KRAS and colorectal neoplasm: This improved activity is consistent with the results presented here as the combination of 100 mg/kg GDC-0941 and 1 mg/kg PD 0325901 was non-toxic, and caused tumour stasis and marked tumour growth delay in the KRAS and PIK3CA mutant HCT116 and the BRAF and PIK3CA mutant HT29 colorectal tumour xenografts, respectively, an effect that was significantly greater than either single agent at the same dose (p≤0.01).