Even when a drug is tremendously lucrative—in fact, especially when a drug is tremendously lucrative—the drugmaker is always selling on borrowed time, conscious that at some fixed point in the future the patent will expire and the generics will come rushing in to decimate profits. There’s a phrase used in the pharmaceutical business to describe this inevitable but terrifying stage in the process. They call it “the patent cliff,” because that’s what a graph of revenue resembles at the moment when the patent expires: a drop so steep it’s like plummeting off a cliff.
