 In addition, mice models have shown the dying neurons exposed to trophic factors can be rescued.Neurturin is an example of a trophic factor that is difficult to utilize clinically because of its inability to cross the blood-brain barrier of the CNS (central nervous system).Ceregene sponsored a double-blind phase II clinical trial of CERE-120, a viral vector mediated gene transfer drug that allows for the continuous delivery of neurturin to the nigrostratial system.