Protein therapies for the eye must be dosed as frequent injections. Gene therapy offers one-time treatment, but must also be administered by injection. Neurotech Pharmaceuticals’ gene therapy comes in a surgical implant, and it’s now the first FDA-approved treatment for a rare vision-loss disorder.
The approval handed out on March 5 covers the treatment of macular telangectasia type 2 (MacTel) in adults. The Neurotech therapy, known in development as revakinagene taroretcel, will be marketed under the brand name Encelto.
There are two types of MacTel. In type 2, tiny blood vessels in the center of the retina become abnormal and may widen, according to the American Academy of Ophthalmology. The disease can also lead to the formation of new blood vessels under the retina that leak fluid. Over time, patients experience blurred vision and loss of central visions. MacTel type 2 affects both eyes, but not always with the same severity. The disease typically presents in middle-age adults. Its cause is unknown.
Protein therapies for eye disorders require frequent injections because those engineered proteins have short half-lives. Neurotech, based in Cumberland, Rhode Island, has developed an alternative way to deliver therapeutic proteins to the retina. The privately held company’s platform technology is based on a line of cells that that can be engineered to continuously produce therapeutic proteins. The technology covers several classes of proteins, including antibodies, fusion proteins, and growth factors.
For MacTel, the Neurotech technology delivers human ciliary neurotrophic factor (CNTF), a signaling protein produced in the body that promotes neuron survival. This protein has been studied for applications in neurodegenerative diseases and retinal degeneration. Neurotech’s approach employs a capsule surgically implanted in the eye during an outpatient procedure. Each capsule contains as many as 440,000 allogeneic retinal pigment epithelial cells, which express engineered versions of CNTF.
The capsule component of Encelto is semi-permeable, which allows essential nutrients to enter and therapeutic proteins to leave, according to Neurotech. The exterior membrane protects the encapsulated cells from being attacked by the patient’s immune system. While Encelto’s mechanism of action is not completely understood, the proteins from this therapy are thought to trigger events that promote the survival of photoreceptors in the eye.
Neurotech contends that its approach offers several advantages. The therapeutic protein is produced and released right in the eye, which means a relatively small amount of protein is needed compared to what would be required from a time-controlled drug delivery system. The Neurotech technology provides continuous and long-term secretion of therapeutic protein. Furthermore, treatment may be terminated by simply retrieving the implant.
Regulatory review of Encelto was based on data from two Phase 3 clinical trials. In both studies, results showed statistically significant and clinically meaningful slowing of disease progression measured at 24 months. The implant was also shown to be safe and well tolerated in both clinical trials.
“I have seen the impact that MacTel can have on patients and their quality of life,” Dr. Charles Wykoff, director of research at Retinal Consultants of Texas and an investigator in the Encelto clinical trials, said in Neurotech’s approval announcement. “Now with an FDA-approved treatment, I am confident that Encelto will be able to meaningfully slow disease progression for many patients affected by MacTel, allowing them the opportunity to preserve more functional vision over time.”
Neurotech has not disclosed a price for Encelto. The company expects the product, its first approved therapy, will become available in June.
Photo: Karen Bleier /AFP, via Getty Images
