As came up in the comments to the previous post, there's not as much price competition inside a given drug category as you'd think. That's not because we're Evil Price Gougers, at least not necessarily. As I was pointed out yesterday, "me-too" type drugs aren't as equivalent as some people think. The main reason we go ahead with a drug in a category where there's already competition is because we think we have some advantage that we can use to gain market share.
This is a constant worry in every drug development effort where there's already a compound out there. I've personally, many times, been in drug project meetings where we've looked at the best competing compound (one that's either already marketed or well into clinical trials) and said "We haven't beaten them yet. We're not going to make it without some kind of unique selling point." The best of those, naturally, would be superior efficacy or a superior safety profile. Then you have easier dosing, fewer interactions with other drugs, and so on. I need to emphasize this: I have seen drug projects killed because no case for an advantage could be made.
Now, there's room to argue about how much better efficacy a drug needs to be a real advance in the field, or at least a bigger seller. You can argue about any of those possible advantages I listed, and it's true that drug companies push some compounds that aren't exactly huge leaps over the previous state of the art. (You see more of that when there's a case of shriveled pipeline in progress.) But there has to be something, and the bigger the difference, the better it is for us. We're motivated, by market forces, to come up with the biggest advances we can. The sales force would much, much rather be out there with data to show that the new drug beats the competition in a clean fight, as opposed to saying that it beats the old one on points, in a subset of patients, if you massage the data enough and squint hard, and besides it tastes better, too. . .
And as I've pointed out before, we often find out things about compounds long after they've reached the market. Lipitor, as discussed yesterday, is a case in point. I have not been a Lipitor fan in the past. The statin field seemed already pretty well served to me (as it did to a number of people inside Warner-Lambert during the drug's development, frankly.) The drug made its way forward based on efficacy in the clinic: it seemed to do a better job lowering cholesterol and improving the LDL/HDL ratio. How much advantage that is in the long term is another question, but those are the best markers we have.
The whole antiinflammatory c-reactive-protein story about the drug only came up after it was already on the market. The marked differences between it and the other statins, which I have to assume at this point are real, are a pleasant surprise to everyone involved. Warner-Lambert (and then Pfizer) thought it was a better compound, but not to this degree or for these reasons, I'l bet. I'd say that this is another argument for having multiple drugs in the same category. We don't, and can't, know everything that they'll do.