Stroke is the leading cause of disability and death in the U.S. Intravenous administration of tPA within 3 hours of symptom onset remains the only FDA-approved pharmacotherapy. Novel approaches to improving the treatment of stroke are in high demand. We recently discovered that the SUR1-TRPM4 channel is upregulated de novo in all cell types of the neurovascular unit following ischemia and channel blockade using glyburide achieved robust, clinically-relevant beneficial effects in multiple preclinical models. This finding has led to a phase II GAMES-RP trial. Clinical results revealed a trend toward improved survival and a significant reduction in edema but failed to meet the primary endpoint. The degree of swelling reduction was insufficient to prevent decompressive craniectomy or significantly increase clinical outcome. Further analysis showed that the unmet efficacy is due to the limitations associated with the current formulation. First, glyburide in the current formulation has limited penetration into the ischemic brain and thus does not allow fully capitalizing its anti- edema and neuron protective actives. Second, the current formulation does not accommodate the requirement for prompt drug administration. To overcome these limitations, we propose to develop a novel nanoformulation, acid responsive, stroke- targeting, antioxidant nanoparticles (ARSTA NPs), to enhance the delivery and efficacy of glyburide. As preliminary work, we developed an innovative approach for isolating natural nanomaterials from medicinal natural products (MNPs), and identified betulinic acid (BA) that forms NPs. We showed that BA NPs penetrated the ischemic brain, effectively reduced brain infarction through regulation of the antioxidant and pro-inflammatory pathways, and mediated efficient delivery of glyburide to the brain. We demonstrated that the ischemic microenvironment is acidic. We developed chemistry to convert BA to betulinic amine (BAM) and showed that BAM NPs released glyburide in a rate significantly greater than BA NPs in acidic pH. We screened a collection of MNPs and identified three new nanomaterials that have anti-stroke activity and drug delivery capacity comparable to BA. We demonstrated that targeted delivery of NPs to the ischemic brain can be achieved through surface conjugation of AMD3100. We developed a PET imaging approach for non-invasive monitoring stroke recovery by measuring synapse density. Building on these progress, we propose to synthesize and characterization of ARSTA NPs for targeted delivery of glyburide to the ischemic brain in Aim 1, and to evaluate glyburide-loaded ARSTA NPs for treating ischemic stroke and the PET imaging approach for non-invasively monitoring post-stroke functional recovery in Aim 2. The success of this project will result in a new paradigm for treating ischemic stroke and for non-invasively monitoring post- stroke functional recovery, which can be translated into clinical applications to improve clinical management of patients with the disease.

Relevance to public health: Stroke is the leading cause of disability and death in the United States, with approximately 795,000 ischemic stroke victims annually. Malignant infarction, characterized by significant brain swelling, has no available preventative medical therapy and results in very high rates of mortality and morbidity. This research project will result in a new approach to improving the treatment of patients with this disease.