Drug Studies Limited by Patent Term?

According to a March 9, 2005 article by Matthew Harper in Forbes,com, expensive clinical trials that come just as a drug is losing its patent protection are a real problem for drugmakers:

But though it takes longer and longer to study each new medicine, the patent
clock remains the same. . . . For now, the huge markets that are available mean that drugmakers will keep spending until the bitter end. But after that, unless the government starts funding more clinical trials, very little money is spent on studying generic drugs. Are we getting enough study before the patent clock runs out?