Development and application of CD19-specific T cells for adoptive immunotherapy of B cell malignancies

Chimeric antigen receptor T cell therapy: a new emerging landscape in autoimmune rheumatic diseases

Chimeric antigen receptor T cell (CAR-T) therapy, an innovative immune cell therapy, has revolutionized the treatment landscape of haematological malignancies. The past 2 years has witnessed the successful application of CD19-targeting CAR constructs in refractory cases of autoimmune rheumatic diseases, including systemic lupus erythematosus, systemic sclerosis and anti-synthetase syndrome. In comparison with existing B cell depletion therapies, targeting CD19 has demonstrated a more rapid and profound therapeutic effect, enabling drug-free remission with manageable adverse events. These promising results necessitate validation through long-term, large-sample randomized controlled studies. Corroborating the role of CAR-T therapy in refractory rheumatological disorders and affirming safety, efficacy and durability of responses are the aims of future clinical studies. Optimizing the engineering strategies and better patient selection are also critical to further refining the successful clinical implementation of CAR-T therapy.

Redefining Precision Management of r/r Large B-Cell Lymphoma: Novel Antibodies Take on CART and BMT in the Quest for Future Treatment Strategies

The treatment paradigms for patients with relapsed large B-cell lymphoma are expanding. Chimeric antigen receptor technology (CAR-T) has revolutionized the management of these patients. Novel bispecific antibodies and antibody-drug conjugates, used as chemotherapy-free single agents or in combination with other novel therapeutics, have been quickly introduced into the real-world setting. With such a paradigm shift, patients have an improved chance of better outcomes with unpredictable complete remission rates. Additionally, the excellent tolerance of new antibodies targeting B-cell lymphomas is another motivation to broaden its use in relapsed and refractory patients. With the increasing number of approved therapy approaches, future research needs to focus on optimizing the sequence and developing new combination strategies for these antibodies, both among themselves and with other agents. Clinical, pathological, and genetic risk profiling can assist in identifying which patients are most likely to benefit from these costly therapeutic options. However, new combinations may lead to new side effects, which we must learn to deal with. This review provides a comprehensive overview of the current state of research on several innovative antibodies for the precision management of large B-cell lymphoma. It explores various treatment strategies, such as CAR-T vs. ASCT, naked antibodies, antibody-drug conjugates, bispecific antibodies, and bispecific T-cell engagers, as well as discussing the challenges and future perspectives of novel treatment strategies. We also delve into resistance mechanisms and factors that may affect decision making. Moreover, each section provides a detailed analysis of the available literature and ongoing clinical trials.

Antibody-drug conjugates for lymphoma patients: preclinical and clinical evidences

Antibody-drug conjugates (ADCs) are a recent, revolutionary approach for malignancies treatment, designed to provide superior efficacy and specific targeting of tumor cells, compared to systemic cytotoxic chemotherapy. Their structure combines highly potent anti-cancer drugs (payloads or warheads) and monoclonal antibodies (Abs), specific for a tumor-associated antigen, via a chemical linker. Because the sensitive targeting capabilities of monoclonal Abs allow the direct delivery of cytotoxic payloads to tumor cells, these agents leave healthy cells unharmed, reducing toxicity. Different ADCs have been approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of a wide range of malignant conditions, both as monotherapy and in combination with chemotherapy, including for lymphoma patients. Over 100 ADCs are under preclinical and clinical investigation worldwide. This paper it provides an overview of approved and promising ADCs in clinical development for the treatment of lymphoma. Each component of the ADC design, their mechanism of action, and the highlights of their clinical development progress are discussed.

Targeting CD19 in diffuse large B-cell lymphoma: An expert opinion paper

The ubiquitous, early-stage expression, efficient internalization, limited off-target effects, and high disease specificity of CD19 make it an attractive therapeutic target. Currently available anti-CD19 therapies have demonstrated particular promise in patients with relapsed or refractory B-cell non-Hodgkin lymphoma. Selection of the most appropriate treatment strategy should be based on individual patient characteristics and the goal of therapy. However, evidence and knowledge about the sequencing of anti-CD19 therapies are limited. Here, we review the current evidence for CD19 as a target in diffuse large B-cell lymphoma and consider approaches to the use of anti-CD19 therapy.

Selection of a Nuclease-Resistant RNA Aptamer Targeting CD19

Simple Summary

Haematological malignancies show a constantly growing incidence, accounting for 6.5% of new cancer cases worldwide. Among them, B-cell neoplasms often show resistance to conventional chemotherapy that is also associated with numerous adverse effects. Therefore, in order for the treatment outcome to be improved, the development of new safe and effective targeted therapeutic approaches represents a main challenge. In this regard, nucleic acid aptamers are very attractive molecules. Indeed, they show high affinity and specificity for their target, increased tumour penetration, and low toxicity. Recently, CD19 has emerged as a key surface marker of malignant B cells, suitable for the development of new compounds for malignant B-cell targeting. Here, we isolated an RNA aptamer targeting the human CD19 antigen on malignant B cells that was able to rapidly internalise into target cells. Therefore, it represents a useful carrier for secondary reagents and a promising tool for the development of new safe and effective targeted therapies for B-cell malignancy treatment.

Abstract

The transmembrane glycoprotein cluster of differentiation 19 (CD19) is a B cell–specific surface marker, expressed on the majority of neoplastic B cells, and has recently emerged as a very attractive biomarker and therapeutic target for B-cell malignancies. The development of safe and effective ligands for CD19 has become an important need for the development of targeted conventional and immunotherapies. In this regard, aptamers represent a very interesting class of molecules. Additionally referred to as ‘chemical antibodies’, they show many advantages as therapeutics, including low toxicity and immunogenicity. Here, we isolated a nuclease-resistant RNA aptamer binding to the human CD19 glycoprotein. In order to develop an aptamer also useful as a carrier for secondary reagents, we adopted a cell-based SELEX (Systematic Evolution of Ligands by EXponential Enrichment) protocol adapted to isolate aptamers able to internalise upon binding to their cell surface target. We describe a 2′-fluoro pyrimidine modified aptamer, named B85.T2, which specifically binds to CD19 and shows an exquisite stability in human serum. The aptamer showed an estimated dissociation constant (K_D) of 49.9 ± 13 nM on purified human recombinant CD19 (rhCD19) glycoprotein, a good binding activity on human B-cell chronic lymphocytic leukaemia cells expressing CD19, and also an effective and rapid cell internalisation, thus representing a promising molecule for CD19 targeting, as well as for the development of new B-cell malignancy-targeted therapies.

Monoclonal Antibody Therapies for Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder

Considerable progress has been made in treatments for multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) over the last several decades. However, the present treatments do not show satisfactory efficacy or safety in a considerable proportion of patients, who experience relapse or disability progression despite receiving treatment and suffer from side effects, which can be severe. Improvements in the understanding of the pathophysiologies of MS and NMOSD have led to numerous therapeutic approaches being proposed and developed. Monoclonal antibodies (mAbs) are receiving increasing attention because of their specificity of action and likelihood of high efficacy with fewer side effects. Many mAbs have been evaluated, and some have been approved for MS or NMOSD treatment. This article reviews the use of mAbs for treating MS and NMOSD, including summarizing their mechanisms of action, efficacy, and safety profiles.

Mesothelin-targeted second generation CAR-T cells inhibit growth of mesothelin-expressing tumors in vivo

Non-small cell lung cancer (NSCLC) and mesothelioma are renowned for being diagnosed at a late stage and poor prognosis. Although surgery, chemotherapy, and radiotherapy have yielded successful outcomes, the improvement on the survival rate of NSCLC and mesothelioma have been less marked. Recently, adoptive immunotherapy, particularly chimeric antigen receptor T (CAR-T) cell therapy demonstrated promise for improving the survival of acute lymphoblastic leukemia with minimum toxicity. However, its application in solid tumors still warrants in-depth investigations and multiple consistent trial results, particularly in eliminating 'off-tumor' toxicity. To explore CAR-T therapy in NSCLC and mesothelioma, second-generation CAR-T cells were constructed targeting mesothelin (MSLN), which is abundant in NSCLC and mesothelioma but is under expressed in normal tissues. The second-generation design incorporated co-stimulatory CD28 and 4-1BB signaling domains to enhance the proliferation. Following the successful analysis of CAR-T cells by flow cytometry, cytotoxicity experiments were performed using the LDH kit to verify the killing effect of CAR-T cells on target cells. Otherwise, the in vivo killing tumor activity of MSLN CAR-T cells was verified by constructing a mouse model using tumor-derived cells from patients to inoculate the mice. When the effector-to-target ratio is >0.5:1, CAR-T MSLN cells exhibited significantly higher ability to kill tumor cells than T cells. In in vivo experiments, mice whose tail vein was injected with CAR-T MSLN cells demonstrated significantly slower tumor growth. Without continuous administration, both groups became gradually synchronized in growth of tumor size, which suggests that the persistence of CAR-T cells is an important issue in preclinical studies.

Generation and characterization of avian-derived anti-human CD19 single chain fragment antibodies

The human cluster of differentiation 19 (CD19) is highly expressed in most leukemia, rendering is a promising therapeutic target. In this study, we generated anti-CD19 single-chain variable fragments (scFv) from immunized chickens by phage display technology. After constructing a scFv antibody library with 2.5 × 10⁸ compositional diversity for panning, one representative scFv clone S2 which can specifically recognize to the CD19 protein was isolated and characterized. The binding reactivity of the scFv S2 to the endogenous CD19 protein of the ARH-77 leukemia cancer cell was verified through flow cytometry and the binding affinity of scFv S2 is 6.9 × 10^-8 M determined by the surface plasmon resonance system. Compared with the chicken germline, hyper mutation in the complementarity-determining regions (CDRs) suggested that scFv S2 could be generated through an antigen-driven humoral response. By molecular modeling, the possible CDR configurations of scFv S2 were constructed rationally. Furthermore, the characteristics of chicken antibodies of a protein database were investigated. The findings in this study contribute to antibody development and engineering because they reveal the geometric structures and properties of the CDRs in chicken antibodies.

Development of novel anti-CD19 antibody-drug conjugates for B-cell lymphoma treatment

B-cell lymphoma remains one of the most refractory tumors, and as such the development of novel treatment approaches, such as antibody-drug conjugates (ADCs), is required. To improve the stability and homogeneity of the ADCs, a humanized anti-CD19 monoclonal antibody (RC58) was developed in the present study. RC58 was based on the CD19 antigen as a potential molecular target of human B-cell lymphomas. RC58 has high CD19-binding affinity and can be internalized in CD19-positive cells through endocytosis. Furthermore, three types of RC58-based ADCs (ADC-1, ADC-2, and ADC-3) were generated using three kinds of Maleimide-PEG-based linkers with two different cytotoxins. The anti-tumor activities of the ADCs were confirmed by in vitro and in vivo experiments. The stability of the ADCs was also evaluated by incubation in human plasma for 10 days. In vitro experiments showed that the three ADCs had distinct inhibitory effects on several B-lymphoma cell lines. Meanwhile, a close correlation between efficacy and drug concentration was found in a nude mouse xenograft model of human B-cell lymphoma, after treatment with RC58-based ADCs. Our results suggest that ADC-1, with high efficiency, could be used as a potential therapeutic agent for human B-cell malignancies.

Selection of a novel CD19 aptamer for targeted delivery of doxorubicin to lymphoma cells

CD19 is overexpressed in most human B cell malignancies and considered an important tumor marker for diagnosis and treatment. Aptamers are oligonucleotides that may potentially serve as tumor-homing ligand for targeted cancer therapy with excellent affinity and specificity. In this study, we selected a novel CD19 aptamer (LC1) that was a 59-nucleotide single strand DNA. The aptamer could bind to recombinant CD19 protein with a Kd of 85.4 nM, and had minimal cross reactivity to bovine serum albumin (BSA) or ovalbumin (OVA). Moreover, the aptamer was found capable of binding with the CD19-positive lymphoma cells (Ramos and Raji), but not the CD19-negative cell lines (Jurkat and NB4). An aptamer-doxorubicin complex (Apt-Dox) was also formulated, and selectively delivered doxorubicin to CD19-positive lymphoma cells in vitro. The results indicate that aptamer LC1 can recognize CD19-positive tumor cells and may potentially function as a CD19-targeting ligand.

ADCT-402, a PBD dimer-containing antibody drug conjugate targeting CD19-expressing malignancies

Human CD19 antigen is a 95-kDa type I membrane glycoprotein in the immunoglobulin superfamily whose expression is limited to the various stages of B-cell development and differentiation and is maintained in the majority of B-cell malignancies, including leukemias and non-Hodgkin lymphomas of B-cell origin. Coupled with its differential and favorable expression profile, CD19 has rapid internalization kinetics and is not shed into the circulation, making it an ideal target for the development of antibody-drug conjugates (ADCs) to treat B-cell malignancies. ADCT-402 (loncastuximab tesirine) is a novel CD19-targeted ADC delivering SG3199, a highly cytotoxic DNA minor groove interstrand crosslinking pyrrolobenzodiazepine (PDB) dimer warhead. It showed potent and highly targeted in vitro cytotoxicity in CD19-expressing human cell lines. ADCT-402 was specifically bound, internalized, and trafficked to lysosomes in CD19-expressing cells and, following release of the PBD warhead, resulted in formation of DNA crosslinks that persisted for 36 hours. Bystander killing of CD19- cells by ADCT-402 was also observed. In vivo, single doses of ADCT-402 resulted in highly potent, dose-dependent antitumor activity in several subcutaneous and disseminated human tumor models with marked superiority to comparator ADCs delivering tubulin inhibitors. Dose-dependent DNA crosslinks and γ-H2AX DNA damage response were measured in tumors by 24 hours after single dose administration, whereas matched peripheral blood mononuclear cells showed no evidence of DNA damage. Pharmacokinetic analysis in rat and cynomolgus monkey showed excellent stability and tolerability of ADCT-402 in vivo. Together, these impressive data were used to support the clinical testing of this novel ADC in patients with CD19-expressing B-cell malignancies.

MGD011, A CD19 x CD3 Dual-Affinity Retargeting Bi-specific Molecule Incorporating Extended Circulating Half-life for the Treatment of B-Cell Malignancies

Purpose: CD19, a B-cell lineage-specific marker, is highly represented in B-cell malignancies and an attractive target for therapeutic interventions. MGD011 is a CD19 x CD3 DART bispecific protein designed to redirect T lymphocytes to eliminate CD19-expressing cells. MGD011 has been engineered with a modified human Fc domain for improved pharmacokinetic (PK) properties and designed to cross-react with the corresponding antigens in cynomolgus monkeys. Here, we report on the preclinical activity, safety and PK properties of MGD011.Experimental Design: The activity of MGD011 was evaluated in several in vitro and in vivo models. PK, safety and pharmacodynamic activity was also assessed in dose-escalation and repeat-dose studies of MGD011 administered once weekly in cynomolgus monkeys.Results: MGD011 mediated killing of human B-cell lymphoma lines by human or cynomolgus monkey PBMCs as well as autologous B-cell depletion in PBMCs from both species. MGD011-mediated killing was accompanied by target-dependent T-cell activation and expansion, cytokine release and upregulation of perforin and granzyme B. MGD011 demonstrated antitumor activity against localized and disseminated lymphoma xenografts reconstituted with human PBMCs. In cynomolgus monkeys, MGD011 displayed a terminal half-life of 6.7 days; once weekly intravenous infusion of MGD011 at doses up to 100 μg/kg, the highest dose tested, was well tolerated and resulted in dose-dependent, durable decreases in circulating B cells accompanied by profound reductions of B lymphocytes in lymphoid organs.Conclusions: The preclinical activity, safety and PK profile support clinical investigation of MGD011 as a therapeutic candidate for the treatment of B-cell malignancies. Clin Cancer Res; 23(6); 1506-18. ©2016 AACR.

CD19-redirected chimeric antigen receptor-modified T cells: a promising immunotherapy for children and adults with B-cell acute lymphoblastic leukemia (ALL)

Relapsed and chemotherapy-refractory B-cell acute lymphoblastic leukemia (B-ALL) remain significant causes of cancer-associated morbidity and mortality for children and adults. Development of new molecularly targeted treatment strategies for patients with high-risk B-ALL is thus a major preclinical and clinical priority. Adoptive cellular therapy with patient-derived human T cells genetically engineered to express CD19 redirected chimeric antigen receptors (CD19 CAR T cells) is one immunotherapeutic modality that has recently demonstrated remarkable efficacy in re-inducing remission in patients with multiply relapsed B-ALL. Investigative teams at several major cancer centers are currently conducting phase I clinical trials in children and/or adults with relapsed/refractory B-ALL to assess the safety and to identify the maximally tolerated dose of each group's CD19 CAR T-cell product. All groups have reported major clinical toxicities associated with CD19 CAR T-cell treatment, including cytokine release syndrome (CRS) and macrophage activation syndrome, neurologic dysfunction and aplasia of normal B lymphocytes, while CD19 CAR T cells persist in vivo. Toxicities have generally been transient or manageable with supportive care measures. Some patients with life-threatening CD19 CAR T-cell induced sequelae have received anti-cytokine receptor antibody treatment to diminish CRS symptoms and/or corticosteroids to terminate CAR T-cell proliferation. Remarkably, 67-90% of children and adults with B-ALL treated with CD19 CAR T cells in these trials have achieved morphologic leukemia remission with many patients also in molecular remission. The duration of CD19 CAR T cell persistence in vivo has varied appreciably among treated patients and likely reflects differences in the CD19 CAR constructs utilized at each institution. CD19-positive and CD19-negative B-ALL relapses after CD19 CAR T-cell treatment have occurred in some patients. Phase II trials to assess the efficacy of CD19 CAR T-cell immunotherapy in larger cohorts of patients with relapsed/refractory B-ALL are ongoing or planned.

CD19-Targeted Nanodelivery of Doxorubicin Enhances Therapeutic Efficacy in B-Cell Acute Lymphoblastic Leukemia

Nanomedicine has advanced to clinical trials for adult cancer therapy. However, the field is still in its infancy for treatment of childhood malignancies such as acute lymphoblastic leukemia (ALL). Nanotherapy offers multiple advantages over conventional therapy. It facilitates targeted delivery and enables controlled release of drugs to reduce treatment-related side effects. Here, we demonstrate that doxorubicin (DOX) encapsulated in polymeric nanoparticles (NPs) modified with targeting ligands against CD19 (CD19-DOX-NPs) can be delivered in a CD19-specific manner to leukemic cells. The CD19-DOX-NPs were internalized via receptor-mediated endocytosis and imparted cytotoxicity in a CD19-dependent manner in CD19-positive ALL cells. Leukemic mice treated with CD19-DOX-NPs survived significantly longer and manifested a higher degree of agility, indicating reduced apparent systemic toxicity during treatment compared to mice treated with free DOX. We suggest that targeted delivery of drugs used in childhood cancer treatment should improve therapeutic efficacy and reduce treatment-related side effects in children.

Genetic Engineering of T Cells to Target HERV-K, an Ancient Retrovirus on Melanoma

PURPOSE

The human endogenous retrovirus (HERV-K) envelope (env) protein is a tumor-associated antigen (TAA) expressed on melanoma but not normal cells. This study was designed to engineer a chimeric antigen receptor (CAR) on T-cell surface, such that they target tumors in advanced stages of melanoma.

EXPERIMENTAL DESIGN

Expression of HERV-K protein was analyzed in 220 melanoma samples (with various stages of disease) and 139 normal organ donor tissues using immunohistochemical (IHC) analysis. HERV-K env-specific CAR derived from mouse monoclonal antibody was introduced into T cells using the transposon-based Sleeping Beauty (SB) system. HERV-K env-specific CAR(+) T cells were expanded ex vivo on activating and propagating cells (AaPC) and characterized for CAR expression and specificity. This includes evaluating the HERV-K-specific CAR(+) T cells for their ability to kill A375-SM metastasized tumors in a mouse xenograft model.

RESULTS

We detected HERV-K env protein on melanoma but not in normal tissues. After electroporation of T cells and selection on HERV-K(+) AaPC, more than 95% of genetically modified T cells expressed the CAR with an effector memory phenotype and lysed HERV-K env(+) tumor targets in an antigen-specific manner. Even though there is apparent shedding of this TAA from tumor cells that can be recognized by HERV-K env-specific CAR(+) T cells, we observed a significant antitumor effect.

CONCLUSIONS

Adoptive cellular immunotherapy with HERV-K env-specific CAR(+) T cells represents a clinically appealing treatment strategy for advanced-stage melanoma and provides an approach for targeting this TAA on other solid tumors.

CD19 as a molecular target in CNS autoimmunity

Multiple sclerosis (MS) and neuromyelitis optica (NMO) are the most prevalent neuroinflammatory diseases of the central nervous system (CNS). The immunological cascade of these disorders is complex, and the exact spatial and temporal role of different immune cells is not fully understood. Although MS has been considered for many years to be primarily T cell driven, it is well established that B cells and the humoral immune response play an important role in its pathogenesis. This has long been evident from laboratory findings that include the presence of oligoclonal bands in the CSF. In NMO, the importance of the humoral immune system appears even more obvious as evidenced by pathogenic antibodies against aquaporin 4 (AQP4). Besides their capacity to mature into antibody-producing plasma cells, B cells are potent antigen-presenting cells to T lymphocytes and they can provide soluble factors for cell activation and differentiation to other immune-competent cells. In MS and NMO, there are substantial data from clinical trials that B cell depletion with CD20-directed agents is effective and relatively safe. Plasma cells, which produce antibodies against molecular targets expressed by the host, but which also provide humoral immune responses against pathogens, are not targeted by anti-CD20 therapies. Therefore, the depletion of CD19-expressing cells would offer potential advantages with regard to efficacy, but potentially higher risks with regard to infectious complications. This review will outline the rationale for CD19 as a molecular target in CNS autoimmunity. The current stage of drug development is illustrated. Potential safety concerns will be discussed.

The plasma cell signature in autoimmune disease

OBJECTIVE

Production of pathogenic autoantibodies by self-reactive plasma cells (PCs) is a hallmark of autoimmune diseases. We undertook this study to investigate the prevalence of PCs and their relationship to known pathogenic pathways to increase our understanding of the role of PCs in disease progression and treatment response.

METHODS

We developed a sensitive gene expression-based method to overcome the challenges of measuring PCs using flow cytometry. Whole-genome microarray analysis of sorted cellular fractions identified a panel of genes, IGHA1, IGJ, IGKC, IGKV4-1, and TNFRSF17, expressed predominantly in PCs. The sensitivity of the PC signature score created from the combined expression levels of these genes was assessed through ex vivo experiments with sorted cells. This PC gene expression signature was used for monitoring changes in PC levels following anti-CD19 therapy, for evaluating the relationship between PCs and other autoimmune disease-related genes, and for estimating PC levels in affected blood and tissue from patients with multiple autoimmune diseases.

RESULTS

The PC signature was highly sensitive and capable of detecting a change in as few as 360 PCs. The PC signature was reduced more than 90% in scleroderma patients following anti-CD19 treatment, and this reduction was highly correlated (r = 0.80) with inhibition of collagen gene expression. Evaluation of multiple autoimmune diseases revealed that 30-35% of lupus and rheumatoid arthritis patients had increased levels of PCs.

CONCLUSION

This newly developed PC signature provides a robust and accurate method of measuring PC levels in the clinic. Our results highlight subsets of patients across multiple autoimmune diseases who may benefit from PC-depleting therapy.

Engineered T cells for cancer treatment

Adoptively transferred T cells have the capacity to traffic to distant tumor sites, infiltrate fibrotic tissue and kill antigen-expressing tumor cells. Various groups have investigated different genetic engineering strategies designed to enhance tumor specificity, increase T cell potency, improve proliferation, persistence or migratory capacity and increase safety. This review focuses on recent developments in T cell engineering, discusses the clinical application of these engineered cell products and outlines future prospects for this therapeutic modality.

Regimen-specific effects of RNA-modified chimeric antigen receptor T cells in mice with advanced leukemia

Cytotoxic T lymphocytes modified with chimeric antigen receptors (CARs) for adoptive immunotherapy of hematologic malignancies have demonstrated activity in early phase clinical trials. While T cells bearing stably expressed CARs are efficacious and have potential long-term persistence, temporary expression of a CAR via RNA electroporation is also potentially efficacious in preclinical models. Temporary CAR expression using RNA presents a method of testing CARs clinically with additional safety where there may be concerns about possible chronic "on-target, off-tumor" toxic effects, as the degradation of RNA ensures complete removal of the CAR over time without relying on suicide induction systems. CD19-directed RNA CAR T cells were tested in vivo for efficacy and comparison to lentiviral vector (LV)-generated stable CAR T cells. We tested the hypothesis that multiple infusions of RNA CAR T cells preceded by lymphodepleting chemotherapy could mediate improved survival and sustained antitumor responses in a robust leukemia xenograft model. The saturation strategy using rationally designed multiple infusions of RNA CARs based on multiple model iterations approached the efficacy of a stable LV expression method. Two-color imaging revealed that relapse was a locoregional phenomenon in both the temporary and the stable expression models. In marked contrast to stably expressed CARs with retroviral or LV technology, the efficacy of RNA CARs appears independent of the costimulatory signaling endodomains likely because they more influence proliferation and persistence rather than short-term efficacy. The efficacy of the RNA CAR infusions may approach that of stably expressed CARs, offer theoretically safer initial clinical testing in addition to suicide systems, and allow for rapid and effective iterative preclinical modeling for the testing of new targets.

Current translational and clinical practices in hematopoietic cell and gene therapy

Clinical trials over the last 15 years have demonstrated that cell and gene therapies for cancer, monogenic and infectious disease are feasible and can lead to long-term benefit for patients. However, these trials have been limited to proof-of-principle and were conducted on modest numbers of patients or over long periods of time. In order for these studies to move towards standard practice and commercialization, scalable technologies for the isolation, ex vivo manipulation and delivery of these cells to patients must be developed. Additionally, regulatory strategies and clinical protocols for the collection, creation and delivery of cell products must be generated. In this article we review recent progress in hematopoietic cell and gene therapy, describe some of the current issues facing the field and discuss clinical, technical and regulatory approaches used to navigate the road to product development.

Bayesian continual reassessment method for dose-finding trials infusing T cells with limited sample size

We consider the design of dose-finding trials for patients with malignancies when only a limited sample size is available. The small sample size may be necessary because (1) the modality of treatment is very expensive, and/or (2) the disease under investigation is rare, requiring a lengthy period to enroll a target patient population. Both of these are common in the field of adoptive immunotherapy, in which T cells are infused to prevent and treat infections and malignancies. The clinical trial described in this paper investigates a novel therapy to adoptively transfer genetically modified T cells in small pilot protocols enrolling patients with B-lineage malignancies. Due to the constraints of cost and infrastructure, the maximum sample size for this trial is fixed at 12 patients distributed among four doses of T cells. Given these limitations, an innovative statistical design has been developed to efficiently evaluate the safety, feasibility, persistence, and toxicity profiles of the trial doses. The proposed statistical design is specifically tailored for trials with small sample sizes in that it uses the toxicity outcomes from patients treated at different doses to make dose-finding decisions. Supplementary materials including an R function and a movie demo can be downloaded in the websites mentioned in the paper.

CD19: a biomarker for B cell development, lymphoma diagnosis and therapy

The human CD19 antigen is a 95 kd transmembrane glycoprotein belonging to the immunoglobulin superfamily. CD19 is classified as a type I transmembrane protein, with a single transmembrane domain, a cytoplasmic C-terminus, and extracellular N-terminus. CD19 is a biomarker for normal and neoplastic B cells, as well as follicular dendritic cells. CD19 is critically involved in establishing intrinsic B cell signaling thresholds through modulating both B cell receptor-dependent and independent signaling. CD19 functions as the dominant signaling component of a multimolecular complex on the surface of mature B cells, alongside complement receptor CD21, and the tetraspanin membrane protein CD81 (TAPA-1), as well as CD225. Through study of CD19 transgenic and knockout mouse models, it becomes clear that CD19 plays a critical role in maintaining the balance between humoral, antigen-induced response and tolerance induction. This review also summarized latest clinical development of CD19 antibodies, anti-B4-bR (an immunotoxin conjugate), blinatumomab (BiTE), and SAR3419 (huB4-DM4), a novel antibody-drug conjugate.

A foundation for universal T-cell based immunotherapy: T cells engineered to express a CD19-specific chimeric-antigen-receptor and eliminate expression of endogenous TCR

Clinical-grade T cells are genetically modified ex vivo to express a chimeric antigen receptor (CAR) to redirect specificity to a tumor associated antigen (TAA) thereby conferring antitumor activity in vivo. T cells expressing a CD19-specific CAR recognize B-cell malignancies in multiple recipients independent of major histocompatibility complex (MHC) because the specificity domains are cloned from the variable chains of a CD19 monoclonal antibody. We now report a major step toward eliminating the need to generate patient-specific T cells by generating universal allogeneic TAA-specific T cells from one donor that might be administered to multiple recipients. This was achieved by genetically editing CD19-specific CAR(+) T cells to eliminate expression of the endogenous αβ T-cell receptor (TCR) to prevent a graft-versus-host response without compromising CAR-dependent effector functions. Genetically modified T cells were generated using the Sleeping Beauty system to stably introduce the CD19-specific CAR with subsequent permanent deletion of α or β TCR chains with designer zinc finger nucleases. We show that these engineered T cells display the expected property of having redirected specificity for CD19 without responding to TCR stimulation. CAR(+)TCR(neg) T cells of this type may potentially have efficacy as an off-the-shelf therapy for investigational treatment of B-lineage malignancies.

Cellular therapies in acute lymphoblastic leukemia

ALL remains a difficult disease to treat. In the adult setting, most patients will ultimately die of their disease, whereas in the pediatric setting, relapsed and refractory disease remains a therapeutic challenge. Cellular therapy through allo-HSCT remains an option for these patients, and recent advances in alternative forms of allo-HSCT, including unrelated donor transplants, UCB transplants, and haploidentical transplants, have expanded the numbers of patients eligible for allo-HSCT but have not improved outcomes when compared with HLA-matched related allo-HSCTs. In light of this persistent failure, several novel adoptive cellular approaches are being investigated to treat patients with ALL. The use of enriched WT-1–specific donor T cells to treat patients with ALL is currently under investigation in phase I trials at several centers. Treatment of ALL with genetically modified T cells targeted to the CD19 antigen through the expression of a CD19-specific CAR also have entered phase I clinical trials at several centers. Similarly, a clinical trial treating patients with ALL with genetically modified NK cells targeted to the CD19 antigen has recently opened for accrual. Collectively, these ongoing and anticipated trials provide a promising role for adoptive cellular therapies in the treatment of ALL. What remains to be seen is whether this promise will either translate into improved outcomes for these patients or provide significant insights on which to design second-generation adoptive cell therapeutic clinical trials for ALL in the future.

Genetically modified T cells targeting interleukin-11 receptor α-chain kill human osteosarcoma cells and induce the regression of established osteosarcoma lung metastases

The treatment of osteosarcoma pulmonary metastases remains a challenge. T cells genetically modified to express a chimeric antigen receptor (CAR), which recognizes a tumor-associated antigen, have shown activity against hematopoietic malignancies in clinical trials, but this requires the identification of a specific receptor on the tumor cell. In the current study, we found that interleukin (IL)-11Rα was selectively expressed on 14 of 16 osteosarcoma patients' lung metastases and four different human osteosarcoma cell lines, indicating that IL-11Rα may be a novel target for CAR-specific T-cell therapy. IL-11Rα expression was absent or low in normal organ tissues, with the exception of the gastrointestinal tract. IL-11Rα-CAR-specific T cells were obtained by non-viral gene transfer of Sleeping Beauty DNA plasmids and selectively expanded ex vivo using artificial antigen-presenting cells derived from IL-11Rα + K562 cells genetically modified to coexpress T-cell costimulatory molecules. IL-11Rα-CAR(+) T cells killed all four osteosarcoma cell lines in vitro; cytotoxicity correlated with the level of IL-11Rα expression on the tumor cells. Intravenous injection of IL-11Rα-CAR(+) T cells into mice resulted in the regression of osteosarcoma pulmonary metastases with no organ toxicity. Together, the data suggest that IL-11Rα-CAR T cells may represent a new therapy for patients with osteosarcoma pulmonary metastases.

Synergistic and persistent effect of T-cell immunotherapy with anti-CD19 or anti-CD38 chimeric receptor in conjunction with rituximab on B-cell non-Hodgkin lymphoma

Using artificial receptors, it is possible to redirect the specificity of immune cells to tumour-associated antigens, which is expected to provide a useful strategy for cancer immunotherapy. Given that B-cell non-Hodgkin lymphoma (B-NHL) cells invariably express CD19 and CD38, these antigens may be suitable molecular candidates for such immunotherapy. We transduced human peripheral T cells or a T-cell line with either anti-CD19-chimeric receptor (CAR) or anti-CD38-CAR, which contained an anti-CD19 or anti-CD38 antibody-derived single-chain variable domain respectively. Retroviral transduction led to anti-CD19-CAR or anti-CD38-CAR expression in T cells with high efficiency (>60%). The T cell line, Hut78, when transduced with anti-CD19-CAR or anti-CD38-CAR, exerted strong cytotoxicity against the B-NHL cell lines, HT and RL, and lymphoma cells isolated from patients. Interestingly, use of both CARs had an additive cytotoxic effect on HT cells in vitro. In conjunction with rituximab, human peripheral T cells expressing either anti-CD19-CAR or anti-CD38-CAR enhanced cytotoxicity against HT-luciferase cells in xenografted mice. Moreover, the synergistic tumour-suppressing activity was persistent in vivo for over 2 months. These results provide a powerful rationale for clinical testing of the combination of rituximab with autologous T cells carrying either CAR on aggressive or relapsed B-NHLs.

Non-MHC-dependent redirected T cells against tumor cells

Adoptive transfer of T cells with restricted tumor specificity provides a promising approach to immunotherapy of cancers. However, the isolation of autologous cytotoxic T cells that recognize tumor-associated antigens is time consuming and fails in many instances. Alternatively, gene modification with tumor antigen-specific T-cell receptors (TCR) or chimeric antigen receptors (CARs) can be used to redirect the specificity of large numbers of immune cells toward the malignant cells. Chimeric antigen receptors are composed of the single-chain variable fragment (scFv) of a tumor-recognizing antibody cloned in frame with human T-cell signaling domains (e.g., CD3zeta, CD28, OX40, 4-1BB), thus combining the specificity of antibodies with the effector functions of cytotoxic T cells. Upon antigen binding, the intracellular signaling domains of the CAR initiate cellular activation mechanisms including cytokine secretion and cytolysis of the antigen-positive target cell.In this chapter, we provide detailed protocols for large-scale ex vivo expansion of T cells and manufacturing of medium-scale batches of CAR-expressing T cells for translational research by mRNA electroporation. An anti-CD19 chimeric receptor for the targeting of leukemias and lymphomas was used as a model system. We are currently scaling up the protocols to adapt them to cGMP production of a large number of redirected T cells for clinical applications.

Treatment of lymphoma with adoptively transferred T cells

BACKGROUND

Chemotherapy-resistant lymphomas can be cured with allogeneic hematopoietic cell transplantation, demonstrating the susceptibility of these tumors to T cell mediated immune responses. However, high rates of transplant-related morbidity and mortality limit this approach. Efforts have, therefore, been made to develop alternative T cell based therapies, and there is growing evidence that adoptive therapy with T cells targeted to lymphoma-associated antigens may be a safe and effective new method for treating this group of diseases.

OBJECTIVE/METHODS

We review publications on adoptive therapy with ex vivo expanded T cells targeting viral antigens, as well as genetically modified autologous T cells, as strategies for the treatment of lymphoma, with the goal of providing an overview of these approaches.

RESULTS/CONCLUSIONS

Epstein-Barr virus specific T cell therapy is an effective and safe method of treating Epstein-Barr virus associated lymphomas; however, most lymphoma subtypes do not express EBV antigens. For these diseases, adoptive immunotherapy with genetically modified T cells expressing chimeric T cell receptors targeting lymphoma-associated antigens such as CD19 and CD20 appears to be a promising alternative. Recent innovations including enhanced co-stimulation, exogenous cytokine administration and use of memory T cells promise to overcome many of the limitations and pitfalls initially encountered with this approach.

Genetic engineering of T cells for adoptive immunotherapy

To be effective for the treatment of cancer and infectious diseases, T cell adoptive immunotherapy requires large numbers of cells with abundant proliferative reserves and intact effector functions. We are achieving these goals using a gene therapy strategy wherein the desired characteristics are introduced into a starting cell population, primarily by high efficiency lentiviral vector-mediated transduction. Modified cells are then expanded using ex vivo expansion protocols designed to minimally alter the desired cellular phenotype. In this article, we focus on strategies to (1) dissect the signals controlling T cell proliferation; (2) render CD4 T cells resistant to HIV-1 infection; and (3) redirect CD8 T cell antigen specificity.

Antigen-independent and antigen-dependent methods to numerically expand CD19-specific CD8+ T cells

OBJECTIVE

Preclinical and clinical trials are investigating the potential of T cells genetically modified to express a first-generation CD19-specific chimeric antigen receptor (CAR), designated CD19R, for adoptive immunotherapy of B-lineage leukemias and lymphomas. Currently, our genetically modified CD19-specific CD8+ (CD19R+CD8+) T cells are expanded ex vivo using a rapid expansion protocol (REP) to clinically meaningful numbers after antigen-independent activation with anti-CD3epsilon and recombinant human interleukin-2 on a double-cell feeder-layer of gamma-irradiated allogeneic peripheral blood mononuclear cells and a lymphoblastoid cell line. We now compare the ability of the REP with CD19-dependent numerical expansion using CD19+ artificial antigen-presenting cells to propagate CD19R+CD8+ T cells.

MATERIALS AND METHODS

We evaluated long-term (28 days) propagation, CD19R CAR expression, and cytolytic activity of CD19R+CD8+ T cells expanded by either a REP or an antigen expansion protocol (AEP) using K562-derived artificial antigen-presenting cells coexpressing CD19 antigen and two T-cell costimulatory molecules (4-1BB ligand and major histocompatibility class I-related chains A) in the presence of exogenous recombinant human interleukin-2 and recombinant human interleukin-15.

RESULTS

Populations of CD19R+CD8+ T cells could be numerically expanded on AEP to meet anticipated clinical need. The AEP was superior to REP, as this method selected for an outgrowth of T cells with increased CD19R CAR expression and improved redirected cytolytic activity.

CONCLUSION

Robust propagation of CD19R+CD8+ T cells achieved by AEP supports qualifying this cell line for use in current good manufacturing practices for CAR+ T cells as an alternative to REP for adoptive immunotherapy clinical trials.

Novel approaches to the immunotherapy of B-cell malignancies: An update

Immunotherapy of cancer includes both active and adoptive, or passive, forms of immunization to target and eradicate malignant B cells in the host. Advances in the understanding of immunology and tumor-cell evasion of the host immune system, coupled with improved technologies to manipulate immune effectors and tumors, have led to a wide array of novel therapies for B-cell malignancies. As a result, investigators have proposed and tested numerous vaccine strategies able to elicit immune responses to tumor antigens. Furthermore, novel approaches to B-cell-targeted antibody therapies hold promise in advancing this line of treatment, and efficient gene transfer technologies have enabled investigators to manipulate immune effector cells to enhance antitumor activity. Significantly, an increasing number of these novel immune-based therapies are being applied to the clinical setting. Whether findings from these clinical trials, in combination with further preclinical studies, will ultimately translate into improved survival of patients with B-cell malignancies remains to be seen.

Addition of the CD28 signaling domain to chimeric T-cell receptors enhances chimeric T-cell resistance to T regulatory cells

T cells can be engineered to target tumor cells by transduction of tumor-specific chimeric receptors, consisting of an extracellular antigen-binding domain and an intracellular signaling domain. However, the peripheral blood of cancer patients frequently contains an increased number of T regulatory cells, which appear to inhibit immune reactivity. We have investigated the effects of T regulatory cells on chimeric T cells specific for the B-cell antigen CD19, as B-cell malignancies are attractive targets for chimeric T-cell therapy. When a CD19 single-chain Fv antibody was coupled to the CD3 zeta (zeta) chain, there was sharply reduced activity on exposure to T regulatory cells, measured by CD19+ target-induced proliferation and cytotoxicity. By contrast, expression in T cells of a chimeric receptor consisting of the intracellular portion of the CD28 molecule fused to the zeta-chain and CD19 single-chain Fv not only produced a higher proliferative response and an increased nuclear factor kappaB activation but also sustained these activities in the presence of T regulatory cells. These effects are seen whether the chimeric T cells are derived from normal donors or from patients with B-cell chronic lymphocytic leukemia, indicating the potential for clinical application in B cell malignancies.

Manufacturing of gene-modified cytotoxic T lymphocytes for autologous cellular therapy for lymphoma

BACKGROUND

The production of therapeutic T-cell populations for adoptive immunotherapy of cancer requires extensive ex vivo cell processing, including the isolation or creation of Ag-specific T cells and their subsequent propagation to clinically relevant numbers. These procedures must be performed according to the principles of current good manufacturing practices (cGMP) for phase I clinical trials to ensure the identity, purity potency and safety of the cellular product. In this report we describe our approach to manufacturing and characterizing bulk populations of gene-modified autologous T cells for use in treating follicular lymphoma.

METHODS

PBMC from healthy donors, obtained after informed consent, were stimulated in vitro with Ab to CD3epsilon (OKT3) and recombinant human IL-2 and then electroporated with plasmid DNA containing a human CD19-specific chimeric Ag receptor (CAR) gene and HSV-1 thymidine kinase (TK) gene. Stably transfected cells were selected in cytocidal concentrations of hygromycin B over multiple 14-day stimulation culture cycles and then cryopreserved. Vials of cryopreserved/selected T cells were used to initiate T-cell expansion cultures to produce cell products for clinical infusion. These cultures were characterized for phenotype, function and suitability for use in adoptive immunotherapy studies.

RESULTS

Our results demonstrate that bulk populations of gene-modified T cells derived from peripheral blood of healthy donors express CD19+ chimeric Ag receptor at low levels and can specifically lyse CD19+ target cells in vitro. These cells display a differentiated T-effector phenotype, are sensitive to ganciclovir-mediated killing and display a non-transformed phenotype. TCR Vbeta usage indicated that all populations tested were polyclonal. Ex vivo cell expansion from cryopreserved cell banks is sufficient to produce doses of between 5 x 10(9) and 1 x 10(10) cells/run. One of three transductions resulted in a population of cells that was not suitable for infusion but was identified during release testing. No populations displayed any evidence of bacterial, fungal or mycoplasma contamination.

DISCUSSION

We have established a manufacturing strategy that is being used to produce T cells for a phase I clinical trial for follicular lymphoma. Genetically modified T cells have been characterized by cell-surface marker phenotype, functional activity against CD19+ targets and requisite safety testing. These pre-clinical data confirm the feasibility of this approach to manufacturing T-cell products.

Enhancing siRNA effects in T cells for adoptive immunotherapy

Genetically manipulated T cells can be endowed with novel functions to obtain desired in vivo effects after adoptive transfer. This genetic approach is being used to introduce genes such as chimeric immunoreceptors and tumor-specific T cells are being evaluated in early phase clinic trials. However, the ability to alter the genetic programming of T cells also presents opportunities to remove unwanted T-cell functions in order to augment an anti-tumor effect or endow resistance such as to HIV infection. Specifically, the use of RNA interference (RNAi) to disrupt gene expression by targeting either the mRNA or the promoter, provides investigators with many new opportunities to genetically modify T cells that should prove useful in future applications of adoptive immunotherapy.

Differentiation of naive cord-blood T cells into CD19-specific cytolytic effectors for posttransplantation adoptive immunotherapy

Disease relapse is a barrier to achieving therapeutic success after unrelated umbilical cord-blood transplantation (UCBT) for B-lineage acute lymphoblastic leukemia (B-ALL). While adoptive transfer of donor-derived tumor-specific T cells is a conceptually attractive approach to eliminating residual disease after allogeneic hematopoietic stem cell transplantation, adoptive immunotherapy after UCBT is constrained by the difficulty of generating antigen-specific T cells from functionally naive umbilical cord-blood (UCB)-derived T cells. Therefore, to generate T cells that recognize B-ALL, we have developed a chimeric immunoreceptor to redirect the specificity of T cells for CD19, a B-lineage antigen, and expressed this transgene in UCB-derived T cells. An ex vivo process, which is compliant with current good manufacturing practice for T-cell trials, has been developed to genetically modify and numerically expand UCB-derived T cells into CD19-specific effector cells. These are capable of CD19-restricted cytokine production and cytolysis in vitro, as well as mediating regression of CD19+ tumor and being selectively eliminated in vivo. Moreover, time-lapse microscopy of the genetically modified T-cell clones revealed an ability to lyse CD19+ tumor cells specifically and repetitively. These data provide the rationale for infusing UCB-derived CD19-specific T cells after UCBT to reduce the incidence of CD19+ B-ALL relapse.