Bristol-Myers Squibb (NYSE:BMY) changed its huge patent cliff into two smaller falls with a larger ledge in the middle. It's a good deal for the company, but it doesn't fix the ultimate problem: hitting the bottom is going to hurt.

Bristol-Myers was expected to lose both blood thinner Plavix, which it sells with sanofi-aventis (NYSE:SNY), and its antipsychotic Abilify almost on top of each other; a major hit considering the two combined accounted for over 37% of sales last year. Plavix will go off patent at the end of 2011 and Bristol-Myers' agreement with Otsuka Pharmaceutical to market Abilify was set to expire about a year later.

In order to shorten the cliff's fall, Bristol-Myers announced yesterday that it was extending its agreement with Otsuka until 2015 when the patent on Abilify expires. Bristol-Myers will pay $400 million up front for the pleasure and reduce its share of the revenue, currently at 65% but ramping it down to about 51%. On the other hand, Otsuka will begin to pick up some of the tab for marketing Abilify.

The patent cliff that almost every drugmaker is facing is the dark side of developing blockbuster drugs. Be it Pfizer's (NYSE:PFE) Lipitor, Eli Lilly's (NYSE:LLY) Zyprexa, or AstraZeneca's (NYSE:AZN) Nexium, it's going to hurt when the drugmakers start to face generic competition. Fortunately, investors can see the patents coming and the loss of revenue won't be a shock, unlike when Merck (NYSE:MRK) had to suddenly pull Vioxx off the market prematurely.

With the cliff in plain sight, share prices will be determined by what the companies do between now and their rapidly approaching fall. Adding a parachute in the form of marketing deals like this one along with its developmental-stage deal with Exelixis (NASDAQ:EXEL) should help Bristol-Myers. It certainly has the cash to keep arranging them.

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