Using viral-mediated gene delivery to model Parkinson's disease: do nonhuman primate investigations expand our understanding?

In this review, we consider the use of nonhuman primate (NHP) models of Parkinson's disease (PD) produced using viral-mediated gene delivery and information they provide in comparison to other model systems in rodents and NHPs. To date, rodent and NHP PD models have found it difficult to fully recapitulate the human disorder and, therefore, provide little actual insight into disease progression. The viral-mediated gene delivery method for α-synuclein has been shown to produce a parkinsonian rodent and NHP. This novel viral-mediated gene transfer model in the NHP appears to provide a significant advance beyond neurotoxicant models, by more closely mimicking the more chronic time course of developed behavioral deterioration and neuropathology. Although we agree that the use of these novel methods inducing parkinsonian NHPs may provide relevant treatment insights, beyond those of more standard PD models, we remain cautious as to the preclinical models' ability to predict outcomes in human trials. In specific cases of certain novel medical therapeutics, therefore, we also consider the phase 0 clinical trial as offering an alternative to the currently non-predictive preclinical models, including those in the NHP.