Leonard Schleifer

Leonard S. Schleifer, M.D., Ph.D. is an American physician, neuroscientist, and biotechnology executive who co-founded Regeneron Pharmaceuticals, Inc. in 1988 and has served continuously as its president and chief executive officer.

A licensed neurologist certified by the American Board of Psychiatry and Neurology, Schleifer earned a B.A. from Cornell University and both an M.D. and a Ph.D. in pharmacology from the University of Virginia before transitioning from academic neurology at Weill Cornell Medical College to entrepreneurship. Under his leadership, Regeneron advanced genetic engineering and monoclonal antibody technologies to yield multiple FDA-approved therapies, including the vascular endothelial growth factor inhibitor Eylea for wet age-related macular degeneration and the interleukin-4 receptor antagonist Dupixent for severe atopic dermatitis and asthma, both achieving blockbuster status with annual sales exceeding $1 billion.

Schleifer's strategic recruitment of co-founder George D. Yancopoulos, M.D., Ph.D., as chief scientific officer catalyzed Regeneron's focus on translating basic neuroscience into therapeutics, culminating in pioneering antibody cocktails like REGEN-COV for COVID-19 and treatments for Ebola. The company's pipeline now encompasses over a dozen investigational candidates targeting oncology, immunology, and rare diseases, reflecting Schleifer's emphasis on rigorous scientific validation over short-term market pressures. He also holds a clinical professorship in neurology and neuroscience at Weill Cornell and received the Biotechnology Heritage Award in 2025 for advancing biopharmaceutical innovation.