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).
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Relative change of MDSCs in peripheral blood
Timeframe: Baseline, week 6 of RT, before the start of adjuvant TMZ (approximately 4-6 weeks after the end of RT), before the 3rd cycle of adjuvant TMZ (or approximately 3 months after the end of RT if no planned 3rd cycle of adjuvant TMZ), time of progression
Frequency of adverse events as measured by CTCAE v5.0
Timeframe: Baseline through 30 days after last dose of tadalafil (estimated to be 90 days)