Lots of biotech companies are working on immunosuppressant-free islet-equivalent transplantation.

Two examples off the top of my head: Sana recently announced islet cell transplantation without immunosuppression (press release: https://ir.sana.com/news-releases/news-release-details/sana-... ) and Vertex (ongoing trial: https://www.breakthrought1d.org/news-and-updates/vertex-laun... ).