Impact of FLT3 Mutation on Outcomes after Venetoclax and Azacitidine for Patients with Treatment-Naïve Acute Myeloid Leukemia

Prognostic analysis according to European LeukemiaNet 2022 risk stratification for elderly patients with acute myeloid leukemia treated with decitabine

OBJECTIVES

This study aimed to evaluate the prognostic significance of the revised European LeukemiaNet (ELN)-2022 risk stratification model for 123 elderly acute myeloid leukemia (AML) patients treated with decitabine chemotherapy.

RESULTS

Based on the ELN-2022 risk stratification, 15 (12.2%), 51 (41.5%), and 57 (46.3%) patients were classified as having favorable, intermediate, and high-risk AML, respectively. In comparison with the ELN-2017 risk stratification, the ELN-2022 risk stratification re-assigned 26 (21.1%) and three (2.4%) patients to the adverse and favorable risk groups, respectively. Survival analysis revealed distinctive overall survival (OS) outcomes among the ELN-2022 risk groups (6-month OS rate: 73.3%, 52.9%, and 47.7% for favorable, intermediate, and adverse risk, respectively; P = 0.101), with a parallel trend observed in the event-free survival (EFS) (6-month EFS rate: 73.3%, 52.9%, and 45.6% for favorable, intermediate, and adverse risk, respectively; P = 0.049). Notably, both OS and EFS in the favorable risk group were significantly superior in comparison to that of the adverse risk group (OS: P = 0.040, EFS: P = 0.030). Although the ELN-2022 C-index (0.559) was greater than the ELN-2017 C-index (0.539), the result was not statistically significant (P = 0.059). Based on the event net reclassification index, we consistently observed significant improvements in the ELN-2022 risk stratification for overall survival (0.21 at 6 months).

CONCLUSION

In conclusion, the revised ELN-2022 risk stratification model may have improved the risk classification of elderly AML patients treated with hypomethylating agents compared to the ELN-2017 risk stratification model.

Azacitidine, Venetoclax, and Gilteritinib in Newly Diagnosed and Relapsed or Refractory FLT3-Mutated AML

PURPOSE

Azacitidine plus venetoclax is a standard of care for patients with newly diagnosed AML who are unfit for intensive chemotherapy. However, FLT3 mutations are a common mechanism of resistance to this regimen. The addition of gilteritinib, an oral FLT3 inhibitor, to azacitidine and venetoclax may improve outcomes in patients with FLT3-mutated AML.

METHODS

This phase I/II study evaluated azacitidine, venetoclax, and gilteritinib in two cohorts: patients with (1) newly diagnosed FLT3-mutated AML who were unfit for intensive chemotherapy or (2) relapsed/refractory FLT3-mutated AML (ClinicalTrials.gov identifier: NCT04140487). The primary end points were the maximum tolerated dose of gilteritinib (phase I) and the combined complete remission (CR)/CR with incomplete hematologic recovery (CRi) rate (phase II).

RESULTS

Fifty-two patients were enrolled (frontline [n = 30]; relapsed/refractory [n = 22]). The recommended phase II dose was gilteritinib 80 mg once daily in combination with azacitidine and venetoclax. In the frontline cohort, the median age was 71 years and 73% of patients had an FLT3-internal tandem duplication (ITD) mutation. The CR/CRi rate was 96% (CR, 90%; CRi, 6%). Sixty-five percent of evaluable patients achieved FLT3-ITD measurable residual disease <5 × 10-5 within four cycles. With a median follow-up of 19.3 months, the median relapse-free survival (RFS) and overall survival (OS) have not been reached and the 18-month RFS and OS rates are 71% and 72%, respectively. In the relapsed/refractory cohort, the CR/CRi rate was 27%; nine additional patients (41%) achieved a morphologic leukemia-free state. The most common grade 3 or higher nonhematologic adverse events were infection (62%) and febrile neutropenia (38%), which were more frequent in the relapsed/refractory cohort.

CONCLUSION

The combination of azacitidine, venetoclax, and gilteritinib resulted in high rates of CR/CRi, deep FLT3 molecular responses, and encouraging survival in newly diagnosed FLT3-mutated AML. Myelosuppression was manageable with mitigative dosing strategies.

Transplant Eligible and Ineligible Elderly Patients with AML-A Genomic Approach and Next Generation Questions

The management of elderly patients diagnosed with acute myelogenous leukemia (AML) is complicated by high relapse risk and comorbidities that often preclude access to allogeneic hematopoietic cellular transplantation (allo-HCT). In recent years, fast-paced FDA drug approval has reshaped the therapeutic landscape, with modest, albeit promising improvement in survival. Still, AML outcomes in elderly patients remain unacceptably unfavorable highlighting the need for better understanding of disease biology and tailored strategies. In this review, we discuss recent modifications suggested by European Leukemia Network 2022 (ELN-2022) risk stratification and review recent aging cell biology advances with the discussion of four AML cases. While an older age, >60 years, does not constitute an absolute contraindication for allo-HCT, the careful patient selection based on a detailed and multidisciplinary risk stratification cannot be overemphasized.

Long-term follow-up of VIALE-A: Venetoclax and azacitidine in chemotherapy-ineligible untreated acute myeloid leukemia

Venetoclax-azacitidine is approved for treatment of patients with newly diagnosed acute myeloid leukemia (AML) ineligible for intensive chemotherapy based on the interim overall survival (OS) analysis of the VIALE-A study (NCT02993523). Here, long-term follow-up is presented to address survival benefit and long-term outcomes with venetoclax-azacitidine. Patients with newly diagnosed AML who were ineligible for intensive chemotherapy were randomized 2:1 to receive venetoclax-azacitidine or placebo-azacitidine. OS was the primary endpoint; complete remission with/without blood count recovery (CR/CRi) was a key secondary endpoint. This final analysis was conducted when 100% of the predefined 360 OS events occurred. In VIALE-A, 431 patients were enrolled to venetoclax-azacitidine (n = 286) or placebo-azacitidine (n = 145). At 43.2 months median follow-up, median OS was 14.7 months (95% confidence interval [CI], 12.1-18.7) with venetoclax-azacitidine, and 9.6 months (95% CI, 7.4-12.7) with placebo-azacitidine (hazard ratio, 0.58 [95% CI, 0.47-0.72], p < .001); the estimated 24-month OS rate was 37.5% and 16.9%, respectively. Median OS for patients with IDH1/2 mutations and those with measurable residual disease responses was reached in this final analysis. CR/CRi rate was similar to interim analysis. Any-grade hematologic and gastrointestinal adverse events were most common in venetoclax-azacitidine and placebo-azacitidine arms, including thrombocytopenia (47% and 42%) and neutropenia (43% and 29%). No new safety signals were identified. Long-term efficacy and safety confirm venetoclax-azacitidine is an improvement in standard-of-care for patients with AML who are not eligible for intensive chemotherapy because of advanced age or comorbidities.

Clinical outcomes of hypomethylating agents plus Venetoclax as frontline treatment in patients 75 years and older with acute myeloid leukemia: Real-world data from eight US academic centers

Venetoclax (VEN) combined with hypomethylating agents (HMAs) is the standard of care for the treatment of patients with newly diagnosed acute myeloid leukemia (AML) unfit for intensive chemotherapy. To date, real-world data published on HMAs plus VEN have been either single-center studies or using community-based electronic databases with limited details on mutational landscape, tolerability, and treatment patterns in elderly patients. Therefore, we conducted a multicenter retrospective study to assess the real-world experience of 204 elderly patients (≥75 years) with newly diagnosed AML treated with HMAs plus VEN from eight academic centers in the United States. Overall, 64 patients achieved complete remission (CR; 38%) and 43 CR with incomplete count recovery (CRi; 26%) for a CR/CRi rate of 64%, with a median duration of response of 14.2 months (95% CI: 9.43, 22.1). Among responders, 63 patients relapsed (59%) with median overall survival (OS) after relapse of 3.4 months (95% CI, 2.4, 6.7). Median OS for the entire population was 9.5 months (95% CI, 7.85-13.5), with OS significantly worse among patients with TP53-mutated AML (2.5 months) and improved in patients harboring NPM1, IDH1, and IDH2 mutations (13.5, 18.3, and 21.1 months, respectively). The 30-day and 60-day mortality rates were 9% and 19%, respectively. In conclusion, HMAs plus VEN yielded high response rates in elderly patients with newly diagnosed AML. The median OS was inferior to that reported in the VIALE-A trial. Outcomes are dismal after failure of HMAs plus VEN, representing an area of urgent unmet clinical need.

Gilteritinib in combination with venetoclax, low-dose cytarabine and actinomycin D for relapsed or refractory FLT3-mutated acute myeloid leukaemia

We have conducted a retrospective, single-centre analysis of 20 patients with relapsed or refractory FLT3-mutated acute myeloid leukaemia (FLT3m AML) who received a salvage quadruplet regimen consisting of gilteritinib, venetoclax, low-dose cytarabine and actinomycin D (G-ACTIVE). G-ACTIVE resulted in a 95% (19/20) overall response rate and 75% (15/20) complete remission and complete remission with an incomplete platelet recovery (CR + CRp) rate. Out of 13 transplant-eligible patients, 11 (86%) proceeded to an allogeneic stem cell transplantation. The median overall survival and relapse-free survival after G-ACTIVE were 32 and 12.9 months respectively. The Day 60 mortality rate was 15%.

Spectrum of infections in different regimens of post-induction chemotherapy in acute myeloid leukemia (de-novo): A comparative retrospective study

Background

Patients diagnosed with acute myeloid leukemia (AML) face a heightened susceptibility to infections, which significantly elevates their risk of mortality and disability. The intensity of the chemotherapy treatment and its specific focus on inhibiting myeloid cell divisions render patients especially vulnerable, particularly during the early stages of chemotherapy. This vulnerability is compounded by the occurrence of repeated episodes of prolonged neutropenia, leaving patients highly susceptible to infections. The compromised immune systems of these individuals make them more susceptible to infections, which adversely affect their physical health and overall well-being. Consequently, our study aimed to investigate the range of infections experienced by patients with newly diagnosed AML undergoing different induction chemotherapy.

Methods

This was a comparative retrospective study, conducted at a tertiary hospital providing comprehensive cancer care in North India. All newly diagnosed patients with AML, who received induction chemotherapy from January 1, 2012 to November 1, 2022, were identified from the hospital database and included in this study.

Results

Four hundred and twenty AML patients treated with either high-intensity or low-intensity induction chemotherapy was observed in this study. It was found that patients who received high-intensity treatment had a higher rate of clinically and microbiologically documented infections, fever without a known cause, and more cases of febrile neutropenia than those who got low-intensity treatment. These differences between the two groups were particularly evident on day 14 (p = 0.0002) and persisted through day 28 (p = 0.005).

Conclusions

These findings underscore the effectiveness and downside of high-intensity induction chemotherapy regimens, as evidenced by the higher incidence of infections observed. Further investigation through prospective clinical studies is warranted to better evaluate and validate the efficacy of this approach.

A Markov analysis of azacitidine and venetoclax vs induction chemotherapy for medically fit patients with AML

ABSTRACT

Although induction chemotherapy (IC) is the standard of care in medically fit patients with newly diagnosed acute myeloid leukemia (AML), limited retrospective data indicate that patients at adverse-risk may benefit from azacytidine and venetoclax (aza-ven). Our goal was to perform a Markov decision analysis to determine whether IC or aza-ven is the optimal induction regimen in this population. Using the TreeAge software, Markov models were created for adverse-risk and intermediate-risk cohorts. A systematic review of the literature informed the transition probabilities and utilities included in the analyses. Our primary outcome was quality-adjusted life years (QALYs) gained over 5 years after diagnosis. Overall, patients at adverse risk treated with IC gained 1.4 QALYs, compared with 2.0 QALYs in patients treated with aza-ven. Patients at adverse risk treated with IC and allogeneic stem cell transplantation (allo-SCT), IC, aza-ven and allo-SCT, or aza-ven gained 2.1, 1.5, 3.0, and 1.9 QALYs, respectively. Meanwhile, patients at intermediate risk treated with IC gained 2.0 QALY, compared with 1.7 QALY in patients treated with aza-ven. Patients at intermediate risk treated with IC and allo-SCT, IC, aza-ven and allo-SCT, and aza-ven gained 2.7, 2.3, 2.6, and 1.8 QALYs, respectively. We have demonstrated that medically fit patients with newly diagnosed adverse-risk AML may benefit from treatment with aza-ven over those treated with IC, whereas IC remains the preferred approach for patients at intermediate risk. Our work challenges the use of the European LeukemiaNet risk classification for patients treated with aza-ven and highlights the need for prospective investigation into aza-ven as induction therapy for medically fit patients.

Fludarabine, cytarabine, and idarubicin with or without venetoclax in patients with relapsed/refractory acute myeloid leukemia

Treatment options for relapsed and refractory acute myeloid leukemia patients (R/R AML) are limited. This retrospective cohort study compares safety and efficacy of fludarabine, cytarabine, and idarubicin (FLA-IDA) without or with venetoclax (FLAVIDA) in patients with R/R AML. Thirty-seven and 81 patients received one course FLA-IDA with or without a 7-day course of venetoclax, respectively. The overall response rate (ORR) was significantly higher in FLAVIDA compared to FLAIDA- treated patients (78% vs. 47%; P=0.001), while measurable residual disease was negative at a similar proportion in responding patients (50% vs. 57%), respectively. Eighty-one percent and 79% of patients proceeded to allogeneic hematopoietic cell transplantation or donor lymphocyte infusion after FLAVIDA and FLA-IDA, respectively. Event-free and overall survival were similar in FLAVIDA- and FLA-IDA-treated patients. Refractory patients could be salvaged more successfully after FLA-IDA compared to FLAVIDA pretreatment. Neutrophil and platelet recovery times were similar in the venetoclax and the control group. In conclusion, short-term venetoclax in combination with FLA-IDA represents an effective treatment regimen in R/R AML identifying chemosensitive patients rapidly and inducing measurable residual disease-negative remission in a high proportion of R/R AML patients.

Clinical and genetic characteristics predict outcomes of acute myeloid leukemia patients with FLT3 mutations receiving venetoclax-based therapy

BACKGROUND

Acute myeloid leukemia (AML) is a heterogeneous disease, and its heterogeneity is associated with treatment response. Despite the demonstrated success of venetoclax (VEN)-based therapy for AML, the effect of FLT3 mutations on the efficacy of the therapy is poorly understood. We aimed to compare the efficacy of VEN-based therapy between FLT3-mutated (FLT3mut ) and FLT3 wild-type (FLT3wt ) patients and identify the predictors of efficacy in FLT3mut patients.

METHODS

A total of 266 AML patients (127 newly diagnosed [ND] and 139 refractory/relapsed [R/R]) receiving VEN-based regimens were enrolled in this study. A retrospective analysis was performed, and the treatment responses and overall survival (OS) of FLT3mut and FLT3wt patients were compared. Logistic regression and Cox proportional hazards model were applied to examine the clinical and genetic predictors of outcomes.

RESULTS

With a median of two cycles of VEN-based therapy, for the ND AML cohort, the FLT3mut group had a comparable composite complete remission (CRc) rate with the FLT3wt group (79.3% vs. 61.2%, p = 0.072). For the R/R AML cohort, the FLT3mut group exhibited a lower CRc rate than the FLT3wt group. With a median follow-up of 8.6 months (95% confidence interval [CI], 8.0-10), the median OS observed in the FLT3mut and FLT3wt groups for both cohorts were close (14.0 vs. 19.9 months, p = 0.356; 10.0 vs. 11.9 months, p = 0.680). For the ND AML cohort, in FLT3mut patients, MRD-positive and RNA-splicing mutation predicted inferior survival (hazard ratio [HR], 10.3; 95% CI: 2.0-53.8; p = 0.006; HR 11.3; 95% CI: 1.2-109.3; p = 0.036, respectively). For the R/R AML cohort, in FLT3mut patients, adverse ELN risk was associated with an inferior response (odds ratio [OR], 0.2; 95% CI: 0.1-0.8; p = 0.025), whereas NPM1 co-mutation was associated with a superior response (57.1%; OR, 6.7; 95% CI: 1.5-30.1; p = 0.014). CR/CRi predicted a better survival (HR 0.2; 95% CI: 0.1-0.8; p = 0.029), while DNMT3A mutation predicted an inferior survival (HR, 4.6; 95% CI: 1.4-14.9; p = 0.011).

CONCLUSIONS

FLT3 mutations may influence response to VEN-based therapy in R/R AML patients but not in ND AML patients. Furthermore, clinical and genetic characteristics could predict outcomes of FLT3mut patients receiving VEN-based therapy.

The future paradigm of HMA + VEN or targeted inhibitor approaches: sequencing or triplet combinations in AML therapy

The routine use of next-generation sequencing methods has underscored the genetic and clonal heterogeneity of acute myeloid leukemia (AML), subsequently ushering in an era of precision medicine-based targeted therapies exemplified by the small-molecule inhibitors of FLT3, IDH1/IDH2, and BCL2. This advent of targeted drugs in AML has broadened the spectrum of antileukemic therapies, and the approval of venetoclax in combination with a hypomethylating agent has been a welcome addition to our AML patients unable to tolerate intensive chemotherapy. Mounting evidence demonstrates that molecularly targeted agents combined with epigenetic therapies exhibit synergistic augmented leukemic cell kill compared to single-agent therapy. With such great power comes greater responsibility in determining the appropriate frontline AML treatment regimen in a molecularly defined subset and identifying safe and effective combination therapies with different mechanisms of action to outmaneuver primary and secondary resistance mechanisms in AML.

Hypomethylating agents plus modified priming regimens compared with venetoclax-based regimens based on molecular characteristics for newly diagnosed patients with acute myeloid leukemia: a multi-center cohort study

Venetoclax (VEN)-based regimens are the standard of care for elderly or unfit patients with newly diagnosed (ND) acute myeloid leukemia (AML). Some single-arm studies have implied that hypomethylating agents (HMAs) plus priming regimens may potentially provide an alternative therapeutic approach, owing to encouraging efficacy seen. However, no comparative data exists yet regarding these two treatment approaches. In this retrospective multi-center cohort study, we enrolled 294 ND AML patients, allocating 167 to the HMA + priming group and 127 to the VEN-based group. Treatment response and overall survival (OS) were compared between groups. Molecular subgroup analyses were also conducted. With a median of two cycles for HMA + priming group, the overall response (ORR) was 65.3%, including 55.1% complete remission (CR), 9.6% CR with incomplete hematologic recovery (CRi) and 0.6% morphologic leukemia-free state (MLFS). With a median of two cycles for VEN-based group, the ORR was 70.9%, including 46.5% CR, 18.9% CRi, and 5.5% MLFS. Response differences (ORR or CR/CRi) between groups were not significant (p > 0.05). With a median follow-up of 10.1 months, median OSs were similar between groups (20.9 vs 16.3 months, p = 0.41). However, VEN regimens demonstrated superior CR/CRi for patients with mutations in FLT3, IDH1/2, and NPM1 compared to HMA + priming (80.0% vs 35.0%, p = 0.01; 90.9% vs 65.5%, p = 0.02; 90.9% and 65.5%, p = 0.02, respectively). In conclusion, HMAs plus modified priming regimens might be a potential alternative therapeutic approach for patients with ND AML, but VEN-based regimens presented predominance in specific molecular subgroups. Molecular characteristics contribute to guiding choice of treatment.

Fms -like tyrosine kinase 3 positive acute myeloid leukemia

PURPOSE OF REVIEW

Fms -like tyrosine kinase 3 (FLT3) mutations are common in newly diagnosed patients with acute myeloid leukemia (AML). They are associated with a high risk of relapse. The identification of FLT3 mutations has important implications for the management of AML. FLT3 inhibitors have shown improved outcomes in FLT3-positive AML when used as a single agent in the salvage setting. However, the combination of inhibitors and chemotherapy in the first-line setting is the real game changer in FLT3mutant AML. The introduction of these drugs has improved the prognosis of FLT3-mutant AML, but the development of resistance is common. There are still many unanswered questions about FLT3-mutant AML.

RECENT FINDINGS

This article will analyze recent advances for FLT3-mutant AML, focusing on front-line therapy and post-transplant maintenance.

SUMMARY

Novel drug combinations and strategies against FLT3 mutated AML are currently under investigation and will be the focus of future studies. The development of more selective and potent FLT3 inhibitors may further improve outcomes for patients with FLT3-positive AML. Monitoring minimal residual disease and overcoming resistance are key issues for the future.

Clinical impact of the genomic landscape and leukemogenic trajectories in non-intensively treated elderly acute myeloid leukemia patients

To characterize the genomic landscape and leukemogenic pathways of older, newly diagnosed, non-intensively treated patients with AML and to study the clinical implications, comprehensive genetics analyses were performed including targeted DNA sequencing of 263 genes in 604 patients treated in a prospective Phase III clinical trial. Leukemic trajectories were delineated using oncogenetic tree modeling and hierarchical clustering, and prognostic groups were derived from multivariable Cox regression models. Clonal hematopoiesis-related genes (ASXL1, TET2, SRSF2, DNMT3A) were most frequently mutated. The oncogenetic modeling algorithm produced a tree with five branches with ASXL1, DDX41, DNMT3A, TET2, and TP53 emanating from the root suggesting leukemia-initiating events which gave rise to further subbranches with distinct subclones. Unsupervised clustering mirrored the genetic groups identified by the tree model. Multivariable analysis identified FLT3 internal tandem duplications (ITD), SRSF2, and TP53 mutations as poor prognostic factors, while DDX41 mutations exerted an exceptionally favorable effect. Subsequent backwards elimination based on the Akaike information criterion delineated three genetic risk groups: DDX41 mutations (favorable-risk), DDX41wildtype/FLT3-ITDneg/TP53wildtype (intermediate-risk), and FLT3-ITD or TP53 mutations (high-risk). Our data identified distinct trajectories of leukemia development in older AML patients and provide a basis for a clinically meaningful genetic outcome stratification for patients receiving less intensive therapies.

AML under the Scope: Current Strategies and Treatment Involving FLT3 Inhibitors and Venetoclax-Based Regimens

Acute myeloid leukemia (AML) is a disease that mainly affects elderly patients who are more often unfit for intensive chemotherapy (median age of diagnosis is 68). The regimens, including venetoclax, a highly specific BCL-2 (B-cell lymphoma-2) inhibitor, are a common alternative because of their safer profile and fewer side effects. However, the resistance phenomenon of leukemic cells necessitates the search for drugs that would help to overcome the resistance and improve treatment outcomes. One of the resistance mechanisms takes place through the upregulation of MCL-1 and BCL-XL, preventing BAX/BAK-driven MOMP (mitochondrial outer membrane permeabilization), thus stopping the apoptosis process. Possible partners for BCL-2 inhibitors may include inhibitors from the FLT3i (FMS-like tyrosine kinase-3 inhibitor) group. They resensitize cancer cells through the downregulation of MCL-1 expression in the FLT3 mutated cells, resulting in the stronger efficacy of BCL-2 inhibitors. Also, they provide an additional pathway for targeting the clonal cell. Both preclinical and clinical data suggest that the combination might show a synergistic effect and improve patients' outcomes. The aim of this review is to determine whether the combination of venetoclax and FLT3 inhibitors can impact the therapeutic approaches and what other agents they can be combined with.

Current Advances and Future Strategies for BCL-2 Inhibitors: Potent Weapons against Cancers

Targeting the intrinsic apoptotic pathway regulated by B-cell lymphoma-2 (BCL-2) antiapoptotic proteins can overcome the evasion of apoptosis in cancer cells. BCL-2 inhibitors have evolved into an important means of treating cancers by inducing tumor cell apoptosis. As the most extensively investigated BCL-2 inhibitor, venetoclax is highly selective for BCL-2 and can effectively inhibit tumor survival. Its emergence and development have significantly influenced the therapeutic landscape of hematological malignancies, especially in chronic lymphocytic leukemia and acute myeloid leukemia, in which it has been clearly incorporated into the recommended treatment regimens. In addition, the considerable efficacy of venetoclax in combination with other agents has been demonstrated in relapsed and refractory multiple myeloma and certain lymphomas. Although venetoclax plays a prominent antitumor role in preclinical experiments and clinical trials, large individual differences in treatment outcomes have been characterized in real-world patient populations, and reduced drug sensitivity will lead to disease recurrence or progression. The therapeutic efficacy may vary widely in patients with different molecular characteristics, and key genetic mutations potentially result in differential sensitivities to venetoclax. The identification and validation of more novel biomarkers are required to accurately predict the effectiveness of BCL-2 inhibition therapy. Furthermore, we summarize the recent research progress relating to the use of BCL-2 inhibitors in solid tumor treatment and demonstrate that a wealth of preclinical models have shown promising results through combination therapies. The applications of venetoclax in solid tumors warrant further clinical investigation to define its prospects.

A comprehensive analysis of cell-autonomous and non-cell-autonomous regulation of myeloid leukemic cells: The prospect of developing novel niche-targeting therapies

Leukemic cells (LCs) arise from the hematopoietic stem/and progenitor cells (HSCs/HSPCs) and utilize cues from the bone marrow microenvironment (BMM) for their regulation in the same way as their normal HSC counterparts. Mesenchymal stromal cells (MSCs), a vital component of the BMM promote leukemogenesis by creating a protective and immune-tolerant microenvironment that can support the survival of LCs, helping them escape chemotherapy, thereby resulting in the relapse of leukemia. Conversely, MSCs also induce apoptosis in the LCs and inhibit their proliferation by interfering with their self-renewal potential. This review discusses the work done so far on cell-autonomous (intrinsic) and MSCs-mediated non-cell-autonomous (extrinsic) regulation of myeloid leukemia with a special focus on the need to investigate the extrinsic regulation of myeloid leukemia to understand the contrasting role of MSCs in leukemogenesis. These mechanisms could be exploited to formulate novel therapeutic strategies that specifically target the leukemic microenvironment.

Venetoclax with Hypomethylating Agents in Newly Diagnosed Acute Myeloid Leukemia: A Systematic Review and Meta-Analysis of Survival Data from Real-World Studies

In recent years, the association of venetoclax (VEN) with hypomethylating agents (HMAs) significantly improved the outcome of patients with newly diagnosed acute myeloid leukemia (AML) who were unfit for intensive chemotherapy and became the standard of care after the publication of the pivotal RCT VIALE-A. However, it is still not clear to what extent the results observed in the VIALE-A apply to a real-world setting. For this reason, we carried out a systematic review and meta-analysis of real-world studies on newly diagnosed patients with AML, ineligible for intensive induction chemotherapy, receiving first-line VEN+HMA. We then compared their results in term of survival with those from the VIALE-A. Kaplan-Meier curves were extracted from all included studies and individual survival data was reconstructed. We then estimated a pooled survival curve and compared it with the results of the VIALE-A using the log-rank test. We also conducted a secondary analysis including only studies considering VEN plus azacytidine (AZA) as treatment, as this was the schedule originally used in the VIALE-A. Nineteen real-world studies met the inclusion criteria and were included in the systematic review. Most of them reported a worse survival than the VIALE-A. The pooled survival curve was similar to that reported in the VIALE-A during the first three months of treatment but diverged thereafter (p-value = 0.0001). The pooled median survival among the real-world studies was 9.37 months (95%CI 8.81-10.5), substantially lower than that reported in the VIALE-A (14.7 months; 95%CI 11.9-18.7). Results slightly increased when the analysis was restricted to the studies using VEN+AZA as treatment (median survival: 11.5 months; 95%CI 10.2-14.8). Survival of newly diagnosed AML patients treated with VEN+HMAs in a real-world setting seems to be lower than previously reported in the VIALE-A, while the effect of VEN+AZA is more in line with expected results. Future studies are needed to evaluate whether this apparent discrepancy is due to the different characteristics of enrolled patients or to a non-optimal adherence to therapy, and whether alternative regimens can provide better results in terms of safety and effectiveness.

Treatment of older adults with FLT3-mutated AML: Emerging paradigms and the role of frontline FLT3 inhibitors

FLT3 is the most frequently mutated gene in acute myeloid leukemia (AML), with FLT3 internal tandem duplication (ITD) mutations being associated with a more aggressive clinical course. While two large, randomized clinical trials have shown a survival benefit with the frontline use of an oral FLT3 inhibitor (midostaurin or quizartinib) in patients with FLT3-mutated AML, the role of FLT3 inhibitors in older adults with newly diagnosed FLT3-mutated AML remains unclear. A definitive improvement in survival has not been observed in intensively treated patients over 60 years of age receiving frontline FLT3 inhibitors. Furthermore, many patients with FLT3-mutated AML are unsuitable for intensive chemotherapy due to age and/or comorbidities, and this population represents a particular unmet need. For these older patients who are unfit for intensive approaches, azacitidine + venetoclax is a new standard of care and is used by many clinicians irrespective of FLT3 mutation status. However, FLT3-ITD mutations confer resistance to venetoclax and are a well-established mechanism of relapse to lower-intensity venetoclax-based regimens, leading to short durations of remission and poor survival. Preclinical and clinical data suggest synergy between FLT3 inhibitors and venetoclax, providing rationale for their combination. Novel strategies to safely incorporate FLT3 inhibitors into the standard hypomethylating agent + venetoclax backbone are now being explored in this older, less fit population with newly diagnosed FLT3-mutated AML, with encouraging early results. Herein, we discuss the frontline use of FLT3 inhibitors in older adults with FLT3-mutated AML, including the potential role of FLT3 inhibitors in combination with intensive chemotherapy and as part of novel, lower-intensity doublet and triplet regimens in this older population.

Emerging small molecular inhibitors as targeted therapies for high-risk acute myeloid leukemias

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive disease which has traditionally been treated with intensive chemotherapy. Survival in patients with high-risk cytogenetic and molecular subsets has been poor with this approach due to suboptimal responses seen with intensive chemotherapy and due to many patients with higher risk disease being older and unable to tolerate intensive therapies. In recent years, several targeted therapies have been under investigation for patients with high-risk AML subsets.

AREAS COVERED

This review covers four different subsets of high-risk AML including TP53-mutated, KMT2A-rearranged, FLT3-mutated, and secondary AML developing after prior hypomethylating agent exposure. The research discussed in this review focuses on small molecule inhibitors that have been studied in the treatment of these high-risk AML subsets.

EXPERT OPINION

There are several small molecule inhibitors that have demonstrated promise in these high-risk AML subsets. Longer follow-up and ongoing investigation are needed to continue to optimize therapy for patients with high-risk AML.

An Overview of Targeted Therapies in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most aggressive adult leukemia, characterized by clonal differentiation arrest of progenitor or precursor hematopoietic cells. Intense preclinical and clinical research has led to regulatory approval of several targeted therapeutics, administered either as single agents or as combination therapies. However, the majority of patients still face a poor prognosis and disease relapse frequently occurs due to selection of therapy-resistant clones. Hence, more effective novel therapies, most likely as innovative, rational combination therapies, are urgently needed. Chromosomal aberrations, gene mutations, and epigenetic alterations drive AML pathogenesis but concurrently provide vulnerabilities to specifically target leukemic cells. Other molecules, either aberrantly active and/or overexpressed in leukemic stem cells, may also be leveraged for therapeutic benefit. This concise review of targeted therapies for AML treatment, which are either approved or are being actively investigated in clinical trials or recent preclinical studies, provides a flavor of the direction of travel, but also highlights the current challenges in AML treatment.

Older Adults With Newly Diagnosed AML: Hot Topics for the Practicing Clinician

Over the past decade, our understanding of AML pathogenesis and pathophysiology has improved significantly with mutational profiling. This has led to translational advances in therapeutic options, as there have been 10 new US Food and Drug Administration (FDA) approvals for AML therapies since 2017, half of which target specific driver mutations in FLT3, IDH1, or IDH2. These new agents have expanded the therapeutic armamentarium for AML, particularly for patients who are considered ineligible for intensive chemotherapy with anthracycline- and cytarabine-containing regimens. These new treatment options are relevant because the median age at diagnosis is 68 years, and outcomes for patients older than 60 years have historically been dismal. However, the optimal approach to incorporating novel agents into frontline regimens remains a clinical challenge, particularly with regard to sequencing of therapies, considering the role of allogeneic hematopoietic stem cell transplantation and managing toxicities.

How acute myeloid leukemia (AML) escapes from FMS-related tyrosine kinase 3 (FLT3) inhibitors? Still an overrated complication?

FMS-related tyrosine kinase 3 (FLT3) mutations, present in about 25%-30% of acute myeloid leukemia (AML) patients, constitute one of the most frequently detected mutations in these patients. The binding of FLT3L to FLT3 activates the phosphatidylinositol 3-kinase (PI3K) and RAS pathways, producing increased cell proliferation and the inhibition of apoptosis. Two types of FLT3 mutations exist: FLT3-ITD and FLT3-TKD (point mutations in D835 and I836 or deletion of codon I836). A class of drugs, tyrosine-kinase inhibitors (TKI), targeting mutated FLT3, is already available with 1^st and 2^nd generation molecules, but only midostaurin and gilteritinib are currently approved. However, the emergence of resistance or the selection of clones not responding to FLT3 inhibitors has become an important clinical dilemma, as the duration of clinical responses is generally limited to a few months. This review analyzes the insights into mechanisms of resistance to TKI and poses a particular view on the clinical relevance of this phenomenon. Has resistance been overlooked? Indeed, FLT3 inhibitors have significantly contributed to reducing the negative impact of FLT3 mutations on the prognosis of AML patients who are no longer considered at high risk by the European LeukemiaNet (ELN) 2022. Finally, several ongoing efforts to overcome resistance to FLT3-inhibitors will be presented: new generation FLT3 inhibitors in monotherapy or combined with standard chemotherapy, hypomethylating drugs, or IDH1/2 inhibitors, Bcl2 inhibitors; novel anti-human FLT3 monoclonal antibodies (e.g., FLT3/CD3 bispecific antibodies); FLT3-CAR T-cells; CDK4/6 kinase inhibitor (e.g., palbociclib).

Activity of eftozanermin alfa plus venetoclax in preclinical models and patients with acute myeloid leukemia

Activation of apoptosis in malignant cells is an established strategy for controlling cancer and is potentially curative. To assess the impact of concurrently inducing the extrinsic and intrinsic apoptosis-signaling pathways in acute myeloid leukemia (AML), we evaluated activity of the TRAIL receptor agonistic fusion protein eftozanermin alfa (eftoza; ABBV-621) in combination with the B-cell lymphoma protein-2 selective inhibitor venetoclax in preclinical models and human patients. Simultaneously stimulating intrinsic and extrinsic apoptosis-signaling pathways with venetoclax and eftoza, respectively, enhanced their activities in AML cell lines and patient-derived ex vivo/in vivo models. Eftoza activity alone or plus venetoclax required death receptor 4/5 (DR4/DR5) expression on the plasma membrane but was independent of TP53 or FLT3-ITD status. The safety/tolerability of eftoza as monotherapy and in combination with venetoclax was demonstrated in patients with relapsed/refractory AML in a phase 1 clinical trial. Treatment-related adverse events were reported in 2 of 4 (50%) patients treated with eftoza monotherapy and 18 of 23 (78%) treated with eftoza plus venetoclax. An overall response rate of 30% (7/23; 4 complete responses [CRs], 2 CRs with incomplete hematologic recovery, and 1 morphologic leukemia-free state) was reported in patients who received treatment with eftoza plus venetoclax and 67% (4/6) in patients with myoblasts positive for DR4/DR5 expression; no tumor responses were observed with eftoza monotherapy. These data indicate that combination therapy with eftoza plus venetoclax to simultaneously activate the extrinsic and intrinsic apoptosis-signaling pathways may improve clinical benefit compared with venetoclax monotherapy in relapsed/refractory AML with an acceptable toxicity profile. This trial was registered at www.clinicaltrials.gov as #NCT03082209.

Targeting FLT3 Mutation in Acute Myeloid Leukemia: Current Strategies and Future Directions

FLT3 mutations are present in 30% of newly diagnosed patients with acute myeloid leukemia. Two broad categories of FLT3 mutations are ITD and TKD, with the former having substantial clinical significance. Patients with FLT3-ITD mutation present with a higher disease burden and have inferior overall survival, due to high relapse rates after achieving remission. The development of targeted therapies with FLT3 inhibitors over the past decade has substantially improved clinical outcomes. Currently, two FLT3 inhibitors are approved for use in patients with acute myeloid leukemia: midostaurin in the frontline setting, in combination with intensive chemotherapy; and gilteritinib as monotherapy in the relapsed refractory setting. The addition of FLT3 inhibitors to hypomethylating agents and venetoclax offers superior responses in several completed and ongoing studies, with encouraging preliminary data. However, responses to FLT3 inhibitors are of limited duration due to the emergence of resistance. A protective environment within the bone marrow makes eradication of FLT3^mut leukemic cells difficult, while prior exposure to FLT3 inhibitors leads to the development of alternative FLT3 mutations as well as activating mutations in downstream signaling, promoting resistance to currently available therapies. Multiple novel therapeutic strategies are under investigation, including BCL-2, menin, and MERTK inhibitors, as well as FLT3-directed BiTEs and CAR-T therapy.

Hypomethylating agent-based therapies in older adults with acute myeloid leukemia - A joint review by the Young International Society of Geriatric Oncology and European Society for Blood and Marrow Transplantation Trainee Committee

Acute myeloid leukemia (AML) is associated with poor outcomes in older adults. A major goal of treatment is to balance quality of life and functional independence with disease control. With the approval of new, more tolerable regimens, more older adults are able to receive AML-directed therapy. Among these options are hypomethylating agents (HMAs), specifically azacitidine and decitabine. HMAs have become an integral part of AML therapy over the last two decades. These agents are used either as monotherapy or nowadays more commonly in combination with other agents such as the Bcl-2 inhibitor venetoclax. Biological AML characteristics, such as molecular and cytogenetic risk factors, play crucial roles in guiding treatment decisions. In patients with high-risk AML, HMAs are increasingly used rather than intensive chemotherapy, although further trials based on a risk-adapted approach using patient- and disease-related factors are needed. Here, we review trials and evidence for the use of HMA monotherapy and combination therapy in the management of older adults with AML. Furthermore, we discuss the use of HMAs and HMA combination therapies in AML, mechanisms of action, their incorporation into hematopoietic stem cell transplantation strategies, and their use in patients with comorbidities and reduced organ function.

Recent advances in targeted therapies in acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common acute leukemia in adults. While survival for younger patients over the last several decades has improved nearly sixfold with the optimization of intensive induction chemotherapy and allogeneic stem cell transplantation (alloHSCT), this effect has been largely mitigated in older and less fit patients as well as those with adverse-risk disease characteristics. However, the last 10 years has been marked by major advances in the molecular profiling of AML characterized by a deeper understanding of disease pathobiology and therapeutic vulnerabilities. In this regard, the classification of AML subtypes has recently evolved from a morphologic to a molecular and genetic basis, reflected by recent updates from the World Health Organization and the new International Consensus Classification system. After years of stagnation in new drug approvals for AML, there has been a rapid expansion of the armamentarium against this disease since 2017. Low-intensity induction therapy with hypomethylating agents and venetoclax has substantially improved outcomes, including in those previously considered to have a poor prognosis. Furthermore, targeted oral therapies against driver mutations in AML have been added to the repertoire. But with an accelerated increase in treatment options, several questions arise such as how to best sequence therapy, how to combine therapies, and if there is a role for maintenance therapy in those who achieve remission and cannot undergo alloHSCT. Moreover, certain subtypes of AML, such as those with TP53 mutations, still have dismal outcomes despite these recent advances, underscoring an ongoing unmet need and opportunity for translational advances. In this review, we will discuss recent updates in the classification and risk stratification of AML, explore the literature regarding low-intensity and novel oral combination therapies, and briefly highlight investigative agents currently in early clinical development for high-risk disease subtypes.

Progress toward Better Treatment of Therapy-Related AML

Therapy-related acute myeloid leukemia (t-AML) comprises 10-20% of all newly diagnosed cases of AML and is related to previous use of chemotherapy or ionizing radiotherapy for an unrelated malignant non-myeloid disorder or autoimmune disease. Classic examples include alkylating agents and topoisomerase II inhibitors, whereas newer targeted therapies such as poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors have emerged as causative agents. Typically, t-AML is characterized by adverse karyotypic abnormalities and molecular lesions that confer a poor prognosis. Nevertheless, there are also cases of t-AML without poor-risk features. The management of these patients remains controversial. We describe the causes and pathophysiology of t-AML, putting emphasis on its mutational heterogeneity, and present recent advances in its treatment including CPX-351, hypomethylating agent plus venetoclax combination, and novel, molecularly targeted agents that promise to improve the cure rates. Evidence supporting personalized medicine for patients with t-AML is presented, as well as the authors' clinical recommendations.

Molecularly Targeted Therapy in Acute Myeloid Leukemia: Current Treatment Landscape and Mechanisms of Response and Resistance

Treatment for acute myeloid leukemia (AML) has evolved rapidly over the last decade as improved understanding of cytogenetic and molecular drivers of leukemogenesis refined survival prognostication and enabled development of targeted therapeutics. Molecularly targeted therapies are now approved for the treatment of FLT3 and IDH1/2-mutated AML and additional molecularly and cellularly targeted therapeutics are in development for defined patient subgroups. Alongside these welcome therapeutic advancements, increased understanding of leukemic biology and treatment resistance has resulted in clinical trials investigating combinations of cytotoxic, cellular, and molecularly targeted therapeutics resulting in improved response and survival outcomes in patients with AML. Herein, we comprehensively review the current landscape of IDH and FLT3 inhibitors in clinical practice for the treatment of AML, highlight known resistance mechanisms, and discuss new cellular or molecularly targeted therapies currently under investigation in ongoing early phase clinical trials.

Real-World Experience of Adults With Acute Myeloid Leukemia on Hypomethylating Agents With or Without Venetoclax at a Comprehensive Cancer Center

Background

Venetoclax (VEN) in combination with hypomethylating agent (HMA) therapy is a standard treatment option for patients with newly diagnosed acute myeloid leukemia (AML); however, data are limited in the relapsed or refractory (R/R) populations and in those with poor-risk disease. A retrospective review was conducted involving patients with AML who received HMA alone or in combination with VEN (VEN + HMA).

Methods

VEN + HMA was compared to HMA alone in first-line and R/R settings. Patients were stratified by specific HMA and line of therapy. The primary endpoint was overall response rate (ORR) up to 6 months from start of treatment.

Results

Fifty-two patients were evaluated for efficacy and 78 patients for safety. ORR was 67% (VEN + HMA) versus 80% (HMA) in the first line and 50% versus 22% in R/R setting. A greater clinical benefit was seen with VEN + HMA compared to HMA in both lines of therapy (first-line: 87% vs. 80%; R/R: 75% vs. 67%). The median duration of response was longer with VEN + HMA first-line, but shorter in the R/R setting compared to HMA (8.3 vs. 7.2 months and 2.5 vs. 3.7 months, respectively). Of the 32 patients who responded to therapy, 63% had a complex karyotype. Survival benefits were greater with VEN + HMA in both lines of therapy, although not statistically significant. Grade 3/4 neutropenia was reported in all patients receiving VEN, and 95% of these patients also experienced grade 3/4 thrombocytopenia. There were three cases of tumor lysis syndrome.

Conclusion

The addition of VEN to HMA has consistently shown benefit as first-line treatment and may have some benefit in R/R settings as well. Further studies are needed to compare across various lines of treatment and unfavorable disease. Dynamic strategies that improve toxicity management should be considered.

The Cup Runneth Over: Treatment Strategies for Newly Diagnosed Acute Myeloid Leukemia

Since 2017, the number of agents for acute myeloid leukemia (AML) has rapidly expanded. Given the increased therapeutic options, better identification of high-risk subsets of AML and more refined approaches to patient fitness assessment, the decisions surrounding selection of intensive chemotherapy versus lower-intensity treatment have grown increasingly more nuanced. In this review, we present available data for both standard and investigational approaches in the initial treatment of AML using an intensive chemotherapy backbone or a lower-intensity approach. We summarize management strategies in newly diagnosed secondary AML, considerations around allogeneic stem-cell transplantation, and the role of maintenance therapy. Finally, we highlight important areas of future investigation and novel agents that may hold promise in combination with standard therapies.

FMS-Like Tyrosine Kinase 3 Inhibitors in the Treatment of Acute Myeloid Leukemia: An Update on the Emerging Evidence and Safety Profile

FMS-like tyrosine kinase 3 (FLT3) is one of the most frequently mutated genes in acute myeloid leukemia (AML). Approximately 30% of the adult cases harbor an internal tandem duplication (FLT3-ITD) and 5-10% a tyrosine kinase domain (TKD) amino acid substitution (FLT3-TKD). The treatment paradigm of AML patients harboring FLT3 mutations (30%) has been modified by the discovery of tyrosine kinase inhibitors. First- and second-generation inhibitors classify FLT3 inhibitors according to FLT3 specificity: first-generation FLT3 inhibitors include sorafenib and midostaurin and second-generation inhibitors are represented by quizartinib, gilteritinib and crenolanib, among others. Activity of these inhibitors depends on their mechanism of receptor binding (active vs inactive conformation) and efficacy against the FLT3-ITD and -TKD mutations (type 1 inhibitors are active both on FLT3-ITD and TKD, whereas type 2 inhibitors are active only on FLT3-ITD). The FLT3 inhibitors sorafenib, midostaurin, quizartinib and gilteritinib have been tested in monotherapy in several settings including refractory or relapsed AML (R/R AML), post-transplant maintenance as well as in combination with intensive chemotherapy (ICT) or non-intensity regimens. The results of published randomized studies support the use of sorafenib in a post-transplant setting (SORMAIN trial), midostaurin in combination with ICT based (RATIFY trial) and gilteritinib for R/R AML (ADMIRAL trial). Gilteritinib in combination with hypomethylating agent as well as quizartinib are not supported by solid randomized trial results for their use in FLT3-mutated AML patients.

Acute myeloid leukemia resistant to venetoclax-based therapy: What does the future hold?

Venetoclax is a highly selective B-cell lymphoma-2 (BCL-2) inhibitor, which, combined with a DNA hypomethylating agent or low dose cytarabine, results in high rates of initial responses in patients with acute myeloid leukemia (AML). However, the disease relapses in most patients. Mechanisms of resistance to venetoclax-based therapy include TP53 gene mutations or inactivation of p53 protein, activating kinase mutations such as FLT3 and RAS, and upregulation of other BCL-2 family apoptotic proteins. Current clinical trials are exploring strategies such as doublet or triplet regimens incorporating a p53 activator, an anti-CD47 antibody, or other novel agents that target genes and proteins responsible for resistance to venetoclax. Further studies should focus on identifying predictive biomarkers of response to venetoclax-based therapy and incorporating immunotherapeutic approaches such as checkpoint inhibitors, bispecific antibodies, antibody-drug conjugates, and CAR T-cell therapy to improve outcomes for patients with AML.

Therapeutic Targeting of FLT3 in Acute Myeloid Leukemia: Current Status and Novel Approaches

FMS-like tyrosine kinase 3 (FLT3) is mutated in approximately 30% of acute myeloid leukemia (AML) patients. The presence of FLT3-ITD (internal tandem duplication, 20-25%) mutation and, to a lesser extent, FLT3-TKD (tyrosine kinase domain, 5-10%) mutation is associated with poorer diagnosis and therapy response since the leukemic cells become hyperproliferative and resistant to apoptosis after continuous activation of FLT3 signaling. Targeting FLT3 has been the focus of many pre-clinical and clinical studies. Hence, many small-molecule FLT3 inhibitors (FLT3is) have been developed, some of which are approved such as midostaurin and gilteritinib to be used in different clinical settings, either in combination with chemotherapy or alone. However, many questions regarding the best treatment strategy remain to be answered. On the other hand, various FLT3-dependent and -independent resistance mechanisms could be evolved during FLT3i therapy which limit their clinical impact. Therefore, identifying molecular mechanisms of resistance and developing novel strategies to overcome this obstacle is a current interest in the field. In this review, recent studies of approved FLT3i and knowledge about major resistance mechanisms of clinically approved FLT3i's will be discussed together with novel treatment approaches such as designing novel FLT3i and dual FLT3i and combination strategies including approved FLT3i plus small-molecule agents targeting altered molecules in the resistant cells to abrogate resistance. Moreover, how to choose an appropriate FLT3i for the patients will be summarized based on what is currently known from available clinical data. In addition, strategies beyond FLT3i's including immunotherapeutics, small-molecule FLT3 degraders, and flavonoids will be summarized to highlight potential alternatives in FLT3-mutated AML therapy.

The Growing Role of the BH3 Mimetic Drug Venetoclax in the Therapy of Acute Myeloid Leukemia

Despite recent progress, acute myeloid leukemia (AML) remains a disease associated with poor prognosis, particularly in older AML patients unfit to tolerate intensive chemotherapy treatment. The development and introduction in the therapy of Venetoclax (VEN), a potent BH3 mimetic targeting the antiapoptotic protein BCL-2, inducing apoptosis of leukemic cells, has shown to be a promising treatment for newly diagnosed, relapsed, and refractory AML patients ineligible for induction chemotherapy. Combination treatments using Ventoclax and a hypomethylating agent (azacitidine or decitabine) or low-intensity chemotherapy have shown in newly diagnosed patients variable response rates, with highly responsive patients with NPM1, IDH1-IDH2, TET2, and RUNX1 mutations and with scarcely responsive patients with FLT3, TP53 and ASXL1 mutations, complex karyotypes, and secondary AMLs. Patients with refractory/relapsing disease are less responsive to Venetoclax-based regimens. However, in the majority of patients, the responses have only a limited duration, and the development of resistance is frequently observed. Therefore, understanding the resistance mechanisms is crucial for developing new strategies and identifying rational drug combination regimens. In this context, two strategies seem to be promising: (i) triplet therapies based on the combined administration of Venetoclax, a hypomethylating agent (or low-dose chemotherapy), and an agent targeting a specific genetic alteration of leukemic cells (i.e., FLT3 inhibitors in FLT3-mutated AMLs) or an altered signaling pathway; (ii) combination therapies based on the administration of two BH3 mimetics (i.e., BCL-2 +MCL-1 mimetics) and a hypomethylating agent.

Overcoming Resistance: FLT3 Inhibitors Past, Present, Future and the Challenge of Cure

FLT3 ITD and TKD mutations occur in 20% and 10% of Acute Myeloid Leukemia (AML), respectively, and they represent the target of the first approved anti-leukemic therapies in the 2000s. Type I and type II FLT3 inhibitors (FLT3i) are active against FLT3 TKD/ITD and FLT3 ITD mutations alone respectively, but they still fail remissions in 30-40% of patients due to primary and secondary mechanisms of resistance, with variable relapse rate of 30-50%, influenced by NPM status and FLT3 allelic ratio. Mechanisms of resistance to FLT3i have recently been analyzed through NGS and single cell assays that have identified and elucidated the polyclonal nature of relapse in clinical and preclinical studies, summarized here. Knowledge of tumor escape pathways has helped in the identification of new targeted drugs to overcome resistance. Immunotherapy and combination or sequential use of BCL2 inhibitors and experimental drugs including aurora kinases, menin and JAK2 inhibitors will be the goal of present and future clinical trials, especially in patients with FLT3-mutated (FLT3mut) AML who are not eligible for allogeneic transplantation.

Machine Learning–Based Exploratory Clinical Decision Support for Newly Diagnosed Patients With Acute Myeloid Leukemia Treated With 7 + 3 Type Chemotherapy or Venetoclax/Azacitidine

PURPOSE

There are currently limited objective criteria to help assist physicians in determining whether an individual patient with acute myeloid leukemia (AML) is likely to do better with induction with either standard 7 + 3 chemotherapy or targeted therapy with venetoclax plus azacitidine. The study goal was to address this need by developing exploratory clinical decision support methods.

PATIENTS AND METHODS

Univariable and multivariable analysis as well as comparison of a range of machine learning (ML) predictors were performed using cohorts of 120 newly diagnosed 7 + 3-treated AML patients compared with 101 venetoclax plus azacitidine–treated patients.

RESULTS

A variety of features in the two patient cohorts were identified that may potentially correlate with short- and long-term outcomes, toxicities, and other considerations. A subset of these diagnostic features was then used to develop ML-based predictors with relatively high areas under the curve of short- and long-term outcomes, hospital stays, transfusion requirements, and toxicities for individual patients treated with either venetoclax/azacitidine or 7 + 3.

CONCLUSION

Potential ML-based approaches to clinical decision support to help guide individual patients with newly diagnosed AML to either 7 + 3 or venetoclax plus azacitidine induction therapy were identified. Larger cohorts with separate test and validation studies are necessary to confirm these initial findings.

Current status and future perspectives in targeted therapy of NPM1-mutated AML

Nucleophosmin 1 (NPM1) is a nucleus-cytoplasmic shuttling protein which is predominantly located in the nucleolus and exerts multiple functions, including regulation of centrosome duplication, ribosome biogenesis and export, histone assembly, maintenance of genomic stability and response to nucleolar stress. NPM1 mutations are the most common genetic alteration in acute myeloid leukemia (AML), detected in about 30–35% of adult AML and more than 50% of AML with normal karyotype. Because of its peculiar molecular and clinico-pathological features, including aberrant cytoplasmic dislocation of the NPM1 mutant and wild-type proteins, lack of involvement in driving clonal hematopoiesis, mutual exclusion with recurrent cytogenetic abnormalities, association with unique gene expression and micro-RNA profiles and high stability at relapse, NPM1-mutated AML is regarded as a distinct genetic entity in the World Health Organization (WHO) classification of hematopoietic malignancies. Starting from the structure and functions of NPM1, we provide an overview of the potential targeted therapies against NPM1-mutated AML and discuss strategies aimed at interfering with the oligomerization (compound NSC348884) and the abnormal traffic of NPM1 (avrainvillamide, XPO1 inhibitors) as well as at inducing selective NPM1-mutant protein degradation (ATRA/ATO, deguelin, (-)-epigallocatechin-3-gallate, imidazoquinoxaline derivatives) and at targeting the integrity of nucleolar structure (actinomycin D). We also discuss the current therapeutic results obtained in NPM1-mutated AML with the BCL-2 inhibitor venetoclax and the preliminary clinical results using menin inhibitors targeting HOX/MEIS1 expression. Finally, we review various immunotherapeutic approaches in NPM1-mutated AML, including immune check-point inhibitors, CAR and TCR T-cell-based therapies against neoantigens created by the NPM1 mutations.

Targeting Acute Myeloid Leukemia with Venetoclax; Biomarkers for Sensitivity and Rationale for Venetoclax-Based Combination Therapies

Simple Summary

Venetoclax has proven to be a promising therapy for newly diagnosed, relapsed and refractory AML patients ineligible for induction chemotherapy. Current ongoing clinical trials are evaluating its effectivity as frontline therapy for all acute myeloid leukemia (AML) patients. However, response rates vary wildly, depending on patient characteristics and mutational profiles. This review elaborates on the efficacy and safety of venetoclax compared to conventional chemotherapy for treatment of AML patients, comparing the response rates, overall survival and adverse events. Moreover, it gives an overview of genetic and epigenetic AML cell characteristics that give enhanced or decreased response to venetoclax and offers insights into the pathogenesis of venetoclax sensitivity and resistance. Additionally, it suggests possible treatment combinations predicted to be successful based on identified mechanisms influencing venetoclax sensitivity of AML cells.

Abstract

Venetoclax is a BCL-2 inhibitor that effectively improves clinical outcomes in newly diagnosed, relapsed and refractory acute myeloid leukemia (AML) patients, with complete response rates (with and without complete blood count recovery) ranging between 34–90% and 21–33%, respectively. Here, we aim to give an overview of the efficacy of venetoclax-based therapy for AML patients, as compared to standard chemotherapy, and on factors and mechanisms involved in venetoclax sensitivity and resistance in AML (stem) cells, with the aim to obtain a perspective of response biomarkers and combination therapies that could enhance the sensitivity of AML cells to venetoclax. The presence of molecular aberrancies can predict responses to venetoclax, with a higher response in NPM1-, IDH1/2-, TET2- and relapsed or refractory RUNX1-mutated AML. Decreased sensitivity to venetoclax was observed in patients harboring FLT3-ITD, TP53, K/NRAS or PTPN11 mutations. Moreover, resistance to venetoclax was observed in AML with a monocytic phenotype and patients pre-treated with hypomethylating agents. Resistance to venetoclax can arise due to mutations in BCL-2 or pro-apoptotic proteins, an increased dependency on MCL-1, and usage of additional/alternative sources for energy metabolism, such as glycolysis and fatty acid metabolism. Clinical studies are testing combination therapies that may circumvent resistance, including venetoclax combined with FLT3- and MCL-1 inhibitors, to enhance venetoclax-induced cell death. Other treatments that can potentially synergize with venetoclax, including MEK1/2 and mitochondrial complex inhibitors, need to be evaluated in a clinical setting.

Shall We Dance: Evolving Partnerships of Targeted Therapies for AML

Two publications detailing the clinical outcomes of patients with acute myeloid leukemia and mutations in IDH1, IDH2, or FLT3 who received initial therapy with venetoclax and azacitidine provide new insights into risk stratification and set the stage for future trials integrating molecularly targeted therapy with this new standard regimen. See related articles by Konopleva et al., p. 2744 and Pollyea et al., p. 2753.

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.

Older Patients with Acute Myeloid Leukemia Deserve Individualized Treatment

PURPOSE OF REVIEW

Treatment of elderly patients with acute myeloid leukemia is a known challenge for hematologists due to patient diversity, heterogeneous disease biology, and a rapidly evolving treatment landscape. Here, we highlight the importance of determining fitness, review the latest therapeutic developments, and discuss clinical scenarios to provide guidance on individualized treatment for older AML patients.

RECENT FINDINGS

Several factors, like age, performance status, and comorbidities, play a role in fitness and are associated with outcome. Comorbidity scoring systems and geriatric assessments are tools to help physicians select the most appropriate treatment for each patient. The addition of venetoclax, targeted therapy with IDH1/2 and FLT3 inhibitors, and enhanced formulas of existing drugs like CPX-351 and oral azacitidine have improved responses and outcomes. New drugs and combination therapies have increased the therapeutic options for elderly AML patients but determination of fitness and disease biology is essential to select patient-tailored treatments.