This is actually the 2nd brain gene therapy research I've seen.
In the Phase I trial below, injecting telomerase and klotho AV vectors into CNS/brain was safe and it improved cognitive scores of 5 dementia patients after 1 yr follow up.
This space will hopefully get very big. Mice lifespans were extended 25-40% (massive!) through similar techniques. See Dr George Church Gene Therapy for more.