New, previously unpublished clinical data was presented today at ISSCR 2026 demonstrating that transplanted human neural progenitor cells survived for at least one year following subretinal transplantation in patients with retinitis pigmentosa (RP), while maintaining a favorable safety profile.
Retinitis pigmentosa is a group of inherited retinal diseases that progressively causes vision loss currently has no treatment for most patients. Because thousands of different genetic mutations can cause the disease, developing mutation-specific gene therapies remains challenging. Cell-based therapies offer the potential for a gene-agnostic approach that could benefit a broader population of patients.
The Phase 1/2a clinical study funded by the California Institute for Regenerative Medicine (CIRM) evaluated the safety and feasibility of a single subretinal injection of CNS10-NPC, a human neural progenitor cell product derived from fetal brain cortex, in 13 patients with retinitis pigmentosa. Participants received either 300,000 or 1,000,000 cells and were followed for 12 months and then enrolled into a long-term follow-on protocol.
Visual acuity remained stable throughout the study, and imaging with optical coherence tomography (OCT) demonstrated that transplanted cells remained present in the subretinal space for at least one year. Cell-related adverse events included three epiretinal membranes and one persistent subretinal bleb. Overall, investigators concluded that the treatment was well tolerated and resulted in long-term cell engraftment.
"This study represents the first demonstration of long-term survival of fetal-derived neural progenitor cells in patients with retinitis pigmentosa while maintaining a favorable safety profile," said Clive Svendsen, Ph.D., Cedars-Sinai Board of Governors Regenerative Medicine Institute, USA and sponsor of the project. "Long-term engraftment is a critical milestone for the development of stem cell-based therapies for retinal disease and provides an important foundation for future studies."
Unlike gene therapies that target individual mutations, neural progenitor cell transplantation is designed as a mutation-independent strategy. Preclinical studies showed that CNS10-NPC preserved photoreceptors and vision in animal models through reducing inflammation and the release of powerful growth factors, supporting its evaluation in patients.
Although retinitis pigmentosa progresses slowly and changes in vision were not expected during the first year of the study, investigators continue to follow participants to determine whether long-term survival of the transplanted cells can help preserve vision in the treated eye over time.
"Our goal is to help patients maintain their vision for as long as possible," said Dr. Liao the clinical lead on the project. "The next critical question is whether these surviving cells can slow the continued deterioration that occurs in retinitis pigmentosa."
Svendsen also presented data on an induced pluripotent stem cell (iPSC)-derived neural progenitor product during the presentation. An iPSC-based approach could provide a more scalable therapy capable of treating substantially more patients in the future while avoiding ethical concerns associated with fetal tissue sources.
To learn more about ISSCR 2026 visit www.isscr2026.org
