If I’m not mistaken, EBT-101 human trials for HIV are under way as of last month. Hope this works out the same for humans.
"Approximately 9" participants seems surprisingly low. Although to be honest, if I were infected with HIV and on HAART, I think I would find it hard to justify to myself an experimental gene therapy when HAART is already pretty darn effective.
But maybe I would... my understanding is the impact on life expectancy is still there once you get older. My guess is the constraint is more regulatory/clinical than lack of demand.
The primary question is "will anyone die or have extreme negative side effects". They run the study small in this phase because it might kill or seriously harm the entire study population.
Once they know that nothing extremely bad happened, they'll try on bigger populations.
They expect a big enough effect on the virus to be able to measure it in this tiny population.
In reality though, running medical trials is hugely expensive, the FDA requires all kinds of procedural documentation, as well as documentation of software code etc.