Duchenne muscular dystrophy (DMD) is the most common and serious form of muscular dystrophy. One out of every 3500 boys is born with the disorder, and it is invariably fatal. Until recently, there was little hope that the widespread muscle degeneration that accompanies this disease could be combated.
However, stem cell therapy now offers that hope. Like other degenerative disorders, DMD is the result of loss of cells that are needed for correct functioning of the body. In the case of DMD, a vital muscle protein is mutated, and its absence leads to progressive degeneration of essentially all the muscles in the body.
To begin to approach a therapy for this condition, we must provide a new supply of stem cells that carry the missing protein that is lacking in DMD. These cells must be delivered to the body in such a way that they will engraft in the muscles and produce new, healthy muscle tissue on an ongoing basis.
We now possess methods whereby we can generate stem cells that can become muscle cells out of adult cells from skin or fat by a process known as “reprogramming”. Reprogramming is the addition of genes to a cell that can dial the cell back to becoming a stem cell. By reprogramming adult cells, together with addition to them of a correct copy of the gene that is missing in DMD, we can potentially create stem cells that have the ability to create new, healthy muscle cells in the body of a DMD patient. This is essentially the strategy that we are developing in this proposal.
We start with mice that have a mutation in the same gene that is affected in DMD, so they have a disease similar to DMD. We reprogram some of their adult cells, add the correct gene, and grow the cells in incubators in a manner that will produce muscle stem cells. The muscle stem cells can be identified and purified by using an instrument that detects characteristic proteins that muscles make.
The corrected muscle stem cells are transplanted into mice with DMD, and the ability of the cells to generate healthy new muscle tissue is evaluated. Using the mouse results as a guide, a similar strategy will then be pursued with human cells, utilizing cells from patients with DMD. The cells will be reprogrammed, the correct gene added, and the cells grown into muscle stem cells. The ability of these cells to make healthy muscle will be tested by injection into mice with DMD that are immune-deficient, so they will accept a graft of human cells.
In order to make this process into something that could be used in the clinic, we will develop standard procedures for making and testing the cells, to ensure that they are effective and safe. In this way, this project could lead to a new stem cell therapy that could improve the clinical condition of DMD patients. If we have success with DMD, similar methods could be used to treat other degenerative disorders, and perhaps even some of the degeneration that occurs during normal aging
The proposed research could lead to a stem cell therapy for Duchenne muscular dystrophy (DMD). This outcome would deliver a variety of benefits to the state of California.
First, there would be a profound personal impact on patients and their families if the current inevitable decline of DMD patients could be halted or reversed. This would bring great happiness and satisfaction to the thousands of Californians affected directly or indirectly by DMD.
Progress toward a cure for DMD is also likely to accelerate the development of treatments for other degenerative disorders. The most obvious targets would be other forms of muscular dystrophy and neuromuscular disorders. However, the impact would likely also stimulate medical progress on a variety of conditions in which a stem cell therapy could be beneficial. These conditions may even extend to some of the normal processes of aging, which can be traced to depletion of stem cells.
An effective stem cell therapy for DMD would also bring economic benefits to the state. Currently, there is a huge burden of costs associated with the care of patients with long-term degenerative disorders like DMD, which afflict thousands of patients statewide. If the clinical condition of these patients could be improved, the cost of maintenance would be reduced, saving billions in medical costs. Many of these patients would be more able to contribute to the workforce and pay taxes.
Another benefit is the effect of novel, cutting-edge technologies developed in California on the business economy of the state. Such technologies can have a profound effect on the competitiveness of California through the formation of new manufacturing and health care delivery facilities that would employ California citizens and bring new sources of revenue to the state.
Therefore, this project has the potential to bring health and economic benefits to California that are highly desirable for the state.
The principal investigator (PI) proposes a Development Candidate Feasibility (DCF) project that focuses on developing an autologous cell therapy approach for treating the genetic disorder Duchenne’s Muscular Dystrophy (DMD). The approach involves derivation of induced pluripotent stem cells (iPSCs) from patient cells, followed by removal of the reprogramming genes and insertion of the wild type dystrophin gene. These cells will then be differentiated into skeletal muscle stem cells that upon engraftment provide long-term supply of genetically corrected muscle-forming cells. Aim 1 involves the reprogramming and genetic correction of cells from a murine muscular dystrophy model and from DMD patients. In Aim 2, the genetically corrected iPSCs are differentiated and sorted to isolate muscle precursor cells. Aim 3 tests the engraftment and function of these muscle precursors in muscles of the murine disease model. In Aim 4, the PI begins the development of clinically relevant processes for human cells in preparation for preclinical studies.
The reviewers believed that a cellular therapy for DMD would have a significant impact on patients. The proposed approach was regarded both scientifically and clinically reasonable, and the PI clearly communicated the conceptual aspects of the proposed research. Reviewers differed in their opinion regarding the rationale for using iPSC rather than other cellular approaches, but agreed that the PI presents an elegant molecular biology solution with the potential to provide a safe therapeutic cell product that does not contain unwanted genes. The approach also enables introduction of large genes, an important aspect because of the size of the dystrophin gene, although a reviewer pointed out that the use of corresponding minigenes has shown some promise in the field. Reviewers felt the proposed molecular strategy probably provides enough of a competitive advantage over similar cell-based therapeutic approaches for DMD pursued by others, and appreciated that the technology was developed in the PI’s laboratory and the PI’s institution holds the patent.
Reviewers raised concerns regarding the feasibility of the study. Although the molecular biology approach is well supported, reviewers uniformly criticized that no preliminary data is presented regarding iPSC differentiation into muscle precursor cells, and felt that time required to work out the protocol could impact the proposed time line. Reviewers also indicated the milestones are marginally specific in determining success metrics.
Reviewers believed the PI is well qualified to implement most of the proposed studies but would benefit significantly from collaboration with a cell biologist, especially because of lack of expertise with iPSC differentiation. The PI describes potential collaborations with well-regarded colleagues at the applicant institution, but reviewers were concerned that these collaborations had not yet been formally established. Similarly, a potential collaboration with an industrial partner will be critical for enabling the scaling of iPSC production and modification, but has not been defined. Reviewers did appreciate the PI’s commitment to the project, found the budget to be appropriate, and praised the research environment.
In summary, this DCF award application describes a study to derive genetically corrected iPSCs for the treatment of DMD. Despite the reviewers’ enthusiasm regarding the rationale and potential impact, they raised several concerns regarding the feasibility, the lack of preliminary data, and lack of formal collaborations.
A motion was made to move this application from Tier 2 to Tier 1, Recommended for Funding. Reviewers discussed that the proposed molecular biology approach may have wide applicability in the cell therapy field, as this technology has the potential to help move iPSC products through regulatory approval. Although other promising approaches to treat DMD are under investigation, this proposal has ramifications in general for iPSC-based cell therapy approaches. Reviewers acknowledged the feasibility risk of this application, but believed the novel technology mitigated this reservation. The motion carried.