About Us

Gideon E. Bollag, Ph.D.

Chief Executive Officer

Dr. Bollag has served as chief executive officer since May 2013. More recently, he was the senior vice president of research since June 2008. Prior, he served as vice president of discovery biology since November 2004. He joined Plexxikon as senior director of drug discovery in June 2002. Dr. Bollag was instrumental in the discovery and development of Zelboraf^®, Plexxikon’s first oncology drug now approved in the U.S. and many other countries, along with its companion diagnostic. Prior to Plexxikon, he helped build drug discovery capabilities at Syrrx, Inc., where he was the director of cellular pharmacology. Before Syrrx, he held escalating positions at Onyx Pharmaceuticals, initially as one of the founding scientists and eventually senior director of small molecule therapeutics. While there, Dr. Bollag was involved in the Onyx collaboration with Bayer to discover BAY 43-9006 (Nexavar), now an approved cancer treatment. Prior to Onyx, Dr. Bollag held various scientific positions at Cetus, Inc. Dr. Bollag earned his Ph.D. in biochemistry from the University of California, Berkeley.

Dr. Zhang has served as Plexxikon’s Chief Scientific Officer since August 2018. More recently, he was the senior vice president of research since November 2015. He joined Plexxikon in 2001 as associate director of bioinformatics and became director of informatics in 2004, leading the company’s efforts in both computational chemistry and computational biology. Dr. Zhang assumed additional responsibilities in 2008 when the structural biology and informatics teams were merged to strengthen the company’s core expertise in structure-guided drug design. Dr. Zhang helped build the scaffold-based drug discovery platform at Plexxikon, and has been a leader and key contributor to the company’s wealth of discovery efforts. Dr. Zhang was instrumental in the discovery of Zelboraf®, Plexxikon’s first oncology drug now approved in the U.S. and many other countries. Prior to Plexxikon, Dr. Zhang was a scientist at Incyte Genomics where he developed an integrated genomics information system for mining disease-related genes and novel drug targets. Dr. Zhang earned his Ph.D. in biomedical engineering from Boston University, and was a postdoctoral fellow at the University of California at Berkeley.

Ms. Hutchinson is SVP & General Counsel, overseeing all finance and operations aspects of the company, as well as business development and legal affairs. She joined Plexxikon in 2013 and has held positions of increasing responsibility since then. Before joining Plexxikon, Ms. Hutchinson represented the UCSF Helen Diller Family Comprehensive Cancer Center in its industry collaborations and negotiations. She received her undergraduate degree from Harvard University and law degree from the University of San Diego School of Law. In her free time, she is a member of the Board of Directors of Community Resources for Science, a non-profit that delivers science curriculum to elementary school teachers and students. She is a member of the California bar.

Jackie Walling MBChB PhD is an experienced biotech pharma executive with expertise in global clinical development and strategy. She has more than 30 years’ experience in developing new medicines for cancer patients and has contributed in various leadership roles to the approvals of widely used agents such as gemcitabine, pemetrexed and talazoparib.

Dr. Spevak has served as vice president of chemistry since August 2018. More recently, he was senior director of chemistry since 2016. He joined Plexxikon in 2004 as a senior scientist and has led the chemistry group since 2009. He is an inventor on 45 issued U.S. patents, and was a contributing member of drug discovery teams leading to 11 novel molecules entering human clinical trials, including Zelboraf®, Plexxikon’s first oncology drug now approved in the U.S. and many other countries. Dr. Spevak is an enthusiastic practitioner of medicinal chemistry based on structure-guided drug design. Prior to Plexxikon, he was director of chemistry at Thios Pharmaceuticals. He began his industry career at Telik, holding a series of positions with increasing responsibility. Dr. Spevak earned his undergraduate degree from Northwestern University, and his Ph.D. degree in chemistry from the University of California, Berkeley. He was a postdoctoral fellow at the Lawrence Berkeley National Laboratory.

Dr. Athanasios Tsiatis has served as Plexxikon’s Vice President, Clinical Development since August 2020. More recently, Dr. Tsiatis has served as Senior Director, Oncology Clinical Development, global lead for the bromodomain program, and clinical lead for the PLX9486 program since joining Plexxikon in May 2018. Previously, Dr. Tsiatis held roles of increasing responsibility in clinical development at Genomic Health from 2011 to 2018 and was integral to the development and commercialization of multiple genomic cancer tests. Dr. Tsiatis completed his postgraduate medical training at Vanderbilt University Medical Center, the Johns Hopkins Hospital, and the Hospital of the University of Pennsylvania. Dr. Tsiatis holds an M.D. from Vanderbilt University School of Medicine and a B.A. in Biology from New York University.

Dr. Jason Halladay has served as Vice President of Nonclinical Development since April 2020. His department integrates DMPK, preclinical and clinical pharmacology, toxicology, and pharmaceuticals and is responsible for the design and execution of translational strategy to bridge preclinical research and clinical studies. Dr. Halladay joined Plexxikon in 2017 to lead the DMPK and early formulation functions and strengthen the company’s core competencies in small molecule drug discovery and development. Prior to Plexxikon, he was Director of DMPK at Anacor Pharmaceuticals. Dr. Halladay began his industry career at Theravance and Genentech, holding a series of positions with increasing responsibility for 13 years. He has a strong interest in drug metabolism, transporters, pharmacokinetics, and hypothesis-driven research to identify molecules with drug-like properties and progress them to the clinic. He is an author on 45 publications and was a contributing member of drug discovery teams leading to several NCEs entering human clinical trials. Dr. Halladay earned his undergraduate degree from Southern Utah University, and his Ph.D. degree in Pharmacology and Toxicology from the University of Arizona.