Background. Isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) mutations are found in 10 and 15% of acute myeloid leukemia (AML) patients, respectively. IDH1/2 mutants' proteins produce high 2-hydroxyglutarate (2HG) levels that inhibit α-ketoglutarate-dependent dioxygenases including histone and DNA demethylases, as TET2 proteins. Furthermore, serum 2HG can act as a biomarker predictive of the presence of IDH1 and IDH2 mutations at diagnosis (cut-off value >2µM) but also correlate with response after intensive chemotherapy. 5-azacitidine (AZA) is a DNA methyltransferase inhibitor that demonstrated significant clinical benefit not only in high-risk MDS but also in AML. Hypomethylating agents yield higher response rate in the context of CpG island hypermethylation phenotype induced by TET2 mutations in myelodysplastic syndrome (MDS). Thus, we evaluate AZA response in the context of IDH1/2 mutations and the effect of AZA on serum 2HG production.

Patients and methods. The present study retrospectively focused on IDH1/2 mutant AML/MDS patients treated in our center with at least 1 cycle of AZA. IDH1/2 mutational status was evaluated in all patients with Sanger or Next-Generation sequencing before therapy. All patients received subcutaneous AZA 75mg/m2/d for 7 days every 28 days. Response to therapy was evaluated according to modified 2003 IWG criteria's for AML. Hematological improvement (HI) was evaluated according to IWG 2006 criteria's for MDS. Overall survival (OS) was censored in case of IDH1/2 inhibitor therapy after AZA. Serum samples were analyzed for total 2HG by reverse-phase liquid chromatography coupled to mass spectrometry.

Results. Thirty-six patients (34 AML, 2 MDS) were retrospectively analyzed. Initial characteristics of the patients are shown on Table 1. Median age was 74.3 years (range, 48.4-86). Thirteen patients (36%) had IDH1 mutations (R132C: 10, R132H: 2, R132G: 1) and 22 patients (61%) had IDH2 mutations (R140Q: 19, R172K: 3). One patient had both IDH1 R132H and IDH2 R140Q mutations. Twenty-nine patients had intermediate cytogenetic (including normal karyotype in 20 patients) and 6/36 unfavorable. IDH1/2 mutations were associated with SRSF2 mutations in 13 patients, DNMT3A in 11 patients, NPM1 mutation in 9 patients, ASXL1 in 5 patients and FLT3 -ITD in 5 patients. Ten patients (28%) were treated frontline with AZA while the others received AZA as second line (50%, including 6 patients with primary refractory AML to intensive chemotherapy) or subsequent lines (22%). Five patients received IDH1/2 inhibitors (AG221: 3, AG120: 2) prior to AZA treatment. Patients received a median of 4.5 cycles of AZA (range, 1-23). Four patients (11%) achieved complete remission (CR) and 7 (19%) obtained HI with persistent excess of blasts (overall response rate: 30%). Median OS was 9.5 months (FU range, 0.2-41.6) with a trend toward shorter OS in IDH1 mutant AML patient (6.4 vs 10.1; p≤0.0764) (Figure 1). No difference was observed between patients in 1st or subsequent treatment lines (p≤0.7265).

Median 2HG concentration (available in 25/36 patients) before the onset of AZA treatment was 9.7µM. Seventeen patients had available serum during follow-up (median: 2 measures/patient). When 2HG values in responding and non-responding patients were compared at different time-points, 2HG values remained elevated in responders (median 2HG: 6.8µM; range 0.99-13.5) without significant difference compared to baseline or relapse values (Figure 2). All responders to AZA ultimately relapsed or progressed during follow-up. IDH1 or IDH2 mutations persisted at relapse along with elevated 2HG levels (median 2HG: 4.5µM).

Discussion. In the present series, IDH1/2 mutations were not associated with an increased sensitivity to AZA, as opposed to TET2 mutations. AZA may decrease production of 2HG in responders compared to diagnosis values. However, unlike intensive chemotherapy, AZA is unable to normalize 2HG values in responding patients. This suggests that 2HG cannot be used as a surrogate marker of AZA response and AZA efficacy might not be related to inhibition of 2HG production in IDH1/2 AML/MDS patients. Thus, combinations of AZA with IDH1/2 mutant proteins inhibitors might lead to an additive or synergistic antitumor effect.


Renneville: CELGENE: Research Funding. Ribrag: Roche: Honoraria, Other: travel, accommodation, expenses; BMS: Consultancy, Honoraria; MSD: Consultancy, Honoraria; Infinity: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Nanostring: Consultancy, Honoraria; Epizyme: Consultancy, Honoraria; Pharmamar: Consultancy; Esai: Honoraria, Research Funding; ArgenX: Research Funding; Servier: Consultancy, Honoraria. de Botton: Celgene Corporatation: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; Servier: Honoraria; Agios Pharmaceuticals, Inc.: Honoraria, Research Funding.

Author notes


Asterisk with author names denotes non-ASH members.