Sanofi is girding itself for an ugly year, forecasting a 12%-15%  drop in business earnings per share for 2012 as the company absorbs the loss of patent exclusivity on a stable of drugs that brought in more than €4 billion last year.

Already reeling from patent expirations for Lovenox, Ambien CR and Taxotere in the US and Plavix and Taxotere in the EU, the company will soon be hit with generic competition on Avapro and Eloxatin, which loses US exclusivity in August.

“This is the year we’ve all had circled in red on our diaries for a number of years now,” said CEO Chris Viehbacher. “We have a number of headwinds facing us.”

Sanofi’s diabetes business was a bright spot in 2011, with sales up 12.5% to €1.2 billion in the fourth quarter. Emerging markets sales rose 19% for the quarter compared to the same period a year ago.

Sanofi acquired Genzyme in April, and that part of the company’s business, which was reeling from manufacturing problems, is on the mend. Viebacher said the merger is going smoothly and that he sees “a growing sense of confidence and trust among people” at both the firm’s ex-Genzyme Boston-area operations and in Europe.

Bernstein analyst Tim Anderson rated the stock “Overperform,” saying “financial performance will be strained because of patent expirations, but consistent revenue and EPS growth seems to return from 2013 onwards, and we feel that as this return-to-growth period draws closer, Sanofi’s valuation will expand. What distinguishes Sanofi from many of its peers is that there is a fairly well-defined end to its patent cliff which annualizes in 2013.”