“Not everything that works on animals works on humans”
Frank Bradke on the regeneration of spinal cord injuries using paclitaxel
Mr Bradke, today you and your colleagues published a study in the journal Science, in which you were able to stimulate new nerve cell regrowth in the injured spinal cord of rats using the drug paclitaxel. After the treatment, the movements of the animals significantly improved. How important is this discovery?
The thing that is so special about the drug paclitaxel is that it both allows severed axons (nerve fibres) to start growing again and also limits the formation of scar tissue. These are two factors that normally affect regeneration after injuries to the central nervous system. It is the first time that a drug has been found to have this dual effect. It is literally a small breakthrough.
When will patients with brain or spinal cord injuries be able to benefit from your discovery?
We are still far from a potential clinical application. On the one hand, paclitaxel has already been used for years to treat cancer, e.g., ovarian and breast cancer. Its side effects and interaction with other drugs are therefore well-known. In addition to this, we have administrated paclitaxel in much smaller doses than those used in cancer treatment. Naturally, this should facilitate and speed up clinical development.
On the other hand, we still do not know if the drug has the same effect on human nerve cells. If we could always assume that results from animal testing are directly applicable on humans there would no longer be any incurable diseases. We have begun by investigating the basic principles and mechanisms in a cell culture and then in rats. Following these very promising results, we need to find out whether paclitaxel has a similar effect on the nerve cells and scar tissue in other species, which are more closely related to humans than rats. Also, it remains to be seen how long after an injury paclitaxel is still effective. I would say that – if it works – it will be at least another ten years before we see paclitaxel in clinical application on patients.
Are you in contact with any pharmaceutical companies that could take over the clinical development?
Not so far, but that will surely change soon. The patent for the application of paclitaxel is held by Max Planck Innovation, the knowledge transfer company of the Max Planck Society. However, this does not in any way affect further research on the drug.
What are your aims now?
In the published study, we investigated the regeneration of nerve cells immediately after an injury. The important question now is, of course, whether paclitaxel can stimulate axonal growth even long after the injury occurred. Moreover, we want to analyse the improvement in functionality. To do this, we will conduct additional behavioural experiments together with other research groups.
Thank you for the interview.
Interview by Harald Roesch