Shares of drugmakers Amgen Inc. and Novartis AG rose in after-hours trading Thursday after jointly announcing FDA approval of Aimovig, a first-of-its-kind treatment for migraines. In a statement, Novartis said the Federal Drug Administration approved Aimovig's use for the preventive treatment of migraines in adults. "Aimovig is the first therapy of its kind targeting the CGRP receptor, and has demonstrated robust efficacy across the spectrum of migraine," Novartis Chief Executive Paul Hudson said in the statement. "We look forward to working closely with Amgen in the U.S. to bring this treatment to physicians and their patients, who could now gain days of their lives back each month." About 37 million Americans are said to experience migraines. The treatment won't come cheap -- the list price is $6,900 a year, Novartis said. Amgen shares were up 1.3% after hours, while Novartis was up about 0.3%.