Sonolisib (PX-866) is a small-molecule inhibitor of the alpha, gamma, and delta isoforms of phosphoinositide 3-kinase (PI3K) with potential antineoplastic activity. Sonolisib inhibits the production of the secondary messenger phosphatidylinositol-3,4,5-trisphosphate (PIP3) and activation of the PI3K/Akt signaling pathway, which may result in inhibition of tumor cell growth and survival in susceptible tumor cell populations. Inhibition of the PI3K pathway with Sonolisib leads to inhibition of cell growth and decreased activation of downstream targets in GBM, both in vitro and in vivo, using U87–tumor-bearing mice, including Akt, S6, and mTOR. Sonolisib was in phase II clinical trials by Oncothyreon for the treatment of glioblastoma multiforme and castration-resistant prostate cancer (CRPC). It was in phase I/II clinical trials for the treatment of malignant melanoma, non-small cell lung cancer and Head and neck cancer. In clinical trials, Sonolisib was well tolerated, with common side effects being diarrhea, nausea, vomiting, and elevated liver enzymes. However, no recent development has been reported.