PHT-427 can inhibit both Akt and PDPK1 with Ki values of 2.7 uM and 5.2 uM. PHT-427 itself (C-12 chain) bound with the highest affinity to the PH domains of both PDPK1 and Akt. PHT-427 inhibited Akt and PDKP1 signaling and their downstream targets in sensitive but not resistant cells and tumor xenografts. The PDPK1-independent phospho-Ser473-Akt was slightly increased by PHT-427, but completely inhibited in by wortmannin. Phospho-Ser657-protein kinase C (PKC) and total SGK1 are decreased by treatment with both PHT-427 and wortmannin. In the BxPC-3 cells which is sensitive to the antitumor activity of PHT-427, shows a decrease of both phospho-Ser473-Akt and phospho-Thr308-Akt.
In vivo
PHT-427 shows great antitumor activity. At doses of 125 to 250 mg/kg, PHT-427 gave up to an 80% inhibition of tumor growth in the most sensitive tumors.PHT-427 administered orally to mice with subcutaneous MCF-7 human breast cancer xenografts shows antitumor that was additive with that of paclitaxel. PHT-427 administered orally for 10 days to mice with orthotopic NCI-H441 NSC lung cancer xenografts increased the antitumor activity of continuous daily erlotinib which by itself had no antitumor activity in this model.