If you looked at the timelines of a clinical trial, you'll notice that there's often a surprisingly long gap between when the trial actually ends and when the results of it are ready to announce. If you've ever been involved in working up all that data, you'll know why, but it's usually not obvious to people outside of medical research why it should take so long. (I know how they'd handle the scene in a movie, were any film to ever take on such a subject - it would look like the Oscars, with someone saying "And the winner is. . ." within the first few seconds after the last patient was worked up).
The Danish company NeuroSearch unfortunately provided everyone with a lesson in why you want to go over your trial data carefully. In February of 2010, they announced positive results in a Phase III trial of a drug (pridopidine, Huntexil) for Huntington's (a rare event, that), but two months later they had to take it back. This move cratered their stock price, and investor confidence in general, as you'd imagine. Further analysis, which I would guess involved someone sitting in front of a computer screen, tapping keys and slowly turning pale and sweaty, showed that the drug actually hadn't reached statistical significance after all.
It came down to the varying genetic background in the patients being studied, specifically, the number of CAG repeats. That's the mutation behind Huntington's - once you get up to too many of those trinucleotide repeats in the middle of the gene sequence, the resulting protein starts to behave abnormally. Fewer than 36 CAGs, and you should be fine, but a good part of the severity of the disease has to do with how many repeats past that a person might have. NeuroSearch's trial design was not predicated on such genetic differences, at least not for modeling the primary endpoints. If you took those into account, they reached statistical significance, but if you didn't, you missed.
That's unfortunate, but could (in theory) be worse - after all, their efficacy did seem to track with a clinically relevant measure of disease severity. But you'll have noticed that I'm wording all these sentences in the past tense. The company has announced that they're closing. It's all been downhill since that first grim announcement. In early 2011, the FDA rejected their New Drug Application, saying that the company needed to provide more data. By September of that year, they were laying off most of their employees to try to get the resources together for another Phase III trial. In 2012, the company began shopping Huntexil around, as it became clear that they were not going to be able to develop it themselves, and last September, Teva purchased the program.
This is a rough one, because for a few weeks there in 2010, NeuroSearch looked like they had made it. If you want to see the fulcrum, the place about which whole companies pivot, go to clinical trial design. It's hard to overstate just how important it is.