Our human retinal progenitor cell (hRPC) programme for blindness-causing diseases of the retina has been developed through our collaboration with the Schepens Eye Research Institute Massachusetts Eye and Ear, an affiliate of Harvard Medical School in Boston, USA and a world-renowned clinical centre for the treatment of retinal diseases. Our hRPC programme currently focuses on the inherited retinal disease, retinitis pigmentosa (RP). RP is a hereditary diseases of the eye that lead to progressive loss of vision due to cells in the retina becoming damaged and eventually dying. We are also assessing the potential expansion of our ophthalmology programmes into cone rod dystrophy (CRD) as part of a broader strategy to evaluate the efficacy of our hRPC therapeutic candidate across a range of genetic diseases of the eye.
In RP, there is a progressive loss of rod cells in the periphery of the retina causing night blindness that leads to loss of peripheral vision, and ultimately tunnel vision. In contrast, CRD is associated with a loss of cone cells in the retina that initially results in deterioration of central visual acuity and colour vision.
We are using proprietary human retinal progenitor cells as the basis of our programme. Pre-clinical studies carried out in disease models by the Company’s academic collaborators have demonstrated that, when transplanted into the retina, our retinal progenitor cell technology has the potential to preserve existing photoreceptors, potentially reducing or halting further deterioration of vision. In addition, the progenitor cells have been shown to mature into functional photoreceptors that engraft into the photoreceptor layer, bringing the possibility of restored vision.
Our hRPC stem cell therapy candidate for RP benefits from Orphan Drug Designation in both Europe and the US. We have worked with world-leading collaborators and academic institutions in the retinal disease field to successfully take our retinitis pigmentosa programme through pre-clinical development. We have signed an exclusive licence agreement with Fosun Pharma for the development, manufacture and commercialisation of the hRPC programme in the People’s Republic of China.
We are currently conducting a Phase I/IIa clinical trial in the US with our hRPC therapy candidate for RP. The trial design is an open-label, dose escalation study to evaluate the safety, tolerability and preliminary efficacy of the hRPC stem cell therapy candidate in patients with advanced RP. The method of administration of the hRPCs is a single sub-retinal injection. The primary endpoint of the study is safety, with patients being followed up for 12 months post-treatment with monitoring including measurements of visual acuity.
We have reported positive preliminary data in the first cohort of the Phase IIa part of this study with all three subjects in the cohort demonstrating a rapid and sustained improvement in vision compared with their pre-treatment baseline. The latest results were presented in April 2019 at the sixth annual Retinal Cell and Gene Therapy Innovation Summit in Vancouver, Canada; at most recent follow-up, subjects in the study showed a mean improvement from baseline in visual acuity of + 23 letters in the treated eye. The untreated control eyes did not show meaningful improvement (mean change from baseline of + 5 letters, range – 2 to + 12 letters).
In February 2020, we presented positive long-term data from the Phase IIa part of this study and we have now received regulatory approval to expand the Phase IIa study in both the US and the UK. We expect to have sufficient data from the Phase I/IIa study to enable the company to seek approval in the second half of 2021 to commence a single pivotal clinical study with its hRPC cell therapy candidate in RP.