NT-501 demonstrates strong biologic effect on photoreceptors in RP studies

Lincoln, RI

-An intraocular implant, NT-501, has demonstrated a strong biologic effect in two phase II clinical trials for retinitis pigmentosa (RP), according to a release issued by Neurotech Pharmaceuticals. The implant consists of human cells that have been genetically modified to secrete ciliary neurotrophic factor (CNTF), the company said.

“CNTF has the potential to help people with RP and other photoreceptor degenerations,” said Paul Sieving, MD, PhD, director of the National Eye Institute and principal investigator of Neurotech’s phase I study of NT-501 in RP. “These studies are important as they present an opportunity to move the field forward.”

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The two phase II studies were multicenter, randomized, double-masked, sham-controlled, dose-ranging trials designed to evaluate the safety and efficacy of NT-501 in patients with RP. The first trial consisted of 65 patients with later-stage RP (defined as patients with RP and who have vision between 20/63 and 20/320), and the second trial consisted of 67 patients with earlier-stage RP (defined as patients with RP and who have vision better than 20/63). In both studies, each patient received either a high- or low-dose NT-501 implant in one eye and a sham treatment in the fellow, control eye.

Best-corrected visual acuity was evaluated as a primary endpoint for patients in the later-stage RP group, and visual field sensitivity was evaluated in the patients in the earlier-stage group. At 12 months, no trend in visual benefit was observed in either study for these functions, according to the release. All patients will be monitored for another 6 to 18 months per protocol. No serious adverse events associated with NT-501 were reported, and NT-501 and the surgical procedure were well tolerated.

“We are hopeful that the biological changes observed in RP patients treated with NT-501 will lead to a benefit in visual function,” said David Birch, PhD, director of the Retina Foundation of the Southwest and lead investigator for the RP studies. “However, the progression of this disease is slow, and we have not seen a visual benefit in the treated eye relative to the control eye over this relatively short 12-month time period.”

Ted Danse, president and chief executive officer of Neurotech, said: “We are encouraged with the consistent biological effects of CNTF observed in these two phase II RP studies. We will continue to follow the patients in these studies, and [we] plan to discuss the results and the clinical development path with the FDA.”