I am a participant in the studies at the University of Iowa Wynn Clinic, which I believe is the one mentioned in another comment. I have Leber's Congenital Amaurosis, it's roughly the same condition as RP from what I understand, one of my doctors won't even make the distinction between the two. They took a biopsy from me about six years ago and I have visited them once every two years since then. There is a lot of awesome stuff coming, but it's still very much in development. I know the Wynn Clinic just got an enormous amount of funding for a new ultra sterile lab so they can continue progress more effectively. My doctor also mentioned that they are experimenting with bio 3D printing. My doctors are very confident that something will happen within my lifetime, however they also aren't the types of people to instill false hope. At my last visit this past January they told me we are at least a decade away from making this into a procedure that they can roll out to patients. They did say they are in the process of starting human trials though which is exciting. Long story short things are happening for people with degenerative retinal conditions, but we are going to have to wait a bit. I'm hopeful and excited though.

Mid-twenties guy with RP here, (Not the one from OP's post). I go in to a specialist once every two years to see what's new for treatments and stuff. My doctor told me there was a study that showed a connection between taking extra vitamin A and slowing the progression of RP down. Bilberry and Lutine vitamins have also been indicated as helpful. As always, YMMV.

As for the stem-cell treatments, I know a lot of the stuff that's being tried out is primarily using people who have gone completely blind from RP. I still have enough vision to read, but I'm legally blind, so I'm definitely watching the subject.

u/yodatheweise's post is spot on as well. Do your best to be a good friend. I was diagnosed at age eleven, and the hardest part of it all has been the isolation of my friends being able to drive and me not getting included in stuff. Best of luck to your friend.

Off the top of my head: University of California Irvine just launched a small human trial for stem cells in the retina. RIKEN in Japan recently had some success with stem cells in the human eye. The University of Iowa is soon to have a clinical trial in humans with skin cells turned into photoreceptors. $1 There's many other research universities either beginning trials or about to. It's all still in the relatively early stages but there's significant progress being made. It'll still be five to ten years before people really start getting stem cell treatments because scientists need to be sure the treatments are safe and effective. There's also gene therapies and bionic retinas being developed. At some point a treatment may involve one or more of those options together. I firmly believe the day is coming soon when this condition will be treatable. Right now people with RP need to get genetic testing done and help raise money for research. As a friend, remember that anyone with RP is dealing with an immensely frustrating and isolating disease and it's so important to keep them included in ordinary life as much as possible.