Executive Management


Chief Executive Officer

Dr. David J. Bearss brings a consistent and successful track record of drug discovery and development that spans the last 20 years in both academic and industrial settings. Dr. Bearss is an expert in small-molecule drug development and in the use of genetic model systems in drug discovery. He has deep experience in translational research focused on drug development and the use of genetic and functional markers to predict drug sensitivity. He is also an expert in the development and use of genetically modified animals to model human disease. Dr. Bearss received his PhD in Cell and Structural Biology at the University of Texas Health Sciences Center at San Antonio and was a post-doctoral fellow with Dr. Daniel Von Hoff, a recognized leader in oncology drug development. Dr. Bearss was on faculty at the University of Arizona from 1999 to 2003, after which he co-founded Montigen Pharmaceuticals where he served as Chief Scientific Officer until Montigen was acquired by SuperGen in 2006. Dr. Bearss served as Chief Scientific Officer at SuperGen overseeing early drug discovery and development and subsequently as Co-director of the Center for Investigational Therapeutics at the Huntsman Cancer Institute where he was an Associate Professor in the Department of Oncological Sciences at the University of Utah. Dr. Bearss was also an Associate Professor of Physiology & Developmental Biology at Brigham Young University. Dr. Bearss has published more than 70 manuscripts and book chapters, is an author over 150 abstracts at international meetings and has more than 50 patents issued or pending. Dr. Bearss has also won several awards for his scientific and entrepreneurial achievements.


Chief Financial Officer

David Sampson has extensive experience working with both small to medium-sized companies in rapidly growing environments and also with large publicly traded companies. Before joining Tolero, Mr. Sampson served as the Vice President of Finance and Principal Accounting Officer of Fusion-io, Inc., during a period of rapid growth—including sales growth from $36 million to over $400 million, the company's initial public offering, and its expansion internationally—prior to the ultimate acquisition by SanDisk Corporation for a value exceeding $1 billion in market capitalization. Prior to Fusion-io, Mr. Sampson was Vice President of Finance for Ancestry.com, Inc. where he oversaw all financial and accounting, treasury and credit card processing aspects of the company and was instrumental in the company's international expansion, acquisitions and initial public offering. Mr. Sampson also spent twelve years of his career at Ernst and Young in Palo Alto, California and Salt Lake City, Utah where he assisted small entrepreneurial to large multinational companies with technical accounting issues, debt financing arrangements, initial public offerings, and compliance with SEC filing requirements. Mr. Sampson is a Certified Public Accountant in the state of California and Utah and has a Bachelor of Science degree in accounting from Brigham Young University.


Chief Operating Officer

Dr. Michael V. McCullar serves as the Chief Operating Officer for Tolero Pharmaceuticals. Most recently, Dr. McCullar served as Senior Vice President of Business Development of Astex Pharmaceuticals, which was acquired by Otsuka Pharmaceuticals for $880 million in cash. Dr. McCullar held other senior positions within Astex Pharmaceuticals and predecessor organizations including Senior Vice President of Strategy and Operations where he led SuperGen's acquisition of Astex Therapeutics as well as the acquisition of Montigen Pharmaceuticals. Dr. McCullar held the position of VP of Strategy and Development and led the approval of Dacogen in MDS and held operating responsibility for SuperGen's European commercial business. Dr. McCullar has been involved with several ANDAs as well as INDs and held management positions in Drug Discovery, Regulatory Affairs and CMC. Dr. McCullar served on the Board of Trustees for the Leukemia and Lymphoma Society. Dr. McCullar holds a PhD in Toxicology from the University of California, Riverside as well as an MBA from the W.P. Carey School of Business at the Arizona State University, Tempe.


Chief Strategy Officer

Katsumi Tanaka headshot

Mr. Katsumi Tanaka serves as the Chief Strategy Officer for Tolero Pharmaceuticals. Most recently, Mr. Tanaka served as Senior Officer of Business Development of Sumitomo Dainippon Pharma and engaged in its acquisition of Tolero Pharmaceuticals in January 2017. Prior to the acquisition, Mr. Tanaka led numerous business collaborations between Sumitomo Dainippon Pharma and pharma/biotechnology companies such as AstraZeneca, Nitto Denko, SanBio, Intercept Pharmaceuticals, Edison Pharmaceuticals and so on. Mr. Tanaka worked for Sumitomo Dainippon Pharma for 25 years and was involved in CMC management and development of its products. Mr. Tanaka earned his MBA from Kobe University and Master degree in Pharmacy from Kyoto University. Mr. Tanaka holds qualifications of Patent Attorney and Pharmacist in Japan.


Vice President, Clinical Research

Stephen Anthony headshot

Dr. Stephen P. Anthony serves as our Vice President of Clinical Research and has over 20 years of Hematology and Oncology drug development experience in the academic, private practice and industrial sectors. He is well published in the field of Hematology and Oncology Drug Development. As a founding member of the US Oncology Phase 1 program, he has participated in hundreds of Phase 1 Hematology and Oncology Clinical trials for several drugs now approved. He has also been involved with Phase 2 and 3 clinical trials. In addition, he has expertise in precision medicine with a strong understanding of the genomic mechanisms of disease. Dr. Anthony was the Director of the Phase 1 partnership between the Translation Genomic Institute (TGen) and Honor Health in Scottsdale, AZ. Dr. Anthony also served as the Chief Medical Officer for TGen's Drug Development (TD2) unit in Scottsdale, AZ. He obtained his medical degree from The Philadelphia College of Osteopathic Medicine, completed an Internal Medicine Residency at Hahnemann University Hospital in Philadelphia, PA. Dr. Anthony completed his fellowship at Dartmouth's Mary Hitchcock Medical Center in Lebanon, NH. His research was focused in the section of Pharmacology and Toxicology at Dartmouth Medical School. Dr. Anthony also served as a Flight Surgeon during the Gulf War.


Vice President, Drug Discovery and Development

Steven L. Warner, PHD headshot

Steven Warner, PhD, specializes in small molecule drug discovery, new screening platforms in drug discovery, and translational research focusing on cancer therapeutics. He is an expert in the discovery of novel cancer agents and has played integral roles in moving multiple compounds into clinical trials. Dr. Warner has a broad background in molecular and cell biology that comes from nearly a decade of involvement in drug discovery and development in both academic and pharmaceutical industry settings. Dr. Warner earned his graduate degree in Pharmaceutical Sciences at the University of Arizona. He completed a postdoctoral fellowship under the mentoring of Dan Von Hoff at the Translational Genomics Research Institute (TGen). In 2007, Dr. Warner joined SuperGen Inc. where he led a team of scientists focusing on studies ranging from initial compound library screens to proof-of-concept studies in animal models. Most recently, Dr. Warner has worked with the Center for Investigational Therapeutics at the Huntsman Cancer Institute as Senior Manager, Drug Discovery. Together in these capacities, he has led or integrally participated in drug discovery projects that have produced three first-in-man clinical compounds and has published several peer-reviewed publications and patents from multiple drug discovery projects.

Kotaro Hirota

Vice President, Global Relations

Kotaro Hirota Headshot

Mr. Kotaro Hirota serves as the Vice President of Global Relations for Tolero Pharmaceuticals. After his 14-year career as a research scientist in pharmacology, Mr. Hirota broadened his experience as a Medical Science Liaison, and a product leader in oncology arena. In 2013, Mr. Hirota joined Boston Biomedical, Inc., a sister company of Sumitomo Dainippon Pharma Global Oncology, and worked to liaise closely with research, clinical development, medical affairs, and commercial team among the group companies. He also led naming processes for global oncology assets with authorities. Mr. Hirota will coordinate Corporate Communications for US-based subsidiaries in oncology in conjunction with Sumitomo Dainippon Pharma Co., Ltd., the Japan-based parent company. He earned his Master degree in Pharmaceutical Technology, Biology from The University of Tokyo.


Vice President, Regulatory Affairs

Michael A. Bernstein, MPH headshot

Over 28 years of professional experience in the Pharmaceutical/Biotech/Device industry encompassing the areas of clinical and regulatory strategy, quality assurance and CMC strategy with experience in oncology, neurology, psychopharmacology, dermatology and wound care as well as other indications. Mr. Bernstein spent 11 years at FDA and has extensive experience working with regulatory agencies around the world. Mr. Bernstein has submitted more than 20 INDs/CTXs and has submitted 9 NDAs/BLAs/MAAs, receiving approval for 5 NDAs/BLAs/MAAs. He has also submitted 6 510(k)s and received clearance on all of them. Mr. Bernstein currently resides in San Antonio, Texas and was a former employee of Ilex Oncology, a Texas-based pharmaceutical company started by Dr. Dan Von Hoff.

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