Iyer, Sunil Girish

Abstract Introduction: Isocitrate dehydrogenase (IDH) mutations are observed in ~20% of patients with acute myeloid leukemia (AML). In the U.S., ivosidenib (ivo) is approved with or without azacitidine (aza) in the frontline (FL) and as monotherapy in relapsed/refractory (R/R) IDH1-mutated (mut) AML. Olutasidenib (oluta) is approved as monotherapy for R/R IDH1-mut AML. Enasidenib (ena) is approved as monotherapy for R/R IDH2-mut AML. This study describes real-world IDH inhibitor (IDHi) administration patterns and evaluates their outcomes in on-label settings. Methods: A retrospective review of patients with IDH1/2-mut AML who received ivosidenib, olutasidenib, or enasidenib was conducted at 12 academic institutions in the U.S. Best response at any time during treatment, including complete response (CR) and complete response with partial hematologic recovery (CRh), were graded using European Leukemia Net (ELN) 2022 criteria. Results: A total of 387 patients with IDH1- and IDH2-mut AML were treated with an IDHi in the FL or R/R setting. Median follow-up was 9.6 months (range, 0.03-90.7). Demographics include 79% White, 14% Black, 3% Asian, and 4% other/unknown race; 5% were Hispanic ethnicity; 46% were female; the median age was 70 years (range, 28-95). 70% had an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1, 26% had secondary AML, and 10% had therapy-related AML. Per the ELN 2024 less-Intensive risk classification, 58% were favorable risk, 29% intermediate, 7% adverse, and 6% unknown. Overall, 209 of 387 patients (54%) received IDHi regimens on-label. In FL IDH1-mut AML (n=45), 11 received ivo monotherapy, 25 aza/ivo, and 9 used off-label combinations: 3 hypomethylating agent (HMA) + venetoclax (ven) + ivo, 5 decitabine/ivo, 1 intensive chemotherapy (IC)/ivo. Among R/R IDH1-mut AML (n=109), 47 received ivo monotherapy, 7 oluta monotherapy, and 55 off-label (31 HMA/ivo, 16 HMA/ven/ivo, 3 IC/ivo, and 5 other). 44 received off-label ena for FL treatment of IDH2-mut AML (25 ena monotherapy, 9 HMA/ena, 8 HMA/ven/ena, and 2 IC/ena). In R/R IDH2-mut AML (n=189), 119 patients received ena monotherapy and 70 received off-label combinations (25 HMA/ena, 30 HMA/ven/ena, 7 IC/ena, 6 ena/gilteritinib, and 2 other). In on-label treatment of FL IDH1-mut AML, one of four patients with response assessment of FL ivo monotherapy had a CR/CRh. Of 19 patients with response assessment on FL aza/ivo, 13 patients (68.4%) had a CR as best response (95% CI, 46.0-84.6%). Median OS was 14.9 mo (95% CI, 4.17-NR) for ivo monotherapy (n=11) and 31.9 mo (95% CI, 9.1-NR) for aza/ivo (n=25), with 0 and 2 patients receiving allogeneic stem cell transplant (allo-SCT), respectively. In R/R IDH1-mut AML, the rate of CR/CRh was 35.5% (95% CI, 21.1-53.1) for on-label ivo monotherapy. All 4 patients with response assessment for on-label oluta monotherapy had a CR. Median OS was 14.0 mo (95% CI, 10.1-22.4) for ivo monotherapy and NR for oluta monotherapy (95% CI, 10.1-NR), with 10 and 0 receiving allo-SCT, respectively. The CR/CRh rate for ivo was 38.1% (8 of 21 assessed; 95% CI, 20.8-59.1) in age < 70, and 30.0% (3 of 10 assessed; 95% CI, 10.8-60.3) in age ≥ 70. Median OS was 15.2 mo (95% CI 9.3-NR) in age < 70 (n=27) and 10.4 mo (95% CI 8.0-18) in age ≥ 70 (n=20). In R/R IDH2-mut AML, the rate of CR/CRh for on-label ena monotherapy was 38.2% (95% CI, 27.6-50.1). Median OS was 12.1 mo (95% CI, 8.2-16.6), with 5 having received allo-SCT. In demographic subgroups for ena monotherapy, 52 non-Hispanic White (NHW) patients with response assessment had a CR/CRh rate of 42.3% (95% CI, 0.30-0.56). Only 1 of 13 non-Hispanic Black (NHB) patients with response assessment had a CRh (7.7%; 95% CI, 1.4-33.0) as best response, with none attaining CR. Median OS was 13.7 mo (95% CI 10.3-26.3) in NHW (n=82), 11.2 mo (95% CI, 6.1-NR) in NHB (n=18), and 69.1 mo (95% CI, 52.6-NR) in Hispanic patients (n=8). The CR/CRh rate was 48.6% (17 of 35 assessed; 95% CI, 33.0-64.4) for age < 70, and 27.3% (9 of 33 assessed; 95% CI, 15.1-44.2) for age ≥ 70. Median OS was 12.0 mo (95% CI, 9.9-22.1) in age < 70 (n=48) and 5.8 mo (95% CI, 4.1-8.7) in age ≥ 70 (n=69). Conclusion: Practice patterns for IDH inhibitors in AML vary considerably, with high amounts of off-label use. Response rates for ivosidenib and enasidenib in the real-world setting are comparable to those of clinical trials. Descriptive analyses of demographic subgroups highlight areas in need of further research.

Introduction: Detection of measurable residual disease (MRD) prior to allogeneic hematopoietic cell transplant (alloHCT) in patients with acute myeloid leukemia (AML) in remission is associated with increased relapse and inferior survival after transplant. We recently reported that next-generation sequencing (NGS) detection of mutated NPM1 or FLT3-ITD in first complete remission (CR1) blood prior to alloHCT is strongly associated with increased relapse and death (PMID: 36881031). However, the prognostic implications of detecting persistence of other common AML-associated mutations at this treatment landmark remain incompletely defined. Around 20% of patients diagnosed with AML have variants in isocitrate dehydrogenase ( IDH) genes (~7% for IDH1) and clinical outcomes are known to differ due to co-occurrence of other mutations, IDH subtypes, treatment strategies, and patient factors. Studies have examined the relationship between residual IDH1 variants ( IDH1m) in CR and subsequent clinical outcomes, but definitive standardized evidence to inform decision-making for the clinical utility of IDH1m as a target for AML MRD testing was not previously available. Methods: Adult patients undergoing alloHCT for IDH1 mutated AML in CR1 at CIBMTR sites in the USA between 2013-2019 were eligible for the study if remission blood sample collected within 100 days before alloHCT and outcome data were available. Ultrasensitive error-corrected NGS (NGS-MRD) targeting IDH1, NPM1, and FLT3 genes was performed on DNA from pre-conditioning blood to identify residual variants. Detected IDH1m were validated by digital droplet PCR (ddPCR). The day of transplant was considered as day 0. Median follow-up time was calculated for censored patients. Overall survival (OS) was estimated using Kaplan-Meier (log-rank tests) and Cox proportional hazards models (forward selection); cumulative incidence of relapse was examined using Fine-Gray regression models with non-relapse mortality as a competing risk. Results: A total of 148 patients were included in the study, with a median follow-up time of 24 months. Relapse was observed in 37 (25%) patients, with the majority occurring within 1 year after alloHCT (n = 28, 76%). Pre-transplant flow cytometry results were reported by the transplant centers for 97% of patients (n = 144), but no statistically significant differences in clinical outcomes were observed between the positive and negative groups (OS: p = 0.3; relapse: p = 0.07). 53 patients (36%) tested positive for IDH1m persistence in CR1, with a 100% validation rate by ddPCR for variants with an orthogonal assay available. Logistic regression indicated that IDH1m persistence in remission was more likely to occur in patients older than 40 years (OR: 1.02 with every 1-year increase after 40, p = 0.04). Clinical outcomes showed no statistically significant difference between the pre-alloHCT IDH1m positive and negative groups (Figure 1A), and this remained true after further subgroup analysis by age. The variant allele fraction (VAF) of the residual IDH1m ranged from 0.09% to 48.5% (median: 1.5%), and no differences in clinical outcomes were observed when stratifying by high (≥2.5%) or low VAF (<2.5%). Among patients with co-mutated NPM1 and/or FLT3-ITD at baseline (n=69), those with residual mutated NPM1 and/or FLT3-ITD in pre-transplant remission had significantly higher rates of relapse compared to those with residual IDH1m only or NGS-negative groups (p = 0.01, Figure 1B). The cohort excluding patients with co-mutated NPM1 and/or FLT3-ITD did not show any significant clinical outcome differences based on IDH1m persistence. Conditioning intensity did not show an association with clinical outcomes, and multivariable analysis for overall survival and relapse did not identify residual IDH1m as an important marker. Conclusion: Detection of persistent IDH1 variants in the blood of adult patients with AML in CR1 prior to first alloHCT is common, but not associated with increased relapse or death after transplant compared with those testing negative. For those patients with IDH1 mutated AML co-mutated with either NPM1 and/or FLT3-ITD, detection of persistent NPM1 and/or FLT3-ITD was associated with higher rates of relapse. These findings, from the largest study to date, do not support the detection of isolated IDH1 variants in CR1 blood prior to alloHCT as evidence of AML MRD or increased post-transplant relapse risk.

Introduction: Detection of measurable residual disease (MRD) in AML patients during remission is associated with adverse clinical outcomes after allogeneic hematopoietic cell transplant (alloHCT), including recent strong evidence from our group regarding residual NPM1 and/or FLT3-ITD variants (PMID: 36881031). Large studies examining the significance of other potential MRD targets, including isocitrate dehydrogenase isoform 2 ( IDH2), are needed. IDH2, which is mutated in approximately 12% of AML patients, is of particular interest due to the possibility of targeted clinical intervention. Methods: Patients over the age of 18 in first complete remission (CR1) with IDH2 mutated AML undergoing alloHCT transplant at a CIBMTR site between 2013-2019 with remission blood samples within 100 days of alloHCT and available clinical data were included in this study. Residual variants in IDH2, NPM1, and FLT3genes were detected by ultrasensitive error-corrected next-generation sequencing (NGS-MRD) on genomic DNA from pre-conditioning blood and validated by digital droplet PCR (ddPCR). The primary outcomes were overall survival (OS) and cumulative incidence of relapse with non-relapse mortality as a competing risk. The day of transplant was considered as time 0, and the median follow-up time was calculated for censored patients. Kaplan-Meier estimation (log-rank tests), Cox proportional hazards models, and Fine-Gray regression models were fitted to examine the clinical outcomes. Results: Among the 257 IDH2-mutated AML patients in this study, 57 (23%) experienced relapse, with 41 events occurring within 12 months after alloHCT. The median follow-up time was 25 months. Among 247 patients with pre-transplant remission flow cytometry results reported, 25% were positive, but no difference in rates of relapse or OS was observed between positive and negative patients. NGS MRD analysis detected residual IDH2 variants in remission samples of 130 patients (51%) with variant allele fraction (VAF) ranging from 0.05-56% (median: 3%), and 100% validation by ddPCR. NGS MRD IDH2 positive patients had increased rates of relapse (p = 0.03; 3yr: +11%, 95% CI: 0.2% to 22%) and decreased OS (p < 0.001; 3yr: -25%, 95% CI: -13% to -38%) compared to those who tested negative (Figure 1A). These OS differences were still observed between NGS MRD IDH2 positive and negative patients, regardless of age stratification (under 60yr p < 0.001, 3yr: -28%, 95% CI: -12% to -43%; over 60yr p = 0.04, 3yr: -19%, 95% CI: -1% to -40%); however, only patients over 60yrs had increased rates of relapse (p = 0.007; 3yr: +21, 95% CI: 6% to 36%). The impact of co-mutation status was examined by subdividing the cohort based on the presence of NPM1 or FLT3-ITD mutations at baseline. Residual IDH2 variants in patients without baseline NPM1 or FLT3-ITD co-mutations (n = 151) were associated with decreased OS and increased relapse ( IDH2+ vs IDH2-; OS p = 0.005, 3yr: -23%, 95% CI: -6% to -40%; Relapse p = 0.01, 3yr: +19, 95% CI: 6% to 32%; Figure 1B). In contrast, residual IDH2 variants were not predictive of relapse in co-mutated patients (n=106, p = 0.5). In these patients, the only prognostic marker for relapse was NPM1 and/or FLT3-ITD MRD, with similar relapse risk between IDH2 only positive and MRD negative groups (p < 0.001; 3yr: 83% vs. 11% vs. 15%; Figure 1B). In multivariable analysis, IDH2 MRD positivity was associated with decreased OS (HR 2.5, 95% CI: 1.5-4.2, p < 0.001) and increased rates of relapse (HR 2.1, 95% CI: 1.4-5.7, p = 0.003) after adjusting for other characteristics. Conclusion: In this study, we demonstrate that adult patients with IDH2-mutated AML who have IDH2 variants detected in CR1 prior to first alloHCT experienced increased relapse rates and decreased overall survival. However, this association is significant only in patients without baseline NPM1 and FLT3-ITD mutations. In co-mutated patients, NPM1 and/or FLT3-ITD MRD serve as superior prognostic markers. Subgroup analyses show the potential influence of factors such as conditioning intensity and age on clinical outcomes. Nevertheless, larger studies with balanced subgroups and more comprehensive baseline mutational information, including IDH2 mutation subtype, are needed to better define the clinical relevance of IDH2 MRD in this context.