Renfei Du ¹ Ahmed Y. Sanin ² Wenjie Shi ² Bing Huang ³ Ann-Christin Nickel ¹ ANDRES VARGAS-TOSCANO ¹ Shuran Huo ⁴ Thomas Nickl-Jockschat ² Claudia A. Dumitru ² Wei Hu ¹ Siyu Duan ¹ I E. Sandalcioglu ² Roland S. Croner ² Joshua Alcaniz ⁵ Wolfgang Walther ⁵ Carsten Berndt ⁶ Ulf Kahlert ^2*

• ¹ Institute of Systems Neuroscience, Heinrich-Heine University, Düsseldorf, Germany
• ² Otto von Guericke University Magdeburg, Magdeburg, Saxony-Anhalt, Germany
• ³ Goethe University Frankfurt, Frankfurt, Hesse, Germany
• ⁴ Chifeng Cancer Hospital, Inner Mongolia, China
• ⁵ Experimental Pharmacology & Oncology Berlin-Buch GmbH, Berlin, Berlin, Germany
• ⁶ University Hospital of Düsseldorf, Düsseldorf, North Rhine-Westphalia, Germany

Glioblastoma (GBM) is the most commonly occurring and most aggressive primary brain tumor. Transcriptomics-based tumor subtype classification has established the mesenchymal lineage of GBM (MES-GBM) as cancers with particular aggressive behavior and high levels of therapy resistance. Previously it was show that Trihexyphenidyl (THP), a market approved M1 muscarinic receptor-targeting oral drug can suppress proliferation and survival of GBM stem cells from the classical transcriptomic subtype. In a series of in vitro experiments, this study confirms the therapeutic potential of THP, by effectively suppressing the growth, proliferation and survival of MES-GBM cells with limited effects on non-tumor cells. Transcriptomic profiling of treated cancer cells identified genes and associated metabolic signaling pathways as possible underlying molecular mechanisms responsible for THP-induced effects. In vivo trials of THP in immunocompromised mice carry orthotopic MES-GBMs showed moderate response to the drug. This study further highlights the potential of THP repurposing as an anti-cancer treatment regimen but mode of action and d optimal treatment procedures for in vivo regimens need to be investigated further.