Mardi Dier is the Chief Financial Officer (CFO) and Chief Business Officer (CBO) of ACELYRIN, Inc. She previously served as CFO and executive vice president of Ultragenyx Pharmaceutical. Prior to that, she was  CFO and CBO of Portola Pharmaceuticals until its acquisition by Alexion Pharmaceuticals in 2020. Before this, Ms. Dier served as vice president of investor relations at Chiron Corporation from 2003 to 2006. Earlier in her career, she worked as an investment banker at Prudential Securities, and prior to that she worked in the audit department at KPMG Peat Marwick. Ms. Dier received a bachelor’s degree in biology from Stanford University and MBA from the Anderson School at the University of California, Los Angeles.