Human leukocyte antigen, or HLA, genes, help the immune system tell the difference between the body’s own tissues and outside threats. In some people, certain versions of HLA genes mistakenly flag normal proteins as dangerous, which can push immune cells to attack joints, nerves, the gut, or other organs. Many autoimmune diseases are driven by changes in HLA genes. RheumaGen is developing a new kind of gene-editing treatment that aims to cure autoimmune diseases by going after one of their root genetic triggers. Instead of broadly weakening the immune system, the company’s goal is to switch off a single “bad” version of an immune gene while leaving the rest of the body’s defenses intact. We spoke to Richard Freed, CEO of RheumaGen, about the role of HLA genes in autoimmune diseases, how the company’s gene-editing therapies work, and its lead program in rheumatoid arthritis.