Speaking of cancer trials, I mentioned the other day how they tend to be smaller than those for many other diseases. But that doesn't mean that they're always easy to run, as a search for "clinical trial design oncology" will show. Note the number of people offering to help you out, via seminars, consulting visits, books, and entire journals devoted to the topic.
The problems start early. Patient recruitment is a big problem for many of the less common types of cancer, and it's getting to be a problem for the better-known ones, too. If you look at all the therapies that are being aimed at breast cancer, for example, and run the numbers, it looks like there aren't enough breast cancer patients in the US to fill out all the trials that would be needed. Cost is, of course, a big reason why a lot of clinical trial work is being done overseas these days, but access to a new pool of patients is a factor, too.
Which brings up another complication - do you want patients who've tried other drugs? That depends on where you're targeting your therapy. If you hope for it to be a first-line drug, you probably want patients that are newly diagnosed. There's a steady supply of those, but not everyone who's newly diagnosed is going to be willing to participate in a clinical trial, not when there might be more proven treatments available. The worst case is when you're looking for drug-naÔve patients with advanced types of cancer. That's feasible (in theory) for some of the ones that creep up on you (like colorectal cancer), but next to impossible for some others.
But if your drug is going to be a second-line therapy, then you should go ahead and see how it performs in patients who've already been through the first-line stuff. There is, unfortunately, a steady supply of those people, too, and they're often more willing to take a chance.
Your clinical trial design will also be influenced by the kind of cancer you're hoping to treat. If you're looking at a very specific type or two, as is the case with Novartis's Gleevec, you may have to cast the net pretty widely to round up enough people. (We'll ignore the fact, for now, that Gleevec sells a billion dollars a year, which means that a lot of people are getting it when it has very little chance of doing anything for them.) If you have a new mechanism that hits all kinds of cancer cells, then you may want to dip into all sorts of different patient populations to see if one of them looks like a good place to take your stand in later Phase II and III trials. The danger in doing that is that your patients may be such a mixed bag that you can't get good statistics on anything.
Ah, statistics. You'll have noticed that I'm referring to cancer patients as if they were so many terms in an equation, which from the standpoint of drug development is exactly what they are. That comes across, to those outside the medical and scientific areas, as a pretty cold way to talk. Guilty as charged - but keep this in mind: people who work for drug companies get cancer, too, as do our friends and relatives. And we're just as upset as anyone else when that happens. But without the icy numbers, and lots of them, we're not going to be able to do anything to help.