AG-120, an Oral, Selective, First-in-Class, Potent Inhibitor of Mutant IDH1, Reduces Intracellular 2HG and Induces Cellular Differentiation in TF-1 R132H Cells and Primary Human IDH1 Mutant AML Patient Samples Treated Ex Vivo

Abstract

Point mutations in isocitrate dehydrogenase (IDH) define distinct subsets of acute myelogenous leukemia (AML). IDH is a metabolic enzyme that interconverts isocitrate and α-ketoglutarate (α-KG), but cancer-associated point mutations in IDH1 and IDH2 confer a neomorphic activity that allows reduction of α-KG to the oncometabolite R-2-hydroxyglutarate (2-HG). High levels of 2-HG have been shown to inhibit α-KG-dependent dioxygenases including histone and DNA demethylases, which play a key role in regulating the epigenetic state of cells, but the relationship between 2-HG and oncogenesis is not completely understood. Consistent with 2-HG promoting cancer via an effect on chromatin structure, patients harboring IDH mutations display a CpG island methylator phenotype (CIMP) and several studies have shown that overexpression of IDH mutant enzymes can induce histone and DNA hypermethylation as well as block cellular differentiation. In addition, mice engineered to express IDH1-R132H in hematopoietic tissue have increased early hematopoietic progenitors, splenomegaly, anemia, hypermethylated histones and altered DNA methylation patterns similar to those found in AML patients harboring IDH1/2 mutations.[i] Taken together, these data suggest that cancer-associated IDH mutations may induce a block in cellular differentiation to promote tumorigenesis. To investigate whether selective pharmacological inhibition of the mutant IDH1 enzyme could provide an effective way to lower intracellular 2-HG levels and restore normal differentiation, we treated TF-1 cells or primary human AML patient samples expressing mutant IDH1 with AG-120, an oral, selective, first-in-class, potent IDH1 mutant inhibitor currently in phase I clinical trials. Treatment with AG-120 decreased intracellular 2-HG levels, inhibited growth factor independent proliferation and restored erythropoietin (EPO)-induced differentiation in TF-1 IDH1-R132H cells. Similarly, pharmacological inhibition of mutant IDH1 enzyme with AG-120 in primary human blast cells cultured ex vivo provided an effective way to lower intracellular 2-HG levels and induced myeloid differentiation. Taken together, these data demonstrate that AG-120 is effective at lowering 2-HG levels and restoring cellular differentiation, and support further clinical development of this compound. Figure 1: Diagnosis and karyotypes of primary AML patient samples used in ex vivo studies Figure 1:. Diagnosis and karyotypes of primary AML patient samples used in ex vivo studies PB = peripheral blood, BM = bone marrow Figure 2: Percent 2-HG remaining relative to DMSO control after 6-day treatment with AG-120 in IDH1 R132H or IDH1 R132C patient samples Figure 2:. Percent 2-HG remaining relative to DMSO control after 6-day treatment with AG-120 in IDH1 R132H or IDH1 R132C patient samples or following 6 days of treatment with control (DMSO) or AG-120 (0.5, 1.0, and 5.0 μM) Figure 3: Relative proportion of cell types in human AML bone marrow samples untreated Figure 3:. Relative proportion of cell types in human AML bone marrow samples untreated [i] M. Sasaki et al., IDH1(R132H) mutation increases murine haematopoietic progenitors and alters epigenetics. Nature 488(7413):656-9, 2012. Disclosures Hansen: Agios Pharmaceuticals: Employment, Stockholder Other. Quivoron:Institut National de la Santé Et de la Recherche Médicale (INSERM): Grant Other; Association Laurette Fugain: Grant, Grant Other; Institut National du Cancer (INCa): Grant, Grant Other; Association pour la recherche contre le Cancer (ARC): Grant, Grant Other; AGIOS: Grant Other. Straley:Agios Pharmaceuticals: Employment, Stockholder Other. Lemieux:Agios Pharmaceuticals: Employment, Stockholder Other, US20130190249 (pending) Patents & Royalties. Popovici-Muller:Agios Pharmaceuticals: Employment, Stockholder Other. Fathi:Agios Pharmaceuticals: Advisory board participation Other. Gliser:Agios Pharmaceuticals: Employment, Stockholder Other. David:Institut National de la Santé Et de la Recherche Médicale (INSERM): Grant Other; Institut National du Cancer (INCa): Grant, Grant Other; Association pour la Recherche contre le Cancer (ARC): Grant, Grant Other; Association Laurette Fugain: Grant, Grant Other; AGIOS: Grant Other. Bernard:Institut National de la Santé Et de la Recherche Médicale (INSERM): Grant Other; Association Laurette Fugain: Grant, Grant Other; Institut National du Cancer (INCa): Grant, Grant Other; Ligue Nationale contre le cancer (LNCC): Grant, Grant Other; AGIOS: Grant Other. Dorsch:Agios Pharmaceuticals: Employment, Stockholder Other. Yang:Agios Pharmaceuticals: Employment, Stockholder Other. Su:Agios Pharmaceuticals: Employment, Stockholder Other. Agresta:Agios Pharmaceuticals: Employment, Stockholder Other. de Botton:AGIOS: Grant Other. Penard-Lacronique:Institut National de la Santé Et de la Recherche Médicale (INSERM): Grant Other; Association Laurette Fugain: Grant, Grant Other; Institut National du Cancer (INCa): Grant, Grant Other; Association pour la recherche contre le Cancer (ARC): Grant, Grant Other; AGIOS: Grant Other. Yen:Agios Pharmaceuticals: Employment, Stockholder Other.

Acute Myeloid Leukemia: A Concise Review

“…The IDH1 inhibitor AG-120 and the IDH2 inhibitor AG-221 have demonstrated promising response rates in patients with AML in two separate phase I clinical trials [ 98 , 99 ]. Preliminary results were recently presented for both trials.…”

Clinical pharmacokinetics and pharmacodynamics of ivosidenib, an oral, targeted inhibitor of mutant IDH1, in patients with advanced solid tumors

“…Ivosidenib (AG-120) is a selective, potent inhibitor of the mutant IDH1 protein [6]. Preclinical studies showed that treatment with ivosidenib decreased intracellular 2-HG levels in IDH1-mutant AML cells in vitro [7], and resulted in 2-HG inhibition in tumors in an IDH1-mutant xenograft mouse model [6]. These data were used to predict the exposure required for efficacy in humans.…”

The Time Has Come for Targeted Therapies for AML: Lights and Shadows

“…Ivosidenib and enasidenib are two orally available selective inhibitors of mutant IDH1 and IDH2, and have been shown to decrease cellular 2-HG production by more than 90%, thus reducing histone and DNA hypermethylation and inducing myeloid differentiation [37,38].…”