In 1981, Immunex Corporation was founded by Stephen Duzan, and Christopher Henney and Steven Gillis from the Hutchinson Cancer Research Center. Immunex became publicly traded in 1983. In 1991, Immunex won FDA approval to market Sargramostim (Leukine) in the U.S. to treat bone marrow transplant patients, and in 1998 won FDA approval to market Etanercept (Enbrel) for treatment of moderate to severe rheumatoid arthritis. The company was acquired by Amgen in 2001 for $16 billion.