This has happened before, going all the way back to the death of Jesse Gelsinger in 1999, when gene therapy was in its infancy. But there are other issues to consider in gene therapy. Both have been successful targets in gene therapy, with the latter providing long-term treatments for Hemophilia A and B (discussed previously here and here). This particular gene variant makes the receptors more responsive to growth hormones, sending cells a stronger, more urgent signal to proliferate. Finally, which one of these scientists who worked on this project has the “Neanderthal” variant?