Phase I clinical trials generally raise greater ethical and human protection challenges than later stage clinical trials, suggesting a need to proceed cautiously. This is particularly the case for Phase I trials with a novel therapy being tested in humans for the first time, usually termed first-in-human (FIH) trials. In January 2009, the Food and Drug Administration approved the Investigational New Drug application of Geron Corporation, a small California-based biopharmaceutical company, to initiate a clinical trial to assess GRNOPC1, a human embryonic stem cell–derived candidate therapy for severe spinal cord injuries. This article evaluates the ethical and human subject protection issues raised by the Geron FIH trial. It identifies problems with the approval process and with the conduct of the trial, and then recommends ways to improve review of future proposed trials with novel and high-risk therapies.