Abstract
Purpose :
Retinal cell replacement therapy is an attractive therapeutic option for dry AMD and the use of human pluripotent stem cell-derived RPE has rapidly advanced to first-in-human clinical trials for macular degeneration. Here, we provide systematically conducted experimental data for establishing safety and efficacy of an iPSC-derived allogeneic RPE cell product prior to its clinical use.
Methods :
A clinical-grade iPSC line was differentiated following our in-house protocol. A series of selection steps were carried out on days ~45 and ~90 for enrichment and scale up respectively. RPE cells at different levels of maturity were tested for efficacy using RCS rats. Following subretinal injection of increasing doses of cells, OKT was assessed at P60 and P90. Retina sections were stained with HNM to detect human cells, and cone arrestin to evaluate photoreceptor preservation. A tumorigenicity study was conducted in immunodeficient RNU rats and SCID mice to ensure safety. Finally, a non-human primates (NHP) study was employed to determine the optimal human dose for phase 1 clinical studies. 0.1-0.3M cells were transplanted using 38G needle and microdose injector connected to the vitrectomy machine.
Results :
Previously established lab protocol was modified by incorporating additional enrichment steps to increase the purity and reduce residual immature or progenitor cells in the final product, validated by transcriptomic analysis and immunophenotyping. Stability of RPE cells in its cryopreserved state was confirmed for up to 1 year. Subretinal delivery of escalating doses of the RPE cell suspension in RNU rats did not produce tumors 4 months post-injection and cells were present in the injection site with intact ONL. RPE transplanted into immune suppressed RCS rats showed neuroprotection and rescue of visual function. Toxicology and tolerability studies were successfully completed in rabbits and NHP.
Conclusions :
In summary, these results support robust safety of subretinally transplanted RPE cells without any risk of toxicity or tumor growth and strong efficacy. Optimal human dose and delivery method was identified through NHP studies. Lastly, our results comply with the required preclinical checkpoints of PSC-based therapies as per regulatory guidelines for first-in-human clinical trial.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.