Phase 2 CNTF Trial Shows Promise in People With MacTel

Phase 2 CNTF Trial Shows Promise in People With MacTel  

An experimental drug appears to slow neurodegeneration in people with macular telangiectasia type 2 (MacTel), according to data presented at Friday’s Retina Subspecialty Day by Emily Chew, MD, of the National Eye Institute. The findings stem from a phase 2 trial of ciliary neurotrophic factor (CNTF) in 67 participants.  

Earlier reports of neuroprotective effect confirmed. Previous studies showed that neurotrophic factors slow photoreceptor death in cell culture and animal models of retinal degeneration, including mice with MacTel-like features. In 2014, a phase 1 study showed that patients with MacTel tolerate intraocular delivery of CNTF in an encapsulated cell implant. Those patients showed better visual acuity  (average of 6.67 letters) than untreated controls after 48 months of follow-up.

Now, a prospective, single-masked, sham-controlled study conducted at 11 research centers in the United States and Australia hints at additional promise. Researchers implanted 48 eyes with retinal pigment epithelium cells engineered to express human CNTF and compared them with 51 sham-treated eyes after 12 and 24 months of follow-up.

At 24 months, CNTF slows photoreceptor loss, with few adverse events. Compared with control eyes, the treated eyes showed:

• 31% less disease progression, as measured by area of ellipsoid zone (EZ) loss
• Increase in macular thickness (compared with progressive thinning in controls)
• Stable reading speed (compared with a gradual slowing in controls)
• Similar visual acuity

The study uncovered a few adverse effects, however. Roughly 19% of eyes treated with CNTF showed delays in dark adaptation and miosis, compared with 0% of the untreated eyes. 

Despite these minor setbacks, Dr. Chew said, the treatment has a solid safety profile. Her team is preparing to corroborate the results in a pair of phase 3 trials.—Anni Griswold

Financial disclosures: None.

Disclosure key. C = Consultant/Advisor; E = Employee; L = Speakers bureau; O = Equity owner; P = Patents/Royalty; S = Grant support.