An inherited eye disease known as retinitis pigmentosa (RP) affects 1.5 million people worldwide, causing blindness in many by age 40.
Researchers have labored for many years to find ways to prevent deterioration of sight or to restore vision to those patients. Now a novel type of stem cell treatment for the disease is under investigation by UCI Health researchers at the Gavin Herbert Eye Institute.
After showing promising results in a Phase 1 clinical study, the U.S. Food and Drug Administration approved a Phase 2 clinical trial to evaluate the dosages, safety and effectiveness of treatment involving a type of stem cell called progenitor cells.
UCI Health ophthalmologist Dr. Mitul C. Mehta, who treats diseases of the retina at the Gavin Herbert Eye Institute, is the lead investigator in the second phase of the clinical trial, which is just wrapping up.
Live Well spoke with Mehta, who is also an assistant professor of ophthalmology in the UCI School of Medicine, about the treatment and how it works.
He also explains the path toward potential FDA approval and the tantalizing possibility of preserving and even restoring vision in people with RP.
What is RP?
RP is actually multiple diseases that result from changes in any one of more than 50 different genes that destroy the light-sensing cells in the eye. That’s one of the challenges we have faced.
A device called the Argus II Retinal Prosthesis — also known as the bionic eye — produces some vision when implanted in people who had no vision or perceived only light.
Vitamin A palmitate may help RP patients prolong vision. All sorts of treatments have been tried for RP, but nothing has really worked. That’s why this stem-cell approach is truly exciting.
What is the new treatment you’re studying?
The therapy was developed in the lab of my colleague, UCI ophthalmologist and researcher Dr. Henry Klassen, whose studies show that progenitor cells can slow damage progression and may spark the growth of new retinal cells.
The Phase 2 study evaluates the effectiveness of progenitor cells in improving the vision of people with RP.
More than 80 volunteers, whose vision ranged from 20/80 to 20/800, received injections in the vitreous of the eye. The vitreous is the gel-like substance that makes up much of the inner eye.
Participants, most of whom had severe peripheral vision loss, were randomized into three groups:
- One-third were injected with three million cells each
- One-third received six million cells each
- One-third served as a control group and got a placebo injection
To eliminate bias, two physicians gave the injections. We also didn’t know the type of injection or the dosages people received.
What are progenitor cells?
Progenitor cells start as embryonic stem cells, then are modified in the lab to produce specific growth factors important to fostering vision.
How does the treatment work?
Participants are given a single injection in one eye. The progenitor cells come together to form a new organ-like mass in the eye that we believe helps dormant, damaged cells work better.
What are the results so far?
We haven’t analyzed the results of this phase of the study yet. But the Phase 1 study of the treatment’s safety was promising enough that the FDA approved Phase 2.
We were also able to offer to inject the second eye of participants in the first phase, and most were delighted to accept.
So far, the treatment appears to be beneficial and long-lasting, but we think people may need injections every year or two to maintain the improvement.
How have participants reacted?
For some participants, we’ve seen remarkable improvement. One of my patients had so much trouble seeing she couldn’t find the door.
After the treatment, she walked into my exam room without anyone helping her, sat down and said, “That’s a very nice green tie you’re wearing.”
I have no way of knowing what dosage she had, but she improved so much that it was shocking. Another patient who couldn’t see fingers in front of her face is now able to see her children.
What are the next steps?
Over the next six months, we’ll finalize and analyze the data. There is one more clinical trial — a Phase 3 — that the FDA requires before it will approve the treatment for general use.
Once the FDA approves a research protocol and progenitor cells are developed commercially, that clinical trial can get underway at multiple sites with a greater number of participants.
I can’t say how long before the treatment would be available outside of a clinical trial.
How has this research affected you?
I became a doctor to help people. This research is so game-changing for people’s lives.
It’s impossible to imagine what your life would be like if you couldn’t even see the person standing next to you. It’s super-exciting to be part of this leading-edge work.
How RP Stem Cell Therapy Works
Retinitis pigmentosa is marked by the slow decay of the photoreceptors — the rods and cones that turn light into signals sent to the brain. The investigational therapy involves:
- Embryonic stem cells called progenitor cells are modified in the lab to produce specific growth factors that facilitate vision.
- In the clinical trial, progenitor cells or a placebo are injected into the vitreous, the gel-like substance that fills the inner eye.
- The progenitor cells are designed to replace damaged rods and cones, reversing the course of RP.