Molecular Pharmacology and Antitumor Activity of PHT-427, a Novel Akt/Phosphatidylinositide-Dependent Protein Kinase 1 Pleckstrin Homology Domain Inhibitor

Abstract

Phosphatidylinositol 3-kinase/phosphatidylinositide-dependent protein kinase 1 (PDPK1)/Akt signaling plays a critical role in activating proliferation and survival pathways within cancer cells. We report the molecular pharmacology and antitumor activity of PHT-427, a compound designed to bind to the pleckstrin homology (PH) binding domain of signaling molecules important in cancer. Although originally designed to bind the PH domain of Akt, we now report that PHT-427 also binds to the PH domain of PDPK1. A series of PHT-427 analogues with variable C-4 to C-16 alkyl chain length were synthesized and tested. 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 PDPK1 signaling and their downstream targets in sensitive but not resistant cells and tumor xenografts. When given orally, PHT-427 inhibited the growth of human tumor xenografts in immunodeficient mice, with up to 80% inhibition in the most sensitive tumors, and showed greater activity than analogues with C4, C6, or C8 alkyl chains. Inhibition of PDPK1 was more closely correlated to antitumor activity than Akt inhibition. Tumors with PIK3CA mutation were the most sensitive, and K-Ras mutant tumors were the least sensitive. Combination studies showed that PHT-427 has greater than additive antitumor activity with paclitaxel in breast cancer and with erlotinib in non-small cell lung cancer. When given >5 days, PHT-427 caused no weight loss or change in blood chemistry. Thus, we report a novel PH domain binding inhibitor of PDPK1/Akt signaling with significant in vivo antitumor activity and minimal toxicity. Mol Cancer Ther; 9(3); 706-17. ©2010 AACR.

AMIGO2, a novel membrane anchor of PDK1, controls cell survival and angiogenesis via Akt activation

“…Moreover, the disruption of the PH domain in PDK1 knockin embryoid bodies resulted in impairment of Akt activation, vessel formation, and EC migration (Primo et al, 2007;Bayascas et al, 2008). Likewise, depletion of AMI GO2 using siRNA resulted in inhibition of PDK1 localization to the plasma membrane as well as activation and caused defective EC survival, It is well established that the PI3K-mediated PDK1-Akt signaling pathway plays a crucial role in regulating tumorigenesis and angiogenesis through VEGF and several other growth factors (Jiang and Liu, 2008;Meuillet et al, 2010). The ablation of Akt interfered with mammary tumor growth in MMTVPyMT and MMTV-ErbB2/Neu transgenic mice (Maroulakou et al, 2007).…”

Nanoparticle delivery of an AKT/PDK1 inhibitor improves the therapeutic effect in pancreatic cancer

“…We have previously shown that PH-427 is highly efficient in treating a BxPC3 xenograft model that has wild-type K-ras, but is poorly Dovepress Dovepress 5654 lucero-acuña et al efficient in a MiaPaCa-2 subcutaneous xenograft model with mutant K-ras. 12,13 These previous results suggest that PCAs with mutant K-ras require a higher dose or longer drug exposure to PH-427 to overcome the protective stromal layer surrounding the pancreatic tumor. Therefore, methods that improve drug delivery or retention may potentially improve treatment of PCA with mutant K-ras.…”

“…We have developed PH-427 as a novel inhibitor of AKT/PDK1 12,13 that is activated in PCA. 14,15 When PH-427 prevents activation of AKT at the plasma membrane, AKT cannot initiate an important cell survival signaling pathway, leading to death of pancreatic tumor cells.…”

The Akt signaling pathway

“…107 Intraperitoneal administration of PHT-427 blocked the growth of xenografted pancreatic tumors ( Table 2). 108 Recently, analogs of PHT-427 with increasing carbon chain length (from C-4 to C-16) have been synthesized and antitumor activity evaluated. 108 The C-12 analog was found to exhibit potent Akt and PDPK1 (phosphoinositide-dependent protein kinase-1) inhibitory activity compared with other derivatives.…”

“…108 The C-12 analog was found to exhibit potent Akt and PDPK1 (phosphoinositide-dependent protein kinase-1) inhibitory activity compared with other derivatives. 108 API-1. API-1 (NSC-177223) is a pyrido [2,3-d]pyrimidine structurally related to antibiotic sangivamycin ( Table 2).…”