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. From August 2012 to September 2014, 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, from January 2007 to August 2012, 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. 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
Adam S. 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, from June 2016 to August 2018. Prior to that, Mr. Mostafa was a managing director in the healthcare investment banking group at Cantor Fitzgerald from January 2015 to May 2016, and from June 2011 to January 2015, Mr. Mostafa 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 from March 2007 to May 2011, and from September 2003 to March 2007, Mr. Mostafa was a portfolio management associate in the global stock selection group at AQR Capital. Mr. Mostafa 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
E. Lynne Kelley, M.D., FACS
Chief Medical Officer
Dr. Kelley is the Chief Medical Officer at X4. She brings more than a decade of experience directing clinical development and global expansion of novel pharmaceutical products at both emerging and established life sciences companies. Dr. Kelley is a Board Certified General and Vascular Surgeon. Before joining X4, Dr. Kelley was chief medical officer (CMO) of Massachusetts-based biopharmaceutical company Histogenics Corporation, where she led the development of restorative cell therapies to replace damaged cartilage and oversaw the completion of a Phase 3 clinical trial and regulatory submission for the company’s lead program. Dr. Kelley previously served as CMO of Senseonics Holdings, Inc. and held leadership positions in clinical development roles at global companies such as Becton, Dickinson and Company, Kimberly-Clark Corporation, and Boston Scientific Corporation. Dr. Kelley received her medical degree from Dartmouth Medical School and her bachelor’s degree in biology from Boston University. She trained at Dartmouth Hitchcock Hospital and Massachusetts General Hospital, and was a practicing surgeon at Yale University. Dr. Kelley was named Fellow of the American College of Surgeons, was awarded an NIH research grant at Harvard and the Marco Polo Fellowship studying at Hospital Henri Mondor of the University Paris Hospital System, and has authored numerous articles for peer-reviewed publications. Read More
Mary DiBiase, PhD
Vice President, Technical Operations and Quality
Dr. DiBiase is 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
Celeste DiJohnson
Vice President, Clinical Operations
Ms. Celeste DiJohnson is Vice President of Clinical Operations at X4. Ms. DiJohnson brings over 25 years of industry experience in small and large biotechnology companies and has held senior leadership roles in clinical operations and global program development and has significant success in building and leading high performing clinical development teams with broad organizational impact. She worked in multiple orphan indications in the therapeutic areas of neurology, oncology, and rare disease while at Cephalon, Sanofi Genzyme, and Sarepta, respectively. While at Sarepta, Ms. DiJohnson was instrumental in the development and approval of EXONDYS 51® (eteplirsen injection) for genetic mutations amenable to exon-skipping, which was approved by the FDA for Duchenne Muscular Dystrophy in 2016. Ms. DiJohnson received her BS degree in Biology from Shippensburg University and a Master of Psychology degree from Immaculata University and is active in her community. Read More
Tarek Ebrahim, MD
Vice President Medical Affairs, Rare Disease
Dr. Ebrahim is Vice President Medical Affairs, Rare Disease at X4. He has 17 years of extensive experience in rare diseases and a strong presence among thought leaders in the U.S. and globally. Most recently, as Executive Director, he led the Paroxysmal Nocturnal Hemoglobinuria (PNH) global team in Alexion Pharmaceuticals, where he successfully implemented effective patients’ identification strategies and medical marketing educational programs. Prior to Alexion, he spent 13 years in Genzyme/Sanofi leading U.S. and global multi-disciplinary teams focusing on developing evidence-based data for physicians’ communication and patient engagement in the field of Lysosomal Storage Disorders (LSDs). He supported global medical affairs to develop the first published therapeutic goals and disease management guideline for a rare genetic disease. He managed new product development, integrated product launches and oversaw brand management. At X4, Dr. Ebrahim is leading our medical affairs strategy, patient enrollment engagement and drive key thought leadership partnerships. He earned his bachelor’s degree in medicine and surgery from Alexandria University in Egypt, where he also received training as an anesthesiologist and the designation of Diplomat of Public Health. Read More
Leif-Ann Tuohey
Vice President, Head of Business Development
Ms. Tuohey is Vice President and Head of Business Development at X4. She joined X4 to lead its business development activities in 2017. Ms. Tuohey has more than 15 years of biopharmaceutical experience and has held strategic and transaction-focused corporate and business development roles in startups and publicly traded biotechs, as well as at large multinational and specialty pharmaceutical companies. From 2011 to 2016, Ms. Tuohey held key roles in business and corporate development activities at Infinity Pharmaceuticals. During her tenure, she was responsible for leading out-licensing and in-licensing initiatives and helped hone its corporate strategy. Ms. Tuohey began her career as a life science strategy consultant at Health Advances, LLC and co-founded MEND, a Gates Foundation-backed non-profit biotech, while in college. She has an A.B. in biochemical sciences from Harvard College and an M.B.A. from Harvard Business School. Read More
Ronny Mosston, MBA
Vice President of Human Resources
Ms. Mosston is the Vice President of Human Resources at X4. She has held leadership positions in leading biotechnology and life sciences companies for over 20 years in Human Resources and Patient Advocacy/Engagement roles for several leading public bio-technology companies in oncology, rare disease and infertility. In addition to senior positions in Millennium Pharmaceuticals, Takeda, and OvaScience, Ms. Mosston has provided consulting services to the Executive Teams of several leading public and private biotechnology companies to help build their Patient Engagement and Human Resources strategies to align with their business and cultural goals. Prior to working in life sciences, she was a Partner and Chief Operating Officer of a Boston based staffing and executive search company which became publicly traded and was acquired by a top global Human Resources consulting companies. She is the past co-chair and serves on the Dana Farber Patient and Family Advisory Council, the Vice Chair of the Joe Andruzzi Cancer Foundation, a founding member of the MassBIO Patient Advocacy Committee and a member of the Healthcare Businesswomen’s Association (HBA). Ms. Mosston received her BS in Biology and her MBA, in Human Resources Management from Boston University and is active in the community. Read More
Nic Scalfarotto, DVM
Vice President, Regulatory Affairs and Program Management
Dr. Scalfarotto has served as Vice President, Regulatory Affairs and Program Management since November, 2018. With over 25 years of experience at biopharmaceutical companies and clinical research organizations, he has held executive roles covering multiple stages of development including solutions for treating rare and ultra-rare diseases. His experience has spanned diverse development programs covering small molecules, novel biologics, biosimilars, bio-betters, follow-on biologics, imaging agents and combination products. Initially focused on preclinical development, his regulatory career evolved in small and large corporate settings including PAREXEL, Millennium, Bristol-Myers, Eurand, Momenta, EMD Serono and GE Healthcare. He has been responsible for global regulatory development, in multiple therapeutic areas including Cardiology, Oncology, Immunology, Endocrinology, Gastroenterology, Dermatology, Rheumatology, Neurology and Biomarker development, as well as, support of licensing activities. Most recently, he held the position of Senior Vice President, Regulatory Affairs at Aegerion Pharmaceuticals, focusing on the development of products targeting rare metabolic diseases. Additionally in prior positions at three CROs (MetTrials, Chrysalis and Oread), Dr. Scalfarotto held General Management positions with encompassed such responsibilities as strategic and tactical planning, finance, operations, business development, regulatory affairs, quality assurance, information systems and facilities planning. Dr. Scalfarotto holds an undergraduate degree in biological sciences from Seton Hall University and a degree in Veterinary Medicine from the University of Bologna. Read More

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