Introduction: PI3K inhibition

Currently in clinical testing are inhibitors of both Akt and mTOR which have shown significant promise for certain patient sub-populations. However, resistance and toxicity to these molecules is common, hence new targets are continuously being investigated. Upstream of Akt and mTOR is the membrane bound protein PI3K which intercepts signals from extracellular growth factor from transmission into the cytosole and eventually the nucleus. While being an upstream target PI3K is still being investigated for anti-tumor effects (1, 2). PI3K is classified into several classes with class 1 being the focus of the small molecule inhibitors currently in preclinical and clinical testing (3). Class 1 kinases are subdivided into four different proteins containing a common catalytic domain, they are identified as Alpha, Beta, Gamma and Delta (4). BEZ235 PI3K inhibitor is a pan- inhibitor of all the isoforms of PI3K as well as targeting mTOR directly as well. BEZ235 is known as an effective dual inhibitor of many tumor types (5-11).

BEZ235: Properties and Availability

Developed by Novartis the dual inhibitor BEZ235 can be found in the catalogues of several BEZ235 suppliers with BEZ235 prices ranging from $35 up to $475 for a 50 mg vial. BEZ235 solubility in water is typical for this type of molecules with virtually no solubility at the physiological pH of 7.4, slight solubility is seen at pH 1 with gentle warming. For research purposes this molecule should be solubilize in DMSO or dimethyl formamide before preparation of buffered solutions, note should be made that a maximum of 10-20 µM can be prepared in aqueous solutions. BEZ235 stability is an issue in that it is light sensitive and relatively unstable at room temperature when in solution. All DMSO solutions should be stored at -20°C prior to daily use, defrosted stock solutions should not be refrozen but discarded. An expiration date of 2 years is recommended before a repeat of purity testing.

BEZ235: Preclinical investigation

Initial screening identified BEZ6244 against a panel of xenographs and cell lines demonstrating that the dual inhibition of PI3K and mTOR2 prevented cell survival as well as the feedback loop observed with mTOR1 inhibitors via the P706K phosphorylation (12). In purified PI3K isoforms was determined to have a pan-PI3K inhibition with similar BEZ235 IC50 for the alpha, gamma and delta (5.33 ± 2 nM) isoforms but demonstrating less sensitivity for the beta isoforms (IC50 – 75 nM) (5, 6, 13). Further activity against malignant melanoma (14), breast cancer (wild type and mutated) (15, 16), NSCLC (wild type and KRAS mutated) (17, 18) and human glioma’s (11). In addition BEZ235 has been investigated in conjunction with gemcitabine in pancreatic cancer showing an enhanced efficacy (19) and having the ability to overcome resistance in breast cancer to ErbB inhibitors (20). In NSCLC a combination with RAD001 (better known as rapamycin), a MTOR1 inhibitor, demonstrated synergistic activity; closer examination using NMR demonstrated deceases in the vascular structure of the tumor during treatment with this combination (21-25). A combination with the 2nd generation mTOR1 inhibitor temsirolimus demonstrated similar results indicating that the triple inhibition of PI3K and mTOR 1&2 is more effective that single therapy of either molecule (26). In addition, BEZ235 is active in the more common forms of lymphoma such a follicular lymphoma or primary effusion lymphoma representing a novel treatment profile for these diseases. In vitro investigation has demonstrate the potent and wide ranging effects of the BEZ235 inhibitor and clinical investigations have been quickly initiated.

BEZ235: - Clinical status

BEZ235 clinical trials have been launched in response to preclinical work; which has been published in 2010 and 2011. Therefore, these trials are recruiting but no reports or data is currently available. Clinical trials initiated in breast cancer cover the wild type form of tumors and in tumors exhibiting mutated BRaf, KRAS, EGFR- and hormonal receptor positive.

Reference List

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      (2)    Ciraolo E, Morello F, Hirsch E. Present and future of PI3K pathway inhibition in cancer: perspectives and limitations. Curr Med Chem 2011;18:2674-85.

      (3)    McNamara CR, Degterev A. Small-molecule inhibitors of the PI3K signaling network. Future Med Chem 2011;3:549-65.

      (4)    Jia S, Roberts TM, Zhao JJ. Should individual PI3 kinase isoforms be targeted in cancer? Curr Opin Cell Biol 2009;21:199-208.

      (5)    Chapuis N, Tamburini J, Green AS, Vignon C, Bardet V, Neyret A, et al. Dual inhibition of PI3K and mTORC1/2 signaling by NVP-BEZ235 as a new therapeutic strategy for acute myeloid leukemia. Clin Cancer Res 2010;16:5424-35.

      (6)    Fokas E, Im JH, Hill S, Yameen S, Stratford M, Beech J, et al. Dual Inhibition of the PI3K/mTOR Pathway Increases Tumor Radiosensitivity by Normalizing Tumor Vasculature. Cancer Res 2012;72:239-48.

      (7)    Roccaro AM, Sacco A, Husu EN, Pitsillides C, Vesole S, Azab AK, et al. Dual targeting of the PI3K/Akt/mTOR pathway as an antitumor strategy in Waldenstrom macroglobulinemia. Blood 2010;115:559-69.

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      (9)    Martin SK, Fitter S, Bong LF, Drew JJ, Gronthos S, Shepherd PR, et al. NVP-BEZ235, a dual pan class I PI3 kinase and mTOR inhibitor, promotes osteogenic differentiation in human mesenchymal stromal cells. J Bone Miner Res 2010;25:2126-37.

    (10)    Serra V, Markman B, Scaltriti M, Eichhorn PJ, Valero V, Guzman M, et al. NVP-BEZ235, a dual PI3K/mTOR inhibitor, prevents PI3K signaling and inhibits the growth of cancer cells with activating PI3K mutations. Cancer Res 2008;68:8022-30.

    (11)    Liu TJ, Koul D, LaFortune T, Tiao N, Shen RJ, Maira SM, et al. NVP-BEZ235, a novel dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor, elicits multifaceted antitumor activities in human gliomas. Mol Cancer Ther 2009;8:2204-10.

    (12)    Maira SM, Stauffer F, Brueggen J, Furet P, Schnell C, Fritsch C, et al. Identification and characterization of NVP-BEZ235, a new orally available dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor with potent in vivo antitumor activity. Mol Cancer Ther 2008;7:1851-63.

    (13)    Santiskulvong C, Konecny GE, Fekete M, Chen KY, Karam A, Mulholland D, et al. Dual targeting of phosphoinositide 3-kinase and mammalian target of rapamycin using NVP-BEZ235 as a novel therapeutic approach in human ovarian carcinoma. Clin Cancer Res 2011;17:2373-84.

    (14)    Baumann P, Mandl-Weber S, Oduncu F, Schmidmaier R. The novel orally bioavailable inhibitor of phosphoinositol-3-kinase and mammalian target of rapamycin, NVP-BEZ235, inhibits growth and proliferation in multiple myeloma. Exp Cell Res 2009;315:485-97.

    (15)    Crowder RJ, Phommaly C, Tao Y, Hoog J, Luo J, Perou CM, et al. PIK3CA and PIK3CB inhibition produce synthetic lethality when combined with estrogen deprivation in estrogen receptor-positive breast cancer. Cancer Res 2009;69:3955-62.

    (16)    Brachmann SM, Hofmann I, Schnell C, Fritsch C, Wee S, Lane H, et al. Specific apoptosis induction by the dual PI3K/mTor inhibitor NVP-BEZ235 in HER2 amplified and PIK3CA mutant breast cancer cells. Proc Natl Acad Sci U S A 2009;106:22299-304.

    (17)    Herrera VA, Zeindl-Eberhart E, Jung A, Huber RM, Bergner A. The dual PI3K/mTOR inhibitor BEZ235 is effective in lung cancer cell lines. Anticancer Res 2011;31:849-54.

    (18)    Konstantinidou G, Bey EA, Rabellino A, Schuster K, Maira MS, Gazdar AF, et al. Dual phosphoinositide 3-kinase/mammalian target of rapamycin blockade is an effective radiosensitizing strategy for the treatment of non-small cell lung cancer harboring K-RAS mutations. Cancer Res 2009;69:7644-52.

    (19)    Awasthi N, Yen PL, Schwarz MA, Schwarz RE. The efficacy of a novel, dual PI3K/mTOR inhibitor NVP-BEZ235 to enhance chemotherapy and antiangiogenic response in pancreatic cancer. J Cell Biochem 2011.

    (20)    Brunner-Kubath C, Shabbir W, Saferding V, Wagner R, Singer CF, Valent P, et al. The PI3 kinase/mTOR blocker NVP-BEZ235 overrides resistance against irreversible ErbB inhibitors in breast cancer cells. Breast Cancer Res Treat 2011;129:387-400.

    (21)    Schnell CR, Stauffer F, Allegrini PR, O'Reilly T, McSheehy PM, Dartois C, et al. Effects of the dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor NVP-BEZ235 on the tumor vasculature: implications for clinical imaging. Cancer Res 2008;68:6598-607.

    (22)    Breuleux M, Klopfenstein M, Stephan C, Doughty CA, Barys L, Maira SM, et al. Increased AKT S473 phosphorylation after mTORC1 inhibition is rictor dependent and does not predict tumor cell response to PI3K/mTOR inhibition. Mol Cancer Ther 2009;8:742-53.

    (23)    Lee M, Theodoropoulou M, Graw J, Roncaroli F, Zatelli MC, Pellegata NS. Levels of p27 sensitize to dual PI3K/mTOR inhibition. Mol Cancer Ther 2011;10:1450-9.

    (24)    Pollizzi K, Malinowska-Kolodziej I, Stumm M, Lane H, Kwiatkowski D. Equivalent benefit of mTORC1 blockade and combined PI3K-mTOR blockade in a mouse model of tuberous sclerosis. Mol Cancer 2009;8:38.

    (25)    Xu CX, Li Y, Yue P, Owonikoko TK, Ramalingam SS, Khuri FR, et al. The combination of RAD001 and NVP-BEZ235 exerts synergistic anticancer activity against non-small cell lung cancer in vitro and in vivo. PLoS One 2011;6:e20899.

    (26)    Yang S, Xiao X, Meng X, Leslie KK. A mechanism for synergy with combined mTOR and PI3 kinase inhibitors. PLoS One 2011;6:e26343.

Related Products

Cat.No. Product Name Information Publications Customer Product Validation
S1009 Dactolisib (BEZ235, NVP-BEZ235) Dactolisib (BEZ235, NVP-BEZ235) is a dual ATP-competitive PI3K and mTOR inhibitor for p110α/γ/δ/β and mTOR(p70S6K) with IC50 of 4 nM /5 nM /7 nM /75 nM /6 nM in cell-free assays, respectively. Inhibits ATR with IC50 of 21 nM in 3T3TopBP1-ER cell. (170) (11)

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