Methods are provided for treating mesothelioma patients with a dual PI3K/mTOR inhibitor, GDC-0980: (S)-1-(4-((2-(2-aminopyrimidin-5-yl)-7-methyl-4-morpholinothieno[3,2-d]pyrimidin-6-yl)methyl)piperazin-1-yl)-2-hydroxypropan-1-one, and having the structure: