The first-ever clinical trial to test a therapy based on human embryonic stem cells has started. Menlo Park, California-based Geron Corp announced today that a patient who was recently partially paralyzed by a spinal cord injury had millions of cells derived from embryonic stem cells injected into the site of the damage.

The subject was treated with stem cell-derived neural precursors called oligodendrocyte progenitor cells at the Shepherd Center in Atlanta, one of seven potential sites in the US where participants can enroll in the landmark phase 1 trial. At the moment, however, only the Shepherd Center and Northwestern Medicine in Chicago are open for patient enrollment.