Leonard Schleifer, MD, PhD

Early Life and Inspiration

Len 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, a top scientist from Columbia University, as co-Founder, along with 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, neurological diseases, hematologic conditions, infectious diseases, and rare diseases.

Regeneron is among the few pharmaceutical companies with the expertise and technologies to rapidly respond to global public health emergencies. The company pioneered the first effective antibody cocktail treatments for both COVID-19 and Ebola, collectively benefitting millions of people worldwide. In September 2025, Regeneron demonstrated its commitment to global health by announcing a donation of up to 500 doses of its Ebola treatment to the World Health Organization, specifically for use by governments in low- and lower-middle income countries. Simultaneously, the company rushed a delivery of doses and personal protection equipment (PPE) to the Democratic Republic of the Congo (DRC) to immediately address a rapidly escalating Ebola outbreak. These achievements, according to Len, are the result of decades of strategic investments in technologies that generate antibodies that, when directed toward a virus, could become an effective treatment approach.