Eli Lilly (LLY) announced some bad news last week when they dropped arzoxifene, a once-promising osteoporosis treatment (and successor to Evista (raloxifene), which has been one of the company's big successes).
If this drug had been found ten or fifteen years ago, it might have made it through. But the trial data showed that while it made its primary endpoints (reducing vertebral fractures, for example), it missed several secondary ones (such as, well, non-vertebral fractures). And the side effect profile wasn't good, either. That combination meant that the drug was going to face a hard time at the FDA for starters, and even if it somehow got through, it would face a hard time competing with generic Fosamax (and Lilly's own Evista).
So down it went, and it sounds like the right decision to make. Unfortunately, given the complexities of estrogen receptor signaling, the clinic is the only place that you can find out about such things. And there are no short, inexpensive clinical trials in osteoporosis, so the company had to run one of the big, expensive ones only to find out that arzoxifene didn't quite measure up. That's why this is a territory for the deep-pocketed, or (at the very least) for those who hope to do a deal with them at the first opportunity.
One more point is worth emphasizing. Take a look at the structures of the two compounds (from those Wikipedia links in the first paragraph). Pretty darn similar, aren't they? Arzoxifene is clearly a follow-up drug in every way - modified a bit here and there, but absolutely in the same family. A "me-too" drug, in other words, an attempt to come up with something that works similarly but sands off some of the rough edges of the previous compound. But anyone who thinks that development of a flow-up compound is easy - and a lot of people outside the industry do - should consider what happened to this one.