Vyvanse is in the same family of ADHD drugs such as Anderall. Maybe you can try the Ritalin family, including
Metadate CD. By the way stimulant drugs, such as Vyvanse, Ritalin and Metadate, seem to make the PDD / Autism and Anxiety symptoms worse in some children. If the Ritalin / Metadate does not work you could try Stratera, a non-stimulant type medicine. Good luck.