Management of toxicities associated with targeted therapies for acute myeloid leukemia: when to push through and when to stop

In silico and in vitro study of FLT3 inhibitors and their application in acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common hematological cancer in the adult population worldwide. Approximately 35% of patients with AML present internal tandem duplication (ITD) mutations in the FMS‑like tyrosine kinase 3 (FLT3) receptor associated with poor prognosis, and thus, this receptor is a relevant target for potential therapeutics. Tyrosine kinase inhibitors (TKIs) are used to treat AML; however, their molecular interactions and effects on leukemic cells are poorly understood. The present study aimed to gain insights into the molecular interactions and affinity forces of four TKI drugs (sorafenib, midostaurin, gilteritinib and quizartinib) with the wild‑type (WT)‑FLT3 and ITD‑mutated (ITD‑FLT3) structural models of FLT3, in its inactive aspartic acid‑phenylalanine‑glycine motif (DFG‑out) and active aspartic acid‑phenylalanine‑glycine motif (DFG‑in) conformations. Furthermore, the present study evaluated the effects of the second‑generation TKIs gilteritinib and quizartinib on cancer cell viability, apoptosis and proliferation in the MV4‑11 (ITD‑FLT3) and HL60 (WT‑FLT3) AML cell lines. Peripheral blood mononuclear cells (PBMCs) from a healthy volunteer were included as an FLT3‑negative group. Molecular docking analysis indicated higher affinities of second‑generation TKIs for WT‑FLT3/DFG‑out and WT‑FLT3/DFG‑in compared with those of the first‑generation TKIs. However, the ITD mutation changed the affinity of all TKIs. The in vitro data supported the in silico predictions: MV4‑11 cells presented high selective sensibility to gilteritinib and quizartinib compared with the HL60 cells, whereas the drugs had no effect on PBMCs. Thus, the current study presented novel information about molecular interactions between the FLT3 receptors (WT or ITD‑mutated) and some of their inhibitors. It also paves the way for the search for novel inhibitory molecules with potential use against AML.

Promising Therapeutic Strategies for Hematologic Malignancies: Innovations and Potential

In this review we explore innovative approaches in the treatment of hematologic cancers by combining various therapeutic modalities. We discuss the synergistic potential of combining inhibitors targeting different cellular pathways with immunotherapies, molecular therapies, and hormonal therapies. Examples include combining PI3K inhibitors with proteasome inhibitors, NF-κB inhibitors with immunotherapy checkpoint inhibitors, and neddylation inhibitors with therapies targeting the tumor microenvironment. Additionally, we discuss the potential use of small molecules and peptide inhibitors in hematologic cancer treatment. These multidimensional therapeutic combinations present promising strategies for enhancing treatment efficacy and overcoming resistance mechanisms. However, further clinical research is required to validate their effectiveness and safety profiles in hematologic cancer patients.

Top Ten Tips Palliative Care Clinicians Should Know About Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults. Rapidly proliferating leukemic cells cause symptoms and increase the risk of infection. While individuals may initially benefit from supportive measures, disease-directed therapy may ultimately be required for symptom management, even at the end of life, although this may also inadvertently increase symptom burden. This unpredictable illness trajectory complicates prognostic uncertainty and the timing of hospice referral, which may prohibit access to palliative therapies and lead to recurrent hospitalizations. However, emerging evidence demonstrates that early palliative care (PC) integration with standard leukemia care results in improved quality of life, psychological outcomes, and greater participation in advance care planning. To orient PC clinicians asked to care for patients with AML, this article highlights 10 salient considerations.

Advancements and Challenges in the Treatment of AML

The therapeutic arsenal for the management of AML has expanded significantly in recent years. Before 2017, newly diagnosed AML was treated with either standard cytarabine- and anthracycline-based induction chemotherapy (for all fit patients) or a single-agent hypomethylating agent (in unfit patients or those 75 years and older). While assessing patient fitness remains important, characterizing the disease biology has become critical to select the optimal initial therapy for each patient with more options available. FLT3 inhibitors, gemtuzumab ozogamicin, and CPX-351 have been shown to improve outcomes for specific subsets of patients. Venetoclax (VEN) with a hypomethylating agent (HMA) is the standard-of-care frontline regimen for most older patients, except perhaps for those with an IDH1 mutation where ivosidenib with azacitidine may also be considered. On the basis of the success seen with HMA/VEN in older patients, there is now increasing interest in incorporating VEN into frontline regimens in younger patients, with promising data from multiple early phase studies. This article focuses on recent updates and ongoing challenges in the management of AML, with a particular focus on the ongoing challenge of secondary AML and considerations regarding the selection of initial therapy in younger patients. An overview of common side effects and toxicities associated with targeted therapies is also presented here, along with recommended strategies to mitigate these risks.

Synergy and antagonism between azacitidine and FLT3 inhibitors

Synergetic interactions between drugs can make a drug combination more effective. Alternatively, they may allow to use lower concentrations and thus avoid toxicities or side effects that not only cause discomfort but might also reduce the overall survival. Here, we studied whether synergy exists between agents that are used for treatment of acute myeloid leukaemia (AML). Azacitidine is a demethylation agent that is used in the treatment of AML patients that are unfit for aggressive chemotherapy. An activating mutation in the FLT3 gene is common in AML patients and in the absence of specific treatment makes prognosis worse. FLT3 inhibitors may be used in such cases. We sought to determine whether combination of azacitidine with a FLT3 inhibitor (gilteritinib, quizartinib, LT-850-166, FN-1501 or FF-10101) displayed synergy or antagonism. To this end, we calculated dose-response matrices of these drug combinations from experiments in human AML cells and subsequently analysed the data using a novel consensus scoring algorithm. The results show that combinations that involved non-covalent FLT3 inhibitors, including the two clinically approved drugs gilteritinib and quizartinib were antagonistic. On the other hand combinations with the covalent inhibitor FF-10101 had some range of concentrations where synergy was observed.

Combating Acute Myeloid Leukemia via Sphingosine Kinase 1 Inhibitor-Nanomedicine Combination Therapy with Cytarabine or Venetoclax

MP-A08 is a novel sphingosine kinase 1 (SPHK1) inhibitor with activity against acute myeloid leukemia (AML). A rationally designed liposome-based encapsulation and delivery system has been shown to overcome the physicochemical challenges of MP-A08 and enable its effective delivery for improved efficacy and survival of mice engrafted with human AML in preclinical models. To establish therapies that overcome AML's heterogeneous nature, here we explored the combination of MP-A08-loaded liposomes with both the standard chemotherapy, cytarabine, and the targeted therapy, venetoclax, against human AML cell lines. Cytarabine (over the dose range of 0.1-0.5 µM) in combination with MP-A08 liposomes showed significant synergistic effects (as confirmed by the Chou-Talalay Combination Index) against the chemosensitised human AML cell lines MV4-11 and OCI-AML3. Venetoclax (over the dose range of 0.5-250 nM) in combination with MP-A08 liposomes showed significant synergistic effects against the chemosensitised human AML cell lines, particularly in venetoclax-resistant human AML cells. This strong synergistic effect is due to multiple mechanisms of action, i.e., inhibiting MCL-1 through SPHK1 inhibition, leading to ceramide accumulation, activation of protein kinase R, ATF4 upregulation, and NOXA activation, ultimately resulting in MCL-1 degradation. These combination therapies warrant further consideration and investigation in the search for a more comprehensive treatment strategy for AML.

Real-Life Multicenter Experience of Venetoclax in Combination with Hypomethylating Agents in Previously Untreated Adult Patients with Acute Myeloid Leukemia in Greece

BACKGROUND

The landscape of first-line treatment for acute myeloid leukemia (AML) patients ineligible for intensive chemotherapy has changed remarkably after venetoclax approval. Accumulating real-world data further apprises us with more knowledgeable use. To assess the efficacy and safety challenges in the real-life setting of the combination of hypomethylated agent (HMA) and venetoclax, we conducted a multi-center retrospective study.

METHODS

Forty adult AML patients treated with the combination of HMA and venetoclax as a first-line treatment after full approval (2020) were included. To confirm VIALE-A results, this group was compared to a historical cohort of 17 chemotherapy-ineligible AML patients treated with HMA monotherapy before 2020.

RESULTS

The combination of HMA-venetoclax achieved a composite complete response rate of 86.8% (p < 0.001), median overall survival, and event-free survival of 33.8 and 19.7 months, respectively, in a median follow-up of 17.8 months (pos < 0.001, HR = 0.276, CI: 0.132-0.575, pEFS = 0.004, HR = 0.367, CI: 0.174-0.773). High rates of neutropenia (90%) and consequent infection rates (57.5%) were noted. Only 55% of our patients received antifungal prophylaxis, as its use remains controversial, and invasive fungal infections were presented in 7.5%.

CONCLUSIONS

Evidently, venetoclax-HMA yields high response rates and profound survival benefits in real life and has changed our approach to alternative chemotherapy options.

Treatment of Acute Myeloid Leukemia in Older Adults

Acute Myeloid Leukemia (AML) is an aggressive myeloid malignancy predominantly affecting older adults. Despite the advancements in new therapies for AML, older and medically unfit patients continue to suffer from poor outcomes due to disease-related factors such as the mutational profile and patient-related factors such as comorbidities and performance status. In this review, we discuss a spectrum of therapeutic options for older patients with AML starting with a historical perspective and ending with therapies being investigated in clinical trials. We review the standard of care treatment options including combination venetoclax and hypomethylating agents, in addition to targeted therapies such as FLT3 and IDH inhibitors. Lastly, we shed light on challenges facing the care of older adults and their representation in clinical trials.

Prophylactic or pre-emptive therapies to prevent relapse after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation is a potent curative treatment for hematological malignancies, but relapse is still a major problem. Donor lymphocyte infusion (DLI) and maintenance therapies after transplantation are promising strategies to reduce the risk of relapse. DLI augments the graft-versus-tumor effect by directly adding allo-reactive donor lymphocytes, and has been used in relapsed patients. In this Progress in Hematology (PIH), we will focus on prophylactic or pre-emptive DLI, including DLI from a haploidentical donor. On the other hand, specific drugs, which are used in maintenance therapies for each disease, kill tumor cells directly and/or immunologically by stimulating immune cells. Maintenance therapies should be started early after transplantation without severe myelosuppression. Molecularly targeted drugs are therefore suitable for use in maintenance therapies, and are reviewed in this PIH. The optimal application of these strategies has not yet been established. However, important evidence regarding their efficacies, adverse events, and effects on immune systems is accumulating, and could help to improve outcomes in allogeneic transplantation.

Cardio-oncology and transplantation for acute myeloid leukemia

Despite the rapidly evolving treatment landscape for acute myeloid leukemia (AML), allogeneic hematopoietic cell transplantation (allo-HCT) remains an important and potentially curative treatment option for many high-risk AML patients. Cardiovascular disease is an important competing risk throughout allo-HCT and a key driver of morbidity and mortality long after treatment. Cardio-oncology is a new discipline in cardiology which provides multidisciplinary care and expertise to complex cancer patients with the aims of optimizing cardiovascular health plus monitoring and treating potential cardiotoxicity related to cancer treatments. As allogeneic HCT techniques get more sophisticated there will be an increase in transplant eligible older patients with a rise in comorbidities including established cardiovascular disease highlighting the need for close collaboration with cardio-oncology specialists from the time of diagnosis through late survivorship.

Heightened apoptotic priming of vascular cells across tissues and life span predisposes them to cancer therapy-induced toxicities

Although major organ toxicities frequently arise in patients treated with cytotoxic or targeted cancer therapies, the mechanisms that drive them are poorly understood. Here, we report that vascular endothelial cells (ECs) are more highly primed for apoptosis than parenchymal cells across many adult tissues. Consequently, ECs readily undergo apoptosis in response to many commonly used anticancer agents including cytotoxic and targeted drugs and are more sensitive to ionizing radiation and BH3 mimetics than parenchymal cells in vivo. Further, using differentiated isogenic human induced pluripotent stem cell models of ECs and vascular smooth muscle cells (VSMCs), we find that these vascular cells exhibit distinct drug toxicity patterns, which are linked to divergent therapy-induced vascular toxicities in patients. Collectively, our results demonstrate that vascular cells are highly sensitive to apoptosis-inducing stress across life span and may represent a "weakest link" vulnerability in multiple tissues for development of toxicities.

An Enzymatically Cleavable Tripeptide Linker for Maximizing the Therapeutic Index of Antibody-Drug Conjugates

Valine-citrulline is a protease-cleavable linker commonly used in many drug delivery systems, including antibody-drug conjugates (ADC) for cancer therapy. However, its suboptimal in vivo stability can cause various adverse effects such as neutropenia and hepatotoxicity, leading to dose delays or treatment discontinuation. Here, we report that glutamic acid-glycine-citrulline (EGCit) linkers have the potential to solve this clinical issue without compromising the ability of traceless drug release and ADC therapeutic efficacy. We demonstrate that our EGCit ADC resists neutrophil protease-mediated degradation and spares differentiating human neutrophils. Notably, our anti-HER2 ADC shows almost no sign of blood and liver toxicity in healthy mice at 80 mg kg-1. In contrast, at the same dose level, the FDA-approved anti-HER2 ADCs Kadcyla and Enhertu show increased levels of serum alanine aminotransferase and aspartate aminotransferase and morphologic changes in liver tissues. Our EGCit conjugates also exert greater antitumor efficacy in multiple xenograft tumor models compared with Kadcyla and Enhertu. This linker technology could substantially broaden the therapeutic windows of ADCs and other drug delivery agents, providing clinical options with improved efficacy and safety.

Management of Acute Myeloid Leukemia: A Review for General Practitioners in Oncology

Acute myeloid leukemia (AML) is a hematologic malignancy that most frequently develops in older adults. Overall, AML is associated with a high mortality although advancements in genetic risk stratification and new treatments are leading to improvements in outcomes for some subgroups. In this review, we discuss an individualized approach to intensive therapy with a focus on the role of recently approved novel therapies as well as the selection of post-remission therapies for patients in first remission. We discuss the management of patients with relapsed and refractory AML, including the role of targeted treatment and allogeneic stem cell transplant. Next, we review non-intensive treatment for older and unfit AML patients including the use of azacitidine and venetoclax. Finally, we discuss the integration of palliative care in the management of patients with AML.

Which FLT3 Inhibitor for Treatment of AML?

OPINION STATEMENT

Treatment options in acute myeloid leukemia (AML) have improved significantly over the last decade with better understanding of disease biology and availability of a multitude of targeted therapies. The use of FLT3 inhibitors (FLT3i) in FLT3-mutated (FLT3^mut) AML is one such development; however, the clinical decisions that govern their use and dictate the choice of the FLT3i are evolving. Midostaurin and gilteritinib are FDA-approved in specific situations; however, available data from clinical trials also shed light on the utility of sorafenib maintenance post-allogeneic stem cell transplantation (allo-SCT) and quizartinib as part of combination therapy in FLT3^mut AML. The knowledge of the patient's concurrent myeloid mutations, type of FLT3 mutation, prior FLT3i use, and eligibility for allo-SCT helps to refine the choice of FLT3i. Data from ongoing studies will further precisely define their use and help in making more informed choices. Despite improvements in FLT3i therapy, the definitive aim is to enable the eligible patient with FLT3^mut AML (esp. ITD) to proceed to allo-SCT with regimens containing FLT3i incorporated prior to SCT and as maintenance after SCT.