We have previously described a novel series of low molecular weight protein tyrosine kinase inhibitors which we named tyrphostins. The characteristic active pharmacophore of these compounds was the hydroxy-cis-benzylidenemalononitrile moiety. In this article we describe three novel groups of tyrphostins: (i) one group has the phenolic moiety of the cis-benzylidenemalononitrile replaced either with other substituted benzenes or with heteroaromatic rings, (ii) another is a series of conformationally constrained derivatives of hydroxy-cis-benzylidenemalononitriles in which the malononitrile moiety is fixed relative to the aromatic ring, and (iii) two groups of compounds in which the position trans to the benzenemalononitrile has been substituted by ketones and amides. Among the novel tyrphostins examined we found inhibitors which discriminate between the highly homologous EGF receptor kinase (HER1) and ErbB2/neu kinase (HER2). These findings may lead to selective tyrosine kinase blockers for the treatment of diseases in which ErbB2/neu is involved.

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...

Perifosine-bortezomib ± dexamethasone demonstrated encouraging activity in heavily pretreated bortezomib-exposed patients with advanced MM. A phase III trial is underway comparing perifosine-bortezomib plus dexamethasone with bortezomib-dexamethasone in patients with relapsed/refractory MM previously treated with bortezomib.