PIK3CB and neoplasm: Preclinical murine and in vitro studies have demonstrated efficacy of PI3K/mTOR dual inhibitors in reducing pathway activation, decreasing tumor progression, and increasing survival times.30, 31, 32 The purpose of the present study is to evaluate the efficacy of VDC597, a dual PI3K/mTOR inhibitor (Supplemental Figs. 1 and 2), for the treatment of canine OS, alone and in combination with cytotoxic chemotherapy drugs.