Galcanezumab, sold under the brand name Emgality, is a humanized monoclonal antibody used for the prevention of migraine. It is also used for cluster headaches. Common side effects include pain or redness at the site of injection. Other side effects may include hypersensitivity reactions. A substance called calcitonin gene-related peptide (CGRP) has been shown to be involved in the development of migraine by widening blood vessels in the brain. Galcanezumab is a monoclonal antibody (a type of protein) designed to attach to and block CGRP, thereby helping blood vessels to return to their normal size. This will stop the symptoms of migraine.