CSL Limited (ASX:CSL) is in talks to buy Vifor Pharma AG (SWX:VIFN) for around $7 billion, according to Australian media. The target's sickly share price makes the pounce timely, although the returns look paltry unless Chief Executive Paul Perreault can unearth lots of synergies. A looming patent expiry for one of Vifor's key drugs adds to the unknowns.