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Human retinal progenitor cells (hRPCs) used to treat first patient in a US Phase I/II study for retinitis pigmentosa

A US Phase I/II study has reported the successful injection of a first patient with human retinal progenitor cells (hRPCs) developed for the therapeutic treatment of retinitis pigmentosa. The procedure is understood to have involved a single sub-retinal injection of hRPC cells at the Massachusetts Eye and Ear Hospital in Boston, a teaching affiliate of Harvard Medical School (HMS). The first patient was reported to have being discharged from hospital on the same day. The therapeutic approach had previously being shown in preclinical models to improve visual acuity and to be capable of engrafting into the retina facilitating differentiation of the cells into viable photoreceptors. The sponsors of the study, ReNeuron, a UK based company, have suggested their approach may be suitable to treat a wide population of retinitis pigmentosa patients regardless of the multiple causative mutations underlying the disease. If validated the hRPC treatment could provide a significant advantage over developing single gene treatments targeting individual gene mutations on a patient-by-patient basis.


Formally entitled a “First-in-human Phase I/IIa, Open-Label, Prospective Study of the Safety and Tolerability of Subretinally Transplanted Human Retinal Progenitor Cells (hRPC) in Patients With Retinitis Pigmentosa (RP)”, the study is designed as a dose escalation trial in which participants with RP will receive a single sub-retinal injection of hRPC cells in one eye to evaluate safety and tolerability. The trial has an enrolment target of 15 participants with retinitis pigmentosa each of who will receive a single uni-ocular subretinal implantation of one of three doses of hRPCs. Treated eyes will be tracked for ocular or systemic adverse events for 12 months while testing will also evaluate any preliminary signals of efficacy. The sponsoring company previously secured Orphan Drug Designation in both the US and the EU and Fast Track designation with the US FDA.


The potential for stem cell therapies has gained increasing momentum in recent years with well over a dozen commercial entities now in operation targeting a broad range of indications. The sponsor of the hRPC study (ReNeuron) has built considerable know-how and expertise in translating their opportunity for stem cell treatments into an industrial process. They have developed full manufacturing scale-up and quality-testing processes having invested considerably in forging the capability to produce “off-the-shelf” commercial grade cell banks and materials. The lead therapeutic of the company is a stem cell treatment for patients left disabled as a result of stroke and is currently under clinical development in a Phase 2 trial termed “PISCESII”. According to the company, the PISCESII study is designed to test the efficacy of a manufactured neural stem cell line (CTX cells) delivered by injection intracranially via stereotaxic neurosurgery in up to 41 patients with paresis of an arm following an ischaemic middle cerebral artery (MCA) stoke.


Safety and tolerability data from the retinitis pigmentosa Phase I portion of the study is expected towards the end of FY2016, with preliminary efficacy data scheduled for the first half of 2017. Commenting on the clinical trial milestone, Eric Pierce, MD, PhD, the Principal Investigator for the clinical trial, stated: “We are delighted to have treated the first patient in this important Phase I/II clinical trial. The human Retinal Progenitor Cells being tested in the study are promising since they can make photoreceptors. The implanted cells may not only prevent degeneration of patients’ vision but may possibly restore some vision by replacing degenerated photoreceptor cells. We look forward to reporting future progress with this study in the months ahead.”