Natural expression of the CD19 antigen impacts the long-term engraftment but not antitumor activity of CD19-specific engineered T cells

Lymphodepletion - an essential but undervalued part of the chimeric antigen receptor T-cell therapy cycle

Lymphodepletion (LD) or conditioning is an essential step in the application of currently used autologous and allogeneic chimeric antigen receptor T-cell (CAR-T) therapies as it maximizes engraftment, efficacy and long-term survival of CAR-T. Its main modes of action are the depletion and modulation of endogenous lymphocytes, conditioning of the microenvironment for improved CAR-T expansion and persistence, and reduction of tumor load. However, most LD regimens provide a broad and fairly unspecific suppression of T-cells as well as other hematopoietic cells, which can also lead to severe side effects, particularly infections. We reviewed 1271 published studies (2011-2023) with regard to current LD strategies for approved anti-CD19 CAR-T products for large B cell lymphoma (LBCL). Fludarabine (Flu) and cyclophosphamide (Cy) (alone or in combination) were the most commonly used agents. A large number of different schemes and combinations have been reported. In the respective schemes, doses of Flu and Cy (range 75-120mg/m2 and 750-1.500mg/m2) and wash out times (range 2-5 days) differed substantially. Furthermore, combinations with other agents such as bendamustine (benda), busulfan or alemtuzumab (for allogeneic CAR-T) were described. This diversity creates a challenge but also an opportunity to investigate the impact of LD on cellular kinetics and clinical outcomes of CAR-T. Only 21 studies explicitly investigated in more detail the influence of LD on safety and efficacy. As Flu and Cy can potentially impact both the in vivo activity and toxicity of CAR-T, a more detailed analysis of LD outcomes will be needed before we are able to fully assess its impact on different T-cell subsets within the CAR-T product. The T2EVOLVE consortium propagates a strategic investigation of LD protocols for the development of optimized conditioning regimens.

Applying a Clinical Lens to Animal Models of CAR-T Cell Therapies

Chimeric antigen receptor (CAR)-T cells have emerged as a promising treatment modality for various hematologic and solid malignancies over the past decade. Animal models remain the cornerstone of pre-clinical evaluation of human CAR-T cell products and are generally required by regulatory agencies prior to clinical translation. However, pharmacokinetics and pharmacodynamics of adoptively transferred T cells are dependent on various recipient factors, posing challenges for accurately predicting human engineered T cell behavior in non-human animal models. For example, murine xenograft models did not forecast now well-established cytokine-driven systemic toxicities of CAR-T cells seen in humans, highlighting the limitations of animal models that do not perfectly recapitulate complex human immune systems. Understanding the concordance as well as discrepancies between existing pre-clinical animal data and human clinical experiences, along with established advantages and limitations of each model, will facilitate investigators’ ability to appropriately select and design animal models for optimal evaluation of future CAR-T cell products. We summarize the current state of animal models in this field, and the advantages and disadvantages of each approach depending on the pre-clinical questions being asked.

Leukemia's Next Top Model? Syngeneic Models to Advance Adoptive Cellular Therapy

In recent years, there has been an emphasis on harnessing the immune system for therapeutic interventions. Adoptive cell therapies (ACT) have emerged as an effective option for B-cell derived hematological malignancies. Despite remarkable successes with ACT, immune dysregulation and the leukemia microenvironment can critically alter clinical responses. Therefore, preclinical modeling can contribute to the advancement of ACT for leukemias. Human xenografts, the current mainstay of ACT in vivo models, cannot evaluate the impact of the immunosuppressive leukemia microenvironment on adoptively transferred cells. Syngeneic mouse models utilize murine tumor models and implant them into immunocompetent mice. This provides an alternative model, reducing the need for complicated breeding strategies while maintaining a matched immune system, stromal compartment, and leukemia burden. Syngeneic models that evaluate ACT have analyzed the complexity of cytotoxic T lymphocytes, T cell receptor transgenics, and chimeric antigen receptors. This review examines the immunosuppressive features of the leukemia microenvironment, discusses how preclinical modeling helps predict ACT associated toxicities and dysfunction, and explores publications that have employed syngeneic modeling in ACT studies for the improvement of therapy for leukemias.

Associação Brasileira de Hematologia, Hemoterapia e Terapia Celular Consensus on genetically modified cells. VIII: CAR-T cells: preclinical development - Safety and efficacy evaluation

Currently, there are four CAR-T products commercially available on the market. CAR-T cells have shown high remission rates and they represent an effective treatment option for patients with resistant or refractory B cell malignancies. Approval of these cell therapy products came after an extended period of preclinical evaluation that demonstrated unprecedented efficacy in this difficult-to-treat patient population. This review article outlines the main preclinical evaluations needed for CAR T cell product development.

Preclinical pharmacology modeling of chimeric antigen receptor T therapies

Chimeric antigen receptor (CAR) T cells have largely been successful in treating hematological malignancies in the clinic but have not been as effective in treating solid tumors, in part, owing to poor access and the immunosuppressive tumor microenvironment. In addition, CAR-T therapy can cause potentially life-threatening side effects, including cytokine release syndrome and neurotoxicity. Current preclinical testing of CAR-T therapy efficacy is typically performed in mouse tumor models, which often fails to predict toxicity. Recent developments in humanized models and transgenic mice as well as in vitro three-dimensional organoids in early development and nonhuman primate models are being adopted for CAR-T cell efficacy and toxicity assessment. However, because no single model perfectly recapitulates the human immune system and tumor microenvironment, careful model selection based on their respective pros and cons is crucial for adequate evaluation of different CAR-T treatments, so that their clinical development can be better supported.

Anti-CD19 CAR T Cells That Secrete a Biparatopic Anti-CLEC12A Bridging Protein Have Potent Activity Against Highly Aggressive Acute Myeloid Leukemia In Vitro and In Vivo

Refractory acute myeloid leukemia (AML) remains an incurable malignancy despite the clinical use of novel targeted therapies, new antibody-based therapies, and cellular therapeutics. Here, we describe the preclinical development of a novel cell therapy that targets the antigen CLEC12A with a biparatopic bridging protein. Bridging proteins are designed as "CAR-T cell engagers," with a CAR-targeted protein fused to antigen binding domains derived from antibodies. Here, we created a CD19-anti-CLEC12A bridging protein that binds to CAR19 T cells and to the antigen CLEC12A. Biparatopic targeting increases the potency of bridging protein-mediated cytotoxicity by CAR19 T cells. Using CAR19 T cells that secrete the bridging protein we demonstrate potent activity against aggressive leukemic cell lines in vivo This CAR-engager platform is facile and modular, as illustrated by activity of a dual-antigen bridging protein targeting CLEC12A and CD33, designed to counter tumor heterogeneity and antigen escape, and created without the need for extensive CAR T-cell genetic engineering. CAR19 T cells provide an optimal cell therapy platform with well-understood inherent persistence and fitness characteristics.

Therapeutic efficacy of anti-CD19 CAR-T cells in a mouse model of systemic lupus erythematosus

Dysregulated B-cell activation plays pivotal roles in systemic lupus erythematosus (SLE), which makes B-cell depletion a potential strategy for SLE treatment. The clinical success of anti-CD19 CAR-T cells in treating B-cell malignancies has attracted the attention of researchers. In this study, we aimed to investigate the feasibility of applying anti-CD19 CAR-T cell therapy to SLE treatment in a mouse disease model. We constructed murine anti-CD19 CARs with either CD28 or 4-1BB as the intracellular costimulatory motif and evaluated the therapeutic function of the corresponding CAR-T cells by infusing them into MRL-lpr mice. Furthermore, anti-CD19 CAR-T cells were transferred to MRL-lpr mice before the onset of disease to determine their role in SLE prevention. According to our observations, compared with antibody treatment, the adoptive transfer of our anti-CD19 CAR-T cells showed a more sustained B-cell-depletion effect in MRL-lpr mice. The transfer of syngeneic anti-CD19 CAR-T cells not only prevented disease pathogenesis before the onset of disease symptoms but also displayed therapeutic benefits at a later stage after disease progression. We also tried to optimize the treatment strategy and found that compared with CAR-T cells with the CD28 costimulatory motif, CAR-T cells with the 4-1BB costimulatory motif showed better therapeutic efficiency without cell enrichment. Taken together, these results show that anti-CD19 CAR-T cell therapy was effective in the prevention and treatment of a murine model of SLE, indicating its potential for clinical use in patients.

Anti-CD19 CAR T cells potently redirected to kill solid tumor cells

Successful CAR T cell therapy for the treatment of solid tumors requires exemplary CAR T cell expansion, persistence and fitness, and the ability to target tumor antigens safely. Here we address this constellation of critical attributes for successful cellular therapy by using integrated technologies that simplify development and derisk clinical translation. We have developed a CAR-CD19 T cell that secretes a CD19-anti-Her2 bridging protein. This cell therapy strategy exploits the ability of CD19-targeting CAR T cells to interact with CD19 on normal B cells to drive expansion, persistence and fitness. The secreted bridging protein potently binds to Her2-positive tumor cells, mediating CAR-CD19 T cell cytotoxicity in vitro and in vivo. Because of its short half-life, the secreted bridging protein will selectively accumulate at the site of highest antigen expression, ie. at the tumor. Bridging proteins that bind to multiple different tumor antigens have been created. Therefore, antigen-bridging CAR-CD19 T cells incorporate critical attributes for successful solid tumor cell therapy. This platform can be exploited to attack tumor antigens on any cancer.

How do CARs work?: Early insights from recent clinical studies targeting CD19

Second-generation chimeric antigen receptors (CARs) are powerful tools to redirect antigen-specific T cells independently of HLA-restriction. Recent clinical studies evaluating CD19-targeted T cells in patients with B-cell malignancies demonstrate the potency of CAR-engineered T cells. With results from 28 subjects enrolled by five centers conducting studies in patients with chronic lymphocytic leukemia (CLL) or lymphoma, some insights into the parameters that determine T-cell function and clinical outcome of CAR-based approaches are emerging. These parameters involve CAR design, T-cell production methods, conditioning chemotherapy as well as patient selection. Here, we discuss the potential relevance of these findings and in particular the interplay between the adoptive transfer of T cells and pre-transfer patient conditioning.

IL-6 trans-signaling promotes the expansion and anti-tumor activity of CAR T cells

Chimeric antigen receptor (CAR) T cell therapies lead to high clinical response rates in B cell malignancies, and are under investigation for treatment of solid tumors. While high systemic interleukin- (IL-) 6 levels are associated with clinical cytokine release syndrome (CRS), the role of IL-6 trans-signaling within CAR T-cells has not been reported. We generated CAR T cells that constitutively express hyper IL-6 (HIL-6), a designer cytokine that activates the trans-signaling pathway. HIL-6-expressing CAR T-cells exhibited enhanced proliferation and antitumor efficacy in vitro and in xenograft models. However, HIL-6 CAR T cells caused severe graft-versus-host disease (GVHD). Transcriptomic profiling revealed that HIL-6 stimulation of CAR T cells upregulated genes associated with T cell migration, early memory differentiation, and IL-6/GP130/STAT3 signaling. Since IL-6 trans-signaling acts via surface GP130, we generated CAR T cells expressing a constitutively-active form of GP130 and found these retained improved antitumor activity without signs of GVHD in preclinical models of B-cell leukemia and solid tumors. Taken together, these results show that IL-6 trans-signaling can enhance expansion and antitumor activity of CAR T cells via the GP130/STAT3 pathway, and suggest that expression of GP130 within CAR T cells could lead to improved antitumor efficacy without systemic IL-6 trans-signaling.

Chimeric antigen receptor T-cell therapies: Optimising the dose

Lymphocytes such as T-cells can be genetically transduced to express a synthetic chimeric antigen receptor (CAR) that re-directs their cytotoxic activity against a tumour-expressed antigen of choice. Autologous (patient-derived) CAR T-cells have been licensed to treat certain relapsed and refractory B-cell malignancies, and numerous CAR T-cell products are in clinical development. As living gene-modified cells, CAR T-cells exhibit unique pharmacokinetics, typically proliferating within the recipient during the first 14 days after administration before contracting in number, and sometimes exhibiting long-term persistence. The relationship between CAR T-cell dose and exposure is highly variable, and may be influenced by CAR design, patient immune function at the time of T-cell harvest, phenotype of the CAR T-cell product, disease burden, lymphodepleting chemotherapy and subsequent immunomodulatory therapies. Recommended CAR T-cell doses are typically established for a specific product and indication, although for some products, stratification of dose based on disease burden may mitigate toxicity while maintaining efficacy. Re-evaluation of CAR T-cell dosing may be necessary following changes to the lymphodepleting regimen, for different disease indications, and following significant manufacturing changes, if product comparability cannot be demonstrated. Dose escalation trials have typically employed 3 + 3 designs, although this approach has limitations, and alternative phase I trial designs may facilitate the identification of CAR T-cell doses that strike an optimal balance of safety, efficacy and manufacturing feasibility.

Mouse Tumor Models for Advanced Cancer Immunotherapy

Recent advances in the development of new methods of cancer immunotherapy require the production of complex cancer animal models that reliably reflect the complexity of the tumor and its microenvironment. Mice are good animals to create tumor models because they are low cost, have a short reproductive cycle, exhibit high tumor growth rates, and can be easily genetically modified. However, the obvious problem of these models is the high failure rate observed in human clinical trials after promising results obtained in mouse models. In order to increase the reliability of the results obtained in mice, the tumor model should reflect the heterogeneity of the tumor, contain components of the tumor microenvironment, in particular immune cells, to which the action of immunotherapeutic drugs are directed. This review discusses the current immunocompetent and immunocompromised mouse models of human tumors that are used to evaluate the effectiveness of immunotherapeutic agents, in particular chimeric antigen receptor (CAR) T-cells and immune checkpoint inhibitors.

Recent Advancements and Applications of Human Immune System Mice in Preclinical Immuno-Oncology

Significant advances in immunotherapies have resulted in the increasing need of predictive preclinical models to improve immunotherapeutic drug development, treatment combination, and to prevent or minimize toxicity in clinical trials. Immunodeficient mice reconstituted with human immune system (HIS), termed humanized mice or HIS mice, permit detailed analysis of human immune biology, development, and function. Although this model constitutes a great translational model, some aspects need to be improved as the incomplete engraftment of immune cells, graft versus host disease and the lack of human cytokines and growth factors. In this review, we discuss current HIS platforms, their pathology, and recent advances in their development to improve the quality of human immune cell reconstitution. We also highlight new technologies that can be used to better understand these models and how improved characterization is needed for their application in immuno-oncology safety, efficacy, and new modalities therapy development.

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.

Transgenic Tumor Models for Evaluating CAR T-Cell Immunotherapies

Chimeric antigen receptor (CAR) T-cell therapy against tumor antigens involves a recombinant immunoreceptor that combines an antibody-derived targeting fragment with signaling domains capable of activating T cells and fusion of this receptor domain to a costimulatory domain (typically CD28 or 4-1BB). Clinical trials of CAR T-cell therapeutics targeting CD19 antigens for relapsed or refractory B-cell malignancies have shown unparalleled results and consequently have recently been approved by the U.S. Food and Drug Administration. However, the lack of efficacy beyond B-cell malignancies, the emergence of resistance to CAR T-cell therapy due to loss of the antigenic epitope, and severe cases of cytokine release syndrome and neurotoxicity necessitate further preclinical studies. As it is very complicated to develop a single animal model that would replicate the complexity of the clinical scenario, this article focuses on transgenic models used to study human tumor-associated antigens in an immunocompetent model. © 2019 by John Wiley & Sons, Inc.

Single-cell imaging of CAR T cell activity in vivo reveals extensive functional and anatomical heterogeneity

Cazaux et al. use intravital imaging to dissect anti-CD19 CAR T cell activity. This study uncovers both anatomical and functional diversity in the outcome of anti-CD19 CAR T cell interactions with tumor cells impacting engraftment, killing dynamics, and tumor immunoediting.

CAR T cells represent a potentially curative strategy for B cell malignancies. However, the outcome and dynamics of CAR T cell interactions in distinct anatomical sites are poorly understood. Using intravital imaging, we tracked interactions established by anti-CD19 CAR T cells in B cell lymphoma–bearing mice. Circulating targets trapped CAR T cells in the lungs, reducing their access to lymphoid organs. In the bone marrow, tumor apoptosis was largely due to CAR T cells that engaged, killed, and detached from their targets within 25 min. Notably, not all CAR T cell contacts elicited calcium signaling or killing while interacting with tumors, uncovering extensive functional heterogeneity. Mathematical modeling revealed that direct killing was sufficient for tumor regression. Finally, antigen-loss variants emerged in the bone marrow, but not in lymph nodes, where CAR T cell cytotoxic activity was reduced. Our results identify a previously unappreciated level of diversity in the outcomes of CAR T cell interactions in vivo, with important clinical implications.

Opportunities for future therapeutic interventions for hyperoxaluria: targeting oxidative stress

INTRODUCTION

Oxalate is a toxic byproduct of metabolism and is normally produced in quantities easily removed from the body. However, under specific circumstances oxalate production is increased resulting in deposition of calcium oxalate (CaOx) crystals in the kidneys as well as other organs causing inflammation and injury. Excessive buildup of crystal deposits in the kidneys causes eventual loss of renal function requiring renal transplantation. Areas covered: Cellular exposure to CaOx crystals induces the production of reactive oxygen species (ROS) with the involvement of renin-angiotensin aldosterone system (RAAS), mitochondria, and NADPH oxidase. Inflammasomes are activated and pro-inflammatory cytokines, such as IL-1β and IL-18 are produced. We reviewed results of experimental and clinical studies of crystal renal epithelial cell interactions with emphasis on cellular injury and ROS production. Expert opinion: Treatment should depend upon the level of hyperoxaluria and whether it is associated with CaOx crystal deposition. Persistent low grade or intermittent hyperoxaluria can be treated with antioxidants, free radical scavengers. Hyperoxaluria associated with CaOx crystal deposition will require administration of angiotensin II receptor blockers, and NADPH oxidase or NLRP3 inflammasome inhibitors. DASH-style diet will be beneficial in both cases.

Delayed remission following sequential infusion of humanized CD19- and CD22-modified CAR-T cells in a patient with relapsed/refractory acute lymphoblastic leukemia and prior exposure to murine-derived CD19-directed CAR-T cells

Background

CD19-modified CAR-T cells greatly influence responses in patients with relapsed/refractory acute lymphoblastic leukemia (ALL). However, recurrence remains a challenge, and reinfusion of CAR-T cells is not always effective. Sequential infusion of humanized CD19-modified and CD22-modified CAR-T cells may overcome this issue and induce remission.

Methods

We examined treatment with sequential infusion of humanized CD19-modified and CD22-modified CAR-T cells in a patient with relapsed ALL previously exposed to murine-derived anti-CD19 CAR-T cells.

Results

At ~6 weeks after treatment, repeated bone marrow smear and flow cytometry analysis revealed no lymphoblasts.

Conclusion

Our results suggest that sequential infusion of humanized CD19-modified and CD22-modified CAR-T cells is a valuable option for relapsed patients with prior infusion of murine-derived, CD19-directed CAR-T cells.

CD40 Ligand-Modified Chimeric Antigen Receptor T Cells Enhance Antitumor Function by Eliciting an Endogenous Antitumor Response

Chimeric antigen receptor (CAR) T cells provide great efficacy in B cell malignancies. However, improved CAR T cell therapies are still needed. Here, we engineered tumor-targeted CAR T cells to constitutively express the immune-stimulatory molecule CD40 ligand (CD40L) and explored efficacy in different mouse leukemia/lymphoma models. We observed that CD40L⁺ CAR T cells circumvent tumor immune escape via antigen loss through CD40/CD40L-mediated cytotoxicity and induction of a sustained, endogenous immune response. After adoptive cell transfer, the CD40L⁺ CAR T cells displayed superior antitumor efficacy, licensed antigen-presenting cells, enhanced recruitment of immune effectors, and mobilized endogenous tumor-recognizing T cells. These effects were absent in Cd40^-/- mice and provide a rationale for the use of CD40L⁺ CAR T cells in cancer treatment.

Switchable control over in vivo CAR T expansion, B cell depletion, and induction of memory

Chimeric antigen receptor (CAR) T cell therapy represents a powerful strategy in immuno-oncology. Nevertheless, associated life-threatening toxicities and chronic B cell aplasia have underscored the need to control engineered T cells in the patient. To address these challenges, we have previously developed a switchable CAR (sCAR) T cell platform that allows dose-titratable control over CAR T cell activity by using antibody-based switches. Here, we demonstrate in a syngeneic murine model that the switchable platform can impart antitumor efficacy while dissociating long-term persistence from chronic B cell aplasia. Further, the functional reversibility of the switchable platform can be leveraged to incorporate “rest” phases through cyclical dosing of the switch to enable the induction of a robust central memory population for in vivo, on-demand expansion of sCAR T cells.

Chimeric antigen receptor (CAR) T cells with a long-lived memory phenotype are correlated with durable, complete remissions in patients with leukemia. However, not all CAR T cell products form robust memory populations, and those that do can induce chronic B cell aplasia in patients. To address these challenges, we previously developed a switchable CAR (sCAR) T cell system that allows fully tunable, on/off control over engineered cellular activity. To further evaluate the platform, we generated and assessed different murine sCAR constructs to determine the factors that afford efficacy, persistence, and expansion of sCAR T cells in a competent immune system. We find that sCAR T cells undergo significant in vivo expansion, which is correlated with potent antitumor efficacy. Most importantly, we show that the switch dosing regimen not only allows control over B cell populations through iterative depletion and repopulation, but that the “rest” period between dosing cycles is the key for induction of memory and expansion of sCAR T cells. These findings introduce rest as a paradigm in enhancing memory and improving the efficacy and persistence of engineered T cell products.

Generation of Luciferase-expressing Tumor Cell Lines

Murine tumor models have been critical to advances in our knowledge of tumor physiology and for the development of effective tumor therapies. Essential to these studies is the ability to both track tumor development and quantify tumor burden in vivo. For this purpose, the introduction of genes that confer tumors with bioluminescent properties has been a critical advance for oncologic studies in rodents. Methods of introducing bioluminescent genes, such as firefly luciferase, by viral transduction has allowed for the production of tumor cell lines that can be followed in vivo longitudinally over long periods of time. Here we describe methods for the production of stable luciferase expressing tumor cell lines by lentiviral transduction.

Preclinical Models in Chimeric Antigen Receptor-Engineered T-Cell Therapy

Cancer immunotherapy has enormous potential in inducing long-term remission in cancer patients, and chimeric antigen receptor (CAR)-engineered T cells have been largely successful in treating hematological malignancies in the clinic. CAR-T therapy has not been as effective in treating solid tumors, in part due to the immunosuppressive tumor microenvironment. Additionally, CAR-T therapy can cause dangerous side effects, including off-tumor toxicity, cytokine release syndrome, and neurotoxicity. Animal models of CAR-T therapy often fail to predict such adverse events and frequently overestimate the efficacy of the treatment. Nearly all preclinical CAR-T studies have been performed in mice, including syngeneic, xenograft, transgenic, and humanized mouse models. Recently, a few studies have used primate models to mimic clinical side effects better. To date, no single model perfectly recapitulates the human immune system and tumor microenvironment, and some models have revealed CAR-T limitations that were contradicted or missed entirely in other models. Careful model selection based on the primary goals of the study is a crucial step in evaluating CAR-T treatment. Advancements are being made in preclinical models, with the ultimate objective of providing safer, more effective CAR-T therapy to patients.

Differences in Expansion Potential of Naive Chimeric Antigen Receptor T Cells from Healthy Donors and Untreated Chronic Lymphocytic Leukemia Patients

Introduction

Therapy with chimeric antigen receptor T (CART) cells for hematological malignancies has shown promising results. Effectiveness of CART cells may depend on the ratio of naive (T_N) vs. effector (T_E) T cells, T_N cells being responsible for an enduring antitumor activity through maturation. Therefore, we investigated factors influencing the T_N/T_E ratio of CART cells.

Materials and methods

CART cells were generated upon transduction of peripheral blood mononuclear cells with a CD19.CAR-CD28-CD137zeta third generation retroviral vector under two different stimulating culture conditions: anti-CD3/anti-CD28 antibodies adding either interleukin (IL)-7/IL-15 or IL-2. CART cells were maintained in culture for 20 days. We evaluated 24 healthy donors (HDs) and 11 patients with chronic lymphocytic leukemia (CLL) for the composition of cell subsets and produced CART cells. Phenotype and functionality were tested using flow cytometry and chromium release assays.

Results

IL-7/IL-15 preferentially induced differentiation into T_N, stem cell memory (T_SCM: naive CD27+ CD95+), CD4+ and CXCR3+ CART cells, while IL-2 increased effector memory (T_EM), CD56+ and CD4+ T regulatory (T_Reg) CART cells. The net amplification of different CART subpopulations derived from HDs and untreated CLL patients was compared. Particularly the expansion of CD4+ CART_N cells differed significantly between the two groups. For HDs, this subtype expanded >60-fold, whereas CD4+ CART_N cells of untreated CLL patients expanded less than 10-fold. Expression of exhaustion marker programmed cell death 1 on CART_N cells on day 10 of culture was significantly higher in patient samples compared to HD samples. As the percentage of malignant B cells was expectedly higher within patient samples, an excessive amount of B cells during culture could account for the reduced expansion potential of CART_N cells in untreated CLL patients. Final T_N/T_E ratio stayed <0.3 despite stimulation condition for patients, whereas this ratio was >2 in samples from HDs stimulated with IL-7/IL-15, thus demonstrating efficient CART_N expansion.

Conclusion

Untreated CLL patients might constitute a challenge for long-lasting CART effects in vivo since only a low number of T_N among the CART product could be generated. Depletion of malignant B cells before starting CART production might be considered to increase the T_N/T_E ratio within the CART product.

The impact of antibiotic usage on the efficacy of chemoimmunotherapy is contingent on the source of tumor-reactive T cells

In recent years the combined use of chemotherapy and immunotherapy, collectively termed chemoimmunotherapy, has emerged as a promising treatment option for patients with cancer. Antibiotics are commonly used to reduce infection-related complications in patients undergoing chemotherapy. Intriguingly, accumulating evidence has implicated gut microbiota as a critical determinant of host antitumor immune responses, raising the question as to whether the use of broad-spectrum antibiotics would invariably diminish tumor response to chemoimmunotherapies. We investigated the impact of antibiotics on the therapeutic outcomes of cyclophosphamide (CTX) chemotherapy and adoptive T-cell therapy (ACT) where CTX was used as the host-conditioning regimen in mice. We show that antibiotic prophylaxis dampened the endogenous T cell responses elicited by CTX, and reduced the efficacy of CTX against B-cell lymphoma. In the ACT setting, antibiotics administration impaired the therapeutic effects of adoptively transferred tumor-specific CD4+ T cells in mice with implanted colorectal tumors. In contrast, long-term antibiotic exposure did not affect the efficacy of ACT using CD19-targeting chimeric antigen receptor (CAR) T cells in mice with systemic B-cell lymphoma, although it correlated with prolonged CAR expression and sustained B-cell aplasia. Our study demonstrates that chemoimmunotherapies may have variable reliance on intestinal microbiota for T cell activation and function, and thus have different sensitivities to antibiotic prophylaxis. These findings may have implications for the judicial use of antibiotics in cancer patients receiving chemoimmunotherapies.

GUCY2C-directed CAR-T cells oppose colorectal cancer metastases without autoimmunity

Adoptive T-cell therapy (ACT) is an emerging paradigm in which T cells are genetically modified to target cancer-associated antigens and eradicate tumors. However, challenges treating epithelial cancers with ACT reflect antigen targets that are not tumor-specific, permitting immune damage to normal tissues, and preclinical testing in artificial xenogeneic models, preventing prediction of toxicities in patients. In that context, mucosa-restricted antigens expressed by cancers exploit anatomical compartmentalization which shields mucosae from systemic antitumor immunity. This shielding may be amplified with ACT platforms employing antibody-based chimeric antigen receptors (CARs), which mediate MHC-independent recog-nition of antigens. GUCY2C is a cancer mucosa antigen expressed on the luminal surfaces of the intestinal mucosa in mice and humans, and universally overexpressed by colorectal tumors, suggesting its unique utility as an ACT target. T cells expressing CARs directed by a GUCY2C-specific antibody fragment recognized GUCY2C, quantified by expression of activation markers and cytokines. Further, GUCY2C CAR-T cells lysed GUCY2C-expressing, but not GUCY2C-deficient, mouse colorectal cancer cells. Moreover, GUCY2C CAR-T cells reduced tumor number and morbidity and improved survival in mice harboring GUCY2C-expressing colorectal cancer metastases. GUCY2C-directed T cell efficacy reflected CAR affinity and surface expression and was achieved without immune-mediated damage to normal tissues in syngeneic mice. These observations highlight the potential for therapeutic translation of GUCY2C-directed CAR-T cells to treat metastatic tumors, without collateral autoimmunity, in patients with metastatic colorectal cancer.

CAR T-cell therapy: toxicity and the relevance of preclinical models

Chimeric antigen receptor (CAR) T cells form part of a broad wave of immunotherapies that are showing promise in early phase cancer clinical trials. This clinical delivery has been based upon preclinical efficacy testing that confirmed the proof of principle of the therapy. However, CAR T-cell therapy does not exist alone as T cells are generally given in combination with patient preconditioning, most commonly in the form of chemotherapy, and may also include systemic cytokine support, both of which are associated with toxicity. Consequently, complete CAR T-cell therapy includes elements where the toxicity profile is well known, but also includes the CAR T cell itself, for which toxicity profiles are largely unknown. With recent reports of adverse events associated with CAR T-cell therapy, there is now concern that current preclinical models may not be fit for purpose with respect to CAR T-cell toxicity profiling. Here, we explore the preclinical models used to validate CAR T-cell function and examine their potential to predict CAR T-cell driven toxicities for the future.

Heparan sulfate mimetic PG545-mediated antilymphoma effects require TLR9-dependent NK cell activation

Heparan sulfate (HS) is an essential component of the extracellular matrix (ECM), which serves as a barrier to tumor invasion and metastasis. Heparanase promotes tumor growth by cleaving HS chains of proteoglycan and releasing HS-bound angiogenic growth factors and facilitates tumor invasion and metastasis by degrading the ECM. HS mimetics, such as PG545, have been developed as antitumor agents and are designed to suppress angiogenesis and metastasis by inhibiting heparanase and competing for the HS-binding domain of angiogenic growth factors. However, how PG545 exerts its antitumor effect remains incompletely defined. Here, using murine models of lymphoma, we determined that the antitumor effects of PG545 are critically dependent on NK cell activation and that NK cell activation by PG545 requires TLR9. We demonstrate that PG545 does not activate TLR9 directly but instead enhances TLR9 activation through the elevation of the TLR9 ligand CpG in DCs. Specifically, PG545 treatment resulted in CpG accumulation in the lysosomal compartment of DCs, leading to enhanced production of IL-12, which is essential for PG545-mediated NK cell activation. Overall, these results reveal that PG545 activates NK cells and that this activation is critical for the antitumor effect of PG545. Moreover, our findings may have important implications for improving NK cell-based antitumor therapies.

Lymphoma Immunotherapy: Current Status

The rationale to treat lymphomas with immunotherapy comes from long-standing evidence on their distinctive immune responsiveness. Indolent B-cell non-Hodgkin lymphomas, in particular, establish key interactions with the immune microenvironment to ensure prosurvival signals and prevent antitumor immune activation. However, reports of spontaneous regressions indicate that, under certain circumstances, patients develop therapeutic antitumor immunity. Several immunotherapeutic approaches have been thus developed to boost these effects in all patients. To date, targeting CD20 on malignant B cells with the antibody rituximab has been the most clinically effective strategy. However, relapse and resistance prevent to cure approximately half of B-NHL patients, underscoring the need of more effective therapies. The recognition of B-cell receptor variable regions as B-NHL unique antigens promoted the development of specific vaccines to immunize patients against their own tumor. Despite initial promising results, this strategy has not yet demonstrated a sufficient clinical benefit to reach the regulatory approval. Several novel agents are now available to stimulate immune effector functions or counteract immunosuppressive mechanisms, such as engineered antitumor T cells, co-stimulatory receptor agonist, and immune checkpoint-blocking antibodies. Thus, multiple elements can now be exploited in more effective combinations to break the barriers for the induction of anti-lymphoma immunity.

CD19 chimeric antigen receptor T cell therapy for haematological malignancies

T cells can be redirected to recognize tumour antigens by genetic modification to express a chimeric antigen receptor (CAR). These consist of antibody-derived antigen-binding regions linked to T cell signalling elements. CD19 is an ideal target because it is expressed on most B cell malignancies as well as normal B cells but not on other cell types, restricting any 'on target, off tumour' toxicity to B cell depletion. Recent clinical studies involving CD19 CAR-directed T cells have shown unprecedented responses in a range of B cell malignancies, even in patients with chemorefractory relapse. Durable responses have been achieved, although the persistence of modified T cells may be limited. This therapy is not without toxicity, however. Cytokine release syndrome and neurotoxicity appear to be frequent but are treatable and reversible. CAR T cell therapy holds the promise of a tailored cellular therapy, which can form memory and be adapted to the tumour microenvironment. This review will provide a perspective on the currently available data, as well as on future developments in the field.

Using gene therapy to manipulate the immune system in the fight against B-cell leukemias

INTRODUCTION

Over 20 years ago, chimeric antigen receptors (CARs) were created to endow T cells with new antigen-specificity and create a therapy that could eradicate cancer and provide life-long protection against recurrence. Steady progress has led to significant improvements with CAR design and CAR T-cell production, allowing evaluation of CAR T cells in patients. The initial trials have targeted CD19, which is expressed on normal and malignant B cells.

AREAS COVERED

We review data from trials for patients with chronic lymphocytic leukemia (CLL) and B-cell acute lymphoblastic leukemia (B-ALL). In addition, we discuss the on-target toxicities, B-cell aplasia and cytokine release syndrome (CRS), which is uniquely associated with T-cell immunotherapies.

EXPERT OPINION

We compare the results when targeting the same antigen in CLL or B-ALL and speculate on reasons for outcome differences and future directions to enhance outcomes. Furthermore, the dramatic results targeting B-ALL require further analysis in Phase II trials, and we discuss important components of these future trials. We also suggest a management scheme for CRS. The next several years will be critical and may lead to the first clinical indication of a gene-engineered cell therapy for cancer.

Adoptive T-cell therapy for Leukemia

Allogeneic stem cell transplantation (alloSCT) is the most robust form of adoptive cellular therapy (ACT) and has been tremendously effective in the treatment of leukemia. It is one of the original forms of cancer immunotherapy and illustrates that lymphocytes can specifically recognize and eliminate aberrant, malignant cells. However, because of the high morbidity and mortality that is associated with alloSCT including graft-versus-host disease (GvHD), refining the anti-leukemia immunity of alloSCT to target distinct antigens that mediate the graft-versus-leukemia (GvL) effect could transform our approach to treating leukemia, and possibly other hematologic malignancies. Over the past few decades, many leukemia antigens have been discovered that can separate malignant cells from normal host cells and render them vulnerable targets. In concert, the field of T-cell engineering has matured to enable transfer of ectopic high-affinity antigen receptors into host or donor cells with greater efficiency and potency. Many preclinical studies have demonstrated that engineered and conventional T-cells can mediate lysis and eradication of leukemia via one or more leukemia antigen targets. This evidence now serves as a foundation for clinical trials that aim to cure leukemia using T-cells. The recent clinical success of anti-CD19 chimeric antigen receptor (CAR) cells for treating patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia displays the potential of this new therapeutic modality. In this review, we discuss some of the most promising leukemia antigens and the novel strategies that have been implemented for adoptive cellular immunotherapy of lymphoid and myeloid leukemias. It is important to summarize the data for ACT of leukemia for physicians in-training and in practice and for investigators who work in this and related fields as there are recent discoveries already being translated to the patient setting and numerous accruing clinical trials. We primarily focus on ACT that has been used in the clinical setting or that is currently undergoing preclinical testing with a foreseeable clinical endpoint.

Clinical application of genetically modified T cells in cancer therapy

Immunotherapies are emerging as highly promising approaches for the treatment of cancer. In these approaches, a variety of materials are used to boost immunity against malignant cells. A key component of many of these approaches is functional tumor-specific T cells, but the existence and activity of sufficient T cells in the immune repertoire is not always the case. Recent methods of generating tumor-specific T cells include the genetic modification of patient lymphocytes with receptors to endow them with tumor specificity. These T cells are then expanded in vitro followed by infusion of the patient in adoptive cell transfer protocols. Genes used to modify T cells include those encoding T-cell receptors and chimeric antigen receptors. In this review, we provide an introduction to the field of genetic engineering of T cells followed by details of their use against cancer in the clinic.

Differential role of Th1 and Th2 cytokines in autotoxicity driven by CD19-specific second-generation chimeric antigen receptor T cells in a mouse model

T cells engrafted with chimeric AgRs (CAR) are showing exciting potential for targeting B cell malignancies in early-phase clinical trials. To determine whether the second-generation CAR was essential for optimal antitumor activity, two CD28-based CAR constructs targeting CD19 were tested for their ability to redirect mouse T cell function against established B cell lymphoma in a BALB/c syngeneic model system. T cells armed with either CAR eliminated A20 B cell lymphoma in vivo; however, one construct induced a T cell dose-dependent acute toxicity associated with a raised serum Th1 type cytokine profile on transfer into preconditioned mice. Moreover, a chronic toxicity manifested as granuloma-like formation in spleen, liver, and lymph nodes was observed in animals receiving T cells bearing either CD28 CAR, albeit with different kinetics dependent upon the specific receptor used. This phenotype was associated with an expansion of CD4+ CAR+ T cells and CD11b+ Gr-1(+) myeloid cells and increased serum Th2-type cytokines, including IL-10 and IL-13. Mouse T cells engrafted with a first-generation CAR failed to develop such autotoxicity, whereas toxicity was not apparent when T cells bearing the same receptors were transferred into C57BL/6 or C3H animals. In summary, the adoptive transfer of second-generation CD19-specific CAR T cells can result in a cell dose-dependent acute toxicity, whereas the prolonged secretion of high levels of Th2 cytokines from these CAR T cells in vivo drives a granulomatous reaction resulting in chronic toxicity. Strategies that prevent a prolonged Th2-cytokine biased CAR T cell response are clearly warranted.

Targeting high-grade B cell lymphoma with CD19-specific T cells

Adoptive T cell therapy is an important additional treatment option for malignant diseases resistant to chemotherapy. Using a murine high-grade B cell lymphoma model, we have addressed the question whether the B cell differentiation antigen CD19 can act as rejection antigen. CD19(-/-) mice inoculated with CD19(+) B cell lymphoma cells showed higher survival rates than WT mice and were protected against additional tumor challenge. T cell depletion prior to tumor transfer completely abolished the protective response. By heterotypic vaccination of CD19(-/-) mice against murine CD19, survival after tumor challenge was significantly increased. To define protective epitopes within the CD19 molecule, T cells collected from mice that had survived the tumor transfer were analyzed for IFNγ secretion in response to CD19-derived peptides. The majority of mice exhibited a CD4(+) T cell response to CD19 peptide 27, which was the most dominant epitope after CD19 vaccination. A peptide 27-specific CD4(+) T cell line protected CD19(-/-) mice against challenge with CD19(+) lymphoma and also cured a significant proportion of WT mice from recurrent disease in a model of minimal residual disease after chemotherapy. In conclusion, our data highlight CD19-specific CD4(+) T cells for adoptive T cell therapy of B cell lymphomas.

Genetic modification of mouse effector and helper T lymphocytes expressing a chimeric antigen receptor

Genetic modification of primary mouse T cells with chimeric antigen receptors (CAR) has emerged as an important tool for optimizing adoptive T cell immunotherapy strategies. However, limitations in current protocols for generating highly pure and sufficient numbers of enriched effector and helper CAR(+) T cell subsets remain problematic. Here, we describe a new retroviral transduction protocol for successfully generating transduced CD8(+) and CD4(+) T lymphocytes for in vitro and in vivo characterization.

Donor-derived CD19-targeted T cells cause regression of malignancy persisting after allogeneic hematopoietic stem cell transplantation

New treatments are needed for B-cell malignancies persisting after allogeneic hematopoietic stem cell transplantation (alloHSCT). We conducted a clinical trial of allogeneic T cells genetically modified to express a chimeric antigen receptor (CAR) targeting the B-cell antigen CD19. T cells for genetic modification were obtained from each patient's alloHSCT donor. All patients had malignancy that persisted after alloHSCT and standard donor lymphocyte infusions (DLIs). Patients did not receive chemotherapy prior to the CAR T-cell infusions and were not lymphocyte depleted at the time of the infusions. The 10 treated patients received a single infusion of allogeneic anti-CD19-CAR T cells. Three patients had regressions of their malignancies. One patient with chronic lymphocytic leukemia (CLL) obtained an ongoing complete remission after treatment with allogeneic anti-CD19-CAR T cells, another CLL patient had tumor lysis syndrome as his leukemia dramatically regressed, and a patient with mantle cell lymphoma obtained an ongoing partial remission. None of the 10 patients developed graft-versus-host disease (GVHD). Toxicities included transient hypotension and fever. We detected cells containing the anti-CD19-CAR gene in the blood of 8 of 10 patients. These results show for the first time that donor-derived allogeneic anti-CD19-CAR T cells can cause regression of B-cell malignancies resistant to standard DLIs without causing GVHD.

Chimeric antigen receptors for the adoptive T cell therapy of hematologic malignancies

The genetic modification of autologous T cells with chimeric antigen receptors (CARs) represents a breakthrough for gene engineering as a cancer therapy for hematologic malignancies. By targeting the CD19 antigen, we have demonstrated robust and rapid anti-leukemia activity in patients with heavily pre-treated and chemotherapy-refractory B cell acute lymphoblastic leukemia (B-ALL). We demonstrated rapid induction of deep molecular remissions in adults, which has been recently confirmed in a case report involving a child with B-ALL. In contrast to the results when treating B-ALL, outcomes have been more modest in patients with chronic lymphocytic leukemia (CLL) or other non-hodgkin's lymphoma (NHL). We review the clinical trial experience targeting B-ALL and CLL and speculate on the possible reasons for the different outcomes and propose potential optimization to CAR T cell therapy when targeting CLL or other indolent NHL. Lastly, we discuss the pre-clinical development and potential for clinical translation for using CAR T cells against multiple myeloma and acute myeloid leukemia. We highlight the potential risks and benefits by targeting these poor outcome hematologic malignancies.

Chimeric antigen receptor therapy for chronic lymphocytic leukemia: what are the challenges?

Chimeric antigen receptor (CAR)-modified T cells targeting CD19 expressed by normal and malignant B cells is a unique therapy for patients with chronic lymphocytic leukemia (CLL); recent results highlight the potential of this therapy for patients with relapsed CLL. Because adoptive transfer of CAR-modified T cells is a novel approach, there are issues for the medical oncologist to consider when evaluating current and future clinical trials for CLL patients. This article reviews the impact of CAR design, T-cell production, T-cell dose, conditioning regimens, and tumor burden at the time of CAR-modified T-cell infusion on the efficacy of this therapy.

Gene-engineered T cells for cancer therapy

T cells have the capacity to eradicate diseased cells, but tumours present considerable challenges that render T cells ineffectual. Cancer cells often make themselves almost 'invisible' to the immune system, and they sculpt a microenvironment that suppresses T cell activity, survival and migration. Genetic engineering of T cells can be used therapeutically to overcome these challenges. T cells can be taken from the blood of cancer patients and then modified with genes encoding receptors that recognize cancer-specific antigens. Additional genes can be used to enable resistance to immunosuppression, to extend survival and to facilitate the penetration of engineered T cells into tumours. Using genetic modification, highly active, self-propagating 'slayers' of cancer cells can be generated.

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.

An Influenza Virus M2 Protein Specific Chimeric Antigen Receptor Modulates Influenza A/WSN/33 H1N1 Infection In Vivo

A potential target for the development of universal vaccine strategies against Influenza A is the M2 protein – a membrane protein with a highly conserved extracellular domain. In this study we developed engineered T-cell receptors, by fusing M2-specific antibody sequences with T-cell receptor transmembrane and signaling domains to target influenza infected cells. When expressed on T-cells, these novel T-cell receptors (chimeric antigen receptors - CARs) are able to recognize specific antigens on the surface of target cells via an MHC-independent mechanism. Using an existing monoclonal antibody (14C2) specific for the M2 ectodomain (M2e), we generated an M2-specific CAR. We tested the specificity of this M2 CAR in vitro by measuring the activation of T-cells in response to M2-specific peptides or M2-expressing cell lines. Both Jurkat T-cells and peripheral blood mononuclear cells expressing the M2-specific CAR responded to specific antigen stimulation by upregulating NFAT and producing γ-interferon. To test whether the M2-specific CAR are effective at recognizing influenza infected cells in vivo we used an established BALB/c murine infection model. At day 4 post-infection, when M2 CAR expressing splenocytes could be detected in the lung, the Influenza A/WSN/33 virus titre was around 50% of that in control mice. Although the lung virus titre later increased in the treated group, virus was cleared in both groups of mice by day 8. The results provide support for the development of M2e as a target for cell mediated immunotherapy.

B-cell maturation antigen is a promising target for adoptive T-cell therapy of multiple myeloma

PURPOSE

Multiple myeloma is a usually incurable malignancy of plasma cells. New therapies are urgently needed for multiple myeloma. Adoptive transfer of chimeric antigen receptor (CAR)-expressing T cells is a promising new therapy for hematologic malignancies, but an ideal target antigen for CAR-expressing T-cell therapies for multiple myeloma has not been identified. B-cell maturation antigen (BCMA) is a protein that has been reported to be selectively expressed by B-lineage cells including multiple myeloma cells. Our goal was to determine if BCMA is a suitable target for CAR-expressing T cells.

EXPERIMENTAL DESIGN

We conducted an assessment of BCMA expression in normal human tissues and multiple myeloma cells by flow cytometry, quantitative PCR, and immunohistochemistry. We designed and tested novel anti-BCMA CARs.

RESULTS

BCMA had a restricted RNA expression pattern. Except for expression in plasma cells, BCMA protein was not detected in normal human tissues. BCMA was not detected on primary human CD34(+) hematopoietic cells. We detected uniform BCMA cell-surface expression on primary multiple myeloma cells from five of five patients. We designed the first anti-BCMA CARs to be reported and we transduced T cells with lentiviral vectors encoding these CARs. The CARs gave T cells the ability to specifically recognize BCMA. The anti-BCMA-CAR-transduced T cells exhibited BCMA-specific functions including cytokine production, proliferation, cytotoxicity, and in vivo tumor eradication. Importantly, anti-BCMA-CAR-transduced T cells recognized and killed primary multiple myeloma cells.

CONCLUSIONS

BCMA is a suitable target for CAR-expressing T cells, and adoptive transfer of anti-BCMA-CAR-expressing T cells is a promising new strategy for treating multiple myeloma.

Immunotherapies in CLL

Chronic lymphocytic leukemia (CLL) is the most frequently diagnosed leukemia in the Western world, yet remains essentially incurable. Although initial chemotherapy response rates are high, patients invariably relapse and subsequently develop resistance to chemotherapy. For the moment, allogeneic hematopoietic stem cell transplant (allo-HSCT) remains the only potentially curative treatment for patients with CLL, but it is associated with high rates of treatment-related mortality. Immune-based treatment strategies to augment the cytotoxic potential of T cells offer exciting new treatment options for patients with CLL, and provide a unique and powerful spectrum of tools distinct from traditional chemotherapy. Among the most novel and promising of these approaches are chimeric antigen receptor (CAR)-based cell therapies that combine advances in genetic engineering and adoptive immunotherapy.

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.