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Retinal Pigment Epithelial Cell Program

Retinal degeneration can cause a variety of blinding diseases, including retinitis pigmentosa, Stargardt’s disease (juvenile macular degeneration), age-related macular degeneration (AMD) and other degenerative diseases of the retina. ACT has developed an embryonic stem cell-based therapy which provides a promising treatment option for a variety of these incurable eye diseases.

Retinal Degenerative Conditions

AMD afflicts more than 30 million people worldwide and is the leading cause of blindness in people over age 60 in the U.S. As average life expectancy continues to rise, it is predicted that the incidence of AMD will only continue to rise in tandem. Atrophic (dry) AMD, the most prevalent form accounting for 90% of all cases, is characterized by the degeneration of the retinal pigment epithelium (RPE) and the neuroretina. End stage AMD occurs when the RPE completely degenerates, which further induces secondary cell death of macular rod and cones.

Dry AMD represents a $25-30 billion market in the U.S. and Europe alone, and there are currently no approved therapies available for this condition.

Stargardt’s disease is an autosomal recessive form of juvenile macular degeneration. The pathophysiology includes the death of photoreceptors due to the loss of a functional RPE, resulting in blindness. The patients are typically affected in the first or second decade of their life, and there is currently no effective therapy available.

The Retinal Pigment Epithelium (RPE)

The retinal pigment epithelium (RPE) is a highly specialized tissue that is located between the choroids and the neural retina. RPE cells support, protect and provide nutrition for the light sensitive photoreceptors.

Many retinopathies (retinal diseases) are caused by the degeneration or malfunction of the RPE, and as a result, an effective treatment option for these conditions may be the replacement of the destroyed RPE cells with healthy RPE cells. Embryonic stem cells could provide a promising therapy to replace the damaged RPE cells and to sustain visual function for patients suffering from these progressive diseases.

The Promise of Stem Cell-Derived Retinal Pigment Epithelial (RPE) Cells

Embryonic stem cells can differentiate in any cell type and due to its unlimited self-renewal capabilities they also provide an unlimited source. RPE cells derived from human embryonic stem (h-ES) cells are terminally differentiated and express all molecular markers found in vivo in RPE cells. Proof of concept studies using RPEs have been conducted in collaboration with the Casey Eye Institute at Oregon Health and Science University in multiple animal models with photoreceptor degeneration.

hESC-derived RPE cells have the capacity to support photoreceptor survival and preserve visual function after sub-retinal transplantation. Visual performance improved by up to 100% over untreated control, demonstrating the potential for hESC-derived RPE cells to slow disease progression and to restore visual function manner.

Clinical Development

ACT is enrolling patients in two Phase 1/2 clinical trials to test the safety of the hESC-derived RPE cellular therapy for Stargardt's Macular Dystrophy (SMD) and for Dry Age-Related Macular Degeneration (Dry AMD). Both the FDA and the European Medicines Agency (EMA) have also granted ACT's RPE cells "Orphan" status for treatment of Stargardt's Disease.

ACT’s hESC-derived RPE cells are produced following current Good Manufacturing Practices (cGMPs) and current Good Tissue Practices (cGTPs).