4. Mallinckrodt/Questcor Pharmaceuticals

Deal value: $5.6 billion
Deal status: Closed

Mallinckrodt ($MNK) became a standalone drug company last year when it was spun off from devicemaker Covidien ($COV). Chief Executive Officer Mark Trudeau wanted to reduce his new company's dependence on medical imaging and decided on specialty pharmaceuticals. In February, Mallinckrodt snatched up Cadence Pharmaceuticals ($CADX) and its rapidly growing specialty pain drug Ofirmev for $1.3 billion. A month later it bagged Questcor, essentially another one-drug move, for $5.6 billion.

That one drug is the autoimmune treatment, H.P. Acthar Gel, one of the most expensive drugs in the world. Not only did it get that drug, but it also taps Questcor's experience at pricing specialty drugs, which has been controversial. When Questcor bought rights to the drug, a hormone-based drug derived from pig pituitary glands, from Sanofi Aventis in 2001, it ran about $40 per vial. In 2007, its price was up to $23,000 per vial, and by last year it was up 9% to $205,681 for a year's treatment course. It was the fifth most expensive drug in the world last year. It had $760 million in sales in 2013, up 50%.

All of these machinations have attracted some attention. There was a 2012 probe into its marketing and more recently an acknowledgement that the drug has been tied to 3,100 adverse events reports in about three years, including 20 deaths. There were also attacks by short sellers, but they lost out when Mallinckrodt swept in with its $5.6 billion bid.

For more:
Special Report: The top 10 most expensive drugs of 2013 - H.P. Acthar Gel
Mallinckrodt bets $5.6B on Questcor and its controversial Acthar drug
Questcor, short sellers trade attacks
Mallinckrodt expands pain portfolio with Cadence acquisition
With $135M rights deal, Questcor locks up rival to its pricey Acthar drug

-- Eric Palmer (email | Twitter)

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4. Mallinckrodt/Questcor Pharmaceuticals