
Originally Posted by
Wise Young
Thanks very much for posting.
As you know, Geron has been trying to get this trial approved for nearly 4 years. This is the first clinical trial using cells derived from human embryonic stem cells. Last year, the US Food and Drug Administration (FDA) put a hold on the trial, causing widespread speculation that the hold was politically motivated. However, after 6 months of negotiations, the FDA has approved the protocol. The company has not yet specified if there are any changes to the protocol. In their press release, however, they indicate that the trial will be carried out on 10 patients within 2 weeks after a thoracic "complete" spinal cord injury. The goal of the trial is to assess the safety and feasibility of transplanting these cells to the spinal cord. The trial may start as early as June.
People should understand that this is a phase 1 trial, intended to assess safety and efficacy. If this trial indicates that the treatment is safe, they will go to phase 2 trials, which may examine different dose (amount) of cells that will be injected into the spinal cord, different immunosuppressive protocols (which is necessary because the cells come from a cell line that may be rejected), and possibly different times after injury. When they have a protocol that they think is likely to restore function, they will go to phase 3 trials that are usually done by multiple centers, to test the efficacy and safety of the treatment in large numbers of patients. It is important to remember that this is just to starting of a long clinical trial process that may take a number of years to complete.
It is too early to think about use of this therapy for chronic spinal cord injury. Note that Dr. Douglas Kerr at Johns Hopkins has published studies indicating that human embryonic stem cells can produce neurons that replace motoneurons in the spinal cord of rats that have been infected with a virus that kills motoneurons. This is important for people who have had injuries that have damaged motoneurons in their lower spinal cord. For example, most people who have had injuries to the T11, T12, and L1 vertebral segments will have damaged the part of the spinal cord that contain motoneurons for the legs. This may cause flaccid (as opposed to spastic) paralysis and atrophy of leg muscles. Replacement of motoneurons may restore muscle function in such patients. The current Geron trial will not be studying this possibility.
I hope that there will be more studies in the coming years, involving not only human embryonic stem cells but other types of stem cells. As you know, we are starting clinical trials in China to look at umbilical cord blood stem cells. Others are beginning to look at neural stem cells. In the coming year, there will likely be clinical trials of induced pluripotent stem cells (stem cells that are created from your own cells by inserting four genes). In my opinion, cell transplants must be combined with other therapies to provide long term growth factor support and block growth inhibitors in the spinal cord. All this work is just starting.
Wise.