Harmaline as novel mitochondrial human ClpP activator for the treatment of pediatric DIPG

Diffuse intrinsic pontine glioma (DIPG) is a rare aggressive brainstem tumor and the leading cause of pediatric cancer-related death, with over 90% of young patients dying within two years of diagnosis. Due to its neuroanatomical location and infiltrative nature, DIPG remains incurable underscoring the urgent need for effective therapies. The DIPG standard of care treatment is the focal noncurative radiation therapy, which provides only a transient stabilization of symptoms1. Recent discoveries led to identify ONC201, which acts as dopamine D2 receptor (DRD2) antagonist, and currently in phase III clinical trials for children and adults with low- and high-grade gliomas, including DIPG. In 2019, the biological target of ONC201 was found to be the human mitochondrial caseinolytic protease P (hClpP). Through single crystal X-rays analysis was ascertained that ONC201 allosterically activates ClpP2. In this context, a wide program aimed at identifying scaffolds to drug repositioning was started to find out new hClpP activity inducers that could overcome ONC201 pharmacokinetic and pharmacodynamic drawbacks. Structure Based Virtual Screening study by Fingerprints for Ligands and Proteins (FLAP) identified harmaline, a natural β -carboline alkaloid with emerging anti-tumor properties. Extensive in vitro biopharmaceutical characterization oh harmaline as hClpP activator potentially useful in DIPG treatment will be presented.