I think it is simpler than that. The inflection point is likely to be the pediatric Rett study.
That does two important things. It should show safety in children which demonstrates safety in all age groups. That opens up Rett, Fragile X, Autism, etc. at the earliest diagnosis.
It will also validate the MOA in a larger controlled study in a different CNS disease. That will provide strong support for the upstream action MOA in CNS disease.