Roche Holding AG said Wednesday it has completed its Genentech acquisition, setting up Genentech CEO Arthur Levinson as the chair Genentech’s new board.

Roche bought the biotechnology company for $46.8 billion, or a 56 percent share. The new new Chief Executive Pascal Soriot will all the operations in United States.

The move, effective May 1, will put Mr. Levinson and Mr. Soriot in charge of efforts to combine the companies, with a goal of finishing the integration and the Genentech’s operation by the end of 2009.

Analysts have debated how Roche would take the management of the pioneering biotechnology, whose science-based corporate culture has long drawn successful products.

Soriot, 49, a well trained veterinary surgeon and holds an M.B.A. joined Roche in 2006, while Levinson, 59, is a senior scientist sand a Ph.D. biochemist who spent his entire career at Genentech, moving up through R&D since 1995.

Shares of Roche fell 17 cents to 52 cent percent at $32.65 or 154 Swiss francs in midday trading.