Biological characterization of SN 32976 , a selective inhibitor of PI 3 K and mTOR with preferential activity to PI 3 K α , in comparison to established pan PI 3 K inhibitors

Multiple therapeutic agents have been developed to target the phosphatidylinositol 3-kinase (PI3K) signaling pathway, which is frequently dysregulated in cancer promoting tumor growth and survival. These include pan PI3K inhibitors, which target class Ia PI3K isoforms and have largely shown limited single agent activity with narrow therapeutic windows in clinical trials. Here, we characterize SN32976, a novel pan PI3K inhibitor, for its biochemical potency against PI3K isoforms and mTOR, kinase selectivity, cellular activity, pharmacokinetics, pharmacodynamics and antitumor efficacy relative to five clinically-evaluated pan PI3K inhibitors: buparlisib, dactolisib, pictilisib, omipalisib and ZSTK474. SN32976 potently inhibited PI3K isoforms and mTOR, displaying preferential activity for PI3Kα and sparing of PI3Kδ relative to the other inhibitors, while showing less off-target activity than the clinical inhibitors in a panel of 442 kinases. The major metabolites of SN32976 were also potent PI3K inhibitors with similar selectivity for PI3Kα as the parent compound. SN32976 compared favorably with the clinically-evaluated PI3K inhibitors in cellular assays, inhibiting pAKT expression and cell proliferation at nM concentrations, and in animal models, inducing a greater extent and duration of pAKT inhibition in tumors than pictilisib, dactolisib and omipalisib at similarly tolerated dose levels and inhibiting tumor growth to a greater extent than dactolisib and ZSTK474 and with similar efficacy to pictilisib and omipalisib. These results suggest that SN32976 is a promising clinical candidate for cancer therapy with enhanced kinase selectivity and preferential inhibition of PI3Kα compared to first generation pan PI3K inhibitors, while retaining comparable anticancer activity. www.impactjournals.com/oncotarget/ Oncotarget, 2017, Vol. 8, (No. 29), pp: 47725-47740

[1]  P. Lønning,et al.  Abstract S4-07: BELLE-3: A phase III study of buparlisib + fulvestrant in postmenopausal women with HR+, HER2–, aromatase inhibitor-treated, locally advanced or metastatic breast cancer, who progressed on or after mTOR inhibitor-based treatment , 2017 .

[2]  M. Campone,et al.  A randomized adaptive phase II/III study of buparlisib, a pan-class I PI3K inhibitor, combined with paclitaxel for the treatment of HER2– advanced breast cancer (BELLE-4) , 2016, Annals of oncology : official journal of the European Society for Medical Oncology.

[3]  Philippe Foubert,et al.  PI3Kγ is a molecular switch that controls immune suppression , 2016, Nature.

[4]  T. Fojo,et al.  BEZ235: When Promising Science Meets Clinical Reality , 2016, The oncologist.

[5]  L. Rassenti,et al.  Idelalisib given front-line for treatment of chronic lymphocytic leukemia causes frequent immune-mediated hepatotoxicity. , 2016, Blood.

[6]  M. Ellis,et al.  Pictilisib for oestrogen receptor-positive, aromatase inhibitor-resistant, advanced or metastatic breast cancer (FERGI): a randomised, double-blind, placebo-controlled, phase 2 trial. , 2016, The Lancet. Oncology.

[7]  L. Pusztai,et al.  A phase II study of the PI3K inhibitor taselisib (GDC-0032) combined with fulvestrant (F) in patients (pts) with HER2-negative (HER2-), hormone receptor-positive (HR+) advanced breast cancer (BC). , 2016 .

[8]  Sung-Bae Kim,et al.  BERIL-1: A phase II, placebo-controlled study of buparlisib (BKM120) plus paclitaxel in patients with platinum-pretreated recurrent/metastatic head and neck squamous cell carcinoma (HNSCC). , 2016 .

[9]  E. Winer,et al.  A Phase Ib Study of Alpelisib (BYL719), a PI3Kα-Specific Inhibitor, with Letrozole in ER+/HER2− Metastatic Breast Cancer , 2016, Clinical Cancer Research.

[10]  M. Falasca,et al.  Novel roles for class II Phosphoinositide 3-Kinase C2β in signalling pathways involved in prostate cancer cell invasion , 2016, Scientific Reports.

[11]  J. Baselga,et al.  Abstract S6-01:PIK3CAstatus in circulating tumor DNA (ctDNA) predicts efficacy of buparlisib (BUP) plus fulvestrant (FULV) in postmenopausal women with endocrine-resistant HR+/HER2– advanced breast cancer (BC): First results from the randomized, phase III BELLE-2 trial: , 2016 .

[12]  Paul Workman,et al.  Drugging PI3K in cancer: refining targets and therapeutic strategies , 2015, Current opinion in pharmacology.

[13]  G. Rewcastle,et al.  Inhibitors of pan-PI3K Signaling Synergize with BRAF or MEK Inhibitors to Prevent BRAF-Mutant Melanoma Cell Growth , 2015, Front. Oncol..

[14]  I. Jennings,et al.  Class II but Not Second Class-Prospects for the Development of Class II PI3K Inhibitors. , 2015, ACS medicinal chemistry letters.

[15]  R. Herbst,et al.  A phase I/II, first-in-human dose-escalation study of GSK2636771 in patients (pts) with PTEN-deficient advanced tumors. , 2014 .

[16]  Hung-Ming Wang,et al.  Phase lb/ll study of the PI3Kα inhibitor BYL719 in combination with cetuximab in recurrent/metastatic squamous cell cancer of the head and neck (SCCHN). , 2014 .

[17]  D. Erdmann,et al.  Characterization of the Novel and Specific PI3Kα Inhibitor NVP-BYL719 and Development of the Patient Stratification Strategy for Clinical Trials , 2014, Molecular Cancer Therapeutics.

[18]  Doriano Fabbro,et al.  Discovery of NVP-BYL719 a potent and selective phosphatidylinositol-3 kinase alpha inhibitor selected for clinical evaluation. , 2013, Bioorganic & medicinal chemistry letters.

[19]  Steve Price,et al.  Discovery of 2-{3-[2-(1-isopropyl-3-methyl-1H-1,2-4-triazol-5-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepin-9-yl]-1H-pyrazol-1-yl}-2-methylpropanamide (GDC-0032): a β-sparing phosphoinositide 3-kinase inhibitor with high unbound exposure and robust in vivo antitumor activity. , 2013, Journal of medicinal chemistry.

[20]  F. Gosselin,et al.  A Practical Synthesis of a PI3K Inhibitor under Noncryogenic Conditions via Functionalization of a Lithium Triarylmagnesiate Intermediate , 2013 .

[21]  Mengrou Lu,et al.  Selective Inhibition of Phosphoinositide 3-Kinase p110α Preserves Lymphocyte Function* , 2012, The Journal of Biological Chemistry.

[22]  Benjamin E. Gross,et al.  The cBio cancer genomics portal: an open platform for exploring multidimensional cancer genomics data. , 2012, Cancer discovery.

[23]  Jordi Rodon,et al.  Phase I, dose-escalation study of BKM120, an oral pan-Class I PI3K inhibitor, in patients with advanced solid tumors. , 2012, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[24]  W. Sellers,et al.  Identification and Characterization of NVP-BKM120, an Orally Available Pan-Class I PI3-Kinase Inhibitor , 2011, Molecular Cancer Therapeutics.

[25]  G. Rewcastle,et al.  Effects of acutely inhibiting PI3K isoforms and mTOR on regulation of glucose metabolism in vivo , 2011, The Biochemical journal.

[26]  A. Maity,et al.  PI3K/AKT/mTOR Pathway in Angiogenesis , 2011, Front. Mol. Neurosci..

[27]  Claire L. Lill,et al.  Synthesis and biological evaluation of novel analogues of the pan class I phosphatidylinositol 3-kinase (PI3K) inhibitor 2-(difluoromethyl)-1-[4,6-di(4-morpholinyl)-1,3,5-triazin-2-yl]-1H-benzimidazole (ZSTK474). , 2011, Journal of medicinal chemistry.

[28]  Simon Ng,et al.  Identification of NVP-BKM120 as a Potent, Selective, Orally Bioavailable Class I PI3 Kinase Inhibitor for Treating Cancer. , 2011, ACS medicinal chemistry letters.

[29]  W. Denny,et al.  A drug targeting only p110α can block phosphoinositide 3-kinase signalling and tumour growth in certain cell types , 2011, The Biochemical journal.

[30]  J. Schellens,et al.  Phase I first-in-human study of the PI3 kinase inhibitor GSK2126458 (GSK458) in patients with advanced solid tumors (study P3K112826). , 2011, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[31]  J. Engelman,et al.  The PI3K pathway as drug target in human cancer. , 2010, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[32]  M. Belvin,et al.  Isoform-specific phosphoinositide 3-kinase inhibitors exert distinct effects in solid tumors. , 2010, Cancer research.

[33]  Kaushik Raha,et al.  Discovery of GSK2126458, a Highly Potent Inhibitor of PI3K and the Mammalian Target of Rapamycin. , 2010, ACS medicinal chemistry letters.

[34]  P. Workman,et al.  Biological properties of potent inhibitors of class I phosphatidylinositide 3-kinases: from PI-103 through PI-540, PI-620 to the oral agent GDC-0941 , 2009, Molecular Cancer Therapeutics.

[35]  A. Ridley,et al.  Phosphoinositide 3‐kinases in cell migration , 2009, Biology of the cell.

[36]  Gary Box,et al.  The identification of 2-(1H-indazol-4-yl)-6-(4-methanesulfonyl-piperazin-1-ylmethyl)-4-morpholin-4-yl-thieno[3,2-d]pyrimidine (GDC-0941) as a potent, selective, orally bioavailable inhibitor of class I PI3 kinase for the treatment of cancer . , 2008, Journal of medicinal chemistry.

[37]  Daniela Gabriel,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 , 2008, Molecular Cancer Therapeutics.

[38]  마르쿠스 밴치거,et al.  Salts and crystal forms of 2-methyl-2-[4-(3-methyl-2-oxo-8-quinolin-3-yl-2,3-dihydro-imidazo[4,5-c]quinolin-1-yl)-phenyl]-propionitrile , 2007 .

[39]  Dexin Kong,et al.  ZSTK474 is an ATP‐competitive inhibitor of class I phosphatidylinositol 3 kinase isoforms , 2007, Cancer science.

[40]  K. Okkenhaug,et al.  Cutting Edge: The Phosphoinositide 3-Kinase p110δ Is Critical for the Function of CD4+CD25+Foxp3+ Regulatory T Cells1 , 2006, The Journal of Immunology.

[41]  S. Hirono,et al.  Antitumor activity of ZSTK474, a new phosphatidylinositol 3-kinase inhibitor. , 2006, Journal of the National Cancer Institute.

[42]  Li Zhao,et al.  Oncogenic PI3K deregulates transcription and translation , 2005, Nature Reviews Cancer.

[43]  Y. Samuels,et al.  Oncogenic mutations of PIK3CA in human cancers. , 2004, Current topics in microbiology and immunology.

[44]  C. Sawyers,et al.  The phosphatidylinositol 3-Kinase–AKT pathway in human cancer , 2002, Nature Reviews Cancer.

[45]  T. Miller,et al.  Therapeutic targeting of cancers with loss of PTEN function. , 2014, Current drug targets.

[46]  B. Baguley,et al.  Anticancer drug sensitivity profiles of new and established melanoma cell lines. , 1993, Oncology research.