Researchers from the City of Hope Beckman Research Institute in Duarte, California have been given permision by the FDA to carry out a small-scale clinical trial to inject reprogrammed neural stem cells into the brains of terminally ill patients suffering from recurrent glioma.
Only 20 patients will be treated, and the trial is to assess the potential safety of the procedure before authorisation for larger scale trials of efficacy of the treastment can begin.
The patients to be treated will only have 3 to 6 months to live, and will have to have had tumour resection surgery to remove the majority of the cancer. The cells will be injected locally a the site of re-section and is aimed at targetting the remaining cancer cells individually.
The neural stem cells have been genetically modified to secrete the enzyme cytosine deaminase whose target will be 5-fluorocytosine, which will be administered systemically on a daily basis. Deamination of the cytosine will produce the well known, but toxic, anti-cancer drug 5-fluorouracil.
The team believe that local conversion at the site of disease will result in maximising the concentration of the active drug whilst leading to much smaller systemic side effects. Previous trials in mice lead to significant reduction in brain tumours in the diseased animals compared to those which had been untreated.
Many have criticised trials of stem cell therapies to repair brain degeneration due to the inherent risk of cancer from the uncontrolled proliferation of the injected cells. However, the neural stem cells used in this trial have not been observed dividing following 48 hours after their delivery into the brain.
If the trial is successful, and there is evidence that the recurrence of glioma has been halted, or severely postponed, it will bring credence to the hypothesis that stem cells and cancer cells migrate using the same, or similar biological cues. Furthermore, it is likely that new treatments for non-neural carcinomas will be designed based on the same principle.