CNTF implant shows potential for treatment of retinitis pigmentosa

LINCOLN, R.I. — An intraocular implant from Neurotech Pharmaceuticals significantly preserves cone photoreceptors in patients with retinitis pigmentosa, according to a press release from the company.

NT-501 is an intraocular implant made of human cells that are genetically modified to secrete ciliary neurotrophic factor (CNTF). The prospective study enrolled two patients with retinitis pigmentosa and one patient with Usher syndrome type 2 who were selected from Neurotech's phase 2 study of the implant in patients with early-stage retinitis pigmentosa, the release said.

One eye of each patient was implanted with NT-501, and the fellow eye received sham treatment. Photoreceptor loss was evaluated with adaptive optics scanning laser ophthalmoscopy (AOSLO) for 2 years after implantation, the release said.

The study results, published in Investigative Ophthalmology & Visual Science, revealed that no eyes treated with NT-501 had cone spacing or decrease in cone density. In addition, all eyes treated with NT-501 showed statistically significant cone preservation when compared with sham-treated eyes, the release said.

Cone spacing in the sham treatment eyes increased by 2.9% more per year (P < .001) and cone density decreased by 9.1% more per year (P = .002) when compared with treated eyes.

"These results suggest that AOSLO may play a meaningful role in the early assessment of photoreceptor loss due to retinitis pigmentosa well before serious functional loss is detected by standard measures of visual function, and that NT-501 may play an important neuroprotective role," Paul Sieving, MD, PhD, director of the National Eye Institute and principal investigator of a phase 1 study of the implant, said in the release.