December 18, 2001 — THOUSAND OAKS, CA — Amgen and Immunex Corporation have signed a definitive agreement providing for Amgen to acquire Immunex, biotechnology’s inflammation leader, for $16 billion in stock and net cash.

Under the terms of the agreement, each share of Immunex common stock will be exchanged for a fixed-ratio of 0.44 shares of Amgen common stock, and cash of $4.50, or a total of 85% in stock and 15% in cash.

“This is a compelling strategic transaction and an excellent opportunity for the shareholders, employees and partners of both companies, and we expect it will generate significant benefits for hundreds of thousands of patients around the world,” said Kevin Sharer, chairman and CEO of Amgen.

With the acquisition, Amgen expects to accelerate its five-year annual percentage growth in product sales to the low 30s from the low 20s, and accelerate its annual growth in cash EPS to the mid-20s from the low 20s. Amgen will have pro forma 2002 revenues of approximately$5.5 billion and 2002 net income in excess of $1.5 billion.