Paula Ragan, PhD
CEO and President
Dr. Ragan has been X4’s President and Chief Executive Officer and a member of the X4 Board of Directors since July 2014. She has more than 18 years of experience building companies in the biotechnology industry. Prior to founding X4, Dr. Ragan consulted as Chief Business Officer at Lysosomal Therapeutics Inc., a private biopharmaceutical company, where she led the company’s business development activities. Prior to that, Dr. Ragan held leadership roles in corporate development and operations at Genzyme Corporation, a Sanofi company, where she led strategic partnering efforts for Genzyme’s Rare Disease business and headed the supply chain planning for Genzyme’s flagship commercial products. Other professional roles include business roles at Hydra Biosciences, Oscient Corporation and Celera Corporation. Since 2019, Dr. Ragan is a member of the Board of Directors at Camp4. Dr. Ragan received her B.S. from Tufts University and her Ph.D. from Massachusetts Institute of Technology and completed post-doctoral studies at Harvard Medical School. Read More
Adam Mostafa
Chief Financial Officer
Mr. Mostafa has served as X4’s Chief Financial Officer since September 2018. Prior to joining X4, Mr. Mostafa served as chief financial officer of Abpro Corporation, a biotechnology company focused on antibody therapeutics. Prior to that, Mr. Mostafa was a managing director in the healthcare investment banking group at Cantor Fitzgerald, and was a senior banker in the healthcare investment banking group at Needham & Company. Prior to that, Mr. Mostafa was a vice president in the investment banking group at CRT Capital Group, and was a portfolio management associate in the global stock selection group at AQR Capital. He began his career as an analyst in the healthcare investment banking group at Salomon Smith Barney. Mr. Mostafa earned an A.B. in Economics from Brown University. Read More
Diego Cadavid, MD
Chief Medical Officer
Diego Cadavid, MD, joined the X4 team as Chief Medical Officer in December 2020. He brings more than 22 years of experience in drug development and academic research to X4, having led multiple programs through all phases of clinical development, including small molecules and biologics for the treatment of rare and immunological diseases. Most recently, Dr. Cadavid served as Senior Vice President and Head of Clinical Development at Fulcrum Therapeutics where he led the development of multiple small molecules for the treatment of genetically defined rare diseases, including facioscapulohumeral muscular dystrophy, sickle cell disease and beta-thalassemia. Prior to Fulcrum, Dr. Cadavid held several leadership positions at Biogen over an eight-year tenure, including Senior Medical Director of the multiple sclerosis clinical development group. While at Biogen, he also worked as a consultant at the center for immunology and inflammatory diseases at Massachusetts General Hospital (MGH). Previously, Dr. Cadavid was a faculty member at Rutgers-New Jersey Medical School for over 9 years. Dr. Cadavid holds an MD in medicine and surgery from the Pontificia Universidad Javeriana in Bogotá, Colombia, and completed post-doctoral training in microbiology and immunology at the University of Texas Health Science Center in San Antonio, Texas (UTHSCSA). He completed a clinical neurology residency at Georgetown University and conducted a fellowship in neuropathology at Armed Forces Institute of Pathology, both in Washington, DC. He is board-certified and a U.S. licensed clinical neurologist. Dr. Cadavid has published more than 100 peer review publications, review papers, and book chapters. Read More
Art Taveras, PhD
Chief Scientific Officer
Dr. Art Taveras joined the X4 team as Chief Scientific Officer in October 2020. He brings more than 30 years of experience leading small molecule research and development programs focused on the treatment of cancer, dysregulated immune disorders, neurodegeneration and metabolic diseases. His research and leadership have led to the development of multiple IND candidates and dozens of clinical trials. He joins X4 from CoMET Therapeutics, where he served as Chief Scientific Officer leading the development of treatments for Inborn Errors of Metabolism (IEM) diseases and metabolic disorders. Previously, he was the Founder and Chief Scientific Officer at Transform Therapeutics, a company aiming to discover CXCR2 antagonists for the treatment of cancer and served as President and Chief Scientific Officer at ShangPharma ChemPartner where he supported discovery and clinical portfolios of hundreds of pharmaceutical and biotech companies worldwide. Prior to that, Dr. Taveras was Vice President of Small Molecule Drug Discovery and CMC Development at Biogen Idec, where he led the discovery and development of neurology, immunology and oncology drug candidates at its multiple sites in the U.S. and abroad. He also was Vice President of drug discovery and development at Alantos Pharmaceuticals, which was acquired by Amgen in 2007, where he spearheaded the company's discovery research and built its diabetes and matrix metalloproteinase franchise in the U.S. and Germany. Dr. Taveras began his career with Schering-Plough Corporation and held multiple roles of increasing responsibility in the oncology and immunology drug discovery and research sector over a 14-year period, including leading the discovery of Navarixin®, a CXCR2 antagonist currently in clinical trials in combination with pembrolizumab for the treatment of cancer. He holds 130 issued patents and patent applications and has authored more than 90 scientific publications. Dr. Taveras received his B.S., M.S. and Ph.D. from Rensselaer Polytechnic Institute. Additionally, he attended the college of advancing studies at Boston College. Read More
Derek Meisner, J.D.
Chief Legal Officer & Corporate Secretary
Derek Meisner, J.D., serves as Chief Legal Officer and Corporate Secretary at X4. Mr. Meisner brings more than two decades of experience providing counsel to public and private companies across key legal and operational functions, including regulatory compliance, debt and equity financings, mergers and acquisitions, strategic partnerships and corporate governance. Most recently, Mr. Meisner held the role of General Counsel at Genocea Biosciences, a Cambridge-based, publicly traded, clinical-stage biopharmaceutical company. Prior to Genocea, he served as General Counsel of multiple Boston-based financial services firms, including prominent life science investor RA Capital Management, and he was previously a partner at the international law firm K&L Gates and Branch Chief in the Division of Enforcement of the U.S. Securities and Exchange Commission. Mr. Meisner holds a B.A. from the University of Michigan and a J.D. from the Washington College of Law at American University. Read More
Mary DiBiase, PhD
Chief Operating Officer
Previously, Dr. DiBiase was the Senior Vice President of Technical Operations and Quality at X4. She has more than 20 years of drug development and technical operations experience in both large and small organizations holding leadership roles in technical development, product operations and program management. Prior to X4 she was VP Technical Operations and Program Management at Epirus Biopharmaceuticals, a small biosimilar company working to expand access to biosimilar products across the globe. Other professional roles include VP Product Operations, Specialty Care Business Unit for Pfizer Global Supply, and multiple positions of increasing responsibility at Biogen including Sr Director CMC Management, Program Executive for Avonex® and Associate Director Pharmaceutical Science and Technology. Dr. DiBiase received her PhD from the University of Rhode Island and her B.Pharm. from the University of London. Read More
Shariq Ali, PhD
Vice President, Medical Affairs
Dr. Ali is Vice President of Medical Affairs at X4 Pharmaceuticals. He has more than a decade of experience leading teams to launch transformative therapies across a diverse set of disease areas, including rare diseases and rare hematological disorders. Previously, Shariq served as VP of Medical Affairs at Wave Life Sciences, where he helped build and establish the medical affairs organization, to prepare for launching a potential therapy for Duchenne muscular dystrophy (DMD). In addition, Dr. Ali spent several years leading various aspects of the medical function for Sanofi Genzyme’s Rare Diseases and Rare Blood Disorder franchises, and prior to that, he was part of the medical team at Alexion Pharmaceuticals responsible for launching Soliris for patients living with Paroxysmal Nocturnal Hemoglobinuria (PNH). Dr. Ali has also held faculty and department chair appointments at A&M Schwartz College of Pharmacy & Health Sciences, Long Island University, and the Touro College of Pharmacy. He received his PhD in pharmacology from New York Medical College and completed his post-doctoral training at Cornell University Medical College. Read More
Mihaela MacNair, PhD
Vice President, Regulatory Affairs
Dr. MacNair is the Vice President of Regulatory Affairs at X4. She has over 20 years of global experience in the pharmaceutical industry having worked in Regulatory Affairs roles of increasing responsibility in the European Union and the US. Her regulatory expertise with early and late-stage product development, registration and life-cycle management in rare diseases is well-aligned with X4 Pharmaceuticals’ pipeline. Prior to joining X4, Dr. MacNair was Vice President of Regulatory Affairs at Atea Pharmaceuticals. Previously, she worked as Therapeutic Area Regulatory Lead at Biogen where she oversaw several portfolios of assets in neuromuscular diseases, including amyotrophic lateral sclerosis and spinal muscular atrophy, in neurodegeneration and dementia, including Alzheimer’s disease, and in movement disorders such as progressive supranuclear palsy. Prior to Biogen, Dr. MacNair held leadership positions in Global Regulatory Strategy at Shire Pharmaceuticals in lysosomal storage diseases and served as the General Manager of the Voisin Consulting Life Sciences US office in Cambridge, MA. Dr. MacNair holds a Ph.D. in Spectrochemistry from the University of Paris 7, an M.Sc in drug development and registration from the University of Paris 11, and an M.Sc in organic chemistry from Universitatea Politechnica Bucharest. Read More
Brian Bowersox
Vice President, Finance
Mr. Bowersox has more than 15 years of progressive experience in finance and accounting functions, leveraging capital allocation and business transformation initiatives while helping to maximize profitability and enterprise value. Mr. Bowersox previously served in a similar role as a corporate controller at a Massachusetts-based life sciences company, Abpro, where he provided strategic financial counsel to corporate management and business partners across all functions of the organization, including business development valuations, systems implementation and optimization, annual planning and projections and effective accounting policies and principles. He received his Master’s in Business Administration at Southern New Hampshire University and his Bachelor’s in Accounting at Bryant University. Read More
Michele Rhee, MPH, MBA
Vice President, Patient Affairs and Advocacy
Michele Rhee is Head of Patient Affairs and Advocacy of X4 Pharmaceuticals. She has more than a decade of experience leading patient affairs and advocacy across pharmaceutical and nonprofit industries. Michele is embedded within the rare disease and oncology patient communities through both her extensive professional work and her personal experience with a cancer diagnosis at age 20 and rare disease diagnosis at age 21. Partnering with these communities, she has led patient interviews/advisory boards and represented the patient perspective, which has directly informed trial design, patient support services, and disease education programs, among other efforts. Michele previously served as Head of Patient Affairs at Enzyvant where she helped build the Patient Affairs function, developing and maintaining both global patient advisor and advocacy partnerships across disease areas. During her time there, the company was nominated for a Global Genes 2019 RARE Champions of Hope award, in part, due to its expanding efforts in Patient Advocacy. Prior to her work at Enzyvant, Michele served as Global and R&D Patient Advocacy Lead at Takeda Oncology, Head of Global Patient Affairs at Bluebird Bio, and Director of both Strategic Initiatives and Program Initiatives at the National Brain Tumor Society. In addition, Michele has served as Chair of the MassBio Patient Advocacy Roundtable since 2017, is a founding board member for Costs of Care, an organization dedicated to helping clinicians and health systems deliver better care at lower cost, and was named a 2019 PharmaVOICE 100 honoree. Michele received her MPH from Yale School of Public Health and her MBA from Yale School of Management. Read More
Marie Green
Vice President, Program Executive
Marie Green, Ph.D. is the Vice President, Program Executive at X4. She has more than 20 years of comprehensive drug development experience in the pharmaceutical and biotechnology industry, leading cross-functional global drug development teams at small and large companies alike in multiple therapeutic areas with biologics, small molecules and vaccines. Prior to joining X4, Dr. Green served as the Tuberculosis vaccines and Malaria monoclonal antibody and vaccines Program Team Leader at the Bill and Melinda Gates Medical Research Institute. Throughout her career, she has also held the titles of Executive Director, Portfolio Management and Assessment at TESARO, Inc. and Program Executive at Sesen Bio. Dr. Green was instrumental in building several small start-up biotech companies, including Eleven Biotherapeutics (now Sesen Bio), Constellation Pharmaceuticals and Taligen Therapeutics (now Alexion Pharmaceuticals). Dr. Green began her career in the Bioassay group at Biogen before going on to building out the Bioassay group at Millennium Pharmaceuticals (later acquired by Takeda Oncology) where she then transitioned into a Program Executive. Marie received her Ph.D. in Immunology from the Tufts School of Biomedical Sciences and completed an American Cancer Society post-doctoral fellowship at Harvard University in the Department of Genetics. Read More

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