Combination of dasatinib and venetoclax in newly diagnosed chronic phase chronic myeloid leukemia

BACKGROUND

The dual inhibition of the BCR::ABL1 tyrosine kinase and BCL-2 could potentially deepen the response rates of chronic myeloid leukemia in chronic phase (CML-CP). This study evaluated the safety and efficacy of the combination of dasatinib and venetoclax.

METHODS

In this phase 2 trial, patients with CML-CP or accelerated phase (clonal evolution) received dasatinib 50 mg/day for three courses; venetoclax was added in course 4 for 3 years. The initial venetoclax dose was 200 mg/day continuously but reduced later to 200 mg/day for 14 days, and to 100 mg/day for 7 days per course once a molecular response (MR)4.5 was achieved. After 3 years of combination, patients were maintained on single-agent dasatinib. The primary end point was the rate of major molecular response (MMR) by 12 months of combination.

RESULTS

Sixty-five patients were treated. Their median age was 46 years (range, 23-73). By 12 months of combination, the MMR, MR4, and MR4.5 rates were 86%, 53%, and 45%, respectively. After a median follow-up of 42 months, the 4-year event-free and overall survival rates were 96% and 100%, respectively. Outcomes with the combination were comparable to historical outcomes with single-agent dasatinib (cumulative 12-months MMR rate of 79% with both strategies). The incidence of grade 3-4 neutropenia was 22% with the combination and 11% with single-agent dasatinib (p < .001).

CONCLUSIONS

Treatment with dasatinib and venetoclax was safe and effective in CML-CP. The cumulative response rates with the combination were similar to those with single-agent dasatinib. Further follow-up is needed to evaluate the rates of durable deep molecular response and treatment-free remission.

Mitochondrial regulation of GPX4 inhibition-mediated ferroptosis in acute myeloid leukemia

Resistance to apoptosis in acute myeloid leukemia (AML) cells causes refractory or relapsed disease, associated with dismal clinical outcomes. Ferroptosis, a mode of non-apoptotic cell death triggered by iron-dependent lipid peroxidation, has been investigated as potential therapeutic modality against therapy-resistant cancers, but our knowledge of its role in AML is limited. We investigated ferroptosis in AML cells and identified its mitochondrial regulation as a therapeutic vulnerability. GPX4 knockdown induced ferroptosis in AML cells, accompanied with characteristic mitochondrial lipid peroxidation, exerting anti-AML effects in vitro and in vivo. Electron transport chains (ETC) are primary sources of coenzyme Q10 (CoQ) recycling for its function of anti-lipid peroxidation in mitochondria. We found that the mitochondria-specific CoQ potently inhibited GPX4 inhibition-mediated ferroptosis, suggesting that mitochondrial lipid redox regulates ferroptosis in AML cells. Consistently, Rho0 cells, which lack functional ETC, were more sensitive to GPX4 inhibition-mediated mitochondrial lipid peroxidation and ferroptosis than control cells. Furthermore, degradation of ETC through hyperactivation of a mitochondrial protease, caseinolytic protease P (ClpP), synergistically enhanced the anti-AML effects of GPX4 inhibition. Collectively, our findings indicate that in AML cells, GPX4 inhibition induces ferroptosis, which is regulated by mitochondrial lipid redox and ETC.

Venetoclax and Cobimetinib in Relapsed/Refractory AML: A Phase 1b Trial

BACKGROUND

Therapies for relapsed/refractory acute myeloid leukemia remain limited and outcomes poor, especially amongst patients who are ineligible for cytotoxic chemotherapy or targeted therapies.

PATIENTS AND METHODS

This phase 1b trial evaluated venetoclax, a B-cell lymphoma-2 (BCL-2) inhibitor, plus cobimetinib, a MEK1/2 inhibitor, in patients with relapsed/refractory acute myeloid leukemia, ineligible for cytotoxic chemotherapy. Two-dimensional dose-escalation was performed for venetoclax dosed daily, and for cobimetinib dosed on days 1-21 of each 28-day cycle.

RESULTS

Thirty patients (median [range] age: 71.5 years [60-84]) received venetoclax-cobimetinib. The most common adverse events (AEs; in ≥40.0% of patients) were diarrhea (80.0%), nausea (60.0%), vomiting (40.0%), febrile neutropenia (40.0%), and fatigue (40.0%). Overall, 66.7% and 23.3% of patients experienced AEs leading to dose modification/interruption or treatment withdrawal, respectively. The composite complete remission (CRc) rate (complete remission [CR] + CR with incomplete blood count recovery + CR with incomplete platelet recovery) was 15.6%; antileukemic response rate (CRc + morphologic leukemia-free state/partial remission) was 18.8%. For the recommended phase 2 dose (venetoclax: 600 mg; cobimetinib: 40 mg), CRc and antileukemic response rates were both 12.5%. Failure to achieve an antileukemic response was associated with elevated baseline phosphorylated ERK and MCL-1 levels, but not BCL-xL. Baseline mutations in ≥1 signaling gene or TP53 were noted in nonresponders and emerged on treatment. Pharmacodynamic biomarkers revealed inconsistent, transient inhibition of the mitogen-activated protein kinase (MAPK) pathway.

CONCLUSION

Venetoclax-cobimetinib showed limited preliminary efficacy similar to single-agent venetoclax, but with added toxicity. Our findings will inform future trials of BCL-2/MAPK pathway inhibitor combinations.

Enhanced TP53 reactivation disrupts MYC transcriptional program and overcomes venetoclax resistance in acute myeloid leukemias

The tumor suppressor TP53 is frequently inactivated in a mutation-independent manner in cancers and is reactivated by inhibiting its negative regulators. We here cotarget MDM2 and the nuclear exporter XPO1 to maximize transcriptional activity of p53. MDM2/XPO1 inhibition accumulated nuclear p53 and elicited a 25- to 60-fold increase of its transcriptional targets. TP53 regulates MYC, and MDM2/XPO1 inhibition disrupted the c-MYC-regulated transcriptome, resulting in the synergistic induction of apoptosis in acute myeloid leukemia (AML). Unexpectedly, venetoclax-resistant AMLs express high levels of c-MYC and are vulnerable to MDM2/XPO1 inhibition in vivo. However, AML cells persisting after MDM2/XPO1 inhibition exhibit a quiescence- and stress response-associated phenotype. Venetoclax overcomes that resistance, as shown by single-cell mass cytometry. The triple inhibition of MDM2, XPO1, and BCL2 was highly effective against venetoclax-resistant AML in vivo. Our results propose a novel, highly translatable therapeutic approach leveraging p53 reactivation to overcome nongenetic, stress-adapted venetoclax resistance.

Co-targeting BCL-XL and BCL-2 by PROTAC 753B eliminates leukemia cells and enhances efficacy of chemotherapy by targeting senescent cells

BCL-XL and BCL-2 are key anti-apoptotic proteins and validated cancer targets. 753B is a novel BCL-XL/BCL-2 proteolysis targeting chimera (PROTAC) that targets both BCL-XL and BCL-2 to the von Hippel-Lindau (VHL) E3 ligase, leading to BCLX L/BCL-2 ubiquitination and degradation selectively in cells expressing VHL. Because platelets lack VHL expression, 753B spares on-target platelet toxicity caused by the first-generation dual BCL-XL/BCL-2 inhibitor navitoclax (ABT-263). Here, we report pre-clinical single-agent activity of 753B against different leukemia subsets. 753B effectively reduced cell viability and induced dose-dependent degradation of BCL-XL and BCL-2 in a subset of hematopoietic cell lines, acute myeloid leukemia (AML) primary samples, and in vivo patient-derived xenograft AML models. We further demonstrated the senolytic activity of 753B, which enhanced the efficacy of chemotherapy by targeting chemotherapy-induced cellular senescence. These results provide a pre-clinical rationale for the utility of 753B in AML therapy, and suggest that 753B could produce an added therapeutic benefit by overcoming cellular senescence-induced chemoresistance when combined with chemotherapy.

Epichaperome inhibition targets TP53-mutant AML and AML stem/progenitor cells

TP 53-mutant acute myeloid leukemia (AML) remains the ultimate therapeutic challenge. Epichaperomes, formed in malignant cells, consist of heat shock protein 90 (HSP90) and associated proteins that support the maturation, activity, and stability of oncogenic kinases and transcription factors including mutant p53. High-throughput drug screening identified HSP90 inhibitors as top hits in isogenic TP53-wild-type (WT) and -mutant AML cells. We detected epichaperomes in AML cells and stem/progenitor cells with TP53 mutations but not in healthy bone marrow (BM) cells. Hence, we investigated the therapeutic potential of specifically targeting epichaperomes with PU-H71 in TP53-mutant AML based on its preferred binding to HSP90 within epichaperomes. PU-H71 effectively suppressed cell intrinsic stress responses and killed AML cells, primarily by inducing apoptosis; targeted TP53-mutant stem/progenitor cells; and prolonged survival of TP53-mutant AML xenograft and patient-derived xenograft models, but it had minimal effects on healthy human BM CD34+ cells or on murine hematopoiesis. PU-H71 decreased MCL-1 and multiple signal proteins, increased proapoptotic Bcl-2-like protein 11 levels, and synergized with BCL-2 inhibitor venetoclax in TP53-mutant AML. Notably, PU-H71 effectively killed TP53-WT and -mutant cells in isogenic TP53-WT/TP53-R248W Molm13 cell mixtures, whereas MDM2 or BCL-2 inhibition only reduced TP53-WT but favored the outgrowth of TP53-mutant cells. Venetoclax enhanced the killing of both TP53-WT and -mutant cells by PU-H71 in a xenograft model. Our data suggest that epichaperome function is essential for TP53-mutant AML growth and survival and that its inhibition targets mutant AML and stem/progenitor cells, enhances venetoclax activity, and prevents the outgrowth of venetoclax-resistant TP53-mutant AML clones. These concepts warrant clinical evaluation.

ABCC1 and glutathione metabolism limit the efficacy of BCL-2 inhibitors in acute myeloid leukemia

The BCL-2 inhibitor Venetoclax is a promising agent for the treatment of acute myeloid leukemia (AML). However, many patients are refractory to Venetoclax, and resistance develops quickly. ATP-binding cassette (ABC) transporters mediate chemotherapy resistance but their role in modulating the activity of targeted small-molecule inhibitors is unclear. Using CRISPR/Cas9 screening, we find that loss of ABCC1 strongly increases the sensitivity of AML cells to Venetoclax. Genetic and pharmacologic ABCC1 inactivation potentiates the anti-leukemic effects of BCL-2 inhibitors and efficiently re-sensitizes Venetoclax-resistant leukemia cells. Conversely, ABCC1 overexpression induces resistance to BCL-2 inhibitors by reducing intracellular drug levels, and high ABCC1 levels predicts poor response to Venetoclax therapy in patients. Consistent with ABCC1-specific export of glutathionylated substrates, inhibition of glutathione metabolism increases the potency of BCL-2 inhibitors. These results identify ABCC1 and glutathione metabolism as mechanisms limiting efficacy of BCL-2 inhibitors, which may pave the way to development of more effective therapies.

Inhibition of menin, BCL-2, and FLT3 combined with a hypomethylating agent cures NPM1/FLT3-ITD/-TKD mutant acute myeloid leukemia in a patient-derived xenograft model

Not available.

A phase 1/2 study of azacitidine, venetoclax and pevonedistat in newly diagnosed secondary AML and in MDS or CMML after failure of hypomethylating agents

BACKGROUND

Pevonedistat is a first-in-class, small molecular inhibitor of NEDD8-activating enzyme that has clinical activity in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). Preclinical data suggest synergy of pevonedistat with azacitidine and venetoclax.

METHODS

This single-center, phase 1/2 study evaluated the combination of azacitidine, venetoclax and pevonedistat in older adults with newly diagnosed secondary AML or with MDS or chronic myelomonocytic leukemia (CMML) after failure of hypomethylating agents. Patients received azacitidine 75 mg/m2 IV on days 1-7, venetoclax at maximum dose of 200-400 mg orally on days 1-21 (AML cohort) or days 1-14 (MDS/CMML cohort) and pevonedistat 20 mg/m2 IV on days 1, 3 and 5 for up to 24 cycles. The primary endpoints for the phase 2 portion of the study were the CR/CRi rate in the AML cohort and the overall response rate (CR + mCR + PR + HI) in the MDS/CMML cohort.

FINDINGS

Forty patients were enrolled (32 with AML and 8 with MDS/CMML). In the AML cohort, the median age was 74 years (range 61-86 years), and 27 patients (84%) had at least one adverse risk cyto-molecular feature, including 15 (47%) with a TP53 mutation or MECOM rearrangement; seventeen patients (53%) had received prior therapy for a preceding myeloid disorder. The CR/CRi rate was 66% (CR 50%; CRi 16%), and the median overall survival (OS) was 8.1 months. In the MDS/CMML cohort, 7 patients (87%) were high or very high risk by the IPSS-R. The overall response rate was 75% (CR 13%; mCR with or without HI 50%; HI 13%). The most common grade 3-4 adverse events were infection in 16 patients (35%), febrile neutropenia in 10 patients (25%) and hypophosphatemia in 9 patients (23%). In an exploratory analysis, early upregulation of NOXA expression was observed, with subsequent decrease in MCL-1 and FLIP, findings consistent with preclinical mechanistic studies of pevonedistat. Upregulation of CD36 was observed, which may have contributed to therapeutic resistance.

CONCLUSIONS

The triplet combination of azacitidine, venetoclax and pevonedistat shows encouraging activity in this very poor-risk population of patients with AML, MDS or CMML. Trial registration ClinicalTrials.gov (NCT03862157).

Mitophagy Promotes Resistance to BH3 Mimetics in Acute Myeloid Leukemia

BH3 mimetics are used as an efficient strategy to induce cell death in several blood malignancies, including acute myeloid leukemia (AML). Venetoclax, a potent BCL-2 antagonist, is used clinically in combination with hypomethylating agents for the treatment of AML. Moreover, MCL1 or dual BCL-2/BCL-xL antagonists are under investigation. Yet, resistance to single or combinatorial BH3-mimetic therapies eventually ensues. Integration of multiple genome-wide CRISPR/Cas9 screens revealed that loss of mitophagy modulators sensitizes AML cells to various BH3 mimetics targeting different BCL-2 family members. One such regulator is MFN2, whose protein levels positively correlate with drug resistance in patients with AML. MFN2 overexpression is sufficient to drive resistance to BH3 mimetics in AML. Insensitivity to BH3 mimetics is accompanied by enhanced mitochondria-endoplasmic reticulum interactions and augmented mitophagy flux, which acts as a prosurvival mechanism to eliminate mitochondrial damage. Genetic or pharmacologic MFN2 targeting synergizes with BH3 mimetics by impairing mitochondrial clearance and enhancing apoptosis in AML.

SIGNIFICANCE

AML remains one of the most difficult-to-treat blood cancers. BH3 mimetics represent a promising therapeutic approach to eliminate AML blasts by activating the apoptotic pathway. Enhanced mitochondrial clearance drives resistance to BH3 mimetics and predicts poor prognosis. Reverting excessive mitophagy can halt BH3-mimetic resistance in AML. This article is highlighted in the In This Issue feature, p. 1501.

Determination of Radiation Exposure of Individuals in the Population by Patients after Radioiodine Therapy - Comparison of two Measurement Systems

According to the requirements of radiation protection legislation, patients may only be discharged from the nuclear medicine therapy ward if it is ensured that the cumulative radiation exposure of the population is below 1 mSv per year. In the present study, dose measurements of patients after radioiodine therapy (RIT) and their relatives are to be used to prove that the radiation exposure resulting from the medical application is low and that the legal framework conditions are complied with. Furthermore, the results allow conclusions to be drawn about the measurement accuracy of the dosimeters used.

METHODS

In 147 patients after RIT and their relatives, the dosage was measured over 14 days with different measuring systems. Finger ring dosimeters (FRD) were worn during the whole day, furthermore the dose was determined by non-official OSL and TLD dosimeters during the sleep phase.

RESULTS

88 data sets were used for the final analysis. With the FRD, dose values between 0.1-50 mSv were determined for the patients. As expected, the finger ring dose of the relatives was significantly lower, averaging 0.75 mSv compared to 10 mSv for the patient. For the TLD and OSL used in the sleep phase, the measured values were in the same range. The reproducibility of the measurement results was significantly better for the OSL than for the TLD.

CONCLUSION

Despite method-related measurement uncertainties, it can be concluded that the exposure dose of patients' relatives after radioiodine therapy is low and that the legal requirements are met. Moreover, the now official OSL dosimeters represent a more accurate and for the chosen measurement task better suited measurement system than the TLD.

KEY POINTS

· The exposure dose of patients' relatives after radioiodine therapy is low.. · The requirements of radiation protection legislation after discharge from the nuclear medicine therapy ward are complied with. · OSL dosimeters are a accurate and for the measurement task suited system.

CITATION FORMAT

· Hartmann H, Andreeff M, Claußnitzer J et al. Determination of Radiation Exposure of Individuals in the Population by Patients after Radioiodine Therapy - Comparison of two Measurement Systems. Fortschr Röntgenstr 2023; 195: 605 - 612.

A Phase I study of Milademetan (DS3032b) in combination with low dose cytarabine with or without venetoclax in acute myeloid leukemia: Clinical safety, efficacy, and correlative analysis

In TP53 wild-type acute myeloid leukemia (AML), inhibition of MDM2 can enhance p53 protein expression and potentiate leukemic cell apoptosis. MDM2 inhibitor (MDM2i) monotherapy in AML has shown modest responses in clinical trials but combining options of MDM2i with other potent AML-directed agents like cytarabine and venetoclax could improve its efficacy. We conducted a phase I clinical trial (NCT03634228) to study the safety and efficacy of milademetan (an MDM2i) with low-dose cytarabine (LDAC)±venetoclax in adult patients with relapsed refractory (R/R) or newly diagnosed (ND; unfit) TP53 wild-type AML and performed comprehensive CyTOF analyses to interrogate multiple signaling pathways, the p53-MDM2 axis and the interplay between pro/anti-apoptotic molecules to identify factors that determine response and resistance to therapy. Sixteen patients (14 R/R, 2 N/D treated secondary AML) at a median age of 70 years (range, 23-80 years) were treated in this trial. Two patients (13%) achieved an overall response (complete remission with incomplete hematological recovery). Median cycles on trial were 1 (range 1-7) and at a median follow-up of 11 months, no patients remained on active therapy. Gastrointestinal toxicity was significant and dose-limiting (50% of patients ≥ grade 3). Single-cell proteomic analysis of the leukemia compartment revealed therapy-induced proteomic alterations and potential mechanisms of adaptive response to the MDM2i combination. The response was associated with immune cell abundance and induced the proteomic profiles of leukemia cells to disrupt survival pathways and significantly reduced MCL1 and YTHDF2 to potentiate leukemic cell death. The combination of milademetan, LDAC±venetoclax led to only modest responses with recognizable gastrointestinal toxicity. Treatment-induced reduction of MCL1 and YTHDF2 in an immune-rich milieu correlate with treatment response.

Mdm2/p53 levels in bone marrow mesenchymal stromal cells are essential for maintaining the hematopoietic niche in response to DNA damage

Mesenchymal stromal cells (MSCs) are a key component of the bone marrow (BM) niche, providing essential support required for the maintenance of hematopoietic stem cells. To advance our understanding of physiological functions of p53 and Mdm2 in BM-MSCs, we developed traceable conditional mouse models targeting Mdm2 and/or Trp53 in vivo. We demonstrate that Mdm2 is essential for the emergence, maintenance, and hematopoietic support of BM-MSCs. Mdm2 haploinsufficiency in BM-MSCs resulted in genotoxic stress-associated thrombocytopenia, suggesting a functional role for Mdm2 in hematopoiesis. In a syngeneic mouse model of acute myeloid leukemia (AML), Trp53 deletion in BM-MSCs improved survival, and protected BM against hematopoietic toxicity from a murine Mdm2i, DS-5272. The transcriptional changes were associated with dysregulation of glycolysis, gluconeogenesis, and Hif-1α in BM-MSCs. Our results reveal a physiologic function of Mdm2 in BM-MSC, identify a previously unknown role of p53 pathway in BM-MSC-mediated support in AML and expand our understanding of the mechanism of hematopoietic toxicity of MDM2is.

Targeting Unc51-like Autophagy Activating Kinase 1 (ULK1) Overcomes Adaptive Drug Resistance in Acute Myelogenous Leukemia

Despite effective new therapies, adaptive resistance remains the main obstacle in acute myelogenous leukemia (AML) therapy. Autophagy induction is a key mechanism for adaptive resistance. Leukemic blasts at diagnosis express higher levels of the apical autophagy kinase ULK1 compared with normal hematopoietic cells. Exposure to chemotherapy and targeted agents upregulate ULK1, hence we hypothesize that developing ULK1 inhibitors may present the unique opportunity for clinical translation of autophagy inhibition. Accordingly, we demonstrate that ULK1 inhibition, by genetic and pharmacologic means, suppresses treatment-induced autophagy, overcomes adaptive drug-resistance, and synergizes with chemotherapy and emerging antileukemia agents like venetoclax (ABT-199). The study next aims at exploring the underlying mechanisms. Mechanistically, ULK1 inhibition downregulates MCL1 antiapoptotic gene, impairs mitochondrial function and downregulates components of the CD44-xCT system, resulting in impaired reactive oxygen species (ROS) mitigation, DNA damage, and apoptosis. For further validation, several mouse models of AML were generated. In these mouse models, ULK1 deficiency impaired leukemic cell homing and engraftment, delayed disease progression, and improved survival. Therefore, in the study, we validated our hypothesis and identified ULK1 as an important mediator of adaptive resistance to therapy and an ideal candidate for combination therapy in AML. Therefore, we propose ULK1 inhibition as a therapeutically relevant treatment option to overcome adaptive drug-resistance in AML.

IMPLICATIONS

ULK1 drives a cell-intrinsic adaptive resistance in AML and targeting ULK1-mediated autophagy can synergize with existing and emerging AML therapies to overcome drug-resistance and induce apoptosis.

Combined inhibition of BCL-2 and MCL-1 overcomes BAX deficiency-mediated resistance of TP53-mutant acute myeloid leukemia to individual BH3 mimetics

TP53-mutant acute myeloid leukemia (AML) respond poorly to currently available treatments, including venetoclax-based drug combinations and pose a major therapeutic challenge. Analyses of RNA sequencing and reverse phase protein array datasets revealed significantly lower BAX RNA and protein levels in TP53-mutant compared to TP53-wild-type (WT) AML, a finding confirmed in isogenic CRISPR-generated TP53-knockout and -mutant AML. The response to either BCL-2 (venetoclax) or MCL-1 (AMG176) inhibition was BAX-dependent and much reduced in TP53-mutant compared to TP53-WT cells, while the combination of two BH3 mimetics effectively activated BAX, circumventing survival mechanisms in cells treated with either BH3 mimetic, and synergistically induced cell death in TP53-mutant AML and stem/progenitor cells. The BH3 mimetic-driven stress response and cell death patterns after dual inhibition were largely independent of TP53 status and affected by apoptosis induction. Co-targeting, but not individual targeting of BCL-2 and MCL-1 in mice xenografted with TP53-WT and TP53-R248W Molm13 cells suppressed both TP53-WT and TP53-mutant cell growth and significantly prolonged survival. Our results demonstrate that co-targeting BCL-2 and MCL-1 overcomes BAX deficiency-mediated resistance to individual BH3 mimetics in TP53-mutant cells, thus shifting cell fate from survival to death in TP53-deficient and -mutant AML. This concept warrants clinical evaluation.

Molecular Mechanisms of Ferroptosis and Updates of Ferroptosis Studies in Cancers and Leukemia

Ferroptosis is a mode of cell death regulated by iron-dependent lipid peroxidation. Growing evidence suggests ferroptosis induction as a novel anti-cancer modality that could potentially overcome therapy resistance in cancers. The molecular mechanisms involved in the regulation of ferroptosis are complex and highly dependent on context. Therefore, a comprehensive understanding of its execution and protection machinery in each tumor type is necessary for the implementation of this unique cell death mode to target individual cancers. Since most of the current evidence for ferroptosis regulation mechanisms is based on solid cancer studies, the knowledge of ferroptosis with regard to leukemia is largely lacking. In this review, we summarize the current understanding of ferroptosis-regulating mechanisms with respect to the metabolism of phospholipids and iron as well as major anti-oxidative pathways that protect cells from ferroptosis. We also highlight the diverse impact of p53, a master regulator of cell death and cellular metabolic processes, on the regulation of ferroptosis. Lastly, we discuss recent ferroptosis studies in leukemia and provide a future perspective for the development of promising anti-leukemia therapies implementing ferroptosis induction.

Clinical outcomes associated with NPM1 mutations in patients with relapsed or refractory AML

Mutations in Nucleophosmin 1 (NPM1) are associated with a favorable prognosis in newly diagnosed acute myeloid leukemia (AML), however, their prognostic impact in relapsed/refractory (R/R) settings are unknown. In a retrospective analysis, we identified 206 patients (12%) with mutated NPM1 (NPM1c) and compared their outcomes to 1516 patients (88%) with NPM1 wild-type (NPM1wt). NPM1c was associated with higher rates of complete remission or complete remission with incomplete count recovery compared with NPM1wt following each line of salvage therapy (first salvage, 56% vs 37%; P < .0001; second salvage, 33% vs 22%; P = .02; third salvage, 24% vs 14%; P = .02). However, NPM1 mutations had no impact on relapse-free survival (RFS) and overall survival (OS) with each salvage therapy with a median OS following salvage 1, 2 or 3 therapies in NPM1c vs NPM1wt of 7.8 vs 6.0; 5.3 vs 4.1; and 3.5 vs 3.6 months, respectively. Notably, the addition of venetoclax to salvage regimens in patients with NPM1c improved RFS and OS (median RFS, 15.8 vs 4.6 months; P = .05; median OS, 14.7 vs 5.9 months; P = .02). In conclusion, NPM1 mutational status has a minimal impact on prognosis in relapsed or refractory AML; therefore, novel treatment strategies are required to improve outcomes in this entity.

Venetoclax and idasanutlin in relapsed/refractory AML: a nonrandomized, open-label phase 1b trial

This phase 1b trial (NCT02670044) evaluated venetoclax-idasanutlin in patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) ineligible for cytotoxic chemotherapy. Two-dimensional dose escalation (DE, n = 50) was performed for venetoclax daily with idasanutlin on days 1 to 5 in 28-day cycles, followed by dosing schedule optimization (n = 6) to evaluate reduced venetoclax schedules (21-/14-day dosing). Common adverse events (occurring in ≥40% of patients) included diarrhea (87.3% of patients), nausea (74.5%), vomiting (52.7%), hypokalemia (50.9%), and febrile neutropenia (45.5%). During DE, across all doses, composite complete remission (CRc; CR + CR with incomplete blood count recovery + CR with incomplete platelet count recovery) rate was 26.0% and morphologic leukemia-free state (MLFS) rate was 12%. For anticipated recommended phase 2 doses (venetoclax 600 mg + idasanutlin 150 mg; venetoclax 600 mg + idasanutlin 200 mg), the combined CRc rate was 34.3% and the MLFS rate was 14.3%. Pretreatment IDH1/2 and RUNX1 mutations were associated with higher CRc rates (50.0% and 45.0%, respectively). CRc rate in patients with TP53 mutations was 20.0%, with responses noted among those with co-occurring IDH and RUNX1 mutations. In 12 out of 36 evaluable patients, 25 emergent TP53 mutations were observed; 22 were present at baseline with low TP53 variant allele frequency (median 0.0095% [range, 0.0006-0.4]). Venetoclax-idasanutlin showed manageable safety and encouraging efficacy in unfit patients with R/R AML. IDH1/2 and RUNX1 mutations were associated with venetoclax-idasanutlin sensitivity, even in some patients with co-occurring TP53 mutations; most emergent TP53 clones were preexisting. Our findings will aid ongoing/future trials of BCL-2/MDM2 inhibitor combinations. This trial was registered at www.clinicaltrials.gov as #NCT02670044.

Early mortality in acute myeloid leukemia with KMT2A rearrangement is associated with high risk of bleeding and disseminated intravascular coagulation

BACKGROUND

Acute myeloid leukemia (AML) with rearrangement of lysine methyltransferase 2a gene (KMT2Ar) is characterized by chemotherapy resistance and high rates of relapse. However, additional causes of treatment failure or early mortality have not been well-defined in this entity.

METHODS

In a retrospective analysis, causes and rates of early mortality following induction treatment were compared between a cohort of adults with KMT2Ar AML (N = 172) and an age-matched cohort of patients with normal karyotype AML (N = 522).

RESULTS

The 60-day mortality in patients with KMT2Ar AML was 15% compared with 7% with normal karyotype (p = .04). We found a significantly higher occurrence of major bleeding events (p = .005) and total bleeding events (p = .001) in KMT2Ar AML compared with diploid AML. Among evaluable patients with KMT2Ar AML, 93% exhibited overt disseminated intravascular coagulopathy compared with 54% of patients with a normal karyotype before death (p = .03). In a multivariate analysis, KMT2Ar and a monocytic phenotypic were the only independent predictors of any bleeding event in patients who died within 60 days (odds ratio, 3.5; 95% CI, 1.4-10.4; p = .03; odds ratio, 3.2; 95% CI, 1-1-9.4; p = .04, respectively).

CONCLUSION

In conclusion, early recognition and aggressive management of disseminated intravascular coagulopathy and coagulopathy are important considerations that could mitigate the risk of death during induction treatment in KMT2Ar AML.

PLAIN LANGUAGE SUMMARY

Acute myeloid leukemia (AML) with rearrangement of KMT2A is characterized by chemotherapy resistance and high rates of relapse. However, additional causes of treatment failure or early mortality have not been well-defined in this entity. In this article, that KMT2A-rearranged AML is demonstrably associated with higher early mortality and an increased risk of bleeding and coagulopathy, specifically, disseminated intravascular coagulation, compared with normal karyotype AML. These findings emphasize the importance of monitoring and mitigating coagulopathy in KMT2A-rearranged leukemia similar to what is done in acute promyelocytic leukemia.

Mdm2/p53 levels in bone marrow mesenchymal stromal cells is essential for maintaining the hematopoietic niche in response to DNA damage

Mesenchymal stromal cells (MSCs) are a key component of the bone marrow (BM) niche, providing essential support required for maintenance of hematopoietic stem cells. To advance our understanding of physiological functions of p53 and Mdm2 in BM-MSCs, we developed traceable conditional mouse models targeting Mdm2 and/or Trp53 in vivo . We demonstrate that Mdm2 is essential for the emergence, maintenance and hematopoietic support of BM-MSCs. Mdm2 haploinsufficiency in BM-MSCs resulted in genotoxic stress-associated thrombocytopenia, suggesting a functional role for Mdm2 in hematopoiesis. In a syngeneic mouse model of acute myeloid leukemia (AML), Trp53 deletion in BM-MSCs improved survival, and protected BM against hematopoietic toxicity from a murine Mdm2i, DS-5272. The transcriptional changes were associated with dysregulation of glycolysis, gluconeogenesis, and Hif-1α in BM-MSCs. Our results reveal a physiologic function of Mdm2 in BM-MSC, identify a previously unknown role of p53 pathway in BM-MSC-mediated support in AML and expand our understanding of the mechanism of hematopoietic toxicity of MDM2is.

The multi-kinase inhibitor CG-806 exerts anti-cancer activity against acute myeloid leukemia by co-targeting FLT3, BTK, and Aurora kinases

Background

Despite the development of several FLT3 inhibitors that have improved outcomes in patients with FLT3-mutant acute myeloid leukemias (AML), drug resistance is frequently observed, which may be associated with the activation of additional pro-survival pathways such as those regulated by BTK, aurora kinases, and potentially others in addition to acquired tyrosine kinase domains (TKD) mutations of FLT3 gene. FLT3may not always be a driver mutation.

Objective

To evaluate the anti-leukemia efficacy of the novel multi-kinase inhibitor CG-806, which targets FLT3 and other kinases, in order to circumvent drug resistance and target FLT3 wild-type (WT) cells.

Methods

The anti-leukemia activity of CG-806 was investigated by measuring apoptosis induction and analyzing cell cycle with flow cytometry in vitro, and its anti-leukemia.

Results

CG-806 demonstrated superior anti-leukemia efficacy compared to commercially available FLT3 inhibitors, both in vitro and in vivo, regardless of FLT3 mutational status. The mechanism of action of CG-806 may involve its broad inhibitory profile of FLT3, BTK, and aurora kinases. InFLT3 mutant cells, CG-806 induced G1 phase blockage, while in FLT3WT cells, it resulted in G2/M arrest. Targeting FLT3 and Bcl-2 and/or Mcl-1 simultaneously resulted in a synergistic pro-apoptotic effect in FLT3mutant leukemia cells.

Conclusion

The results of this study suggest that CG-806 is a promising multi-kinase inhibitor with anti-leukemia efficacy, regardless of FLT3 mutational status. A phase 1 clinical trial of CG-806 for the treatment of AML has been initiated (NCT04477291).

Clinical and molecular profiling of AML patients with chromosome 7 or 7q deletions in the context of TP53 alterations and venetoclax treatment

Deletions in chromosome 7 (del(7)) or its long arm (del(7q)) constitute the most common adverse cytogenetic events in acute myeloid leukemia (AML). We retrospectively analyzed 243 treatment-naive patients with AML and del(7) (168/243; 69%) or del(7q) (75/243; 31%) who did not receive any myeloid-directed therapy prior to AML diagnosis. This is the largest comprehensive clinical and molecular analysis of AML patients with del(7) and del(7q). Our results show that relapse-free survival was significantly longer for AML patients with del(7q) compared to del(7), but the overall survival and remission duration were similar. TP53 mutations and del5/5q were the most frequent co-occurring mutations and cytogenetic abnormalities, and conferred worse outcomes in del(7) and del(7q) patients. Venetoclax-based treatments were associated with worse outcomes in TP53 mutated AML patients with del(7) or del(7q), as well as del(7) with TP53 wildtype status, requiring further investigation.

Phase II Study of Venetoclax Added to Cladribine Plus Low-Dose Cytarabine Alternating With 5-Azacitidine in Older Patients With Newly Diagnosed Acute Myeloid Leukemia

PURPOSE

The combination of venetoclax and 5-azacitidine (5-AZA) for older or unfit patients with acute myeloid leukemia (AML) improves remission rates and survival compared with 5-AZA alone. We hypothesized that the addition of venetoclax to cladribine (CLAD)/low-dose araC (low-dose cytarabine [LDAC]) alternating with 5-AZA backbone may further improve outcomes for older patients with newly diagnosed AML.

METHODS

This is a phase II study investigating the combination of venetoclax and CLAD/LDAC alternating with venetoclax and 5-AZA in older (≥ 60 years) or unfit patients with newly diagnosed AML. The primary objective was composite complete response (CR) rate (CR plus CR with incomplete blood count recovery); secondary end points were overall survival, disease-free survival (DFS), overall response rate, and toxicity.

RESULTS

A total of 60 patients were treated; median age was 68 years (range, 57-84 years). By European LeukemiaNet, 23%, 33%, and 43% were favorable, intermediate, and adverse risk, respectively. Fifty-six of 60 evaluable patients responded (composite CR: 93%) and 84% were negative for measurable residual disease. There was one death (2%) within 4 weeks. With a median follow-up of 22.1 months, the median overall survival and DFS have not yet been reached. The most frequent grade 3/4 nonhematologic adverse events were febrile neutropenia (n = 33) and pneumonia (n = 14). One patient developed grade 4 tumor lysis syndrome.

CONCLUSION

Venetoclax and CLAD/LDAC alternating with venetoclax and 5-AZA is an effective regimen among older or unfit patients with newly diagnosed AML. The rates of overall survival and DFS are encouraging. Further study of this non-anthracycline-containing backbone in younger patients, unfit for intensive chemotherapy, as well as comparisons to standard frontline therapies is warranted.

Concomitant targeting of FLT3 and BTK overcomes FLT3 inhibitor resistance in acute myeloid leukemia through inhibition of autophagy

Strategies to overcome resistance to FMS-like tyrosine kinase 3 (FLT3)-targeted therapy in acute myeloid leukemia (AML) are urgently needed. We identify autophagy as one of the resistance mechanisms, induced by hypoxia and the bone marrow (BM) microenvironment via Bruton's tyrosine kinase (BTK) activation. Suppressing autophagy/BTK sensitized FLT3-mutated AML to FLT3 inhibitor-induced apoptosis. Further, co-targeting FLT3/BTK/Aurora kinases (AURKs) with a novel multi-kinase inhibitor CG-806 (luxeptinib) induced profound apoptosis induction in FLT3-mutated AML by co-suppressing FLT3/BTK, antagonizing autophagy, and causing leukemia cell death in FLT3 wild-type AML by AURK-mediated G2/M arrest and polyploidy, in addition to FLT3 inhibition. Thus, CG-806 exerted profound anti-leukemia activity against AMLs regardless of FLT3 mutation status. CG-806 further significantly reduced AML burden and extended survival in an in vivo PDX leukemia murine model of FLT3 inhibitorresistant FLT3-ITD/TKD double mutant primary AML. Taken together, CG-806 exerts a unique mechanistic action and pre-clinical activity, suggesting further development in FLT3 wild-type and mutant AML.

Azacitidine plus venetoclax in patients with high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia: phase 1 results of a single-centre, dose-escalation, dose-expansion, phase 1-2 study

BACKGROUND

Therapies beyond hypomethylating agents such as azacitidine are needed in high-risk myelodysplastic syndromes. Venetoclax is an orally bioavailable small molecule BCL-2 inhibitor that is synergistic with hypomethylating agents. We therefore aimed to evaluate the safety, tolerability, and preliminary activity of azacitidine combined with venetoclax for treatment-naive and relapsed or refractory high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia.

METHODS

We did a single centre, dose-escalation, dose-expansion, phase 1-2 trial at the University of Texas MD Anderson Cancer Center (Houston, TX, USA). This Article details the phase 1 results. We enrolled patients (≥18 years) with treatment-naive or relapsed or refractory high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia and bone marrow blasts of more than 5%. No specific Eastern Cooperative Oncology Group status restriction was used. Patients were treated with intravenous or subcutaneous azacitidine (75 mg/m²) for 5 days and oral venetoclax (100-400 mg) for 7-14 days. The primary outcome was safety and tolerability as well as determination of the maximum tolerated dose and recommended phase 2 dose of the azacitidine and venetoclax combination using a 3 + 3 study design. All patients who received one dose of study drug were included in the analyses. This study is registered with ClinicalTrials.gov, number NCT04160052. The phase 2 dose-expansion part of the trial is ongoing.

FINDINGS

Between Nov 12, 2019, and Dec 17, 2021, a total of 23 patients were enrolled in the phase 1 portion of this study (17 [74%] hypomethylating agent naive and six [26%] post-hypomethylating agent failure). 18 (78%) patients were male and five (22%) were female; 21 (91%) were white and two (9%) were Asian. Median follow-up was 13·2 months (IQR 6·8-18·3). The maximum tolerated dose was not reached and the recommended phase 2 dose was established as azacitidine 75 mg/m² for 5 days plus venetoclax 400 mg for 14 days. The most common grade 3-4 treatment-emergent adverse events were neutropenia (nine [39%] of 23), thrombocytopenia (nine [39%]), lung infection (seven [30%]), and febrile neutropenia (four [17%]). Three deaths due to sepsis, which were not deemed treatment-related, occurred on the study drugs. The overall response rate was 87% (95% CI 66-97; 20 of 23 patients).

INTERPRETATION

Azacitidine with venetoclax is safe and shows encouraging activity in patients with high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia.

FUNDING

MD Anderson Cancer Center.

A phase two study of high dose blinatumomab in Richter's syndrome

Richter's Syndrome (RS) is an aggressive transformation of CLL, usually clonally-related diffuse large B-cell lymphoma (DLBCL), characterized by frequent TP53 mutations, intrinsic chemoresistance and poor survival. TP53-independent treatments are needed. We conducted a single center, phase 2, investigator-initiated study of high dose blinatumomab (maximum 112 mcg/d after initial, weekly dose escalation), NCT03121534, given for an 8-week induction and 4-week consolidation cycle. Responses were assessed by Lugano 2014 criteria. Serial multi-parameter flow cytometry from blood was performed to identify patient-specific biomarkers for response. Nine patients were treated. Patients had received a median of 4 and 2 prior therapies for CLL and RS, respectively. Five of 9 had del(17p) and 100% had complex karyotype. Four patients had reduction in nodal disease, including one durable complete response lasting >1 y. Treatment was well tolerated, with no grade >3 cytokine release syndrome and 1 case of grade 3, reversible neurotoxicity. Immunophenotyping demonstrated the majority of patients expressed multiple immune checkpoints, especially PD1, TIM3 and TIGIT. The patient who achieved CR had the lowest levels of immune checkpoint expression. Simultaneous targeting with immune checkpoint blockade, especially PD1 inhibition, which has already demonstrated single-agent efficacy in RS, could achieve synergistic killing and enhance outcomes.

Abstract 5337: Tolinapant (ASTX660) enhances the anti-leukemic activity of Venetoclax and Dexamethasone in T cell acute lymphoblastic leukemia (T-ALL)

Background: Inhibitors of apoptosis proteins (IAPs) are overexpressed in ALL leading to resistance to apoptosis and chemo-resistance. Tolinapant, a non-peptidomimetic antagonist of the cellular and X-linked inhibitors of apoptosis (cIAP1/2 and XIAP) being evaluated in Phase 1/2 clinical trial [NCT02503423] showed single-agent activity in T-cell lymphoma. Objectives: Herein, we analyzed the preclinical activity of tolinapant in combination with ABT199 and Dexamethasone (DEX) in T-ALL (in vitro and ex-vivo patient derived xenografts (PDX).

Results: Using a panel of 8 T-ALL cell lines we analyzed the single agent activity of tolinapant. Loucy and SUP-T11 were most sensitive (IC50 = 190-309 nM). CCRF-CEM and ALL-SIL showed moderate sensitivity (IC50 = 10-18 µM) while Jurkat, MOLT16, MOLT4 and PF382 were resistant. Western blotting (WB) showed decreased levels of cIAP1and cIAP2 with no change in XIAP in response to tolinapant as a single agent. We next investigated the efficacy of tolinapant with Bcl2 inhibitor ABT199. The combination of ABT199 and ASTX660 was synergistic in Loucy cell line with combination index (CI) of 0.14. Cell death was increased to 64±3% in combination v/s 27±0.9% in ABT199. WB showed decreased cIAP2 and increased levels of cleaved caspase 7 and cleaved caspase 9 in combination compared to single agents, suggesting increased apoptosis. Treatment of PDX-derived cells with tolinapant and ABT199 was more effective than monotherapy in inducing apoptosis in CD45+ bulk (46±0.7% to 63±6%, p&lt;0.0001) and leukemia initiating cells (LICs, CD45+ CD7+ CD19- CD34+) (39±3% to 54±8%, p=0.003). Next, we checked the effect of combination of DEX with tolinapant in T-ALL cell lines. CCRF-CEM cell line is from a relapsed patient and is resistant to DEX. The combination was synergistic with CI of 0.26 and cell death of 50±4% compared to 20±3% by DEX. A triple combination of DEX, ABT199 and tolinapant increased apoptotic response to 82.9±1%, compared to DEX+ABT199 dual combination where apoptosis was induced to 52.4±2%. Strong synergy in terms of both cytoreduction as well as apoptosis induction was observed in SUP-T11 cells. Tolinapant sensitized SUP-T11 cells to DEX with ED50 value of 542 nM in combination compared to ~2 µM with DEX treatment. Simultaneous analysis of cell proliferation, stress response and DNA damage using single-cell proteomics analysis showed downregulation of proliferation (Ki-67), stress response (ATF4, LC3B) and increased levels of cleaved PARP, cleaved caspase 3 suggesting increased apoptosis in combination of tolinapant with DEX. Treatment of PDX-derived cells with tolinapant enhanced the cytotoxic effect of DEX in CD45+ bulk (58±2% to 71±0.1%, p&lt;0.0001) and LICs (62±2% to 78±0.9%, p&lt;0.0001).

Conclusion: Tolinapant synergizes with the anti-leukemic activity of ABT199 and DEX, establishing a therapeutic rationale for IAP antagonist in T-ALL.

Citation Format: Priyanka Sharma, Sujan Piya, Huaxian Ma, Natalia Baran, Muharrem Muftuoglu, Mahesh Basyal, Vivian Ruvolo, George Ward, Tomoko Smyth, Martin J. Sims, Michael Andreeff, Gautam Borthakur. Tolinapant (ASTX660) enhances the anti-leukemic activity of Venetoclax and Dexamethasone in T cell acute lymphoblastic leukemia (T-ALL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5337.

Abstract 5479: Discovery and evaluation of GT19630, a c-Myc/GSPT1 cereblon E3 ligase modulator (CELMoD), for targeting Myc-driven blood cancers and small cell lung cancers (SCLC)

c-Myc is an oncogenic transcriptional factor driving tumor initiation, progression and poor prognosis in 80% of all tumor types, especially in B-cell malignancies and small cell lung cancer (SCLC) with Myc genomic alterations. Myc dysregulation have been directly linked to the poor clinical outcome in these cancers. Therefore, it is highly warranted to discover and develop novel Myc therapeutical agents for targeting Myc driven cancers. Here we described GT19630, a GSPT1/Myc CELMoD. GT19630 was discovered through an SAR effort for c-Myc degrader by using c-Myc ELISA and Western blot assays in c-Myc driven HL60 AML cells. GT19630 selectively degraded c-Myc proteins in HL60 cells (IC50=1.5 nM) as compared to growth-factor regulated c-Myc erythroid progenitor cells (TF-1 cells) with IC50=52.5 nM. GT19630 also selectively inhibited HL60 cell proliferation (IC50= 0.33 nM), as compared to its IC50 (26.2 nM) in GM-CSF-TF-1 proliferation, as well as in bone marrow colony-forming cell assays (myeloid=40.2 nM), suggesting&gt;100X selectivity for HL60 cells over normal blood cells. Through the SAR for Myc degrader, GT19630 has been evolved as a leading molecule sharing chemical properties to CELMoDs. Therefore, this compound was further evaluated by proteomics and western blot, GT19630 was confirmed to selective degradation of CELMoD targets, GSPT1/GSPT2 (translation termination factor G1 to S phase transition proteins 1 and 2) with IC90&lt;1 nM and CK1 alpha (IC90&lt;10 nM), but not IKZF1/Ikaros. In silico modeling of GT19630 was performed in the DDB1−CRBN−CC-885−GSPT1 complex and confirmed the docking similarity with CELMoDs. Further, GT19630 inhibited the cell proliferation with IC50&lt;10 nM in 74% B-cell malignant cell lines (20/27) bearing deregulated c-Myc and in 79% of SCLC cell lines (4/19) carrying deregulated Myc (c-Myc, N-Myc or L-Myc) tested. Moreover, GT19630 completely degraded Myc proteins in AML, lymphoma and multiple myeloma (c-Myc) and SCLC (c-Myc and N-Myc) xenograft tumors at the lowest dose of 1.0 mg/kg and induced complete tumor regression (lowest dose=0.3 mg/kg) tested. Furthermore, this compound eradicated lymphoma cells in Daudi-induced liquid lymphoma mouse models. In addition, GT19630, as a potent GSPT1/Myc CELMoD, demonstrated an even-driven pharmacology in vivo and induced complete tumor regression with a dosing regimen of 3 day on/7 day off. Remarkably, GT19630 selectively degraded Myc proteins in HL60 and DMS114 SCLC xenograft tumors as compared to a much less potency at degrading c-Myc in rat spleen. Finally, GT19630 demonstrated favorable PK and safety profiles (an 8-fold safety therapeutic windows) with no effect on myeloid lineages in rats at the dose of 6 mg/kg for 14 days, indicating GT19630 lacks myelosuppression as reported for other CELMoDs. Currently, GT19630 has been advanced into IND enabling stage.

Citation Format: Liandong Ma, Youzhi Tong, Zhaohui Yang, Qianxiang Zhou, Hongha Yan, Ru Xu, Jie Chen, Jie Pan, Huiyuan Wang, Jiangwei Li, Dong Chen, Xiang Cai, Jie Qu, Yini Wang, Jun Qin, Yuki Nishida, Michael Andreeff, Qilnli Guo, Yuki Nishida, Michael Andreeff. Discovery and evaluation of GT19630, a c-Myc/GSPT1 cereblon E3 ligase modulator (CELMoD), for targeting Myc-driven blood cancers and small cell lung cancers (SCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5479.

Quizartinib (QUIZ) with decitabine (DAC) and venetoclax (VEN) is active in patients (pts) with FLT3-ITD mutated acute myeloid leukemia (AML): A phase I/II clinical trial

7036

Background: QUIZ, a potent 2nd generation FLT3 inhibitor (FLT3i) demonstrated synergy with VEN in AML cell lines and PDX models (Mali Haematologica 2020). We evaluated the safety and efficacy of DAC + VEN + QUIZ triplet in patients with newly diagnosed (ineligible for intensive induction chemotherapy) or relapsed/refractory (R/R; up to 5 prior chemotherapies) FLT3 ITD mutated AML. Methods: All pts received 10 days of DAC (20 mg/m2) in Cycle 1. Pts underwent day 14 bone marrow (BM) biopsy, and VEN (400 mg/day starting from day1) was put on hold in pts with BM blasts ≤ 5% or aplasia. Those with day14 BM blast >5% continued VEN for 21 days during cycle 1. In subsequent cycles, DAC was reduced to 5 days. QUIZ (30 or 40 mg/day) was administered daily continuously. Results: Overall, 28 pts were enrolled and evaluable at the time of this report. Of the 23 pts with R/R AML (median 3 [range 1-5] prior therapies, 78% with ≥1 prior FLT3i including prior gilteritinib (GILT) in 70%, and 39% had a prior ASCT), 78% achieved CRc (3 CR, 15 CRi) with 6/16 and 5/18 responders FLT3-PCR and multicolor flow cytometry (MFC) negative, respectively. Pts with RAS/MAPK mutations had the lowest response rates (Table). Interestingly, no emergent TKD mutations were noted at relapse after the triplet but 3/8 evaluable pts had emergent RAS/MAPK mutations. 60-day mortality rate was 5%. Of 5 patients with newly diagnosed AML (median age 69), all achieved CRc (2 CR, 3 CRi) with 4/5 and 2/4 responders FLT3-PCR and MFC negative, respectively. 60-day mortality was 0. 2 pts developed hematologic DLT with 40 mg/day QUIZ dose (grade 4 neutropenia with a <5% cellular BM lasting ≥42 days). Hence, QUIZ 30 mg/day dose was determined as RP2D for the triplet. Grade 3/4 non-hematologic toxicities included lung infections (42%) and neutropenic fever (30%). No QTcF prolongations >480 msec were noted. With a median follow-up (f/u) of 13 months, the median OS was 7.6 months in R/R cohort (1-year OS of 30%). 8/18 responding R/R pts (including 5/8 prior GILT exposed pts) underwent ASCT with a median OS of 19 vs 8 months in those who underwent ASCT versus not (p=0.26). Of the 5 frontline responding pts median OS was 14.5 months, 2 were alive in CR, 1 died in CR1 post-ASCT, 2 died due to relapsed disease at the last f/u. Conclusions: DAC + VEN + QUIZ is active in R/R FLT3-ITD mutated AML pts, with CRc rates of 78% and the median OS of 7.6 months. Interestingly, RAS/MAPK mutations but not emergent TKD mutations were associated with primary and secondary resistance to the triplet. Accrual continues, and updated clinical, NGS, and mass cytometry (CyTOF) data will be presented. Clinical trial information: NCT03661307. [Table: see text]

Acute myeloid leukemia with KMT2Ar and association with risk of bleeding and early mortality

7026

Background: Acute myeloid leukemia (AML) with rearrangement of KMT2A is characterized by chemotherapy resistance and high rates of relapse. However, additional causes of treatment failure or early mortality have not been well-defined in this entity. Methods: In a retrospective analysis, we compared causes and rates of early mortality following induction treatment between a cohort of adults with KMT2Ar AML (N=172) and an age-matched cohort of patients (pts) with normal karyotype (NK) AML (N=522). Results: The 30 and 60-day (60d) mortality in pts with KMT2Ar AML were significantly higher compared to those with NK AML, with rates of 10% (17/172 pts) and 15% (26/172 pts) in KMT2Ar AML vs 4% (20/522 pts) and 7% (38/522 pts) in NK AML, respectively ( P=0.004). Among those who died within 60d, the most common contributing cause in KMT2Ar was respiratory failure without a clear infectious etiology in 38% (10/26 pts) vs 11% (4/38 pts) in NK AML ( P=0.01). We found 42% (11/26 pts) with KMT2Ar AML who died within 60d were either diagnosed with or had high clinical suspicion for diffuse alveolar hemorrhage (DAH) that warranted empiric therapy vs 18% (7/38 pts) with NK AML ( P=0.05). Given the high occurrence of DAH in KMT2Ar AML, we set out to quantify bleeding events and recorded major and minor bleeds as defined by the International Society of Thrombosis and Haemostasis. We found 65% (17/26 pts) with KMT2Ar AML had at least one bleeding event vs 32% (12/38 pts) with NK AML ( P=0.01). There was a significantly higher frequent occurrence of major bleeds (rate ratio=6.22; P=0.005) and total bleeding events (rate ratio=4.5; P=0.001) in KMT2Ar AML vs NK AML. KMT2Ar was associated with disseminated intravascular coagulopathy (DIC), as 93% of evaluable pts (14/15 pts) vs 54% (7/13 pts) in NK AML had overt DIC before death. Longitudinal trajectories of DIC parameters of pts who died within 60d showed significantly higher prothrombin time levels ( P=0.008) in KMT2Ar. In a multivariate analysis, KMT2Ar and a monocytic phenotypic were the only independent predictors of any bleeding event in pts who died within 60d (OR 3.5, 95% CI 1.4-10.4, P=0.03; OR 3.2, 95% CI 1.1-9.4, P=0.04). Conclusions: KMT2Ar AML is associated with higher early mortality and an increased risk of bleeding and coagulopathy compared with NK AML. Early recognition and aggressive management of DIC and coagulopathy are important considerations that could mitigate the risk of death during induction treatment.[Table: see text]

Inhibition of mitochondrial complex I reverses NOTCH1-driven metabolic reprogramming in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is commonly driven by activating mutations in NOTCH1 that facilitate glutamine oxidation. Here we identify oxidative phosphorylation (OxPhos) as a critical pathway for leukemia cell survival and demonstrate a direct relationship between NOTCH1, elevated OxPhos gene expression, and acquired chemoresistance in pre-leukemic and leukemic models. Disrupting OxPhos with IACS-010759, an inhibitor of mitochondrial complex I, causes potent growth inhibition through induction of metabolic shut-down and redox imbalance in NOTCH1-mutated and less so in NOTCH1-wt T-ALL cells. Mechanistically, inhibition of OxPhos induces a metabolic reprogramming into glutaminolysis. We show that pharmacological blockade of OxPhos combined with inducible knock-down of glutaminase, the key glutamine enzyme, confers synthetic lethality in mice harboring NOTCH1-mutated T-ALL. We leverage on this synthetic lethal interaction to demonstrate that IACS-010759 in combination with chemotherapy containing L-asparaginase, an enzyme that uncovers the glutamine dependency of leukemic cells, causes reduced glutaminolysis and profound tumor reduction in pre-clinical models of human T-ALL. In summary, this metabolic dependency of T-ALL on OxPhos provides a rational therapeutic target.

Venetoclax combined with FLAG-IDA induction and consolidation in newly diagnosed acute myeloid leukemia

Multi-agent induction chemotherapy (IC) improves response rates in younger patients with acute myeloid leukemia (AML); however, relapse remains the principal cause of treatment failure. Improved induction regimens are needed. A prospective single-center phase Ib/II study evaluating fludarabine, cytarabine, G-CSF, and idarubicin combined with venetoclax (FLAG-IDA + VEN) in patients with newly diagnosed (ND) or relapsed/refractory AML. The primary efficacy endpoint was assessment of overall activity (overall response rate [ORR]: complete remission [CR] + CR with partial hematologic recovery [CRh] + CR with incomplete hematologic recovery [CRi] + morphologic leukemia free state + partial response). Secondary objectives included additional assessments of efficacy, overall survival (OS), and event-free survival (EFS). Results of the expanded ND cohort with additional follow-up are reported. Forty-five patients (median age: 44 years [range 20-65]) enrolled. ORR was 98% (N = 44/45; 95% credible interval 89.9%-99.7%). Eighty-nine percent (N = 40/45) of patients attained a composite CR (CRc + CRh + CRi) including 93% (N = 37/40) who were measurable residual disease (MRD) negative. Twenty-seven (60%) patients transitioned to allogeneic stem cell transplant (alloHSCT). Common non-hematologic adverse events included febrile neutropenia (44%; N = 20), pneumonia (22%, N = 10), bacteremia (18%, N = 8), and skin/soft tissue infections (44%, N = 20). After a median follow-up of 20 months, median EFS and OS were not reached. Estimated 24-month EFS and OS were 64% and 76%, respectively. FLAG-IDA + VEN is an active regimen in ND-AML capable of producing high MRD-negative remission rates and enabling transition to alloHSCT when appropriate in most patients. Toxicities were as expected with IC and were manageable. Estimated 24-month survival appears favorable compared to historical IC benchmarks.

Transgenic Expression of IL15 Retains CD123-Redirected T Cells in a Less Differentiated State Resulting in Improved Anti-AML Activity in Autologous AML PDX Models

Immunotherapy with T-cells expressing bispecific T-cell engagers (ENG T-cells) is a promising approach to improve the outcomes for patients with recurrent/refractory acute myeloid leukemia (AML). However, similar to T-cells expressing chimeric antigen receptors (CARs), their antitumor activity is limited in the setting of chronic antigen stimulation. We therefore set out to explore whether transgenic expression of IL15 improves the effector function of ENG T-cells targeting CD123-positive AML. T-cells expressing CD123-specific ENG (CD123-ENG) ± IL15 were generated by retroviral transduction from peripheral blood T cells from healthy donors or patients with AML. In this study, we characterized in detail the phenotype and effector functions of ENG T-cell populations in vitro and in vivo. IL15-expressing CD123-ENG (CD123-ENG.IL15) T-cells retained their antigen-specificity and effector function in the setting of chronic antigen exposure for more 30 days of coculture with AML blasts in contrast to CD123-ENG T-cells, whose effector function rapidly eroded. Furthermore, CD123-ENG.IL15 T-cells remained in a less differentiated state as judged by a high frequency of naïve/memory stem T-cell-like cells (CD45RA+CCR7+/CD45RO−CD62L+ cells) without evidence of T-cell exhaustion. Single cell cytokine profiling using IsoPlexis revealed enhanced T-cell polyfunctionality of CD123-ENG.IL15 T-cells as judged by effector cytokine production, including, granzyme B, IFN-γ, MIP-1α, perforin, TNF-α, and TNF-β. In vivo, CD123-ENG.IL15 T-cells exhibited superior antigen-specific anti-AML activity and T-cell persistence in both peripheral blood and tissues (BM, spleens, and livers), resulting in a significant survival advantage in one AML xenograft model and two autologous AML PDX models. In conclusion, we demonstrate here that the expansion, persistence, and anti-AML activity of CD123-ENG T-cells can be significantly improved by transgenic expression of IL15, which promotes a naïve/TSCM-like phenotype. However, we also highlight that targeting a single tumor antigen (CD123) can lead to immune escape, reinforcing the need to develop approaches to target multiple antigens. Likewise, our study demonstrates that it is feasible to evaluate autologous T cells in AML PDX models, which will be critical for future preclinical evaluations of next generation AML-redirected T-cell therapies.

Hypomethylating agent and venetoclax with FLT3 inhibitor "triplet" therapy in older/unfit patients with FLT3 mutated AML

In older/unfit newly diagnosed patients with FLT3 mutated acute myeloid leukemia (AML), lower intensity chemotherapy (LIC) in combination with either a FLT3 inhibitor or with venetoclax results in poor overall survival (median 8 to 12.5 months). We performed a retrospective analysis of 87 newly diagnosed FLT3 mutated AML patients treated on triplet (LIC + FLT3 inhibitor + Venetoclax, [N = 27]) and doublet (LIC + FLT3 inhibitor, [N = 60]) regimens at our institution. Data were collected from prospective clinical trials in 75% (N = 65) and 25% (N = 22) who received the same treatment regimens outside of a clinical trial. Triplet therapy was associated with significantly higher rates of complete remission (CR) (67% versus 32%, P = 0.002), CR/CRi (93% versus 70%, P = 0.02), FLT3-PCR negativity (96% versus 54%, P < 0.01), and flow-cytometry negativity (83% versus 38%, P < 0.01) than doublets. At the end of the first cycle, the median time to ANC > 0.5 (40 versus 21 days, P = 0.15) and platelet > 50 K (29 versus 25 days, P = 0.6) among responders was numerically longer with triplets, but 60-day mortality was similar (7% v 10%). With a median follow-up of 24 months (median 12 months for triplet arm, and 63 months for doublet arm), patients receiving a triplet regimen had a longer median overall survival (not reached versus 9.5 months, P < 0.01). LIC combined with FLT3 inhibitor and venetoclax (triplet) may be an effective frontline regimen for older/unfit FLT3 mutated AML that should be further validated prospectively.

A multi-arm phase Ib/II study designed for rapid, parallel evaluation of novel immunotherapy combinations in relapsed/refractory acute myeloid leukemia

We conducted a phase Ib/II multi-arm, parallel cohort study to simultaneously evaluate various immunotherapeutic agents and combinations in relapsed/refractory acute myeloid leukemia (AML). Overall, 50 patients were enrolled into one of 6 arms: (A) single agent PF-04518600 (OX40 agonist monoclonal antibody), (B) azacitidine + venetoclax + gemtuzumab ozogamicin (GO), (C) azacitidine + avelumab (anti-PD-L1 monoclonal antibody) + GO, (D) azacitidine + venetoclax + avelumab, (E) azacitidine + avelumab + PF-04518600, and (F) glasdegib + GO. Among all regimens evaluated, azacitidine + venetoclax + GO appeared most promising. In this arm, the CR/CRi rates among venetoclax-naïve and prior venetoclax-exposed patients were 50% and 22%, respectively, and the 1-year OS rate was 31%. This study shows the feasibility of a conducting a multi-arm trial to efficiently and simultaneously evaluate novel therapies in AML, a needed strategy in light of the plethora of emerging therapies. This trial was registered at www.clinicaltrials.gov as NCT03390296.

Maximal activation of apoptosis signaling by co-targeting anti-apoptotic proteins in BH3 mimetic-resistant AML and AML stem cells

MCL-1 is known to play a major role in resistance to BCL-2 inhibition, but the contribution of other BCL-2 family proteins has not been fully explored. We here demonstrate ineffectiveness of MCL-1 inhibitor AMG176 in venetoclax-resistant, and conversely, of venetoclax in AMG176-resistant AML. Like cells with acquired resistance to venetoclax, cells with acquired resistance to AMG176 express increased MCL-1. Both cells with acquired resistance to venetoclax and to AMG176 express increased levels of BCL-2 and BCL-2A1, decreased BAX, and/or altered levels of other BCL-2 proteins. Co-targeting BCL-2 and MCL-1 was highly synergistic in AML cell lines with intrinsic or acquired resistance to BH3 mimetics or engineered to genetically-overexpress BCL-2 or BCL-2A1 or downregulate BAX. The combination effectively eliminated primary AML blasts and stem/progenitor cells resistant to or relapsed after venetoclax-based therapy irrespective of mutations and cytogenetic abnormalities. Venetoclax and AMG176 combination markedly suppressed anti-apoptotic BCL-2 proteins and AML stem/progenitor cells and dramatically extended mouse survival (median 336 vs control 126 d, P&lt;0.0001) in a PDX model developed from a venetoclax/hypomethylating agent therapy-resistant AML patient. However, decreased BAX levels in the bone marrow residual leukemia cells after 4-wk combination treatment may represent a resistance mechanism that contributed to their survival. Enhanced anti-leukemia activity was also observed in a PDX model of monocytic AML, known to be resistant to venetoclax therapy. Our results support co-dependence on multiple anti-apoptotic BCL-2 proteins and suppression of BAX as mechanisms of AML resistance to individual BH3 mimetics. Co-targeting of MCL-1 and BCL-2 eliminates otherwise apoptosis-resistant cells.

Metabolic stress induces GD2+ cancer stem cell-like phenotype in triple-negative breast cancer

BACKGROUND

Metabolic stress resulting from nutrient deficiency is one of the hallmarks of a growing tumour. Here, we tested the hypothesis that metabolic stress induces breast cancer stem-like cell (BCSC) phenotype in triple-negative breast cancer (TNBC).

METHODS

Flow cytometry for GD2 expression, mass spectrometry and Ingenuity Pathway Analysis for metabolomics, bioinformatics, in vitro tumorigenesis and in vivo models were used.

RESULTS

Serum/glucose deprivation not only increased stress markers but also enhanced GD2⁺ BCSC phenotype and function in TNBC cells. Global metabolomics profiling identified upregulation of glutathione biosynthesis in GD2^high cells, suggesting a role of glutamine in the BCSC phenotype. Cueing from the upregulation of the glutamine transporters in primary breast tumours, inhibition of glutamine uptake using small-molecule inhibitor V9302 reduced GD2⁺ cells by 70-80% and BCSC characteristics in TNBC cells. Mechanistic studies revealed inhibition of the mTOR pathway and induction of ferroptosis by V9302 in TNBC cells. Finally, inhibition of glutamine uptake significantly reduced in vivo tumour growth in a TNBC patient-derived xenograft model using NSG (non-obese diabetic/severe combined immunodeficiency with a complete null allele of the IL-2 receptor common gamma chain) mice.

CONCLUSION

Here, we show metabolic stress results in GD2⁺ BCSC phenotype in TNBC and glutamine contributes to GD2⁺ phenotype, and targeting the glutamine transporters could complement conventional chemotherapy in TNBC.

In-depth analysis of SARS-CoV-2-specific T cells reveals diverse differentiation hierarchies in vaccinated individuals

SARS-CoV-2 vaccines pose as the most effective approach for mitigating the COVID-19 pandemic. High-degree efficacy of SARS-CoV-2 vaccines in clinical trials indicates that vaccination invariably induces an adaptive immune response. However, the emergence of breakthrough infections in vaccinated individuals suggests that the breadth and magnitude of vaccine-induced adaptive immune response may vary. We assessed vaccine-induced SARS-CoV-2 T cell response in 21 vaccinated individuals and found that SARS-CoV-2–specific T cells, which were mainly CD4⁺ T cells, were invariably detected in all individuals but the response was varied. We then investigated differentiation states and cytokine profiles to identify immune features associated with superior recall function and longevity. We identified SARS-CoV-2–specific CD4⁺ T cells were polyfunctional and produced high levels of IL-2, which could be associated with superior longevity. Based on the breadth and magnitude of vaccine-induced SARS-CoV-2 response, we identified 2 distinct response groups: individuals with high abundance versus low abundance of SARS-CoV-2–specific T cells. The fractions of TNF-α– and IL-2–producing SARS-CoV-2 T cells were the main determinants distinguishing high versus low responders. Last, we identified that the majority of vaccine-induced SARS-CoV-2 T cells were reactive against non-mutated regions of mutant S-protein, suggesting that vaccine-induced SARS-CoV-2 T cells could provide continued protection against emerging variants of concern.

Activation of RAS/MAPK pathway confers MCL-1 mediated acquired resistance to BCL-2 inhibitor venetoclax in acute myeloid leukemia

Despite high initial response rates, acute myeloid leukemia (AML) treated with the BCL-2-selective inhibitor venetoclax (VEN) alone or in combinations commonly acquires resistance. We performed gene/protein expression, metabolomic and methylation analyses of isogenic AML cell lines sensitive or resistant to VEN, and identified the activation of RAS/MAPK pathway, leading to increased stability and higher levels of MCL-1 protein, as a major acquired mechanism of VEN resistance. MCL-1 sustained survival and maintained mitochondrial respiration in VEN-RE cells, which had impaired electron transport chain (ETC) complex II activity, and MCL-1 silencing or pharmacologic inhibition restored VEN sensitivity. In support of the importance of RAS/MAPK activation, we found by single-cell DNA sequencing rapid clonal selection of RAS-mutated clones in AML patients treated with VEN-containing regimens. In summary, these findings establish RAS/MAPK/MCL-1 and mitochondrial fitness as key survival mechanisms of VEN-RE AML and provide the rationale for combinatorial strategies effectively targeting these pathways.

Targeting the NOTCH1-MYC-CD44 axis in leukemia-initiating cells in T-ALL

The NOTCH1-MYC-CD44 axis integrates cell-intrinsic and extrinsic signaling to ensure the persistence of leukemia-initiating cells (LICs) in T-cell acute lymphoblastic leukemia (T-ALL) but a common pathway to target this circuit is poorly defined. Bromodomain-containing protein 4 (BRD4) is implicated to have a role in the transcriptional regulation of oncogenes MYC and targets downstream of NOTCH1, and here we demonstrate its role in transcriptional regulation of CD44. Hence, targeting BRD4 will dismantle the NOTCH1-MYC-CD44 axis. As a proof of concept, degrading BRD4 with proteolysis targeting chimera (PROTAC) ARV-825, prolonged the survival of mice in Notch1 mutated patient-derived xenograft (PDX) and genetic models (ΔPTEN) of T-ALL. Single-cell proteomics analysis from the PDX model, demonstrated quantitative reduction of LICs (CD34+ CD7+ CD19−) and downregulation of the NOTCH1-MYC-CD44 axis, along with cell cycle, apoptosis and PI3K/Akt pathways. Moreover, secondary transplantation from PDX and ΔPTEN models of T-ALL, confirmed delayed leukemia development and extended survival of mice engrafted with T-ALL from ARV-825 treated mice, providing functional confirmation of depletion of LICs. Hence, BRD4 degradation is a promising LIC-targeting therapy for T-ALL.

Inhibition of BCL2A1 by STAT5 inactivation overcomes resistance to targeted therapies of FLT3-ITD/D835 mutant AML

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BCL2A1 is upregulated and exerts a pro-survival function in FLT3-ITD/D835 AML cells.

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Upregulation of BCL2A1 attenuates sensitivity to quizartinib in FLT3-ITD/D835 cells.

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Gilteritinib decreases BCL2A1 through inactivation of STAT5 in FLT3-ITD/D835 cells.

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Gilteritinib/Venetoclax has a synergistic anti-tumor activity in FLT3-ITD/D835 cells.

Tyrosine kinase inhibitors (TKIs) are established drugs in the therapy of FLT3-ITD mutated acute myeloid leukemia (AML). However, acquired mutations, such as D835 in the tyrosine kinase domain (FLT3-ITD/D835), can induce resistance to TKIs. A cap analysis gene expression (CAGE) technology revealed that the gene expression of BCL2A1 transcription start sites was increased in primary AML cells bearing FLT3-ITD/D835 compared to FLT3-ITD. Overexpression of BCL2A1 attenuated the sensitivity to quizartinib, a type II TKI, and venetoclax, a selective BCL2 inhibitor, in AML cell lines. However, a type I TKI, gilteritinib, inhibited the expression of BCL2A1 through inactivation of STAT5 and alleviated TKI resistance of FLT3-ITD/D835. The combination of gilteritinib and venetoclax showed synergistic effects in the FLT3-ITD/D835 positive AML cells. The promoter region of BCL2A1 contains a BRD4 binding site. Thus, the blockade of BRD4 with a BET inhibitor (CPI-0610) downregulated BCL2A1 in FLT3-mutated AML cells and extended profound suppression of FLT3-ITD/D835 mutant cells. Therefore, we propose that BCL2A1 has the potential to be a novel therapeutic target in treating FLT3-ITD/D835 mutated AML.

Efficacy and safety of enasidenib and azacitidine combination in patients with IDH2 mutated acute myeloid leukemia and not eligible for intensive chemotherapy

Preclinically, enasidenib and azacitidine (ENA + AZA) synergistically enhance cell differentiation, and venetoclax (VEN), a small molecule Bcl2 inhibitor (i) is particularly effective in IDH2 mutated acute myeloid leukemia (IDH2^mutAML). This open label phase II trial enrolled patients (pts) with documented IDH2^mutAML. All patients received AZA 75 mg/m²/d x 7 d/cycle and ENA 100 mg QD continuously. Concomitant Bcl2i and FLT3i were allowed (NCT03683433).Twenty-six pts received ENA + AZA (median 68 years, range, 24–88); 7 newly diagnosed (ND) and 19 relapsed/refractory (R/R). In R/R AML patients, three had received prior ENA and none had received prior VEN. The composite complete remission rate (CRc) [complete remission (CR) or complete remission with incomplete hematologic recovery (CRi)] was 100% in ND AML, and 58% in R/R AML. Median OS was not reached in ND AML with median follow-up of 13.1 months (mo); Pts treated in first relapse had improved OS than those with ≥2 relapse (median OS not reached vs 5.2 mo; HR 0.24, 95% CI 0.07–0.79, p = 0.04). Two patients received ENA + AZA with a concomitant FLT3i, one responding ND AML patient and one nonresponding R/R AML patient. Seven R/R AML pts received ENA + AZA + VEN triplet, and with median follow up of 11.2 mo, median OS was not reached and 6-mo OS was 70%. The most frequent treatment-emergent adverse events include febrile neutropenia (23%). Adverse events of special interest included all-grade IDH differentiation syndrome (8%) and indirect hyperbilirubinemia (35%). ENA + AZA was a well-tolerated, and effective therapy for elderly pts with IDH2^mut ND AML as well as pts with R/R AML. The addition of VEN to ENA + AZA appears to improve outcomes in R/R IDH2^mutAML.

Clinical trial registration information: https://clinicaltrials.gov/.NCT03683433