T-cell genetic modification for re-directed tumor recognition

Universal CARs, universal T cells, and universal CAR T cells

Currently, the two approved T cell products with chimeric antigen receptors (CAR) are from autologous T cells. These CAR T cells approved for clinical use must be generated on a custom-made basis. This case-by-case autologous T cell production platform remains a significant limiting factor for large-scale clinical application due to the costly and lengthy production process. There is also an inherent risk of production failure. The individualized, custom-made autologous CAR T cell production process also posts constriction on the wide application on diverse tumor types. Therefore, universal allogeneic T cells are needed for the preparation of universal CAR T cells that can serve as the “off-the-shelf” ready-to-use therapeutic agents for large-scale clinical applications. Genome-editing technologies including ZFN (zinc finger nuclease), TALEN (transcription activator-like effector nuclease), and CRISPR-Cas9 are being used to generate the universal third-party T cells. In addition, split, universal, and programmable (SUPRA) CARs are being developed to enhance the flexibility and controllability of CAR T cells. The engineered universal T cells and universal CARs are paving the road for a totally new generation of CAR T cells capable of targeting multiple antigens and/ or being delivered to multiple recipients without re-editing of T cells. This may escalate to a new wave of revolution in cancer immunotherapy. This review summarized the latest advances on designs and development of universal CARs, universal T cells, and clinical application of universal CAR T cells.

Multiplex Genome-Edited T-cell Manufacturing Platform for "Off-the-Shelf" Adoptive T-cell Immunotherapies

Adoptive immunotherapy using autologous T cells endowed with chimeric antigen receptors (CAR) has emerged as a powerful means of treating cancer. However, a limitation of this approach is that autologous CAR T cells must be generated on a custom-made basis. Here we show that electroporation of transcription activator-like effector nuclease (TALEN) mRNA allows highly efficient multiplex gene editing in primary human T cells. We use this TALEN-mediated editing approach to develop a process for the large-scale manufacturing of T cells deficient in expression of both their αβ T-cell receptor (TCR) and CD52, a protein targeted by alemtuzumab, a chemotherapeutic agent. Functionally, T cells manufactured with this process do not mediate graft-versus-host reactions and are rendered resistant to destruction by alemtuzumab. These characteristics enable the administration of alemtuzumab concurrently or prior to engineered T cells, supporting their engraftment. Furthermore, endowing the TALEN-engineered cells with a CD19 CAR led to efficient destruction of CD19(+) tumor targets even in the presence of the chemotherapeutic agent. These results demonstrate the applicability of TALEN-mediated genome editing to a scalable process, which enables the manufacturing of third-party CAR T-cell immunotherapies against arbitrary targets. As such, CAR T-cell immunotherapies can therefore be used in an "off-the-shelf" manner akin to other biologic immunopharmaceuticals

IL-13 receptor-directed cancer vaccines and immunotherapy

Many immunotherapy approaches including therapeutic cancer vaccines targeting specific tumor-associated antigens are at various stages of development. Although the significance of overexpression of (IL-13Rα2) in cancer is being actively investigated, we have reported that IL-13Rα2 is a novel tumor-associated antigen. The IL-13Rα2-directed cancer vaccine is one of the most promising approaches to tumor immunotherapy, because of the selective expression of IL-13Rα2 in various solid tumor types but not in normal tissues. In this article, we will summarize its present status and potential strategies to improve IL-13Rα2-directed cancer vaccines for an optimal therapy of cancer.

A transgene-encoded cell surface polypeptide for selection, in vivo tracking, and ablation of engineered cells

An unmet need in cell engineering is the availability of a single transgene encoded, functionally inert, human polypeptide that can serve multiple purposes, including ex vivo cell selection, in vivo cell tracking, and as a target for in vivo cell ablation. Here we describe a truncated human EGFR polypeptide (huEGFRt) that is devoid of extracellular N-terminal ligand binding domains and intracellular receptor tyrosine kinase activity but retains the native amino acid sequence, type I transmembrane cell surface localization, and a conformationally intact binding epitope for pharmaceutical-grade anti-EGFR monoclonal antibody, cetuximab (Erbitux). After lentiviral transduction of human T cells with vectors that coordinately express tumor-specific chimeric antigen receptors and huEGFRt, we show that huEGFRt serves as a highly efficient selection epitope for chimeric antigen receptor(+) T cells using biotinylated cetuximab in conjunction with current good manufacturing practices (cGMP)-grade anti-biotin immunomagnetic microbeads. Moreover, huEGFRt provides a cell surface marker for in vivo tracking of adoptively transferred T cells using both flow cytometry and immunohistochemistry, and a target for cetuximab-mediated antibody-dependent cellular cytotoxicity and in vivo elimination. The versatility of huEGFRt and the availability of pharmaceutical-grade reagents for its clinical application denote huEGFRt as a significant new tool for cellular engineering.

Redirecting T-cell specificity by introducing a tumor-specific chimeric antigen receptor

Infusions of antigen-specific T cells have yielded therapeutic responses in patients with pathogens and tumors. To broaden the clinical application of adoptive immunotherapy against malignancies, investigators have developed robust systems for the genetic modification and characterization of T cells expressing introduced chimeric antigen receptors (CARs) to redirect specificity. Human trials are under way in patients with aggressive malignancies to test the hypothesis that manipulating the recipient and reprogramming T cells before adoptive transfer may improve their therapeutic effect. These examples of personalized medicine infuse T cells designed to meet patients' needs by redirecting their specificity to target molecular determinants on the underlying malignancy. The generation of clinical grade CAR(+) T cells is an example of bench-to-bedside translational science that has been accomplished using investigator-initiated trials operating largely without industry support. The next-generation trials will deliver designer T cells with improved homing, CAR-mediated signaling, and replicative potential, as investigators move from the bedside to the bench and back again.

Imaging immune response in vivo: cytolytic action of genetically altered T cells directed to glioblastoma multiforme

PURPOSE

Clinical trials have commenced to evaluate the feasibility of targeting malignant gliomas with genetically engineered CTLs delivered directly to the tumor bed in the central nervous system. The objective of this study is to determine a suite of magnetic resonance imaging (MRI) measurements using an orthotopic xenograft murine model that can noninvasively monitor immunologically mediated tumor regression and reactive changes in the surrounding brain parenchyma.

EXPERIMENTAL DESIGN

Our preclinical therapeutic platform is based on CTL genetic modification to express a membrane tethered interleukin-13 (IL-13) cytokine chimeric T-cell antigen receptor. This enables selective binding and signal transduction on encountering the glioma-restricted IL-13 alpha2 receptor (IL-13Ralpha2). We used MRI to visualize immune responses following adoptive transfer of IL-13Ralpha2-specific CD8+ CTL clones.

RESULTS

Based on MRI measurements, several phases following IL-13Ralpha2-specific T-cell adoptive transfer could be distinguished, all of which correlated well with glioblastoma regression confirmed on histology. The first detectable changes, 24 hours post-treatment, were significantly increased T2 relaxation times and strongly enhanced signal on T1-weighted postcontrast images. In the next phase, the apparent diffusion coefficient was significantly increased at 2 and 3 days post-treatment. In the last phase, at day 3 after IL-13Ralpha2-specific T-cell injection, the volume of hyperintense signal on T1-weighted postcontrast image was significantly decreased, whereas apparent diffusion coefficient remained elevated.

CONCLUSIONS

The present study indicates the feasibility of MRI to visualize different phases of immune response when IL-13Ralpha2-specific CTLs are administered directly to the glioma tumor bed. This will further the aim of better predicting clinical outcome following immunotherapy.

Preparing clinical grade Ag-specific T cells for adoptive immunotherapy trials

The production of clinical-grade T cells for adoptive immunotherapy has evolved from the ex vivo numerical expansion of tumor-infiltrating lymphocytes to sophisticated bioengineering processes often requiring cell selection, genetic modification and other extensive tissue culture manipulations, to produce desired cells with improved therapeutic potential. Advancements in understanding the biology of lymphocyte signaling, activation, homing and sustained in vivo proliferative potential have redefined the strategies used to produce T cells suitable for clinical investigation. When combined with new technical methods in cell processing and culturing, the therapeutic potential of T cells manufactured in academic centers has improved dramatically. Paralleling these technical achievements in cell manufacturing is the development of broadly applied regulatory standards that define the requirements for the clinical implementation of cell products with ever-increasing complexity. In concert with academic facilities operating in compliance with current good manufacturing practice, the prescribing physician can now infuse T cells with a highly selected or endowed phenotype that has been uniformly manufactured according to standard operating procedures and that meets federal guidelines for quality of investigational cell products. In this review we address salient issues related to the technical, immunologic, practical and regulatory aspects of manufacturing these advanced T-cell products for clinical use.

Optimizing adoptive polyclonal T cell immunotherapy of lymphomas, using a chimeric T cell receptor possessing CD28 and CD137 costimulatory domains

We previously demonstrated the feasibility of generating therapeutic numbers of cytotoxic T lymphocyte (CTL) clones expressing a CD20-specific scFvFc:CD3zeta chimeric T cell receptor (cTCR), making them specifically cytotoxic for CD20+ B lymphoma cells. However, the process of generating and expanding he CTL clones was laborious, the CTL clones expressed the cTCR at low surface density, and they exhibited suboptimal proliferation and cytotoxicity. To improve the performance of the CTLs in vitro and in vivo, we engineered "second-generation'' plasmid constructs containing a translational enhancer (SP163) and CD28 and CD137 costimulatory domains in cis with the CD3zeta intracellular signaling domain of the cTCR gene. Furthermore, we verified the superiority of generating genetically modified polyclonal T cells expressing the second-generation cTCR rather than T cell clones. Our results demonstrate that SP163 enhances the surface expression of the cTCR; that the second-generation cTCR improves CTL activation, proliferation, and cytotoxicity; and that polyclonal T cells proliferate rapidly in vitro and mediate potent CD20-specific cytotoxicity. This study provides the preclinical basis for a clinical trial of adoptive T cell immunotherapy for patients with relapsed CD20+ mantle cell lymphoma and indolent lymphomas.

Transgene-enforced co-stimulation of CD4+ T cells leads to enhanced and sustained anti-tumor effector functioning

Background The role of co-stimulation in CD4+ T cell activation by professional APC is well established, while less is known of the role co-stimulation plays when CD4+ T cells interact directly with tumor cells. Methods Through genetic engineering of human CD4+ T cells, we tested the hypothesis that integration of co-stimulatory signaling domains within a tumor-targeting chimeric Ag receptor (CAR), the IL-13Ralpha2-specific IL-13-zetakine (IL13zeta), would enhance CD4+ T cell mediated responses against tumors that fail to express ligands for co-stimulatory receptors. Results Compared with CD3zeta-mediated activation alone, CD4+ effector T cells expressing the IL13-CD28-41BBzeta CAR exhibited augmented/sustained MAPK and AKT activity, up-regulated Th1 cytokine production, and enhanced cytolytic potency against tumor targets. Moreover, upon recursive stimulation with tumor, the IL13-CD28-41BBzeta+ cells retained/recycled their lytic function, whereas IL-13zeta+ CD4+ cells became anergic/exhausted. These in vitro observations correlated with enhanced in vivo control of established orthotopic CNS glioma xenografts in immunodeficient mice mediated by adoptively transferred ex vivo-expanded CD4+ T cells expressing the co-stimulatory CAR. Discussion Together these studies demonstrate the importance of integrating co-stimulation with CD3zeta signaling events to activate fully CD4+ anti-tumor effector cells for sustained function in the tumor microenvironment.

Medulloblastomas expressing IL13Ralpha2 are targets for IL13-zetakine+ cytolytic T cells

Central nervous system loco-regional disease relapse is a common etiology of treatment failure for medulloblastoma (MB)/primitive neuroectodermal tumors. Therapeutic targeting of primary disease and the adjacent craniospinal cerebral spinal fluid pathways should decrease relapse rates and allow for the curtailed use of radiation therapy. The adoptive transfer of tumor-specific cytolytic T cells (CTLs) to the tumor bed and cerebral spinal fluid is an attractive strategy, but limited in its clinical application owing to the paucity of defined antigens consistently expressed by these tumors and their potential to escape T-cell recognition by expressing low level surface human leukocyte antigen. Here, we describe the human leukocyte antigen-independent recognition of MB cell-surface IL13Ralpha2 by genetically modified CTLs expressing an IL13-zetakine chimeric immunoreceptor. We found that IL13-zetakine+ CTLs exhibit potent cytolytic activity toward IL13Ralpha2 Daoy cells, and are activated to secrete proinflammatory cytokines such as interferon-gamma. By employing an orthotopic NOD-scid murine model in which intraventricularly seeded Daoy cells form tumors on leptomeningeal surfaces, regression of established ffLuc+ Daoy xenografts in response to intraventricularly delivered IL13-zetakine+ CD8+ CTLs was observed using biophotonic imaging. These studies support the rationale for exploring the clinical utility of targeted immunotherapy using adoptively transferred IL13-zetakine redirected CTLs as a therapeutic component for treating IL13Ralpha2+ MB/primitive neuroectodermal tumors.

Tumor-Derived Chemokine MCP-1/CCL2 Is Sufficient for Mediating Tumor Tropism of Adoptively Transferred T Cells

To exert a therapeutic effect, adoptively transferred tumor-specific CTLs must traffic to sites of tumor burden, exit the circulation, and infiltrate the tumor microenvironment. In this study, we examine the ability of adoptively transferred human CTL to traffic to tumors with disparate chemokine secretion profiles independent of tumor Ag recognition. Using a combination of in vivo tumor tropism studies and in vitro biophotonic chemotaxis assays, we observed that cell lines derived from glioma, medulloblastoma, and renal cell carcinoma efficiently chemoattracted ex vivo-expanded primary human T cells. We compared the chemokines secreted by tumor cell lines with high chemotactic activity with those that failed to elicit T cell chemotaxis (Daudi lymphoma, 10HTB neuroblastoma, and A2058 melanoma cells) and found a correlation between tumor-derived production of MCP-1/CCL2 (> or =10 ng/ml) and T cell chemotaxis. Chemokine immunodepletion studies confirmed that tumor-derived MCP-1 elicits effector T cell chemotaxis. Moreover, MCP-1 is sufficient for in vivo T cell tumor tropism as evidenced by the selective accumulation of i.v. administered firefly luciferase-expressing T cells in intracerebral xenografts of tumor transfectants secreting MCP-1. These studies suggest that the capacity of adoptively transferred T cells to home to tumors may be, in part, dictated by the species and amounts of tumor-derived chemokines, in particular MCP-1.

Role of hematopoietic stem cell transplantation for advanced-stage diffuse large cell B-cell lymphoma-B

The prognosis of patients with relapsed or refractory diffuse large cell B-cell lymphoma-B (DLCL-B) is poor with conventional salvage chemotherapy; therefore, high-dose therapy (HDT) combined with autologous stem cell transplant (ASCT) has become the treatment of choice for these patients. The outcomes of transplant are better in patients with chemosensitive relapse: those with a longer duration of first remission (>12 month) and those with an age-adjusted low-risk International Prognostic Index (IPI) at relapse. Several high-dose regimens with or without total body irradiation (TBI) have been used with similar outcomes. Relapse remains the most common cause of treatment failure, and thus the use of radioimmunotherapy (RIT) in the high-dose regimens and incorporation of rituximab in the transplant setting have been explored. Several studies have shown that RIT both at conventional dose and at high dose can be given in combination with high-dose chemotherapy regimens without additional toxicity or delay in hematopoietic recovery after ASCT. Additional studies using RIT in combination with high-dose chemotherapy and ASCT are ongoing, and preliminary results suggest that these approaches may be superior to conventional high-dose regimens. Since rituximab is an effective therapy for B-cell non-Hodgkin's lymphoma and given its limited toxicity, rituximab has been incorporated into HDT and ASCT for DLCL-B as in vivo purging, as part of high-dose regimens, and as maintenance therapy to prevent relapse. Preliminary results suggested that rituximab during ASCT and as maintenance therapy post-transplant reduces the risk of relapse and improves survival; however, these results need to be confirmed in phase III randomized trials. The role of ASCT during first remission as consolidative therapy in patients with DLCL-B remains controversial and should not be performed outside of the clinical trial setting. Allogeneic stem cell transplant (allo-SCT) for patients with relapsed DLCL-B is associated with significant toxicity and should be reserved for patients who relapse after ASCT or those with persistent marrow involvement. Innovative approaches are needed for primary refractory and chemoresistant relapsed DLCL-B since these patients have very poor outcomes after ASCT.

Conversion of a tumor-binding peptide identified by phage display to a functional chimeric T cell antigen receptor

Adoptive transfer of ex vivo expanded tumor-specific T cells is a promising therapeutic modality for promoting or augmenting antitumor immunity. Several groups, including ours, are developing antigen receptor gene transfer strategies as a means of generating effector cells for adoptive therapy. Chimeric antigen receptors (CARs) have been described that use single-chain antibodies or cytokine ligands as tumor targeting domains. Here, we describe the capacity of a tumor-binding peptide identified by phage display combinatorial library screening to serve as a CAR targeting domain. A phage library-selected high-affinity 12-mer peptide (Bpep) specific for alpha(v) beta(6) integrin (alpha v beta6) was chosen for these studies. Primary human T cells were genetically modified to express the Bpep-CAR consisting of an alpha v beta6-specific peptide and human IgG4 hinge-Fc extracellular domain fused to the cytoplasmic tail of CD3-zeta. T cell expression of the Bpep-CAR was assessed by Western blot analysis, and trafficking of the Bpep-CAR to the cell surface was demonstrated by flow cytometry. Functionally, Bpep-CAR redirected cytotoxic T lymphocytes specifically kill integrin alpha v beta6+ ovarian tumor targets, and are activated for interferon gamma secretion. Our data suggest that large new repertoires of tumor-specific T cell antigen receptor transgenes might be available through merging combinatorial peptide libraries with CAR construct design.

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.