The TKI Era in Chronic Leukemias

Inhibition of Tumoral VISTA to Overcome TKI Resistance via Downregulation of the AKT/mTOR and JAK2/STAT5 Pathways in Chronic Myeloid Leukemia

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment landscape for chronic myeloid leukemia (CML). However, TKI resistance poses a significant challenge, leading to treatment failure and disease progression. Resistance mechanisms include both BCR::ABL1-dependent and BCR::ABL1-independent pathways. The mechanisms underlying BCR::ABL1 independence remain incompletely understood, with CML cells potentially activating alternative signaling pathways, including the AKT/mTOR and JAK2/STAT5 pathways, to compensate for the loss of BCR::ABL1 kinase activity. This study explored tumoral VISTA (encoded by VSIR) as a contributing factor to TKI resistance in CML patients and identified elevated tumoral VISTA levels as a marker of resistance and poor survival. Through in vitro and in vivo analyses, we demonstrated that VSIR knockdown and the application of NSC-622608, a novel VISTA inhibitor, significantly impeded CML cell proliferation and induced apoptosis by attenuating the AKT/ mTOR and JAK2/STAT5 pathways, which are crucial for CML cell survival independent of BCR::ABL1 kinase activity. Moreover, VSIR overexpression promoted TKI resistance in CML cells. Importantly, the synergistic effect of NSC-622608 with TKIs offers a potent therapeutic avenue against both imatinib-sensitive and imatinib-resistant CML cells, including those harboring the challenging T315I mutation. Our findings highlight the role of tumoral VISTA in mediating TKI resistance in CML, suggesting that inhibition of VISTA, particularly in combination with TKIs, is an innovative approach to enhancing treatment outcomes in CML patients, irrespective of BCR::ABL1 mutation status. This study not only identified a new pathway contributing to TKI resistance but also revealed the possibility of targeting tumoral VISTA as a means of overcoming this significant clinical challenge.

ACOX1-mediated peroxisomal fatty acid oxidation contributes to metabolic reprogramming and survival in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is still an incurable disease, with many patients developing resistance to conventional and targeted therapies. To better understand the physiology of CLL and facilitate the development of innovative treatment options, we examined specific metabolic features in the tumor CLL B-lymphocytes. We observed metabolic reprogramming, characterized by a high level of mitochondrial oxidative phosphorylation activity, a low glycolytic rate, and the presence of C2- to C6-carnitine end-products revealing an unexpected, essential role for peroxisomal fatty acid beta-oxidation (pFAO). Accordingly, downmodulation of ACOX1 (a rate-limiting pFAO enzyme overexpressed in CLL cells) was enough to shift the CLL cells' metabolism from lipids to a carbon- and amino-acid-based phenotype. Complete blockade of ACOX1 resulted in lipid droplet accumulation and caspase-dependent death in CLL cells, including those from individuals with poor cytogenetic and clinical prognostic factors. In a therapeutic translational approach, ACOX1 inhibition spared non-tumor blood cells from CLL patients but led to the death of circulating, BCR-stimulated CLL B-lymphocytes and CLL B-cells receiving pro-survival stromal signals. Furthermore, a combination of ACOX1 and BTK inhibitors had a synergistic killing effect. Overall, our results highlight a less-studied but essential metabolic pathway in CLL and pave the way towards the development of new, metabolism-based treatment options.

Severe Hyperglycemia Due to Protein Kinase Inhibitor Therapy in a Patient With Poorly Controlled Diabetes Mellitus

The efficacy and safety of zanubrutinib, a highly selective next-generation Bruton's tyrosine kinase (BTK) inhibitor, in chronic lymphocytic leukemia and lymphoplasmocytoides immunocytoma seems favorable. Adverse events comprise neutropenia, thrombocytopenia, infection, anemia, and atrial fibrillation. This report describes a 75-year-old man suffering from polydipsia, polyuria, and blurred vision for 10 days. He was diagnosed with lymphoplasmocytoides immunocytoma in 2003. After various therapies, he was started on zanubrutinib in October 2022. A diagnosis of diabetes mellitus had never been established before. On arrival in the emergency department, his plasma glucose was 37.2 mmol/L (671 mg/dL) and glycated hemoglobin (HbA1c) was 14.2%. Circulating antibodies showed positivity for glutamic acid decarboxylase (GAD-65), and his C-peptide level was 1.3 nmol/L (normal range, 0.37-1.47 nmol/L), equivalent to 3.9 ng/mL (normal range 1.1-5.0 ng/mL). From the patient's medical history, it became obvious that the metabolic situation had been problematic for many years, and that diabetes could have been taken into account at least in the summer of 2020 when HbA1c was 6.7%. In patients on tyrosine kinase inhibitors, careful assessment of glycemic control (monitoring HbA1c and blood glucose levels periodically even for nondiabetic patients) is recommended to prevent a major diabetic emergency.

GNF-7, a novel FLT3 inhibitor, overcomes drug resistance for the treatment of FLT3‑ITD acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) with FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation accounts for a large proportion of AML patients and diagnosed with poor prognosis. Although the prognosis of FLT3-ITD AML has been greatly improved, the drug resistance frequently occurred in the treatment of FLT3 targeting drugs. GNF-7, a multitargeted kinase inhibitor, which provided a novel therapeutic strategy for overriding leukemia. In this study, we explored the antitumor activity of GNF-7 against FLT3-ITD and clinically-relevant drug resistance in FLT3 mutant AML.

METHODS

Growth inhibitory assays were performed in AML cell lines and Ba/F3 cells expressing various FLT3 mutants to evaluate the antitumor activity of GNF-7 in vitro. Western blotting was used to examine the inhibitory  effect of GNF-7 on FLT3 and its downstream pathways. Molecular docking and cellular thermal shift assay (CETSA) were performed to demonstrate the binding of FLT3 to GNF-7. The survival benefit of GNF-7 in vivo was assessed in mouse models of transformed Ba/F3 cells harboring FLT3-ITD and FLT3-ITD/F691L mutation. Primary patient samples and a patient-derived xenograft (PDX) model were also used to determine the efficacy of GNF-7.

RESULTS

GNF-7 inhibited the cell proliferation of Ba/F3 cells expressing FLT3-ITD and exhibited potently anti-leukemia activity on primary FLT3-ITD AML samples. Moreover, GNF-7 could bind to FLT3 protein and inhibit the downstream signaling pathway activated by FLT3 including STAT5, PI3K/AKT and MAPK/ERK. In vitro and in vivo studies showed that GNF-7 exhibited potent inhibitory activity against FLT3-ITD/F691L that confers resistant to quizartinib (AC220) or gilteritinib. Importantly, GNF-7 showed potent cytotoxic effect on leukemic stem cells, significantly extend the survival of PDX model and exhibited similar therapy effect compared with gilteritinib.

CONCLUSIONS

Our results show that GNF-7 is a potent FLT3-ITD inhibitor and may become a promising lead compound applied for treating some of the clinically drug resistant patients.

Modern treatment strategies in pediatric oncology and hematology

Every year, approximately 400 00 children worldwide are diagnosed with cancer. Although treatment results in most types of childhood neoplasms are excellent with survival more than 80%, there are some with poor prognosis. Also recurrent and resistant to treatment childhood cancer remain a therapeutic challenge. Besides chemotherapy, which has been the basis of cancer therapy for years, molecular methods and precisely targeted therapies have recently found their usage. As a result of that, survival has improved and has positively impacted the rate of toxicities associated with chemotherapy (Butler et al. in CA Cancer J Clin 71:315-332, 2021). These achievements have contributed to better quality of patients' lives. Current methods of treatment and ongoing trials give hope for patients with relapses and resistance to conventional chemotherapy. This review focuses on the most recent progress in pediatric oncology treatments and discusses specific therapy methods for particular cancers types of cancer. Targeted therapies and molecular approaches have become more beneficial but research need to be continued in this field. Despite significant breakthroughs in pediatric oncology in the last few years, there is still a need to find new and more specific methods of treatment to increase the survival of children with cancer.

A Real-World Evidence-Based Study of Long-Term Tyrosine Kinase Inhibitors Dose Reduction or Discontinuation in Patients with Chronic Myeloid Leukaemia

The therapeutic approach to chronic myeloid leukaemia (CML) has changed in recent years. As a result, a high percentage of current patients in the chronic phase of the disease almost have an average life expectancy. Treatment also aims to achieve a stable deep molecular response (DMR) that might allow dose reduction or even treatment discontinuation. These strategies are often used in authentic practices to reduce adverse events, yet their impact on treatment-free remission (TFR) is a controversial debate. In some studies, it has been observed that as many as half of patients can achieve TFR after the discontinuation of TKI treatment. If TFR was more widespread and globally achievable, the perspective on toxicity could be changed. We retrospectively analysed 80 CML patients treated with tyrosine kinase inhibitor (TKI) at a tertiary hospital between 2002 and 2022. From them, 71 patients were treated with low doses of TKI, and 25 were eventually discontinued, 9 of them being discontinued without a previous dose reduction. Regarding patients treated with low doses, only 11 of them had molecular recurrence (15.4%), and the average molecular recurrence free survival (MRFS) was 24.6 months. The MRFS outcome was not affected by any of the variables examined, including gender, Sokal risk scores, prior treatment with interferon or hydroxycarbamide, age at the time of CML diagnosis, the initiation of low-dose therapy and the mean duration of TKI therapy. After TKI discontinuation, all but four patients maintained MMR, with a median follow-up of 29.2 months. In our study, TFR was estimated at 38.9 months (95% CI 4.1-73.9). This study indicates that low-dose treatment and/or TKI discontinuation is a salient, safe alternative to be considered for patients who may suffer adverse events (AEs), which hinder the adherence of TKI and/or deteriorate their life quality. Together with the published literature, it shows that it appears safe to administer reduced doses to patients with CML in the chronic phase. The discontinuation of TKI therapy once a DMR has been reached is one of the goals for these patients. The patient should be assessed globally, and the most appropriate strategy for management should be considered. Future studies are needed to ensure that this approach is included in clinical practice because of the benefits for certain patients and the increased efficiency for the healthcare system.

Targeted-Lymphoma Drug Delivery System Based on the Sgc8-c Aptamer

Aptamers are emerging as a promising new class of functional nucleic acids because they can specifically bind to any target with high affinity and be easily modified chemically with different pharmacophoric subunits for therapy. The truncated aptamer, Sgc8-c, binds to tyrosine-protein kinase-like 7 receptor, a promising cancer therapeutic target, allowing the recognition of haemato-oncological malignancies, among others. We have previously developed aptamer-drug conjugates by chemical synthesis, hybridizing Sgc8-c and dasatinib, a drug proposed for lymphoma chemotherapy. One of the best-characterised Sgc8-c-dasatinib hybrids, namely Sgc8-c-carb-da, was capable of releasing dasatinib at an endosomal-pH. Herein, we probed the therapeutic potential of this aptamer-drug conjugate. Sgc8-c-carb-da specifically inhibited murine A20 B lymphocyte growth and produced cell death, mainly by late apoptosis and necrosis. In addition, Sgc8-c-carb-da generated an arrest in cell proliferation, with a cell cycle arrest in the Sub-G1-peak. The mitochondrial potential was altered accordingly to these pathways. Moreover, using an in vitro cell-targeting assay that mimics in vivo conditions, we showed that Sgc8-c-carb-da displayed higher (2.5-fold) cytotoxic effects than dasatinib. These findings provide proof-of-concept of the therapeutic value of Sgc8-c-carb-da for lymphoma, creating new opportunities for the chemical synthesis of targeted biotherapeutics.

Proteolysis Targeting Chimeric Molecules: Tuning Molecular Strategies for a Clinically Sound Listening

From seminal evidence in the early 2000s, the opportunity to drive the specific knockdown of a protein of interest (POI) through pharmacological entities called Proteolysis Targeting Chimeric molecules, or PROTACs, has become a possible therapeutic option with the involvement of these compounds in clinical trials for cancers and autoimmune diseases. The fulcrum of PROTACs pharmacodynamics is to favor the juxtaposition between an E3 ligase activity and the POI, followed by the ubiquitination of the latter and its degradation by the proteasome system. In the face of an apparently modular design of these drugs, being constituted by an E3 ligase binding moiety and a POI-binding moiety connected by a linker, the final structure of an efficient PROTAC degradation enhancer often goes beyond the molecular descriptors known to influence the biological activity, specificity, and pharmacokinetics, requiring a rational improvement through appropriate molecular strategies. Starting from the description of the basic principles underlying the activity of the PROTACs to the evaluation of the strategies for the improvement of pharmacodynamics and pharmacokinetics and rational design, this review examines the molecular elements that have been shown to be effective in allowing the evolution of these compounds from interesting proof of concepts to potential aids of clinical interest.