Once upon a time, a long, long time ago, a pharmaceutical company called Sanofi-aventis declared its undying love. Sadly for Sanofi, its love – the alluring Genzyme – was shy, and for a long, long time would not respond to its advances.

Now however the two companies have finally agreed a deal, with Sanofi paying just over US$20 billion, with extra payments a possibility if Genzyme’s MS drug Lemtrada hits certain targets.

The purchase continues the trend of pharma companies buying up biotechs in an attempt to deal with their own, well publicised, problems with pipelines. It also represents the end of a marathon pursuit by Sanofi, which even threatened to try for a hostile take over last year, before finally settling down for a more peaceable chat with its desire.

Will the two-who-are-now-one live happily ever after? Only time will tell. It looks likely to please Genzyme’s shareholders though. The price of $74 a share being paid by Sanofi is a significant hike to previous offers – rumoured to be around $69 – and an even bigger hike on the share price early last year, which was hovering around $50 before the takeover rumours surfaced.