Ciliary neurotrophic factor (CNTF) for human retinal degeneration: phase I trial of CNTF delivered by encapsulated cell intraocular implants

Proc Natl Acad Sci U S A. 2006 Mar 7;103(10):3896-901. doi: 10.1073/pnas.0600236103. Epub 2006 Feb 27.


Neurotrophic factors are agents with a promising ability to retard progression of neurodegenerative diseases and are effective in slowing photoreceptor degeneration in animal models of retinitis pigmentosa. Here we report a human clinical trial of a neurotrophic factor for retinal neurodegeneration. In this Phase I safety trial, human ciliary neurotrophic factor (CNTF) was delivered by cells transfected with the human CNTF gene and sequestered within capsules that were surgically implanted into the vitreous of the eye. The outer membrane of the encapsulated cell implant is semipermeable to allow CNTF to reach the retina. Ten participants received CNTF implants in one eye. When the implants were removed after 6 months, they contained viable cells with minimal cell loss and gave CNTF output at levels previously shown to be therapeutic for retinal degeneration in rcd1 dogs. Although the trial was not powered to form a judgment as to clinical efficacy, of seven eyes for which visual acuity could be tracked by conventional reading charts, three eyes reached and maintained improved acuities of 10-15 letters, equivalent to two- to three-line improvement on standard Snellen acuity charts. A surgically related choroidal detachment in one eye resulted in a transient acuity decrease that resolved with conservative management. This Phase I trial indicated that CNTF is safe for the human retina even with severely compromised photoreceptors. The approach to delivering therapeutic proteins to degenerating retinas using encapsulated cell implants may have application beyond disease caused by genetic mutations.

Publication types

  • Clinical Trial, Phase I
  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Aged
  • Cell Line
  • Ciliary Neurotrophic Factor / administration & dosage*
  • Ciliary Neurotrophic Factor / biosynthesis
  • Ciliary Neurotrophic Factor / genetics
  • Ciliary Neurotrophic Factor / therapeutic use
  • Diffusion Chambers, Culture*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pigment Epithelium of Eye / cytology
  • Pigment Epithelium of Eye / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • Recombinant Proteins / therapeutic use
  • Retinal Degeneration / drug therapy*
  • Retinal Degeneration / pathology
  • Retinal Degeneration / physiopathology
  • Safety
  • Transfection


  • Ciliary Neurotrophic Factor
  • Recombinant Proteins