Tadalafil to Overcome Immunosuppression During Chemoradiotherapy for IDH-wildtype Grade III-IV Astrocytoma

Increasing preclinical and clinical data have shown that myeloid-derived suppressor cells (MDSCs) may represent a significant driver of immunosuppression in glioblastoma (GBM, grade IV astrocytoma) and a potential mechanism of treatment resistance to chemoradiotherapy. Tadalafil, an FDA-approved drug with inexpensive cost and excellent safety profile, has been shown to effectively reduce MDSCs and restore T-cell activation in the peripheral blood and in the tumor microenvironment. The purpose of this study is to investigate the impact of targeting MDSCs in newly diagnosed IDH-wildtype grade III-IV astrocytoma by combining tadalafil with standard of care radiation therapy (RT) and temozolomide (TMZ).