Targeting BCL-2 and ABL/LYN in Philadelphia chromosome-positive acute lymphoblastic leukemia

A review of immunotargeted therapy for Philadelphia chromosome positive acute lymphoblastic leukaemia: making progress in chemotherapy-free regimens

Philadelphia chromosome-positive acute lymphoblastic leukemia (PH + ALL) is the most common cytogenetic abnormality of B-ALL in adults and is associated with poor prognosis. Previously, the only curative treatment option in PH + ALL was allogeneic hematopoietic stem cell transplantation (Allo-HSCT). Since 2000, targeted therapy combined with chemotherapy, represented by the tyrosine kinase inhibitor Imatinib, has become the first-line treatment for PH + ALL. Currently, the remission rate and survival rate of Imatinib are superior to those of simple chemotherapy, and it can also improve the efficacy of transplantation. More recently, some innovative immune-targeted therapy greatly improved the prognosis of PH + ALL, such as Blinatumomab and Inotuzumab Ozogamicin. For patients with ABL1 mutations and those who have relapsed or are refractory to other treatments, targeted oral small molecule drugs, monoclonal antibodies, Bispecific T cell Engagers (BiTE), and chimeric antigen receptor (CAR) T cells immunotherapy are emerging as potential treatment options. These new therapeutic interventions are changing the treatment landscape for PH + ALL. In summary, this review discusses the current advancements in targeted therapeutic agents shift in the treatment strategy of PH + ALL towards using more tolerable chemotherapy-free induction and consolidation regimens confers better disease outcomes and might obviate the need for HSCT.

A novel lncRNA associated with the prognosis of patients with colorectal cancer resists apoptosis through the LYN/BCL-2 pathway

PURPOSE

We found a novel lncRNA named lncAC138150.2 related to the overall survival and staging of patients with colorectal cancer (CRC) by bioinformatic analysis using data from the Cancer Genome Atlas (TCGA), and the study aimed to elucidate the function of lncAC138150.2 and underlying mechanisms.

METHODS

Target molecules were knocked down by transfection with antisense oligonucleotides (ASOs), siRNAs, or lentiviruses and overexpressed by transfection with plasmids. The function of lncAC138150.2 was determined using histological, cytological, and molecular biology methods. The underlying mechanism of lncAC138150.2 function was investigated using RNA-seq, bioinformatics analysis, and molecular biology methods.

RESULTS

The expression of lncAC138150.2 was increased in colorectal tissues compared with paired normal tissues. The lncAC138150.2 knockdown increased apoptosis but did not change the cell proliferation, cell cycle distribution, or cell migration ability of CRC cells, while lncAC138150.2 overexpression decreased CRC apoptosis. lncAC138150.2 was mainly located in the cell nucleus, and each lncAC138150.2 transcript knockdown increased CRC apoptosis. BCL-2 pathway was significantly altered in apoptosis induced by lncAC138150.2 knockdown, which was alleviated by BAX knockdown. The expression of LYN was significantly decreased with lncAC138150.2 knockdown, LYN knockdown increased CRC apoptosis, and its overexpression completely alleviated CRC apoptosis induced by lncAC138150.2 knockdown.

CONCLUSION

lncAC138150.2 significantly inhibited CRC apoptosis and affected the prognosis of patients with CRC, through the LYN/BCL-2 pathway.

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.

Novel therapies for pediatric acute lymphoblastic leukemia

PURPOSE OF REVIEW

This review summarizes the current novel therapy landscape in pediatric acute lymphoblastic leukemia (ALL), with a focus on key clinical trials which will shape the future direction of care for these children.

RECENT FINDINGS

Recent landmark immunotherapy trials in B-ALL have demonstrated significant benefit for children, adolescents, and young adults with relapsed/refractory high-risk leukemia. Due to these successes, current trials are asking the question as to whether immunotherapy can be successfully incorporated upfront. Additionally, therapies targeting novel antigens or molecular pathways are being developed, providing new options for children previously thought to have incurable leukemia.

SUMMARY

As survival for ALL has relatively plateaued with maximizing intensity through conventional chemotherapy, continued preclinical and clinical study of novel immunotherapeutic and targeted agents is crucial to further improve outcomes in childhood leukemia.

High-throughput screening as a drug repurposing strategy for poor outcome subgroups of pediatric B-cell precursor Acute Lymphoblastic Leukemia

Although a great cure rate has been achieved for pediatric BCP-ALL, approximately 15% of patients do not respond to conventional chemotherapy and experience disease relapse. A major effort to improve the cure rates by treatment intensification would result in an undesirable increase in treatment-related toxicity and mortality, raising the need to identify novel therapeutic approaches. High-throughput (HTP) drug screening enables the profiling of patients' responses in vitro and allows the repurposing of compounds currently used for other diseases, which can be immediately available for clinical application. The aim of this study was to apply HTP drug screening to identify potentially effective compounds for the treatment of pediatric BCP-ALL patients with poor prognosis, such as patients with Down Syndrome (DS) or carrying rearrangements involving PAX5 or KMT2A/MLL genes. Patient-derived Xenografts (PDX) samples from 34 BCP-ALL patients (9 DS CRLF2r, 15 PAX5r, 10 MLLr), 7 human BCP-ALL cell lines and 14 hematopoietic healthy donor samples were screened on a semi-automated HTP drug screening platform using a 174 compound library (FDA/EMA-approved or in preclinical studies). We identified 9 compounds active against BCP-ALL (ABT-199/venetoclax, AUY922/luminespib, dexamethasone, EC144, JQ1, NVP-HSP990, paclitaxel, PF-04929113 and vincristine), but sparing normal cells. Ex vivo validations confirmed that the BCL2 inhibitor venetoclax exerts an anti-leukemic effect against all three ALL subgroups at nanomolar concentrations. Overall, this study points out the benefit of HTP screening application for drug repurposing to allow the identification of effective and clinically translatable therapeutic agents for difficult-to-treat childhood BCP-ALL subgroups.

Concomitant Venetoclax and Imatinib for Comanaging Chronic Lymphocytic Leukemia and Chronic Myeloid Leukemia: A Case Report

Patients with synchronous malignancies can be problematic to diagnose and manage because workup and therapeutic targeting for each individual malignancy must be coordinated carefully. This report presents a patient with concurrent chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL) managed with concomitant venetoclax and imatinib. Because imatinib is a moderate cytochrome P450 3A4 inhibitor, close monitoring is required when using with a substrate of 3A4 such as venetoclax. Although the target dose of venetoclax is 400 mg, it was capped at 100 mg due to the interaction. Despite the interaction and possible enhancement of toxicities, the patient has tolerated therapy well, and both diseases have responded to this novel approach. In addition, because aberrant BCL-2 activity has been implicated in CML, the use of venetoclax may contribute to success in the management of this patient's CML. This case report represents the safe concomitant use of venetoclax and imatinib in a patient with synchronous CML and CLL.

Flumatinib plus venetoclax as an effective therapy for Philadelphia chromosome-positive acute myeloid leukemia: A case report

Philadelphia chromosome-positive acute myeloid leukemia (Ph + AML) is a rare type of AML with a low survival rate and poor prognosis. We first report a Ph + AML patient who remained in long-term remission after the combination of flumatinib and venetoclax, which could provide corresponding treatment ideas for clinical practice.

Modern Management Options for Ph+ ALL

Simple Summary

The use of tyrosine kinase inhibitors has represented a major step forward in the therapy of Philadelphia chromosome positive acute lymphoblastic leukemia. Recent improvements in the therapy are focused on early use of third generation tyrosine kinase inhibitors, their combination with immunotherapy, the refined indication of allogeneic hematopoietic stem cell transplantation, the optimal use and duration of maintenance therapy, and the management of patients with molecular or hematological relapse with combination of targeted therapies and immunotherapy, including cellular therapies. Improvements in the assessment of measurable residual disease and in the detection of mutations in the ABL1 domain are contributing to the better selection of the therapy for newly diagnosed as well as for relapsed or refractory patients.

Abstract

Impressive advances have been achieved in the management of patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) since the initial concurrent use of imatinib and standard chemotherapy. The attenuation of chemotherapy has proven to be equally effective and less toxic, the use of third generation TKI upfront has improved the frequency of complete molecular response and the survival rate, and the combination of tyrosine kinase inhibitors with immunotherapy has further increased the rate of molecular response to 70–80% after consolidation, which has been translated into a survival rate of 75–90% in recent trials. As a result of these improvements, the role of allogeneic hematopoietic stem cell transplantation is being redefined. The methodology of measurable residual disease assessment and the detection of ABL1 mutations are also improving and will contribute to a more precise selection of the treatment for newly diagnosed and relapsed or refractory (R/R) patients. Finally, new compounds combined with immunotherapeutic approaches, including cellular therapy, are being used as rescue therapy and will hopefully be included in first line therapy in the near future. This article will review and update the modern management of patients with Ph+ ALL.

The Emerging Role of Venetoclax-Based Treatments in Acute Lymphoblastic Leukemia

Venetoclax, a B-cell lymphoma (BCL-2) inhibitor, in combination with hypomethylating agents has become the new standard of care in elderly and unfit patients with acute myeloid leukemia, with significantly improved overall survival and quality of life. Studies of venetoclax combined with high-dose chemotherapy are emerging with evidence of higher rates of molecular remission. Recently, a growing number of publications bring forth the use of venetoclax in patients with acute lymphoblastic leukemia (ALL). In the current review, we present the biological rationale of BCL-2 inhibition in ALL, how the interplay of BH3 proteins modulate the response and the current clinical experience with various combinations.

Chemotherapy-Free Targeted Anti-BCR-ABL+ Acute Lymphoblastic Leukemia Therapy May Benefit the Heart

Targeted therapies are currently considered the best cost-benefit anti-cancer treatment. In hematological malignancies, however, relapse rates and non-hematopoietic side effects including cardiotoxicity remain high. Here, we describe significant heart damage due to advanced acute lymphoblastic leukemia (ALL) with t(9;22) encoding the bcr-abl oncogene (BCR-ABL+ ALL) in murine xenotransplantation models. Echocardiography reveals severe cardiac dysfunction with impaired left ventricular function and reduced heart and cardiomyocyte dimensions associated with increased apoptosis. This cardiac damage is fully reversible, but cardiac recovery depends on the therapy used to induce ALL remission. Chemotherapy-free combination therapy with dasatinib (DAS), venetoclax (VEN) (targeting the BCR-ABL oncoprotein and mitochondrial B-cell CLL/Lymphoma 2 (BCL2), respectively), and dexamethasone (DEX) can fully revert cardiac defects, whereas the depletion of otherwise identical ALL in a genetic model using herpes simplex virus type 1 thymidine kinase (HSV-TK) cannot. Mechanistically, dexamethasone induces a pro-apoptotic BCL2-interacting mediator of cell death (BIM) expression and apoptosis in ALL cells but enhances pro-survival B-cell lymphoma extra-large (BCLXL) expression in cardiomyocytes and clinical recovery with the reversion of cardiac atrophy. These data demonstrate that therapies designed to optimize apoptosis induction in ALL may circumvent cardiac on-target side effects and may even activate cardiac recovery. In the future, combining the careful clinical monitoring of cardiotoxicity in leukemic patients with the further characterization of organ-specific side effects and signaling pathways activated by malignancy and/or anti-tumor therapies seems reasonable.

Has Ph-like ALL Superseded Ph+ ALL as the Least Favorable Subtype?

Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is a subset of high-risk B-ALL associated with high relapse risk and inferior clinical outcomes across the pediatric-to-adult age spectrum. Ph-like ALL is characterized by frequent IKZF1 alterations and a kinase-activated gene expression profile similar to that of Philadelphia chromosome-positive (Ph+) ALL, yet lacks the canonical BCR-ABL1 rearrangement. Advances in high-throughput sequencing technologies during the past decade have unraveled the genomic landscape of Ph-like ALL, revealing a diverse array of kinase-activating translocations and mutations that may be amenable to targeted therapies that have set a remarkable precision medicine paradigm for patients with Ph + ALL. Collaborative scientific efforts to identify and characterise Ph-like ALL during the past decade has directly informed current precision medicine trials investigating the therapeutic potential of tyrosine kinase inhibitor-based therapies for children, adolescents, and adults with Ph-like ALL, although the most optimal treatment paradigm for this high-risk group of patients has yet to be established. Herein, we describe the epidemiology, clinical features, and biology of Ph-like ALL, highlight challenges in implementing pragmatic and cost-effective diagnostic algorithms in the clinic, and describe the milieu of treatment strategies under active investigation that strive to decrease relapse risk and improve long-term survival for patients with Ph-like ALL as has been successfully achieved for those with Ph + ALL.

INCB84344-201: Ponatinib and steroids in frontline therapy of unfit patients with Ph+ acute lymphoblastic leukemia

In patients with newly diagnosed Ph⁺ ALL, ponatinib and prednisone therapy resulted in long molecular remissions and few resistance mutations.

The observed high rates of discontinuation and dose modification suggest that a lower dose may be more appropriate in older/unfit patients.

Tyrosine kinase inhibitors have improved survival for patients with Philadelphia chromosome–positive (Ph⁺) acute lymphoblastic leukemia (ALL). However, prognosis for old or unfit patients remains poor. In the INCB84344-201 (formerly GIMEMA LAL 1811) prospective, multicenter, phase 2 trial, we tested the efficacy and safety of ponatinib plus prednisone in newly diagnosed patients with Ph⁺ ALL ≥60 years, or unfit for intensive chemotherapy and stem cell transplantation. Forty-four patients received oral ponatinib 45 mg/d for 48 weeks (core phase), with prednisone tapered to 60 mg/m²/d from days-14-29. Prophylactic intrathecal chemotherapy was administered monthly. Median age was 66.5 years (range, 26-85). The primary endpoint (complete hematologic response [CHR] at 24 weeks) was reached in 38/44 patients (86.4%); complete molecular response (CMR) in 18/44 patients (40.9%) at 24 weeks. 61.4% of patients completed the core phase. As of 24 April 2020, median event-free survival was 14.31 months (95% CI 9.30-22.31). Median overall survival and duration of CHR were not reached; median duration of CMR was 11.6 months. Most common treatment-emergent adverse events (TEAEs) were rash (36.4%), asthenia (22.7%), alanine transaminase increase (15.9%), erythema (15.9%), and γ-glutamyltransferase increase (15.9%). Cardiac and vascular TEAEs occurred in 29.5% (grade ≥3, 18.2%) and 27.3% (grade ≥3, 15.9%), respectively. Dose reductions, interruptions, and discontinuations due to TEAEs occurred in 43.2%, 43.2%, and 27.3% of patients, respectively; 5 patients had fatal TEAEs. Ponatinib and prednisone showed efficacy in unfit patients with Ph⁺ ALL; however, a lower ponatinib dose may be more appropriate in this population. This trial was registered at www.clinicaltrials.gov as #NCT01641107.

Targeted Therapy in the Treatment of Pediatric Acute Lymphoblastic Leukemia-Therapy and Toxicity Mechanisms

Targeted therapy has revolutionized the treatment of poor-prognosis pediatric acute lymphoblastic leukemia (ALL) with specific genetic abnormalities. It is still being described as a new landmark therapeutic approach. The main purpose of the use of molecularly targeted drugs and immunotherapy in the treatment of ALL is to improve the treatment outcomes and reduce the doses of conventional chemotherapy, while maintaining the effectiveness of the therapy. Despite promising treatment results, there is limited clinical research on the effect of target cell therapy on the potential toxic events in children and adolescents. The recent development of highly specific molecular methods has led to an improvement in the identification of numerous unique expression profiles of acute lymphoblastic leukemia. The detection of specific genetic mutations determines patients’ risk groups, which allows for patient stratification and for an adjustment of the directed and personalized target therapies that are focused on particular molecular alteration. This review summarizes the knowledge concerning the toxicity of molecular-targeted drugs and immunotherapies applied in childhood ALL.

A strategy to assess the cellular activity of E3 ligase components against neo-substrates using electrophilic probes

While there are hundreds of predicted E3 ligases, characterizing their applications for targeted protein degradation has proved challenging. Here, we report a chemical biology approach to evaluate the ability of modified recombinant E3 ligase components to support neo-substrate degradation. Bypassing the need for specific E3 ligase binders, we use maleimide-thiol chemistry for covalent functionalization followed by E3 electroporation (COFFEE) in live cells. We demonstrate that electroporated recombinant von Hippel-Lindau (VHL) protein, covalently functionalized at its ligandable cysteine with JQ1 or dasatinib, induces degradation of BRD4 or tyrosine kinases, respectively. Furthermore, by applying COFFEE to SPSB2, a Cullin-RING ligase 5 receptor, as well as to SKP1, the adaptor protein for Cullin-RING ligase 1 F box (SCF) complexes, we validate this method as a powerful approach to define the activity of previously uncharacterized ubiquitin ligase components, and provide further evidence that not only E3 ligase receptors but also adaptors can be directly hijacked for neo-substrate degradation.

dbMCS: A Database for Exploring the Mutation Markers of Anti-Cancer Drug Sensitivity

The identification of mutation markers and the selection of appropriate treatment for patients with specific genome mutations are important steps in the development of targeted therapies and the realization of precision medicine for human cancers. To investigate the baseline characteristics of drug sensitivity markers and develop computational methods of mutation effect prediction, we presented a manually curated online- based database of mutation Markers for anti-Cancer drug Sensitivity (dbMCS). Currently, dbMCS contains 1271 mutations and 4427 mutation-disease-drug associations (3151 and 1276 for sensitivity and resistance, respectively) with their PubMed indexed articles. By comparing the mutations in dbMCS with the putative neutral polymorphisms, we investigated the characteristics of drug sensitivity markers. We found that the mutation markers tend to significantly impact on high-conservative regions both in DNA sequences and protein domains. And some of them presented pleiotropic effects depending on the tumor context, appearing concurrently in the sensitivity and resistance categories. In addition, we preliminarily explored the machine learning-based methods for identifying mutation markers of anti-cancer drug sensitivity and produced optimistic results, which suggests that a reliable dataset may provide new insights and essential clues for future cancer pharmacogenomics studies. dbMCS is available at http://bioinfo.aielab.cc/dbMCS/.

CARMA1 is required for Notch1-induced NF-κB activation in SIL-TAL1-negative T cell acute lymphoblastic leukemia

The NF-κB signaling pathway is an important downstream pathway of oncogenic Notch1 in T cell acute lymphoblastic leukemia (T-ALL) cells. However, the molecular mechanisms underlying the cascade activation of Notch1 in T-ALL cells are poorly understood. Here, we evaluated the role of CARMA1 in Notch1-induced NF-κB activation in T-ALL cells. CARMA1 was highly and specifically expressed in T-ALL cells and correlated with the prognosis of T-ALL patients. Interestingly, CARMA1 knockdown only inhibited the growth and proliferation of SIL-TAL1 fusion gene-negative T-ALL cells. In addition, CARMA1 knockdown arrested T-ALL cells at the G1 phase. Furthermore, CARMA1 knockdown significantly inhibited the proliferation of T-ALL cells in vivo and prolonged the survival of mice. Mechanistically, CARMA1 deficiency abolished Notch1-induced NF-κB transcriptional activation and significantly reduced expression levels of the NF-κB target genes c-Myc, Bcl-2, and CCR7. Taken together, these results of our study identify CARMA1 as one of the crucial mediators of Notch1-induced transformation of T-All cells, suggesting that CARMA1 is a promising therapeutic target for T-ALL due to its specific expression in lymphocytes. KEY MESSAGES: CARMA1 contributes to cell survival only in SIL-TAL1 negative T-ALL cells. CARMA1 is a crucial mediator of Notch1-induced activation of NF-κB pathway. CARMA1 is a promising therapeutic target for T-ALL.

Network Analysis Reveals Synergistic Genetic Dependencies for Rational Combination Therapy in Philadelphia Chromosome-Like Acute Lymphoblastic Leukemia

PURPOSE

Systems biology approaches can identify critical targets in complex cancer signaling networks to inform new therapy combinations that may overcome conventional treatment resistance.

EXPERIMENTAL DESIGN

We performed integrated analysis of 1,046 childhood B-ALL cases and developed a data-driven network controllability-based approach to identify synergistic key regulator targets in Philadelphia chromosome-like B-acute lymphoblastic leukemia (Ph-like B-ALL), a common high-risk leukemia subtype associated with hyperactive signal transduction and chemoresistance.

RESULTS

We identified 14 dysregulated network nodes in Ph-like ALL involved in aberrant JAK/STAT, Ras/MAPK, and apoptosis pathways and other critical processes. Genetic cotargeting of the synergistic key regulator pair STAT5B and BCL2-associated athanogene 1 (BAG1) significantly reduced leukemia cell viability in vitro. Pharmacologic inhibition with dual small molecule inhibitor therapy targeting this pair of key nodes further demonstrated enhanced antileukemia efficacy of combining the BCL-2 inhibitor venetoclax with the tyrosine kinase inhibitors ruxolitinib or dasatinib in vitro in human Ph-like ALL cell lines and in vivo in multiple childhood Ph-like ALL patient-derived xenograft models. Consistent with network controllability theory, co-inhibitor treatment also shifted the transcriptomic state of Ph-like ALL cells to become less like kinase-activated BCR-ABL1-rearranged (Ph+) B-ALL and more similar to prognostically favorable childhood B-ALL subtypes.

CONCLUSIONS

Our study represents a powerful conceptual framework for combinatorial drug discovery based on systematic interrogation of synergistic vulnerability pathways with pharmacologic inhibitor validation in preclinical human leukemia models.

Optimizing the treatment of acute lymphoblastic leukemia in younger and older adults: new drugs and evolving paradigms

In the past decade, the available treatments for patients with acute lymphoblastic leukemia (ALL) have rapidly expanded, in parallel with an increased understanding of the genomic features that impact the disease biology and clinical outcomes. With the development of the anti-CD22 antibody-drug conjugate inotuzumab ozogamicin, the CD3-CD19 bispecific T-cell engager antibody blinatumomab, CD19 chimeric antigen receptor T-cell therapy, and the potent BCR-ABL1 tyrosine kinase inhibitor ponatinib, the outlook of ALL in both younger and older adults has substantially improved. The availability of highly effective drugs raised important questions concerning the optimal combination and sequence of these agents, their incorporation into frontline regimens, and the role of hematopoietic stem cell transplantation. In this review, we discuss the rapidly evolving paradigms in the treatment of ALL, highlighting both established and effective regimens, as well as promising new therapies that are being evaluated in ongoing clinical trials. We specifically focus on novel combination regimens in both the frontline and salvage settings that are leading to new standards of care in the treatment of ALL.

A reporter system for enriching CRISPR/Cas9 knockout cells in technically challenging settings like patient models

CRISPR/Cas9 represents a valuable tool to determine protein function, but technical hurdles limit its use in challenging settings such as cells unable to grow in vitro like primary leukemia cells and xenografts derived thereof (PDX). To enrich CRISPR/Cas9-edited cells, we improved a dual-reporter system and cloned the genomic target sequences of the gene of interest (GOI) upstream of an out-of-frame fluorochrome which was expressed only upon successful gene editing. To reduce rounds of in vivo passaging required for PDX leukemia growth, targets of 17 GOI were cloned in a row, flanked by an improved linker, and PDX cells were lentivirally transduced for stable expression. The reporter enriched scarce, successfully gene-edited PDX cells as high as 80%. Using the reporter, we show that KO of the SRC-family kinase LYN increased the response of PDX cells of B precursor cell ALL towards Vincristine, even upon heterozygous KO, indicating haploinsufficiency. In summary, our reporter system enables enriching KO cells in technically challenging settings and extends the use of gene editing to highly patient-related model systems.

Current Approaches to Philadelphia Chromosome-Positive B-Cell Lineage Acute Lymphoblastic Leukemia: Role of Tyrosine Kinase Inhibitor and Stem Cell Transplant

PURPOSE OF REVIEW

Over the past two decades, tyrosine kinase inhibitors (TKIs) have changed the management of patients with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL), and this has led to significant improvement in their outcome. In this review, we will provide an overview of the current understanding of treatment of Ph+ ALL focusing on TKIs, alloHSCT, and novel therapies.

RECENT FINDINGS

The advent of more potent TKIs and the novel therapeutic options including blinatumomab, inotuzumab ozogamicin, and CD19 CAR-T therapy has changed the role of allogeneic hematopoietic stem cell transplant (alloHSCT) and intensive chemotherapy. To avoid toxicity from the historical treatment strategies, a more individualized, targeted approach to therapy including detection and monitoring of measurable residual disease (MRD) has become of interest. The treatment of patients with Ph+ ALL has been rapidly evolving with a more individualized, targeted treatment and use of TKIs and novel therapy.

Cotargeting BCL-2 and MCL-1 in high-risk B-ALL

Improving survival outcomes in adult B-cell acute lymphoblastic leukemia (B-ALL) remains a clinical challenge. Relapsed disease has a poor prognosis despite the use of tyrosine kinase inhibitors (TKIs) for Philadelphia chromosome positive (Ph+ ALL) cases and immunotherapeutic approaches, including blinatumomab and chimeric antigen receptor T cells. Targeting aberrant cell survival pathways with selective small molecule BH3-mimetic inhibitors of BCL-2 (venetoclax, S55746), BCL-XL (A1331852), or MCL1 (S63845) is an emerging therapeutic option. We report that combined targeting of BCL-2 and MCL1 is synergistic in B-ALL in vitro. The combination demonstrated greater efficacy than standard chemotherapeutics and TKIs in primary samples from adult B-ALL with Ph+ ALL, Ph-like ALL, and other B-ALL. Moreover, combined BCL-2 or MCL1 inhibition with dasatinib showed potent killing in primary Ph+ B-ALL cases, but the BH3-mimetic combination appeared superior in vitro in a variety of Ph-like ALL samples. In PDX models, combined BCL-2 and MCL1 targeting eradicated ALL from Ph- and Ph+ B-ALL cases, although fatal tumor lysis was observed in some instances of high tumor burden. We conclude that a dual BH3-mimetic approach is highly effective in diverse models of high-risk human B-ALL and warrants assessment in clinical trials that incorporate tumor lysis precautions.

Venetoclax and dexamethasone synergize with inotuzumab ozogamicin-induced DNA damage signaling in B-lineage ALL

Adult patients with relapsed B-cell precursor acute lymphoblastic leukemia (BCP-ALL) have a dismal prognosis. To improve pharmacotherapy, we analyzed induction of apoptosis by venetoclax and inotuzumab ozogamicin in terms of cytotoxicity and mode of action. Flow cytometry-based analyses of mitochondrial outer membrane permeabilization (MOMP) and ataxia telangiectasia mutated activation demonstrate rapid induction of MOMP by venetoclax and DNA damage signaling by inotuzumab ozogamicin, respectively. In primary ALL samples and patient-derived xenograft (PDX) models, venetoclax and inotuzumab ozogamicin cooperated and synergized in combination with dexamethasone in vitro in all tested samples of ALL. In murine PDX models, inotuzumab ozogamicin, but not venetoclax, induced complete remission in a dose-dependent manner but constantly failed to achieve relapse-free survival. In contrast, combination therapy with venetoclax, dexamethasone, and inotuzumab ozogamicin induced long-term leukemia-free survival and treatment-free survival in all 3 ALL-PDX models tested. These data demonstrate synergistic and highly efficient pharmacotherapy in preclinical models that qualify for evaluation in clinical trials.

Dasatinib in the Management of Pediatric Patients With Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Acute leukemia is the most common cancer in childhood; in particular, acute lymphoblastic leukemia (ALL) represents roughly up to 80% of all cases of acute leukemias in children. Survival of children with ALL has dramatically improved over the last few decades, and is now over 90% (versus 40% of adult patients) in developed countries, except for in infants (i.e., children < 1 year), where no significant improvement was registered. Philadelphia positive ALL (Ph+ALL) accounts for around 3% of cases of childhood ALL, its incidence increasing with patient's age. Before the era of tyrosine-kinase inhibitors (TKIs), pediatric Ph+ALL showed a worse prognosis in comparison to other forms of ALL, and was managed with intensive chemotherapy, followed, whenever possible, by allogenic hematopoietic stem cell transplantation (HSCT) in first morphological complete remission. TKIs have revolutionized the current clinical approach, which involves combinations of imatinib plus standard chemotherapy that can abrogate the negative prognostic impact conferred by the presence of BCR/ABL1 rearrangement, resulting in the probability of event-free survival (EFS) being significantly better than that recorded in the pre-TKI era. Long-term follow-up confirms these data, questioning the role of a real advantage offered by HSCT over intensive chemotherapy plus TKI in all Ph+ALL pediatric patients. Imatinib was the first generation TKI and the prototype of targeted therapy, but over the years second- (dasatinib, nilotinib, bosutinib) and third-generation (ponatinib) TKIs showed a capacity to overcome resistance to imatinib in Ph+ hematological neoplasms. Given the effectiveness of the first-in-class TKI, imatinib, also the second-generation TKI dasatinib was incorporated in the treatment regimens of Ph+ALL. In this manuscript, we will discuss the role of this drug in pediatric Ph+ALL, analyzing the available data published to date.

Combined Application of Pan-AKT Inhibitor MK-2206 and BCL-2 Antagonist Venetoclax in B-Cell Precursor Acute Lymphoblastic Leukemia

Aberrant PI3K/AKT signaling is a hallmark of acute B-lymphoblastic leukemia (B-ALL) resulting in increased tumor cell proliferation and apoptosis deficiency. While previous AKT inhibitors struggled with selectivity, MK-2206 promises meticulous pan-AKT targeting with proven anti-tumor activity. We herein, characterize the effect of MK-2206 on B-ALL cell lines and primary samples and investigate potential synergistic effects with BCL-2 inhibitor venetoclax to overcome limitations in apoptosis induction. MK-2206 incubation reduced AKT phosphorylation and influenced downstream signaling activity. Interestingly, after MK-2206 mono application tumor cell proliferation and metabolic activity were diminished significantly independently of basal AKT phosphorylation. Morphological changes but no induction of apoptosis was detected in the observed cell lines. In contrast, primary samples cultivated in a protective microenvironment showed a decrease in vital cells. Combined MK-2206 and venetoclax incubation resulted in partially synergistic anti-proliferative effects independently of application sequence in SEM and RS4;11 cell lines. Venetoclax-mediated apoptosis was not intensified by addition of MK-2206. Functional assessment of BCL-2 inhibition via Bax translocation assay revealed slightly increased pro-apoptotic signaling after combined MK-2206 and venetoclax incubation. In summary, we demonstrate that the pan-AKT inhibitor MK-2206 potently blocks B-ALL cell proliferation and for the first time characterize the synergistic effect of combined MK-2206 and venetoclax treatment in B-ALL.

Venetoclax and Navitoclax in Combination with Chemotherapy in Patients with Relapsed or Refractory Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma

Combining venetoclax, a selective BCL2 inhibitor, with low-dose navitoclax, a BCL-X_L/BCL2 inhibitor, may allow targeting of both BCL2 and BCL-X_L without dose-limiting thrombocytopenia associated with navitoclax monotherapy. The safety and preliminary efficacy of venetoclax with low-dose navitoclax and chemotherapy was assessed in this phase I dose-escalation study (NCT03181126) in pediatric and adult patients with relapsed/refractory (R/R) acute lymphoblastic leukemia or lymphoblastic lymphoma. Forty-seven patients received treatment. A recommended phase II dose of 50 mg navitoclax for adults and 25 mg for patients <45 kg with 400 mg adult-equivalent venetoclax was identified. Delayed hematopoietic recovery was the primary safety finding. The complete remission rate was 60%, including responses in patients who had previously received hematopoietic cell transplantation or immunotherapy. Thirteen patients (28%) proceeded to transplantation or CAR T-cell therapy on study. Venetoclax with navitoclax and chemotherapy was well tolerated and had promising efficacy in this heavily pretreated patient population. SIGNIFICANCE: In this phase I study, venetoclax with low-dose navitoclax and chemotherapy was well tolerated and had promising efficacy in patients with relapsed/refractory acute lymphoblastic leukemia or lymphoblastic lymphoma. Responses were observed in patients across histologic and genomic subtypes and in those who failed available therapies including stem cell transplant.See related commentary by Larkin and Byrd, p. 1324.This article is highlighted in the In This Issue feature, p. 1307.

Efficacy of inotuzumab ozogamicin in patients with Philadelphia chromosome-positive relapsed/refractory acute lymphoblastic leukemia

BACKGROUND

Patients with relapsed/refractory (R/R) Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) have a poor prognosis and limited treatment options.

METHODS

The efficacy of inotuzumab ozogamicin (InO), a humanized anti-CD22 monoclonal antibody conjugated to the cytotoxic antibiotic calicheamicin, was evaluated in R/R ALL patients in the phase 1/2 study 1010 (NCT01363297) and open-label, randomized, phase 3 study 1022 (INO-VATE; NCT01564784). This analysis focused specifically on Ph+ R/R ALL patients. In study 1022, Ph+ patients were randomly assigned 1:1 to InO (n = 22) or standard intensive chemotherapy (SC) (n = 27) and 16 Ph+ patients in study 1010 received InO.

RESULTS

In study 1022, rates of complete remission/complete remission with incomplete hematologic recovery (CR/CRi) and minimal residual disease (MRD) negativity (patients achieving CR/CRi) were higher with InO (CR/CRi = 73%; MRD = 81%) versus SC (CR/CRi = 56%; MRD = 33%). The corresponding rates in study 1010 were 56% (CR/CRi) and 100% (MRD). The hematopoietic stem cell transplantation (HSCT) rate in study 1022 was 41% versus 19% for InO versus SC; however, there was no benefit in overall survival (median OS: 8.7 vs 8.4 months; hazard ratio, 1.17 [95% CI, 0.64-2.14]). The probability of being event-free (progression-free survival) at 12 months was greater with InO versus SC (20.1% vs 4.8%).

CONCLUSION

Given the substantial improvement in responses and rates of HSCT, InO is an important treatment option for patients with R/R Ph+ ALL. Future studies need to consider better characterization of disease characteristics, more sensitive MRD measurements, MRD-directed therapy before HSCT, and potentially combination therapies, including tyrosine kinase inhibitors.

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.

Precision medicine in acute lymphoblastic leukemia

The cure rate of childhood acute lymphoblastic leukemia (ALL) has exceeded 90% in some contemporary clinical trials. However, the dose intensity of conventional chemotherapy has been pushed to its limit. Further improvement in outcome will need to rely more heavily on molecular therapeutic as well as immuno-and cellular-therapy approaches together with precise risk stratification. Children with ETV6-RUNX1 or hyperdiploid > 50 ALL who achieve negative minimal residual disease during early remission induction are suitable candidates for reduction in treatment. Patients with Philadelphia chromosome (Ph)-positive or Ph-like ALL with ABL-class fusion should be treated with dasatinib. BH3 profiling and other preclinical methods have identified several high-risk subtypes, such as hypodiplod, early T-cell precursor, immature T-cell, KMT2A-rearranged, Ph-positive and TCF-HLF-positive ALL, that may respond to BCL-2 inhibitor venetoclax. There are other fusions or mutations that may serve as putative targets, but effective targeted therapy has yet to be established. For other high-risk patients or poor early treatment responders who do not have targetable genetic lesions, current approaches that offer hope include blinatumomab, inotuzumab and CAR-T cell therapy for B-ALL, and daratumumab and nelarabine for T-ALL. With the expanding therapeutic armamentarium, we should start focus on rational combinations of targeted therapy with non-overlapping toxicities.

Onco-Cardiology: Consensus Paper of the German Cardiac Society, the German Society for Pediatric Cardiology and Congenital Heart Defects and the German Society for Hematology and Medical Oncology

The acute and long-lasting side effects of modern multimodal tumour therapy significantly impair quality of life and survival of patients afflicted with malignancies. The key components of this therapy include radiotherapy, conventional chemotherapy, immunotherapy and targeted therapies. In addition to established tumour therapy strategies, up to 30 new therapies are approved each year with only incompletely characterised side effects. This consensus paper discusses the risk factors that contribute to the development of a potentially adverse reaction to tumour therapy and, in addition, defines specific side effect profiles for different treatment groups. The focus is on novel therapeutics and recommendations for the surveillance and treatment of specific patient groups.

Personalized therapy in pediatric high-risk B-cell acute lymphoblastic leukemia

Although cure rates for pediatric acute lymphoblastic leukemia (ALL) have now risen to more than 90%, subsets of patients with high-risk features continue to experience high rates of treatment failure and relapse. Recent work in minimal residual disease stratification and leukemia genomics have increased the ability to identify and classify these high-risk patients. In this review, we discuss this work to identify and classify patients with high-risk ALL. Novel therapeutics, which may have the potential to improve outcomes for these patients, are also discussed.

Multi-parametric single cell evaluation defines distinct drug responses in healthy hematologic cells that are retained in corresponding malignant cell types

Innate drug sensitivity in healthy cells aids identification of lineage specific anti-cancer therapies and reveals off-target effects. To characterize the diversity in drug responses in the major hematopoietic cell types, we simultaneously assessed their sensitivity to 71 small molecules utilizing a multi-parametric flow cytometry assay and mapped their proteomic and basal signaling profiles. Unsupervised hierarchical clustering identified distinct drug responses in healthy cell subsets based on their cellular lineage. Compared to other cell types, CD19+/B and CD56+/NK cells were more sensitive to dexamethasone, venetoclax and midostaurin, while monocytes were more sensitive to trametinib. Venetoclax exhibited dose-dependent cell selectivity that inversely correlated to STAT3 phosphorylation. Lineage specific effect of midostaurin was similarly detected in CD19+/B cells from healthy, acute myeloid leukemia and chronic lymphocytic leukemia samples. Comparison of drug responses in healthy and neoplastic cells showed that healthy cell responses are predictive of the corresponding malignant cell response. Taken together, understanding drug sensitivity in the healthy cell-of-origin provides opportunities to obtain a new level of therapy precision and avoid off-target toxicity.

Venetoclax and BCR-ABL Tyrosine Kinase Inhibitor Combinations: Outcome in Patients with Philadelphia Chromosome-Positive Advanced Myeloid Leukemias

BACKGROUND

Philadelphia chromosome-positive (Ph+) advanced leukemias, including acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) in myeloid blast phase (MBP), have poor outcomes. Venetoclax has shown synergism with BCR-ABL1 tyrosine kinase inhibitors (TKI) in preclinical studies. However, clinical activity of venetoclax and TKI-based regimens is unknown.

METHODS

We conducted a retrospective study on patients with Ph+ AML (n = 7) and CML-MBP (n = 9) who received venetoclax combined with TKI-based regimens at our institution.

RESULTS

Median patient age was 42 years, and the median number of prior therapy cycles was 5 (range 2-8). Nine patients received decitabine-based, and 7 received intensive chemotherapy-based regimens. Ten patients (63%) received ponatinib. The overall response rate (ORR) in 15 evaluable patients was 60% (1 complete remission [CR], 6 CR with incomplete hematologic recovery [CRi], 1 morphologic leukemia-free state, and 1 partial response). The ORR was 43% in Ph+ AML and 75% in CML-MBP. The median overall survival (OS) for all patients was 3.6 months, for AML OS was 2.0 months, and for CML-MBP OS was 10.9 months. The median relapse-free survival for AML and CML-MBP was 3.6 and 3.9 months, respectively. Compared to nonresponders, patients achieving CR/CRi had higher baseline Ph+ metaphases and BCR-ABL1 PCR.

CONCLUSIONS

Combination therapy of venetoclax with TKI-based regimens shows encouraging activity in very heavily pretreated, advanced Ph+ leukemias, particularly CML-MBP.

Philadelphia chromosome-positive acute lymphoblastic leukemia at first relapse in the era of tyrosine kinase inhibitors

Despite the advances in the management of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) with the introduction of tyrosine kinase inhibitors (TKIs), relapses remain challenging. We reviewed clinical data from adult patients with Ph + ALL who received frontline hyperCVAD chemotherapy with a TKI to determine their outcomes after first relapse. Patients with first morphological relapse after prior complete remission were evaluated for predictors of response and survival. For 57 of 233 (25%) patients, there was morphological relapse after a median of 15.9 months from first remission [range: 5.3-94]. The choice of salvage treatments was at the discretion of the treating physician. So, 43 (75%) patients received a TKI in combination with their salvage treatment. Second remission was achieved in 41 of 49 (84%) evaluable patients. Median relapse free survival (RFS) was 10.5 months [range, 0.2-81]. The 1-year and 2-year overall survival (OS) were 41% and 20% respectively. On multivariate analysis, only elevated LDH (units/L), the use of first-generation or no TKI at the time of first relapse and the achievement of a major molecular response (MMR) had a significant effect on OS (HR: 2.82, 95% CI:1.11-7.16, P = .029; HR = 2.39, 95% CI: 1.07,5.39, P = .034; HR = 0.39, 95% CI: 0.16-0.94, P = .03, respectively). Whereas, only achievement of MMR was significantly prognostic for RFS with a HR of 0.48 (95% CI: 0.23-0.98, P = .04). The OS and RFS were comparable between recipients and non-recipients of allogeneic hematopoietic stem cell transplantation (alloHSCT) at second remission, due to a higher non-relapse mortality (53%) seen in patients who underwent alloHSCT.

Venetoclax: evidence to date and clinical potential

The emergence of targeted therapy for patients with hematological diseases has permanently altered the therapeutic landscape. Immunochemotherapy regimes are now more and more being replaced by targeted therapies due to superior efficacy and better safety profiles. However, evolution and selection of subclones with continuous treatment leads to disease relapse and resistance toward these novel drugs. Venetoclax, the highly selective BCL-2 inhibitor (ABT-199), has an acceptable safety profile. To date, it has been approved for the treatment of first-line and relapsed/refractory chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). However, extension of indications can be expected in monotherapy and in combination regimens with promising outcomes in other hematological diseases. In this article, we describe the mechanism of action that stands behind the efficacy of venetoclax and provide a summary of available results from clinical trials.

Prediction of venetoclax activity in precursor B-ALL by functional assessment of apoptosis signaling

Deregulated cell death pathways contribute to leukemogenesis and treatment failure in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Intrinsic apoptosis signaling is regulated by different proapoptotic and antiapoptotic molecules: proapoptotic BCL-2 homology domain 3 (BH3) proteins activate prodeath molecules leading to cellular death, while antiapoptotic molecules including B-cell lymphoma 2 (BCL-2) prevent activation of prodeath proteins and counter-regulate apoptosis induction. Inhibition of these antiapoptotic regulators has become a promising strategy for anticancer treatment, but variable anticancer activities in different malignancies indicate the need for upfront identification of responsive patients. Here, we investigated the activity of the BCL-2 inhibitor venetoclax (VEN, ABT-199) in B-cell precursor acute lymphoblastic leukemia and found heterogeneous sensitivities in BCP-ALL cell lines and in a series of patient-derived primografts. To identify parameters of sensitivity and resistance, we evaluated genetic aberrations, gene-expression profiles, expression levels of apoptosis regulators, and functional apoptosis parameters analyzed by mitochondrial profiling using recombinant BH3-like peptides. Importantly, ex vivo VEN sensitivity was most accurately associated with functional BCL-2 dependence detected by BH3 profiling. Modeling clinical application of VEN in a preclinical trial in a set of individual ALL primografts, we identified that leukemia-free survival of VEN treated mice was precisely determined by functional BCL-2 dependence. Moreover, the predictive value of ex vivo measured functional BCL-2 dependence for preclinical in vivo VEN response was confirmed in an independent set of primograft ALL including T- and high risk-ALL. Thus, integrative analysis of the apoptosis signaling indicating mitochondrial addiction to BCL-2 accurately predicts antileukemia activity of VEN, robustly identifies VEN-responsive patients, and provides information for stratification and clinical guidance in future clinical applications of VEN in patients with ALL.

Optimized induction of mitochondrial apoptosis for chemotherapy-free treatment of BCR-ABL+acute lymphoblastic leukemia

BCR-ABL+acute lymphoblastic leukemia (ALL) in adults has a poor prognosis with allogeneic stem cell transplantation (SCT) considered the best curative option for suitable patients. We here characterize the curative potential of BH3-mimetics differentially targeting mitochondrial BCL2-family members using a combination therapy approach with dexamethasone and tyrosine kinase inhibitors targeting BCR-ABL. In BCR-ABL + ALL BH3-mimetics act by redistribution of mitochondrial activator BIM, which is strongly required for cytotoxicity of the BCL2-specific BH3-mimetic ABT-199, tyrosine kinase inhibitors (TKIs) and dexamethasone. BIM expression is enhanced by dexamethasone and TKIs and both synergize with ABT-199 in BCR-ABL + ALL. Triple combinations with ABT-199, dexamethasone and TKIs efficiently attenuate leukemia progression both in tissue culture and in primary cell xenotransplantation models. Notably, the dasatinib-containing combination led to treatment- and leukemia-free long-term survival in a BCR-ABL + mouse model. Finally, response to BH3-mimetics can be predicted for individual patients in a clinically relevant setting. These data demonstrate curative targeted and chemotherapy-free pharmacotherapy for BCR-ABL + ALL in a preclinical model. Clinical evaluation, in particular for patients not suitable for allogeneic SCT, is warranted.

Dasatinib as an investigational drug for the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults

INTRODUCTION

Acute lymphoblastic leukemia (ALL) with BCR-ABL1 translocation is an aggressive malignancy that is usually treated with intensive chemotherapy with the possibility of allogeneic stem cell transplantation. The encoded fusion protein may be important for leukemogenesis; clinical studies show that dasatinib has an antileukemic effect in combination with steroids alone or intensive chemotherapy. Areas covered: Relevant publications were identified through literature searches (the used terms being acute lymphoblastic leukemia plus dasatinib) in the PubMed database. We searched for original articles and reviews describing the pharmacology and clinical use of dasatinib in ALL with BCR-ABL1. The mechanism of action, pharmacology and clinical study findings are examined. Expert opinion: Dasatinib is associated with a high complete remission rate in ALL when used alone and in combination with steroids or intensive chemotherapy. However, mutations at T315 and F317 are associated with dasatinib resistance. Overall toxicity has been acceptable in these studies and no unexpected toxicity was observed. It is not known whether the antileukemic effect of dasatinib differs between subsets of BCR-ABL1⁺ patients or is attributed to inhibition of the fusion protein alone, or a combined effect on several kinases, and whether dasatinib-containing combination treatment should be preferred in these patients instead of other emerging strategies, e.g. monoclonal antibodies.

Molecular Approaches to Treating Pediatric Leukemias

Over the past decades, striking progress has been made in the treatment of pediatric leukemia, approaching 90% overall survival in children with acute lymphoblastic leukemia (ALL) and 75% in children with acute myeloid leukemia (AML). This has mainly been achieved through multiagent chemotherapy including CNS prophylaxis and risk-adapted therapy within collaborative clinical trials. However, prognosis in children with refractory or relapsed leukemia remains poor and has not significantly improved despite great efforts. Hence, more effective and less toxic therapies are urgently needed. Our understanding of disease biology, molecular drivers, drug resistance and, thus, the possibility to identify children at high-risk for treatment failure has significantly improved in recent years. Moreover, several new drugs targeting key molecular pathways involved in leukemia development, cell growth, and proliferation have been developed and approved. These striking achievements are linked to the great hope to further improve survival in children with refractory and relapsed leukemia. This review gives an overview on current molecularly targeted therapies in children with leukemia, including kinase, and proteasome inhibitors, epigenetic and enzyme targeting, as well as apoptosis regulators among others.

Dasatinib and navitoclax act synergistically to target NUP98-NSD1+/FLT3-ITD+ acute myeloid leukemia

Acute myeloid leukemia (AML) with co-occurring NUP98-NSD1 and FLT3-ITD is associated with unfavorable prognosis and represents a particularly challenging treatment group. To identify novel effective therapies for this AML subtype, we screened patient cells and engineered cell models with over 300 compounds. We found that mouse hematopoietic progenitors co-expressing NUP98-NSD1 and FLT3-ITD had significantly increased sensitivity to FLT3 and MEK-inhibitors compared to cells expressing either aberration alone (P < 0.001). The cells expressing NUP98-NSD1 alone had significantly increased sensitivity to BCL2-inhibitors (P = 0.029). Furthermore, NUP98-NSD1⁺/FLT3-ITD⁺ patient cells were also very sensitive to BCL2-inhibitor navitoclax, although the highest select sensitivity was found to SRC/ABL-inhibitor dasatinib (mean IC_50 =2.2 nM). Topoisomerase inhibitor mitoxantrone was the least effective drug against NUP98-NSD1⁺/FLT3-ITD⁺ AML cells. Of the 25 significant hits, four remained significant also compared to NUP98-NSD1^-/FLT3-ITD⁺ AML patients. We found that SRC/ABL-inhibitor dasatinib is highly synergistic with BCL2-inhibitor navitoclax in NUP98-NSD1⁺/FLT3-ITD⁺ cells. Gene expression analysis supported the potential relevance of dasatinib and navitoclax by revealing significantly higher expression of BCL2A1, FGR, and LCK in NUP98-NSD1⁺/FLT3-ITD⁺ patients compared to healthy CD34+ cells. Our data suggest that dasatinib-navitoclax combination may offer a clinically relevant treatment strategy for AML with NUP98-NSD1 and concomitant FLT3-ITD.

How I treat Philadelphia chromosome-positive acute lymphoblastic leukemia

The introduction of agents targeted at specific molecular events is changing the treatment paradigms in a number of malignancies. Historically, we have relied entirely on DNA-interactive, cytotoxic drugs for treating patients with leukemia. Increased understanding of the leukemic cell biology and pathogenesis, and the ways they evade the immune surveillance mechanisms, will likely lead to the development of more effective agents, and regimens less reliant on chemotherapy, able to achieve deep levels of disease eradication. In Philadelphia chromosome-positive acute lymphoblastic leukemia, the introduction of increasingly potent tyrosine kinas inhibitors (TKIs) has revolutionized therapy. These drugs have been established as the cornerstone of any therapeutic strategy in this disease, and a number of trials have better defined the best ways to incorporate them into the established paradigms. Despite using TKIs, we have continued to remain reliant on cytotoxic chemotherapy regimens and allogeneic hematopoietic cell transplant to achieve the best long-term outcomes. However, with the introduction of more potent TKIs and other novel agents, as well as better methods for monitoring minimal/measurable residual disease, we are entering an era where we hope to diminish our reliance on transplantation and cytotoxic chemotherapy in this disease.

The expression and role of miR-181a in multiple myeloma

This study aims to investigate the role of miR-181a in multiple myeloma (MM). Fresh peripheral blood and bone marrows were collected. Expression of miR-181a, BCL-2 mRNA, and NOVA1 mRNA was detected by RT-qPCR. The correlation between miR-181a and clinical features of MM was further analyzed. miR-181a in serum and bone marrow mononuclear cells of MM patients were significantly higher. And, miR-181a level was significantly higher in MM Durie-Salmon stage III than that in stage I+II. miR-181a was positively correlated to Durie-Salmon staging, age, kidney injury, bone injury, β2-MG whereas negatively related to red blood cell, hemoglobin, and albumin. Additionally, BCL-2 and NOVA1 were predicted to be downstream targets of miR-181a. BCL-2 mRNA was significantly higher in the bone marrow mononuclear cells from MM patients. To sum up, the miR-181a expression is increased in peripheral blood and bone marrow of MM patients and is closely related to the clinical pathological indicators of MM.

BCL2 inhibitor ABT-199 and JNK inhibitor SP600125 exhibit synergistic cytotoxicity against imatinib-resistant Ph+ ALL cells

Imatinib (IMT), a specific tyrosine kinase inhibitor (TKI), has drastically changed the treatment strategy for Ph+ ALL (Philadelphia chromosome-positive acute lymphoblastic leukemia). However, TKI resistance remains a serious problem for patient prognosis. Here, a Ph+ ALL cell line NphA2 and the IMT-resistant subline NphA2/STIR were analyzed to identify a potential novel treatment strategy. We also examined other Ph+ ALL cells, MR87 and its IMT-resistant subline, MR87/STIR. IMT induced apoptosis of NphA2 and MR87 but had no effect on resistant sublines. Increased phosphorylated ERK and BCL2, but not BCL-XL, were observed in NphA2/STIR compared with NphA2. NphA2/STIR but not NphA2 was moderately sensitive to U0126, an ERK inhibitor. Interestingly, SP600125, a JNK inhibitor, was potent in cell growth inhibition and apoptosis induction of both parental and IMT-resistant NphA2 and MR87 cells. Moreover, NphA2 and MR87 and their IMT-resistant sublines were sensitive to ABT-199, a specific BCL2 inhibitor. The combination of SP600125 and ABT-199 synergistically suppressed both parental and IMT-resistant cells, including one with T315I mutation, suggesting that Ph+ ALL exhibits high sensitivity to ABT-199 and SP600125 regardless of TKI resistance. This combination might be a possible therapeutic strategy for Ph+ ALL in the future.

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SP600125 JNK inhibitor is cytotoxic against imatinib-resistant Ph+ ALL cells.

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BCl2 inhibitor ABT 199 exhibits cytotoxicity against imatinib-resistant Ph+ ALL.

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SP600125 and ABT199 are synergistic in imatinib-resistant Ph+ ALL with T315I.

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Some leukemia cells are sensitive to MCL1 inhibitor maritoclax but not to ABT-199.

Novel Therapies for Older Adults With Acute Lymphoblastic Leukemia

PURPOSE OF REVIEW

Older adults with acute lymphoblastic leukemia (ALL) have worse survival compared to their younger counterparts. Here, we review the reasons for the poorer outcomes of older patients with ALL and also summarize the current and future therapeutic approaches to ALL in the elderly population.

RECENT FINDINGS

The poor outcomes of older adults with ALL are driven largely by lack of tolerance to standard-dose chemotherapy, which leads to unacceptably high rates of myelosuppression-related deaths. Recent studies have shown promising results with the use of low-intensity or chemotherapy-free regimens in older patients with ALL, which are able to retain efficacy without excess toxicity. Novel antibody constructs such as inotuzumab ozogamicin and blinatumomab as well as potent later-generation tyrosine kinase inhibitors such as ponatinib hold significant promise in the management of ALL in the older adult. Innovative combination strategies may further improve the outcomes of these patients.

The oncogenic tyrosine kinase Lyn impairs the pro-apoptotic function of Bim

Phosphorylation of Ser/Thr residues is a well-established modulating mechanism of the pro-apoptotic function of the BH3-only protein Bim. However, nothing is known about the putative tyrosine phosphorylation of this Bcl-2 family member and its potential impact on Bim function and subsequent Bax/Bak-mediated cytochrome c release and apoptosis. As we have previously shown that the tyrosine kinase Lyn could behave as an anti-apoptotic molecule, we investigated whether this Src family member could directly regulate the pro-apoptotic function of Bim. In the present study, we show that Bim is phosphorylated onto tyrosine residues 92 and 161 by Lyn, which results in an inhibition of its pro-apoptotic function. Mechanistically, we show that Lyn-dependent tyrosine phosphorylation of Bim increases its interaction with anti-apoptotic members such as Bcl-xL, therefore limiting mitochondrial outer membrane permeabilization and subsequent apoptosis. Collectively, our data uncover one molecular mechanism through which the oncogenic tyrosine kinase Lyn negatively regulates the mitochondrial apoptotic pathway, which may contribute to the transformation and/or the chemotherapeutic resistance of cancer cells.

Venetoclax: Targeting BCL2 in Hematological Cancers

Over the last years, targeted anti-cancer therapy with small-molecule inhibitors and antibodies moved to the forefront as a strategy to treat hematological cancers. These novel agents showed outstanding effects in treatment of patients, often irrespective of their underlying genetic features. However, evolution and selection of subclones with continuous treatment leads to disease relapse and resistance toward these novel drugs. Venetoclax (ABT-199) is a novel, orally bioavailable small-molecule inhibitor for selective targeting of B-cell lymphoma 2 (BCL2). Venetoclax is in clinical development and shows high efficacy and safety in particular in the treatment of chronic lymphocytic leukemia (CLL), but preliminarily also in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). The most important and impressive outcomes of venetoclax treatment include a rapid induction of apoptosis and drastic reduction of the tumor bulk within a few hours after administration. Venetoclax was approved by the FDA and EMA in 2016 for patients with previously treated CLL with del(17p13) and patients failing B cell receptor signaling inhibitors (EMA only), on the basis of a single-arm phase II trial demonstrating a tremendous response rate of 79% with complete remission in 20% of cases and an estimated 1-year progression-free survival of 72%. This review focuses on the mode of action, the preclinical models, and outcomes from various clinical trials with venetoclax in different hematologic cancers as well as future development.