Myeloid derived immune suppressor cells (MDSCs) in the tumor microenvironment of glioblastoma multiforme (GBM) dampen the efficacy of oncologic therapies. What dampens MDSCs? The ubiquitously-prescribed phosphodiesterase-5 inhibitor tadalafil (aka Cialis). A pilot study demonstrates a measurable reduction in peripheral MDSCs and increase in CD8 T-cell proliferation / activation among 16 enrollees receiving daily oral tadalafil at weight-based dosing for two months to commence with definitive chemoradiation for IDH-wildtype GBM. Importantly, this is a drug with an already well-understood (minimal) side effect profile that provides a safe strategy for future prospective evaluations. | Ghosh, Neuro Oncol 2023
