CD19: A multifunctional immunological target molecule and its implications for Blineage acute lymphoblastic leukemia

Treatment of Relapsed Acute Lymphocytic Leukemia in Adult Patients

OPINION STATEMENT

For adult patients diagnosed with relapsed B cell-ALL (B-ALL), there have been significant improvements in available treatment options following the FDA approval of novel cellular and immunotherapy approaches - blinatumomab, chimeric antigen receptor (CAR) T therapy, and inotuzumab. For the last several years, research has focused on gaining a better understanding of the effects of specific disease and patient characteristics on long-term outcomes with each of the FDA-approved agents. In combination with the better prevention and management of unique, treatment-specific toxicities, providers can now select the best available treatment option for each individual patient diagnosed with relapsed, adult B-ALL needing therapy. This has allowed more patients to proceed to consolidative hematopoietic stem cell transplant (HSCT), and long-term data has even brought into question the need for HSCT for long-term durable remission for all patients. However, with the adoption of blinatumomab, CAR T therapy, and inotuzumab in front-line treatment regimens, it remains unclear what effects this will have on patients with relapsed B-ALL following exposure to these novel cellular and immunotherapy therapies. Unlike B-ALL, similar advances have unfortunately not yet been realized in T cell-ALL (T-ALL). Currently, new therapeutic approaches are underway to utilize similar targeting strategies that have been successful in B-ALL - monoclonal antibodies, bispecific T-cell engagers (BiTE), and CAR T therapy. Like B-ALL, the only existing approved therapy for relapsed T-ALL, nelarabine, is now used in the upfront treatment setting potentially limiting its utility in relapsed disease. Over the next several years, the hope is for patients diagnosed with T-ALL to experience the drastic improvement in outcomes as has been seen for patients diagnosed with B-ALL over the last decade.

Commonly Assessed Markers in Childhood BCP-ALL Diagnostic Panels and Their Association with Genetic Aberrations and Outcome Prediction

Immunophenotypic characterization of leukemic cells with the use of flow cytometry (FC) is a fundamental tool in acute lymphoblastic leukemia (ALL) diagnostics. A variety of genetic aberrations underlie specific B-cell precursor ALL (BCP-ALL) subtypes and their identification is of great importance for risk group stratification. These aberrations include: ETV6::RUNX1 fusion gene, Philadelphia chromosome (BCR::ABL1 fusion gene), rearrangements of the KMT2A, TCF3::PBX1 fusion gene and changes in chromosome number (hyperdiploidy and hypodiploidy). Diagnostic panels for BCP-ALL usually include B-cell lineage specific antigens: CD19, CD10, CD20, maturation stage markers: CD34, CD10, CD38, TdT, IgM and other markers useful for possible genetic subtype indication. Some genetic features of leukemic cells (blasts) are associated with expression of certain antigens. This review comprehensively summarizes all known research data on genotype-immunophenotype correlations in BCP-ALL. In some cases, single molecules are predictive of particular genetic subtypes, i.e., NG2 with KMT2A gene rearrangements or CD123 with hyperdiploidy. However, much more information on possible genotype or prognosis can be obtained with wider (≥8-color) panels. In several studies, a quantitative antigen expression scale and advanced statistical analyses were used to further increase the specificity and sensitivity of genotype/immunophenotype correlation detection. Fast detection of possible genotype/immunophenotype correlations makes multicolor flow cytometry an essential tool for initial leukemia diagnostics and stratification.

Novel Treatments for Pediatric Relapsed or Refractory Acute B-Cell Lineage Lymphoblastic Leukemia: Precision Medicine Era

With the markedly increased cure rate for children with newly diagnosed pediatric B-cell acute lymphoblastic leukemia (B-ALL), relapse and refractory B-ALL (R/R B-ALL) remain the primary cause of death worldwide due to the limitations of multidrug chemotherapy. As we now have a more profound understanding of R/R ALL, including the mechanism of recurrence and drug resistance, prognostic indicators, genotypic changes and so on, we can use newly emerging technologies to identify operational molecular targets and find sensitive drugs for individualized treatment. In addition, more promising and innovative immunotherapies and molecular targeted drugs that are expected to kill leukemic cells more effectively while maintaining low toxicity to achieve minimal residual disease (MRD) negativity and better bridge hematopoietic stem cell transplantation (HSCT) have also been widely developed. To date, the prognosis of pediatric patients with R/R B-ALL has been enhanced markedly thanks to the development of novel drugs. This article reviews the new advancements of several promising strategies for pediatric R/R B-ALL.

CAR-expressing NK cells for cancer therapy: a new hope

Since the approval in 2017 and the amazing achievement of Kymriah and Yescarta, the number of basic researchers and clinical trials investigating the safety and efficacy of chimeric antigen receptor-expressing T cells (CAR-T cells) has been relentlessly increasing. Up to now, more than 200 clinical trials are listed on clinical trial database of NIH and the basic research is countless. However, the production of allogeneic CAR-T cells products is still expensive and has toxicity. Thus, more effort is needed to develop reliable off-the-shelf cellular therapeutic methods with safety and efficiency for the treatment of patients with cancer. As a kind of innate effector lymphocyte with potent antitumor activity, natural killer cells (NK cells) have attracted much attention. Until now, basic and clinical research has shown that chimeric antigen receptor-expressing NK cell (CAR-NK) therapy may play a significant anti-tumor role and its safety is higher than CAR-T cell therapy. In this review, we discuss advantages and shortages of employing CAR-NK cells as a novel cellular therapy against cancer.

Chimeric antigen receptor (CAR)-modified NK cells against cancer: Opportunities and challenges

NK cells may have great potential in tumor immunotherapy because they can kill tumor cells directly and quickly. Chimeric antigen receptor is a fusion protein composed of extracellular antigen recognition domain, transmembrane domain and intracellular signal domain. Rapid development of CAR-modified T cells has made tremendous achievements in the treatment of malignancies, especially hematological malignancies. However, there are many deficiencies in clinical application of CAR-T cell therapy. Car-modified NK cells have attracted much attention because they may avoid these shortcomings. At present, preclinical and clinical studies have shown that CAR-NK cell therapy may play significant anti-tumor role and it is safer than CAR-T cell therapy. Nevertheless, CAR-NK cell therapy still faces some challenges, such as the expansion and activation of primary NK cells in vitro, the difficulty to store and ship NK cell products and the low transduction efficiency. Thus further research is still needed to optimize CAR-NK cell therapy. Building better CAR-NK cells is important to improve the treatment efficacy and combination therapy offers a novel direction of NK-cell based immunotherapy.

CD19-specific triplebody SPM-1 engages NK and γδ T cells for rapid and efficient lysis of malignant B-lymphoid cells

Triplebodies are antibody-derived recombinant proteins carrying 3 antigen-binding domains in a single polypeptide chain. Triplebody SPM-1 was designed for lysis of CD19-bearing malignant B-lymphoid cells through the engagement of CD16-expressing cytolytic effectors, including NK and γδ T cells.

SPM-1 is an optimized version of triplebody ds(19-16-19) and includes humanization, disulfide stabilization and the removal of potentially immunogenic sequences. A three-step chromatographic procedure yielded 1.7 - 5.5 mg of purified, monomeric protein per liter of culture medium. In cytolysis assays with NK cell effectors, SPM-1 mediated potent lysis of cancer-derived B cell lines and primary cells from patients with various B-lymphoid malignancies, which surpassed the ADCC activity of the therapeutic antibody Rituximab. EC₅₀-values ranged from 3 to 86 pM. Finally, in an impedance-based assay, SPM-1 mediated a particularly rapid lysis of CD19-bearing target cells by engaging and activating both primary and expanded human γδ T cells from healthy donors as effectors.

These data establish SPM-1 as a useful tool for a kinetic analysis of the cytolytic reactions mediated by γδ T and NK cells and as an agent deserving further development towards clinical use for the treatment of B-lymphoid malignancies.

Differences in Expansion Potential of Naive Chimeric Antigen Receptor T Cells from Healthy Donors and Untreated Chronic Lymphocytic Leukemia Patients

Introduction

Therapy with chimeric antigen receptor T (CART) cells for hematological malignancies has shown promising results. Effectiveness of CART cells may depend on the ratio of naive (T_N) vs. effector (T_E) T cells, T_N cells being responsible for an enduring antitumor activity through maturation. Therefore, we investigated factors influencing the T_N/T_E ratio of CART cells.

Materials and methods

CART cells were generated upon transduction of peripheral blood mononuclear cells with a CD19.CAR-CD28-CD137zeta third generation retroviral vector under two different stimulating culture conditions: anti-CD3/anti-CD28 antibodies adding either interleukin (IL)-7/IL-15 or IL-2. CART cells were maintained in culture for 20 days. We evaluated 24 healthy donors (HDs) and 11 patients with chronic lymphocytic leukemia (CLL) for the composition of cell subsets and produced CART cells. Phenotype and functionality were tested using flow cytometry and chromium release assays.

Results

IL-7/IL-15 preferentially induced differentiation into T_N, stem cell memory (T_SCM: naive CD27+ CD95+), CD4+ and CXCR3+ CART cells, while IL-2 increased effector memory (T_EM), CD56+ and CD4+ T regulatory (T_Reg) CART cells. The net amplification of different CART subpopulations derived from HDs and untreated CLL patients was compared. Particularly the expansion of CD4+ CART_N cells differed significantly between the two groups. For HDs, this subtype expanded >60-fold, whereas CD4+ CART_N cells of untreated CLL patients expanded less than 10-fold. Expression of exhaustion marker programmed cell death 1 on CART_N cells on day 10 of culture was significantly higher in patient samples compared to HD samples. As the percentage of malignant B cells was expectedly higher within patient samples, an excessive amount of B cells during culture could account for the reduced expansion potential of CART_N cells in untreated CLL patients. Final T_N/T_E ratio stayed <0.3 despite stimulation condition for patients, whereas this ratio was >2 in samples from HDs stimulated with IL-7/IL-15, thus demonstrating efficient CART_N expansion.

Conclusion

Untreated CLL patients might constitute a challenge for long-lasting CART effects in vivo since only a low number of T_N among the CART product could be generated. Depletion of malignant B cells before starting CART production might be considered to increase the T_N/T_E ratio within the CART product.

Treatment of Relapsed/Refractory Acute Lymphoblastic Leukemia in Adults

Patients with relapsed and refractory acute lymphoblastic leukemia (ALL) have a dismal prognosis with less than 10 % of patients surviving 5 years. Most such patients cannot be rescued with currently available therapies, whatever the initial treatment they receive. Therefore, there is an urgent need for novel treatment options. Fortunately, over the past several years, an improved understanding of the biology of the disease has allowed the identification of rational molecular targets for therapeutic endeavors and the emergence of novel therapies has sparked great interest. This review will discuss the current treatment landscape for adult patients with relapsed and/or refractory ALL.

Whole genome gene expression changes and hematological effects of rikkunshito in patients with advanced non-small cell lung cancer receiving first line chemotherapy

It has been demonstrated that the traditional Chinese medicine rikkunshito, ameliorates anorexia in several types of human cancer and attenuates lung injury by inhibiting neutrophil infiltration. The current study investigated the clinical and hematological effects of rikkunshito and its underlying mechanisms of action in the treatment of advanced non-small cell lung cancer (NSCLC). The Illumina microarray BeadChip was used to analyze the whole-genome expression profiles of peripheral blood mononuclear cells in 17 patients with advanced NSCLC. These patients were randomized to receive combination chemotherapy (cisplatin and gemcitabine) with (n=9, CTH+R group) or without (n=8, CTH group) rikkunshito. The primary endpoint was the treatment response and the categories of the scales of anorexia, nausea, vomiting and fatigue; secondary endpoints included the hematological effect and whole genome gene expression changes. The results of the current study indicated that there were no significant differences in clinical outcomes, including treatment response and toxicity events, between the two groups. Median one-year overall survival (OS) was 12 months in the CTH group and 11 months in the CTH+R group (P=0.058 by log-rank test), while old age (>60 years old) was the only independent factor associated with one-year OS (hazard ratio 1.095, 95% confidence interval, 1.09–1.189, P=0.030). Patients in the CTH+R group experienced significantly greater maximum decreases in both white cell count (P=0.034) and absolute neutrophil count (P=0.030) from the baseline. A total of 111 genes associated with neutrophil apoptosis, the cell-killing ability of neutrophils, natural killer cell activation and B cell proliferation were up-regulated following rikkunshito treatment. A total of 48 genes associated with neutrophil migration, coagulation, thrombosis and type I interferon signaling were down-regulated following rikkunshito treatment. Rikkunshito may therefore affect the blood neutrophil count when used with combination chemotherapy in patients with NSCLC, potentially by down-regulating prostaglandin-endoperoxidase synthase 1, MPL, AMICA1 and junctional adhesion molecule 3, while up-regulating elastase, neutrophil expressed, proteinase 3, cathepsin G and cluster of differentiation 24.

CD19-CAR engineered NK-92 cells are sufficient to overcome NK cell resistance in B-cell malignancies

Many B‐cell acute and chronic leukaemias tend to be resistant to killing by natural killer (NK) cells. The introduction of chimeric antigen receptors (CAR) into T cells or NK cells could potentially overcome this resistance. Here, we extend our previous observations on the resistance of malignant lymphoblasts to NK‐92 cells, a continuously growing NK cell line, showing that anti‐CD19‐CAR (αCD19‐CAR) engineered NK‐92 cells can regain significant cytotoxicity against CD19 positive leukaemic cell lines and primary leukaemia cells that are resistant to cytolytic activity of parental NK‐92 cells. The ‘first generation’ CAR was generated from a scFv (CD19) antibody fragment, coupled to a flexible hinge region, the CD3ζ chain and a Myc‐tag and cloned into a retrovirus backbone. No difference in cytotoxic activity of NK‐92 and transduced αCD19‐CAR NK‐92 cells towards CD19 negative targets was found. However, αCD19‐CAR NK‐92 cells specifically and efficiently lysed CD19 expressing B‐precursor leukaemia cell lines as well as lymphoblasts from leukaemia patients. Since NK‐92 cells can be easily expanded to clinical grade numbers under current Good Manufactoring Practice (cGMP) conditions and its safety has been documented in several phase I clinical studies, treatment with CAR modified NK‐92 should be considered a treatment option for patients with lymphoid malignancies.

Large-Scale Culture and Genetic Modification of Human Natural Killer Cells for Cellular Therapy

Recent advances in methods for the ex vivo expansion of human natural killer (NK) cells have facilitated the use of these powerful immune cells in clinical protocols. Further, the ability to genetically modify primary human NK cells following rapid expansion allows targeting and enhancement of their immune function. We have successfully adapted an expansion method for primary NK cells from peripheral blood mononuclear cells or from apheresis products in gas permeable rapid expansion devices (G-Rexes). Here, we describe an optimized protocol for rapid and robust NK cell expansion as well as a method for highly efficient retroviral transduction of these ex vivo expanded cells. These methodologies are good manufacturing practice (GMP) compliant and could be used for clinical-grade product manufacturing.

Blinatumomab for the Treatment of Philadelphia Chromosome-Negative, Precursor B-cell Acute Lymphoblastic Leukemia

Blinatumomab is a CD19/CD3 bispescific antibody designed to redirect T cells toward malignant B cells and induce their lysis. It recently gained accelerated approval by the FDA for the treatment of relapsed or refractory Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia (RR-ALL). In the phase II trial that served as the basis for approval, blinatumomab demonstrated significant single-agent activity and induced remission [complete remission (CR) and CR with incomplete recovery of peripheral blood counts (CRh)] in 43% of 189 adult patients with RR-ALL; the majority of responders (82%) also attained negative minimal residual disease (MRD(-)) status that did not generally translate into long-term remissions in most cases. Additional studies show that blinatumomab can induce high response rates associated with lasting remissions in patients in first remission treated for MRD positivity, suggesting a role for blinatumomab in the upfront, MRD-positive setting. Blinatumomab infusion follows a predictable immunopharmacologic profile, including early cytokine release that can be associated with a clinical syndrome, T-cell expansion, and B-cell depletion. Neurologic toxicities represent a unique toxicity that shares similarities with adverse effects of other T-cell engaging therapies. Further studies are needed to clarify the optimal disease setting and timing for blinatumomab therapy. Additional insights into the pathogenesis, risk factors, and prevention of neurologic toxicities as well as a better understanding of the clinical consequences and biologic pathways that are associated with drug resistance are needed.

The pre-B-cell receptor checkpoint in acute lymphoblastic leukaemia

The B-cell receptor (BCR) and its immature form, the precursor-BCR (pre-BCR), have a central role in the control of B-cell development, which is dependent on a sequence of cell-fate decisions at specific antigen-independent checkpoints. Pre-BCR expression provides the first checkpoint, which controls differentiation of pre-B to immature B-cells in normal haemopoiesis. Pre-BCR signalling regulates and co-ordinates diverse processes within the pre-B cell, including clonal selection, proliferation and subsequent maturation. In B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), B-cell development is arrested at this checkpoint. Moreover, malignant blasts avoid clonal extinction by hijacking pre-BCR signalling in favour of the development of BCP-ALL. Here, we discuss three mechanisms that occur in different subtypes of BCP-ALL: (i) blocking pre-BCR expression; (ii) activating pre-BCR-mediated pro-survival and pro-proliferative signalling, while inhibiting cell cycle arrest and maturation; and (iii) bypassing the pre-BCR checkpoint and activating pro-survival signalling through pre-BCR independent alternative mechanisms. A complete understanding of the BCP-ALL-specific signalling networks will highlight their application in BCP-ALL therapy.

Profile of blinatumomab and its potential in the treatment of relapsed/refractory acute lymphoblastic leukemia

The CD19 marker is expressed on the surface of normal and malignant immature or mature B-cells. On the other hand, immunotherapy involving T-cells is a promising modality of treatment for many neoplastic diseases including leukemias and lymphomas. The CD19/CD3-bispecific T-cell-engaging (BiTE^®) monoclonal antibody blinatumomab can transiently engage cytotoxic T-cells to CD19+ target B-cells inducing serial perforin-mediated lysis. In the first clinical trial, blinatumomab showed efficacy in non-Hodgkin’s lymphomas, but the most important trials have been conducted in relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) and in ALL with minimal residual disease. Encouraging reports on the activity of blinatumomab in R/R Philadelphia chromosome-negative B-cell precursor ALL led to its approval by the US Food and Drug Administration on December 3, 2014 after an accelerated review process. This review focuses on the profile of blinatumomab and its activity in R/R ALL.