Pharmacodynamic Markers of Perifosine Efficacy

Abstract

Purpose: It is critical to develop methods to quantify the early pharmacodynamic effects of targeted therapeutics in vivo to make drug development more efficient and ensure biologically relevant dosing. Furthermore, an ability to identify patients likely to respond to targeted therapeutics would decrease the size, duration, and cost of clinical trials, resulting in more efficient translation to improved patient outcomes. Recent studies suggest that perifosine inhibits the phosphatidylinositol-3 ¶-kinase (PI3K) pathway by preventing cell membrane recruitment of the AKT pleckstrin homology domain. Experimental Design: A novel functional proteomics technology, reverse phase protein array, was used to establish and quantify pharmacodynamic markers of perifosine efficacy. Results: Perifosine selectively prevents AKTrecruitment to the membrane and blocks activation of downstream effectors. Perifosine inhibited breast, ovarian, and prostate cancer models. Growth inhibition was associated with apoptosis. Activation of AKT as a consequence of genomic aberrations predicted perifosine efficacy. In cell lines and xenografts, there was a highly statistically significant correlation between the degree of antitumor efficacy of different perifosine doses and quantified down-regulation of phosphorylation of AKT and of its downstream targets, particularly S6. Conclusions: Because of a strong correlation between proportional modulation of PI3K pathway biomarkers and quantified perifosine efficacy, it is likely that early measurement of such pharmacodynamic biomarkers with reverse phase protein array will optimize selection of responding patients and guide perifosine dosing. Furthermore, PI3K pathway activation status may allow baseline selection of patients most likely to respond to perifosine alone or in combination with other therapies.Perifosine is a novel ether alkylphospholipid demonstrating antitumor activity in human trials (1). Perifosine inhibits tumor growth through multiple mechanisms; however, recent studies suggest that perifosine inhibits the phosphatidylinositol-3 ¶-kinase (PI3K)/AKT pathway by preventing cell membrane recruitment of the AKT pleckstrin homology (PH) domain (2). Many effects of perifosine can be bypassed by enforced membrane AKT targeting, further implicating AKT inhibition in its activity. The PI3K/AKT pathway is activated more frequently by genomic anomalies than other signaling pathways in cancer, making it a potentially exciting therapeutic target (3 -7). Other than rapamycin and its analogues, perifosine is the only PI3K/ AKT inhibitor in clinical trials, making methods to (a) determine if perifosine inhibits PI3K/AKT signaling, (b) if patients receive a biologically relevant dose, and (c) select likely responders crucial.The PI3K/AKT pathway regulates many ''hallmarks of cancer,'' including survival, proliferation, and metastasis (3). PDK1, TSC2, glycogen synthase kinase 3 (GSK3), mTOR, p70S6 kinase, and S6 mediate many effects of PI3K/AKT and participate in feedback loops that regulat...

Drug discovery approaches targeting the PI3K/Akt pathway in cancer

“…Blocking simultaneously distinct components of the PI3K/Akt pathway seems to enhance the inhibition of phosphorylation of Akt along with activation of the apoptotic pathway. Recently, it has been shown a statistically significant correlation between the antitumor efficacy of perifosine and quantified downregulation of p-Akt and p-S6 (Hennessy et al, 2007). Moreover, results obtained from a study of perifosine in MT-1 human breast xenograft suggests that immunomodulation may partly contribute to the anticancer activity of this compound (Safa et al, 1998).…”

Integrin-linked kinase has a critical role in ErbB2 mammary tumor progression: implications for human breast cancer

“…To accomplish this, we used both reverse-phase protein analyses and immunoblot analyses with phosphospecific antibodies directed at these key downstream signaling molecules (Hennessy et al, 2007). The results revealed that the rare ILK-deficient tumors that arise did not show a significant decrease in signaling through any of these core signaling pathways (Supplementary Figure S3 and S4).…”

“…Reverse-phase protein lysate microarray Reverse-phase protein microarray was performed as described previously and used to evaluate the expression and the phosphorylation of 40 distinct proteins (Tibes et al, 2006;Hennessy et al, 2007).…”

Induction of death receptor 5 expression in tumor vasculature by perifosine restores the vascular disruption activity of TRAIL-expressing CD34+ cells

“…is an oral Akt inhibitor that is being tested in phase I/II clinical trials [7][8][9][10][11]; this drug is a synthetic alkylphospholipid (APL) that targets the pleckstrin homology domain of Akt, thereby preventing its translocation to the plasma membrane [12][13][14][15]. Recent reports have shown that the in vitro sensitivity of cancer cell lines to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) can be considerably increased by cotreatment with perifosine due to significant upregulation of death receptors 4/5 (DR4/5) expression as well as downregulation of the antiapoptotic protein cFLIP [16][17][18].…”