Roche's influential Chairman Franz Humer said on Tuesday he will not stand for re-election next year when he will have served 16 years at the helm, potentially accelerating a shift of emphasis towards the Swiss drugmaker's U.S. operations.

"Roche is in excellent shape and well positioned to meet future challenges. This is a good time to hand over to a successor," Humer, 66, said in a surprise announcement at the company's annual general meeting in Basel.

Humer, who has joint Swiss and Austrian citizenship, was the driving force behind the takeover in 2009 of U.S. biotech company Genentech, which has produced some of Roche's top-selling cancer medicines and helped it avoid the pain of patent expiries ravaging many rivals.

A top candidate to replace Humer is Genentech and Apple chairman Arthur Levinson, who analysts say would pursue Humer's strategy of focusing on innovation but might push the company's centre of gravity further across the Atlantic.

"If it is Art Levinson, then chances are that innovation will remain the core. And our hypothesis that the Roche-Genentech deal was a reverse takeover and about Genentech going global would be complete," said Vontobel analyst Andrew Weiss.

Since the deal, Genentech's scientists in San Francisco have been driving the development pipeline of the 116-year-old Basel-based firm, casting a shadow over Roche's own research operations.

The world's largest maker of cancer drugs said it would nominate a successor in the autumn and said it would keep the offices of chairman and chief executive separate in future.

Hands-on chairman

Roche is banking on a new generation of cancer drugs, including breast cancer treatment Perjeta which won European approval on Tuesday, to drive sales growth and fend off competition from expected copies of its biotech drugs.

It expects sales and earnings to grow this year in contrast to cross-town rival Novartis, which forecast a fall in profit and also has a new chairman replacing Daniel Vasella who stepped down after 17 years at the head of the company.

Since relinquishing the job of chief executive at Roche, which he held for a decade to fellow Austrian Severin Schwan in 2008, Humer has remained a hands-on chairman and was heavily involved in last year's bid to buy gene-sequencing company Illumina.

Roche walked away from a $6.8 billion hostile offer for the U.S. company last April, refusing to meet Illumina's demand to pay more.

"Roche does not make acquisitions that don't create value. It never has, and never will," Humer told shareholders on Tuesday.

Meanwhile his departure could raise questions about whether Roche might consider developing biosimilars - copies of its biotech drugs which Humer is said to have been opposed to but which CEO Schwan has reportedly raised as a possibility.

Humer has a famously close relationship with Roche's founding Hoffmann-Oeri family, which still has a controlling stake in the company's voting shares and likes its managers to stick around.

Born in Austria in 1946, Humer studied law at Innsbruck university and started his career in pharmaceuticals as a general manager at Schering Plough in 1973.

He worked at Glaxo Holdings from 1981 to 1995, when he joined Roche as head of the pharmaceuticals division. He rose to chief operating officer in 1996 and chief executive in 1998.

From 2001 he held the joint role of CEO and chairman until fellow Austrian Severin Schwan took over as CEO in 2008. On Tuesday, Schwan was elected to the company's board.

A patron of opera, Humer is also non-executive chairman of spirits group Diageo, a member of the boards of Citigroup and Allianz, as well as chairman of business school INSEAD.