More than seven million people in the US struggle to see. While most are not completely blind they have difficulty with, or simply can’t do, daily tasks most of us take for granted. CIRM has committed more than $100 million to 17 projects trying to solve this unmet medical need. Two of those projects have begun clinical trials testing cell therapies in patients. (Both were featured in the “Stem Cells in Your Face” video we released yesterday.)
The two diseases targeted by those therapies bookend the spectrum of patients impacted and their symptoms. Retinitis pigmentosa (RP) strikes young people, wiping out peripheral version first and only later attacking the central vision. Age related macular degeneration (AMD), the leading cause of blindness in the elderly, slowly erodes the central vision.
The RP team
Researcher Henry Klassen at the University of California, Irvine, was told as a kid he might have RP. He didn’t. Instead he has spent more than 25 years searching for cures for blindness, including RP. When asked about the dogged determination it has required to get to the point of the CIRM-funded clinical trial, he naturally fell into visual metaphors.
“It really has been difficult with many opportunities to lose the path, but I think I just had a singular vision of what was possible and when you see the possibility and you know it’s there, you feel this deep responsibility for acting even if other people aren’t seeing what you’re seeing.”
Klassen’s team has treated eight patients in the first part of the clinical trial, all with severe vision loss. If the monitoring of those patients shows the therapy to be safe the team should be given permission to treat a second group of patients, this time people with less progressed vision loss.
The therapy involves injecting nerve stem cells into the fluid of the eye. There the cells release various proteins and factors that promote the health of the photo-receptors that become non-functional in RP.
Rosie Barrero lives with RP’s limitation every day. Although in hindsight she believes the progressive disease started as a young child, she was not diagnosed until the age of 26. Now, with three children of her own to help raise, she can only see shadows and shapes to maneuver, but can not recognize the faces of family and friends—something that can make some new acquaintances think she is a bit of a snob when she unknowingly ignores them.
“A cure for RP would mean independence for me. It would mean I would play a bigger role as a parent; I would do more things, I would help out more.”
Second team aims for AMD
A multi-center team lead by Mark Humayun and David Hinton at the University of Southern California and Dennis Clegg at the University of California, Santa Barbara, are the force behind the second CIRM-funded clinical trial . They developed an approach to treating dry AMD with stem cells fairly different from other teams around the world that are also in the midst of clinical trials. While the other groups generally inject cells from various sources directly into the eye, the California team combines cells with a synthetic scaffold to hold them in place in the eye.
Most of the clinical work in AMD seeks to replace a monolayer of cells under the retina that support that critical part of our eye where the photoreceptors reside. That layer of cells, called the Retinal Pigmented Epithelium (RPE) degenerates in AMD for unknown reasons and without its support structure the photoreceptors start to give out. Rather than hoping injected cells will find their way to where they need to be, the CIRM-funded team grows them on a thin synthetic scaffold. They then implant that three-by-five millimeter piece of plastic under the retina where it is needed.
“We’ve designed the scaffold material—the little piece of plastic that we’re putting the cells on—to be very, very thin such that anything can move through it that needs to move through,” said UC Santa Barbara’s Dennis Clegg. “And there are a number of nutrients that are delivered to the RPE cells from the corriocapillaris, which is the system of blood vessels underneath.”
USC’s Humayan presented more detail about the science behind the project at one of our “Spotlight” presentations very early in the project in 2009, and his clinical collaborator at USC, David Hinton provided clinical perspective at the same session.
Others working on the goal
A collaborating team led by Pete Coffey in London has begun a clinical trial for the more aggressive wet form of AMD. Coffey splits his time between University College London and UC Santa Barbara.
The clinical trial teams have formed companies or collaborated with corporate partners to manage the clinical trials and further development of the technology—something CIRM considers critical to moving therapies forward for patients. jCyte manages the RP work and Regenerative Patch Technologies manages the AMD project. Pfizer is involved with the London project.
Somewhere close to a dozen teams around the world are trying various forms of stem cell-based therapies to fill the huge patient need created by AMD. Clegg suggests this is not redundant but rather a great thing for patients:
“Sometimes I like to compare it to the beginning of the space program. There are a lot of ways you can build a rocket ship. We don’t know which one is going to get to the moon, but it’s worth trying all of these to see what works best for patients.”