Phase 1 dose-finding study of rebastinib (DCC-2036) in patients with relapsed chronic myeloid leukemia and acute myeloid leukemia

PayloadGenX, a multi-stage hybrid virtual screening approach for payload design: A microtubule inhibitor case study

Due to the rapid emergence of treatment-resistant cancers, there is a growing need to discover new anticancer therapies. Antibody-drug conjugates (ADCs) are aimed at solving this problem by specifically targeting and delivering cytotoxic payloads directly to cancer cells, thereby minimizing damage to healthy cells and enhancing treatment efficacy. Therefore, it is highly important to find an effective cytotoxic payload to ensure maximum therapeutic benefit and overcome cancer resistance. To address this challenge, we have developed a multi-stage hybrid virtual screening (VS) approach for payload design. We collected approximately 900 million molecules from databases such as ZINC12, ChEMBL, PubChem, and QM9. Additionally, 220 approved small molecule anticancer drugs were collected. Initially, these molecules were screened based on the Lipinski Rule of Five (RO5) criteria, resulting in 20 million molecules that met the drug-like properties criteria. Subsequently, fragments being key factor in this approach were generated from approved small molecule cancer drugs. This fragment-based screening approach resulted in identifying 6500, 36770, and 150,000 anticancer-like drugs with a similarity threshold greater than 0.6, 0.5, and 0.4. Similarity threshold when increased near to 1 bears better chance of discovering cancer like drugs. Further molecular docking of these anticancer-like drugs with β-tubulin resulted in identifying the top 1000 ranked drugs as microtubule inhibitors. ADMET analysis and synthetic validation followed by cell cytotoxicity further helps in shortlisting the 5 most effective payloads for further confirmation in preclinical setting. Additionally, molecular dynamics simulation was performed to confirm the structural stability and conformational dynamics of the Beta-tubulin-ligand complexes over a 100 ns simulation. In conclusion, this study effectively utilizes extensive compound databases and multi-stage screening methods to identify potent payloads, demonstrating promising advancements in discovering effective anticancer therapies.

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.

Rebastinib inhibits FoxO1 activity and reduces dexamethasone-induced atrophy and its-related gene expression in cultured myotubes

FoxO1, a transcription factor, is upregulated in skeletal muscle during atrophy and inactivation of FoxO1 is a potential strategy to prevent muscle loss. This study identified Rebastinib as a potent suppressor of FoxO1 activity among protein kinase inhibitors. To determine whether Rebastinib inhibits atrophy-related ubiquitin ligases gene expression and mitigates atrophy in mouse skeletal muscle-derived cells, we investigated its protective effects of the compound against dexamethasone (DEX)-induced muscle atrophy using C2C12 myotubes. Rebastinib inhibited the DEX-induced upregulation of atrogin-1 and MuRF-1 mRNA, and atrogin-1 protein. Rebastinib also suppressed protein degradation and increased myotube diameter in DEX-treated C2C12 myotubes. Additionally, Rebastinib ameliorated the DEX- and cachexia-induced reduction in contractile force generation. Although the precise mechanisms underlying the action of Rebastinib against muscle atrophy and its efficacy in vivo remains to be elucidated, this compound shows great potential as a therapeutic agent for muscle atrophy.

The Tie2 antagonist rebastinib reduces ovarian cancer growth in a syngeneic murine model

BACKGROUND

The receptor tyrosine kinase TIE2 and its ligands, angiopoietins (ANGPTs), promote angiogenesis. In addition to expression on vascular endothelial cells, TIE2 is expressed on M2-like pro-tumorigenic macrophages. Thus, the TIE2 inhibitor rebastinib was developed as a potential therapy to address multiple cancers. The objective of this study was to determine the effects of rebastinib alone and combined with chemotherapy in a syngeneic murine model of ovarian cancer.

METHODS

Female C57Bl6J mice were intraperitoneally injected with syngeneic ID8 ovarian cancer cells. Once tumors were established, mice were untreated (control) or treated with rebastinib, carboplatin plus paclitaxel (chemotherapy), or rebastinib plus chemotherapy. In one set of experiments, survival was followed for 140 days. In other experiments, ascites was harvested 24 h after the last treatment and analyzed by flow cytometry. In in vitro experiments, RNA sequencing was performed on ID8 cells and murine peritoneal macrophage cells (PMJ2R) after treatment with rebastinib, chemotherapy, or rebastinib plus chemotherapy.

RESULTS

Tumor-bearing mice treated with rebastinib plus chemotherapy had longer median survival than mice treated with chemotherapy (132.5 vs. 127 days, P < 0.01). Ascites from mice treated with rebastinib had more CD45 + macrophages (P < 0.03) and cytotoxic T cells (P < 0.0001) than ascites from mice treated with chemotherapy. Rebastinib had no significant effect on the numbers of regulatory T cells, Tie2 + macrophages, or Tie2 + M2 macrophages. In ID8 cells, in vitro, rebastinib treatment upregulated 1528 genes and downregulated 3115 genes. In macrophages, in vitro, rebastinib treatment upregulated 2302 genes and downregulated 2970 genes. Rebastinib differentially regulated ANGPT-like proteins in both types of cells, including several ANGPT-like genes involved in tumorigenesis, angiogenesis, and proliferation. ANGPTL1, an anti-angiogenic and anti-apoptotic gene, was increased tenfold in ID8 cells treated with rebastinib (P < 0.001) but was not altered in macrophages.

CONCLUSIONS

Rebastinib plus chemotherapy extends survival in a syngeneic murine model of ovarian cancer. Rebastinib alters proportions of immune cell subsets, increases cytotoxic T cells in ascites, and alters gene expression in tumor cells and macrophages.

Phase Ib Clinical and Pharmacodynamic Study of the TIE2 Kinase Inhibitor Rebastinib with Paclitaxel or Eribulin in HER2-Negative Metastatic Breast Cancer

PURPOSE

Breast cancer cells disseminate to distant sites via tumor microenvironment of metastasis (TMEM) doorways. The TIE2 inhibitor rebastinib blocks TMEM doorway function in the PyMT mouse model of breast cancer. We aimed to assess the safety and pharmacodynamics of rebastinib plus paclitaxel or eribulin in patients with HER2-negative metastatic breast cancer (MBC).

PATIENTS AND METHODS

This phase Ib trial enrolled 27 patients with MBC who received 50 mg or 100 mg of rebastinib orally twice daily in combination with weekly paclitaxel 80 mg/m2 (if ≤2 prior non-taxane regimens) or eribulin 1.4 mg/m2 on days 1 and 8 (if ≥1 prior regimen). Safety, tolerability, and pharmacodynamic parameters indicating TIE2 kinase inhibition and TMEM doorway function were evaluated.

RESULTS

No dose-limiting toxicities in cycle 1 or 2 were observed among the first 12 patients at either rebastinib dose level. The most common treatment-emergent adverse events were anemia (85%), fatigue (78%), anorexia (67%), leukopenia (67%), increased alanine aminotransferase (59%), hyperglycemia (56%), nausea (52%), and neutropenia (52%). Adverse events attributed to rebastinib include muscular weakness and myalgias. Intraocular pressure increased at the 100-mg rebastinib dose level, whereas angiopoietin-2 levels increased at both dose levels, providing pharmacodynamic evidence for TIE2 blockade. Circulating tumor cells decreased significantly with the combined treatment. Objective response occurred in 5/23 (22%) evaluable patients.

CONCLUSIONS

In patients with MBC, the recommended phase II dose of rebastinib associated with pharmacodynamic evidence of TIE2 inhibition is either 50 or 100 mg orally twice daily in combination with paclitaxel or eribulin.

AXL as immune regulator and therapeutic target in Acute Myeloid Leukemia: from current progress to novel strategies

Until recently, treatment options for patients diagnosed with Acute Myeloid Leukemia (AML) were limited and predominantly relied on various combinations, dosages, or schedules of traditional chemotherapeutic agents. Patients with advanced age, relapsed/refractory disease or comorbidities were often left without effective treatment options. Novel advances in the understanding of leukemogenesis at the molecular and genetic levels, alongside recent progress in drug development, have resulted in the emergence of novel therapeutic agents and strategies for AML patients. Among these innovations, the receptor tyrosine kinase AXL has been established as a promising therapeutic target for AML. AXL is a key regulator of several cellular functions, including epithelial-to-mesenchymal transition in tumor cells, immune regulation, apoptosis, angiogenesis and the development of chemoresistance. Clinical studies of AXL inhibitors, as single agents and in combination therapy, have demonstrated promising efficacy in treating AML. Additionally, novel AXL-targeted therapies, such as AXL-specific antibodies or antibody fragments, present potential solutions to overcome the limitations associated with traditional small-molecule AXL inhibitors or multikinase inhibitors. This review provides a comprehensive overview of the structure and biological functions of AXL under normal physiological conditions, including its role in immune regulation. We also summarize AXL's involvement in cancer, with a specific emphasis on its role in the pathogenesis of AML, its contribution to immune evasion and drug resistance. Moreover, we discuss the AXL inhibitors currently undergoing (pre)clinical evaluation for the treatment of AML.

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.

Harmonizing the craft of crafting clinically endorsed small-molecule BCR-ABL tyrosine kinase inhibitors for the treatment of hematological malignancies

The advancement and practical use of small-molecule tyrosine kinase inhibitors (TKIs) that specifically target the BCR-ABL fusion protein have introduced a revolutionary era of precision medicine for the treatment of chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL). This review offers a comprehensive exploration of the synthesis, mechanisms of action, and clinical implementation of clinically validated TKIs in the context of BCR-ABL, emphasizing the remarkable strides made in achieving therapeutic precision. We delve into the intricate design and synthesis of these small molecules, highlighting the synthetic strategies and modifications that have led to increased selectivity, enhanced binding affinities, and reduced off-target effects. Additionally, we discuss the structural biology of BCR-ABL inhibition and how it informs drug design. The success of these compounds in inhibiting aberrant kinase activity is a testament to the meticulous refinement of the synthetic process. Furthermore, this review provides a detailed analysis of the clinical applications of these TKIs, covering not only their efficacy in achieving deep molecular responses but also their impact on patient outcomes, safety profiles, and resistance mechanisms. We explore ongoing research efforts to overcome resistance and enhance the therapeutic potential of these agents. In conclusion, the synthesis and utilization of clinically validated small-molecule TKIs targeting BCR-ABL exemplify the transformative power of precision medicine in the treatment of hematological malignancies. This review highlights the evolving landscape of BCR-ABL inhibition and underscores the continuous commitment to refining and expanding the therapeutic repertoire for these devastating diseases.

Therapeutic targeting of angiopoietins in tumor angiogenesis and cancer development

The formation and progression of tumors in humans are linked to the abnormal development of new blood vessels known as neo-angiogenesis. Angiogenesis is a broad word that encompasses endothelial cell migration, proliferation, tube formation, and intussusception, as well as peri-EC recruitment and extracellular matrix formation. Tumor angiogenesis is regulated by angiogenic factors, out of which some of the most potent angiogenic factors such as vascular endothelial growth factor and Angiopoietins (ANGs) in the body are produced by macrophages and other immune cells within the tumor microenvironment. ANGs have a distinct function in tumor angiogenesis and behavior. ANG1, ANG 2, ANG 3, and ANG 4 are the family members of ANG out of which ANG2 has been extensively investigated owing to its unique role in modifying angiogenesis and its tight association with tumor progression, growth, and invasion/metastasis, which makes it an excellent candidate for therapeutic intervention in human malignancies. ANG modulators have demonstrated encouraging outcomes in the treatment of tumor development, either alone or in conjunction with VEGF inhibitors. Future development of more ANG modulators targeting other ANGs is needed. The implication of ANG1, ANG3, and ANG4 as probable therapeutic targets for anti-angiogenesis treatment in tumor development should be also evaluated. The article has described the role of ANG in tumor angiogenesis as well as tumor growth and the treatment strategies modulating ANGs in tumor angiogenesis as demonstrated in clinical studies. The pharmacological modulation of ANGs and ANG-regulated pathways that are responsible for tumor angiogenesis and cancer development should be evaluated for the development of future molecular therapies.

Activity of a TIE2 inhibitor (rebastinib) in a patient with a life-threatening cervicofacial venous malformation

Targeted therapy has become the first therapeutic option in many patients with vascular anomalies. A male 28-year-old patient presented a severe cervicofacial venous malformation involving half-lower face, anterior neck, and oral cavity with progression despite multiple previous treatments, with a somatic variant in TEK (endothelial-specific protein receptor tyrosine kinase) (c.2740C>T; p.Leu914Phe). The patient had facial deformity, daily episodes of pain and inflammation needing massive amount of medication, and difficulty in speech and swallowing, so rebastinib (a TIE2 kinase inhibitor) was approved for compassionate use. After 6 months of treatment, venous malformation had decreased in size and lightened, as well as improved quality-of-life scores.

The Importance of the Pyrazole Scaffold in the Design of Protein Kinases Inhibitors as Targeted Anticancer Therapies

The altered activation or overexpression of protein kinases (PKs) is a major subject of research in oncology and their inhibition using small molecules, protein kinases inhibitors (PKI) is the best available option for the cure of cancer. The pyrazole ring is extensively employed in the field of medicinal chemistry and drug development strategies, playing a vital role as a fundamental framework in the structure of various PKIs. This scaffold holds major importance and is considered a privileged structure based on its synthetic accessibility, drug-like properties, and its versatile bioisosteric replacement function. It has proven to play a key role in many PKI, such as the inhibitors of Akt, Aurora kinases, MAPK, B-raf, JAK, Bcr-Abl, c-Met, PDGFR, FGFRT, and RET. Of the 74 small molecule PKI approved by the US FDA, 8 contain a pyrazole ring: Avapritinib, Asciminib, Crizotinib, Encorafenib, Erdafitinib, Pralsetinib, Pirtobrutinib, and Ruxolitinib. The focus of this review is on the importance of the unfused pyrazole ring within the clinically tested PKI and on the additional required elements of their chemical structures. Related important pyrazole fused scaffolds like indazole, pyrrolo[1,2-b]pyrazole, pyrazolo[4,3-b]pyridine, pyrazolo[1,5-a]pyrimidine, or pyrazolo[3,4-d]pyrimidine are beyond the subject of this work.

Small molecule inhibitors targeting the cancers

Compared with traditional therapies, targeted therapy has merits in selectivity, efficacy, and tolerability. Small molecule inhibitors are one of the primary targeted therapies for cancer. Due to their advantages in a wide range of targets, convenient medication, and the ability to penetrate into the central nervous system, many efforts have been devoted to developing more small molecule inhibitors. To date, 88 small molecule inhibitors have been approved by the United States Food and Drug Administration to treat cancers. Despite remarkable progress, small molecule inhibitors in cancer treatment still face many obstacles, such as low response rate, short duration of response, toxicity, biomarkers, and resistance. To better promote the development of small molecule inhibitors targeting cancers, we comprehensively reviewed small molecule inhibitors involved in all the approved agents and pivotal drug candidates in clinical trials arranged by the signaling pathways and the classification of small molecule inhibitors. We discussed lessons learned from the development of these agents, the proper strategies to overcome resistance arising from different mechanisms, and combination therapies concerned with small molecule inhibitors. Through our review, we hoped to provide insights and perspectives for the research and development of small molecule inhibitors in cancer treatment.

YES1: a novel therapeutic target and biomarker in cancer

YES1 is a non-receptor tyrosine kinase that belongs to the SRC family of kinases (SFKs) and controls multiple cancer signaling pathways. YES1 is amplified and overexpressed in many tumor types, where it promotes cell proliferation, survival and invasiveness. Therefore, YES1 has been proposed as an emerging target in solid tumors. In addition, studies have shown that YES1 is a prognostic biomarker and a predictor of dasatinib activity. Several SFKs-targeting drugs have been developed and some of them have reached clinical trials. However, these drugs have encountered challenges to their utilization in the clinical practice in unselected patients due to toxicity and lack of efficacy. In the case of YES1, novel specific inhibitors have been developed and tested in preclinical models, with impressive antitumor effects. In this review, we summarize the structure and activation of YES1 and describe its role in cancer as a target and prognostic and companion biomarker. We also address the efficacy of SFKs inhibitors that are currently in clinical trials, highlighting the main hindrances for their clinical use. Current available information strongly suggests that inhibiting YES1 in tumors with high expression of this protein is a promising strategy against cancer.

The progress of small-molecules and degraders against BCR-ABL for the treatment of CML

Chronic myeloid leukemia (CML) is a malignant disease of the hematopoietic system with crucial pathogenic protein named BCR-ABL, which endangers the life of patients severely. As a milestone of targeted drug, Imatinib has achieved great success in the treatment of CML. Nevertheless, inevitable drug resistance of Imatinib has occurred frequently in clinical due to the several mutations in the BCR-ABL kinase. Subsequently, the second-generation of tyrosine kinase inhibitors (TKIs) against BCR-ABL was developed to address the mutants of Imatinib resistance, except T315I. To date, the third-generation of TKIs targeting T315I has been developed for improving the selectivity and safety. Notably, the first allosteric inhibitor has been in market which could overcome the mutations in ATP binding site effectively. Meanwhile, some advanced technology, such as proteolysis-targeting chimeras (PROTAC) based on different E3 ligand, are highly expected to overcome the drug resistance by selectively degrading the targeted proteins. In this review, we summarized the current research progress of inhibitors and degraders targeting BCR-ABL for the treatment of CML.

Chronic myeloid leukemia stem cells: targeting therapeutic implications

Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasm driven by BCR-ABL1 oncoprotein, which plays a pivotal role in CML pathology, diagnosis, and treatment as confirmed by the success of tyrosine kinase inhibitor (TKI) therapy. Despite advances in the development of more potent tyrosine kinase inhibitors, some mechanisms particularly in terms of CML leukemic stem cell (CML LSC) lead to intrinsic or acquired therapy resistance, relapse, and disease progression. In fact, the maintenance CML LSCs in patients who are resistance to TKI therapy indicates the role of CML LSCs in resistance to therapy through survival mechanisms that are not completely dependent on BCR-ABL activity. Targeting therapeutic approaches aim to eradicate CML LSCs through characterization and targeting genetic alteration and molecular pathways involving in CML LSC survival in a favorable leukemic microenvironment and resistance to apoptosis, with the hope of providing a functional cure. In other words, it is possible to develop the combination therapy of TKs with drugs targeting genes or molecules more specifically, which is required for survival mechanisms of CML LSCs, while sparing normal HSCs for clinical benefits along with TKIs.

Role of lymphatic endothelial cells in the tumor microenvironment-a narrative review of recent advances

Background

As lymphatic vessel is a major route for solid tumor metastasis, they are considered an essential part of tumor drainage conduits. Apart from forming the walls of lymphatic vessels, lymphatic endothelial cells (LECs) have been found to play multiple other roles in the tumor microenvironment, calling for a more in-depth review. We hope that this review may help researchers gain a detailed understanding of this fast-developing field and shed some light upon future research.

Methods

To achieve an informative review of recent advance, we carefully searched the Medline database for English literature that are openly published from the January 1995 to December 2020 and covered the topic of LEC or lymphangiogenesis in tumor progression and therapies. Two different authors independently examined the literature abstracts to exclude possible unqualified ones, and 310 papers with full texts were finally retrieved.

Results

In this paper, we discussed the structural and molecular basis of tumor-associated LECs, together with their roles in tumor metastasis and drug therapy. We then focused on their impacts on tumor cells, tumor stroma, and anti-tumor immunity, and the molecular and cellular mechanisms involved. Special emphasis on lung cancer and possible therapeutic targets based on LECs were also discussed.

Conclusions

LECs can play a much more complex role than simply forming conduits for tumor cell dissemination. Therapies targeting tumor-associated lymphatics for lung cancer and other tumors are promising, but more research is needed to clarify the mechanisms involved.

Computational and Biological Investigations on Abl1 Tyrosine Kinase: A Review

Abl1 tyrosine kinase is a validated target for the treatment of chronic myeloid leukemia. It is a form of cancer that is difficult to treat and much research is being done to identify new molecular entities and to tackle drug resistance issues. In recent years, drug resistance of Abl1 tyrosine kinase has become a major healthcare concern. Second and third-generation TKI reported better responses against the resistant forms; still they had no impact on long-term survival prolongation. New compounds derived from natural products and organic small molecule inhibitors can lay the foundation for better clinical therapies in the future. Computational methods, experimental and biological studies can help us understand the mechanism of drug resistance and identify novel molecule inhibitors. ADMET parameters analysis of reported drugs and novel small molecule inhibitors can also provide valuable insights. In this review, available therapies, point mutations, structure-activity relationship and ADMET parameters of reported series of Abl1 tyrosine kinase inhibitors and drugs are summarised. We summarise in detail recent computational and molecular biology studies that focus on designing drug molecules, investigation of natural product compounds and organic new chemical entities. Current ongoing research suggests that selective targeting of Abl1 tyrosine kinase at the molecular level to combat drug resistance in chronic myeloid leukemia is promising.

Management of a 75-Year-Old Lady with Refractory Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is a hematopoietic disorder caused by the BCR/ABL gene or Philadelphia chromosome. The first Food and Drug Administration (FDA)-approved tyrosine kinase inhibitor for treatment of CML was imatinib in 2001. Since then, multiple therapies, such as nilotinib, dasatinib, bosutinib, and, more recently, ponatinib, have made their way as viable treatment options for first-line and secondary therapies. Most patients tend to respond to first-line treatment. Although there is a subset of patients who do not achieve complete molecular response with first line, newer options have proven beneficial. As we progress through therapies, there still remain some patients who do not adequately respond to current available therapies. The treatment options and guidelines become more difficult in such situations, not only with respect to cost but also patient quality of life and satisfaction. We discuss a 75-year-old white female with CML, who has had multiple therapies with hematological remission but has never achieved complete molecular remission, currently on bosutinib and tolerating it well.

Communication Of Cancer Cells And Lymphatic Vessels In Cancer: Focus On Bladder Cancer

Bladder cancer is one of the most commonly diagnosed cancers worldwide and causes the highest lifetime treatment costs per patient. Bladder cancer is most likely to metastasize through lymphatic ducts, and once the lymph nodes are involved, the prognosis is poorly and finitely improved by current modalities. The underlying metastatic mechanism for bladder cancer is thus becoming a research focus to date. To identify relevant published data, an online search of the PubMed/Medline archives was performed to locate original articles and review articles regarding lymphangiogenesis and lymphatic metastasis in urinary bladder cancer (UBC), and was limited to articles in English published between 1998 and 2018. A further search of the clinical trials.gov search engine was conducted to identify both trials with results available and those with results not yet available. Herein, we summarized the unique mechanisms and biomarkers involved in the malignant progression of bladder cancer as well as their emerging roles in therapeutics, and that current data suggests that lymphangiogenesis and lymph node invasion are important prognostic factors for UBC. The growing knowledge about their roles in bladder cancers provides the basis for novel therapeutic strategies. In addition, more basic and clinical research needs to be conducted in order to identify further accurate predictive molecules and relevant mechanisms.

Synthesis, Biological Activities and Docking Studies of Novel 4-(Arylaminomethyl)benzamide Derivatives as Potential Tyrosine Kinase Inhibitors

A number of new compounds containing the 4-(aminomethyl)benzamide fragment as a linker were designed and synthesized, and their biological activities were evaluated as potential anticancer agents. The cytotoxicity activity of the designed compounds was studied in two hematological and five solid cell lines in comparison with the reference drugs. Targeted structures against eight receptor tyrosine kinases including EGFR, HER-2, HER-4, IGF1R, InsR, KDR, PDGFRa, and PDGFRb were investigated. The majority of the compounds showed a potent inhibitory activity against the tested kinases. The analogues 11 and 13 with the (trifluoromethyl)benzene ring in the amide or amine moiety of the molecule were proven to be highly potent against EGFR, with 91% and 92% inhibition at 10 nM, respectively. The docking of synthesized target compounds for nine protein kinases contained in the Protein Data Bank (PDB) database was carried out. The molecular modeling results for analogue 10 showed that the use of the 4-(aminomethyl)benzamide as a flexible linker leads to a favorable overall geometry of the molecule, which allows one to bypass the bulk isoleucine residue and provides the necessary binding to the active center of the T315I-mutant Abl (PDB: 3QRJ).

Receptor tyrosine kinases in PI3K signaling: The therapeutic targets in cancer

The phosphoinositide 3-kinase (PI3K) pathway, one of the most commonly activated signaling pathways in human cancers, plays a crucial role in the regulation of cell proliferation, differentiation, and survival. This pathway is usually activated by receptor tyrosine kinases (RTKs), whose constitutive and aberrant activation is via gain-of-function mutations, chromosomal rearrangement, gene amplification and autocrine. Blockage of PI3K pathway by targeted therapy on RTKs with tyrosine kinases inhibitors (TKIs) and monoclonal antibodies (mAbs) has achieved great progress in past decades; however, there still remain big challenges during their clinical application. In this review, we provide an overview about the most frequently encountered alterations in RTKs and focus on current therapeutic agents developed to counteract their aberrant functions, accompanied with discussions of two major challenges to the RTKs-targeted therapy in cancer - resistance and toxicity.

Insights into the optimal use of ponatinib in patients with chronic phase chronic myeloid leukaemia

There are five tyrosine kinase inhibitors (TKIs) that are currently approved (in the European Union and the United States) for the treatment of chronic myeloid leukaemia (CML) in the chronic phase (CP) and each of them has its own efficacy and toxicity profile. Oral ponatinib (Iclusig^®) is a third-generation TKI structurally designed to inhibit native BCR-ABL1 tyrosine kinase and several BCR-ABL1 mutants, including T315I. Ponatinib is now approved for patients with CML who are resistant or intolerant to prior TKI therapy (European Union) or for whom no other TKI therapy is indicated (United States). Despite achieving results in heavily treated patients, which led to its approval, the drug may induce cardiovascular events, requiring a careful baseline assessment of predisposing risk factors and specific management during treatment. Pharmacokinetic analysis has indicated the possibility of reducing the starting dose of ponatinib to 15 mg/day and preliminary data showed advantages in terms of safety while maintained its efficacy. This review summarizes the results achieved and drug-related side effects reported in all clinical trials and real-life experiences, testing ponatinib in patients with CP-CML. In addition, we focus on the appropriate use of ponatinib in clinical practice suggesting some useful recommendations on the proper management of this drug.

Angiopoietin-1 and Angiopoietin-2 Inhibitors: Clinical Development

PURPOSE OF REVIEW

The purpose of this review is to discuss the current understanding of the Tie2-angiopoietin system and its role in tumor growth and metastasis. This review also focuses on preclinical and clinical data published to date that have evaluated Tie2-angiopoietin inhibition.

RECENT FINDINGS

Tie2 inhibition has shown significant promise in preclinical models, notable for decreased tumor burden and fewer sites of metastatic disease across various malignancies. However, data from human clinical trials have shown more mixed results. Trebananib, rebastanib, and MEDI3617 are the three Tie2-angiopoietin inhibitors that have been most widely evaluated in phase I and II trials. Further investigation into these therapies is ongoing. The Tie2-angiopoietin pathway continues to show promise in preclinical and some clinical trials, including studies on recurrent or metastatic breast and renal cell carcinomas. Further evaluation of these therapies, however, is warranted to better understand their optimal clinical utility.

Resistance in chronic myeloid leukemia: definitions and novel therapeutic agents

PURPOSE OF REVIEW

Chronic myeloid leukemia (CML) is hallmarked by the presence of fusion protein kinase derived from a reciprocal translocation between chromosome 9 and 22, breakpoint cluster region (BCR)-Abelson leukemia virus (ABL) 1, causing aberrant regulation of the downstream pathways leading to unchecked CML leukemia stem cells (LSCs) proliferation. Since the discovery of tyrosine kinase inhibitors (TKI), CML, once a fatal disease, has become a chronic illness if managed appropriately. Changing treatment landscape has unsurfaced the challenge of TKI resistance that is clinically difficult to overcome.

RECENT FINDINGS

In this review, we discuss the concept of TKI resistance and pathways leading to the resistance which allows for a survival advantage to CML LSCs. Aside from BCR-ABL-dependent mechanisms of resistance which involves aberrant expression in the regulatory pumps involving efflux and influx of the TKI affecting drug bioavailability, activation of alternate survival pathways may be accountable for primary or secondary resistance. Activation of these pathways, intrinsically and extrinsically to LSCs, may be mediated through various upstream and downstream signaling as well as conditions affecting the microenvironment. Several therapeutic approaches that combine TKI with an additional agent that inhibits the activation of an alternate pathway have been studied as part of clinical trials which we will discuss here.

SUMMARY

We categorize the resistance into BCR-ABL-dependent and BCR-ABL-independent subgroups to further describe the complex molecular pathways which can potentially serve as a therapeutic target. We further discuss novel combination strategies currently in early or advanced phase clinical trials aimed to overcome the TKI resistance. We further highlight the need for further research despite the tremendous strides already made in the management of CML.

Past, present, and future of Bcr-Abl inhibitors: from chemical development to clinical efficacy

Bcr-Abl inhibitors paved the way of targeted therapy epoch. Imatinib was the first tyrosine kinase inhibitor to be discovered with high specificity for Bcr-Abl protein resulting from t(9, 22)-derived Philadelphia chromosome. Although the specific targeting of that oncoprotein, several Bcr-Abl-dependent and Bcr-Abl-independent mechanisms of resistance to imatinib arose after becoming first-line therapy in chronic myelogenous leukemia (CML) treatment.Consequently, new specific drugs, namely dasatinib, nilotinib, bosutinib, and ponatinib, were rationally designed and approved for clinic to override resistances. Imatinib fine mechanisms of action had been elucidated to rationally develop those second- and third-generation inhibitors. Crystallographic and structure-activity relationship analysis, jointly to clinical data, were pivotal to shed light on this topic. More recently, preclinical evidence on bafetinib, rebastinib, tozasertib, danusertib, HG-7-85-01, GNF-2, and 1,3,4-thiadiazole derivatives lay promising foundations for better inhibitors to be approved for clinic in the near future.Notably, structural mechanisms of action and drug design exemplified by Bcr-Abl inhibitors have broad relevance to both break through resistances in CML treatment and develop inhibitors against other kinases as targeted chemotherapeutics.

Novel tyrosine-kinase inhibitors for the treatment of chronic myeloid leukemia: safety and efficacy

INTRODUCTION

Chronic myeloid leukemia (CML) is characterized by a pathognomonic chromosomal translocation, which leads to the fusion of breakpoint cluster region (BCR) and Abelson leukemia virus 1 (ABL1) genes, generating an oncoprotein with deregulated tyrosine kinase activity. Areas covered: In the last two decades, BCR/ABL1 kinase has become the molecular target for tyrosine kinase inhibitors (TKIs), a class of drugs that impressively improved overall survival. Despite these results, a proportion of patients experiences resistance to TKIs and need to change treatment. Furthermore, TKIs are unable to eradicate leukemic stem cells, allowing the persistence of neoplastic clones. Therefore, there is still clinical need for new agents to overcome common resistance mechanisms to available drugs. This review explores the horizon of drugs actually under investigation for CML patients resistant to conventional treatment. Expert commentary: Radotinib is an ATP-competitive TKI that showed significant activity also in front-line setting and could find employment indications in CML. Asciminib, an allosteric ABL1 inhibitor, could demonstrate a higher capacity in overcoming common TKIs resistant mutations, including T315I, but clinical findings are needed. CML stem cell target will probably require new therapeutic strategies: combinations of several compounds acting with different mechanisms of action are actually under investigation.

The Selective Tie2 Inhibitor Rebastinib Blocks Recruitment and Function of Tie2Hi Macrophages in Breast Cancer and Pancreatic Neuroendocrine Tumors

Tumor-infiltrating myeloid cells promote tumor progression by mediating angiogenesis, tumor cell intravasation, and metastasis, which can offset the effects of chemotherapy, radiation, and antiangiogenic therapy. Here, we show that the kinase switch control inhibitor rebastinib inhibits Tie2, a tyrosine kinase receptor expressed on endothelial cells and protumoral Tie2-expressing macrophages in mouse models of metastatic cancer. Rebastinib reduces tumor growth and metastasis in an orthotopic mouse model of metastatic mammary carcinoma through reduction of Tie2⁺ myeloid cell infiltration, antiangiogenic effects, and blockade of tumor cell intravasation mediated by perivascular Tie2^Hi/Vegf-A^Hi macrophages in the tumor microenvironment of metastasis (TMEM). The antitumor effects of rebastinib enhance the efficacy of microtubule inhibiting chemotherapeutic agents, either eribulin or paclitaxel, by reducing tumor volume, metastasis, and improving overall survival. Rebastinib inhibition of angiopoietin/Tie2 signaling impairs multiple pathways in tumor progression mediated by protumoral Tie2⁺ macrophages, including TMEM-dependent dissemination and angiopoietin/Tie2-dependent angiogenesis. Rebastinib is a promising therapy for achieving Tie2 inhibition in cancer patients. Mol Cancer Ther; 16(11); 2486-501. ©2017 AACR.