Review of New-Generation Tyrosine Kinase Inhibitors for Chronic Myeloid Leukemia

Structure and Dynamics of the ABL1 Tyrosine Kinase and Its Important Role in Chronic Myeloid Leukemia

Abelson (ABL1) tyrosine kinase is an essential component of non-receptor tyrosine kinases and is associated with numerous cellular processes, including differentiation and proliferation. The structural features of ABL1 include a distinct N-terminal cap region, a C-terminal tail, a bilobed kinase, SH2, and SH3 domains. These domains enable its engagement in several signaling cascades and dynamic control. The pathophysiology of chronic myeloid leukemia (CML) is mainly driven by the BCR-ABL1 oncoprotein, arising from dysregulation of ABL1 kinase, namely through its fusion to the breakpoint cluster region (BCR) gene. ABL1 is a crucial target in the treatment of CML as the BCR-ABL1 fusion causes uncontrolled cellular proliferation and resistance to apoptosis. Tyrosine kinase inhibitors (TKIs) targeting the ABL1 tyrosine kinase are playing a critical role in the treatment of CML through the inhibition of persistently activated signaling pathways mediated by the BCR-ABL1 fusion protein. The article examines the structural characteristics of ABL1, how they relate to CML, and the interactions between ABL1 and the current FDA-approved TKIs, emphasizing the kinase's critical function in carcinogenesis and its possible target status for tyrosine kinase inhibitors.

Validated HPLC-UV Method for the Quantification of a Novel BCr-Abl 1 Inhibitor, Vodobatinib, in Rat Plasma: Application to a Pharmacokinetic Study

Vodobatinib is a Bcr-Abl 1 inhibitor, currently entering into Phase 2 clinical trials as a potential drug to treat glioblastoma patients. In the present work, a validated high-performance liquid chromatography (HPLC) detection method for the quantification of vodobatinib in rat plasma was established. Sample preparation involved liquid-liquid extraction method. The chromatographic separation of vodobatinib and the IS was accomplished on an XBridge C18 column using 10 mM ammonium acetate and acetonitrile in gradient condition. The flow-rate and injection volume were 0.8 mL/min and 20 μL, respectively. The eluent was detected at 310 nm. Vodobatinib and the IS eluted at 7.5 and 5.9 min, respectively, with a total run time of 10 min. Validation tests were performed according to FDA requirements. The established method showed good linearity in the range of 50.5-6534 ng/mL. Interday and intraday coefficients of variations were < 5.11%. Stability studies, dilution integrity, and incurred sample reanalysis met the acceptance criteria. Subsequently, the validated HPLC method was used to study the disposition kinetics of vodobatinib in rats.

Synthetic Approaches to the New Drugs Approved During 2022

In 2022, 23 new small molecule chemical entities were approved as drugs by the United States FDA, European Union EMA, Japan PMDA, and China NMPA. This review describes the synthetic approach demonstrated on largest scale for each new drug based on patent or primary literature. The synthetic routes highlight practical methods to construct molecules, sometimes on the manufacturing scale, to access the new drugs. Ten additional drugs approved in 2021 and one approved in 2020 are included that were not covered in the previous year's review.

Genetic alterations in the BCR-ABL1 fusion gene related to imatinib resistance in chronic myeloid leukemia

Use of the potent tyrosine kinase inhibitor imatinib as the first-line treatment in chronic myeloid leukemia (CML) has decreased mortality from 20% to 2%. Approximately 30% of CML patients experience imatinib resistance, however, largely because of point mutations in the kinase domain of the BCR-ABL1 fusion gene. The aim of this study was to use next-generation sequencing (NGS) to identify mutations related to imatinib resistance. The study included 22 patients diagnosed with CML and experiencing no clinical response to imatinib. Total RNA was used for cDNA synthesis, with amplification of a fragment encompassing the BCR-ABL1 kinase domain using a nested-PCR approach. Sanger and NGS were applied to detect genetic alterations. HaplotypeCaller was used for variant calling, and STAR-Fusion software was applied for fusion breakpoint identification. After sequencing analysis, F311I, F317L, and E450K mutations were detected respectively in three different participants, and in another two patients, single nucleotide variants in BCR (rs9608100, rs140506, rs16802) and ABL1 (rs35011138) were detected. Eleven patients carried e14a2 transcripts, nine had e13a2 transcripts, and both transcripts were identified in one patient. One patient had co-expression of e14a2 and e14a8 transcripts. The results identify candidate single nucleotide variants and co-expressed BCR-ABL1 transcripts in cellular resistance to imatinib.

Determination of olverembatinib in human plasma and cerebrospinal fluid by an LC-MS/MS method: validation and clinical application

A sensitive and robust LC-MS/MS method has been developed and validated for olverembatinib quantification in human plasma and cerebrospinal fluid (CSF). The method involved liquid-liquid extraction with methyl tertiary butyl ether for plasma pretreatment and precipitation enrichment with methanol for CSF pretreatment. Separation was achieved on the C18 column with gradient elutions of 10 mM ammonium formate in water and methanol-acetonitrile (50:50,v/v). Analyte detection was conducted by electrospray ionization (ESI) in a positive ion mode using multiple reaction monitoring (MRM). The m/z transitions were 533.4→433.2 for olverembatinib and m/z 502.4→394.2 for the internal standard (IS, Imatinib-d8). Calibration curves ranged from 0.500 to 50.0 ng/mL for plasma and from 0.0100 to 1.00 ng/mL for CSF. The intra- and inter-day precision and accuracy were < 15% for both plasma and CSF with four different quality control concentrations. The relative matrix effect was < 10% in plasma and artificial CSF. This method was successfully utilized for the measurement of olverembatinib concentrations in plasma and CSF from chronic myeloid leukemia patients.

TSPAN32 suppresses chronic myeloid leukemia pathogenesis and progression by stabilizing PTEN

We report herein that TSPAN32 is a key node factor for Philadelphia (Ph+) leukemia pathogenesis. We found that TSPAN32 expression was repressed by BCR-ABL and ectopic TSPAN32 expression upon Imatinib treatment inhibited the proliferation of Ph+ cell lines. Tspan32 overexpression significantly prevented BCR-ABL induced leukemia progression in a murine model and impaired leukemia stem cell (LSC) proliferation. LSCs represent an obstacle for chronic myeloid leukemia (CML) elimination, which continually replenish leukemia cells and are associated with disease relapse. Therefore, the identification of essential targets that contribute to the survival and self-renewal of LSCs is important for novel curative CML. Mechanistically, TSPAN32 was shown to interact with PTEN, increased its protein level and caused a reduction in PI3K-AKT signaling activity. We also found that TSPAN32 was repressed by BCR-ABL via the suppression of an important transcription factor, TAL1. Ectopic expression of TAL1 significantly increased TSPAN32 mRNA and protein level, which indicated that BCR-ABL repressed TSPAN32 transcription by decreasing TAL1 expression. Overall, we identified a new signaling axis composed of "BCR-ABL-TAL1-TSPAN32-PTEN-PI3K-AKT". Our findings further complement the known mechanisms underlying the transformation potential of BCR-ABL in CML pathogenesis. This new signaling axis also provides a potential means to target PI3K-AKT for CML treatment.

JAK2 Alterations in Acute Lymphoblastic Leukemia: Molecular Insights for Superior Precision Medicine Strategies

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, arising from immature lymphocytes that show uncontrolled proliferation and arrested differentiation. Genomic alterations affecting Janus kinase 2 (JAK2) correlate with some of the poorest outcomes within the Philadelphia-like subtype of ALL. Given the success of kinase inhibitors in the treatment of chronic myeloid leukemia, the discovery of activating JAK2 point mutations and JAK2 fusion genes in ALL, was a breakthrough for potential targeted therapies. However, the molecular mechanisms by which these alterations activate JAK2 and promote downstream signaling is poorly understood. Furthermore, as clinical data regarding the limitations of approved JAK inhibitors in myeloproliferative disorders matures, there is a growing awareness of the need for alternative precision medicine approaches for specific JAK2 lesions. This review focuses on the molecular mechanisms behind ALL-associated JAK2 mutations and JAK2 fusion genes, known and potential causes of JAK-inhibitor resistance, and how JAK2 alterations could be targeted using alternative and novel rationally designed therapies to guide precision medicine approaches for these high-risk subtypes of ALL.

An evaluation of asciminib for patients with chronic myeloid leukemia previously treated with ≥2 Tyrosine Kinase Inhibitors

INTRODUCTION

: To date, five tyrosine kinase inhibitors (TKIs) are available for treating chronic myeloid leukemia (CML) patients in clinical practice. Despite this, a significant proportion of patients will ultimately develop failure to approved TKIs due to intolerance or resistance. Consequently, new treatment approaches are still required in this unmet clinical need. Asciminib, a first-in-class BCR::ABL1 inhibitor Specifically Targeting the ABL Myristoyl Pocket (STAMP), has the potential to overcome resistance/intolerance to prior TKI treatment.

AREAS COVERED

This review will cover the mechanism of action, pharmacokinetic profile and clinical data of asciminib based on available information from laboratory studies, clinical trials and real world evidence.

EXPERT OPINION

Recent approval of asciminib will require positioning of this drug in the treatment algorithm of CML patients failing initial TKI therapy. Available data support the lack of cross-intolerance of asciminib with other TKIs and its favorable cardiovascular toxicity profile. In addition, asciminib has demonstrated considerable efficacy in CML patients who have failed at least two TKIs, although preliminary data suggest that this efficacy may be lower in those previously exposed to ponatinib. The introduction of asciminib in clinical practice may represent an important step forward in the management of CML.

Recent advances of nanodrug delivery system in the treatment of hematologic malignancies

Although the survival rate of hematological malignancies (HM) has increased in recent years, the unnecessary adverse effect to the body is usually generated by the traditional chemotherapy for HM due to the lack of specificity to tumor tissue. Nanodrug delivery systems have exhibited unique advantages in targetability, stability and reducing toxicity, attracting wide concern, which is expected to be the prevalent alternative for the treatment of HM. In this review, we systemically introduced the current therapeutic strategies and the categories of HM. Subsequently, five key factors including circulation, targeting, penetration, internalization and release involving in tailoring nanoparticles were demonstrated, followed by the introduction of the development of nanodrug delivery-traditional synthetic nanomaterilas, biomimetic cell membrane coating nanomaterials, cell-based nanomaterials as well as immunotherapy combined with nanodrug. Afterwards, the recent advances of nanodrug delivery system for the treatment of HM were introduced. Moreover, the challenge and prospect of nanodrug delivery system in treating HM were discussed. The promising drug delivery system will provide new therapeutic avenues for the treatment of HM.

Olverembatinib: First Approval

Olverembatinib (HQP1351) is an oral, third-generation BCR-ABL1 tyrosine kinase inhibitor (TKI) developed by Ascentage Pharma for the treatment of chronic myeloid leukaemia (CML), acute myeloid leukaemia, acute lymphoblastic leukaemia (ALL) and solid tumours, including gastrointestinal stromal tumours (GIST). Olverembatinib is an ATP binding-site inhibitor of wild type BCR-ABL1 kinase and a broad spectrum of BCR-ABL1 mutants, including mutant T315I, which confers resistance against all first- and second-generation TKIs. In November 2021, olverembatinib received its first approval in China for the treatment of adult patients with TKI-resistant chronic-phase CML (CML-CP) or accelerated-phase CML (CML-AP) harbouring the T315I mutation, as confirmed by a validated diagnostic test. Clinical studies are underway in the US for CML and precursor cell ALL, and in China for solid tumours, including GIST. This article summarizes the milestones in the development of olverembatinib leading to this first approval for the treatment of CML-CP or CML-AP.

BCR-ABL1 Tyrosine Kinase Complex Signaling Transduction: Challenges to Overcome Resistance in Chronic Myeloid Leukemia

The constitutively active BCR-ABL1 tyrosine kinase, found in t(9;22)(q34;q11) chromosomal translocation-derived leukemia, initiates an extremely complex signaling transduction cascade that induces a strong state of resistance to chemotherapy. Targeted therapies based on tyrosine kinase inhibitors (TKIs), such as imatinib, dasatinib, nilotinib, bosutinib, and ponatinib, have revolutionized the treatment of BCR-ABL1-driven leukemia, particularly chronic myeloid leukemia (CML). However, TKIs do not cure CML patients, as some develop TKI resistance and the majority relapse upon withdrawal from treatment. Importantly, although BCR-ABL1 tyrosine kinase is necessary to initiate and establish the malignant phenotype of Ph-related leukemia, in the later advanced phase of the disease, BCR-ABL1-independent mechanisms are also in place. Here, we present an overview of the signaling pathways initiated by BCR-ABL1 and discuss the major challenges regarding immunologic/pharmacologic combined therapies.

The Use of Inhibitors of Tyrosine Kinase in Paediatric Haemato-Oncology-When and Why?

The fundamental pathophysiology of malignancies is dysregulation of the signalling pathways. Protein tyrosine kinases (PTKs) are among the enzymes which, if mutated, play a critical role in carcinogenesis. The best-studied rearrangement, which enhances PTK activity and causes atypical proliferation, is BCR-ABL1. Abnormal expression of PTKs has proven to play a significant role in the development of various malignancies, such as chronic myelogenous leukaemia, brain tumours, neuroblastoma, and gastrointestinal stromal tumours. The use of tyrosine kinase inhibitors (TKIs) is an outstanding example of successful target therapy. TKIs have been effectively applied in the adult oncology setting, but there is a need to establish TKIs’ importance in paediatric patients. Many years of research have allowed a significant improvement in the outcome of childhood cancers. However, there are still groups of patients who have a poor prognosis, where the intensification of chemotherapy could even cause death. TKIs are designed to target specific PTKs, which lead to the limitation of severe adverse effects and increase overall survival. These advances will hopefully allow new therapeutic approaches in paediatric haemato-oncology to emerge. In this review, we present an analysis of the current data on tyrosine kinase inhibitors in childhood cancers.