Advances in the treatment of hematologic malignancies using immunoconjugates

Post-column denaturation-assisted hydrophobic interaction chromatography-mass spectrometry for rapid and in-depth characterization of positional isomers in cysteine-based antibody-drug conjugates

Antibody-drug conjugates (ADCs) represent a significant advancement in targeted cancer therapy, offering the potential to selectively deliver cytotoxic drugs to tumor cells while minimizing systemic toxicity. However, the structural complexity of ADCs, particularly those conjugated through cysteine residues, poses significant analytical challenges. Due to the hydrophobicity of ADCs, Hydrophobic interaction chromatography (HIC) is often the method of choice to analyze the drug-to-antibody ratio (DAR). However, it requires high-concentration salts, which are often incompatible with mass spectrometry (MS) analysis. By employing ammonium acetate as an MS-compatible salt and integrating a 4-way liquid junction cross configuration for simultaneous introduction of the makeup flow and splitting the flow right before coupling to a mass spectrometer, we achieve high-quality separation and sensitive mass spectrometric analysis. This innovative setup allows for simultaneous DAR measurement and positional isomer characterization by switching the makeup flow solvent from water to a denaturation solution. Our method offers a streamlined and effective approach to ADC characterization, facilitating the identification of positional isomers without the need for fractionation or multiple chromatographic steps. The versatility and robustness of this HIC-MS method are demonstrated through the analysis of two ADCs, highlighting its potential for broad application in ADC development and quality control.

Geriatric nutritional risk index as a predictor of prognosis in hematologic malignancies: a systematic review and meta-analysis

Objective

Recent studies have reported inconsistent results regarding the association between geriatric nutritional risk index (GNRI) and clinical outcomes in patients with hematologic malignancies (HMs). We performed a meta-analysis to evaluate the effect of low GNRI on the overall survival (OS) and progression-free survival (PFS) in patients with HMs.

Research Methods and Procedures

We conducted the research via PubMed, Embase, and Cochrane Library databases to identify trials. Exploring the association between GNRI and prognosis in patients with HMs. A meta-analysis of OS and PFS was performed. Quality In Prognostic Studies instrument and Newcastle-Ottawa quality assessment Scale were used to assess the quality of included trials.

Results

Fourteen studies enrolling 3,524 patients with HMs were included. Low GNRI was associated with shorter OS (Hazard ratio (HR) = 1.77; 95% CI = 1.44-2.18, p < 0.01) and PFS (HR = 1.63; 95% CI = 1.17-2.27, p < 0.01) in patients with HMs. In the subgroup analysis, GNRI was not significantly associated with prognosis in Chinese patients with HMs (OS, HR =1.33; 95% CI = 0.89-1.98, p = 0.16; PFS, HR = 1.70; 95% CI = 0.72-4.01, p = 0.23). For the subgroup with a GNRI cutoff value less than 98, there was no significant difference in PFS (HR = 1.34; 95% CI = 0.98-1.83, p = 0.06).

Conclusion

Low GNRI negatively impacted on the prognosis in patients with HMs. Prospective studies to identify the best cut-off value for GNRI are required.

Theranostic Potentials of Gold Nanomaterials in Hematological Malignancies

Simple Summary

Hematological malignancies (HMs) cover 50% of all malignancies, and people of all ages can be affected by these deadly diseases. In many cases, conventional diagnostic tools fail to diagnose HMs at an early stage, due to heterogeneity and the long-term indolent phase of HMs. Therefore, many patients start their treatment at the late stage of HMs and have poor survival. Gold nanomaterials (GNMs) have shown promise as a cancer theranostic agent. GNMs are 1 nm to 100 nm materials having magnetic resonance and surface-plasmon-resonance properties. GNMs conjugated with antibodies, nucleic acids, peptides, photosensitizers, chemotherapeutic drugs, synthetic-drug candidates, bioactive compounds, and other theranostic biomolecules may enhance the efficacy and efficiency of both traditional and advanced theranostic approaches to combat HMs.

Abstract

Hematological malignancies (HMs) are a heterogeneous group of blood neoplasia generally characterized by abnormal blood-cell production. Detection of HMs-specific molecular biomarkers (e.g., surface antigens, nucleic acid, and proteomic biomarkers) is crucial in determining clinical states and monitoring disease progression. Early diagnosis of HMs, followed by an effective treatment, can remarkably extend overall survival of patients. However, traditional and advanced HMs’ diagnostic strategies still lack selectivity and sensitivity. More importantly, commercially available chemotherapeutic drugs are losing their efficacy due to adverse effects, and many patients develop resistance against these drugs. To overcome these limitations, the development of novel potent and reliable theranostic agents is urgently needed to diagnose and combat HMs at an early stage. Recently, gold nanomaterials (GNMs) have shown promise in the diagnosis and treatment of HMs. Magnetic resonance and the surface-plasmon-resonance properties of GNMs have made them a suitable candidate in the diagnosis of HMs via magnetic-resonance imaging and colorimetric or electrochemical sensing of cancer-specific biomarkers. Furthermore, GNMs-based photodynamic therapy, photothermal therapy, radiation therapy, and targeted drug delivery enhanced the selectivity and efficacy of anticancer drugs or drug candidates. Therefore, surface-tuned GNMs could be used as sensitive, reliable, and accurate early HMs, metastatic HMs, and MRD-detection tools, as well as selective, potent anticancer agents. However, GNMs may induce endothelial leakage to exacerbate cancer metastasis. Studies using clinical patient samples, patient-derived HMs models, or healthy-animal models could give a precise idea about their theranostic potential as well as biocompatibility. The present review will investigate the theranostic potential of vectorized GNMs in HMs and future challenges before clinical theranostic applications in HMs.

Monoclonal antibodies used for the management of haematological disorders

INTRODUCTION

Monoclonal antibodies Ab (MoAb) are increasingly becoming part of therapeutic armamentarium for haematologists and haemato-oncologists. This review brings together commonly used antibodies in one place for brevity and novel understanding.

AREAS COVERED

Pubmed and Scopus databases were explored focusing on MoAb in clinical haematological practice. Emphasis was given to current review articles. The data base was searched from 1997 till present. 24 different antibodies, most of which are in use were discussed. Antibodies are used for diverse conditions i.e. malignant and benign haematological conditions, treatment at various phases of stem cell transplantation. These antibodies were used both alone or in combination with various chemotherapy, targeted small molecules or as immunoconjugates. Some of the side effect profiles of these antibodies were common and some were unique. Unusual infections or organ dysfunctions were noted. Improved function of antibodies by protein engineering is also advancing rapidly. Dosage, frequency and route of administration depended on the convenience and condition for which the antibody is used.

EXPERT OPINION

: MoAbs are increasingly used in haematology practice either alone or in combination with other types of therapy for improved out come in various haematological conditions.

Potent anti-tumor activity of CD45RA-targeting Hm3A4-Ranpirnase against myeloid lineage leukemias

CD45RA is a specific marker for leukemia stem cell (LSC) sub-populations in acute myeloid leukemia (AML). Ranpirnase (Rap), an amphibian RNase, has been extensively investigated in preclinical and clinical studies for its antitumor activity. Rap could be administered repeatedly to patients without inducing an immune response. Reversible renal toxicity has been reported to be dose-limiting. In this study, we generated a novel immunotoxin targeting LSCs: Hm3A4-Rap, which was composed of Rap and Hm3A4, a human-mouse chimeric antibody against CD45RA. This immunotoxin was generated recombinantly by fusing Rap to Hm3A4 at the Fc terminus and then produced by stably transfecting CHO cells. The immunotoxin was purified using Ni-NTA and then evaluated using RT-PCR, SDS-PAGE, antibody titer assays, competitive inhibition assays, and internalization assays. In addition, the purity, molecular integrity, and affinity to the CD45RA antigen were determined. In vitro studies demonstrated that Hm3A4-Rap could efficiently kill target cells. In vivo studies demonstrated that Hm3A4-Rap had potent anti-leukemia activity, with dosed mice showing a significant increase in survival time compared to control mice (P < 0.01). In summary, our immunotoxin had excellent biological activity suggesting its potential therapeutic value for treating AML patients. Additional preclinical and clinical studies are needed to develop this immunotoxin as a treatment option for patients with leukemia.

CD146 is a potential immunotarget for neuroblastoma

Neuroblastoma, the most common extracranial solid tumor of childhood, is thought to arise from neural crest‐derived immature cells. The prognosis of patients with high‐risk or recurrent/refractory neuroblastoma remains quite poor despite intensive multimodality therapy; therefore, novel therapeutic interventions are required. We examined the expression of a cell adhesion molecule CD146 (melanoma cell adhesion molecule [MCAM]) by neuroblastoma cell lines and in clinical samples and investigated the anti‐tumor effects of CD146‐targeting treatment for neuroblastoma cells both in vitro and in vivo. CD146 is expressed by 4 cell lines and by most of primary tumors at any stage. Short hairpin RNA‐mediated knockdown of CD146, or treatment with an anti‐CD146 polyclonal antibody, effectively inhibited growth of neuroblastoma cells both in vitro and in vivo, principally due to increased apoptosis via the focal adhesion kinase and/or nuclear factor‐kappa B signaling pathway. Furthermore, the anti‐CD146 polyclonal antibody markedly inhibited tumor growth in immunodeficient mice inoculated with primary neuroblastoma cells. In conclusion, CD146 represents a promising therapeutic target for neuroblastoma.

Plant-made immunotoxin building blocks: A roadmap for producing therapeutic antibody-toxin fusions

Molecular farming in plants is an emerging platform for the production of pharmaceutical proteins, and host species such as tobacco are now becoming competitive with commercially established production hosts based on bacteria and mammalian cell lines. The range of recombinant therapeutic proteins produced in plants includes replacement enzymes, vaccines and monoclonal antibodies (mAbs). But plants can also be used to manufacture toxins, such as the mistletoe lectin viscumin, providing an opportunity to express active antibody-toxin fusion proteins, so-called recombinant immunotoxins (RITs). Mammalian production systems are currently used to produce antibody-drug conjugates (ADCs), which require the separate expression and purification of each component followed by a complex and hazardous coupling procedure. In contrast, RITs made in plants are expressed in a single step and could therefore reduce production and purification costs. The costs can be reduced further if subcellular compartments that accumulate large quantities of the stable protein are identified and optimal plant growth conditions are selected. In this review, we first provide an overview of the current state of RIT production in plants before discussing the three key components of RITs in detail. The specificity-defining domain (often an antibody) binds cancer cells, including solid tumors and hematological malignancies. The toxin provides the means to kill target cells. Toxins from different species with different modes of action can be used for this purpose. Finally, the linker spaces the two other components to ensure they adopt a stable, functional conformation, and may also promote toxin release inside the cell. Given the diversity of these components, we extract broad principles that can be used as recommendations for the development of effective RITs. Future research should focus on such proteins to exploit the advantages of plants as efficient production platforms for targeted anti-cancer therapeutics.

Tissue Factor-Targeted ImmunoPET Imaging and Radioimmunotherapy of Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is the most aggressive subtype of thyroid cancers with a dismal prognosis. It is aimed to explore a new biomarker and devise a marker-dependent theranostic pair for ATC. Flow cytometry is used to determine tissue factor (TF) expression in thyroid cancer cell lines. ALT-836, a TF-specific monoclonal antibody, is radiolabeled with 64Cu to develop 64Cu-NOTA-ALT-836. The diagnostic utility is assessed by immuno-positron emission tomography (immunoPET) imaging in ATC models. To facilitate total surgical removal of orthotopic ATCs, a near-infrared fluorescent imaging probe IRDye 800CW-ALT-836 is designed. As the therapeutic component, 131I-ALT-836 is further developed and the radioimmunotherapy (RIT) efficacy of this agent is interrogated in orthotopic ATC models. The results demonstrate that TF is highly expressed on the ATC cell line THJ-16T. 64Cu-NOTA-ALT-836 immunoPET imaging clearly delineates both subcutaneous and orthotopic ATCs, with a peak tumor uptake of 19.93 ± 2.17% ID per g (n = 3) and 37.20 ± 1.71% ID per g (n = 3), respectively. Fluorescent imaging with IRDye 800CW-ALT-836 facilitates the total resection of orthotopic ATCs. Moreover, 131I-ALT-836 RIT prolongs the survival of ATC-bearing mice. Taken together, TF is a promising marker for ATC and successive use of 64Cu-NOTA-ALT-836 and 131I-ALT-836 can realize precise management of ATC.

Tofacitinib enhances delivery of antibody-based therapeutics to tumor cells through modulation of inflammatory cells

The routes by which antibody-based therapeutics reach malignant cells are poorly defined. Tofacitinib, an FDA-approved JAK inhibitor, reduced tumor-associated inflammatory cells and allowed increased delivery of antibody-based agents to malignant cells. Alone, tofacitinib exhibited no antitumor activity, but combinations with immunotoxins or an antibody-drug conjugate resulted in increased antitumor responses. Quantification using flow cytometry revealed that antibody-based agents accumulated in malignant cells at higher percentages following tofacitinib treatment. Profiling of tofacitinib-treated tumor-bearing mice indicated that cytokine transcripts and various proteins involved in chemotaxis were reduced compared with vehicle-treated mice. Histological analysis revealed significant changes to the composition of the tumor microenvironment, with reductions in monocytes, macrophages, and neutrophils. Tumor-associated inflammatory cells contributed to non-target uptake of antibody-based therapeutics, with mice treated with tofacitinib showing decreased accumulation of therapeutics in intratumoral inflammatory cells and increased delivery to malignant cells. The present findings serve as a rationale for conducting trials where short-term treatments with tofacitinib could be administered in combination with antibody-based therapies.

Predictors of outcome in patients with hematologic malignancies admitted to the intensive care unit

PURPOSE

Several studies showed conflicting results about prognosis and predictors of outcome of critically ill patients with hematological malignancies (HM). The aim of this study is to determine the hospital outcome of critically ill patients with HM and the factors predicting the outcome.

METHODS AND MATERIALS

All patients with HM admitted to MICU at a tertiary academic medical center were enrolled. Clinical data upon admission and during ICU stay were collected. Hospital, ICU, and 6 months outcomes were documented.

RESULTS

There were 130 HM patients during the study period. Acute Leukemia was the most common malignancy (31.5%) followed by Non-Hodgkin's Lymphoma (28.5%). About 12.5% patients had autologous HSCT and 51.5% had allogeneic HSCT. Sepsis was the most common ICU diagnosis (25.9%). ICU mortality and hospital mortality were 24.8% and 45.3%, respectively. Six months mortality (available on 80% of patients) was 56.7%. Hospital mortality was higher among mechanically ventilated patients (75%). Using multivariate analysis, only mechanical ventilation (OR of 19.0, CI: 3.1-117.4, P: 0.001) and allogeneic HSCT (OR of 10.9, CI: 1.8-66.9, P: 0.01) predicted hospital mortality.

CONCLUSION

Overall hospital outcome of critically ill patients with HM is improving. However those who require mechanical ventilation or underwent allogeneic HSCT continue to have poor outcome.

Investigational therapies targeting CD37 for the treatment of B-cell lymphoid malignancies

INTRODUCTION

While chemotherapy still remains a cornerstone of oncologic therapy, immunotherapy with monoclonal antibodies has steadily improved the treatment strategy for several hematologic malignancies. New treatment options need to be developed for relapsed and refractory non-Hodgkin lymphoma (NHL) patients. Currently, novel agents targeting specific molecules on the surface of lymphoma cells, such as anti-CD37 antibodies, are under considerable investigation. Here we report on anti-CD37 targeting for the treatment of patients with B-cell NHL.

AREAS COVERED

CD37 seems to be the perfect therapeutic target in patients with NHL. The CD37 antigen is abundantly expressed in B-cells, but is absent on normal stem cells and plasma cells. It is hoped that anti-CD37 monoclonal antibodies will increase the efficacy and reduce toxicity in patients with both newly diagnosed and relapsed and refractory disease. Recent clinical trials have shown promising outcomes for these agents, administered both as monotherapy and in combination with standard chemotherapeutics.

EXPERT OPINION

The development of new therapeutic options might help to avoid cytotoxic chemotherapy entirely in some clinical settings. This article presents the latest state of the art on the new treatment strategies in NHL patients. It also discusses recently approved agents and available clinical trial data.

A novel approach for medical research on lymphomas: A study validation of claims-based algorithms to identify incident cases

The use of claims database to study lymphomas in real-life conditions is a crucial issue in the future. In this way, it is essential to develop validated algorithms for the identification of lymphomas in these databases. The aim of this study was to assess the validity of diagnosis codes in the French health insurance database to identify incident cases of lymphomas according to results of a regional cancer registry, as the gold standard.Between 2010 and 2013, incident lymphomas were identified in hospital data through 2 algorithms of selection. The results of the identification process and characteristics of incident lymphomas cases were compared with data from the Tarn Cancer Registry. Each algorithm's performance was assessed by estimating sensitivity, predictive positive value, specificity (SPE), and negative predictive value.During the period, the registry recorded 476 incident cases of lymphomas, of which 52 were Hodgkin lymphomas and 424 non-Hodgkin lymphomas. For corresponding area and period, algorithm 1 provides a number of incident cases close to the Registry, whereas algorithm 2 overestimated the number of incident cases by approximately 30%. Both algorithms were highly specific (SPE = 99.9%) but moderately sensitive. The comparative analysis illustrates that similar distribution and characteristics are observed in both sources.Given these findings, the use of claims database can be consider as a pertinent and powerful tool to conduct medico-economic or pharmacoepidemiological studies in lymphomas.

The emerging role of anti-CD25 directed therapies as both immune modulators and targeted agents in cancer

CD25 (also termed IL2RA) forms one component of the high-affinity heterotrimeric interleukin 2 (IL2) receptor on activated T cells. Its affinity for IL2 and cellular function are tightly regulated and vary in different cell types. The high frequency of CD25 on the surface of many different haematological tumour cells is now well established and, apart from its prognostic significance, CD25 may be present on leukaemic stem cells and enable oncogenic signalling pathways in leukaemic cells. Additionally, high CD25 expression in activated circulating immune cells and Tregs is a factor that has already been exploited by IL2 immunotherapies for treatment of tumours and autoimmune disease. The relative clinical safety and efficacy of administering anti-CD25 radioimmunoconjugates and immunotoxins in various haematological tumour indications has been established and clinical trials of a novel CD25-directed antibody drug conjugate are underway.

Trial Watch: Adoptively transferred cells for anticancer immunotherapy

Immunotherapies aimed at strengthening immune effector responses against malignant cells are growing at exponential rates. Alongside, the impressive benefits obtained by patients with advanced melanoma who received adoptively transferred tumor-infiltrating lymphocytes (TILs) have encouraged the scientific community to pursue adoptive cell transfer (ACT)-based immunotherapy. ACT involves autologous or allogenic effector lymphocytes that are generally obtained from the peripheral blood or resected tumors, expanded and activated ex vivo, and administered to lymphodepleted patients. ACT may be optionally associated with chemo- and/or immunotherapeutics, with the overall aim of enhancing the proliferation, persistence and functionality of infused cells, as well as to ensure their evolution in an immunological permissive local and systemic microenvironment. In addition, isolated lymphocytes can be genetically engineered to endow them with the ability to target a specific tumor-associated antigen (TAA), to increase their lifespan, and/or to reduce their potential toxicity. The infusion of chimeric antigen receptor (CAR)-expressing cytotoxic T lymphocytes redirected against CD19 has shown promising clinical efficacy in patients with B-cell malignancies. Accordingly, the US Food and Drug Administration (FDA) has recently granted 'breakthrough therapy' designation to a CAR-based T-cell therapy (CTL019) for patients with B-cell malignancies. Considerable efforts are now being devoted to the development of efficient ACT-based immunotherapies for non-hematological neoplasms. In this Trial Watch, we summarize recent clinical advances on the use of ACT for oncological indications.

Immunotherapy for the treatment of Hodgkin lymphoma

INTRODUCTION

Most patients with Hodgkin lymphoma (HL) enjoy durable remissions following front-line treatment but 30% of patients are refractory or relapse after first line therapy. Salvage chemotherapy followed by autologous stem cell transplantation (ASCT) can cure an additional 50-55% of relapsing patients but new treatments are needed for patients with HL who are refractory or relapse after ASCT. Immunotherapy has emerged as a promising treatment for the management of these patients. The availability of the anti-CD30 antibody brentuximab vedotin and new targeted drugs such as immune checkpoint inhibitors, show promising clinical activity in patients with HL and are important milestones for the management of patients with HL particularly for those who have progressed after standard initial therapy and ASCT. Areas covered: Overview of the results from the most relevant clinical trials including monoclonal antibody-based therapy in HL. Phase 2 and phase 3 trials including brentuximab vedotin and immune checkpoints inhibitors in patients with Hodgkin lymphoma have been reviewed. In addition, the potential impact of these new therapies in the management of patients with newly diagnosed HL has also been addressed. Expert commentary: Anti-CD30 antibody brentuximab vedotin and immune checkpoint inhibitors have shown promising results in patients with relapsed and refractory HL. Administration of these therapies earlier in the course of the disease might reduce the proportion of relapsed or refractory patients and, subsequently, minimize the number of patients undergoing high-dose therapy and autologous stem cell transplantation. We have little doubt that this will have substantial effects on the outcome for future generations of HL patients.

Preclinical Activity of the Novel Anti-Prolactin Receptor (PRLR) Antibody-Drug Conjugate REGN2878-DM1 in PRLR-Positive Breast Cancers

The Prolactin Receptor (PRLR) is a type 1 cytokine receptor that is expressed in a subset of breast cancers and may contribute to its pathogenesis. It is relatively overexpressed in approximately 25% of human breast tumors while expressed at low levels in some normal human tissues including the mammary gland. We developed an anti-PRLR antibody-drug conjugate (ADC), to target PRLR-positive breast cancer. REGN2878-DM1 is comprised of a fully human high-affinity function-blocking anti-PRLR IgG1 antibody (REGN2878) conjugated via a noncleavable SMCC linker to the cytotoxic maytansine derivative DM1. Both unconjugated REGN2878 and conjugated REGN2878-DM1 block PRL-mediated activation in vitro and are rapidly internalized into lysosomes. REGN2878-DM1 induces potent cell-cycle arrest and cytotoxicity in PRLR-expressing tumor cell lines. In vivo, REGN2878-DM1 demonstrated significant antigen-specific antitumor activity against breast cancer xenograft models. In addition, REGN2878-DM1 showed additive activity when combined with the antiestrogen agent fulvestrant. These results illustrate promising antitumor activity against PRLR-positive breast cancer xenografts and support the evaluation of anti-PRLR ADCs as potential therapeutic agents in breast cancer. Mol Cancer Ther; 16(7); 1299-311. ©2017 AACR.

Novel agents in follicular lymphoma: choosing the best target

Outcomes in patients with follicular lymphoma (FL) have improved dramatically over the last decade. However, novel agents are greatly needed for those who exhibit treatment resistance, in order to minimize lifelong toxicity and to enable combinations that may allow us to achieve the elusive goal of cure. Biological advances have led to the discovery of a large number of potential therapeutic targets and the development of a plethora of novel agents designed to exploit these processes. Possible targets include tumor cell surface markers, key components of intracellular pathways and epigenetic mechanisms, and reactive cells of the microenvironment. Given the large number of candidate drugs and potential combinations, it will be crucial to prioritize evaluation based on sound preclinical and early clinical studies. Combinations that exploit driver mechanisms within tumor cells and target parallel pathways to minimize the development of drug resistance, as well as harness the potential of the immune system would seem most logical. In order to expedite progress, future studies will need to use innovative trial designs and employ surrogate end points. The development of validated prognostic tools to identify higher risk patients and reliable predictive markers to select subgroups most likely to benefit from targeted agents will be paramount. The potential for unexpected toxicity with novel combinations must be recognized, necessitating both short- and long-term vigilance. Finally, as a greater number of treatment options become available, optimal sequencing must be determined in order to both prolong life and maintain its quality.

Anti-CD20 antibody treatment of non-Hodgkin lymphomas

The CD20 antigen characteristic for mature B-cell is also expressed on B-cell Non-Hodgkin lymphomas (NHL). It thus presents a possible target for immunotherapy. NHL respond readily to radio- and/or chemotherapy but this standard treatment bears a high risk of relapse. The specific monoclonal anti-CD20-antibody Rituximab, the first to be approved for clinical use, could be shown to improve response rates, response duration, and survival in NHL when combined with standard therapy. This review details the development, clinical application, and future perspectives of anti-CD20-antibody treatment of NHL, thereby proving the efficiency of immunotherapy via targeting of a tumor associated antigen.

(211)Astatine-Conjugated Monoclonal CD45 Antibody-Based Nonmyeloablative Conditioning for Stem Cell Gene Therapy

Most hematopoietic stem cell gene therapy studies require host conditioning to allow for efficient engraftment of gene-modified cells. Conditioning regimens with lower treatment-related toxicities are especially relevant for the treatment of nonmalignant blood disorders, such as hemoglobinopathies and immunodeficiencies, and for patients who are otherwise ineligible for conventional high-dose conditioning. Radioimmunotherapy, which employs an α- or a β-emitting radionuclide conjugated to a targeting antibody, is effective for delivering cytotoxic doses of radiation to a cell type of interest while minimizing off-target toxicity. Here, we demonstrate the feasibility of using a nonmyeloablative dose of a monoclonal anti-CD45 antibody conjugated to the α-emitter Astatine-211 ((211)At) to promote engraftment of an autologous gene-modified stem cell graft in the canine model. The doses used provided myelosuppression with rapid autologous recovery and minimal off-target toxicity. Engraftment levels were low in all dogs and reflected the low numbers of gene-modified cells infused. Our data suggest that a cell dose exceeding 1×10(6) cells/kg be used with nonmyeloablative doses of (211)At-anti-CD45 monoclonal antibodies for sustained engraftment in the dog model.

A rapid on-line method for mass spectrometric confirmation of a cysteine-conjugated antibody-drug-conjugate structure using multidimensional chromatography

Cysteine-conjugated antibody-drug conjugates (ADCs) are manufactured using controlled partial reduction and conjugation chemistry with drug payloads that typically occur in intervals of 0, 2, 4, 6, and 8. Control of heterogeneity is of particular importance to the quality of ADC product because drug loading and distribution can affect the safety and efficacy of the ADC. Liquid chromatography ultra-violet (LC-UV)-based methods can be used to acquire the drug distribution profiles of cysteine-conjugated ADCs when analyzed using hydrophobic interaction chromatography (HIC). However, alternative analysis techniques are often required for structural identification when conjugated drugs do not possess discrete ultra-violet absorbance properties for precise assessment of the drug-to-antibody ratio (DAR). In this study, multidimensional chromatography was used as an efficient method for combining non-compatible techniques, such as HIC, with analysis by mass spectrometry (LC/LC/QTOF-MS) for rapid on-line structural elucidation of species observed in HIC distribution profiles of cysteine-conjugated ADCs. The methodology was tested using an IgG1 mAb modified by cysteine conjugation with a non-toxic drug mimic. Structural elucidation of peaks observed in the HIC analysis (1^st dimension) were successfully identified based on their unique sub-unit masses via mass spectrometry techniques once dissociation occurred under denaturing reversed phase conditions (2^nd dimension). Upon identification, the DAR values were determined to be 2.83, 4.44, and 5.97 for 3 drug load levels (low-, medium-, and high-loaded ADC batches), respectively, based on relative abundance from the LC-UV data. This work demonstrates that multidimensional chromatography coupled with MS, provides an efficient approach for on-line biotherapeutic characterization to ensure ADC product quality.

Are we nearing an era of chemotherapy-free management of indolent lymphoma?

Indolent B-cell lymphomas are heterogeneous, comprising three grades of follicular lymphoma, small lymphocytic lymphoma, Waldenstöm macroglobulinemia, marginal zone lymphoma, and most recently, possibly low proliferative mantle cell lymphoma. These lymphomas are characterized by a high responsiveness to chemotherapy or immunochemotherapy; however, in most cases, conventional therapy might not offer a cure. Furthermore, the patient's age at diagnosis, at time to first or subsequent relapses, as well as potential comorbidities often preclude the use of chemotherapy. Recent progress has been made in our understanding of dysregulated pathways and immunologic antitumor responses in indolent lymphoma. Major therapeutic advances have been achieved in the development of nonchemotherapeutic agents, making "chemo-free" treatment a near-future reality. In this article, we highlight these promising approaches, such as the combination of anti-CD20 antibodies with immunomodulatory drugs, with mAbs directed against other surface antigens such as CD22, with immunomodulatory antibodies such as PD-1, or with inhibitors of key steps in the B-cell receptor pathway signaling. However, the cost of such therapies and potential, albeit manageable, toxicity should be considered. Phase III trials will confirm the benefit of these new treatment strategies that do not require a chemotherapeutic drug and help us identify their exact place in the therapeutic armamentarium for indolent lymphoma. Here we focus on follicular lymphoma, which is the most frequent subtype of indolent lymphoma and for which an increasing body of evidence has emerged that supports the dawn of a new era of chemotherapy-free treatment. See all articles in this CCR Focus section, "Paradigm Shifts in Lymphoma."

AGS67E, an Anti-CD37 Monomethyl Auristatin E Antibody-Drug Conjugate as a Potential Therapeutic for B/T-Cell Malignancies and AML: A New Role for CD37 in AML

CD37 is a tetraspanin expressed on malignant B cells. Recently, CD37 has gained interest as a therapeutic target. We developed AGS67E, an antibody-drug conjugate that targets CD37 for the potential treatment of B/T-cell malignancies. It is a fully human monoclonal IgG2 antibody (AGS67C) conjugated, via a protease-cleavable linker, to the microtubule-disrupting agent monomethyl auristatin E (MMAE). AGS67E induces potent cytotoxicity, apoptosis, and cell-cycle alterations in many non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) cell lines and patient-derived samples in vitro. It also shows potent antitumor activity in NHL and CLL xenografts, including Rituxan-refractory models. During profiling studies to confirm the reported expression of CD37 in normal tissues and B-cell malignancies, we made the novel discovery that the CD37 protein was expressed in T-cell lymphomas and in AML. AGS67E bound to >80% of NHL and T-cell lymphomas, 100% of CLL and 100% of AML patient-derived samples, including CD34(+)CD38(-) leukemic stem cells. It also induced cytotoxicity, apoptosis, and cell-cycle alterations in AML cell lines and antitumor efficacy in orthotopic AML xenografts. Taken together, this study shows not only that AGS67E may serve as a potential therapeutic for B/T-cell malignancies, but it also demonstrates, for the first time, that CD37 is well expressed and a potential drug target in AML.

Whole-genome RNAi screen highlights components of the endoplasmic reticulum/Golgi as a source of resistance to immunotoxin-mediated cytotoxicity

Immunotoxins (antibody-toxin fusion proteins) target surface antigens on cancer cells and kill these cells via toxin-mediated inhibition of protein synthesis. To identify genes controlling this process, an RNAi whole-genome screen (∼ 22,000 genes at three siRNAs per gene) was conducted via monitoring the cytotoxicity of the mesothelin-directed immunotoxin SS1P. SS1P, a Pseudomonas exotoxin-based immunotoxin, was chosen because it is now in clinical trials and has produced objective tumor regressions in patients. High and low concentrations of SS1P were chosen to allow for the identification of both mitigators and sensitizers. As expected, silencing known essential genes in the immunotoxin pathway, such as mesothelin, furin, KDEL receptor 2, or members of the diphthamide pathway, protected cells. Of greater interest was the observation that many RNAi targets increased immunotoxin sensitivity, indicating that these gene products normally contribute to inefficiencies in the killing pathway. Of the top sensitizers, many genes encode proteins that locate to either the endoplasmic reticulum (ER) or Golgi and are annotated as part of the secretory system. Genes related to the ER-associated degradation system were not among high-ranking mitigator or sensitizer candidates. However, the p97 inhibitor eeyarestatin 1 enhanced immunotoxin killing. Our results highlight potential targets for chemical intervention that could increase immunotoxin killing of cancer cells and enhance our understanding of toxin trafficking.

Structure-based design of a streptavidin mutant specific for an artificial biotin analogue

For a multistep pre-targeting method using antibodies, a streptavidin mutant with low immunogenicity, termed low immunogenic streptavidin mutant No. 314 (LISA-314), was produced previously as a drug delivery tool. However, endogenous biotins (BTNs) with high affinity (Kd < 10(-10) M) for the binding pocket of LISA-314 prevents access of exogenous BTN-labelled anticancer drugs. In this study, we improve the binding pocket of LISA-314 to abolish its affinity for endogenous BTN species, therefore ensuring that the newly designed LISA-314 binds only artificial BTN analogue. The replacement of three amino acid residues was performed in two steps to develop a mutant termed V212, which selectively binds to 6-(5-((3aS,4S,6aR)-2-iminohexahydro-1H-thieno[3,4-d]imidazol-4-yl)pentanamido)hexanoic acid (iminobiotin long tail, IMNtail). Surface plasmon resonance results showed that V212 has a Kd value of 5.9 × 10(-7) M towards IMNtail, but no binding affinity for endogenous BTN species. This V212/IMNtail system will be useful as a novel delivery tool for anticancer therapy.

Antigen-armed antibodies targeting B lymphoma cells effectively activate antigen-specific CD4+ T cells

The treatment of non-Hodgkin lymphomas has benefited enormously from the introduction of monoclonal antibody-based therapies. However, the efficacy of these treatments varies with lymphoma subtypes and typically decreases with subsequent relapses. Here, we report on antigen-armed antibodies (AgAbs) as a potential treatment of B-cell lymphoma. AgAbs include antigens from ubiquitous pathogens, such as Epstein-Barr virus (EBV), that persist in their host and elicit strong lifelong T-cell responses. They act as vectors by introducing antigen directly into tumor cells to induce an antigen-specific CD4(+) T-cell response against these cells. We have fused antibodies targeting human B-cell surface receptors (CD19-22) to immunodominant T-cell antigens from EBV proteins, including EBNA1, EBNA3B, and EBNA3C. Exposure of EBV-transformed B cells and of Burkitt lymphoma cells to AgAbs led to antigen presentation, T-cell recognition, and target cell killing. The efficiency of AgAb action paralleled the abundance of the targeted molecules on lymphoma cells as well as their HLA class II expression levels. AgAbs can also induce activation and proliferation of EBV-specific memory CD4(+) T cells ex vivo. These studies show the potential of AgAbs as an effective therapeutic strategy against B-cell lymphomas.

Structure-based design and synthesis of a bivalent iminobiotin analog showing strong affinity toward a low immunogenic streptavidin mutant

The streptavidin/biotin interaction has been widely used as a useful tool in research fields. For application to a pre-targeting system, we previously developed a streptavidin mutant that binds to an iminobiotin analog while abolishing affinity for natural biocytin. Here, we design a bivalent iminobiotin analog that shows 1000-fold higher affinity than before, and determine its crystal structure complexed with the mutant protein.

Diffuse large B-cell lymphoma: optimizing outcome in the context of clinical and biologic heterogeneity

Although the majority of patients with diffuse large B-cell lymphoma (DLBCL) can be cured with standard rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), patients who fail R-CHOP have a dismal outcome. Thus, optimization of front-line therapy, as well as the development of more effective salvage strategies, remains an important objective. Advances in molecular genetics have vastly improved our understanding of the biological diversity of DLBCL and have led to the discovery of key oncogenic pathways. In addition to the major molecular designations of germinal center B-cell and activated B-cell subtypes, next-generation sequencing technologies have unveiled the remarkable complexity of DLBCL and identified unique molecular targets that may be differentially exploited for therapeutic benefit. These findings have translated into a growing list of promising novel agents. Moving forward, it is of paramount importance to recognize the heterogeneity of DLBCL and to investigate these targeted agents within patient populations who are most likely to benefit. It will be necessary to prioritize drugs that affect key driver pathways and to combine them rationally to optimize their benefit. Improved prognostication and the availability of predictive biomarkers will be crucial to allow for the possibility of individualized risk-adapted therapy.

Antigen-specific immunotherapies for acute myeloid leukemia

Antigen-specific immunotherapies have emerged as important components of curative treatment algorithms for many cancers. In acute myeloid leukemia (AML), success has been less obvious. Nonetheless, among the few drugs shown to improve survival in recent randomized trials is the CD33 antibody-drug conjugate gemtuzumab ozogamicin. Significant antileukemic activity is also well documented for radioimmunoconjugates targeting CD33, CD45, or CD66. These therapeutics can intensify conditioning before hematopoietic cell transplantation, but their effect on patient outcomes needs clarification. Emerging data now suggest clinical antileukemic activity of several novel antibodies and perhaps some adoptive T-cell immunotherapies and vaccines. In parallel, numerous other agents targeting a wider variety of antigens are currently being explored. However, the antigenic heterogeneity characteristic of AML is a considerable limitation for all these therapeutics, and many important questions related to the ideal target antigen(s), disease situation in which to use these therapies, most suitable patient populations, exact treatment modalities, and details of supportive care needs remain open. Addressing such questions in upcoming studies will be required to ensure that antigen-directed therapies become an effective tool in AML, a disease for which outcomes with standard "3 + 7"-based chemotherapy have remained unsatisfactory in many patients.

Bortezomib for the treatment of non-Hodgkin's lymphoma

INTRODUCTION

Bortezomib , the first proteasome inhibitor (PI) to be evaluated in humans, is approved in the USA and Europe for the treatment of patients with multiple myeloma, and in the USA for patients with relapsed mantle cell lymphoma (MCL).

AREAS COVERED

This review examines the role of bortezomib in the therapy of non-Hodgkin's lymphoma (NHL). Bortezomib may be particularly effective against the NF-κB-dependent activated B-cell subtype of diffuse large B-cell lymphoma. The combination of bortezomib with rituximab and dexamethasone represents a standard approach for the treatment of Waldenström's macroglobulinemia, and that with bendamustine and rituximab has demonstrated excellent efficacy in follicular lymphoma. Combinations with other novel agents, such as inhibitors of cyclin-dependent kinases or histone deacetylases, also hold substantial promise in NHL. Unmet needs in NHL, competitor compounds, chemistry, pharmacokinetics, pharmacodynamics and safety and tolerability of bortezomib are also discussed.

EXPERT OPINION

The success of bortezomib in MCL has validated the proteasome as a therapeutic target in NHL. Rational combinations, for example, with Bruton's tyrosine kinase inhibitors or BH3-mimetics, may hold the key to optimizing the therapeutic potential of PIs in NHL. Future trials are likely to involve newer agents with improved pharmacodynamic (e.g., carfilzomib, marizomib) or pharmacokinetic (e.g., ixazomib, oprozomib) properties.

Immune-based therapies for childhood cancer

After decades of research, immunotherapies for cancer are demonstrating increasing success. These agents can amplify existent antitumour immunity or induce durable antitumour immune responses in a wide array of cancers. The spectrum of immunotherapeutics is broad, spanning monoclonal antibodies and their derivatives, tumour vaccines, and adoptive therapies using T cells and natural killer cells. Only a small number of immunotherapies have been tested in paediatric cancers, but impressive antitumour effects have already been observed. Mononclonal antibodies targeting GD2 that induce antibody-dependent cell-mediated cytotoxicity improve survival in high-risk neuroblastoma. Bi-specific monoclonal antibodies that simultaneously target CD19 and activate T cells can induce remission in acute B-cell lymphoblastic leukaemia (B-ALL) and adoptive immunotherapy using T cells genetically engineered to express chimeric antigen receptors targeting CD19 induce impressive responses in B-ALL. Efforts are underway to generate and test new immunotherapies in a wider array of paediatric cancers. Major challenges include a need to identify immunotherapy targets on the most lethal childhood cancers, to expand availability of technology-intense platforms, such as adoptive cell therapy, to optimize management of novel toxicities associated with this new class of cancer therapies and to determine how best to incorporate these therapies into standard treatment paradigms.