More than four years ago, the American Victoria Gray received a phone call that changed his life. It was his hematologist, offering him entry into a clinical trial with an experimental drug. Gray, 37, has sickle cell anemia, the most common genetic disease in the world. Every year about 300,000 babies are born with this condition caused by a mutation that causes the red blood cells to be not round, but rather crescent-shaped. These sharp blood cells get stuck in the vessels and cause paralyzing pain throughout the body, chronic damage to many organs, and a high risk of dying from a stroke. Gray was given seven years to live at birth.