Geron Corp. has revealed why the Food and Drug Administration halted its much-heralded Phase I clinical trial using embryonic stem cells to treat spinal cord injury 2 weeks ago. The reason: "non-proliferative cysts." In a statement issued yesterday, the company explained that in their ongoing animal studies, a small number of those injected with the stem cell preparation had developed tiny cysts at the injury site.
But not to worry, says Geron. That's actually good news. Spinal cord patients routinely develop much larger cysts. More significantly, there is no sign that the stem cell treatment causes tumors in the animals. And animal tests with a new batch of GRNOPC1, the stem cell preparation, showed no cysts. Geron officials expressed confidence that the trial will soon be back on track.