Interventions that delay aging are expected to improve health. In the current US National Institute on Aging's Interventions Testing Program (ITP) the immunosuppressive drug rapamycin was found to increase the maximum life span in mice. These mice started receiving this treatment at an age corresponding to 60 years in humans. Rapamycin targets the same mechanism which was critically involved in the life span extension previously seen in certain mutants of worms flies and mice. The maximum life span was increased in some of these mutants by more than 250 percent, suggesting 1) that the maximum...