Advanced Cell Technology, Inc. (a biotechnology company based in Marlborough, Massachusetts) has announced the treatment of the first European patient in a third dosage cohort of a Phase I/II clinical trial for Stargardt’s macular dystrophy (SMD). The clinical trial, using retinal pigment epithelial (RPE) cells derived from human embryonic stem cells (hESCs), represents a key milestone in the progression of retinal stem cell medicine. The first European patient received an injection containing 150,000 hESC-derived RPE cells, compared to the 100,000-cell dose used in patients of a second cohort.