Greenwich, Conn.-based Aptuit, a contract research organization (CRO), named Timothy (Tim) C. Tyson, a pharmaceutical industry veteran, as executive chairman and acting CEO, replacing Michael A. Griffith, the company’s founder and CEO since 2005. The company said Griffith resigned to pursue other opportunities.

“The Board wishes to thank Mike for his outstanding success in creating a world-class organization that is a trusted partner to hundreds of innovative clients throughout the world,” said Tony Ecock, outgoing chairman of Aptuit’s board of managers. “With 2,700 employees working with more than 800 clients throughout the world, Aptuit has established a solid foundation for continued growth and success.”

Since its founding, Aptuit grew quickly through acquisitions. A year ago, Aptuit acquired the chemical and pharmaceutical development business of German company Evotec AG for $63.9 million. Other acquisitions have included EaglePicher Pharmaceutical Services LLC, SSCI Inc., InfoPro Solutions, Almedica International and three business units of Quintiles.

Aptuit’s interim CEO, Tim Tyson, is the former COO, president and CEO of Valeant Pharmaceuticals International, where he served from 2002 through 2008. Prior to Valeant, Tyson’s pharmaceutical industry experience includes a 14-year tenure at GlaxoSmithKline, where he was president of Global Manufacturing and Supply and ran Glaxo Dermatology and Cerenex Pharmaceuticals.

“Aptuit is uniquely positioned to help innovative partners create the new medicines of tomorrow, and we will work tirelessly to ensure that we do all that we can to help improve the way drugs are developed,” Tyson said.