A Phase 2 clinical trial was used to see if injecting human retinal progenitor cells (derived from stem cells) can improve vision and visual fields in people with retinitis pigmentosa (RP). The retinal progenitor cells may activate and preserve retinal cells in patients with RP. The results from the clinical trial suggest that this treatment could enhance vision and the visual field in patients with RP whose cells can be restored. The trial had 74 participants split into 3 groups: patients who were injected with 3 million cells, patients who were injected with 6 million cells and a control group. The results of the study show that the 6 million cell dosage was the most effective. There was improvement in kinetic visual fields, contrast sensitivity and the ability to navigate in a low luminance maze. The injection also had a good safety profile. Phase 3 trials will begin later in 2022. There are still questions as to which patients would most benefit from this treatment.
What this means for Usher syndrome: Because vision loss in Usher syndrome is caused by retinitis pigmentosa, retinal progenitor cell transplants could be a possible treatment used to preserve retinal cells. This could lead to improved vision and visual fields. More research needs to be done, but this is a future candidate therapy.