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787 New Allosteric Inhibitors of Mutant IDH1 in Acute Myeloid Leukemia

Molecular Pharmacology and Drug Resistance in Myeloid Diseases
Program: Oral and Poster Abstracts
Type: Oral
Session: 604. Molecular Pharmacology and Drug Resistance in Myeloid Diseases: Acute Myeloid Leukemia: Exploiting New Therapeutic Targets and Novel Technologies
Monday, December 7, 2015: 4:30 PM
W307, Level 3 (Orange County Convention Center)

Ujunwa Cynthia Okoye-Okafor, MS1, Boris Bartholdy, PhD2*, Jessy Cartier2*, Enoch Gao3*, Beth Pietrak3*, Alan R. Rendina3*, Cynthia Rominger4*, Chad Quinn3*, Angela Smallwood3*, Ken Wiggall5*, Alexander Reif5*, Stan Schmidt5*, Hongwei Qi3*, Huizhen Zhao3*, Gerard Joberty3*, Maria Faelth-Savitski3*, Marcus Bantscheff3*, Gerard Drewes3*, Chaya Duraiswami3*, Pat Brady3*, Swathi-rao Narayanagari6*, Ileana Antony-Debre, PhD, PharmD7*, Kelly Mitchell6*, Luis Carvajal8*, Heng Rui Wang8*, Laura Barreyro, PhD8, Yun-Ruei Kao8*, Maximilian Christopeit, MD9, Elisabeth Paietta, PhD10, Hideki Makishima, MD, Ph.D.11, Britta Will, PhD2*, Nestor Concha3*, Nicholas Adams12*, Benjamin Schwartz3*, Michael T. McCabe, PhD12*, Jaroslaw P. Maciejewski, MD, PhD13, Amit Verma, MD14 and Ulrich Steidl, MD PhD8

1MD/PhD student, Albert Einstein College of Medicine, Bronx, NY
2Albert Einstein College of Medicine, Bronx, NY
3Department of Molecular Discovery Research, GlaxoSmithKline, Collegeville, PA
4GlaxoSmithKline, Collegeville
5Cancer Epigenetics Discovery Performance Unit, GlaxoSmithKline, Collegeville, PA
6Albert Einstein College of Medicine, Bronx
7Albert Einstein College of Medicine, New York, NY
8Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY
9Oncology/Hematology, Internal Medicine, University Hospital Halle (Saale), Halle, Germany
10Cancer Center, The North Division of Montefiore Medical Center, Bronx, NY
11Translational Hematology and Oncology Research, Cleveland Clinic, Cleveland, OH
12GlaxoSmithKline, Collegeville, PA
13Leukemia Program, Cleveland Clinic, Cleveland, OH
14Department of Medicine-Oncology, Albert Einstein College of Medicine, Bronx, NY

Mutations in the isocitrate dehydrogenase 1 (IDH1) gene are known driver mutations in acute myeloid leukemia (AML) and other cancer types. Patient outcomes in AML have remained poor, especially for patients above 60 years of age who typically do not tolerate high dose chemotherapy and stem cell transplantation, leading to cure rates below 20%. The development of novel targeted therapies for defined AML subtypes is urgently desired. Inhibitors of mutants of the closely related IDH2 gene as well as IDH1 have recently been described and show promising pre-clinical and early phase clinical activity. However, the specific molecular and functional effects of IDH1 inhibitors in AML, including in primary patients’ cells, have not been reported yet.

Here, we report the development of novel allosteric inhibitors of mutant IDH1 for differentiation therapy of acute myeloid leukemia. A high-throughput biochemical screen targeting an IDH1 heterodimer composed of R132H and WT IDH1 led to the identification of a tetrahydropyrazolopyridine series of inhibitors. Structural and biochemical analyses revealed that these novel compounds bind to an allosteric site that does not contact any of the mutant residues in the enzymes active site and inhibit enzymatic turnover. The enzyme complex locked in the catalytically inactive conformation inhibits the production of the oncometabolite 2-hydroxyglutarate (2-HG). In biochemical studies, we observed potent inhibition of several different clinically relevant R132 mutants in the presence or absence of the cofactor NADPH, accompanied by significant decrease in H3K9me2 levels.

Allosteric inhibitor treatment of primary AML patients’ cells with different clinically relevant R132 mutants of IDH1 ex vivo uniformly led to a decrease in intracellular 2-HG, abrogation of the myeloid differentiation block, increased cell death and induction of differentiation both at the level of leukemic blasts and immature stem-like cells. Allosteric inhibition of IDH1 also led to a decrease in blasts in an in vivo xenotransplantation model. At the molecular level, enhanced reduced representation bisulfite sequencing showed that treatment with allosteric IDH1 inhibitors led to a significant reversal of the DNA cytosine hypermethylation pattern induced by mutant IDH1, accompanied by gene expression changes of key sets of genes and pathways, including "Cell Cycle", "G1/S transition", "Cellular growth and proliferation", and "Cell death and survival".

Taken together, our findings provide novel insight into the cellular and molecular effects of inhibition of mutant IDH1 in primary AML patients’ cells. Furthermore, our study provides proof-of-concept for the molecular and biological activity of novel allosteric inhibitors for targeting of different mutant forms of IDH1 in leukemia, and opens new avenues for future investigations with these and other allosteric inhibitors for targeting mutant IDH1 in leukemia and other cancers.

Disclosures: Gao: GlaxoSmithKline: Employment . Pietrak: GlaxoSmithKline: Employment . Rendina: GlaxoSmithKline: Employment . Rominger: GlaxoSmithKline: Employment . Quinn: GlaxoSmithKline: Employment . Smallwood: GlaxoSmithKline: Employment . Wiggall: GlaxoSmithKline: Employment . Reif: GlaxoSmithKline: Employment . Schmidt: GlaxoSmithKline: Employment . Qi: GlaxoSmithKline: Employment . Zhao: GlaxoSmithKline: Employment . Joberty: GlaxoSmithKline: Employment . Faelth-Savitski: GlaxoSmithKline: Employment . Bantscheff: GlaxoSmithKline: Employment . Drewes: GlaxoSmithKline: Employment . Duraiswami: GlaxoSmithKline: Employment . Brady: GlaxoSmithKline: Employment . Concha: GlaxoSmithKline: Employment . Adams: GlaxoSmithKline: Employment . Schwartz: GlaxoSmithKline: Employment . McCabe: GlaxoSmithKline: Employment .

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