Franz Humer, 61, steps down as ceo in March to focus on being chairman, and will be succeeded by Severin Schwan, a 40-year-old who heads Roche’s diagnostics unit. The move comes amid criticism of both Roche and Novartis for allowing the same person to remain ceo and chairman. Dan Vasella continues to hold both jobs at Novartis.

Humer, who has been ceo for nearly 10 years and was named chairman in 2001, will also become chairman of Diageo, the big UK drinks company in July. “This is a smooth transition which I’m absolutely convinced will work very well,” Humer tells Bloomberg News. “The board considered now to be a good time for this move because we are under no internal or external pressure to make this transition.”

The move wasn’t expected, though. “The choice of the successor, and the timing are a surprise,” Birgit Kulhoff, pharmaceutical analyst at private bank Rahn and Bodmer in Zurich, tells Bloomberg. She had thought Roche would look outside the company for a candidate, and wasn’t expecting a change for another two or three years.

Schwan, who like Humer is Austrian, has worked at Roche since 1993, when he joined as a finance officer in Basel. And he’ll become ceo as Roche places still greater emphasis on diagnostics as a way toward developing more targeted drugs, as evidenced by is $3 billion hostile bid for Ventana Medical Systems.

“We have important interfaces” between the drug and diagnostic units, Schwan (pictured to the right) tells Bloomberg. “I have been working hard with my pharma colleagues over the last year to improve those synergies and Ventana is very much a result of that.”

Meanwhile, Roche reported a 24 percent increase in first half-net income, thanks to strong sales of its cancer drugs, Avastin and Herceptin. The drug maker says net profit increased to $4.1 billion in the six months ended June 30. Roche also expects both drug and diagnostics to grow at a faster pace than their respective markets.