Target antigen expression on a professional antigen-presenting cell induces superior proliferative antitumor T-cell responses via chimeric T-cell receptors

Adoptive Immunotherapy for B-cell Malignancies Using CD19- Targeted Chimeric Antigen Receptor T-Cells: A Systematic Review of Efficacy and Safety

BACKGROUND

Adoptive infusion of chimeric antigen receptor transduced T- cells (CAR-T) is a powerful tool of immunotherapy for hematological malignancies, as evidenced by recently published and unpublished clinical results.

OBJECTIVE

In this report, we performed a meta-analysis to evaluate the efficacy and side effects of CAR-T on refractory and/or relapsed B-cell malignancies, including leukemia and lymphoma.

METHODS

Clinical studies investigating efficacy and safety of CAR-T in acute and chronic lymphocytic leukemia and lymphoma were identified by searching PubMed and EMBASE. Outcomes of efficacy subjected to analysis were the rates of complete remission (CR) and partial remission (PR). The safety parameters were the prevalence of adverse effects including fever, hypotension, and acute renal failure. Meta analyses were performed using R software. Weighted hazard ratio (HR) with 95% confidence intervals was calculated for each outcome. Fixed or random-effects models were employed depending on the heterogeneity across the included studies.

RESULTS

Nineteen published clinical studies with a total of 391 patients were included for the meta-analysis. The pooled rate of complete remission was 55% (95% CI 41%-69%); the pooled rate of partial remission was 25% (95% CI: 19%-33%). The prevalence of fever was 62% (95% CI: 41%-79%), the hypotension was 22% (95% CI: 15%-31%), and the acute renal failure was 24% (95% CI: 16%-34%). All adverse effects were manageable and no death was reported due to toxicity.

CONCLUSION

CD19-targeted CAR-T is an effective modality in treating refractory B-cell malignancies including leukemia and lymphoma. However, there is still a need to develop strategies to improve the safety in its clinical use.

Chimeric Antigen Receptor Signaling Domains Differentially Regulate Proliferation and Native T Cell Receptor Function in Virus-Specific T Cells

The efficacy of T cells expressing chimeric antigen receptors (CARs) for solid tumors has been limited by insufficient CAR T cell expansion and persistence. The use of virus-specific T cells (VSTs) as carriers for CARs may overcome this limitation since CAR-VSTs can be boosted by viral vaccines or oncolytic viruses. However, there is limited understanding of the optimal combination of endodomains and their influence on the native T cell receptor (TCR) in VSTs. We therefore compared the function of GD2.CARs expressing the TCR zeta chain (ζ) alone or combined with endodomains from CD28 and 4-1BB in varicella zoster virus-specific (VZV) T cells. VZVSTs expressing GD2-CARs recognized VZV-derived peptides and killed GD2-expressing tumor cells. However, after repeated stimulation through their native TCR, the expansion of GD2-CAR.CD28ζ-VZVSTs was 3.3-fold greater (p < 0.001) than non-transduced VZVSTs, whereas GD2-CARζ- and GD2-CAR.41BBζ inhibited VZVST expansion (p < 0.01). Compared to control VZVSTs, GD2-CAR.ζ VZVSTs showed a greater frequency of apoptotic (p < 0.01) T cells, whereas prolonged downregulation of the native αβ TCR was observed in GD2-CAR.41BBζ VZVSTs (p < 0.001). We confirmed that CD28ζ can best maintain TCR function by expressing GD2.CARs in Epstein-Barr virus-specific T cells and CD19-CARs in VZVSTs. In response to CAR stimulation VSTs with CD28ζ endodomains also showed the greatest expansion (6 fold > GD2-CAR.41BBζ VZVSTs (p < 0.001), however anti-tumor efficacy was superior in GD2-CAR.41BBζ-VZVSTs. These findings demonstrate that CAR signaling domains can enhance or diminish the function of the native TCR and indicate that only CD28ζ may preserve the function of the native TCR in tonically signaling CAR-VSTs.

Early transduction produces highly functional chimeric antigen receptor-modified virus-specific T-cells with central memory markers: a Production Assistant for Cell Therapy (PACT) translational application

BACKGROUND

Virus-specific T-cells (VSTs) proliferate exponentially after adoptive transfer into hematopoietic stem cell transplant (HSCT) recipients, eliminate virus infections, then persist and provide long-term protection from viral disease. If VSTs behaved similarly when modified with tumor-specific chimeric antigen receptors (CARs), they should have potent anti-tumor activity. This theory was evaluated by Cruz et al. in a previous clinical trial with CD19.CAR-modified VSTs, but there was little apparent expansion of these cells in patients. In that study, VSTs were gene-modified on day 19 of culture and we hypothesized that by this time, sufficient T-cell differentiation may have occurred to limit the subsequent proliferative capacity of the transduced T-cells. To facilitate the clinical testing of this hypothesis in a project supported by the NHLBI-PACT mechanism, we developed and optimized a good manufacturing practices (GMP) compliant method for the early transduction of VSTs directed to Epstein-Barr virus (EBV), Adenovirus (AdV) and cytomegalovirus (CMV) using a CAR directed to the tumor-associated antigen disialoganglioside (GD2).

RESULTS

Ad-CMVpp65-transduced EBV-LCLs effectively stimulated VSTs directed to all three viruses (triVSTs). Transduction efficiency on day three was increased in the presence of cytokines and high-speed centrifugation of retroviral supernatant onto retronectin-coated plates, so that under optimal conditions up to 88% of tetramer-positive VSTs expressed the GD2.CAR. The average transduction efficiency of early-and late transduced VSTs was 55 ± 4% and 22 ± 5% respectively, and early-transduced VSTs maintained higher frequencies of T cells with central memory or intermediate memory phenotypes. Early-transduced VSTs also had higher proliferative capacity and produced higher levels of TH1 cytokines IL-2, TNF-α, IFN-γ, MIP-1α, MIP-1β and other cytokines in vitro.

CONCLUSIONS

We developed a rapid and GMP compliant method for the early transduction of multivirus-specific T-cells that allowed stable expression of high levels of a tumor directed CAR. Since a proportion of early-transduced CAR-VSTs had a central memory phenotype, they should expand and persist in vivo, simultaneously protecting against infection and targeting residual malignancy. This manufacturing strategy is currently under clinical investigation in patients receiving allogeneic HSCT for relapsed neuroblastoma and B-cell malignancies (NCT01460901 using a GD2.CAR and NCT00840853 using a CD19.CAR).

Treating B-cell cancer with T cells expressing anti-CD19 chimeric antigen receptors

Most B-cell malignancies express CD19, and a majority of patients with B-cell malignancies are not cured by current standard therapies. Chimeric antigen receptors (CARs) are fusion proteins consisting of antigen recognition moieties and T-cell activation domains. T cells can be genetically modified to express CARs, and adoptive transfer of anti-CD19 CAR T cells is now being tested in clinical trials. Effective clinical treatment with anti-CD19 CAR T cells was first reported in 2010 after a patient with advanced-stage lymphoma treated at the NCI experienced a partial remission of lymphoma and long-term eradication of normal B cells. Additional patients have subsequently obtained long-term remissions of advanced-stage B-cell malignancies after infusions of anti-CD19 CAR T cells. Long-term eradication of normal CD19(+) B cells from patients receiving infusions of anti-CD19 CAR T cells demonstrates the potent antigen-specific activity of these T cells. Some patients treated with anti-CD19 CAR T cells have experienced acute adverse effects, which were associated with increased levels of serum inflammatory cytokines. Although anti-CD19 CAR T cells are at an early stage of development, the potent antigen-specific activity observed in patients suggests that infusions of anti-CD19 CAR T cells might become a standard therapy for some B-cell malignancies.

Immunotherapy of malignant disease using chimeric antigen receptor engrafted T cells

Chimeric antigen receptor- (CAR-) based immunotherapy has been under development for almost 25 years, over which period it has progressed from a new but cumbersome technology to an emerging therapeutic modality for malignant disease. The approach involves the genetic engineering of fusion receptors (CARs) that couple the HLA-independent binding of cell surface target molecules to the delivery of a tailored activating signal to host immune cells. Engineered CARs are delivered most commonly to peripheral blood T cells using a range of vector systems, most commonly integrating viral vectors. Preclinical refinement of this approach has proceeded over several years to the point that clinical testing is now being undertaken at several centres, using increasingly sophisticated and therapeutically successful genetic payloads. This paper considers several aspects of the pre-clinical and clinical development of CAR-based immunotherapy and how this technology is acquiring an increasing niche in the treatment of both solid and haematological malignancies.

The ganglioside antigen G(D2) is surface-expressed in Ewing sarcoma and allows for MHC-independent immune targeting

Background:

Novel treatment strategies are needed to cure disseminated Ewing sarcoma. Primitive neuroectodermal features and a mesenchymal stem cell origin are both compatible with aberrant expression of the ganglioside antigen G_D2 and led us to explore G_D2 immune targeting in this cancer.

Methods:

We investigated G_D2 expression in Ewing sarcoma by immunofluorescence staining. We then assessed the antitumour activity of T cells expressing a chimeric antigen receptor specific for G_D2 against Ewing sarcoma in vitro and in vivo.

Results:

Surface G_D2 was detected in 10 out of 10 Ewing sarcoma cell lines and 3 out of 3 primary cell cultures. Moreover, diagnostic biopsies from 12 of 14 patients had uniform G_D2 expression. T cells specifically modified to express the G_D2-specific chimeric receptor 14. G2a-28ζ efficiently interacted with Ewing sarcoma cells, resulting in antigen-specific secretion of cytokines. Moreover, chimeric receptor gene-modified T cells from healthy donors and from a patient exerted potent, G_D2-specific cytolytic responses to allogeneic and autologous Ewing sarcoma, including tumour cells grown as multicellular, anchorage-independent spheres. G_D2-specific T cells further had activity against Ewing sarcoma xenografts.

Conclusion:

G_D2 surface expression is a characteristic of Ewing sarcomas and provides a suitable target antigen for immunotherapeutic strategies to eradicate micrometastatic cells and prevent relapse in high-risk disease.

B-cell depletion and remissions of malignancy along with cytokine-associated toxicity in a clinical trial of anti-CD19 chimeric-antigen-receptor-transduced T cells

We conducted a clinical trial to assess adoptive transfer of T cells genetically modified to express an anti-CD19 chimeric Ag receptor (CAR). Our clinical protocol consisted of chemotherapy followed by an infusion of anti-CD19-CAR-transduced T cells and a course of IL-2. Six of the 8 patients treated on our protocol obtained remissions of their advanced, progressive B-cell malignancies. Four of the 8 patients treated on the protocol had long-term depletion of normal polyclonal CD19(+) B-lineage cells. Cells containing the anti-CD19 CAR gene were detected in the blood of all patients. Four of the 8 treated patients had prominent elevations in serum levels of the inflammatory cytokines IFNγ and TNF. The severity of acute toxicities experienced by the patients correlated with serum IFNγ and TNF levels. The infused anti-CD19-CAR-transduced T cells were a possible source of these inflammatory cytokines because we demonstrated peripheral blood T cells that produced TNF and IFNγ ex vivo in a CD19-specific manner after anti-CD19-CAR-transduced T-cell infusions. Anti-CD19-CAR-transduced T cells have great promise to improve the treatment of B-cell malignancies because of a potent ability to eradicate CD19(+) cells in vivo; however, reversible cytokine-associated toxicities occurred after CAR-transduced T-cell infusions.

Antitumor activity and long-term fate of chimeric antigen receptor-positive T cells in patients with neuroblastoma

We generated MHC-independent chimeric antigen receptors (CARs) directed to the GD2 antigen expressed by neuroblastoma tumor cells and treated patients with this disease. Two distinguishable forms of this CAR were expressed in EBV-specific cytotoxic T lymphocytes (EBV-CTLs) and activated T cells (ATCs). We have previously shown that EBV-CTLs expressing GD2-CARs (CAR-CTLs) circulated at higher levels than GD2-CAR ATCs (CAR-ATCs) early after infusion, but by 6 weeks, both subsets became low or undetectable. We now report the long-term clinical and immunologic consequences of infusions in 19 patients with high-risk neuroblastoma: 8 in remission at infusion and 11 with active disease. Three of 11 patients with active disease achieved complete remission, and persistence of either CAR-ATCs or CAR-CTLs beyond 6 weeks was associated with superior clinical outcome. We observed persistence for up to 192 weeks for CAR-ATCs and 96 weeks for CAR-CTLs, and duration of persistence was highly concordant with the percentage of CD4(+) cells and central memory cells (CD45RO(+)CD62L(+)) in the infused product. In conclusion, GD2-CAR T cells can induce complete tumor responses in patients with active neuroblastoma; these CAR T cells may have extended, low-level persistence in patients, and such persistence was associated with longer survival. This study is registered at www.clinialtrials.gov as #NCT00085930.

Adoptive transfer of syngeneic T cells transduced with a chimeric antigen receptor that recognizes murine CD19 can eradicate lymphoma and normal B cells

Adoptive T-cell therapy with anti-CD19 chimeric antigen receptor (CAR)-expressing T cells is a new approach for treating advanced B-cell malignancies. To evaluate anti-CD19-CAR-transduced T cells in a murine model of adoptive T-cell therapy, we developed a CAR that specifically recognized murine CD19. We used T cells that were retrovirally transduced with this CAR to treat mice bearing a syngeneic lymphoma that naturally expressed the self-antigen murine CD19. One infusion of anti-CD19-CAR-transduced T cells completely eliminated normal B cells from mice for at least 143 days. Anti-CD19-CAR-transduced T cells eradicated intraperitoneally injected lymphoma cells and large subcutaneous lymphoma masses. The antilymphoma efficacy of anti-CD19-CAR-transduced T cells was critically dependent on irradiation of mice before anti-CD19-CAR-transduced T-cell infusion. Anti-CD19-CAR-transduced T cells had superior antilymphoma efficacy compared with the anti-CD19 monoclonal antibody from which the anti-CD19 CAR was derived. Our results demonstrated impressive antilymphoma activity and profound destruction of normal B cells caused by anti-CD19-CAR-transduced T cells in a clinically relevant murine model.

Chimeric antigen receptor-engineered T cells for immunotherapy of cancer

CD4⁺ and CD8⁺ T lymphocytes are powerful components of adaptive immunity, which essentially contribute to the elimination of tumors. Due to their cytotoxic capacity, T cells emerged as attractive candidates for specific immunotherapy of cancer. A promising approach is the genetic modification of T cells with chimeric antigen receptors (CARs). First generation CARs consist of a binding moiety specifically recognizing a tumor cell surface antigen and a lymphocyte activating signaling chain. The CAR-mediated recognition induces cytokine production and tumor-directed cytotoxicity of T cells. Second and third generation CARs include signal sequences from various costimulatory molecules resulting in enhanced T-cell persistence and sustained antitumor reaction. Clinical trials revealed that the adoptive transfer of T cells engineered with first generation CARs represents a feasible concept for the induction of clinical responses in some tumor patients. However, further improvement is required, which may be achieved by second or third generation CAR-engrafted T cells.

Genetic redirection of T cells for cancer therapy

Adoptive immunotherapy can induce dramatic tumor regressions in patients with melanoma or viral-induced malignancies, but extending this approach to many common cancers has been hampered by a lack of naturally occurring tumor-specific T cells. In this review, we describe recent advances in the genetic modification of T cells using genes encoding cell-surface receptors specific for tumor-associated antigen. Using genetic modification, the many functional properties of T cells, including cytokine secretion and cytolytic capacity, are redirected from their endogenous specificity toward the elimination of tumor cells. Advances in gene design, vectors, and cell production are discussed, and details of the progress in clinical application of this approach are provided.

2B4 (CD244) signaling via chimeric receptors costimulates tumor-antigen specific proliferation and in vitro expansion of human T cells

Regulatory NK cell receptors can contribute to antigen-specific adaptive immune responses by modulating T cell receptor (TCR)-induced T cell activation. We investigated the potential of the NK cell receptor 2B4 (CD244) to enhance tumor antigen-induced activation of human T cells. 2B4 is a member of the CD2 receptor subfamily with both activating and inhibitory functions in NK cells. In T cells, its expression is positively associated with the acquisition of a cytolytic effector memory phenotype. Recombinant chimeric receptors that link extracellular single-chain Fv fragments specific for the tumor-associated surface antigens CD19 and G(D2) to the signaling domains of human 2B4 and/or TCRzeta were expressed in non-specifically activated peripheral blood T cells by retroviral gene transfer. While 2B4 signaling alone failed to induce T cell effector functions or proliferation, it significantly augmented the antigen-specific activation responses induced by TCRzeta. 2B4 costimulation did not affect the predominant effector memory phenotype of expanding T cells, nor did it increase the proportion of T cells with regulatory phenotype (CD4+CD25(hi)FoxP3+). These data support a costimulatory role for 2B4 in human T cell subpopulations. As an amplifier of TCR-mediated signals, 2B4 may provide a powerful new tool for immunotherapy of cancer, promoting sustained activation and proliferation of gene-modified antitumor T cells.

Construction and preclinical evaluation of an anti-CD19 chimeric antigen receptor

T cells can be engineered to express the genes of chimeric antigen receptors (CARs) that recognize tumor-associated antigens. We constructed and compared 2 CARs that contained a single chain variable region moiety that recognized CD19. One CAR contained the signaling moiety of the 4-1BB molecule and the other did not. We selected the CAR that did not contain the 4-1BB moiety for further preclinical development. We demonstrated that gammaretroviruses encoding this receptor could transduce human T cells. Anti-CD19-CAR-transduced CD8+ and CD4+ T cells produced interferon-gamma and interleukin-2 specifically in response to CD19+ target cells. The transduced T cells specifically killed primary chronic lymphocytic leukemia (CLL) cells. We transduced T cells from CLL patients that had been previously treated with chemotherapy. We induced these T cells to proliferate sufficiently to provide enough cells for clinical adoptive T cell transfer with a protocol consisting of an initial stimulation with an anti-CD3 monoclonal antibody (OKT3) before transduction followed by a second OKT3 stimulation 7 days after transduction. This protocol was successfully adapted for use in CLL patients with high peripheral blood leukemia cell counts by depleting CD19+ cells before the initial OKT3 stimulation. In preparation for a clinical trial that will enroll patients with advanced B cell malignancies, we generated a producer cell clone that produces retroviruses encoding the anti-CD19 CAR, and we produced sufficient retroviral supernatant for the proposed clinical trial under good manufacturing practice conditions.

Virus-specific T cells engineered to coexpress tumor-specific receptors: persistence and antitumor activity in individuals with neuroblastoma

Cytotoxic T lymphocytes (CTLs) directed to nonviral tumor-associated antigens do not survive long term and have limited antitumor activity in vivo, in part because such tumor cells typically lack the appropriate costimulatory molecules. We therefore engineered Epstein-Barr virus (EBV)-specific CTLs to express a chimeric antigen receptor directed to the diasialoganglioside GD2, a nonviral tumor-associated antigen expressed by human neuroblastoma cells. We reasoned that these genetically engineered lymphocytes would receive optimal costimulation after engagement of their native receptors, enhancing survival and antitumor activity mediated through their chimeric receptors. Here we show in individuals with neuroblastoma that EBV-specific CTLs expressing a chimeric GD2-specific receptor indeed survive longer than T cells activated by the CD3-specific antibody OKT3 and expressing the same chimeric receptor but lacking virus specificity. Infusion of these genetically modified cells seemed safe and was associated with tumor regression or necrosis in half of the subjects tested. Hence, virus-specific CTLs can be modified to function as tumor-directed effector cells.

The combination of cyclophosphamide and human T cells genetically engineered to target CD19 can eradicate established B-cell lymphoma

T cells genetically engineered to express tumour-targeting receptors are attractive anti-cancer therapeutic agents. Human T cells engrafted with a chimeric receptor specific for the B-cell lymphoma antigen CD19 fused to the CD3zeta receptor (aCD19z) are functional in vitro. Current successful clinical protocols targeting melanoma use pre-conditioning chemotherapy in combination with T cells. This study demonstrated that interleukin-2 expanded aCD19z T cells combined with cyclophosphamide effectively treated five-day established Raji B-cell lymphoma in an immunocompromised model system with 50% of mice surviving >100 days. This observation strongly supports the combination of antibody targeted T cells with chemotherapy as a novel approach for the therapy of CD19(+) B-cell malignancies.

The continuing contribution of gene marking to cell and gene therapy

Gene-marking studies were the first gene-transfer protocols approved for human use. Their intent was not directly therapeutic but rather to track the behavior and fate of cells in vivo, and to use this information to improve treatment protocols. For more than fifteen years, gene-marking studies using retroviral vectors have provided invaluable information about the biology of human hematopoietic cells and T lymphocytes, and have helped guide cell therapies intended to treat malignant disease. Although the safety record of marking studies has been impeccable, the development of leukemia by immunodeficient children treated with retroviral vectors cast a pall over the entire field and essentially brought the era of pure gene-marking studies to an abrupt end. Paradoxically, the impetus these events gave to studying retroviral integration sites in host cell DNA emphasized the additional information that marker studies could provide about the behavior of cells at the clonal level. As confidence has slowly returned, marker studies have reappeared, usually as components of gene therapy protocols in which a marker gene or sequence is incorporated to allow the modified cells to be tracked or imaged in vivo. Hence, gene marking continues to have much to offer in terms of our understanding of the behavior, fate, and safety of gene-modified cells in vivo.

Sleeping beauty transposon-mediated nonviral gene therapy

Safe and effective delivery of genetic material to mammalian tissues would significantly expand the therapeutic possibilities for a large number of medical conditions. Unfortunately, the promise of gene therapy has been hampered by technical challenges, the induction of immune responses, and inadequate expression over time. Despite these setbacks, progress continues to be made and the anticipated benefits may come to fruition for certain disorders. In terms of delivery, nonviral vector systems are particularly attractive as they are simple to produce, can be stored for long periods of time, and induce no specific immune responses. A significant drawback to nonviral systems has been the lack of persistent expression, as plasmids are lost or degraded when delivered to living tissues. The recent application of integrating transposons to nonviral gene delivery has significantly helped to overcome this obstacle, because it allows for genomic integration and long-term expression. Recent advances in transposon-based vector systems hold promise as new technologies that may unlock the potential of gene therapy; however, technical and safety issues still need refinement.

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.

CD28 co-stimulation via tumour-specific chimaeric receptors induces an incomplete activation response in Epstein-Barr virus-specific effector memory T cells

Expression of tumour antigen-specific chimaeric receptors in T lymphocytes can redirect their effector functions towards tumour cells. Integration of the signalling domains of the co-stimulatory molecule CD28 into chRec enhances antigen-specific proliferation of polyclonal human T cell populations. While CD28 plays an essential role in the priming of naive CD4(+) T cells, its contribution to effector memory T cell responses is controversial. We compared the function of the chRec with and without the CD28 co-stimulatory domain, expressing it in peripheral blood T cells or Epstein-Barr virus (EBV)-specific T cell lines. The chimaeric T cell receptors contain an extracellular single-chain antibody domain, to give specificity against the tumour ganglioside antigen G(D2). The transduced cytotoxic T lymphocytes (CTL) maintained their specificity for autologous EBV targets and their capacity to proliferate after stimulation with EBV-infected B cells. Intracellular cytokine staining demonstrated efficient and comparable antigen-specific interferon (IFN)-gamma secretion by CTL following engagement of both the native and the chimaeric receptor, independent of chimaeric CD28 signalling. Furthermore, tumour targets were lysed in an antigen-specific manner by both chRec. However, while antigen engagement by CD28 zeta chRec efficiently induced expansion of polyclonal peripheral blood lymphocytes in an antigen-dependent manner, CD28 signalling did not induce proliferation of EBV-CTL in response to antigen-expressing tumour cells. Thus, the co-stimulatory requirement for the efficient activation response of antigen-specific memory cells cannot be mimicked simply by combining CD28 and zeta signalling. The full potential of this highly cytolytic T cell population for adoptive immunotherapy of cancer requires further exploration of their co-stimulatory requirements.