Early Translational I
Parkinson’s disease is a debilitating, neurological disorder that affects over one million Americans. An additional 50,000 Americans get the disease every year. It tends to affect patients over 55 years. However, younger patients of 30-40 years old can also get the disease. Patients lose the ability to control their movement. Their muscles become rigid, the arms shake, and the patient tends to walk in a shuffling manner. Everyday skills like eating, tying shoe laces and buttoning shirts become difficult to perform, and the quality of life deteriorates. Scientists believe that the main cause of the disease is death of nerve cells in the brain that make the neurotransmitter dopamine. When dopaminergic (DAergic) neurons die, the level of brain dopamine is reduced. Doctors treat the disease by replacing the lost brain dopamine using two drugs: 1) L-DOPA, that is made into dopamine in the brain, and 2) Dopamine-like drugs, e.g. pramipexole, that mimic the action of dopamine. However, these drugs treat the symptoms of the disease, not the cause. DAergic neurons continue to die, even though the patient might feel better. Eventually, after 5-7 years of treatment, the drugs don’t work as well. Scientists believe that an alternative method of treating the disease is to replace the dead DAergic neurons with live DAergic neurons made in the laboratory, and transplanted into the brain by a procedure called cell therapy. There is hope in the scientific community that DAergic neurons needed to treat Parkinson’s disease can be made from stem cells, and this research is supported by the California Institute of Regenerative Medicine. However, making DAergic neurons from stem cells on a large scale will likely to take many years. An alternative approach is to use a type of cell called a DAergic progenitor neuron. Unlike stem cells that can make all of the different types of cells in the body, committed progenitors make only the one type of cell they are committed to make, in this case, DAergic neurons, and in limited quantities, compared with stem cells. There are one million DAergic neurons in the region of the brain associated with Parkinson’s disease. These neurons can be removed from the human fetal brain, and grown in the laboratory to produce five million, that can be used to treat five patients. Growing the cells is just one of many steps needed for success. The DAergic neurons must be detached from the growing surface, dispersed, separated from dead cells, packaged into small clusters of 5-50 cells, and maintained in a viable state at room temperature for up to 24 hours. They must also be treated with a neuroprotective agent to minimize cell death after transplantation into the brain. Lastly, the cells will be tested in an animal model of Parkinson’s disease, and then in a clinical trial. One advantage of this approach is that it will save valuable time, by preparing the way for the use of DAergic neurons produced from stem cells.
Statement of Benefit to California:
The estimated cost to the United States per year for drugs to treat Parkinson’s disease (PD) is $1.5 B. California has 10% of the population of the United States, so the pro-rated cost to California is $150,000,000. The estimated cost to the economy of the United States per year due to lost productivity and the cost of care related to PD is $5.6 B. On a pro-rated scale, the cost to California is $560,000,000. Anyone who has witnessed human beings with PD in group therapy will know that the human cost of this debilitating disease is difficult to describe. It is seen in the eyes of a proud middle aged woman who reaches for a hand shake, but is defeated and humiliated by the imposed slowness of her movement. There is the businessman who uses his left hand to physically constrain the violent shakes of his right hand during meetings. Since 1961, scientists have understood that the major cause of PD is the degeneration of Dopaminergic (DAergic) neurons in the substantia nigra (SNc) in the ventral midbrain. Symptoms appear when 70-80% of our DAergic neurons have degenerated. Drug therapy is very successful in relieving symptoms, and improving the quality of life for patients. However, drugs do not modify the underlying neuropathology of the disease. The disease continues to progress, even as the patient’s symptoms are relieved. As the disease progresses, drugs become less effective, and the disease becomes difficult to treat in this chronic stage. The first study to suggest that cell therapy might be an effective treatment for PD was published by Mark Perlow at the National Institutes of Health in 1979. Since then, over 200 patients have been transplanted with DAergic neurons derived from human fetal brain tissue. This effort culminated with a clinical trial that was published by Olanow et al in 2003. The results were negative. We have also learnt that the transplanted DAergic neurons can also degenerate exactly like the patient’s original DAergic neurons. Two conclusions follow from these results: 1) Transplantation of human, fetal nigral tissue into the brains of PD patients is not an effective treatment for PD. 2) When DAergic neurons are introduced into the brains of patients, they must be protected, or they will also degenerate. DAergic neurons for use in cell therapy to treat PD must be prepared in the laboratory as a nearly pure population of DAergic neurons from stem cells ultimately, and progenitors in the short term. We must also discover new drugs to protect the DA neurons after transplantation. This grant application addresses both of these issues. We have developed a patented method for preparing DAergic neurons in the laboratory, and then optimizing them for transplantation. We are also actively working on new drugs to protect DAergic neurons after transplantation. Our first drug candidate called [REDACTED] is being moved forward for testing in the clinic. Cell therapy has the potential to slow down the progression of PD
This proposal is focused on the development and optimization of a cell therapy for Parkinson’s disease (PD). The applicant believes that a major bottleneck to bringing this treatment to clinic is the availability of sufficient numbers of donor neurons. Thus the applicant proposes to develop methods for the expansion of dopaminergic (DA) neuron precursor cells prior to differentiation and transplantation. In the first specific aim, the applicant proposes to optimize the production and survival of DA neuron aggregates from embryonic day 11 (E11) rat neural tissue and test these cells in a rat model of PD. In Aim 2 the applicant plans to use the knowledge gained in Aim 1 to transition to human neural tissue from 6-7 week embryos and test these cells in the same rat PD model. In Aim 3, the applicant proposes to optimize the preparation of DA neuron aggregates by applying various growth factors and then vary the dosage of cells given to the rat PD model. In this aim the applicant also plans to lay the groundwork for a clinical trial based on their cell therapy. In terms of impact, reviewers agreed that this proposal addresses an unmet medical need and that the goal of increasing the yield of DA neurons from donor tissue is an important one. However, reviewers questioned the need to start with rat embryonic neural progenitor cells rather than human, given the current state of the art. Another reviewer was uncomfortable with the applicant’s interpretation of the literature to justify the proposal. This reviewer noted that although the study of fetal DA neuron transplants published by Olanow et al concluded there was no improvement overall in treatment groups, there was some substantial improvement in individual patients. This reviewer also cited a study by Freed, Fahn and colleagues, not cited by the applicant, which showed improvement in experimental groups if analyzed as a function of age (young patients did better than older patients), as well as a few individual patients with marked symptomatic improvement. Furthermore the applicant cites a recent study by Kordower and colleagues showing that transplanted DA neurons accumulate intracellular pathology characteristic of PD, and concludes that improved protection of transplanted cells is required. However the patient in this study lived for 13 years following transplant, 8-9 of these years with significant improvement of symptoms, which seems somewhat in conflict with the conclusions drawn by the applicant. In general this reviewer felt that the applicant presented an unbalanced view of the PD cell therapy literature as rationale for the proposed studies. Reviewers appreciated the clearly defined milestones and timeline but raised a number of concerns about the design of the research plan and its feasibility. While they felt that the preliminary data for enhanced yields of rat DA neurons were substantial, they wondered whether some of the optimizations (e.g. calcium concentrations and conditions for enhancing DA neuron aggregate viability) achieved in these cells would be directly applicable to human cells. One reviewer felt that the time and resources devoted to Aim 1 would be better spent testing human cells in a large animal model following demonstration of efficacy in the rat PD model. Another reviewer noted that while the 6-OHDA rat model chosen for testing is a good one, the motor skill tests proposed are not sophisticated enough. There are now better motor tests that would provide more insight into the integration of new DA neurons into the basal ganglion circuits. This reviewer also pointed out that one of the major concerns with DA cell therapy is the potential for undesired dyskinesias and the applicant makes no mention of testing for this outcome in preclinical studies. On a related note, this reviewer also felt that more than two doses of DA cells need to be tested to determine the optimal dosage. One other concern was the lack of mention of the potential for tumor formation. The reviewers were concerned about a lack of detail in the research design. For example, the applicant stresses the importance of astrocyte conditioned media and the availability of 10 astrocyte cell lines, but provides no details about these lines (names, species of origin, passage number, etc.). In a different instance, the applicant proposes to test the effects of varying trophic factors on their cell preparation viability but does not explain why will they use the particular incubation period chosen, or how the results of these experiments will inform their transplantation strategy. Moreover, the applicant emphasizes the potential of mesencephalic astrocyte-derived neurotrophic factor (MANF) to promote viability but few details about this factor are provided. The applicant notes the possibility of “genetic transformation of the cell aggregates” to optimize cell expansion and survival but again provides insufficient detail. It was also unclear how neoinnervation of the denervated striatum would be assayed. Reviewers commented that the plans in Aim 3 with respect to a clinical trial are very vague and left them with many questions. Reviewers noted that the applicant is a senior scientist with considerable experience in the field including ownership of a patent for cell therapy technology. However, they raised significant questions about the applicant’s collaborations, resources and research environment. Reviewers appreciated that the applicant has enlisted expert collaborators in several areas, including animal models of PD and the isolation and handling of human fetal neural tissue. However, they found the absence of letters of support from these collaborators to be major issue of concern. The need for an international collaborator to supply fetal tissue was also questioned. Reviewers wondered why the applicant could not find a source closer to California and how the viability of tissue shipped over such a distance would be ensured. One reviewer questioned why the international collaborator was provided with a salary percentage in the budget given that his/her role seems limited to supplying tissue. Reviewers found it hard to judge from the proposal whether the applicant would have the space, personnel or resources to support the work described. Overall, the reviewers raised significant questions about this proposal’s feasibility. They specifically cited insufficient detail concerning the research design, environment and collaborations.