He previously cofounded, and was CEO and chairman of, ViroPharma Incorporated, a pharmaceutical company.
From 1983 to 1994 Nash served as vice president for infectious disease and oncology at Schering Plough Research Institute.
During that time, he was involved in the discovery and development of numerous biological agents, antibiotics, and antifungals.
In 1997 Nash co-founded and, until 2000, was chairman, president and CEO of ViroPharma Incorporated, a pharmaceutical company based in Exton, Pennsylvania.
In 2002 he was honored as a distinguished alumnus of the College of Veterinary Medicine and Biomedical Sciences at Colorado State University.