Friday, March 7, 2008

No Easy Stem Cell Lunch

Amgen today announced that Epogen, a blockbuster drug that is often used to produce new blood cells in anemic cancer patients undergoing chemotherapy, has significant risks. The problem is that the drug increases the risk of accelerated tumor growth and death. What does this have to do with stem cells? At least one US company has used this drug to mobilize adult stem cells from the bone marrow into the blood circulation so they could collect them for storage and future use. Several foreign companies are also using similar methods. This approach has been a bit of a scientific mystery, as the stem cells being mobilized were actually what's called CD34+ stem cells and not mesenchymal stem cells. Why is this a problem? CD34+ cells make new blood cells and blood components, but in primates like humans, it's doubtful they can turn into mesenchymal stem cells capable of repairing bone, muscle, cartilage, tendons, organs, or nerve tissue. So why collect them in the first place? Good question.

This problem with Epogen again brings up a big problem with our big pharma approach. Any drug designed to systemically ramp up one system is likely to have unintended side effects. In the end, the only way to treat many problem is a local approach, such as placing stem cells in an area in need of repair via needle guidance.

So in the end, there is no free stem cell lunch...