An interesting study was published this week in the Journal of Neuroimmunology spurring a press release from Geron that stated “GERON’S HUMAN EMBRYONIC STEM (ES) CELL-BASED THERAPEUTIC FOR SPINAL CORD INJURY EVADES DIRECT ATTACK BY THE HUMAN IMMUNE SYSTEM”. The title is a little misleading since the cells really only evade immune cells in an in vitro model. However, the work was published in a peer-reviewed journal so it has some scientific credibility.

This study’s major limitation is that it is performed in vitro, however to get at these questions in an in vivo model would be an extremely difficult (if not impossible) task to perform. Whenever you want to study immune response to human cells, it doesn’t really make sense to do it in animals due to cross-species interactions. It is possible to try to recreate a species specific cell population similar to yours (e.g. make mouse ES cells, test in other mice), but you then are not testing the exact cells you want to take into clinical trials and the data has less value in regulatory filings. I do applaud Geron for getting such a study performed and published in a peer reviewed journal, as the data is strategic for their business model as they progress through clinical trials.

The data presented in the paper is important to Geron for several reasons:

1) It suggests that patients that get Geron’s ES cellular therapies (or at least GRNPOC1, the spinal cord injury product) would not require chronic immune suppression drugs like people that receive organ transplants.

2) The data from this study potentially lowers regulatory hurdles, as it can be submitted to the FDA to give more confidence in the safety profile of the allogeneic cell therapy. However, immune responses would need to be closely monitored during human studies.

3) It suggests that Advanced Cell Technology’s more “autologous” strategy for personalized embryonic-like cellular product (via nuclear transfer) would have fewer competitive advantages over Geron’s allogeneic ES cellular product.

This study is setting the stage for Geron’s first in human ES cell clinical study. They have been gearing up for a spinal cord injury trial for 2007, but it looks like they are now targeting 2008 (regulatory filings can take forever). Advanced Cell Technologies are close behind Geron, targeting 2008 for their first IND using personalized ES cell therapy.