Neural Stem Cell Therapy for Ischemic Stroke Patients

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The single largest cause of adult disability in the developed world is ischemic stroke, in which blood flow in or to the brain is blocked. It precipitates immense amounts of social and financial costs. Currently, therapies for stroke focus on prevention or acute phase treatments that arrest the stroke while it is happening. But many patients are not fortunate enough to get acute phase treatment and suffer neurological damage that leads to functional and cognitive impairment. Until now, there have been almost no options for such patients. But last February, a company called ReNeuron received approval to begin a clinical trial of neural stem cell therapy for disabled stroke patients [1]. Two patients have been treated thus far and the therapy appears to be safe.

ReN001: a clonal human neural stem cell line developed by ReNeuron for clinical use in the treatment of stable disability after stroke.

The PISCES study (Pilot Investigation of Stem Cells in Stroke) is the first clinical trial of neural stem cell therapy for stroke patients in the world. In it, twelve moderately to severely disabled stroke patients, all men between 60 and 85 years of age, will receive injections of ReN001 cells into their brains six to twelve months after their stroke. They will be monitored for two years to assess the safety of the technique, to identify any side effects, and to get preliminary data on efficacy. One patient will be treated and evaluated at a time; if all goes smoothly, the next will then be treated. The company plans on treating four cohorts of three men each with increasing doses of cells. The first patient received his injection of 2 million cells this past November [2]. At his three month check up at the beginning of March he had not experienced any adverse reactions or effects [3]. The third patient is slated to receive his injection of 2 million cells in May, and if all goes according to plan the next group will get 5 million cells. The study is being conducted at the Institute of Neurological Sciences at Glasgow University.

Michael Hunt, the Chief Executive Officer of ReNeuron, said [3]:

Both ReNeuron and the clinical team in Glasgow are very encouraged by the progress of the PISCES clinical trial thus far. We are delighted that the two patients treated so far are doing as well as they are and we could not have hoped for a smoother start in terms of the clinical procedure itself and the lack of any apparent short term safety effects from the ReN001 therapy thereafter. We look forward to providing further updates on the clinical trial in due course.

In animal models, ReN001 cells were shown to reverse functional deficits caused by stroke disability even when administered weeks after the stroke [4]. Potential mechanisms for how this might occur are the observed formation of new myelin sheaths around axons that have been stripped of them, formation of new neurons, and formation of new capillaries and arterioles (small branches off of arteries that lead to capillaries). Moreover, the transplanted cells seem to be cleared from the animal, as they are undetectable six months after injection.

ReN001 cell therapy consists of a neural stem cell line that was made from an extant manufactured cell bank and scaled up using ReNeuron’s proprietary cell expansion and selection technologies. The cells are genetically engineered to have a prolonged lifespan, so researchers do not need to continually use new donor cells. Importantly, this means that any cells for subsequent clinical use will come from the same cells being used in this Phase I clinical trial, without the need to re-derive or test a new batch of cells for the market.

ReNeuron is also developing stem cell therapies for peripheral arterial disease, a common and serious side effect of diabetes and diseases of the retina that cause blindness. The company has generated its ReNcell stem cell lines for non-therapeutic academic and commercial research purposes as well. Another company, StemCells of Palo Alto, California, received approval in December to conduct a similar Phase I clinical trial of neural stem cells in chronic spinal cord injury in Switzerland [5].