BEZ235 (PI3K/mTOR pathway inhibitor) causes significant cell death [29–31], but low concentrations of the drug in the target tissue results in poor therapeutic efficacy and need for more frequent dosing; on the other hand, high drug concentrations may cause toxicity, including stomatitis, hyperglycemia, non-infectious pneumonia, and immunosuppression. Here, MTOR is linked to stomatitis.