Leonard S. Schleifer, born in 1953 in Queens, New York, is an American businessman and the co-founder and chief executive of Regeneron Pharmaceuticals. He earned a B.
S. from Cornell University and an MD-PhD from the University of Virginia, where he studied under Nobel Laureate Alfred G. Gilman.
Following his doctoral studies, he trained as a neurologist and served as a junior faculty member at New York Hospital.