Notes to Editors

About CGRP Antagonists for Migraine and Other Severe Headaches
Calcitonin gene related peptide (CGRP) is released during migraine attacks and can trigger migraine in patients. CGRP is found in small to medium sized neurons in the trigeminal ganglion of the brain and mediates its activity through G protein-coupled receptors located throughout the body. Elevated levels of CGRP are found in people with migraine during an attack and blocking CGRP activity is a validated mechanism of action for relieving pain, and also for preventing migraine.

About Migraine
Approximately 36 million people in the United States and 8 million people in Japan suffer from migraine. Migraine is three times more common in women than in men and affects more than 10 percent of people worldwide. Migraine is defined as recurring attacks of moderate to severe headache pain, typically one-sided, throbbing and worse with activity. The International Headache Society defines chronic migraine as more than 15 headache days per month over a three-month period of which more than eight are migraine, in the absence of medication over use. Episodic migraine is the other migraine sub-type, which is defined as less than 15 headache days per month. During migraine, people can experience varying characteristics such as being very sensitive to light and sound, or experiencing nausea and vomiting. There is no absolute cure for migraine since its pathophysiology has yet to be fully understood.

Forward-looking statements
This press release contains forward-looking statements, including statements about the discovery, development and commercialisation of products. Various risks may cause Sosei’s actual results to differ materially from those expressed or implied by the forward-looking statements, including: adverse results in clinical development programs; failure to obtain patent protection for inventions; commercial limitations imposed by patents owned or controlled by third parties; dependence upon strategic alliance partners to develop and commercialise products and services; difficulties or delays in obtaining regulatory approvals to market products and services resulting from development efforts; the requirement for substantial funding to conduct research and development and to expand commercialisation activities; and product initiatives by competitors. As a result of these factors, prospective investors are cautioned not to rely on any forward-looking statements. We disclaim any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

---