Indolinone based phosphoinositide-dependent kinase-1 (PDK1) inhibitors. Part 2: Optimization of BX-517

Islam, Imadul; Brown, Greg; Bryant, Judi; Hrvatin, Paul; Kochanny, Monica J.; Phillips, Gary B.; Shuanggui, Yuan; Adler, Marc; Whitlow, Marc; Lentz, Dao; Polokoff, Mark A.; Wu, James M.; Shen, Jun; Walters, Janette; Ho, Elena; Subramanyam, Babu; Zhu, Daguang; Feldman, Richard I.; Arnaiz, Damian O.

doi:10.1016/j.bmcl.2007.05.060

Cited by 40 publications

(38 citation statements)

References 13 publications

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“…This compound has potent activity against many other anti-cancer drug targets, including Aura A and TBK1 (61), and shows antiproliferative effects in PDK1 knock-out (PDK1 Ϫ/Ϫ ) cells (13). Along these lines, derivatives of BX-795 optimized for selectivity possess 10 -100-fold higher activity in soft agar growth assays compared with their poor activity under standard tissue culture conditions (70). Notably, PDK1 Ϫ/Ϫ ES cells grow similarly to their wild-type counterparts under standard cell culture conditions, consistent with our observation that the PDK1 enzyme is not rate-limiting for in vitro cell growth of cancer cell lines (13).…”

Section: Discussionmentioning

confidence: 99%

Genetic and Pharmacological Inhibition of PDK1 in Cancer Cells

Nagashima

Shumway

Sathyanarayanan

et al. 2011

Journal of Biological Chemistry

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Phosphoinositide-dependent kinase 1 (PDK1) is a critical activator of multiple prosurvival and oncogenic protein kinases and has garnered considerable interest as an oncology drug target. Despite progress characterizing PDK1 as a therapeutic target, pharmacological support is lacking due to the prevalence of nonspecific inhibitors. Here, we benchmark literature and newly developed inhibitors and conduct parallel genetic and pharmacological queries into PDK1 function in cancer cells. Through kinase selectivity profiling and x-ray crystallographic studies, we identify an exquisitely selective PDK1 inhibitor (compound 7) that uniquely binds to the inactive kinase conformation (DFG-out). In contrast to compounds 1-5, which are classical ATP-competitive kinase inhibitors (DFG-in), compound 7 specifically inhibits cellular PDK1 T-loop phosphorylation (Ser-241), supporting its unique binding mode. Interfering with PDK1 activity has minimal antiproliferative effect on cells growing as plastic-attached monolayer cultures (i.e. standard tissue culture conditions) despite reduced phosphorylation of AKT, RSK, and S6RP. However, selective PDK1 inhibition impairs anchorage-independent growth, invasion, and cancer cell migration. Compound 7 inhibits colony formation in a subset of cancer cell lines (four of 10) and primary xenograft tumor lines (nine of 57). RNAi-mediated knockdown corroborates the PDK1 dependence in cell lines and identifies candidate biomarkers of drug response. In summary, our profiling studies define a uniquely selective and cell-potent PDK1 inhibitor, and the convergence of genetic and pharmacological phenotypes supports a role of PDK1 in tumorigenesis in the context of three-dimensional in vitro culture systems.PDK1 (phosphoinositide-dependent kinase-1) was first identified as a protein serine/threonine kinase that linked phosphatidylinositol 3-kinase (PI3K) to AKT (protein kinase B) activation in response to growth factor receptor signaling (1, 2). Growth factor binding to receptor tyrosine kinases (RTKs) 3 results in activated PI3K, which phosphorylates the 3Ј-position of the inositol ring in phosphatidylinositol 4,5-bisphosphate to produce the second messenger phosphatidylinositol 3,4,5-trisphosphate (3). Membrane-bound phosphatidylinositol 3,4,5-trisphosphate recruits AKT to the plasma membrane, where it co-localizes with PDK1 in a pleckstrin homology domain-dependent manner (4 -6). The binding of phosphatidylinositol 3,4,5-trisphosphate to AKT induces a conformational shift that alleviates AKT autoinhibition (7) and allows for PDK1-mediated phosphorylation of AKT Thr-308, an event that is absent in both PDK1 null mouse embryonic stem (ES) cells (8) and tissue-specific PDK1 knock-out mice (9). In parallel with the elucidation of the above PI3K/ PDK1/AKT signaling cascade, PDK1 has been shown to phosphorylate the conserved threonine/serine residue in the activation loop (T-loop) of about 20 related protein kinases (10). Because this phosphorylation event is a prerequisite for full catalytic activity...

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Section: Discussionmentioning

confidence: 99%

Genetic and Pharmacological Inhibition of PDK1 in Cancer Cells

Nagashima

Shumway

Sathyanarayanan

et al. 2011

Journal of Biological Chemistry

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“…The binding of the compound was confirmed by the solving of the X-ray structure with PDK1. Additional medicinal chemistry activities provided PDK1 inhibitors with improved pharmacological properties (Islam et al, 2007a).…”

Section: Inhibitors Of the Ser/thr Kinase Activity Of Pdk1mentioning

confidence: 99%

Drug discovery approaches targeting the PI3K/Akt pathway in cancer

2008

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“…Feldman et al 5 and Islam et al 6 have described a series of potent indolinone-based PDK1 inhibitors (BX-795, BX-320, and BX-517 with 6-to 30-nM potency). They have demonstrated that these compounds block Akt signaling in cancer cells, cause cell cycle arrest and/or apoptosis, and inhibit transformationdependent growth.…”

mentioning

confidence: 99%

Development of High-Throughput TR-FRET and AlphaScreen® Assays for Identification of Potent Inhibitors of PDK1

Nagashima

Sun

et al. 2009

SLAS Discovery

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The PI3K/Akt signaling pathway plays a key role in cancer cell growth, survival, and tumor angiogenesis. 3-Phosphoinositidedependent protein kinase 1 (PDK1) is a Ser/Thr protein kinase, which catalyzes the phosphorylation of a conserved residue in the activation loop of a number of AGC kinases, including proto-oncogenes Akt, p70S6K, and RSK kinases. To find new small-molecule inhibitors of this important regulator kinase, the authors have developed PDK1-specific high-throughput enzymatic assays in time-resolved fluorescence resonance energy transfer (TR-FRET) and AlphaScreen ® formats, monitoring phosphorylation of a biotinylated peptide substrate derived from the activation loop of Akt. Development of homogeneous assays enabled screening of a focused kinase library of ~21,500 compounds in 1536-well TR-FRET format in duplicate. Upon validation of hits in an alternative 384-well AlphaScreen ® assay, several classes of structurally diverse PDK1 inhibitors, including tetracyclics, tricyclics, azaindoles, indazoles, and indenylpyrazoles, were identified, thus confirming the utility and sensitivity of the developed assays. Further testing in PC3 prostate cancer cells confirmed that representatives of the tetracyclic series showed intracellular modulation of the PDK1 activity, as evident from decreased phosphorylation levels of AKT, RSK, and S6-ribosomal protein. (Journal of Biomolecular

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Indolinone based phosphoinositide-dependent kinase-1 (PDK1) inhibitors. Part 2: Optimization of BX-517

Cited by 40 publications

References 13 publications

Genetic and Pharmacological Inhibition of PDK1 in Cancer Cells

Genetic and Pharmacological Inhibition of PDK1 in Cancer Cells

Drug discovery approaches targeting the PI3K/Akt pathway in cancer

Development of High-Throughput TR-FRET and AlphaScreen® Assays for Identification of Potent Inhibitors of PDK1

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