Shire P.L.C. announced today that Matthew Emmens will step down as chief executive officer in June. He will be succeeded by Angus Russell, Shire's chief financial officer since 1999.

Board member James H. Cavanaugh, 70, will retire as non-executive chairman in June, and Emmens, 56, will succeed him as chairman. Emmens has been CEO since 2003.

Russell, who is British and is currently looking for a permanent residence in the Philadelphia area, will spend two-thirds of his time in the United States and one-third of his time in Basingstoke, a Shire spokesman said.

Emmens, an American who lives in Malvern, spent three-quarters of his time as CEO in the Philadelphia area and one-quarter of his time in England.

Russell has worked 27 years in the pharmaceutical industry, including at ICI, Zeneca and AstraZeneca in finance, strategy and marketing. In his eight years at Shire, he devised and implemented Shire's long-term business strategy, the company said.

Shire, Britain's third-largest drug maker behind GlaxoSmithKline P.L.C. and AstraZeneca, announced plans in July to expand its U.S. headquarters in Tredyffrin Township, Chester County, to support its pipeline of specialty drugs that target rare diseases and growing sales in its core attention-deficit hyperactivity disorder drug business.

Shire, based in Basingstoke, outside London, has more than 600 full-time employees at the Chesterbrook Corporate Center and plans to add 390 workers over the next four years.

Shares fell $4.19, or 5.9 percent, to $66.40 on the Nasdaq.