Advanced surgically unresectable colorectal patients have limited treatment options. Recent pivotal research enforces the necessity of identification and appropriate application of predictive and prognostic markers (if available) for optimal selection of systemic chemotherapy. Akt is a serine/threonine kinase that promotes cell proliferation and survival and may be abnormally or constitutively activated (overexpression and mutation), altered by PI3K (mutation), and/or loss of PTEN (mutation, loss of heterozygosity, or methylation). Perifosine is an orally bioavailable alkylphospholipid that blocks localization of Akt to the cell membrane and its phosphorylation in-vitro and in-vivo. Striking phase II data of perifosine capecitabine demonstrated a 2- to 3-fold superior time to progression (TTP), response, and overall survival (OS) in metastatic colorectal patients (MCRC). These results are the foundation for a randomized, placebo-controlled, double blinded, phase III trial of capecitabine perifosine (X-PECT) in previously treated MCRC patients. Perifosine is the first putative Akt inhibitor in phase III development. Archived tissue, pre- and on-treatment (before cycle #1 and at cycle #2) blood and tissue correlatives will be obtained.
Specific Aim #1 : To determine whether PI3K pathway aberrations predict response, progression-free survival (PFS) and OS to perifosine. Mutation status of key oncogenes including PIK3CA, PIK3R1, Akt, ras, and raf, will be evaluated through Sequenom mutation analysis on formalin-fixed paraffin embedded (FFPE) archival tissue. Loss of PTEN will be assessed by immunohistochemistry (IHC). Hypothesis: We hypothesize that patients having tumor aberrations activating PI3K signaling (PIK3CA, PTEN mutations, and PTEN loss by IHC) will derive significant benefit from perifosine. Endpoint: Identification of pretreatment biomarkers that correlate with efficacy of perifosine therapy.
Specific Aim #2 : To determine whether perifosine inhibits Akt signaling in metastatic tumors and determine whether this correlates with its anti-tumor effect. 1. To assess effect of perifosine on PI3K pathway signaling, apoptosis, and proliferation by IHC. 2. To determine effect of perifosine on PI3K pathway signaling utilizing reverse phase protein array (RPPA) a high-throughput, functional proteomic technique. RPPA will be used for detection of baseline cell signaling, expression of putative drug resistance markers, and alterations in the functional proteome. 3. To correlate changes in pharmacodynamic expression in pre- and on-treatment peripheral blood mononuclear cell's (PBMC's) and platelet-rich plasma (PRP) with tumor tissue. Hypothesis: We hypothesize that perifosine treatment will result in inhibition of phosphorylated Akt (p-Akt) and downstream signaling thereby inhibiting cell proliferation and enhancing apoptosis. Endpoint: Pharma- codynamic biomarker changes will correlate with efficacy of perifosine therapy.
Perifosine is an orally bioavailable alkylphospholipid that is the only putative Akt inhibitor in phase III development for the treatment of metastatic colorectal cancer patients. Results from a randomized phase II trial of perifosine in combination with capecitabine were overwhelmingly positive for time to progression and overall survival in heavily pretreated metastatic colorectal cancer patients. However, the exact mechanism of how perifosine impacts the PI3K/PTEN/AKT/mTOR signal transduction pathway is not well understood;molecular marker analysis of archival tissue, as well as pre- and on-treatment tissue and blood specimens for predictive biomarker identification in the phase III (X-PECT) trial will provide fundamental knowledge about perifosine but also other PI3K/AKT inhibitors in development for the treatment of metastatic colorectal cancer and other malignancies.
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