It's a test to see if they should bother moving forward. You don't want to gear up a big study just to find out that the treatment gives everyone cancer (which is a concern mentioned in the article) or that it doesn't work at all. You do a pilot study to see if there is potential before you waste a lot of work and maybe hurt people.
Anyway if the effect size is big enough, you don't need a really large study to get statistical significance. I mean, what are the odds of macular degeneration reversing by chance?
We do the same in web ergonomics. Testing you Ui on 3 people is enough to see the biggest flaws of the tool and engaging in more expenses. See the excellent book "don't make me think" for a quick and efficient write up on the topuc.
unfortunately that is all we have. There is nobody on earth with your exact genetic makeup (even identical twins, though then the random mutation is small enough to ignore: consider it an exception). As a result nothing exactly will behave correctly for you. A drug that causes death in 99% of those it is tried on might be the one you need, but because it is so deadly trials will ensure it never makes it to market.
Anyway if the effect size is big enough, you don't need a really large study to get statistical significance. I mean, what are the odds of macular degeneration reversing by chance?