NINDS CREATE DISCOVERY: Development of dendrimer-N-acetylcysteine for the treatment of neonatal brain injury

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Project Summary Cerebral palsy is one of the common chronic childhood neurological disorders and has no effective cure. Half a million children under the age of 18 in the US have CP, and 1 in 6 children have some form of developmental disability. Perinatal hypoxic-ischemic encephalopathy (HIE) and maternal-fetal inflammation/immune dysregulation are major causes of cerebral palsy and related disabilities. Although the collective evidence from at least 6-large clinical trials confirms that therapeutic hypothermia improves outcome, 40%-50% of infants treated with hypothermia still die or suffer significant neurologic disability. There remains a critical need for development of therapies for patients who do not qualify for hypothermia, and for adjunct therapies with hypothermia that improve neuroprotection and address the negative effects of hypothermia and rewarming. This is the goal of this 3½ year NINDS CREATE DISCOVERY project. Recent studies suggest that attenuating neuroinflammation, mediated by activated glia, in the early stages can not only delay the onset, but may also provide a longer therapeutic window for treatment. However, delivering drugs across the blood-brain-barrier to target and treat diffuse neuroinflammation is a major challenge. Our team discovered that systemically-administered hydroxyl-terminated poly(amidoamine) (PAMAM) dendrimers (~4 nm) target activated glia in the injured brain, without the need for targeting ligands. Interestingly, intravenous administration of the anti-inflammatory drug N-acetyl cysteine (NAC) conjugated to the dendrimer (D-NAC), in clinically-relevant preclinical models of CP, resulted in striking neuroprotective effects. Building on our strong proof-of concept data using our lead compound D-NAC, we propose to optimize this compound further for use in perinatal/neonatal brain injury, during the discovery phase of the CREATE application, for progressing towards an eventual developmental phase and clinical trials. Three aims are identified, along with appropriate milestones: (1) Optimize the synthesis of D-NAC for scale up production, and demonstrate reproducibility, purity and storage stability. (2) Determine pharmacokinetics, PK-PD relationship, minimal effective dose, optimal dose and elimination of D-NAC in rabbit model of cerebral palsy. (3) Determine long term efficacy of D-NAC at the optimal dose identified in Aim 2, in rabbit model of maternal inflammation induced CP and in term mouse hypoxic-ischemia model with hypothermia.