Organ and cell transplants are potentially life-saving treatments for a variety of medical conditions, but their success depends on how long the transplanted cells or tissues can survive in their new host. Drugs that suppress the immune system to minimize rejection must strike a delicate balance between being powerful enough to hold back the recipient’s immune system from destroying the donated material, without being too potent to cause toxic reactions. In a study presented at the Summit on Stem Cell Derived Islets in Boston, researchers report on encouraging results using an experimental immunosuppressive drug in people with Type 1 diabetes.