Amgen has announced that Dennis Fenton, executive vice president of operations, will retire at the end of the year. Fenton, 55, has worked for Amgen for 25 years. One of the company’s longest-tenured staff members, Fenton joined Amgen during its first 12 months of existence. A research scientist by training, Fenton has worked in and led virtually every part of Amgen, including research, process development, sales and marketing, engineering and manufacturing. Dr. Fabrizio Bonanni will succeed Fenton. Bonanni has been Amgen’s senior vice president of manufacturing, overseeing the company’s site operations and contract manufacturing, since March 2003. He has previously served as Amgen’s senior vice president of quality and compliance and as a corporate compliance officer. Madhu Balachandran, who was previously vice president of operations at Amgen Manufacturing Ltd. in Puerto Rico, will succeed Bonanni.