Tero Weckroth, an analyst at Dresdner Kleinwort, has asserted that German-based Bayer has a mid-stage pipeline that could achieve €6bn a year in future sales, with other key experimental drugs potentially worth over €3.5bn annually.

"Together these easily outweigh the EUR3bn risk from patent expiries by 2015," he said.

Weckroth explained that Xarelto (rivaroxaban) and new indications of Nexavar (sorafenib) remain key to the projected €3.5bn of sales from pipeline projects.

Bayer has had to make several difficult decisions since it acquired Schering for €17bn last year, including cutting 6000 jobs - 1400 in R&D - and reducing its pipeline by 30 per cent . However, what is left could leave Bayer as one of the few big pharma firms which won't be too troubled by impending patent expiries.

While this is the case, perhaps it is not surprising that rumours of a possible bid from Novartis surfaced on the trading floor last week. There were whispers that the Swiss drug maker would make a bid of €70 per share for its German neighbour. That values Bayer at over €70bn, which is almost 30 per cent higher than its current market valuation.

Although that price may sound over the top, it is in line with Weckroth's valuation. He has set a buy rating on the stock with a target share price of €67.

Although neither company would comment on the speculation, some analysts were less than convinced. Bankhaus Metzler Seel analyst Karl-Heinz Scheunemann, told Bloomberg news: "Novartis is always good for a rumour. It doesn't appear to be any more than that."

"While Novartis could certainly finance a takeover, it would be difficult to digest a conglomerate. They'd have to have buyers lined up for the plastics and crop treatments units," he concluded.