Joel A. Saydoff

Oral uridine pro-drug PN401 decreases neurodegeneration, behavioral impairment, weight loss and mortality in the 3-nitropropionic acid mitochondrial toxin model of Huntington's disease.

Huntingtons disease (HD) is associated with decreased activity of mitochondrial succinate dehydrogenase (complex II). De novo biosynthesis of uridine nucleotides is directly coupled to the respiratory chain. Cells with impaired mitochondrial function become uridine auxotrophs and can be maintained with high micromolar concentration of uridine and pyruvate. The therapeutic role of pyrimidines and possible changes in uridine content has not been assessed in neurological diseases involving mitochondrial dysfunction in vivo. Oral administration of PN401 delivers much higher levels of uridine to the circulation than oral administration of uridine itself. Administration of complex II inhibitor 3-nitropropionic acid (3NP) induced neuronal damage in the striatum, substantia nigra and/or thalamus in 80% of the mice and led to 38% mortality. Treatment with PN401 almost completely prevented the neuronal damage due to 3NP and completely prevented mortality. In two subsequent experiments, 3NP-induced weight loss, mortality and behavioral impairment in rotarod performance and spontaneous motor activity were attenuated by treatment with oral PN401. 3NP did not reduce forebrain total uridine nucleotides (TUN), though higher doses of PN401 associated with optimal neuroprotection did elevate TUN to supranormal levels. Thus, oral PN401 treatment has neuroprotective effects in a HD model of mitochondrial dysfunction and the mechanism is more complex than correction of a pyrimidine deficit.

Neuroprotective effects of oral administration of triacetyluridine against MPTP neurotoxicity

Administration of triacetyluridine (TAU) is a means of delivering exogenous pyrimidines to the brain, which may help to compensate for bioenergetic defects. TAU has previously been shown to be neuroprotective in animal models of Huntington’s and Alzheimer’s diseases. We examined whether oral administration of TAU in the diet could exert significant neuroprotective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity model of Parkinson’s disease. Administration of TAU significantly attenuated MPTP-induced depletion of striatal dopamine and loss of tyrosine-hydroxylase-positive neurons in the substantia nigra. These findings suggest that administration of TAU may be a novel approach for treating neurodegenerative diseases associated with impaired mitochondrial function.

Uridine prodrug improves memory in Tg2576 and TAPP mice and reduces pathological factors associated with Alzheimer's disease in related models.

Uridine prodrug PN401 has been shown to have neuroprotective effects in models of Parkinsons disease and Huntingtons disease. These age-related neurodegenerative diseases including Alzheimers disease (AD) are associated with mitochondrial dysfunction, oxidative stress, and inflammation. Attenuation of these pathological factors in AD, in addition to amyloid fibrils and neurofibrillary tangles, is critical to prevent cognitive impairment. The effects of PN401 treatment were tested in the Tg2576 and Tg2576 X P301L (TAPP) mouse models of AD. Treatment with PN401 reduced impairments in the Tg2576 mice in contextual fear conditioning and novel object recognition. In the TAPP mice, PN401 reduced the impairments in novel object recognition and social transmission of food preference. PN401 also improved motor behavior and reduced anxiety-like behavior in the TAPP mice. TAPP mouse hippocampal tau phosphorylation and lipid peroxidation were reduced by PN401 treatment. Increased tau phosphorylation was significantly correlated with worsening novel object recognition memory. PN401 did not affect amyloid plaque area in the AD mice. In other AD-related animal studies, PN401 treatment reduced blood-brain barrier damage due to intracortical LPS, elevation of serum TNFα due to systemic LPS, and hippocampal CA1 neuronal loss in the gerbil stroke model. Uridine dose-dependently protected cells from chemical hypoxia and ceramide, and decreased formation of reactive oxygen species and mitochondrial DNA damage due to hydrogen peroxide. These protective effects were achieved by raising uridine levels to at least 25-50 μM and serum uridine levels in this range in humans were obtained with oral PN401.

PN401 decreases neurodegeneration in models of Alzheimer’s, Huntington’s and Parkinson’s disease, neuroinflammation, excitotoxicity and has antiepileptic activity

based on an extensive preclinical literature which shows that AL-108 has potent neuroprotective, memory enhancing and neurotrophic properties. Furthermore, the data from these studies provide insights into a proposed mechanism of action of AL-108 against two primary pathologies of AD beta amyloid toxicity and microtubule breakdown that is associated with tau hyperphosphorylation. Objectives: To evaluate AL-108 in preclinical and toxicological studies toward clinical trials in Alzheimer’s disease patients. Methods and Results: Neuroprotective activities of AL-108 have been investigated in vitro against: The AD toxin ( amyloid peptide); The toxic envelope protein of the human immunodeficiency virus (HIV; gp120); Glucose deprivation; Electrical blockade (tetrodotoxin); Oxidative stress (hydrogen peroxide and glutathione); Dopamine toxicity and excitotoxicity (N-methyl-D-aspartate). AL-108 has also been evaluated as a potential neuroprotectant in a variety of animal models related to AD: The rat cholinotoxicity model; Apolipoprotein E-deficient mice; Mouse head trauma model; Hypertensive rat stroke model. AL-108 is an eight amino acid peptide with the following characteristics: It has a lipophilic structure that allows penetration through lipid membranes as in the case of the cellular membrane and the blood brain barrier; It has intrinsic sheet breaker characteristics, thus acting as a peptide chaperone to protect against toxic A plaque associated with AD; It chelates trace amounts of heavy metals, thus preventing toxicity; It binds to tubulin and promotes proper microtubule assembly as a peptide chaperone. In conclusion, based on the preclinical results toxicology studies have been peroformed. Good Laboratory Practice (GLP) animal studies have demonstrated that AL-108 is safely tolerated, brain bioavailable by intranasal, intravenous and subcutaneous routes and suitable for drug development. Allon Therapeutics has filed an Investigational New Drug application with the United States Food and Drug Administration for AL-108 and has received FDA approval to proceed.

Prompt treatment with uridine triacetate improves survival and reduces toxicity due to fluorouracil and capecitabine overdose or dihydropyrimidine dehydrogenase deficiency

&NA; Uridine triacetate has been shown to be an effective antidote against mortality and toxicity caused by either overdoses or exaggerated susceptibility to the widely used anticancer agents 5‐fluorouracil (5‐FU) and capecitabine. However, a direct assessment of efficacy based on when emergency treatment was initiated was not clinically feasible. In this study we used mouse models of 5‐FU overdose and of dihydropyrimidine dehydrogenase (DPD) deficiency to compare the efficacy of uridine triacetate in reducing toxicity and mortality when treatment was initiated at time points from 4 to 144 h after administration of 5‐FU. We found that uridine triacetate was effective both in the 5‐FU overdose and DPD deficiency models. Starting treatment within 24 h was most effective at reducing toxicity and mortality in both models, while treatment starting more than 96 to 120 h after 5‐FU was far less effective. Uridine triacetate also reduced mortality in the DPD deficiency model when mice were treated with the 5‐FU prodrug capecitabine. The results of this study are supportive of clinical observations and practice, indicating that efficacy declined progressively with later and later treatment initiation. Prompt treatment with uridine triacetate, within 24 h, conferred the greatest protection against 5‐FU overexposure. HighlightsUridine triacetate reduced mortality from 5FU overdose and DPD deficiency.Treatment within 24 h conferred the greatest protection against 5FU overexposure.Delaying uridine triacetate administration led to greater toxicity and mortality.Little benefit was observed when uridine triacetate was given 96–120 h after 5FU.Results support clinical evidence of reduced 5FU/capecitabine mortality and toxicity.