Jul 13, 2026

Cell Replacement Therapy: A Primer

As the first stem cell therapies have gone into clinical trial to test if they are safe and effective, we have put together a primer to help our readers understand them, and we turned to Dr. David Gamm, a pioneer in stem cell therapy for blinding eye disease for help.

Whether or not stem cell therapy — also known as cell replacement therapy — is right for you, depends on how far your eye disease has progressed.

In the early stages of an inherited eye disease, like retinitis pigmentosa, where people haven’t lost many of their retinal cells, a therapy that slows progression, such as gene therapy, is the likely treatment protocol. As a disease progresses, and retinal cells are lost, other types of restorative treatments, like cell replacement therapies or optogenetics, are needed.

At the heart of cell replacement therapies are pluripotent stem cells. These are special cells that are capable of producing all the cells that we have in our own body. Pluripotent stem cells are rare but in the mid-2000s, a scientist discovered a way to reprogram adult skin or blood cells back into an embryonic or pluripotent stem cell state.

Dr. Gamm and his team have worked — successfully — on ways to turn these stem cells into a type of retinal cell called photoreceptor cells, which sense light and are lost in inherited retinal disease. But creating new photoreceptor cells in a lab and demonstrating if they can help replace lost photoreceptors is a long process.

After growing the cells, Dr. Gamm’s team needed to show that these new photoreceptors could do what photoreceptors do: they needed to detect light, produce energy and connect to other cells in the retina.

They were able to demonstrate that the photoreceptors could detect light. Moreover, they were also able to show that these cells could regrow the wires they needed to connect to other cells in the retina.

The next step in the development of stem cell therapies is to be able to scale up the manufacturing of the pluripotent cells and derived photoreceptors without losing any of the functionality, and to test them through clinical trials. The photoreceptors are injected into the subretinal space, and this needs to be done in a safe way without damaging the eye.

Over the course of five-to-six years, with funding from Fighting Blindness Canada, Dr. Gamm’s team has proved this and much more leading to a milestone clinical trial.

Currently, Dr. Gamm and his team are working with BlueRock Therapeutics LP for a first-of-its-kind cell replacement therapy clinical trial. It’s an exciting trial with the prospect of one day helping people to regain some of their lost vision.