A phase 1 clinical trial conducted by UC Davis Health researchers indicates that CD34+ stem cell therapy is a safe and potentially effective treatment for retinitis pigmentosa (RP). The study, published in Ophthalmology Science, assessed the safety and preliminary efficacy of injecting CD34+ stem cells, derived from the patient's own bone marrow, into the eyes of RP patients.
The trial involved seven participants with RP who had significant loss of peripheral vision. Researchers successfully isolated CD34+ cells from each participant's bone marrow using a sterile, good manufacturing practices laboratory at the UC Davis Institute for Regenerative Cures. Each participant received a single injection of these stem cells into one of their affected eyes.
Safety and Cell Viability
The stem cell isolation process yielded high-quality cells, with approximately 90% viability. The therapy was well-tolerated, with only one patient experiencing a minor complication that resolved within 24 hours. No other serious adverse effects or infections were reported following the cell injection.
Visual Improvements
While the primary focus of this phase 1 study was safety, a notable finding was that most participants reported perceived improvements in their vision. Objective eye tests corroborated these subjective reports, revealing measurable improvements in vision for four of the seven patients.
Mutation-Agnostic Approach
Retinitis pigmentosa is a genetically diverse disease caused by numerous mutations. Existing gene therapies target only a small percentage of RP patients with specific mutations. The UC Davis team adopted a mutation-agnostic approach, investigating whether stem cells could regenerate retinal tissue and improve vision regardless of the underlying genetic cause.
Susanna Park, professor in the Department of Ophthalmology and Vision Science and first author of the study, explained, "We believe the CD34+ cells find the degenerating retina, grab onto it and could generate molecular changes to reduce the degeneration. We showed some preservation of retinal function using these stem cells in one of our animal models of RP."
Future Directions
The researchers are planning larger studies to further evaluate the safety and efficacy of this stem cell therapy. Jan Nolta, director of the Stem Cell Program and the UC Davis Gene Therapy Center, noted, "After a decade of collaborative studies testing the human CD34+ cells in mouse models of retinal degeneration, it is very promising to see their safety and potential efficacy in patients who have enrolled in the clinical trial."
