The FDA has approved Tregzi, the first regulatory T cell-based immunotherapy designed to prevent a dangerous complication called chronic graft-versus-host disease (GVHD) in blood cancer patients undergoing stem cell transplants. In a 187-person clinical trial, patients receiving Tregzi had a 78% one-year GVHD-free survival rate compared to just 38.4% for standard transplant recipients. Serious chronic GVHD occurred in only 12.6% of Tregzi patients versus 44% in the control group. The therapy uses donor-derived immune cells — including regulatory T cells, which calm overactive immune responses — alongside stem cells to rebuild the patient's immune system while reducing the risk of donor cells attacking the patient's own body.