Wired reports this interview with Tom Okarma, CEO of Geron which is starting a major trial using cells derived from embryonic stem cells to help reverse damage from spinal cord injury.

It sounds interesting, and Okarma sounds cautious and very consciuos of the importance of getting this first major trial right. For every trial that fails because it was rushed, the field will be more and more difficult to fund and fight for.

We recognize that the world's spotlights are going to be on this. So we want to structure out as much subjective stuff as we possibly can. That's the first point. The second point, again to your point of safety, is that the initial patients in the trial a) will get a very low dose of cells, which is always done with a new therapy. They just start with less than the therapeutic range because you want to be sure there's no toxicity associated with this.

How are we going to monitor for toxicity in a patient that has a complete thoracic injury, that has no sensation below the point of injury? Well, if we start with a T3 lesion (an injury at the third vertebra in the thoracic region of the spinal cord), the question will be: Do we see evidence of an ascending paralysis? In other words, changing patients' physiology from a T3 lesion to a T2 or a T1, ascending toxicity.

We start with complete patients because they have no hope of recovery and we want to offer them something. We're starting with thoracic lesions because there's no significant impact for the patient should we see toxicity go from, say, a T3 to a T2 lesion. If we had started with cervical complete lesions and went from C4 to C2, that would be significant because we would reduce respiratory drive.

We're turning every single stone over that we can to reduce -- if not eliminate -- the risk to these patients who volunteer to get the cells for the first time. Once we go through the initial safety cohorts ... then we start looking at incomplete lesions. For all these patients, the efficacy is based on three simple principles: Do we restore sensation in any way or conversely reduce neuritic plan? Do we change bowel or bladder control? Do we see patients enjoying some degree of local motor recovery?