Our Team


Mike Grey

Executive Chairman & CEO

Mr. Grey has 40 years of experience in the pharmaceutical and biotechnology industries and serves as our Executive Chairman and Chief Executive Officer.

He has founded several biotechnology companies and is currently chairman or executive chair of Mirum Pharmaceuticals, Inc., Spruce Biosciences, and Reneo Pharmaceuticals, Inc. He also serves as venture partner at Pappas Capital. Previously, Mr. Grey founded and was President and Chief Executive Officer at Lumena Pharmaceuticals, Inc., a company developing treatments for pediatric and adult orphan diseases, until its acquisition by Shire Plc. Mr. Grey has held senior positions at a number of companies, including President and Chief Executive Officer of Auspex Pharmaceuticals, Inc., President and Chief Executive Officer of SGX Pharmaceuticals, Inc., which was acquired by Eli Lilly in 2008, President and Chief Executive Officer of Trega Biosciences, Inc., which was acquired by Lion Bioscience in 2001, and President of BioChem Therapeutic Inc. For approximately 20 years, Mr. Grey served in various roles with Glaxo, Inc. and Glaxo Holdings plc, culminating in his position as Vice President, Corporate Development and Head of International Licensing. Mr. Grey serves on the board of directors of Horizon Therapeutics plc.

Stephen Mullennix

Chief Financial Officer
Stephen Mullennix

Stephen is the Chief Financial Officer at Plexium.

Mr. Mullennix joined Plexium in 2022 to lead the Finance, Accounting and Investor Relations and other corporate functions at Plexium. He brings deep expertise in operational finance, capital markets and executive leadership roles.

Mr. Mullennix joined Plexium from ProSciento, Inc., a leading Clinical Research Organization in the metabolic disease arena, where he served as CFO. Prior to ProSciento, Mr. Mullennix was CFO and COO of UroGen Pharma, Ltd (NYSE:URGN), a uro-oncology drug developer. During his tenure at UroGen, he led finance functions as the CFO, and then transitioned to COO as the company successfully launched JELMYTO, its first FDA-approved drug for urothelial cancer. Before UroGen, Mr. Mullennix was Chief Financial Officer and Senior Vice President of Operations at SolarReserve, LLC, and Managing Director at US Renewables Group, a private equity investment fund with more than $750 million of assets under management.

Mr. Mullennix has been directly involved in $3.3 billion of public, private, equity, debt and M&A transactions. He earned his MBA from the Anderson School at University of California Los Angeles and BA in Economic Geography from Dartmouth College.

Simon Bailey, Ph.D., MBA

Executive Vice President, Drug Discovery

The Head of Drug Discovery at Plexium, Simon oversees the company’s efforts to identify novel protein degrader drugs that address significant unmet medical needs.

Simon joined Plexium in 2019, bringing more than 25 years of experience in medicinal chemistry and small molecule drug discovery leadership. From 1995-2015, Simon held positions of increasing responsibility at Pfizer, including leading the Diabetes and Oncology Medicinal Chemistry Departments. Subsequently, Simon was the Head of Research and Global Pipeline Leader for Intercept Pharmaceuticals. There, he led the company’s programs from inception to Phase 2 in the area of fibrotic liver disease. Simon holds a Ph.D. and was the Hibbert Prize winner in synthetic organic chemistry from the University of Manchester. He completed postdoctoral studies under Prof. Leo Paquette at the Ohio State University and obtained an MBA from the University of California, San Diego. Simon is a 2021 recipient of the American Chemical Society’s Hero of Chemistry award for his role in the discovery of Lorbrena™.

Kevin Eastwood

Executive Vice President, Corporate Business Development

Kevin is the Executive Vice President of Corporate Development for Plexium.

He leads corporate strategy and is responsible for establishing external partnerships, managing strategic alliances, and supporting corporate financing initiatives. With over 30 years of industry experience, Kevin joined Plexium after working with large biotechnology companies, such as Agouron Pharmaceuticals and Gilead, and venture-backed start-ups, such as Achillion Pharmaceuticals and eFFECTOR Therapeutics. Prior to joining Plexium, Kevin was the Vice President of Corporate Development for the California Institute for Biomedical Research. He began his business development career at Agouron Pharmaceuticals and has significant experience across strategic partnerships, in-licensing, out-licensing, and M&A. Kevin graduated from Missouri State University with a degree in biology.

Suzanne Zoumaras

Executive Vice President, Head of Human Resources

Ms. Zoumaras is the Executive Vice President, Head of Human Resources for Plexium.

Prior to joining Plexium, Ms. Zoumaras was a Co-Founder and Managing Partner of Human Capital Resource Partners, a human capital and advisory services consulting firm. Before that, she served as Executive Vice President & Chief Human Capital Officer at Arena Pharmaceuticals, Executive Vice President and Chief Human Resource Officer at Teradata, and as Senior Vice President of Global Human Resources at Atmel Corporation (acquired by Microchip). She is also an adjunct professor in the Fowler School of Management at San Diego State University where she teaches Total Rewards. Ms. Zoumaras received her BS in Finance from San Diego State University and an HR Certificate, Human Resources from the University of California, San Diego.

Daniel Sipes

Senior Vice President, Head of Technology

Mr. Sipes leads the Engineering, Software, Informatics, and Compound Management groups.

Before joining Plexium, Daniel served as SVP, Strategy and Operations, Site Head San Diego at Strateos (formerly Transcriptic), where he was responsible for building and operating remotely controlled cloud labs for automated chemistry and biology. Before Strateos, he was Director, Advanced Automation Technologies at the Novartis Institutes for BioMedical Research (NIBR) San Diego location (formerly GNF). While at NIBR, Daniel developed and implemented new technologies for drug discovery, assay development, high throughput screening, automated cell culture, and protein production. Before that, he held positions focused on high throughput screening and compound management at Kalypsys, Inc. and Ligand Pharmaceuticals. Daniel started his career in the Hybridoma Laboratory at Genentech. He received his BS in Molecular Biology from California State University, Sacramento, and an MS, in Immunology from the University of California, Davis.

Peggy Thompson, Ph.D.

Vice President, Biology

Peggy is the Vice President of Biology, leading the targeted protein degradation drug discovery efforts at Plexium.

Peggy joined Plexium in 2020 with more than 20 years of experience in drug discovery and development in the biotechnology industry. Prior to Plexium, she was a co-founder and Executive Director of Biology at eFFECTOR Therapeutics, where she established their technology platform for targeting dysregulated mRNA translation for supporting oncology drug development. She also led their eIF4A program (Zotatifin, Phase II) from concept to clinical development in solid tumor malignancies. Before that, Peggy served as the Director of Biology at Anadys Pharmaceuticals, Inc., where she held positions of increasing responsibility, including leading the drug discovery biology efforts and supporting the development of Setrobuvir until the acquisition by Roche Pharmaceuticals. Prior to Anadys, Peggy held positions at Biopraxis and the National Institutes of Health. She was an NIH postdoctoral fellow in Biophysics at the University of California, Berkeley, and completed her Ph.D. in Chemistry from the University of California, San Diego. She received her B.S. with Highest Distinction in Biochemistry from Washington State University.

Kevin Freeman-Cook, Ph.D.

 VP, Head of Medicinal and Computational Chemistry

Kevin is the Vice President of Medicinal and Computational Chemistry, leading the design and synthesis of targeted protein degraders at Plexium.

Kevin joined Plexium in 2022 with extensive pharmaceutical industry experience. Before joining Plexium, Kevin worked for twenty-two years at Pfizer, where he held positions of increasing responsibility, including Research Fellow. Kevin led numerous medicinal chemistry teams and drug discovery programs during this time. Kevin spent ten years in Groton, CT working in the therapeutic areas of allergy and respiratory disease, inflammation, antibacterials, oncology, and diabetes. In 2009, Kevin moved to Pfizer’s La Jolla, CA site, where he focused on medicinal chemistry design in oncology. Over these years, Kevin worked in and led teams that have nominated five compounds for clinical development across multiple therapeutic areas. Dr. Freeman-Cook received his BA in chemistry from Carleton College in 1994 and a Ph.D. in organic chemistry from the University of Colorado Boulder in 1999.

Board of Directors

Cariad Chester

Partner, TCG X

Ian Peikon

Partner, Lux Capital

Rob Hopfner

Managing Partner, Pivotal Bioventure Partners

Gorjan Hrustanovic

Managing Director at BVF Partners L.P.

Eric Shiozaki

Partner DCVC

Brian Wong, M.D., Ph.D.

President and CEO of RAPT Therapeutics