Clinical Trials and Emerging Research Show Promise for LCA Treatments

Forty clinical trials and a lot of pre-clinical research into LCA treatments show promising pathways to discovering the next LUXTURNA®, according to Shannon Boye, PhD, the opening speaker for the Virtual VISIONS 2020 conference, presented earlier this summer by the Foundation Fighting Blindness. 

The breakthrough drug developed by Spark Therapeutics marked a milestone in the history of genetic research as the first gene therapy in the United States for any inherited disease and as the first to treat one of the more than 25 forms of Leber congenital amaurosis (LCA).

Boye, along with Foundation Chairman of the Board David Brint and Foundation Chief Executive Officer Benjamin Yerxa  PhD, kicked off the three-day, first-time virtual conference, the Foundation’s major annual gathering. Rather than convening in person, the event’s speakers, exhibitors and more than 1,600 attendees participated through an online app, due to concerns surrounding the coronavirus pandemic.

Brint said that the 40 clinical trials and more emerging treatments for various IRDs span the disease profile.

“No matter what your disease is, these hopefully will be able to restore vision,” Brint said. “In the next 10 years, we have an opportunity to bring many more vision-saving treatments into and through the pipeline and across the finish line.”

Yerxa said the topic of genetic therapies would be good to lead off with because of the sheer variety of innovative programs and approaches to each therapeutic challenge.

“There’s essentially a revolution happening right now in personalized medicine and genetic therapies in general,” Yerxa said.

Boye, an assistant professor in the Department of Ophthalmology at the University of Florida, addressed the audience in the beginning session called: “Mission Possible! What’s Next?”

She discussed three major strategies in treating LCA and other IRDs: Gene supplementation or gene replacement therapy, RNA therapeutics and gene editing. 

Boye set up an analogy to better understand the complexities of these strategies, saying we all have little letters in our bodies called DNA. Subunits of those letters – that DNA – are genes. RNA carry the instructions from DNA for making proteins, the building blocks of life.

“They act alone or in concert with a bunch of other proteins to perform essential functions.”

Continuing her letters analogy, Boye said, imagine a friend texts you: ‘Please take out the dog.’ You get that message and perform that function because letters combined correctly to tell you to take the dog out. 

If only the word ‘Please’ appears on your phone screen, you don’t take the dog out.

Or, if the ‘d’ is pushed and an ‘l’ comes out, sending the message, ‘Please take the log out,’ “you then have a mess to clean up,” she quipped.  

In the first strategy of gene supplementation or gene replacement, the right protein needs to be expressed in the patient’s retina. 

The letters need to be correctly sequenced to generate a coherent message, in this case, telling a protein to perform an important function. Any break in that cascade of events can cause visual impairment. 

The gene replacement therapy LUXTURNA is a human-engineered virus containing copies of the corrective gene that doctors deliver through a subretinal injection so the cells can make the originally missing protein.

“You deliver the right letters that make the right message and the right protein,” she said. “That’s a pretty simple concept. That’s LUXTURNA.”

Developed to improve vision in people with LCA2* caused by a mutation in the RPE65 gene, LUXTURNA received Food and Drug Administration approval for  use in humans in December 2017. 

One area of Boye’s research as Associate Division Chief of Cellular and Molecular Therapeutics is entering into a Phase 1/2 clinical trial, applying the same premise for mutations in the GUCY2D gene that causes LCA1. 

“It’s early,” she said. “But this is an example of another perhaps next LUXTURNA being right around the corner.”

She cited similar research moving forward on other IRDs, including Retinitis Pigmentosa (RP), Choroideremia, and Bardet Biedl Syndrome (BBS). 

The second strategy is a form of RNA therapeutics that uses antisense oligonucleotides (AONs) – short, single-stranded DNA  molecules that interact with messenger RNA to correct translation of a targeted gene. Think of an AON as an autocorrect feature that binds to the ‘l’ in log and changes to a ‘d’ for dog.

Promising pre-clinical work now in Phase 2/3 for CEP290 or LCA10 also is coming out of Rob Collin’s research group in The Netherlands, Boye said.

Another AON program underway addresses a form of Usher Syndrome. 

The third strategy – the newest and most exciting – is gene editing. A guide RNA is used to drag a special enzyme to a region in the DNA that contains the mutation, and the enzyme cuts the DNA, like molecular scissors. 

Researchers are exploring a host of gene editing variations, including cutting out a specific area of DNA and replacing it with the right letters to make a coherent message. The lab work has created paths to address a range of IRDs, including CEP290,  Usher Syndrome,  RP, Stargardt Disease and Choroidermia.

“There’s an absolute exponential increase in the therapies that are being developed,” she said.

These strategies are not limited to the disease conditions under discussion and can be more widely applied to a number of genes and conditions.

Addressing those who do not have RPE65 or LCA2 for which a treatment exists, Boye said, with all of this research in progress, “that one day, there’s going to be a LUXTURNA for your inherited retinal disease, too.”