Encouraging news for treatment targeting retinitis pigmentosa

While most people probably wouldn’t put 2020 in their list of favorite years, it’s certainly turning out to be a good one for jCyte. Earlier this year jCyte entered into a partnership with global ophthalmology company Santen Pharmaceuticals worth up to $252 million. Then earlier this week they announced some encouraging results from their Phase 2b clinical trial.

Let’s back up a bit and explain what jCyte does and why it’s so important. They have developed a therapy for retinitis pigmentosa (RP), a rare vision destroying disease that attacks the light sensitive cells at the back of the eye. People are often diagnosed when they are in their teens and most are legally blind by middle age. CIRM has supported this therapy from its early stages into clinical trials.

This latest clinical trial is one of the largest of its kind anywhere in the world. They enrolled 84 patients (although only 74 were included in the final analysis). The patients had vision measuring between 20/80 and 20/800. They were split into three groups: one group was given a sham or placebo treatment; one was given three million human retinal progenitor cells (hRPCs), the kind attacked by the disease; and one was given six million hRPCs.

jCyte CEO Paul Bresge

In an article in Endpoints News, jCyte’s CEO Paul Bresge said there was a very specific reason for this approach. “We did enroll a very wide patient population into our Phase IIb, including patients that had vision anywhere from 20/80 to 20/800, just to learn which patients would potentially be the best responders.”

The results showed that the treatment group experienced improved functional vision and greater clarity of vision compared to the sham or placebo group. Everyone had their vision measured at the start and again 12 months later. For the placebo group the mean change in their ability to read an eye chart (with glasses on) was an improvement of 2.81 letters; for the group that got three million hRPCs it was 2.96 letters, and for the group that got six million hRPCs it was 7.43 letters.

When they looked at a very specific subgroup of patients the improvement was even more dramatic, with the six million cell group experiencing an improvement of 16.27 letters.

Dr. Henry Klassen

Dr. Henry Klassen, one of the founders of jCyte, says the therapy works by preserving the remaining photoreceptors in the eye, and helping them bounce back.

“Typically, people think about the disease as a narrowing of this peripheral vision in a very nice granular way, but that’s actually not what happens. What happens in the disease is that patients lose like islands of vision. So, what we’re doing in our tests is actually measuring […] islands that the patients have at baseline, and then what we’re seeing after treatment is that the islands are expanding. It’s similar to the way that one would track, let’s say a tumor, in oncology of course we’re looking for the opposite effect. We’re looking for the islands of vision to expand.”

One patient did experience some serious side effects in the trial but they responded well to treatment.

The team now plan on carrying out a Phase 3 clinical trial starting next year. They hope that will provide enough evidence showing the treatment is both safe and effective to enable them to get approval from the US Food and Drug Administration to make it available to all who need it.

7 thoughts on “Encouraging news for treatment targeting retinitis pigmentosa

  1. Retinitis Pigmentosa (RP) is a rare genetic disorders that involves a breakdown and loss of cells in retinal cells. RP is one of the most common forms of inherited retinal degeneration. It involves multiple genes which are mutated. The common symptoms of people with RP include difficulty to see at night and loss of side (peripheral) vision. Gene therapy is not an efficiency tool to cure genetic disorders in eyes. A defective of a single gene to cause inheritance disease in human can be corrected by transferring of normal copy of DNA into cells. However, the ability of gene transfering vector to transduce the cells is limited by weakness of current technology. Therefore, stem cells transplantation by introducing the neural progenitor cells into retinal and growing them into retinal progenitor cells is an alternative choice of treatment. The early results showed the improvement of functional vision. Clinical investigation showed that transplantation of higher numbers of hRPCs (3 millions to 6 millions) can preserve the remaining photoreceptors in the eye and help patients to bounce back their vision. Stem cells are moveable, they interact with growth factors on other cells to enable them to growth and differentiate. The many cycles of growth and differentiation of progenitor stem cells are essential for immature cells to develop into mature and functioning cells. More hRPCs are introduced into retinal increasing the chances of growing progenitors to seed in the site of retinal. This may overcome the loss of stem cells which have been moved to other parts of tissues and organs. Therefore, the efficiency of hRPC treatment is very dependent on the number of hRPC seeding in retinal. The additional of essential growth factors may trigger hRPCs to speed up the time of maturation into functioning and healthy cells. The mature, healthy and functioning cells form and expand the island of vision. They are not only preserving photoreceptors but regenerating photoreceptors at the outer segment of hRPCs.

    • Not sure at this point Tom, more likely it rescued those that had not been completely damaged and protected others against destruction

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