Myeloid derived suppressor cells (MDSC) play a significant role in tumor-induced immune suppression. Targeting their function could improve anti-tumor therapies. We previously demonstrated that phosphodiesterase 5 (PDE5) inhibition in MDSCs augmented anti-tumor immunity in murine models. Here we show how the addition of the PDE5 inhibitor, tadalafil, in a patient with end-stage relapsed/refractory multiple myeloma reduced MDSC function and generated a dramatic and durable anti-myeloma immune and clinical response. Strategies targeting MDSC function with PDE5 inhibitors represent a novel approach that can augment the efficacy of tumor-directed therapies.
- Received December 2, 2013.
- Revision received March 20, 2014.
- Accepted March 24, 2014.
- Copyright © 2014, American Association for Cancer Research.