George Rathmann, 84, who as founding CEO took Amgen Inc. from a small company with an unclear mission in a strange new field and helped turn it into the world's largest biotech drugmaker, died Sunday of complications from pneumonia at his home in Palo Alto, Calif.

Amgen, based in Thousand Oaks, Calif., announced Mr. Rathmann's death Monday in a statement.

Convinced in the 1970s that gene splicing would become hugely important, Mr. Rathmann set out to make it so. As chief executive officer of Amgen from 1980 to 1988, he developed two blockbuster drugs that made the company's name and have remained its best sellers: Epogen for anemia and Neupogen for cancer patients undergoing chemotherapy.

"George Rathmann was a biotechnology giant, and we were privileged to have him as our first CEO. George's vision and values are as alive today at Amgen as they were when he led the company," said Kevin Sharer, chairman and chief executive of Amgen.

One of Mr. Rathmann's main accomplishments was finding the funds Amgen needed during its start-up years, according to a statement on the company's website. Nicknamed the "Golden Throat" by friends who admired his persuasiveness, he secured venture capital, built revenue streams through partnerships, and guided Amgen through its first public offerings.

After leaving Amgen, Mr. Rathmann became CEO and chairman of Seattle-based biotech ICOS Corp. (later acquired by Eli Lilly). He later served as chief executive and chairman of the genomics company Hyseq Inc.

— AP