DR. FREDERICK MUNSCHAUER: A clinical trial is a very well-designed experiment where you take a drug that has been shown to be safe in the doses normally used in humans, and you compare it to either another therapy or a placebo -- a sugar pill or a therapy that would have no effective value -- and you select patients that are relatively similar, and then randomly assign one patient to the drug and another patient to the placebo, and then follow them out over a period of months or years to see whether one particular aspect of their disease changes. That may be attack rate in multiple sclerosis, or it may be progression in disability, and at the end of that time you see whether this very similar group of patients over years does better with the drug versus the placebo in a statistically significant way. That's a clinical trial. It represents a major achievement of medicine, and it's the only way to really evaluate both safety and efficacy of a drug in MS.
DAVID R. MARKS, MD: By statistically significant, you mean the rate at which they got better was better than just chance, right?
DR. FREDERICK MUNSCHAUER: Yes, correct.
DAVID R. MARKS, MD: There are different phases of clinical trials. Tell me what the different phases are.
DR. JEFFREY GREENSTEIN: There are actually four phases of clinical trials. The first phase is a trial of the agent in people who are healthy to see whether or not there are untoward side effects. Once that's completed, then we move on to a phase II study where we begin to start using the drug in somebody with a disease that we hope to treat. We're primarily still interested in whether or not there is safety in use of the drug, but we're also hoping to glean some information as to whether or not there may be efficacy as well. However, we can't prove efficacy in that kind of study because it's usually too small a study to give us what we call "statistical power."