Project Summary/Abstract Glioblastoma (GBM) is the most common and lethal primary brain tumor with the median survival of 9.7 months. The current standard of care treatment involves a combination of surgery, chemotherapy and radiation but only improve the median survival up to 14 months. Challenges in discovery of therapeutics for GBM include identifying drug targets and discovering therapeutics that are blood brain barrier (BBB) permeable. To meet the challenges, we have identified small ubiquitin-related modifier 1 (SUMO1) as an oncoprotein that drives the self-renewal and tumorigenesis of GBM stem cells. We have designed GBM cell-based SUMO1 assay, screened the compounds library provided by the National Cancer Institute, and identified the hit compound as the first small molecule degrader that induces SUMO1 ubiquitination and degradation in GBM cells. Structure-activity relationship (SAR) studies around the hit-derived analogs have generated three scaffolds of lead compounds with improved potency and an excellent BBB permeability. Using GBM stem cell-enriched neurospheres and derived xenografts, we have shown that the lead compounds are more effective in treatment of GBM than the standard chemotherapy temozolomide (TMZ). In this R01 project, we will optimize our lead series with the aim of identifying more potent, orally bioavailable and BBB-permeable SUMO1 degraders that will have the preclinical efficacy, safety, and pharmacokinetic properties predicting it be enable full exploration in clinical treatment of GBM. To achieve this objective, we will leverage our computational chemistry technology to assist the design of novel compounds with BBB permeability and drug-like properties through chemical modifications of our lead series in Aim 1. Each of compounds will be rationally designed, synthesized and assessed in our established compound testing funnel for their activity and target selectivity in SUMO1 degradation. Compounds that meet our criteria for success will be selected for in vitro solubility, permeability, absorption, distribution, metabolism, and excretion assessment and prioritized for the anticancer activity against GBM stem cell-enriched neurospheres. In Aim 2, the leading compounds selected from the studies of Aim 1 will be evaluated for their pharmacokinetic properties to determine oral bioavailability and BBB permeability. Selected compounds will be assessed for in vivo target engagement and therapeutic efficacy in treatment of patient derived xenograft GBM models. The optimized lead compounds selected from the studies in Aim 2 will be evaluated for their toxicology, safety pharmacology and oral formulation in Aim 3. The milestone of this project is to select optimized lead compound(s) for advancement into preclinical development phase, investigative new drug-enabling studies and phase I trials in treatment of GMB patients.