Roche has announced that its majority stockholders, the Hoffmann and Oeri families, have extended a ‘pooling agreement’ to retain their combined shareholding in the Swiss major, thus effectively ending any possibility of a takeover bid.

The agreement, which was due to expire at the end of 2009, has been extended indefinitely. The families, who are the descendants of founder Fritz Hoffmann-La Roche, own just over 50% of the bearer shares in the Basel-based group, ie the ones that come with voting rights.

Roche chairman Franz Humer said that the pool extension “represents an important affirmation of the long-term commitment of our majority shareholders to an independent development of the company. He added that “particularly in these economically turbulent times we are very happy being able to count on such a highly stable group of shareholders keen in the long-term success of Roche”.

Since Pfizer’s move to acquire Wyeth at the beginning of the week, merger mania has reared its head again and Roche, with its attractive pipeline, was seen in some circles as a possible target. Novartis has a 33% stake in its fellow Swiss firm and in the past chief executive Daniel Vasella has spoken hypothetically about how strong a Roche/Novartis combination could be.

However the likelihood of that ever happening was remote and the extension of the pooled agreement pretty much rules it out. Now all eyes will be on Roche’s proposed purchase of the 44% of Genentech it does not own. Its $43.7 billion offer was rejected by the US biotechnology giant and observers are waiting to see how Roche will finance any deal.