Venetoclax: A new wave in hematooncology

Advancing the understanding of venetoclax in t(11;14)-positive multiple myeloma: a comprehensive review of clinical evidence and future prospects

Venetoclax is a selective inhibitor of the anti-apoptotic protein B-cell lymphoma 2 (BCL2), as a targeted therapy for multiple myeloma (MM) patients. It was initially approved by the United States Food and Drug Administration for the treatment of chronic lymphocytic leukemia in April 2016 and later for acute myeloid leukemia in October 2020. However, venetoclax is used as an off-label in a subset group of relapsed and refractory multiple myeloma (RRMM) patients with the presence of translocation t(11;14). Preclinical and clinical studies have highlighted the potential of venetoclax in the management of MM patients, with a specific focus on t(11;14) as a predictive biomarker for initiating venetoclax-based treatment. Later, several studies in RRMM patients that used venetoclax in combination with dexamethasone or/and proteasome inhibitors have shown promising results, in which management guidelines have included venetoclax as one of the options to treat MM patients. Hence, this review focuses on the use of venetoclax in RRMM, clinical efficacy, safety, dosing strategies, and predictive biomarkers for initiating venetoclax. Additionally, we discuss ongoing studies that are investigating different combination of venetoclax regimens in MM patients.

Directly targeting BAX for drug discovery: Therapeutic opportunities and challenges

For over two decades, the development of B-cell lymphoma-2 (Bcl-2) family therapeutics has primarily focused on anti-apoptotic proteins, resulting in the first-in-class drugs called BH3 mimetics, especially for Bcl-2 inhibitor Venetoclax. The pro-apoptotic protein Bcl-2-associated X protein (BAX) plays a crucial role as the executioner protein of the mitochondrial regulated cell death, contributing to organismal development, tissue homeostasis, and immunity. The dysregulation of BAX is closely associated with the onset and progression of diseases characterized by pathologic cell survival or death, such as cancer, neurodegeneration, and heart failure. In addition to conducting thorough investigations into the physiological modulation of BAX, research on the regulatory mechanisms of small molecules identified through biochemical screening approaches has prompted the identification of functional and potentially druggable binding sites on BAX, as well as diverse all-molecule BAX modulators. This review presents recent advancements in elucidating the physiological and pharmacological modulation of BAX and in identifying potentially druggable binding sites on BAX. Furthermore, it highlights the structural and mechanistic insights into small-molecule modulators targeting diverse binding surfaces or conformations of BAX, offering a promising avenue for developing next-generation apoptosis modulators to treat a wide range of diseases associated with dysregulated cell death by directly targeting BAX.

COVID-19 severity in patients with chronic lymphocytic leukemia treated with venetoclax: a single-center observational cohort study

Patients with chronic lymphocytic leukemia (CLL) are at high risk of developing severe COVID-19. The present study was undertaken to elucidate COVID-19 related morbidity and mortality in CLL patients treated with venetoclax. We present a single-center study of 108 patients with small lymphocytic lymphoma or CLL treated with venetoclax. Primary outcome was 30-day COVID-19 mortality. Secondary outcomes included COVID-19 severity and hospitalization rate. Forty-eight (44%) patients had PCR-verified SARS-COV-2 between March 2020 and January 2023. Thirty-six patients (75%) presented with asymptomatic/mild COVID-19 and 12 (25%) with severe/critical disease. The hospitalization rate was 46% with a 30-day mortality rate of only 4% and severe comorbidities as the primary cause of death. COVID-19 severity and mortality were similar before and during the Omicron era. High CIRS-scores (P < 0.02) and thrombocytopenia (P < 0.01) were more frequent in patients with severe/critical disease. In real-world data, most venetoclax treated patients presented with mild COVID-19. Hospitalization and mortality rates were low compared to data of general CLL populations. Our data indicate that venetoclax was a safe treatment option for CLL patients during the pandemic.

A Novel Approach for Glioblastoma Treatment by Combining Apoptosis Inducers (TMZ, MTX, and Cytarabine) with E.V.A. (Eltanexor, Venetoclax, and A1210477) Inhibiting XPO1, Bcl-2, and Mcl-1

Adjuvant treatment for Glioblastoma Grade 4 with Temozolomide (TMZ) inevitably fails due to therapeutic resistance, necessitating new approaches. Apoptosis induction in GB cells is inefficient, due to an excess of anti-apoptotic XPO1/Bcl-2-family proteins. We assessed TMZ, Methotrexate (MTX), and Cytarabine (Ara-C) (apoptosis inducers) combined with XPO1/Bcl-2/Mcl-1-inhibitors (apoptosis rescue) in GB cell lines and primary GB stem-like cells (GSCs). Using CellTiter-Glo® and Caspase-3 activity assays, we generated dose-response curves and analyzed the gene and protein regulation of anti-apoptotic proteins via PCR and Western blots. Optimal drug combinations were examined for their impact on the cell cycle and apoptosis induction via FACS analysis, paralleled by the assessment of potential toxicity in healthy mouse brain slices. Ara-C and MTX proved to be 150- to 10,000-fold more potent in inducing apoptosis than TMZ. In response to inhibitors Eltanexor (XPO1; E), Venetoclax (Bcl-2; V), and A1210477 (Mcl-1; A), genes encoding for the corresponding proteins were upregulated in a compensatory manner. TMZ, MTX, and Ara-C combined with E, V, and A evidenced highly lethal effects when combined. As no significant cell death induction in mouse brain slices was observed, we conclude that this drug combination is effective in vitro and expected to have low side effects in vivo.

Use of venetoclax in t(11;14) positive relapsed/refractory multiple myeloma: A systematic review

BACKGROUND

The plasma cell malignancy, multiple myeloma (MM), remains incurable despite advanced treatment protocols. Overexpression of Bcl-2 (an anti-apoptotic protein), in MM harboring the translocation (11;14), contributes to resistance to prior therapy. Venetoclax, a selective oral inhibitor of BCL-2 is a novel agent that shows promise as a therapeutic agent.

AIMS

The objective of this systematic review is to address how the use of venetoclax, alone or as a combination regimen, contributed to the treatment of patients with t(11:14) positive relapsed/refractory multiple myeloma (RRMM).

DATA SOURCES

This systematic review was conducted in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was done on 5th June 2022. A literature search was conducted on PubMed and Scopus, 145 articles were screened and 10 studies were included. Risk of bias assessment was performed using the Methodological Index for Non-Randomized Studies (MINORS) criteria.

DATA SUMMARY

Across the studies reviewed, a total of 311 patients were identified with t(11;14) positive RRMM. The overall response rate achieved ranged between 33% and 95.5%. Furthermore, the use of venetoclax has exhibited a favorable adverse effect profile. Side effects included hematological side effects, nausea, vomiting, and diarrhea.

CONCLUSION

Venetoclax demonstrates promising results. When given with drugs like dexamethasone, daratumumab and carfilzomib, a synergistic effect is seen in treating translocation (11:14) positive relapsed/refractory MM. The use of venetoclax in clinical practice can potentially improve outcomes and quality of life in RRMM patients, and future research should continue to explore this promising treatment option.

Predicting transcription factor activity using prior biological information

Dysregulation of normal transcription factor activity is a common driver of disease. Therefore, the detection of aberrant transcription factor activity is important to understand disease pathogenesis. We have developed Priori, a method to predict transcription factor activity from RNA sequencing data. Priori has two key advantages over existing methods. First, Priori utilizes literature-supported regulatory information to identify transcription factor-target gene relationships. It then applies linear models to determine the impact of transcription factor regulation on the expression of its target genes. Second, results from a third-party benchmarking pipeline reveals that Priori detects aberrant activity from 124 single-gene perturbation experiments with higher sensitivity and specificity than 11 other methods. We applied Priori and other top-performing methods to predict transcription factor activity from two large primary patient datasets. Our work demonstrates that Priori uniquely discovered significant determinants of survival in breast cancer and identified mediators of drug response in leukemia.

More than the Infinite Monkey Theorem: NHP Models in the Development of a Pediatric HIV Cure

PURPOSE OF REVIEW

An HIV cure that eliminates the viral reservoir or provides viral control without antiretroviral therapy (ART) is an urgent need in children as they face unique challenges, including lifelong ART adherence and the deleterious effects of chronic immune activation. This review highlights the importance of nonhuman primate (NHP) models in developing an HIV cure for children as these models recapitulate the viral pathogenesis and persistence.

RECENT FINDINGS

Several cure approaches have been explored in infant NHPs, although knowledge gaps remain. Broadly neutralizing antibodies (bNAbs) show promise for controlling viremia and delaying viral rebound after ART interruption but face administration challenges. Adeno-associated virus (AAV) vectors hold the potential for sustained bNAb expression. Therapeutic vaccination induces immune responses against simian retroviruses but has yet to impact the viral reservoir. Combining immunotherapies with latency reversal agents (LRAs) that enhance viral antigen expression should be explored. Current and future cure approaches will require adaptation for the pediatric immune system and unique features of virus persistence, for which NHP models are fundamental to assess their efficacy.

LC-MS/MS methods for determination of venetoclax in human plasma and cerebrospinal fluid

We developed and validated sensitive MS/MS methods for the determination of venetoclax, an oral selective B-cell lymphoma-2 inhibitor, in human plasma and cerebrospinal fluid (CSF). Acetonitrile was used as protein precipitant. The mobile phase was 10 mM ammonium formate consisting of 0.1% formic acid and acetonitrile (40:60, v/v). The analytes were separated on an ACQUITY UPLC HSS T3 column (2.1 × 50 mm, 1.8 μm) in 5 min. An API 4000 mass spectrometer was selected to quantify venetoclax and internal standard using m/z 868.3 → 636.3 and 876.3 → 644.3 under multiple response monitoring mode. In plasma, the calibration curve exhibited good linearity ranging from 20.0 to 5000 ng/mL, whereas in the CSF, the linear range was 0.500-100 ng/mL. The matrix effect of venetoclax and internal standard (venetoclax-d8) was not obvious in both plasma and CSF. The inter- and intra-run accuracy was within ±11.9%, and the inter- and intra-run precision was below 13.6%. Both methods had no carryover, and the recovery was close to 100%. The validated methods were employed to quantify the concentrations of venetoclax in the plasma and CSF of patients diagnosed with chronic lymphocytic leukemia or acute myelogenous leukemia.

Venetoclax combined with hypomethylating agents and the CAG regimen in relapsed/refractory AML: a single-center clinical trial

Objective

This study aimed to evaluate the efficacy and safety of venetoclax in combination with hypomethylating agents and CAG (VEN-DCAG) regimens in patients with relapsed/refractory acute myeloid leukemia (R/R AML).

Methods

The treatment response was analyzed by retrospective methods in R/R AML patients treated with the VEN-DCAG regimen at our institution. This included, but was not limited to, CR/CRi (complete remission/complete remission with incomplete hematologic recovery) rate, measurable residual disease (MRD) negative rate, and overall survival (OS).

Results

20 patients with R/R AML were recruited, with a median age of 40 years (10-70), 11 of whom were male (55%), and a median follow-up of 10.4 months (0.7-21.8). The overall response rate (ORR) after receiving 1 course of VEN-DCAG was 90% (18/20), with 17 (85%) CR/CRi (10 MRD-CR), 1 (5%) PR, and 2 (10%) NR. Subsequently, 12 patients (7 MRD-CR, 4 MRD+CR, 1 NR) were treated with the VEN-DCAG regimen, and 3 MRD+CR patients turned negative, and 13 patients finally achieved MRD-CR. Among them, 7 patients were in the relapse group, all achieving CR/CRi (6 MRD-CR), and 13 patients in the refractory group, with 10 CR/CRi (7 MRD-CR). The ORR for patients in the relapse and refractory groups was 100% (7/7) and 84.6% (11/13), respectively. Further, all patients experienced adverse events (AEs) of varying degrees of severity, with hematologic AEs primarily consisting of myelosuppression, while non-hematologic AEs were more common in the form of fever, gastrointestinal distress, and infections. 11 patients were followed up with bridging allogeneic hematopoietic stem cell transplantation (allo-HSCT) therapy. At the last follow-up, 11 patients (7 MRD-CR, 4 MRD+CR) who received allo-HSCT, 1 (MRD+CR) died, and 9 patients (6 MRD-CR, 1 PR, 2 NR) who did not receive allo-HSCT, 5 (2 MRD-CR, 1 PR, 2 NR) died as well.

Conclusion

The VEN-DCAG regimen may be an effective treatment option for R/R AML patients, with high ORR and MRD negative remission rates in both the relapsed and refractory groups. It is recommend that patients should be bridged to allo-HSCT as soon as possible after induction to CR by the VEN-DCAG regimen, which can lead to a significant long-term survival benefit.

Clinical trial registration

https://www.chictr.org.cn/, identifier ChiCTR2300075985.

Ellagic Acid and Cancer Hallmarks: Insights from Experimental Evidence

Cancer is a complex and multifaceted disease with a high global incidence and mortality rate. Although cancer therapy has evolved significantly over the years, numerous challenges persist on the path to effectively combating this multifaceted disease. Natural compounds derived from plants, fungi, or marine organisms have garnered considerable attention as potential therapeutic agents in the field of cancer research. Ellagic acid (EA), a natural polyphenolic compound found in various fruits and nuts, has emerged as a potential cancer prevention and treatment agent. This review summarizes the experimental evidence supporting the role of EA in targeting key hallmarks of cancer, including proliferation, angiogenesis, apoptosis evasion, immune evasion, inflammation, genomic instability, and more. We discuss the molecular mechanisms by which EA modulates signaling pathways and molecular targets involved in these cancer hallmarks, based on in vitro and in vivo studies. The multifaceted actions of EA make it a promising candidate for cancer prevention and therapy. Understanding its impact on cancer biology can pave the way for developing novel strategies to combat this complex disease.

The effects of STA-9090 (Ganetespib) and venetoclax (ABT-199) combination on apoptotic pathways in human cervical cancer cells

Combined chemotherapy is recommended strategy as a first-line treatment method in patients with cervical cancer. Ganetespib (STA-9090) is a second-generation heat shock protein 90 (Hsp90) inhibitor that blocks the ATPase function of Hsp90 and inhibits the proper folding of oncogenic client proteins. Venetoclax (ABT-199) is an orally bioavailable Bcl-2 (B-cell lymphoma 2) inhibitor that stimulates apoptotic signaling pathways in cancer cells. This study evaluated the anticancer effects of STA-9090 combined with Venetoclax in the human cervical cancer cell line (HeLa). The human cervical cancer cells were treated with STA-9090, Venetoclax, and Sta-9090 plus Venetoclax for 48 h, and cell viability was measured using the XTT assay. The alteration of the Hsp90 protein expression level and the chaperone activity of HSP90 were detected by ELISA and luciferase aggregation assay, respectively. For the apoptotic process, qRT-PCR was applied to study Bcl-2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), Bcl-2-like protein 1 (Bcl-xL ), Cytochrome c (Cyt-c), Caspase3 (Cas-3), and Caspase7 (Cas-7) expression levels after drug treatments. Also, a colorimetric Cas-3 activity assay was performed to detect the induction of the apoptosis process. Our results demonstrated that 8 nM of STA-9090 combined with 4 µM of Venetoclax synergistically inhibited cervical cancer cell proliferation more than STA-9090 or Venetoclax alone after 48 h of treatment. STA-9090 and Venetoclax combination decreased the protein expression level of Hsp90 and significantly inhibited chaperone activity of Hsp90. This combination stimulated apoptosis in cervical cancer cells by down-regulating of anti-apoptotic markers while inducing pro-apoptotic markers. Also, the STA-9090-Venetoclax combination increased Cas-3 activity in Hela cells. Collectively, these findings pointed out that the STA-9090-Venetoclax combination exhibited more activity than the individual drugs to stimulate toxicity and apoptosis in cervical cancer cells based on HSP90 inhibition.

Therapeutic advancements in targeting BCL-2 family proteins by epigenetic regulators, natural, and synthetic agents in cancer

Cancer is amongst the deadliest and most disruptive disorders, having a much higher death rate than other diseases worldwide. Human cancer rates continue to rise, thereby posing the most significant concerns for medical health professionals. In the last two decades, researchers have gone past several milestones in tackling cancer while gaining insight into the role of apoptosis in cancer or targeting various biomarker tools for prognosis and diagnosis. Apoptosis which is still a topic full of complexities, can be controlled considerably by B-cell lymphoma 2 (BCL-2) and its family members. Therefore, targeting proteins of this family to prevent tumorigenesis, is essential to focus on the pharmacological features of the anti-apoptotic and pro-apoptotic members, which will help to develop and manage this disorder. This review deals with the advancements of various epigenetic regulators to target BCL-2 family proteins, including the mechanism of several microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Similarly, a rise in natural and synthetic molecules' research over the last two decades has allowed us to acquire insights into understanding and managing the transcriptional alterations that have led to apoptosis and treating various neoplastic diseases. Furthermore, several inhibitors targeting anti-apoptotic proteins and inducers or activators targeting pro-apoptotic proteins in preclinical and clinical stages have been summarized. Overall, agonistic and antagonistic mechanisms of BCL-2 family proteins conciliated by epigenetic regulators, natural and synthetic agents have proven to be an excellent choice in developing cancer therapeutics.

Efficacy and safety of venetoclax-based regimens for the treatment of relapsed/refractory multiple myeloma: a systemic review and meta-analysis

BACKGROUND

Patients with relapsed/refractory multiple myeloma (RRMM) usually have dismal prognostic outcomes. Venetoclax, a selective inhibitor of antiapoptotic protein B-cell lymphoma-2 (BCL-2), demonstrates antimyeloma activity in plasma cells with t(11;14) or high BCL-2 expression.

OBJECTIVES

This meta-analysis aimed to investigate the efficacy and safety of venetoclax-based therapy in RRMM.

DESIGN

This is a meta-analysis study.

DATA SOURCES AND METHODS

PubMed, Embase, and Cochrane were searched for studies published up to 20 December 2021. Overall response rate (ORR), rate of very good partial response or better (≧VGPR), and complete response (CR) rate were pooled with the random-effects model. Safety was evaluated by the incidences of grade ≧3 adverse events. Subgroup analysis and meta-regression were performed to identify the causes of heterogeneities. All the analyses were conducted by STATA 15.0 software.

RESULTS

A total of 14 studies with 713 patients were included for analysis. The pooled ORR, rate of ≧VGPR, and CR for all patients were 59% [95% confidence interval (CI) = 45-71%], 38% (95% CI = 26-51%), and 17% (95% CI = 10-26%), respectively. The median progression-free survival (PFS) ranged from 2.0 months to not reached (NR), and the median overall survival (OS) ranged from 12.0 months to NR. Meta-regression showed that patients treated with more drugs combined or less heavily pretreated had higher response rates. Patients with t(11;14) had superior ORR [relative risk (RR) = 1.47, 95% CI = 1.05-2.07], ≧VGPR (RR = 1.71, 95% CI = 1.12-2.60), CR (RR = 1.86, 95% CI = 1.34-2.57), PFS [hazard ratio (HR) = 0.47, 95% CI = 0.30-0.65], and OS (HR = 0.30, 95% CI = 0.08-0.52) compared with patients without t(11;14). Most grade ≧3 adverse events were hematologic, gastrointestinal, and infectious related and were manageable.

CONCLUSION

Venetoclax-based therapy is an effective and safe option for RRMM patients, especially those with t(11;14).

The Therapeutic Synergy of Selinexor and Venetoclax in Mantle Cell Lymphoma Through Induction of DNA Damage and Perturbation of the DNA Damage Response

Introduction: Mantle cell lymphoma (MCL) can be stratified into blastoid and classical subtypes based on morphological features, with the former subtype having a poorer prognosis. Despite recent advances in targeted approaches, including multiple bruton tyrosine kinase inhibitors which yield impressive clinical responses and improve prognoses, MCL remains an incurable disease with frequent relapses. Additional therapeutic interventions are therefore unmet medical needs for the management of patients with MCL. Methods: Cell viability and apoptosis assays were employed to analyze the therapeutic interaction of venetoclax combined with selinexor in MCL cells. Western blot was used to investigate the potential mechanism of action for the synergy of venetoclax in combination with selinexor in MCL cells. Results: In this study, we revealed that both blastoid and classical MCL cells were vulnerable to the cytotoxic effects of selinexor, a well-established XPO1 inhibitor, manifested by loss of cell viability and induction of cell apoptosis. Moreover, our data indicated that the addition of venetoclax to selinexor showed synergistically decreased cell viabilities and increased cell deaths in blastoid and classical MCL cells compared to each single drug treatment. Either selinexor or venetoclax treatment alone decreased MCL1 expressions and increased BAX levels in MCL cells, and these effects were further enhanced by their combined regimen. Mechanistically, our findings demonstrated that induction of DNA damage and inactivation of DNA damage response were involved in the synergistic interaction of the drug combination regimen. Conclusion: Collectively, this study might provide a potential attractive therapy option for the treatment of MCL. However, the conclusion needs additional experimental validation in in vivo models and clinical evaluations are mandatory.

Venetoclax Induces Cardiotoxicity through Modulation of Oxidative-Stress-Mediated Cardiac Inflammation and Apoptosis via NF-κB and BCL-2 Pathway

Cardiovascular damage induced by anticancer therapy has become the main health problem after tumor elimination. Venetoclax (VTX) is a promising novel agent that has been proven to have a high efficacy in multiple hematological diseases, especially acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL). Considering its mechanism of action, the possibility that VTX may cause cardiotoxicity cannot be ruled out. Therefore, this study was designed to investigate the toxic effect of VTX on the heart. Male Sprague-Dawley rats were randomly divided into three groups: control, low-dose VTX (50 mg/kg via oral gavage), and high-dose VTX (100 mg/kg via oral gavage). After 21 days, blood and tissue samples were collected for histopathological, biochemical, gene, and protein analyses. We demonstrated that VTX treatment resulted in cardiac damages as evidenced by major changes in histopathology and markedly elevated cardiac enzymes and hypertrophic genes markers. Moreover, we observed a drastic increase in oxidative stress, as well as inflammatory and apoptotic markers, with a remarkable decline in the levels of Bcl-2. To the best of our knowledge, this study is the first to report the cardiotoxic effect of VTX. Further experiments and future studies are strongly needed to comprehensively understand the cardiotoxic effect of VTX.

Quantification of Venetoclax for Therapeutic Drug Monitoring in Chinese Acute Myeloid Leukemia Patients by a Validated UPLC-MS/MS Method

Venetoclax has emerged as a breakthrough for treatment of leukemia with a wide interindividual variability in pharmacokinetics. Herein, a rapid, sensitive, and reliable UPLC-MS/MS method for quantification of venetoclax in plasma was developed and validated. The method was operated in the multiple-reaction monitoring (MRM) mode to detect venetoclax at m/z transition 868.5 > 321.0 and IS at 875.5 > 321.0, respectively. Protein precipitation prior to injection into the LC-MS/MS and the analyte was separated on an ACQUITY UPLC BEH C18 column by gradient elution with acetonitrile and 0.1% formic acid in water. Linear calibration curves were obtained in the range of 25−8000 ng/mL. The specificity, recovery, matrix effect, and stability also met the acceptance criteria of FDA guidance. The method was successfully applied to analyze plasma in acute myeloid leukemia (AML) patients. The peak plasma concentration (Cmax) of venetoclax in Chinese AML patient was 2966.0 ± 1595.0 ng/mL while the trough concentration (Cmin) was 1018.0 ± 729.4 ng/mL. Additionally, Cmax and Cmin showed a positive correlation with AST levels. Furthermore, Cmax was significantly higher in the older patients. The present method can be applied for TDM of venetoclax in treatment of hematological cancers.

Aberrantly expressed Wnt5a in nurse-like cells drives resistance to Venetoclax in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of neoplastic B lymphocytes with high levels of Wnt5a in the plasma. Currently, the cell source of Wnt5a remains controversial. The receptor of Wnt5a is ROR1, whose expression is associated with disease progression and resistance to venetoclax, a BCL-2 inhibitor approved for the treatment of CLL. In this study, we found that the levels of Wnt5a in the plasma of CLL patients were positively correlated with absolute monocyte counts, but not lymphocyte counts. We cultured monocyte-derived nurse-like cells (NLCs) from patients with CLL, and detected Wnt5a expressed in NLCs. Flow cytometry and transwell assays showed that the antibody neutralizing Wnt5a inhibited the enhanced survival and migration in CLL cells co-cultured with NLCs. Furthermore, we performed a drug screening with CLL cells cultured with or without NLCs with a library containing 133 FDA-approved oncology drugs by using high-throughput flow cytometry. We observed a significant resistance to venetoclax in CLL cells co-cultured with NLCs. Immunoblot revealed the activation of NF-κB with enhanced expression of MCL-1 and BCL-XL in CLL cells co-cultured with NLCs. Neutralizing Wnt5a or blocking NF-κB pathway significantly decreased the expression of MCL-1 and BCL-XL, which leads to enhanced sensitivity to venetoclax in CLL cells co-cultured with NLCs. In conclusion, our data showed that NLCs could be one of the sources of Wnt5a detected in patients with CLL, and Wnt5a-induced NF-κB activation in the CLL microenvironment results in resistance to venetoclax in CLL cells.

FDA-Approved Drugs for Hematological Malignancies-The Last Decade Review

Simple Summary

Hematological malignancies are diseases involving the abnormal production of blood cells. The aim of the study is to collect comprehensive information on new drugs used in the treatment of blood cancers which have introduced into therapy in the last decade. The approved drugs were analyzed for their structures and their biological activity mechanisms.

Abstract

Hematological malignancies, also referred to as blood cancers, are a group of diseases involving abnormal cell growth and persisting in the blood, lymph nodes, or bone marrow. The development of new targeted therapies including small molecule inhibitors, monoclonal antibodies, bispecific T cell engagers, antibody-drug conjugates, recombinant immunotoxins, and, finally, Chimeric Antigen Receptor T (CAR-T) cells has improved the clinical outcomes for blood cancers. In this review, we summarized 52 drugs that were divided into small molecule and macromolecule agents, approved by the Food and Drug Administration (FDA) in the period between 2011 and 2021 for the treatment of hematological malignancies. Forty of them have also been approved by the European Medicines Agency (EMA). We analyzed the FDA-approved drugs by investigating both their structures and mechanisms of action. It should be emphasized that the number of targeted drugs was significantly higher (46 drugs) than chemotherapy agents (6 drugs). We highlight recent advances in the design of drugs that are used to treat hematological malignancies, which make them more effective and less toxic.

Killing by Degradation: Regulation of Apoptosis by the Ubiquitin-Proteasome-System

Apoptosis is a cell suicide process that is essential for development, tissue homeostasis and human health. Impaired apoptosis is associated with a variety of human diseases, including neurodegenerative disorders, autoimmunity and cancer. As the levels of pro- and anti-apoptotic proteins can determine the life or death of cells, tight regulation of these proteins is critical. The ubiquitin proteasome system (UPS) is essential for maintaining protein turnover, which can either trigger or inhibit apoptosis. In this review, we will describe the E3 ligases that regulate the levels of pro- and anti-apoptotic proteins and assisting proteins that regulate the levels of these E3 ligases. We will provide examples of apoptotic cell death modulations using the UPS, determined by positive and negative feedback loop reactions. Specifically, we will review how the stability of p53, Bcl-2 family members and IAPs (Inhibitor of Apoptosis proteins) are regulated upon initiation of apoptosis. As increased levels of oncogenes and decreased levels of tumor suppressor proteins can promote tumorigenesis, targeting these pathways offers opportunities to develop novel anti-cancer therapies, which act by recruiting the UPS for the effective and selective killing of cancer cells.

Myelodysplastic Syndromes and Modalities of Treatment: An Updated Literature Review

Myelodysplastic syndromes (MDS) represent a large group of rare and diverse clonal stem cell disorders. These are classified into several different phenotypes and typically arise following a multistep genetic process, whereby genetic mutations alter the DNA damage and cellular stress responses, impacting transcription, RNA splicing, epigenetics, and cytokine signaling. However, despite the advances made regarding molecular pathophysiology and prognostic criteria and the influx of new treatment modalities, management is primarily based on prognostic scores, such as the Revised International Prognostic Scoring System. This poses a significant challenge to current healthcare professionals due to poor comprehension of the underlying pathophysiology. Hence, this review integrates the latest research and treatment modalities for MDS and discusses the different genetic mutations outlined in the revised World Health Organization 2016 MDS classification system and the associated treatment modalities. Additionally, future directions of research and clinical management of MDS are discussed.

Resistance to Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia-From Molecular Mechanisms to Clinical Relevance

Simple Summary

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasia associated with a molecular alteration, the fusion gene BCR-ABL1, that encodes the tyrosine kinase oncoprotein BCR-ABL1. This led to the development of tyrosine kinase inhibitors (TKI), with Imatinib being the first TKI approved. Although the vast majority of CML patients respond to Imatinib, resistance to this targeted therapy contributes to therapeutic failure and relapse. Here we review the molecular mechanisms and other factors (e.g., patient adherence) involved in TKI resistance, the methodologies to access these mechanisms, and the possible therapeutic approaches to circumvent TKI resistance in CML.

Abstract

Resistance to targeted therapies is a complex and multifactorial process that culminates in the selection of a cancer clone with the ability to evade treatment. Chronic myeloid leukemia (CML) was the first malignancy recognized to be associated with a genetic alteration, the t(9;22)(q34;q11). This translocation originates the BCR-ABL1 fusion gene, encoding the cytoplasmic chimeric BCR-ABL1 protein that displays an abnormally high tyrosine kinase activity. Although the vast majority of patients with CML respond to Imatinib, a tyrosine kinase inhibitor (TKI), resistance might occur either de novo or during treatment. In CML, the TKI resistance mechanisms are usually subdivided into BCR-ABL1-dependent and independent mechanisms. Furthermore, patients’ compliance/adherence to therapy is critical to CML management. Techniques with enhanced sensitivity like NGS and dPCR, the use of artificial intelligence (AI) techniques, and the development of mathematical modeling and computational prediction methods could reveal the underlying mechanisms of drug resistance and facilitate the design of more effective treatment strategies for improving drug efficacy in CML patients. Here we review the molecular mechanisms and other factors involved in resistance to TKIs in CML and the new methodologies to access these mechanisms, and the therapeutic approaches to circumvent TKI resistance.

Genomics of Resistance to Targeted Therapies

Targeting BCR and BCL-2 signaling is a widely used therapeutic strategy for chronic lymphocytic leukemia. C481S mutation decreases the covalent binding affinity of ibrutinib to BTK, resulting in reversible rather than irreversible inhibition. In addition to BTK, mutations in PLCG2 have been demonstrated to mediate acquired ibrutinib resistance. Venetoclax, a highly selective BCL2 inhibitor, has high affinity to the BH3-binding grove of BCL2. Mutation in BCL2 (Gly101Val) decreases the affinity of BCL2 for venetoclax and confers acquired resistance in cell lines and primary patient cells. This review discusses the common mechanisms of resistance to targeted therapies in chronic lymphocytic leukemia.

Discovery of 2-(3-(3-Carbamoylpiperidin-1-yl)phenoxy)acetic Acid Derivatives as Novel Small-Molecule Inhibitors of the β-Catenin/B-Cell Lymphoma 9 Protein-Protein Interaction

The β-catenin/B-cell lymphoma 9 (BCL9) protein-protein interaction (PPI) is a potential target for the suppression of hyperactive Wnt/β-catenin signaling that is vigorously involved in cancer initiation and development. Herein, we describe the medicinal chemistry optimization of a screening hit to yield novel small-molecule inhibitors of the β-catenin/BCL9 interaction. The best compound 30 can disrupt the β-catenin/BCL9 interaction with a K_i of 3.6 μM in AlphaScreen competitive inhibition assays. Cell-based experiments revealed that 30 selectively disrupted the β-catenin/BCL9 PPI, while leaving the β-catenin/E-cadherin PPI unaffected, dose-dependently suppressed Wnt signaling transactivation, downregulated oncogenic Wnt target gene expression, and on-target selectively inhibited the growth of cancer cells harboring aberrant Wnt signaling. This compound with a new chemotype can serve as a lead compound for further optimization of inhibitors for β-catenin/BCL9 PPI.

Targeted Therapies for Multiple Myeloma

Multiple myeloma continues to be a challenging disorder to treat despite improved therapies and the widespread use of proteasome inhibitors and immunomodulatory drugs. Although patient outcomes have improved, the disease continues to invariably relapse, and in the majority of cases, a cure remains elusive. In the last decade, there has been an explosion of novel drugs targeting cellular proteins essential for malignant plasma cell proliferation and survival. In this review, we focus on novel druggable targets leading to the development of monoclonal antibodies and cellular therapies against surface antigens (CD38, CD47, CD138, BCMA, SLAMF7, GPRC5D, FcRH5), inhibitors of epigenetic regulators such as histone deacetylase (HDAC), and agents targeting anti-apoptotic (BCL-2), ribosomal (eEF1A2) and nuclear export (XPO1) proteins.

Exovesicular-Shh confers Imatinib resistance by upregulating Bcl2 expression in chronic myeloid leukemia with variant chromosomes

Chronic myeloid leukemia (CML) patients with complex chromosomal translocations as well as non-compliant CML patients often demonstrate short-lived responses and poor outcomes on the current therapeutic regimes using Imatinib and its variants. It has been derived so far that leukemic stem cells (LSCs) are responsible for Imatinib resistance and CML progression. Sonic hedgehog (Shh) signaling has been implicated in proliferation of this Imatinib-resistant CD34(+) LSCs. Our work here identifies the molecular mechanism of Shh-mediated mutation-independent Imatinib resistance that is most relevant for treating CML-variants and non-compliant patients. Our results elucidate that while Shh can impart stemness, it also upregulates expression of anti-apoptotic protein—Bcl2. It is the upregulation of Bcl2 that is involved in conferring Imatinib resistance to the CD34(+) LSCs. Sub-toxic doses of Bcl2 inhibitor or Shh inhibitor (<<IC50), when used as adjuvants along with Imatinib, can re-sensitize Shh signaling cells to Imatinib. Our work here highlights the need to molecularly stratify CML patients and implement combinatorial therapy to overcome the current limitations and improve outcomes in CML.

Venetoclax in combination with chidamide and dexamethasone in relapsed/refractory primary plasma cell leukemia without t(11;14): A case report

BACKGROUND

Conventional therapies for primary plasma cell leukemia (pPCL) are usually ineffective, with a short remission time with the use of multiple myeloma medications, showing aggressiveness of pPCL. B-cell lymphoma-2 inhibitor venetoclax is usually used for relapsed/refractory multiple myeloma (RRMM) with t(11;14). There are very few studies published on the use of venetoclax in pPCL without t(11;14). Similarly, histone deacetylase inhibitors are considered effective for the treatment of RRMM, but there are no reports on their use in pPCL.

CASE SUMMARY

A 57-year-old woman with severe anemia, thrombocytopenia, multiple bone destruction, impaired renal function, and 42.7% of peripheral plasma cells is reported. After multiple chemotherapy regimens and chimeric antigen receptor T-cell treatment, the disease progressed again. The patient had very good partial response and was maintained for a long time on venetoclax in combination with chidamide and dexamethasone therapy.

CONCLUSION

The success of venetoclax-chidamide-dexamethasone combination therapy in achieving a very good partial response suggested that it can be used for refractory/relapsed pPCL patients who have been exhausted with the use of various drug combinations and had poor survival outcomes.

Combination strategies to overcome resistance to the BCL2 inhibitor venetoclax in hematologic malignancies

Venetoclax has been approved by the United States Food and Drug Administration since 2016 as a monotherapy for treating patients with relapsed/refractory chronic lymphocytic leukemia having 17p deletion. It has led to a breakthrough in the treatment of hematologic malignancies in recent years. However, unfortunately, resistance to venetoclax is inevitable. Multiple studies confirmed that the upregulation of the anti-apoptotic proteins of the B-cell lymphoma 2 (BCL2) family mediated by various mechanisms, such as tumor microenvironment, and the activation of intracellular signaling pathways were the major factors leading to resistance to venetoclax. Therefore, only targeting BCL2 often fails to achieve the expected therapeutic effect. Based on the mechanism of resistance in specific hematologic malignancies, the combination of specific drugs with venetoclax was a clinically optional treatment strategy for overcoming resistance to venetoclax. This study aimed to summarize the possible resistance mechanisms of various hematologic tumors to venetoclax and the corresponding clinical strategies to overcome resistance to venetoclax in hematologic malignancies.

The safety of available chemo-free treatments for mantle cell lymphoma

INTRODUCTION

Conventional treatment for mantle cell lymphoma (MCL) patients includes regimens combining rituximab with other cytotoxic drugs, followed or not by consolidation with autologous stem cell transplantation and rituximab maintenance. However, older, unfit, and relapsed/refractory patients are often ineligible for intense treatment. Currently, available new targeted treatment options seem to offer hope in this group of patients.

AREAS COVERED

This article reviews the safety profiles of new therapeutic chemotherapy-free options for MCL patients. Publications in English from 2010 through June 2020 were surveyed on the MEDLINE database for articles. Proceedings of the American Society of Hematology during the last 5 years were also included.

EXPERT OPINION

MCL is a clinically heterogenous disease predominantly affecting elderly patients. Its variable clinical course requires personalization and individualization of treatment to achieve optimal survival and acceptable safety profiles, especially in poor prognosis patients. Results of clinical trials performed in the past decade indicated that novel drugs used as a single agent or as part of a conventional chemotherapeutic treatment offer promise in minimalizing the relapse rate for MCL and may allow more effective and safer treatment options by reducing the risk of adverse events, especially cytopenias and infections.

Options for Chemotherapy and Scoring Response and Relapse

Chemotherapy for amyloid light chain (AL) amyloidosis has evolved over the years. Although high-dose melphalan and stem cell transplantation remain the standard of care for eligible patients, a vast majority of the patients at the time of presentation are not eligible for this approach and require low-intensity but highly effective induction therapy, usually based on bortezomib. Immunomodulatory agents are not well tolerated, particularly by patients with AL amyloidosis cardiomyopathy, and are reserved for second-line or later therapy. Because there currently is no Food Drug and Administration-approved therapy, participation in well-designed clinical trials of high scientific merit should be considered.

A small-molecule ARTS mimetic promotes apoptosis through degradation of both XIAP and Bcl-2

Many human cancers over-express B cell lymphoma 2 (Bcl-2) or X-linked inhibitor of apoptosis (IAP) proteins to evade cell death. The pro-apoptotic ARTS (Sept4_i2) protein binds directly to both Bcl-2 and XIAP and promotes apoptosis by stimulating their degradation via the ubiquitin-proteasome system (UPS). Here we describe a small molecule, A4, that mimics the function of ARTS. Microscale thermophoresis assays showed that A4 binds XIAP, but not cellular inhibitor of apoptosis protein 1 (cIAP1). A4 binds to a distinct ARTS binding pocket in the XIAP-BIR3 (baculoviral IAP repeat 3) domain. Like ARTS, A4 stimulated poly-ubiquitylation and UPS-mediated degradation of XIAP and Bcl-2, but not cIAP1, resulting in caspase-9 and -3 activation and apoptosis. In addition, over-expression of XIAP rescued HeLa cells from A4-induced apoptosis, consistent with the idea that A4 kills by antagonizing XIAP. On the other hand, treatment with the SMAC-mimetic Birinapant induced secretion of tumour necrosis factor-α (TNFα) and killed ~50% of SKOV-3 cells, and addition of A4 to Birinapant-treated cells significantly reduced secretion of TNFα and blocked Birinapant-induced apoptosis. This suggests that A4 acts by specifically targeting XIAP. The effect of A4 was selective as peripheral blood mononuclear cells and normal human breast epithelial cells were unaffected. Furthermore, proteome analysis revealed that cancer cell lines with high levels of XIAP were particularly sensitive to the killing effect of A4. These results provide proof of concept that the ARTS binding site in XIAP is "druggable". A4 represents a novel class of dual-targeting compounds stimulating apoptosis by UPS-mediated degradation of important anti-apoptotic oncogenes.

Blocking interaction between SHP2 and PD-1 denotes a novel opportunity for developing PD-1 inhibitors

Small molecular PD-1 inhibitors are lacking in current immuno-oncology clinic. PD-1/PD-L1 antibody inhibitors currently approved for clinical usage block interaction between PD-L1 and PD-1 to enhance cytotoxicity of CD8⁺ cytotoxic T lymphocyte (CTL). Whether other steps along the PD-1 signaling pathway can be targeted remains to be determined. Here, we report that methylene blue (MB), an FDA-approved chemical for treating methemoglobinemia, potently inhibits PD-1 signaling. MB enhances the cytotoxicity, activation, cell proliferation, and cytokine-secreting activity of CTL inhibited by PD-1. Mechanistically, MB blocks interaction between Y248-phosphorylated immunoreceptor tyrosine-based switch motif (ITSM) of human PD-1 and SHP2. MB enables activated CTL to shrink PD-L1 expressing tumor allografts and autochthonous lung cancers in a transgenic mouse model. MB also effectively counteracts the PD-1 signaling on human T cells isolated from peripheral blood of healthy donors. Thus, we identify an FDA-approved chemical capable of potently inhibiting the function of PD-1. Equally important, our work sheds light on a novel strategy to develop inhibitors targeting PD-1 signaling axis.

Discovery of PROTAC BCL-XL degraders as potent anticancer agents with low on-target platelet toxicity

Anti-apoptotic protein BCL-X_L plays a key role in tumorigenesis and cancer chemotherapy resistance, rendering it an attractive target for cancer treatment. However, BCL-X_L inhibitors such as ABT-263 cannot be safely used in the clinic because platelets solely depend on BCL-X_L to maintain their viability. To reduce the on-target platelet toxicity associated with the inhibition of BCL-X_L, we designed and synthesized PROTAC BCL-X_L degraders that recruit CRBN or VHL E3 ligase because both of these enzymes are poorly expressed in human platelets compared to various cancer cell lines. We confirmed that platelet-toxic BCL-X_L/2 dual inhibitor ABT-263 can be converted into platelet-sparing CRBN/VHL-based BCL-X_L specific degraders. A number of BCL-X_L degraders are more potent in killing cancer cells than their parent compound ABT-263. Specifically, XZ739, a CRBN-dependent BCL-X_L degrader, is 20-fold more potent than ABT-263 against MOLT-4 T-ALL cells and has >100-fold selectivity for MOLT-4 cells over human platelets. Our findings further demonstrated the utility of PROTAC technology to achieve tissue selectivity through recruiting differentially expressed E3 ligases.

Comparison of putative BH3 mimetics AT-101, HA14-1, sabutoclax and TW-37 with ABT-737 in platelets

Platelet lifespan is regulated by intrinsic apoptosis. Platelet apoptosis can be triggered by BH3 mimetics that inhibit the pro-survival Bcl-2 family protein, Bcl-xL. Here, we investigated several small molecules that are reported to act as BH3 mimetics and compared their effects to the well-established BH3 mimetic, ABT-737. Platelet phosphatidylserine (PS) exposure was determined by flow cytometry. Changes in cytosolic Ca²⁺ signaling were detected using Cal-520. Plasma membrane integrity was determined by calcein leakage. The roles of caspases and calpain in these processes were determined using Q-VD-OPh and calpeptin, respectively. As previously reported, ABT-737 triggered PS exposure in a caspase-dependent manner and calcein loss in a caspase and calpain-dependent manner. In contrast, AT-101 and sabutoclax triggered PS exposure independently of caspases. HA14-1 also triggered PS exposure in a caspase-independent but calpain-dependent manner. There were also significant differences in the pattern and protease-dependency of cytosolic Ca²⁺ signaling in response to these drugs compared to ABT-737. Since there are clear differences between the action of ABT-737 and the other putative BH3 mimetics investigated here, AT-101, HA14-1 and sabutoclax cannot be considered as acting as BH3 mimetics in platelets. Furthermore, the platelet death caused by these drugs is likely to be distinct from apoptosis.

Real-world data on safety and efficacy of venetoclax-based regimens in relapsed/refractory t(11;14) multiple myeloma

The treatment for relapsed/refractory multiple myeloma (RRMM) continues to be challenging despite recent therapeutic advancements. Venetoclax, an inhibitor of the anti‐apoptotic protein BCL‐2, is a promising agent, especially in patients harbouring t(11;14). Our objective was to review our experience with venetoclax‐based regimens at our institution. All ten RRMM patients treated with venetoclax were included and had a median of six prior lines of therapy. The overall response rate was 78% and one patient with cardiac amyloidosis and MM achieved a cardiac organ response. Haematologic toxicities requiring red blood cell and platelet transfusion and non‐haematologic toxicities, most commonly gastrointestinal upset, were observed.

Venetoclax combination therapy in relapsed/refractory acute myeloid leukemia: A single institution experience

Venetoclax (VEN) is a selective BCL-2 inhibitor that has been shown to be effective when used in combination with hypomethylating agents (HMAs) or low-dose cytarabine (LDAC) for treatment-naïve, elderly acute myeloid leukemia (AML) patients unfit for intensive chemotherapy. Data on its use in the relapsed/refractory setting are limited. A retrospective analysis was performed among 14 patients with relapsed or refractory AML treated with VEN combination therapy at the University of California Los Angeles from 2018-2019. Eight patients received VEN in combination with azacitidine, 5 patients with decitabine, and 1 patient with LDAC. The majority (10 patients, 71.4%) had adverse cytogenetics. Three patients (21.4%) had undergone an allogeneic stem cell transplant prior to VEN therapy, and 5 patients (35.7%) had leukemia that failed HMA therapy prior. The objective response rate (ORR) was 35.7% (3 patients achieved complete remission with incomplete hematologic recovery and 2 patients achieved partial remission). Three patients (21.4%) were successfully transitioned to either allogeneic bone marrow transplant (2 patients) or donor lymphocyte infusion (1 patient). Seven patients (50.0%) developed a grade 3 or greater infection following VEN therapy, and 3 patients (21.4%) developed a grade 3 or greater intracranial hemorrhage. Three patients experienced early death within 30 days of therapy (2 from infection, 1 from bleeding). The median overall survival (OS) was 4.7 months, and the 1-year OS rate was 23.6% (95% CI 4.4-51.2) for the entire patient cohort. Overall, the response rate was not inferior to that with conventional salvage chemotherapy, but there were notable complications as a result of prolonged cytopenias.

How I treat newly diagnosed acute myeloid leukemia in an outpatient setting: a multidisciplinary team perspective

Historically, patients with acute myeloid leukemia received intensive chemotherapy requiring hospitalization, which can diminish quality of life and increase healthcare costs. The introduction of new therapies facilitated a shift toward outpatient therapy, which requires coordination of a multidisciplinary team, thorough patient evaluation, careful preparation and rigorous patient monitoring. Many patients are candidates for multiple treatment approaches; we generally employ CPX-351 (Vyxeos®) as an intensive outpatient approach and venetoclax (Venclyxto/Venclexta®) plus hypomethylating agents as a lower-intensity approach, with 2-3 visits/week during treatment. Treatment infusions are scheduled in the morning to leave sufficient time for transfusions and other supportive care later the same day, to prevent additional visits. With careful planning and patient monitoring, acute myeloid leukemia treatment can be successfully administered in the outpatient setting.

Obinutuzumab and venetoclax induced complete remission in a patient with ibrutinib-resistant non-nodal leukemic mantle cell lymphoma

We herein report the case of a 73-year-old male patient who was diagnosed with leukemic non-nodal MCL. This patient had received six cycles of bendamustine, which resulted in a transient remission, and a second-line therapy with ibrutinib, which unfortunately failed to induce remission. We started a treatment with single-agent obinutuzumab at a dose of 20 mg on day 1, 50 mg on day 2-4, 330 mg on day 5, and 1000 mg on day 6. The laboratory analysis showed a rapid decrease of leukocyte count. Four weeks later, we repeated the treatment with obinutuzumab at a dose of 1000 mg q4w and started a therapy with venetoclax at a dose of 400 mg qd, which could be increased to 800 mg qd from the third cycle. This combination therapy was well tolerated. The patient achieved a complete remission (CR) after three cycles of obinutuzumab and venetoclax. To date, the patient has a progression-free survival of 17 months under ongoing obinutuzumab maintenance q4w. This is the first report about obinutuzumab and venetoclax induced CR in rituximab-intolerant patient with an ibrutinib-resistant MCL. This case suggests that obinutuzumab- and venetoclax-based combination therapy might be salvage therapy in patients with ibrutinib-resistant MCL.

PROTACs are effective in addressing the platelet toxicity associated with BCL-XL inhibitors

BCL-X_L is an anti-apoptotic protein that plays an important role in tumorigenesis, metastasis, and intrinsic or therapy-induced cancer drug resistance. More recently, BCL-X_L has also been identified as a key survival factor in senescent cells. Accumulation of senescent cells has been indicated as a causal factor of aging and many age-related diseases and contributes to tumor relapse and metastasis. Thus, inhibition of BCL-X_L is an attractive strategy for the treatment of cancer and extension of healthspan. However, development of BCL-X_L inhibitors such as navitoclax for clinical use has been challenging because human platelets depend on BCL-X_L for survival. In this review, the authors discuss how BCL-X_L-targeted proteolysis targeting chimeras (PROTACs) afford a novel approach to mitigate the on-target thrombocytopenia associated with BCL-X_L inhibition. The authors summarize the progress in the development of BCL-X_L PROTACs. The authors highlight the in vitro and in vivo data supporting that by hijacking the ubiquitin protein ligase (E3) that are poorly expressed in human platelets, BCL-X_L PROTACs can significantly improve the therapeutic window compared to conventional BCL-X_L inhibitors. These findings demonstrated the potentially broad utility of PROTAC technology to achieve tissue selectivity through recruiting differentially expressed E3 ligases and to reduce on-target toxicity.

Gly101Val BCL2 Mutation: One Step Closer to Understanding Venetoclax Resistance in CLL

In this issue, Blombery and colleagues show that the chronic lymphocytic leukemia (CLL) cells bearing Gly101Val mutation confer resistance to venetoclax by reducing the affinity of BCL2 for venetoclax by 180-fold in cell lines and in patient cells. Detection of this mutation provides a potential biomarker for impending disease progression and an opportunity for targeted and combinational therapy to treat CLL.See related article by Blombery et al., p. 342.

Multiple myeloma: an overview of management

Multiple myeloma represents 2% of all new cancer diagnoses in the United Kingdom and accounts for 2% of all cancer deaths. In the past few decades, there have been huge improvements in life expectancy which have been driven by novel therapeutic agents, autologous stem cell transplants and intensified supportive care. This review will discuss the pathogenesis of multiple myeloma, current management approaches and the direction of future treatments. In addition, this review will highlight the high burden of symptoms that patients experience and therefore the great benefits that can be gained from specialist palliative care input.

New advances in targeting aberrant signaling pathways in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disorder characterized by malignant transformation of immature progenitors primed towards T-cell development. Over the past 15 years, advances in the molecular characterization of T-ALL have uncovered oncogenic key drivers and crucial signaling pathways of this disease, opening new chances for the development of novel therapeutic strategies. Currently, T-ALL patients are still treated with aggressive therapies, consisting of high dose multiagent chemotherapy. To minimize and overcome the unfavorable effects of these regimens, it is critical to identify innovative targets and test selective inhibitors of such targets. Major efforts are being made to develop small molecules against deregulated signaling pathways, which sustain T-ALL cell growth, survival, metabolism, and drug-resistance. This review will focus on recent improvements in the understanding of the signaling pathways involved in the pathogenesis of T-ALL and on the challenging opportunities for T-ALL targeted therapies.

ABT-737 Triggers Caspase-Dependent Inhibition of Platelet Procoagulant Extracellular Vesicle Release during Apoptosis and Secondary Necrosis In Vitro

Platelet lifespan is limited by activation of intrinsic apoptosis. Apoptotic platelets are rapidly cleared from the circulation in vivo. ABT-737 triggers platelet apoptosis and is a useful tool for studying this process. However, in vitro experiments lack clearance mechanisms for apoptotic platelets. To determine whether apoptotic platelets progress to secondary necrosis, apoptosis was triggered in human platelets with ABT-737, a BH3 mimetic. Platelet annexin V (AnV) binding, release of AnV⁺ extracellular vesicles (EVs), and loss of plasma membrane integrity were monitored by flow cytometry. ABT-737 triggered AnV binding, indicating phosphatidylserine exposure, release of AnV⁺ EVs, and a slow loss of plasma membrane integrity. The latter suggests that apoptotic platelets progress to secondary necrosis in vitro. These responses were dependent on caspase activation and Ca²⁺ entry. Surprisingly, although intracellular Ca²⁺ concentration increased, AnV⁺ EV release was not dependent on the Ca²⁺-dependent protease, calpain. On the contrary, ABT-737 downregulated the ability of the Ca²⁺ ionophore, A23187, to trigger calpain-dependent release of AnV⁺ EVs. This was dependent on caspase activity as, when caspases were inhibited, ABT-737 increased the ability of A23187 to trigger AnV⁺ EV release. These data suggest that apoptotic platelets progress to secondary necrosis unless they are cleared. This may affect the interpretation of ABT-737-triggered signaling in platelets in vitro. Ca²⁺-dependent AnV⁺ EV release is downregulated during apoptosis in a caspase-dependent manner, which may limit the potential consequences of secondary necrotic platelets.

A literature review of the patent publications on venetoclax - a selective Bcl-2 inhibitor: discovering the therapeutic potential of a novel chemotherapeutic agent

INTRODUCTION

Studies presented in patents show that a novel chemotherapeutic agent, venetoclax, might be useful in additional therapeutic indications. Venetoclax is approved in America for the treatment of patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). Venetoclax selectively inhibits the B-cell lymphoma-2 (Bcl-2) protein, an anti-apoptotic protein that can be overexpressed in most B-cell lymphoid malignancies.

AREAS COVERED

This is a review of all the patents granted until November 2018, with venetoclax in the examples or claim section of the patent document. The patents include the synthesis, polymorphism, formulations, in vitro and in vivo efficacy as well as the therapeutic application of venetoclax.

EXPERT OPINION

The approved indications for treatment with venetoclax are limited but expanding rapidly. Studies suggest that venetoclax might be useful in several other therapeutic indications, mostly other hematological malignancies. Numerous studies use venetoclax in combinations with other therapeutic agents. Such combinational treatment shows promising results in additional indications as well as drug-resistant cancers. Venetoclax is an interesting new therapeutic involved in a variety of clinical research. Patent applications in recent years even include venetoclax in somewhat exotic fields such as type 1 diabetes, asthma, and Zika virus treatment.