I was thinking that if I was in the Imagine trial and I was on...

I was thinking that if I was in the Imagine trial and I was on placebo and I had taken it for 12 months and subjected myself to regular intrusive testing for the whole of that time - without any apparent benefit or improvement - why the hell would I agree to another 12 months of inconvenience and bother.

There is only one reason of course. The physicians running the trial have been so impressed with the benefits gained by those on PBT2, that they have managed to encourage the placebo trialists to give it another crack so they, too, can experience those benefits

If the benefits had been insignificant, I very much doubt that the physicians would have bothered with including the placebo sample in the Extension trial. There would have been no imperative for it.