated with alternative preventive treatments," Loder told 鶹ý.
Erenumab is a self-administered, monthly injectable drug; its most commonly reported side effects in clinical studies were injection site reactions and constipation. Amgen and Novartis expect it to be available to patients within 1 week.