What happens when a drug works — but only for one person?

Really, really intriguing piece at Nature News by Heidi Ledford. It's all about a class of patients called "exceptional responders" — aka, the people who got a benefit (sometimes a big one) from a medication or treatment that otherwise failed the clinical trial process. When we do clinical trials, we're looking at group averages. We want to know whether a drug performed better than placebo when administered to lots of people. Sometimes, though, drugs that can't do that do seem to have a positive effect for a few lucky individuals. Now, scientists are trying to figure out why that is. What makes those people special? And how should this change the way we do research?