Development of a non-invasive NGF-based therapy for Alzheimer's disease. Current Alzheimer Research 6: 158

Nerve growth factor (NGF) deficits are linked to Alzheimer's Disease (AD), due to the role of NGF on basal forebrain cholinergic neurons (BFCN). We have further established that a disequilibrium in NGF signaling and/or processing from its precursor proNGF is also directly and causally related to the aberrant activation of an amyloidogenic route to neurodegeneration. The therapeutic potential of using human NGF to provide a long-lasting cholinergic trophic support, thereby preventing or slowing cognitive decline in AD patients, has therefore a strong rationale. However, a simple and practical means of delivering NGF to the brain in a safe and long-term manner, limiting the undesired adverse effects of NGF in activating nociceptive responses, has represented a significant challenge. For this reason, pilot clinical studies have been performed so far with invasive approaches requiring neurosurgery. We obtained a proof of principle, in neurodegeneration animal models, of an alternative, non-invasive delivery of NGF through an intranasal route, which facilitates access of NGF to the central nervous system (CNS), while minimizing the biodistribution of NGF to compartments where it activates undesired effects, such as pain. The ideal NGF product for a non invasive NGF-based therapy would be a recombinant NGF that, while exhibiting an identical biological activity to that of human NGF, can be traced, against the endogenous NGF, in order to optimize the therapeutical dose range and meet the required therapeutic window. We describe an engineered mutein of hNGF, hNGF-61, that is selectively recognized, against endogenous NGF, by a specific antibody. hNGF-61 mutein has an identical potency and bioactivity profile as hNGF, in vitro and in vivo. Moreover, hNGF-61 and hNGF are equally effective in rescuing the behavioral and neurodegenerative phenotype in adult and aged AD11 anti-NGF mice. Finally, we demonstrated that intranasally delivered hNGF-61 is significantly more effective than ocularly applied hNGF-61, to determine phenotypic rescue in AD11 mice. The development of hNGF-61 towards clinical applications in AD patients is under way.