Scientific American checks in with the latest developments on embryonic stem cell (ESC) research. Clinical trials are once again under way for ESC therapies, but expectations should be tempered.
The author doesn’t want to use the word “disappointed” but he does stress supporters are in for a reality check.
To address the most obvious one first: practicable ESC-based therapies are years away. The upcoming tests of Geron’s paralysis treatment, for example, will look only at how safely it is tolerated by patients; tests of its effectiveness are further off. The therapeutic cells helped mice to partially recover from spinal injuries, but in humans they might fail to do the same or, worse, might induce tumors. It will take time to find out. New drugs often take five to nine years to progress from phase I testing to market.
Moreover, many if not most of those future therapies based on ESC research may not actually involve ESCs. Patients, after all, will not be able to supply embryonic cells directly from their own body. Therapeutic ESCs would either have to come from immunologically matched stockpiles (the equivalent of blood banks) or be cloned for each patient individually. Both solutions would involve technological and legal headaches. Using adult stem cells or others reprogrammed for versatility from a patient’s own tissues may therefore prove much easier. (Adult stem cells are indeed already used to treat some blood-related and orthopedic disorders.)