Additionally, vector-induced expression of ciliary neurotrophic factor (CNTF) was shown to be neuroprotective in a mouse model of RP (Lipinski et al., 2015), yet long-term follow up of three RP patients treated with sustained-release CNTF delivered intravitreally via encapsulated cell technology implant (NT-501, Neurotech Pharmaceuticals Inc.), one of which had Usher-associated RP, showed no significant difference in visual acuity (Talcott et al., 2011). Here, CNTF is linked to retinitis pigmentosa 1.