PROJECT SUMMARY Glioblastoma (GBM) is among the most common and malignant tumor in the central nervous system with an extremely poor prognosis. New treatments for this disease are desperately needed and the protease ATG4B is a new potential target to reduce GBM tumorgenicity and prolong patient life. Based on strong preliminary results, we propose to create new ATG4B inhibitors through a collaborative and iterative process. Our collaborative workflow involves a) optimization of a commercial compound (NSC185058) with poor potency and drug like characteristics guided by in vitro potency and selectivity, b) evaluation of blood brain barrier and metabolic performance, and lastly, c) in vivo efficacy investigations combining our best candidates with radiotherapy and temozolomide. This high risk, high reward project will add validation to ATG4B as a prime target for GBM treatment and provide new Northwestern-based drug compounds to combat this dreaded disease.