PDXs were selected on the basis of PIK3CA activating mutation (UWSCC-6 and 13) or for intrinsic cetuximab resistance (UWSCC-1, 17, and 64). Mice were treated with daily administration of the dual mTORC inhibitor AZD8055 by oral gavage and bi-weekly dosing of i.p. cetuximab or single agent therapy for comparison for two or three weeks...Overall, we observed a greater benefit of combining mTORC inhibition with anti-EGFR therapy in the in vivo PDX models than we did in cell lines.