Interim Data From Phase 2 Trial of AC220 Monotherapy in Patients With Relapsed or Refractory Acute Myeloid Leukemia With

Ambit Biosciences is a privately-held biopharmaceutical company engaged in the discovery and development of small molecule kinase inhibitors for the treatment of cancer, inflammatory disease, and other indications. Ambit's lead compound, AC220, is a novel, potent, highly selective, orally bioavailable FMS-like tyrosine kinase-3 (FLT3) inhibitor, and is currently under clinical investigation in patients with relapsed or refractory AML. Ambit is developing AC220 in collaboration with Astellas Pharma Inc. as part of a worldwide agreement to jointly develop and commercialize FLT3 kinase inhibitors in oncology and non-oncology indications. In addition to AC220, Ambit's clinical pipeline includes AC480, an oral pan-HER inhibitor, and AC430, an oral JAK2 inhibitor. Ambit also has a pipeline of preclinical candidates which includes CEP-32496, a BRAF inhibitor licensed to Cephalon.

About Astellas

Astellas Pharma Inc., located in Tokyo, Japan, is a pharmaceutical company dedicated to improving the health of people around the world through provision of innovative and reliable pharmaceuticals. Astellas has approximately 16,000 employees worldwide. The organization is committed to becoming a global category leader in Urology, Immunology & Infectious Diseases, Oncology, Neuroscience, and DM complications & Metabolic Diseases. For more information on Astellas Pharma Inc., please visit our website at http://www.astellas.com/en.

CONTACT: Contacts: Ambit Biosciences: Alan Fuhrman, Chief FinancialOfficer, +1-858-334-2133; Doug Sherk/Jenifer Kirtland, EVC Group,+1-415-896-6820; Media: Janine McCargo, EVC Group, +1-646-528-4034; Astellas Pharma Inc: CorporateCommunications, +81-3-3244-3201