Determination of optimal medication to support efficacy of hESC-derived transplants for Parkinson's disease and assessment of side effect risk.

Parkinson's disease (PD) affects over 120 000 patients in the UK and over 6.3 million people around the globe. A patient with PD could be on 3 or 4 different drugs to help with their symptoms, and additionally many of them suffer with depression so are taking antidepressants, while no cure exists. The disease is caused by the loss of cells in the brain that contain the chemical dopamine and it has been proven possible to take these cells from the brains of embryos (once they have started to make dopamine) and implant them into the brains of people with PD. Some patients who have received these transplants so far have had big improvements in their symptoms and a reduction in their medication after several months or years. However, using embryos is ethically and methodologically unsustainable, so alternative ways of making these cells is needed. We now have the technology to engineer human embryonic stem cells into the right kind of brain cells for transplantation. With this technology we can make enough cells to transplant many patients in a safe and reliable way and there are plans for a new clinical trial in 2019. However, there are some outstanding problems before we can take stem cells into patients. Previous clinical trials showed that the effects of transplanted foetal cells were inconsistent. While some patients had huge improvement to their symptoms others had none, and in addition, patients experienced motor side effects known as graft-induced dyskinesia (GID). These movements are similar to the side effects produced by the drugs, but are permanent. The cause of these side effects and variable outcomes may be the drugs patients were taking to treat their Parkinson's disease at the time of transplantation. For stem cell transplantation to become a successful treatment option for PD, it is vital that both these issues of efficacy and side effects are explored with the new cells that are ready for clinical trial. We asked over 500 people with Parkinson's disease and their carers what their biggest concerns were for cell therapy, and the majority of patients (over 90%) were worried about the possibility of long term side effects. Importantly, they were also willing to make whatever changes they might need to their medication to ensure the best possible outcome should they have a transplant.

This study will carry out 2 experiments in rats to look at the effect of medication on transplants. We can recreate Parkinson's disease on one side of a rats brain such that they are outwardly healthy animals, but we can then explore how good these cells are at repairing the damage in the brain when we give the parkinson's drugs. Experiment 1 will be a shorter experiment to look at how each drug type that is taken by a person with Parkinson's disease might affect the graft. We will look at examples of each type of drug taken by a person with Parkinson's disease and also include drugs such antidepressants that patients are also often taking. A second, longer experiment will allow us to evaluate the risk of side effects from each set of cells that will be used in the clinical trial. These experiments are based on the medications patients that are taking part in a current foetal cell trial and will use some of the exact cells that will be used in clinical trials.

These experiments are important to allow us to guide the clinical trial to select the right patients for inclusion into the clinical trial and determine what the risks might be for side effects. We may be able to identify drugs that will give the best chance of graft success, or that should not be taken in someone receiving a transplant. This information is being generated to support this clinical trial but the results will be relevant to all the planned trials worldwide for cell transplantation in Parkinson's disease so will be made available to them also.

Stem cell based approaches are poised to take over from foetal cell therapy as experimental approaches to the treatment of Parkinson's disease. Robust differentiation protocols have been identified and 2 hESC cell lines (H9 and RC17) are being produced to GMP grade materials for clinical trial. However, preclinical experiments have not, as yet, addressed the risk of reproducing the graft-induced dyskinesia identified in foetal cell transplantation trials, or evaluated the possible influence of ongoing medication on the survival and function of transplanted cells.
Two approaches will be used to determine the safety profile and effect of medication on grafts of these hESC-derived dopaminergic cells. The design of this study is based on a review of patients in the TransEUro foetal cell transplantation, who are on average taking a combination of 3 antiparkinsons medications, as well as antidepressant and sleeping medication, prior to and following transplantation. 6-OHDA lesioned rats will receive transplants in two parallel experiments. The first experiment will examine the likelihood of commonly used anti-parkinson's and other neuroactive medication (L-DOPA, dopamine D2 agonist, MAO-B inhibitor, SSRI antidepressant and GABAA allosteric modulator anxiolytic sedative) having significant acute effects on the early phase (20 weeks post-transplantation) of graft survival and function in immunosuppressed 6-OHDA lesioned rats. Experiment 2 will explore the longer term consequences of L-DOPA exposure on functional efficacy and side effect risk using neonatally tolerised 6-OHDA lesioned rats (to avoid the use of immunosuppression) treated with saline or L-DOPA prior to and following transplantation and will be monitored for 1 year.
Outcomes will directly influence the design of clinical trials with these cells, but will also be presented to GForcePD which has representatives from all groups working on clinical stem cell therapy for Parkinson's disease globally.

There is currently no cure or disease modifying strategy that significantly alleviates the symptoms of Parkinson's disease, which affects over 6 million people worldwide. The current work is based the clinical grade cell lines currently being developed to GMP by Roger Barker and Malin Parmar under a Wellcome Trust grant. This will be used in the development of first in man clinical trials in the UK and Sweden in the next 3 years. Introducing successful cell transplantation as a viable therapeutic option in the treatment of Parkinson's disease would establish the UK as world leaders in the field and offer enormous hope to the 120 000 sufferers in the UK and their families.

Additional beneficiaries to the research have been identified as the following:

Similar stem cell based clinical trials for the treatment of Parkinson's disease are being planned in the US trials also using hESCs and also in Japan using iPS cell based approaches. This data will have a direct relevance to the way in which patients are either selected for transplantation or the treatments they are given following transplantation. Understanding how medication may interact with cell transplants may be fundamental to their successful deployment.

The research team involved the research: not only will the science be highly relevant to the clinic and publishable in its own right, but the RA employed will gain a range of skills which are incredibly valuable to both academic research and industry. In vivo expertise in particular is increasingly hard to develop and the RA will receive expert training in well established, well reputed laboratories in the UK and the chance to promote this research and establish themselves at national conferences.

The research will also benefit members of associated research teams within the Brain Repair Group (Cardiff University) and Neurobiology groups at Lund University in Sweden and Cambridge University. Data in progress will be presented at GForce-PD, informal seminars and lab meetings to support the complimentary research ongoing by other groups.

Other members of the European and International neuronal cell transplantation community will benefit by furthering our understanding of the neurobiology of stem cell transplantation. This will be realised in a relatively short time frame and will be acted on as soon as it is available, with early data from Experiment 1 available within 12 months of the start of the grant.

This research will contribute to the ability of the UK to compete globally as world leaders producing successful, side effect free, hESC based transplantation. It will support our contribution to the field as groups work within the EU to accelerate hESC transplantation for Parkinson's disease into the clinic. Although not currently the major players in the field, there is an industry surrounding the development of stem cells and their use as therapeutics. The benefits will be indirect as it raises the profile of stem cell transplantation and brings the likelihood of successful transplantation closer to a reality.

The general population and local groups of people with Parkinson's disease, their carers, the general public and school children will benefit from the research through PPI and public engagement activities that EL is actively undertaking to raise the profile of stem cell research in the UK. Stem cell use is part of the biology A level curricula and the growing expertise in the local area and extensive plans for dissemination in the community will aid their involvement and understanding of ES cell research (see Pathway to Impact).