Intranasal NAP (davunetide) decreases tau hyperphosphorylation and moderately improves behavioral deficits in mice overexpressing α-synuclein.

Genome-wide association studies have identified strong associations between the risk of developing Parkinson's disease (PD) and polymorphisms in the genes encoding α-synuclein and the microtubule-associated protein tau. However, the contribution of tau and its phosphorylated form (p-tau) to α-synuclein-induced pathology and neuronal dysfunction remains controversial. We have assessed the effects of NAP (davunetide), an eight-amino acid peptide that decreases tau hyperphosphorylation, in mice overexpressing wild-type human α-synuclein (Thy1-aSyn mice), a model that recapitulates aspects of PD. We found that the p-tau/tau level increased in a subcortical tissue block that includes the striatum and brain stem, and in the cerebellum of the Thy1-aSyn mice compared to nontransgenic controls. Intermittent intranasal NAP administration at 2 µg/mouse per day, 5 days a week, for 24 weeks, starting at 4 weeks of age, significantly decreased the ratio of p-tau/tau levels in the subcortical region while a higher dose of 15 µg/mouse per day induced a decrease in p-tau/tau levels in the cerebellum. Both NAP doses reduced hyperactivity, improved habituation to a novel environment, and reduced olfactory deficits in the Thy1-aSyn mice, but neither dose improved the severe deficits of motor coordination observed on the challenging beam and pole, contrasting with previous data obtained with continuous daily administration of the drug. The data reveal novel effects of NAP on brain p-tau/tau and behavioral outcomes in this model of synucleinopathy and suggest that sustained exposure to NAP may be necessary for maximal benefits.

NAP (davunetide) modifies disease progression in a mouse model of severe neurodegeneration: protection against impairments in axonal transport.

NAP (davunetide) is a novel neuroprotective compound with mechanism of action that appears to involve microtubule (MT) stabilization and repair. To evaluate, for the first time, the impact of NAP on axonal transport in vivo and to translate it to neuroprotection in a severe neurodegeneration, the SOD1-G93A mouse model for amyotrophic lateral sclerosis (ALS) was used. Manganese-enhanced magnetic resonance imaging (MRI), estimating axonal transport rates, revealed a significant reduction of the anterograde axonal transport in the ALS mice compared to healthy control mice. Acute NAP treatment normalized axonal transport rates in these ALS mice. Tau hyperphosphorylation, associated with MT dysfunction and defective axonal transport, was discovered in the brains of the ALS mice and was significantly reduced by chronic NAP treatment. Furthermore, in healthy wild type (WT) mice, NAP reversed axonal transport disruption by colchicine, suggesting drug-dependent protection against axonal transport impairment through stabilization of the neuronal MT network. Histochemical analysis showed that chronic NAP treatment significantly protected spinal cord motor neurons against ALS-like pathology. Sequential MRI measurements, correlating brain structure with ALS disease progression, revealed a significant damage to the ventral tegmental area (VTA), indicative of impairments to the dopaminergic pathways relative to healthy controls. Chronic daily NAP treatment of the SOD1-G93A mice, initiated close to disease onset, delayed degeneration of the trigeminal, facial and hypoglossal motor nuclei as was significantly apparent at days 90-100 and further protected the VTA throughout life. Importantly, protection of the VTA was significantly correlated with longevity and overall, NAP treatment significantly prolonged life span in the ALS mice.

D-NAP prophylactic treatment in the SOD mutant mouse model of amyotrophic lateral sclerosis: review of discovery and treatment of tauopathy.

Davunetide (NAP) is a leading drug candidate being tested against tauopathy. Davunetide is an eight-amino-acid peptide fragment derived by structure-activity studies from activity-dependent neuroprotective protein, activity-dependent neuroprotective protein (ADNP). ADNP is essential for brain formation. ADNP haploinsufficiency in mice results in tauopathy and cognitive deficits ameliorated by davunetide treatment. This article summarizes in brief recent reviews about NAP protection against tauopathy including the all D-amino acid analogue-D-NAP (AL-408). D-NAP was discovered to have similar neuroprotective functions to NAP in vitro. Here, D-NAP was tested as prophylactic as well as therapeutic treatment for amytrophic lateral sclerosis (ALS) in the widely used TgN(SOD1-G93A)1Gur transgenic mouse model. Results showed D-NAP-associated prophylactic protection, thus daily treatment starting from day 2 of age resulted in a prolonged life course in the D-NAP-treated mice, which was coupled to a significant decrease in tau hyperphosphorylation. These studies correlate protection against tau hyperphosphorylation and longevity in a severe model of ALS-like motor impairment and early mortality. NAP is a first-in-class drug candidate/investigation compound providing neuroprotection coupled to inhibition of tau pathology. D-NAP (AL-408) is a pipeline product.

Tau and caspase 3 as targets for neuroprotection.

The peptide drug candidate NAP (davunetide) has demonstrated protective effects in various in vivo and in vitro models of neurodegeneration. NAP was shown to reduce tau hyperphosphorylation as well as to prevent caspase-3 activation and cytochrome-3 release from mitochondria, both characteristic of apoptotic cell death. Recent studies suggest that caspases may play a role in tau pathology. The purpose of this study was to evaluate the effect of NAP on tau hyperphosphorylation and caspase activity in the same biological system. Our experimental setup used primary neuronal cultures subjected to oxygen-glucose deprivation (OGD), with and without NAP or caspase inhibitor. Cell viability was assessed by measuring mitochondrial activity (MTS assay), and immunoblots were used for analyzing protein level. It was shown that apoptosis was responsible for all cell death occurring following ischemia, and NAP treatment showed a concentration-dependent protection from cell death. Ischemia caused an increase in the levels of active caspase-3 and hyperphosphorylated tau, both of which were prevented by either NAP or caspase-inhibitor treatment. Our data suggest that, in this model system, caspase activation may be an upstream event to tau hyperphosphorylation, although additional studies will be required to fully elucidate the cascade of events.