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

Antibody-drug conjugates and bispecific antibodies targeting cancers: applications of click chemistry

Engineering approaches using antibody drug conjugates (ADCs) and bispecific antibodies (bsAbs) are designed to overcome the limitations of conventional chemotherapies and therapeutic antibodies such as drug resistance and non-specific toxicity. Cancer immunotherapies have been shown to be clinically successful with checkpoint blockade and chimeric antigen receptor T cell therapy; however, overactive immune systems still represent a major problem. Given the complexity of a tumor environment, it would be advantageous to have a strategy targeting two or more molecules. We highlight the necessity and importance of a multi-target platform strategy against cancer. Approximately 400 ADCs and over 200 bsAbs are currently being clinically developed for several indications, with promising signs of therapeutic activity. ADCs include antibodies that recognize tumor antigens, linkers that stably connect drugs, and powerful cytotoxic drugs, also known as payloads. ADCs have direct therapeutic effects by targeting cancers with a strong payload. Another type of drug that uses antibodies are bsAbs, targeting two antigens by linking to antigen recognition sites or bridging cytotoxic immune cells to tumor cells, resulting in cancer immunotherapy. Three bsAbs and one ADC have been approved for use by the FDA and the EMA in 2022. Among these, two of the bsAbs and the one ADC are used for cancers. We introduced that bsADC, a combination of ADC and bsAbs, has yet to be approved and several candidates are in the early stages of clinical development in this review. bsADCs technology helps increase the specificity of ADCs or the internalization and killing ability of bsAbs. We also briefly discuss the application of click chemistry in the efficient development of ADCs and bsAbs as a conjugation strategy. The present review summarizes the ADCs, bsAbs, and bsADCs that have been approved for anti-cancer or currently in development. These strategies selectively deliver drugs to malignant tumor cells and can be used as therapeutic approaches for various types of cancer.

Neurology of cancer immunotherapy

BACKGROUND

Immunotherapy is nowadays considered a mainstay of cancer treatment, dramatically affecting the disease-free survival rate in several aggressive malignancies. Unfortunately, cancer immunotherapy can also trigger life-threatening autoimmune neurological complications named "neurological adverse effects" (NAEs). NAEs can affect both the central nervous system (CNS), as in ipilimumab-related aseptic meningitis, and the peripheral nervous system (PNS), as in nivolumab-induced myasthenia gravis.

CURRENT EVIDENCE

The incidence of NAEs is highly variable, ranging from 2 to 4% using checkpoint inhibitors to 50% using blinatumomab. Looking at these numbers, it appears clear that neurologists will soon be called more and more frequently to decide upon the best therapeutic strategy for a patient receiving immunotherapy and experiencing a NAE. Most of them can be treated or reverted withholding the offending drug and adding IVIg, plasmapheresis, or steroids to the therapy. Sometimes, however, for oncological reasons, immunotherapy cannot be stopped so the neurologist needs to know what countermeasures have proven most effective. Moreover, patients with a pre-existing autoimmune neurological disease (AID), such as myasthenia gravis or multiple sclerosis, might need immunotherapy during their life, risking a severe worsening of their symptoms. In that setting, the neurologist needs to properly counsel patients about the risk of a therapy-related relapse.

CONCLUSION

In this article, we describe the most frequently reported NAEs and aim to give neurologists a practical overview on how to deal with them.

Combining blinatumomab and donor lymphocyte infusion in B-ALL patients relapsing after allogeneic hematopoietic cell transplantation: a study of the SFGM-TC

Relapsed B-cell acute lymphoblastic leukemia (B-ALL) after allogeneic stem cell transplantation (allo-HCT) still represents a major concern with poor outcomes. The aim of this study is to compare the efficacy and safety of blinatumomab and donor lymphocyte infusion (DLI) versus blinatumomab alone in this setting. This is a multicenter retrospective study from centers of SFGM-TC. All transplanted patients who received blinatumomab salvage therapy were included. Patients who received DLI from 1 month before to 100 days after the starting of blinatumomab were included in the blina-DLI group. Seventy-two patients were included. Medium follow-up was 38 months. Fifty received blinatumomab alone and 22 the association blinatumomab-DLI. Two-year overall survival (OS) was 31% in the blinatumomab group and 43% in the blinatumomab-DLI group (p = 0.31). Studying DLI as a time dependent variable, PFS did not significantly differ between the 2 groups (HR:0.7, 95% CI: 0.4-1.5). In multivariate analysis, DLI was not a prognostic factor for OS, progression-free survival and progression/relapse incidence. Adverse events and graft-versus-disease rates were comparable in the 2 groups. In conclusion, adding DLI between 1 month before and 100 days after start of blinatumomab is safe and does not seem to improve outcomes in B-ALL patients who relapsed after allo-HCT.

Direct CNS administration of rituximab and epratuzumab in a pediatric patient with relapsed refractory CNS B-cell acute lymphoblastic leukemia

Relapsed central nervous system (CNS) leukemia presents a therapeutic challenge to pediatric oncologists. Systemic monoclonal antibody therapy has shown recent promise in patients with relapsed acute lymphoblastic leukemia, however its effect on CNS disease in this population is not well established. We describe a case of multiply relapsed and refractory CNS leukemia in an adolescent patient who responded to the intra-CNS delivery of rituximab (anti-CD20) and epratuzumab (anti-CD22) therapy, demonstrating the practical use and potential efficacy of a novel route of monoclonal antibody administration in difficult-to-treat CNS leukemia.

Immunoglobulin repletion during blinatumomab therapy does not reduce the rate of secondary hypogammaglobulinemia and associated infectious risk

Background

Blinatumomab has demonstrated efficacy in minimal residual disease (MRD) positive and relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL) by inciting rapid and sustained B-cell depletion.

Methods

Owing to its effect on B-cells, blinatumomab is associated with a higher rate of secondary hypogammaglobulinemia compared to chemotherapy. To mitigate blinatumomab-induced hypogammaglobulinemia, patients were pre-emptively repleted with intravenous immune globulin (IVIG) during blinatumomab therapy. In this retrospective study, we compared outcomes of 23 blinatumomab treated adults with ALL. Seventeen patients routinely received IVIG and 6 patients were in the control cohort.

Results

Our findings demonstrated no difference between the two cohorts in immunoglobulin G (IgG) nadir (338 mg/dL vs. 337 mg/dL, P=0.641), days to IgG nadir (120.5 vs. 85.5 days, P=0.13), infection rate (82.4% vs. 66.7%, P=0.58), infections requiring ICU admission (23.5% vs. 16.7%, P=1), and infection related mortality (17.6% vs. 16.7%, P=1).

Conclusion

Pre-emptive IVIG repletion during blinatumomab did not prevent hypogammaglobulinemia and associated infection risk.

Neurotoxicity of Tumor Immunotherapy: The Emergence of Clinical Attention

Tumor immunotherapy brings substantial and long-term clinical benefits that can even cure tumors. However, the accumulation of evidence suggests that immunotherapy also induces severe and complex neurologic immune-related adverse events (ir-AEs) and even leads to immunotherapy-related death, which arouses the concern of clinicians. The timely and accurate identification of neurotoxicity helps clinicians detect and treat these complications early, thereby enhancing treatment efficiency and improving the prognosis of patients. At present, the mechanism of neurotoxicity caused by immunotherapy has not been completely elucidated. This paper mainly reviews the clinical features, pathogenesis, and therapeutic strategies of neurologic ir-AEs.

Antibody based therapy in relapsed acute lymphoblastic leukemia

Outcomes for relapsed and refractory acute lymphoblastic leukemia (ALL) remain poor. With the advent of targeted monoclonal antibodies and antibody constructs, these outcomes have been significantly improved both in the frontline and salvage setting. These targets include a bispecific antibody that targets both CD3 and CD19, known as blinatumomab, as well as a conjugated antibody that targets CD22, known as inotuzumab ozogamicin. These agents have been thoroughly studied and successively approved for use as monotherapy, however, more recently they have been incorporated in combination or sequentially with cytotoxic chemotherapy. In this chapter, we will discuss the role that these monoclonal antibodies play as monotherapy and in combination in the treatment of ALL in the salvage setting, and how they continue to transform the treatment management of relapsed and refractory ALL.

Involvement of the central nervous system in acute lymphoblastic leukemia: opinions on molecular mechanisms and clinical implications based on recent data

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. One of the major clinical challenges is adequate diagnosis and treatment of central nervous system (CNS) involvement in this disease. Intriguingly, there is little solid evidence on the mechanisms sustaining CNS disease in ALL. Here, we present and discuss recent data on this topic, which are mainly derived from preclinical model systems. We thereby highlight sites and routes of leukemic CNS infiltration, cellular features promoting infiltration and survival of leukemic cells in a presumably hostile niche, and dormancy as a potential mechanism of survival and relapse in CNS leukemia. We also focus on the impact of ALL cytogenetic subtypes on features associated with a particular CNS tropism. Finally, we speculate on new perspectives in the treatment of ALL in the CNS, including ideas on the impact of novel immunotherapies.

First clinical study of a pegylated diabody 124I-labeled PEG-AVP0458 in patients with tumor-associated glycoprotein 72 positive cancers

Through protein engineering and a novel pegylation strategy, a diabody specific to tumor-associated glycoprotein 72 (TAG-72) (PEG-AVP0458) has been created to optimize pharmacokinetics and bioavailability to tumor. We report the preclinical and clinical translation of PEG-AVP0458 to a first-in-human clinical trial of a diabody. Methods: Clinical translation followed characterization of PEG-AVP0458 drug product and preclinical biodistribution and imaging assessments of Iodine-124 trace labeled PEG-AVP0458 (¹²⁴I-PEG-AVP0458). The primary study objective of the first-in-human study was the safety of a single protein dose of 1.0 or 10 mg/m^{2 124}I-PEG-AVP0458 in patients with TAG-72 positive relapsed/ metastatic prostate or ovarian cancer. Secondary study objectives were evaluation of the biodistribution, tumor uptake, pharmacokinetics and immunogenicity. Patients were infused with a single-dose of ¹²⁴I labeled PEG-AVP0458 (3-5 mCi (111-185 MBq) for positron emission tomography (PET) imaging, performed sequentially over a one-week period. Safety, pharmacokinetics, biodistribution, and immunogenicity were assessed up to 28 days after infusion. Results: PEG-AVP0458 was radiolabeled with ¹²⁴I and shown to retain high TAG-72 affinity and excellent targeting of TAG-72 positive xenografts by biodistribution analysis and PET imaging. In the first-in-human trial, no adverse events or toxicity attributable to ¹²⁴I-PEG-AVP0458 were observed. Imaging was evaluable in 5 patients, with rapid and highly specific targeting of tumor and minimal normal organ uptake, leading to high tumor:blood ratios. Serum concentration values of ¹²⁴I-PEG-AVP0458 showed consistent values between patients, and there was no significant difference in T½α and T½β between dose levels with mean (± SD) results of T½α = 5.10 ± 4.58 hours, T½β = 46.19 ± 13.06 hours. Conclusions: These data demonstrates the safety and feasibility of using pegylated diabodies for selective tumor imaging and potential delivery of therapeutic payloads in cancer patients.

T cell-engaging therapies - BiTEs and beyond

Immuno-oncology approaches have entered clinical practice, with tremendous progress particularly in the field of T cell-engaging therapies over the past decade. Herein, we provide an overview of the current status of bispecific T cell engager (BiTE) therapy, considering the unprecedented new indication for such therapy in combating minimal (or measurable) residual disease in patients with acute lymphoblastic leukaemia, and the development of novel approaches based on this concept. Key aspects that we discuss include the current clinical data, challenges relating to treatment administration and patient monitoring, toxicities and resistance to treatment, and novel strategies to overcome these hurdles as well as to broaden the indications for BiTE therapy, particularly to common solid cancers. Elucidation of mechanisms of resistance and immune escape and new technologies used in drug development pave the way for new and more-effective therapies and rational combinatorial approaches. In particular, we highlight novel therapeutic agents, such as bifunctional checkpoint-inhibitory T cell engagers (CiTEs), simultaneous multiple interaction T cell engagers (SMITEs), trispecific killer engagers (TriKEs) and BiTE-expressing chimeric antigen receptor (CAR) T cells (CART.BiTE cells), designed to integrate various immune functions into one molecule or a single cellular vector and thereby enhance efficacy without compromising safety. We also discuss the targeting of intracellular tumour-associated epitopes using bispecific constructs with T cell receptor (TCR)-derived, rather than an antibody-based, antigen-recognition domains, termed immune-mobilizing monoclonal TCRs against cancer (ImmTACs), which might broaden the armamentarium of T cell-engaging therapies.

Bone Marrow Necrosis in a Patient Following Blinatumomab Therapy

Bone marrow necrosis (BMN) is an extremely rare condition characterized by necrosis of the myeloid tissue and medullary stroma leaving an amorphous eosinophilic background and ill-defined necrotic cells in the hematopoietic bone marrow. Several conditions are associated with BMN, including sickle cell disease, metastatic carcinoma, and hematologic malignancies. It is also associated with the use of antineoplastic drugs, such as fludarabine, interferon alpha, and imatinib. Blinatumomab is a CD19/CD3 bispecific T-cell engager antibody which redirects autologous CD3-positive T cells to CD19-positive lymphoblasts creating a cytolytic synapse leading to blastic cells. Cytokine release syndrome, cerebral nervous system toxicities, and febrile neutropenia are the most frequent adverse effects of blinatumomab. Here, we report an adolescent boy with relapse/resistant acute lymphoblastic leukemia developing BMN following blinatumomab therapy. To our knowledge, this is the first case report on BMN following blinatumomab treatment.

Management of toxicities associated with novel immunotherapy agents in acute lymphoblastic leukemia

The advent of novel immunotherapies, such as blinatumomab, inotuzumab, and chimeric antigen receptor (CAR) T cell therapy, has revolutionized the therapeutic landscape in the treatment of relapsed/refractory B cell acute lymphoblastic leukemia, but can be associated with specific toxicities. We review unique toxicities of each of these in this article. Blinatumomab, a bispecific T cell engager, has been associated with cytokine release syndrome (CRS) and neurological toxicities, both of which can be prevented and managed with corticosteroids. Inotuzumab is a calicheamicin-conjugated CD22 targeting antibody. The calicheamicin component of the drug is likely associated with the hepatotoxicity seen with inotuzumab, especially sinusoidal obstruction syndrome, which can happen both in the context of the drug alone, and also with allogeneic stem cell transplantation. QT prolongation has also been noted with inotuzumab. CAR T therapy uses genetically modified autologous T cells directed against CD19, a known target on B cells. CRS and neurological symptoms, formally termed as immune-effector-cell-associated neurological syndrome, have been described along with hypogammaglobulinemia, cytopenias, and infections.

Neurotoxicity of antibodies in cancer therapy: A review

The objective of this manuscript is to identify the neurological side effect profile associated with different classes of antibodies used in cancer pharmacotherapy and to estimate the frequency in which these neurotoxicity occurs. A systematic review of the literature was conducted using OVID MEDLINE and EMBASE databases for articles written between January of 2010 till August of 2018. The spectrum of neurotoxicity was searched using expanded terminology, medical subject headings, truncation, spelling variations and database specific controlled vocabulary. 2134 citations were retrieved that were narrowed down to 151 when SORT 1 or SORT 2 critical appraisal tool was applied to articles with human subjects. Meta-analysis using random effect model was done to estimate the prevalence of neurological symptoms per class of antibody described in SORT1 and SORT2 articles. It was found that the most common neurotoxicity per antibody class are as follows; Bi-specific T-cell engagers was headache 38% [35-40%; I² 0%]; anti-CD20, neuropathy, 16% [7-24%, I² 65%]; anti-CD30, neuropathy 57% [46-68%, I² 72%]; anti-CD52, neuropathy 5-15%; anti-CTL4, headache 12% [7-16%, I² 49%]; anti-EGFR, headache 25% [11-38%, I² 92%]; anti-Her2, neuropathy 33% [18-49%, I² 98%]; anti-PD1 and PDL1, headache 3% [2-5%, I² 85%]; and anti-VEGF, headache 25% [16-35%, I² 73%]. Therefore, all classes of antibodies used in cancer pharmacotherapy have associated neurotoxicity with a wide spectrum of effects afflicting the nervous system as a whole. The specific side effects and the frequency at which they occur differ per class of antibody. Broader and more severe symptoms were noted to effect patients with preexisting brain lesions.

Relapsed Philadelphia Chromosome-Positive Pre-B-ALL after CD19-Directed CAR-T Cell Therapy Successfully Treated with Combination of Blinatumomab and Ponatinib

Adults with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) treated with conventional chemotherapy have dismal outcomes. Novel immunotherapies targeting CD19, including the bispecific T-cell engager blinatumomab and chimeric antigen-receptor T (CAR-T) cells, have revolutionized the treatment of R/R B-ALL. Robust response rates to CAR-T cell therapy after blinatumomab have recently been reported, but it is unknown whether blinatumomab can be effective following failure of anti-CD19 CAR-T cell therapy. Herein, we describe a patient with Philadelphia chromosome-positive B-ALL who relapsed after CD19-directed CAR-T therapy, but subsequently responded to the combination of blinatumomab and the tyrosine kinase inhibitor ponatinib, with the achievement of a complete remission lasting 12 months.

No free rides: management of toxicities of novel immunotherapies in ALL, including financial

Therapeutic options for acute lymphoblastic leukemia, especially in the relapsed/refractory setting, have expanded significantly in recent times. However, this comes at the cost of toxicities: medical as well as financial. We highlight some of the unique toxicities associated with the novel agents to apprise our readers about what to expect, how to recognize them, and how to manage these toxicities. One of the toxicities seen with inotuzumab, a CD22 antibody drug conjugate, is sinusoidal obstruction syndrome, which can be fatal in >80% of patients if associated with multiorgan failure. Blinatumomab, a monoclonal antibody targeting CD19, is associated with cytokine release syndrome (CRS) and neurotoxicity, both of which require prompt recognition and management primarily with corticosteroids. CRS and neurotoxicity are more common and more severe with chimeric antigen receptor T-cell therapy (CAR-T). The fact that CAR-T cannot be discontinued on demand adds a layer of complexity to the management of related toxicities of this therapy. Tocilizumab, an interleukin-6 receptor blocker, is used to treat severe CRS from CAR-T, whereas corticosteroids remain the mainstay for neurotoxicity management. Although effective, these drugs carry a high price tag, and we review the available data on cost-effectiveness of these agents, keeping in mind that median follow-up on most of these studies is limited and that long-term data on durability of response remain to be seen.

No free rides: management of toxicities of novel immunotherapies in ALL, including financial

Therapeutic options for acute lymphoblastic leukemia, especially in the relapsed/refractory setting, have expanded significantly in recent times. However, this comes at the cost of toxicities: medical as well as financial. We highlight some of the unique toxicities associated with the novel agents to apprise our readers about what to expect, how to recognize them, and how to manage these toxicities. One of the toxicities seen with inotuzumab, a CD22 antibody drug conjugate, is sinusoidal obstruction syndrome, which can be fatal in >80% of patients if associated with multiorgan failure. Blinatumomab, a monoclonal antibody targeting CD19, is associated with cytokine release syndrome (CRS) and neurotoxicity, both of which require prompt recognition and management primarily with corticosteroids. CRS and neurotoxicity are more common and more severe with chimeric antigen receptor T-cell therapy (CAR-T). The fact that CAR-T cannot be discontinued on demand adds a layer of complexity to the management of related toxicities of this therapy. Tocilizumab, an interleukin-6 receptor blocker, is used to treat severe CRS from CAR-T, whereas corticosteroids remain the mainstay for neurotoxicity management. Although effective, these drugs carry a high price tag, and we review the available data on cost-effectiveness of these agents, keeping in mind that median follow-up on most of these studies is limited and that long-term data on durability of response remain to be seen.

Prognostic and therapeutic role of CLEC12A in acute myeloid leukemia

CLEC12A has recently been identified as an antigen, expressed on leukemic stem cells and leukemic blasts. Given the fact that this expression profile seems stable throughout diagnosis, treatment and relapse on leukemic blasts and leukemic stem cells, CLEC12A can be considered a highly potent and reliable marker for the detection of measurable residual disease and therefore applicable for risk stratification and prognostication in AML. Low CLEC12A expression on leukemic blasts seems to be independently associated with lower likelihood of achieving complete remission after 1 cycle of induction chemotherapy, shorter event free survival, as well as overall survival, indicating potential prognostic properties of CLEC12A expression itself. Lack of expression on the normal hematopoietic stem and progenitor cells, in contrast to CD123 and CD33, might result in less toxicity regarding cytopenias, making CLEC12A an interesting target for innovating immunotherapies, including monoclonal and bispecific antibodies, antibody-drug conjugates and CAR-T cells therapy.

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.

Primary prophylaxis of invasive fungal infections in patients with haematological malignancies: 2017 update of the recommendations of the Infectious Diseases Working Party (AGIHO) of the German Society for Haematology and Medical Oncology (DGHO)

Immunocompromised patients are at high risk of invasive fungal infections (IFI), in particular those with haematological malignancies undergoing remission-induction chemotherapy for acute myeloid leukaemia (AML) or myelodysplastic syndrome (MDS) and recipients of allogeneic haematopoietic stem cell transplants (HSCT). Despite the development of new treatment options in the past decades, IFI remains a concern due to substantial morbidity and mortality in these patient populations. In addition, the increasing use of new immune modulating drugs in cancer therapy has opened an entirely new spectrum of at risk periods. Since the last edition of antifungal prophylaxis recommendations of the German Society for Haematology and Medical Oncology in 2014, seven clinical trials regarding antifungal prophylaxis in patients with haematological malignancies have been published, comprising 1227 patients. This update assesses the impact of this additional evidence and effective revisions. Our key recommendations are the following: prophylaxis should be performed with posaconazole delayed release tablets during remission induction chemotherapy for AML and MDS (AI). Posaconazole iv can be used when the oral route is contraindicated or not feasible. Intravenous liposomal amphotericin B did not significantly decrease IFI rates in acute lymphoblastic leukaemia (ALL) patients during induction chemotherapy, and there is poor evidence to recommend it for prophylaxis in these patients (CI). Despite substantial risk of IFI, we cannot provide a stronger recommendation for these patients. There is poor evidence regarding voriconazole prophylaxis in patients with neutropenia (CII). Therapeutic drug monitoring TDM should be performed within 2 to 5 days of initiating voriconazole prophylaxis and should be repeated in case of suspicious adverse events or of dose changes of interacting drugs (BIItu). General TDM during posaconazole prophylaxis is not recommended (CIItu), but may be helpful in cases of clinical failure such as breakthrough IFI for verification of compliance or absorption.

Dual-targeting triplebody 33-3-19 mediates selective lysis of biphenotypic CD19+ CD33+ leukemia cells

Simultaneous targeting of multiple tumor-associated antigens (TAAs) in cancer immunotherapy is presumed to enhance tumor cell selectivity and to reduce immune escape.

The combination of B lymphoid marker CD19 and myeloid marker CD33 is exclusively present on biphenotypic B/myeloid leukemia cells. Triplebody 33-3-19 binds specifically to both of these TAAs and activates T cells as immune effectors. Thereby it induces specific lysis of established myeloid (MOLM13, THP-1) and B-lymphoid cell lines (BV173, SEM, Raji, ARH77) as well as of primary patient cells. EC₅₀ values range from 3 pM to 2.4 nM. In accordance with our hypothesis, 33-3-19 is able to induce preferential lysis of double- rather than single-positive leukemia cells in a target cell mixture: CD19/CD33 double-positive BV173 cells were eliminated to a significantly greater extent than CD19 single-positive SEM cells (36.6% vs. 20.9% in 3 hours, p = 0.0048) in the presence of both cell lines. In contrast, equivalent elimination efficiencies were observed for both cell lines, when control triplebody 19-3-19 or a mixture of the bispecific single chain variable fragments 19-3 and 33-3 were used. This result highlights the potential of dual-targeting agents for efficient and selective immune-intervention in leukemia patients.

The Approach to Acute Lymphoblastic Leukemia in Older Patients: Conventional Treatments and Emerging Therapies

Acute lymphoblastic leukemia (ALL) among older adult patients presents significant clinical challenges. As opposed to pediatric populations, in whom long-term outcomes are markedly superior, those for adults remain grim. Nevertheless, younger adults with ALL have experienced a steady improvement in long-term survival in the last few decades. This is significantly different for older ALL patients, for whom long-term outcomes remain poor. Conventional chemotherapies are associated with sub-optimal outcomes and increased toxicity in this population. However, several emerging therapies, including antibody-drug conjugates, bi-specific engagers, and chimeric antigen receptor (CAR) T cells, have demonstrated much promise and are either incorporated into the existing therapeutic paradigms or being actively investigated to improve outcomes.

The clonal evolution of two distinct T315I-positive BCR-ABL1 subclones in a Philadelphia-positive acute lymphoblastic leukemia failing multiple lines of therapy: a case report

BACKGROUND

The treatment of Philadelphia chromosome-positive Acute Lymphoblastic Leukemia (Ph+ ALL) patients who harbor the T315I BCR-ABL1 mutation or who have two or more mutations in the same BCR-ABL1 molecule is particularly challenging since first and second-generation Tyrosine Kinase Inhibitors (TKIs) are ineffective. Ponatinib, blinatumomab, chemotherapy and transplant are the currently available options in these cases.

CASE PRESENTATION

We here report the case of a young Ph+ ALL patient who relapsed on front-line dasatinib therapy because of two independent T315I-positive subclones, resulting from different nucleotide substitutions -one of whom never reported previously- and where additional mutant clones outgrew and persisted despite ponatinib, transplant, blinatumomab and conventional chemotherapy. Deep Sequencing (DS) was used to dissect the complexity of BCR-ABL1 kinase domain (KD) mutation status and follow the kinetics of different mutant clones across the sequential therapeutic approaches.

CONCLUSIONS

This case presents several peculiar and remarkable aspects: i) distinct clones may acquire the same amino acid substitution via different nucleotide changes; ii) the T315I mutation may arise also from an 'act' to 'atc' codon change; iii) the strategy of temporarily replacing TKI therapy with chemo or immunotherapy, in order to remove the selective pressure and deselect aggressive mutant clones, cannot always be expected to be effective; iv) BCR-ABL1-mutated sub-clones may persist at very low levels (undetectable even by Deep Sequencing) for long time and then outcompete BCR-ABL1-unmutated ones becoming dominant even in the absence of any TKI selective pressure.

Immunotargeting relapsed or refractory precursor B-cell acute lymphoblastic leukemia - role of blinatumomab

Patients with refractory or relapsed (R/R) acute lymphoblastic leukemia (ALL) have a dismal prognosis of around 5% long-term survival when treated with cytotoxic chemotherapy and allogenic stem cell transplantation. T-cell immunobased strategies open up new therapeutic perspectives. Blinatumomab is the first of a new class of antibody constructs that was labeled bispecific T-cell engager (BiTE): it consists of two single chain variable fragment connected with a flexible linker, one side binding CD3, the other CD19. The tight binding and the close proximity to the CD19-positive B-cells and leukemic cells leads to non-major histocompatibility complex-restricted T-cell activation, polyclonal T-cell expansion and direct target cell killing. Applied by continuous infusion, blinatumomab achieves morphological complete response rates ranging from 39% to 69% in R/R ALL patients (compared to 25% after second-line chemotherapy) with prolonged overall survival (blinatumomab median overall survival, 7.7 months vs chemotherapy, 4.0 months). In comparison to conventional cytotoxic second-line protocols blinatumomab has a favorable safety profile. The main adverse event is related to the mode of action of blinatumomab: the induction of a cytokine-release syndrome that can be managed by interruption and/or the application of steroids or tocilizumab. Another typical complication is the occurrence of neurological side effects, such as seizures and encephalopathy. This neurotoxicity is reversible after application of steroids and/or withdrawal of blinatumomab. Blinatumomab has proven to be a powerful therapeutic option in R/R ALL patients both adult and pediatric because of its efficacy and limited toxicity.

New targeted therapies for relapsed pediatric acute lymphoblastic leukemia

INTRODUCTION

The improvement in outcomes for children with acute lymphoblastic leukemia (ALL) is one of the greatest success stories of modern oncology however the prognosis for patients who relapse remains dismal. Recent discoveries by high resolution genomic technologies have characterized the biology of relapsed leukemia, most notably pathways leading to the drug resistant phenotype. These observations open the possibility of targeting such pathways to prevent and/or treat relapse. Likewise, early experiences with new immunotherapeutic approaches have shown great promise. Areas covered: We performed a literature search on PubMed and recent meeting abstracts using the keywords below. We focused on the biology and clonal evolution of relapsed disease highlighting potential new targets of therapy. We further summarized the results of early trials of the three most prominent immunotherapy agents currently under investigation. Expert commentary: Discovery of targetable pathways that lead to drug resistance and recent breakthroughs in immunotherapy show great promise towards treating this aggressive disease. The best way to treat relapse, however, is to prevent it which makes incorporation of these new approaches into frontline therapy the best approach. Challenges remain to balance efficacy with toxicity and to prevent the emergence of resistant subclones which is why combining these newer agents with conventional chemotherapy will likely become standard of care.

Neurological sequelae of cancer immunotherapies and targeted therapies

Neurological complications of cancer and of anticancer treatments can be substantially disabling to patients, especially with classic chemotherapies. As a rare but important complication, targeted therapies might also result in similar unwanted effects, partly because inhibition of VEGF is a common downstream effect. Therapeutic antibodies, such as the CD20-depleting antibody rituximab, and underlying haematological malignancies, can induce long-lasting cellular immunosuppression, predisposing patients to opportunistic CNS infections, such as progressive multifocal leukoencephalopathy, where treatment-induced recovery can result in severe reconstitution of immune inflammatory syndromes of the central nervous system. Immune-related neurological adverse events, particularly from immune-activating checkpoint inhibitors, occur as a result of immune activation, resulting in organ-specific autoimmune-like disease. The prevalence of immune-related neurological adverse events might only be about 1%-a low prevalence compared with toxicities in other organs-but it constitutes new patterns of neurological toxic forms, which could result in considerable morbidity and fatal outcomes. Clinicians should be aware of treatment-associated neurotoxicity, and consider discontinuation of the drug with parallel supportive measures to help patients.

Drug Discovery Testing Compounds in Patient Samples by Automated Flow Cytometry

Functional ex vivo assays that predict a patient’s clinical response to anticancer drugs for guiding cancer treatment have long been a goal, but few have yet proved to be reliable. To address this, we have developed an automated flow cytometry platform for drug screening that evaluates multiple endpoints with a robust data analysis system that can capture the complex mechanisms of action across different compounds. This system, called PharmaFlow, is used to test peripheral blood or bone marrow samples from patients diagnosed with hematological malignancies. Functional assays that use the whole sample, retaining all the microenvironmental components contained in the sample, offer an approach to ex vivo testing that may give results that are clinically relevant. This new approach can help to predict the patients’ response to existing treatments or to drugs under development, for hematological malignancies or other tumors. In addition, relevant biomarkers can be identified that determine the patient’s sensitivity, resistance, or toxicity to a given treatment. We propose that this approach, which better recapitulates the human microenvironment, constitutes a more predictive assay for personalized medicine and preclinical drug discovery.

Clinical use of blinatumomab for B-cell acute lymphoblastic leukemia in adults

Adults with relapsed or refractory B-cell acute lymphoblastic leukemia have a dismal prognosis with a short median overall survival that can be measured in months. Because most patients will have chemotherapy-resistant disease, allogeneic hematopoietic stem cell transplantation remains the only potentially curative treatment. Despite advances in current management, patients continue to have poor outcomes and lack of durable responses. Thus, new therapies with alternative modes of actions are currently being investigated. Blinatumomab is a novel bispecific T-cell engager that simultaneously binds CD3-positive cytotoxic T-cells and CD19-positive B-cells, resulting in selective lysis of tumor cells. It has shown promising results in patients with relapsed or refractory acute lymphoblastic leukemia or those achieving hematologic response with persistent minimum residual disease. Future clinical trials will answer questions regarding its optimal place in the treatment paradigm. Dose-limiting toxicities include immunological toxicities and cytokine release syndrome. However, most patients tolerate the therapy relatively well. This review will focus on the pharmacology, clinical efficacy, and safety of blinatumomab in the treatment of adult B-cell acute lymphoblastic leukemia while highlighting its unique drug warnings and toxicity management.

Blinatumomab-induced donor T-cell activation for post-stem cell transplant-relapsed acute CD19-positive biphenotypic leukemia

Post-stem cell transplantation (SCT) relapsed acute lymphoblastic leukemia (ALL) has extremely poor prognosis with median survival of less than 1 year. Donor lymphocyte infusion, second transplantation, chemotherapy or cytokine treatment have been tried as a salvage regimen without significant clinical benefit. Recently, blinatumomab, a bispecific monoclonal antibody targeting CD3-expressing T cells and CD19-expressing B-cell lineage malignant cells demonstrated promising outcomes in relapsed/refractory ALL patients. Literature on blinatumomab use in biphenotypic ALL along with Philadelphia chromosome positive (Ph+) ALL is limited. We report a case of post-SCT relapsed CD19 expressing biphenotypic lymphoblastic leukemia patient who achieved complete remission after blinatumomab treatment and has lasting remission for 1 year.

Paving the road ahead for CD19 CAR T-cell therapy

PURPOSE OF REVIEW

Modern immunotherapies, most notably in the form of anti-CD19 chimeric antigen receptor (CAR) T cells, have produced significant clinical responses in otherwise refractory pre-B-cell acute lymphoblastic leukemia patients. Several groups have simultaneously reported robust response rates in children and adults alike. These early studies indicate an impending shift in paradigm for the treatment of acute lymphoblastic leukemia. Incorporating CD19 CAR T-cell therapy into upfront or salvage regimens has its challenges and opportunities.

RECENT FINDINGS

Most CD19 CAR T-cell products in trial today are excellent at inducing minimal residual disease negative remissions, and most responding patients experience cytokine release syndrome and/or neurotoxicity. The challenges facing the CAR community involve how best to minimize the severity of cytokine release syndrome and neurotoxicity while maximizing antitumor efficacy, determining what role this therapy will play for the prophylaxis and treatment of central nervous system leukemia, and its implications on subsequent hematopoietic stem cell transplant given the emergence of CD19-negative relapses.

SUMMARY

CD19 CAR T-cell therapy is a powerful new tool in the oncologist's arsenal. How it is incorporated into standard practice and how it will shift survival curves are the exciting questions that are waiting to be answered.

Potential for bispecific T-cell engagers: role of blinatumomab in acute lymphoblastic leukemia

Patients with relapsed/refractory (R/R) B-precursor acute lymphoblastic leukemia (ALL) and patients whose minimal residual disease persists during treatment have a poor leukemia-free survival. Despite improvements in front-line therapy, the outcome in these patients remains poor, especially after relapse. As there are no standard chemotherapeutic regimens for the treatment of patients with R/R B-precursor ALL, T-cell-based therapeutic approaches have recently come to the forefront in ALL therapy. Recently, monoclonal antibodies have been developed to target specific antigens expressed in B-lineage blast cells. In this setting, CD19 is of great interest as this antigen is expressed in B-lineage cells. Therefore, it has been selected as the target antigen for blinatumomab, a new bi-specific T-cell engager antibody. This sophisticated antibody binds sites for both CD19 and CD3, leading to T-cell proliferation and activation and B-cell apoptosis. Owing to its short serum half-life, blinatumomab has been administrated by continuous intravenous infusion with a favorable safety profile. The most significant toxicities were central nervous system events and the cytokine release syndrome. This new therapeutic approach using blinatumomab has been shown to be effective in patients with positive minimal residual disease and in patients with R/R B-precursor ALL leading to a recent approval by the US Food and Drug Administration after an accelerated review process. This review focuses on the profile of blinatumomab and its efficacy and safety.