Stepwise activities of mSWI/SNF family chromatin remodeling complexes direct T cell activation and exhaustion.

Highly coordinated changes in gene expression underlie T cell activation and exhaustion. However, the mechanisms by which such programs are regulated and how these may be targeted for therapeutic benefit remain poorly understood. Here, we comprehensively profile the genomic occupancy of mSWI/SNF chromatin remodeling complexes throughout acute and chronic T cell stimulation, finding that stepwise changes in localization over transcription factor binding sites direct site-specific chromatin accessibility and gene activation leading to distinct phenotypes. Notably, perturbation of mSWI/SNF complexes using genetic and clinically relevant chemical strategies enhances the persistence of T cells with attenuated exhaustion hallmarks and increased memory features in vitro and in vivo. Finally, pharmacologic mSWI/SNF inhibition improves CAR-T expansion and results in improved anti-tumor control in vivo. These findings reveal the central role of mSWI/SNF complexes in the coordination of T cell activation and exhaustion and nominate small-molecule-based strategies for the improvement of current immunotherapy protocols.

Cellular pathways influenced by protein arginine methylation: Implications for cancer.

Arginine methylation is an influential post-translational modification occurring on histones, RNA binding proteins, and many other cellular proteins, affecting their function by altering their protein-protein and protein-nucleic acid interactions. Recently, a wealth of information has been gathered, implicating protein arginine methyltransferases (PRMTs), enzymes that deposit arginine methylation, in transcription, pre-mRNA splicing, DNA damage signaling, and immune signaling with major implications for cancer therapy, especially immunotherapy. This review summarizes this recent progress and the current state of PRMT inhibitors, some in clinical trials, as promising drug targets for cancer.

Mitogen-Activated Protein Kinase Phosphatases: No Longer Undruggable?

Phosphatases and kinases maintain an equilibrium of dephosphorylated and phosphorylated proteins, respectively, that are required for critical cellular functions. Imbalance in this equilibrium or irregularity in their function causes unfavorable cellular effects that have been implicated in the development of numerous diseases. Protein tyrosine phosphatases (PTPs) catalyze the dephosphorylation of protein substrates on tyrosine residues, and their involvement in cell signaling and diseases such as cancer and inflammatory and metabolic diseases has made them attractive therapeutic targets. However, PTPs have proved challenging in therapeutics development, garnering them the unfavorable reputation of being undruggable. Nonetheless, great strides have been made toward the inhibition of PTPs over the past decade. Here, we discuss the advancement in small-molecule inhibition for the PTP subfamily known as the mitogen-activated protein kinase (MAPK) phosphatases (MKPs). We review strategies and inhibitor discovery tools that have proven successful for small-molecule inhibition of the MKPs and discuss what the future of MKP inhibition potentially might yield.

A small-molecule inhibitor of TopBP1 exerts anti-MYC activity and synergy with PARP inhibitors.

We have previously identified TopBP1 (topoisomerase IIß-binding protein 1) as a promising target for cancer therapy, given its role in the convergence of Rb, PI(3)K/Akt, and p53 pathways. Based on this, we conducted a large-scale molecular docking screening to identify a small-molecule inhibitor that specifically targets the BRCT7/8 domains of TopBP1, which we have named 5D4. Our studies show that 5D4 inhibits TopBP1 interactions with E2F1, mutant p53, and Cancerous Inhibitor of Protein Phosphatase 2A. This leads to the activation of E2F1-mediated apoptosis and the inhibition of mutant p53 gain of function. In addition, 5D4 disrupts the interaction of TopBP1 with MIZ1, which in turn allows MIZ1 to bind to its target gene promoters and repress MYC activity. Moreover, 5D4 inhibits the association of the TopBP1-PLK1 complex and prevents the formation of Rad51 foci. When combined with inhibitors of PARP1/2 or PARP14, 5D4 synergizes to effectively block cancer cell proliferation. Our animal studies have demonstrated the antitumor activity of 5D4 in breast and ovarian cancer xenograft models. Moreover, the effectiveness of 5D4 is further enhanced when combined with a PARP1/2 inhibitor talazoparib. Taken together, our findings strongly support the potential use of TopBP1-BRCT7/8 inhibitors as a targeted cancer therapy.

MetaHMEI: meta-learning for prediction of few-shot histone modifying enzyme inhibitors.

MOTIVATION: Histones are the chief protein components of chromatin, and the chemical modifications on histones crucially influence the transcriptional state of related genes. Histone modifying enzyme (HME), responsible for adding or removing the chemical labels, has emerged as a very important class of drug target, with a few HME inhibitors launched as anti-cancerous drugs and tens of molecules under clinical trials. To accelerate the drug discovery process of HME inhibitors, machine learning-based predictive models have been developed to enrich the active molecules from vast chemical space. However, the number of compounds with known activity distributed largely unbalanced among different HMEs, particularly with many targets of less than a hundred active samples. In this case, it is difficult to build effective virtual screening models directly based on machine learning. RESULTS: To this end, we propose a new Meta-learning-based Histone Modifying Enzymes Inhibitor prediction method (MetaHMEI). Our proposed MetaHMEI first uses a self-supervised pre-training approach to obtain high-quality molecular substructure embeddings from a large unlabeled chemical dataset. Then, MetaHMEI exploits a Transformer-based encoder and meta-learning framework to build a prediction model. MetaHMEI allows the effective transfer of the prior knowledge learned from HMEs with sufficient samples to HMEs with a small number of samples, so the proposed model can produce accurate predictions for HMEs with limited data. Extensive experimental results on our collected and curated HMEs datasets show that MetaHMEI is better than other methods in the case of few-shot learning. Furthermore, we applied MetaHMEI in the virtual screening process of histone JMJD3 inhibitors and successfully obtained three small molecule inhibitors, further supporting the validity of our model.

Discovery of potent BET bromodomain 1 stereoselective inhibitors using DNA-encoded chemical library selections.

BRDT, BRD2, BRD3, and BRD4 comprise the bromodomain and extraterminal (BET) subfamily which contain two similar tandem bromodomains (BD1 and BD2). Selective BD1 inhibition phenocopies effects of tandem BET BD inhibition both in cancer models and, as we and others have reported of BRDT, in the testes. To find novel BET BD1 binders, we screened >4.5 billion molecules from our DNA-encoded chemical libraries with BRDT-BD1 or BRDT-BD2 proteins in parallel. A compound series enriched only by BRDT-BD1 was resynthesized off-DNA, uncovering a potent chiral compound, CDD-724, with >2,000-fold selectivity for inhibiting BRDT-BD1 over BRDT-BD2. CDD-724 stereoisomers exhibited remarkable differences in inhibiting BRDT-BD1, with the R-enantiomer (CDD-787) being 50-fold more potent than the S-enantiomer (CDD-786). From structure­activity relationship studies, we produced CDD-956, which maintained picomolar BET BD1 binding potency and high selectivity over BET BD2 proteins and had improved stability in human liver microsomes over CDD-787. BROMOscan profiling confirmed the excellent pan-BET BD1 affinity and selectivity of CDD-787 and CDD-956 on BD1 versus BD2 and all other BD-containing proteins. A cocrystal structure of BRDT-BD1 bound with CDD-956 was determined at 1.82 Å and revealed BRDT-BD1­specific contacts with the αZ and αC helices that explain the high affinity and selectivity for BET BD1 versus BD2. CDD-787 and CDD-956 maintain cellular BD1-selectivity in NanoBRET assays and show potent antileukemic activity in acute myeloid leukemia cell lines. These BET BD1-specific and highly potent compounds are structurally unique and provide insight into the importance of chirality to achieve BET specificity.

CARM1 arginine methyltransferase as a therapeutic target for cancer.

Coactivator-associated arginine methyltransferase 1 (CARM1) is an arginine methyltransferase that posttranslationally modifies proteins that regulate multiple levels of RNA production and processing. Its substrates include histones, transcription factors, coregulators of transcription, and splicing factors. CARM1 is overexpressed in many different cancer types, and often promotes transcription factor programs that are co-opted as drivers of the transformed cell state, a process known as transcription factor addiction. Targeting these oncogenic transcription factor pathways is difficult but could be addressed by removing the activity of the key coactivators on which they rely. CARM1 is ubiquitously expressed, and its KO is less detrimental in embryonic development than deletion of the arginine methyltransferases protein arginine methyltransferase 1 and protein arginine methyltransferase 5, suggesting that therapeutic targeting of CARM1 may be well tolerated. Here, we will summarize the normal in vivo functions of CARM1 that have been gleaned from mouse studies, expand on the transcriptional pathways that are regulated by CARM1, and finally highlight recent studies that have identified oncogenic properties of CARM1 in different biological settings. This review is meant to kindle an interest in the development of human drug therapies targeting CARM1, as there are currently no CARM1 inhibitors available for use in clinical trials.

Reversible and irreversible inhibitors of coronavirus Nsp15 endoribonuclease.

The emergence of severe acute respiratory syndrome coronavirus 2, the causative agent of coronavirus disease 2019, has resulted in the largest pandemic in recent history. Current therapeutic strategies to mitigate this disease have focused on the development of vaccines and on drugs that inhibit the viral 3CL protease or RNA-dependent RNA polymerase enzymes. A less-explored and potentially complementary drug target is Nsp15, a uracil-specific RNA endonuclease that shields coronaviruses and other nidoviruses from mammalian innate immune defenses. Here, we perform a high-throughput screen of over 100,000 small molecules to identify Nsp15 inhibitors. We characterize the potency, mechanism, selectivity, and predicted binding mode of five lead compounds. We show that one of these, IPA-3, is an irreversible inhibitor that might act via covalent modification of Cys residues within Nsp15. Moreover, we demonstrate that three of these inhibitors (hexachlorophene, IPA-3, and CID5675221) block severe acute respiratory syndrome coronavirus 2 replication in cells at subtoxic doses. This study provides a pipeline for the identification of Nsp15 inhibitors and pinpoints lead compounds for further development against coronavirus disease 2019 and related coronavirus infections.

Drugs That Regulate Local Cell Signaling: AKAP Targeting as a Therapeutic Option.

Cells respond to environmental cues by mobilizing signal transduction cascades that engage protein kinases and phosphoprotein phosphatases. Correct organization of these enzymes in space and time enables the efficient and precise transmission of chemical signals. The cyclic AMP-dependent protein kinase A is compartmentalized through its association with A-kinase anchoring proteins (AKAPs). AKAPs are a family of multivalent scaffolds that constrain signaling enzymes and effectors at subcellular locations to drive essential physiological events. More recently, it has been recognized that defective signaling in certain endocrine disorders and cancers proceeds through pathological AKAP complexes. Consequently, pharmacologically targeting these macromolecular complexes unlocks new therapeutic opportunities for a growing number of clinical indications. This review highlights recent findings on AKAP signaling in disease, particularly in certain cancers, and offers an overview of peptides and small molecules that locally regulate AKAP-binding partners.

Managing infectious challenges in the age of molecular-targeted therapies for adult hematological malignancies.

Over the last decade, the therapeutic landscape for hematological malignancies (HMs) has witnessed a remarkable surge in the development of novel biological and small-molecule-targeted immunomodulatory agents. These therapies have drastically improved survival, but some come at the cost of increased risk of bacterial, viral, and/or fungal infections and on-target off-tumor immunological side effects. To mitigate such risks, physicians must be well informed about infectious complications and necessary preventive measures, such as screening, vaccinations, and antimicrobial prophylaxis. Furthermore, physicians should be vigilant about the noninfectious side effects of these agents that can mimic infections and understand their potential drug-drug interactions with antimicrobials. Strengthening and harmonizing the current surveillance and reporting system for drug-associated infections in real-world settings is essential to better ascertain the potential infections associated with these agents. In this review, we aimed to summarize the infection risks associated with novel agents used for specific HMs and outline recommended strategies for monitoring and prophylaxis.

Development and therapeutic potential of DNA-dependent protein kinase inhibitors.

The deployment of DNA damage response (DDR) combats various forms of DNA damage, ensuring genomic stability. Cancer cells' propensity for genomic instability offers therapeutic opportunities to selectively kill cancer cells by suppressing the DDR pathway. DNA-dependent protein kinase (DNA-PK), a nuclear serine/threonine kinase, is crucial for the non-homologous end joining (NHEJ) pathway in the repair of DNA double-strand breaks (DSBs). Therefore, targeting DNA-PK is a promising cancer treatment strategy. This review elaborates on the structures of DNA-PK and its related large protein, as well as the development process of DNA-PK inhibitors, and recent advancements in their clinical application. We emphasize our analysis of the development process and structure-activity relationships (SARs) of DNA-PK inhibitors based on different scaffolds. We hope this review will provide practical information for researchers seeking to develop novel DNA-PK inhibitors in the future.

The foundation for investigating factor XI as a target for inhibition in human cardiovascular disease.

Anticoagulant therapy is a mainstay in the management of patients with cardiovascular disease and related conditions characterized by a heightened risk for thrombosis. Acute coronary syndrome, chronic coronary syndrome, ischemic stroke, and atrial fibrillation are the most common. In addition to their proclivity for thrombosis, each of these four conditions is also characterized by local and systemic inflammation, endothelial/endocardial injury and dysfunction, oxidative stress, impaired tissue-level reparative capabilities, and immune dysregulation that plays a critical role in linking molecular events, environmental triggers, and phenotypic expressions. Knowing that cardiovascular disease and thrombosis are complex and dynamic, can the scientific community identify a common pathway or specific point of interface susceptible to pharmacological inhibition or alteration that is likely to be safe and effective? The contact factors of coagulation may represent the proverbial "sweet spot" and are worthy of investigation. The following review provides a summary of the fundamental biochemistry of factor XI, its biological activity in thrombosis, inflammation, and angiogenesis, new targeting drugs, and a pragmatic approach to managing hemostatic requirements in clinical trials and possibly day-to-day patient care in the future.

Emerging role of glutathione peroxidase 4 in myeloid cell lineage development and acute myeloid leukemia.

Phospholipid Hydroperoxide Gluthatione Peroxidase also called Glutathione Peroxidase 4 is one of the 25 described human selenoproteins. It plays an essential role in eliminating toxic lipid hydroxy peroxides, thus inhibiting ferroptosis and favoring cell survival. GPX4 is differentially expressed according to myeloid differentiation stage, exhibiting lower expression in hematopoietic stem cells and polymorphonuclear leucocytes, while harboring higher level of expression in common myeloid progenitors and monocytes. In addition, GPX4 is highly expressed in most of acute myeloid leukemia (AML) subtypes compared to normal hematopoietic stem cells. High GPX4 expression is consistently correlated to poor prognosis in patients suffering AML. However, the role of GPX4 in the development of the myeloid lineage and in the initiation and progression of myeloid leukemia remains poorly explored. Given its essential role in the detoxification of lipid hydroperoxides, and its overexpression in most of myeloid malignancies, GPX4 inhibition has emerged as a promising therapeutic strategy to specifically trigger ferroptosis and eradicate myeloid leukemia cells. In this review, we describe the most recent advances concerning the role of GPX4 and, more generally ferroptosis in the myeloid lineage and in the emergence of AML. We also discuss the therapeutic interest and limitations of GPX4 inhibition alone or in combination with other drugs as innovative therapies to treat AML patients.

MYB as a Critical Transcription Factor and Potential Therapeutic Target in AML.

Myb was identified over four decades ago as the transforming component of acute leukemia viruses in chickens. Since then it has become increasingly apparent that dysregulated MYB activity characterizes many blood cancers, including acute myeloid leukemia, and that it represents the most "addictive" oncoprotein in many, if not all, such diseases. As a consequence of this tumor-specific dependency for MYB, it has become a major focus of efforts to develop specific antileukemia drugs. Much attention is being given to ways to interrupt the interaction between MYB and cooperating factors, in particular EP300/KAT3B and CBP/KAT3A. Aside from candidates identified through screening of small molecules, the most exciting prospect for novel drugs seems to be the design of peptide mimetics that interfere directly at the interface between MYB and its cofactors. Such peptides combine a high degree of target specificity with good efficacy including minimal effects on normal hematopoietic cells.

Discovery and characterization of bromodomain 2-specific inhibitors of BRDT.

Bromodomain testis (BRDT), a member of the bromodomain and extraterminal (BET) subfamily that includes the cancer targets BRD2, BRD3, and BRD4, is a validated contraceptive target. All BET subfamily members have two tandem bromodomains (BD1 and BD2). Knockout mice lacking BRDT-BD1 or both bromodomains are infertile. Treatment of mice with JQ1, a BET BD1/BD2 nonselective inhibitor with the highest affinity for BRD4, disrupts spermatogenesis and reduces sperm number and motility. To assess the contribution of each BRDT bromodomain, we screened our collection of DNA-encoded chemical libraries for BRDT-BD1 and BRDT-BD2 binders. High-enrichment hits were identified and resynthesized off-DNA and examined for their ability to compete with JQ1 in BRDT and BRD4 bromodomain AlphaScreen assays. These studies identified CDD-1102 as a selective BRDT-BD2 inhibitor with low nanomolar potency and >1,000-fold selectivity over BRDT-BD1. Structure-activity relationship studies of CDD-1102 produced a series of additional BRDT-BD2/BRD4-BD2 selective inhibitors, including CDD-1302, a truncated analog of CDD-1102 with similar activity, and CDD-1349, an analog with sixfold selectivity for BRDT-BD2 versus BRD4-BD2. BROMOscan bromodomain profiling confirmed the great affinity and selectivity of CDD-1102 and CDD-1302 on all BET BD2 versus BD1 with the highest affinity for BRDT-BD2. Cocrystals of BRDT-BD2 with CDD-1102 and CDD-1302 were determined at 2.27 and 1.90 Å resolution, respectively, and revealed BRDT-BD2 specific contacts that explain the high affinity and selectivity of these compounds. These BD2-specific compounds and their binding to BRDT-BD2 are unique compared with recent reports and enable further evaluation of their nonhormonal contraceptive potential in vitro and in vivo.

Inhibitors of cullin-RING E3 ubiquitin ligase 4 with antitumor potential.

Cullin-RING (really intersting new gene) E3 ubiquitin ligases (CRLs) are the largest E3 family and direct numerous protein substrates for proteasomal degradation, thereby impacting a myriad of physiological and pathological processes including cancer. To date, there are no reported small-molecule inhibitors of the catalytic activity of CRLs. Here, we describe high-throughput screening and medicinal chemistry optimization efforts that led to the identification of two compounds, 33-11 and KH-4-43, which inhibit E3 CRL4 and exhibit antitumor potential. These compounds bind to CRL4's core catalytic complex, inhibit CRL4-mediated ubiquitination, and cause stabilization of CRL4's substrate CDT1 in cells. Treatment with 33-11 or KH-4-43 in a panel of 36 tumor cell lines revealed cytotoxicity. The antitumor activity was validated by the ability of the compounds to suppress the growth of human tumor xenografts in mice. Mechanistically, the compounds' cytotoxicity was linked to aberrant accumulation of CDT1 that is known to trigger apoptosis. Moreover, a subset of tumor cells was found to express cullin4 proteins at levels as much as 70-fold lower than those in other tumor lines. The low-cullin4-expressing tumor cells appeared to exhibit increased sensitivity to 33-11/KH-4-43, raising a provocative hypothesis for the role of low E3 abundance as a cancer vulnerability.

Estrogen-related receptor, a molecular target against lepidoptera pests.

Until recently, chemical pesticides were one of the most effective means of controlling agricultural pests; therefore, the search for insecticide targets for agricultural pests has been an ongoing problem. Estrogen-related receptors (ERRs) are transcription factors that regulate cellular metabolism and energy homeostasis in animals. Silkworms are highly sensitive to chemical pesticides, making them ideal models for pesticide screening and evaluation. In this study, we detected ERR expression in key organs involved in pesticide metabolism in silkworms (Bombyx mori), including the fat body and midgut. Using ChIP-seq technology, many estrogen- related response elements were identified in the 2000-bp promoter region upstream of metabolism-related genes, almost all of which were potential ERR target genes. The ERR inhibitor, XCT-790, and the endocrine disruptor, bisphenol A, significantly inhibited expression of the ERR target genes, BmTreh-1, BmTret-1, BmPK, BmPFK, and BmHK, in the fat bodies of silkworms, resulting in pupation difficulties in silkworm larvae that ultimately lead to death. In addition, based on the clarification that the ERR can bind to XCT-790, as observed through biofilm interferometry, its three-dimensional spatial structure was predicted, and using molecular docking techniques, small-molecule compounds with a stronger affinity for the ERR were identified. In summary, utilizing the powerful metabolic regulatory function of ERR in Lepidoptera pests, the developed small molecule inhibitors of ERR can be used for future control of Lepidoptera pests.

mCRP-Induced Focal Adhesion Kinase-Dependent Monocyte Aggregation and M1 Polarization, Which Was Partially Blocked by the C10M Inhibitor.

Monomeric C-reactive protein (mCRP) has recently been implicated in the abnormal vascular activation associated with development of atherosclerosis, but it may act more specifically through mechanisms perpetuating damaged vessel inflammation and subsequent aggregation and internalization of resident macrophages. Whilst the direct effects of mCRP on endothelial cells have been characterized, the interaction with blood monocytes has, to our knowledge, not been fully defined. Here we showed that mCRP caused a strong aggregation of both U937 cell line and primary peripheral blood monocytes (PBMs) obtained from healthy donors. Moreover, this increase in clustering was dependent on focal adhesion kinase (FAK) activation (blocked by a specific inhibitor), as was the concomitant adhesive attachment to the plate, which was suggestive of macrophage differentiation. Confocal microscopy confirmed the increased expression and nuclear localization of p-FAK, and cell surface marker expression associated with M1 macrophage polarization (CD11b, CD14, and CD80, as well as iNOS) in the presence of mCRP. Inclusion of a specific CRP dissociation/mCRP inhibitor (C10M) effectively inhibited PBMs clustering, as well as abrogating p-FAK expression, and partially reduced the expression of markers associated with M1 macrophage differentiation. mCRP also increased the secretion of pro-inflammatory cytokines Interleukin-8 (IL-8) and Interleukin-1ß (IL-1ß), without notably affecting MAP kinase signaling pathways; inclusion of C10M did not perturb or modify these effects. In conclusion, mCRP modulates PBMs through a mechanism that involves FAK and results in cell clustering and adhesion concomitant with changes consistent with M1 phenotypical polarization. C10M has potential therapeutic utility in blocking the primary interaction of mCRP with the cells-for example, by protecting against monocyte accumulation and residence at damaged vessels that may be predisposed to plaque development and atherosclerosis.

Inhibition of the RAF/MEK/ERK Signaling Cascade in Pancreatic Cancer: Recent Advances and Future Perspectives.

Pancreatic cancer represents a formidable challenge in oncology, primarily due to its aggressive nature and limited therapeutic options. The prognosis of patients with pancreatic ductal adenocarcinoma (PDAC), the main form of pancreatic cancer, remains disappointingly poor with a 5-year overall survival of only 5%. Almost 95% of PDAC patients harbor Kirsten rat sarcoma virus (KRAS) oncogenic mutations. KRAS activates downstream intracellular pathways, most notably the rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling axis. Dysregulation of the RAF/MEK/ERK pathway is a crucial feature of pancreatic cancer and therefore its main components, RAF, MEK and ERK kinases, have been targeted pharmacologically, largely by small-molecule inhibitors. The recent advances in the development of inhibitors not only directly targeting the RAF/MEK/ERK pathway but also indirectly through inhibition of its regulators, such as Src homology-containing protein tyrosine phosphatase 2 (SHP2) and Son of sevenless homolog 1 (SOS1), provide new therapeutic opportunities. Moreover, the discovery of allele-specific small-molecule inhibitors against mutant KRAS variants has brought excitement for successful innovations in the battle against pancreatic cancer. Herein, we review the recent advances in targeted therapy and combinatorial strategies with focus on the current preclinical and clinical approaches, providing critical insight, underscoring the potential of these efforts and supporting their promise to improve the lives of patients with PDAC.

Clinical Insights into Structure, Regulation, and Targeting of ABL Kinases in Human Leukemia.

Chronic myeloid leukemia is a multistep, multi-lineage myeloproliferative disease that originates from a translocation event between chromosome 9 and chromosome 22 within the hematopoietic stem cell compartment. The resultant fusion protein BCR::ABL1 is a constitutively active tyrosine kinase that can phosphorylate multiple downstream signaling molecules to promote cellular survival and inhibit apoptosis. Currently, tyrosine kinase inhibitors (TKIs), which impair ABL1 kinase activity by preventing ATP entry, are widely used as a successful therapeutic in CML treatment. However, disease relapses and the emergence of resistant clones have become a critical issue for CML therapeutics. Two main reasons behind the persisting obstacles to treatment are the acquired mutations in the ABL1 kinase domain and the presence of quiescent CML leukemia stem cells (LSCs) in the bone marrow, both of which can confer resistance to TKI therapy. In this article, we systemically review the structural and molecular properties of the critical domains of BCR::ABL1 and how understanding the essential role of BCR::ABL1 kinase activity has provided a solid foundation for the successful development of molecularly targeted therapy in CML. Comparison of responses and resistance to multiple BCR::ABL1 TKIs in clinical studies and current combination treatment strategies are also extensively discussed in this article.