"he would have to leak some noted changes of the study group",...

"he would have to leak some noted changes of the study group", no he will not do it. It would be the stupidest thing and after that, nobody would trust him or the results of this expensive double-blind placebo-controlled study. But to tell the results of the open study is possible as is to tell about the animal experiments done with ATH434.
He is not having a one-hour talk but he stands in front of his poster for one hour and people come to ask about his study. Often an official reviewer asks him questions and people around the poster listen. It may be that on the poster there is not a word from the open study but he could mention something about it in the discussion with those around the poster.