Leonard S. Schleifer, MD, PhD

Board co-Chair, President and Chief Executive Officer

Contact: [email protected]

Headshot of Leonard S. Schleifer, M.D., Ph.D. wearing a blue shirt.

Published: June 2023

Leonard S. Schleifer, M.D., Ph.D., has built and managed Regeneron since 1988, alongside his co-Founder George D. Yancopoulos, M.D., Ph.D. He is currently board co-Chair, president and chief executive officer of Regeneron.

Early Life and Inspiration

Leonard S. Schleifer, M.D., Ph.D., grew up in Queens, New York, with parents and teachers who sparked his passion for science and entrepreneurship from a young age. He earned his M.D. and Ph.D. in Pharmacology from the University of Virginia and became a licensed physician certified in neurology. While working as a practicing neurologist and professor at Cornell Medical School, Len became frustrated with the lack of effective treatments for patients with serious neurodegenerative diseases like Parkinson’s and Alzheimer’s. He wondered if new biotechnologies could be harnessed to potentially make an impact for these people, their families and many others.

Regeneron Founding

Len founded Regeneron in 1988, with the vision of creating a company built entirely on science, where scientists are the heroes, and everyone works toward the common goal of helping patients. He knew he needed a top-notch team and immediately recruited George D. Yancopoulos, M.D., Ph.D., a top scientist from Columbia University, as co-Founder, as well as Nobel Laureates to the Board of Directors. Len's dream is now a reality, and the Regeneron team is using its scientific prowess to consistently and repeatedly bring new medicines to people in need.

Scientific Innovation

Regeneron maintains the proud distinction of being one of the most innovative biotechnology companies in the world, with numerous FDA-approved medicines and product candidates in development, almost all of which are homegrown in the company’s laboratories. Regeneron's medicines and pipeline are designed to help patients with eye diseases, allergic and inflammatory diseases, cancer, cardiovascular and metabolic diseases, hematologic conditions, infectious diseases, and rare diseases.

Regeneron was one of the first pharmaceutical companies to develop an effective antibody treatment for COVID-19, which helped millions of high-risk patients. The company previously developed an effective treatment for Ebola in rapid response to an outbreak, which laid the foundation for COVID-19 efforts. Len attributes these successes to decades of investments in technologies to generate antibodies, that when directed toward a virus, could become an effective treatment approach.

The Real Healthcare Problem

We are taking the long view by investing in innovation to tackle society's biggest health challenges.

Read About Our Approach

Corporate Responsibility

Inspired by the words of his father, Len has always strived to “do well by doing good,” which at Regeneron includes extending the company’s success and impact through excellent corporate citizenship and a commitment to fostering the next generation of STEM (Science, Technology, Engineering and Math) leaders. Regeneron’s team uses their unique knowledge and expertise to benefit society, the economy and the environment.

Awards & Recognition

Under Len’s leadership, Regeneron has been lauded as a top company to work for by Science magazine, Fortune, Forbes, Fast Company and others. It has also been recognized for its commitment to corporate responsibility through inclusion in the Dow Jones Sustainability Index and Civic 50 list of most community-minded companies, among others. In recent years, Regeneron has also been recognized for its pandemic response by organizations including Fast Company’s World Changing Ideas.

In 2019, Len was elected as a Fellow by the American Association for the Advancement of Science (AAAS). He has been recognized by Barron’s Best CEOs and as an Ernst & Young’s Entrepreneur of the Year, alongside Dr. Yancopoulos.

Reflecting on Achievements

For nearly 35 years, our mission has been to use the power of science to bring new medicines to patients. To achieve this, we seek to constantly improve the drug discovery and development process by applying our homegrown technologies, deep understanding of science and relentless spirit.

2021 Achievements video thumbnail featuring Leonard S. Schleifer, M.D., Ph.D. 2021 Achievements video thumbnail featuring Leonard S. Schleifer, M.D., Ph.D.

Professional Experience

  • co-Founder, President and Chief Executive Officer, Regeneron (1988-Present)
  • Chairman, Regeneron (1988-1995)
  • Clinical Professor of Neurology and Neuroscience, Department of Neurology, Weill Cornell Medical College (1992-Present)
  • Board co-Chair (2023-Present)


  • Doctor of Philosophy in Pharmacology at University of Virginia
  • Doctor of Medicine in Pharmacology at University of Virginia
  • Bachelor of Arts at Cornell University

Highlights of Honors & Awards

  • Prix Galien Roy Vagelos Pro Bono Humanum Award (2021)
  • Crain’s New York Notables in Healthcare (2021)
  • Walter Reed Distinguished Achievement Award (2020)
  • Forbes America’s 100 Most Innovative Leaders (2019)
  • Cornell Entrepreneur of the Year (2019)
  • Legends in Leadership Award, Yale School of Management, CEO Institute (2017)
  • Ernst & Young Life Sciences Entrepreneurs of the Year National Award (2016)
  • Barron’s World’s Best CEOs (2016)
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