On Dec. 17, 2001, the acquisition of Immunex by Amgen was announced for $16 billion in stock and net cash. Immunex, the largest biotechnology company in the Pacific Northwest, was founded by Steven Gillis and Christopher Henney from the Fred Hutchinson Cancer Research Center, and Stephen Duzan, former CEO of Cello Bag Co. (sold to ARCO Chemicals), and North Star Ice Equipment Corp. The Amgen acquisition closed in July, 2002.

Immunex became publicly traded in 1983, and in 1991, with U.S. Food and Drug Administration (FDA) approval of the drug Leukine, it became only the third fully integrated pharmaceutical company to be created in the U.S. since 1945.