TCRαβ/CD3 disruption enables CD3-specific antileukemic T cell immunotherapy

Advances in CAR-T-cell therapy in T-cell malignancies

Significant advances have been made in chimeric antigen receptor T (CAR-T)-cell therapy for the treatment of recurrent or refractory B-cell hematologic malignancies. However, CAR-T-cell therapy has not yet achieved comparable success in the management of aggressive T-cell malignancies. This article reviews the challenges of CAR-T-cell therapy in treating T-cell malignancies and summarizes the progress of preclinical and clinical studies in this area. We present an analysis of clinical trials of CAR-T-cell therapies for the treatment of T-cell malignancies grouped by target antigen classification. Moreover, this review focuses on the major challenges encountered by CAR-T-cell therapies, including the nonspecific killing due to T-cell target antigen sharing and contamination with cell products during preparation. This review discusses strategies to overcome these challenges, presenting novel therapeutic approaches that could enhance the efficacy and applicability of CAR-T-cell therapy in the treatment of T-cell malignancies. These ideas and strategies provide important information for future studies to promote the further development and application of CAR-T-cell therapy in this field.

Notch3-regulated microRNAs impair CXCR4-dependent maturation of thymocytes allowing maintenance and progression of T-ALL

Malignant transformation of T-cell progenitors causes T-cell acute lymphoblastic leukemia (T-ALL), an aggressive childhood lymphoproliferative disorder. Activating mutations of Notch, Notch1 and Notch3, have been detected in T-ALL patients. In this study, we aimed to deeply characterize hyperactive Notch3-related pathways involved in T-cell dynamics within the thymus and bone marrow to propose these processes as an important step in facilitating the progression of T-ALL. We previously generated a transgenic T-ALL mouse model (N3-ICtg) demonstrating that aberrant Notch3 signaling affects early thymocyte maturation programs and leads to bone marrow infiltration by CD4+CD8+ (DP) T cells that are notably, Notch3highCXCR4high. Newly, our in vivo results suggest that an anomalous immature thymocyte subpopulation, such as CD4-CD8- (DN) over-expressing CD3ɛ, but with low CXCR4 expression, dominates N3-ICtg thymus-resident DN subset in T-ALL progression. MicroRNAs might be of significance in T-ALL pathobiology, however, whether required for leukemia maintenance is not fully understood. The selection of specific DN subsets demonstrates the inverse correlation between CXCR4 expression and a panel of Notch3-deregulated miRNAs. Interestingly, we found that within DN thymocyte subset hyperactive Notch3 inhibits CXCR4 expression through the cooperative effects of miR-139-5p and miR-150-5p, thus impinging on thymocyte differentiation with accumulation of DNCD3ɛ+CXCR4- cells. These data point out that deregulation of Notch3 in T-ALL, besides its role in sustaining dissemination of abnormal DP T cells, as we previously demonstrated, could play a role in selecting specific DN immature T cells within the thymus, thus impeding T cell development, to facilitate T-ALL progression inside the bone marrow.

CAR T Cells in T Cell Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma

Chimeric antigen receptor (CAR T) therapy produced excellent activity in patients with relapsed/refractory B-lineage malignancies. However, extending these therapies to T cell cancers requires overcoming unique challenges. In the recent years, multiple approaches have been developed in preclinical models and some were tested in clinical trials in patients with treatment-refractory T-cell malignanices with promising early results. Here, we review main hurdles impeding the success of CAR T therapy in T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL), discuss potential solutions, and summarize recent progress in both preclinical and clinical development of CAR T therapy for these diseases.

Novel and multiple targets for chimeric antigen receptor-based therapies in lymphoma

Chimeric antigen receptor (CAR) T-cell therapy targeting CD19 in B-cell non-Hodgkin lymphoma (NHL) validates the utility of CAR-based therapy for lymphomatous malignancies. Despite the success, treatment failure due to CD19 antigen loss, mutation, or down-regulation remains the main obstacle to cure. On-target, off-tumor effect of CD19-CAR T leads to side effects such as prolonged B-cell aplasia, limiting the application of therapy in indolent diseases such as chronic lymphocytic leukemia (CLL). Alternative CAR targets and multi-specific CAR are potential solutions to improving cellular therapy outcomes in B-NHL. For Hodgkin lymphoma and T-cell lymphoma, several cell surface antigens have been studied as CAR targets, some of which already showed promising results in clinical trials. Some antigens are expressed by different lymphomas and could be used for designing tumor-agnostic CAR. Here, we reviewed the antigens that have been studied for novel CAR-based therapies, as well as CARs designed to target two or more antigens in the treatment of lymphoma.

Strategies and rules for tuning TCR-derived therapy

Manipulation of T cells has revolutionized cancer immunotherapy. Notably, the use of T cells carrying engineered T cell receptors (TCR-T) offers a favourable therapeutic pathway, particularly in the treatment of solid tumours. However, major challenges such as limited clinical response efficacy, off-target effects and tumour immunosuppressive microenvironment have hindered the clinical translation of this approach. In this review, we mainly want to guide TCR-T investigators on several major issues they face in the treatment of solid tumours after obtaining specific TCR sequences: (1) whether we have to undergo affinity maturation or not, and what parameter we should use as a criterion for being more effective. (2) What modifications can be added to counteract the tumour inhibitory microenvironment to make our specific T cells to be more effective and what is the safety profile of such modifications? (3) What are the new forms and possibilities for TCR-T cell therapy in the future?

Chimeric antigen receptor T cells march into T cell malignancies

T cell malignancies represent a diverse collection of leukemia/lymphoma conditions in humans arising from aberrant T cells. Such malignancies are often associated with poor clinical prognoses, cancer relapse, as well as progressive resistance to anti-cancer treatments. While chimeric antigen receptor (CAR) T cell immunotherapy has emerged as a revolutionary treatment strategy that is highly effective for treating B cell malignancies, its application as a treatment for T cell malignancies remains to be better explored. Furthermore, the effectiveness of CAR-T treatment in T cell malignancies is significantly influenced by the quality of contamination-free CAR-T cells during the manufacturing process, as well as by multiple characteristics of such malignancies, including the sharing of antigens across normal and malignant T cells, fratricide, and T cell aplasia. In this review, we provide a detailed account of the current developments in the clinical application of CAR-T therapy to treat T cell malignancies, offer strategies for addressing current challenges, and outline a roadmap toward its effective implementation as a broad treatment option for this condition.

Targeting T-cell malignancies using allogeneic double-negative CD4-CAR-T cells

BACKGROUND

Patients with relapsed/refractory T-cell malignancies have limited treatment options. The use of chimeric antigen receptor (CAR)-T cell therapy for T-cell malignancies is challenging due to possible blast contamination of autologous T-cell products and fratricide of CAR-T cells targeting T-lineage antigens. Recently, allogeneic double-negative T cells (DNTs) have been shown to be safe as an off-the-shelf adoptive cell therapy and to be amendable for CAR transduction. Here, we explore the antitumor activity of allogeneic DNTs against T-cell malignancies and the potential of using anti-CD4-CAR (CAR4)-DNTs as adoptive cell therapy for T-cell malignancies.

METHODS

Healthy donor-derived allogeneic DNTs were ex vivo expanded with or without CAR4 transduction. The antitumor activity of DNTs and CAR4-DNTs against T-cell acute lymphoblastic leukemia (T-ALL) and peripheral T-cell lymphoma (PTCL) were examined using flow cytometry-based cytotoxicity assays and xenograft models. Mechanisms of action were investigated using transwell assays and blocking assays.

RESULTS

Allogeneic DNTs induced endogenous antitumor cytotoxicity against T-ALL and PTCL in vitro, but high doses of DNTs were required to attain therapeutic effects in vivo. The potency of DNTs against T-cell malignancies was significantly enhanced by transducing DNTs with a third-generation CAR4. CAR4-DNTs were manufactured without fratricide and showed superior cytotoxicity against CD4+ T-ALL and PTCL in vitro and in vivo relative to empty-vector transduced-DNTs. CAR4-DNTs eliminated T-ALL and PTCL cell lines and primary T-ALL blasts in vitro. CAR4-DNTs effectively infiltrated tumors, delayed tumor progression, and prolonged the survival of T-ALL and PTCL xenografts. Further, pretreatment of CAR4-DNTs with PI3Kδ inhibitor idelalisib promoted memory phenotype of CAR4-DNTs and enhanced their persistence and antileukemic efficacy in vivo. Mechanistically, LFA-1, NKG2D, and perforin/granzyme B degranulation pathways were involved in the DNT-mediated and CAR4-DNT-mediated killing of T-ALL and PTCL.

CONCLUSIONS

These results demonstrate that CAR4-DNTs can effectively target T-ALL and PTCL and support allogeneic CAR4-DNTs as adoptive cell therapy for T-cell malignancies.

Autologous, allogeneic hematopoietic cell transplantation and CAR-T/NK therapy: what is their real importance in PTCL?

Peripheral T cell lymphoma (PTCL) is a rare and aggressive type of non-Hodgkin's lymphoma that affects mature T cells. This type of cancer is characterized by the abnormal growth of T cells, which can accumulate in the lymph nodes, spleen, bone marrow, and other organs, leading to a variety of symptoms. PTCLs are often difficult to diagnose and treat, and they have a poorer prognosis than other types of lymphoma. However, recent advancements in treatment options, such as targeted therapies have shown promise in improving outcomes for patients with PTCL. Here, we discuss the use of autologous and allogeneic hematopoietic cell transplantation (HCT) as a treatment strategy for patients with PTCL, as well as the recent treatment approaches based on advanced cellular therapy. The current evidence for the use of HCT in PTCL is mainly derived from registry data, retrospective studies, and expert opinion, as randomized trials are limited due to the low incidence and histological heterogeneity of PTCL subtypes.

Inserting EF1α-driven CD7-specific CAR at CD7 locus reduces fratricide and enhances tumor rejection

CAR-T therapies to treat T-cell malignancies face unique hurdles. Normal and malignant T cells usually express the same target for CAR, leading to fratricide. CAR-T cells targeting CD7, which is expressed in various malignant T cells, have limited expansion due to fratricide. Using CRISPR/Cas9 to knockout CD7 can reduce the fratricide. Here we developed a 2-in-1 strategy to insert EF1α-driven CD7-specific CAR at the disrupted CD7 locus and compared it to two other known strategies: one was random integration of CAR by a retrovirus and the other was site-specific integration at T-cell receptor alpha constant (TRAC) locus, both in the context of CD7 disruption. All three types of CD7 CAR-T cells with reduced fratricide could expand well and displayed potent cytotoxicity to both CD7+ tumor cell lines and patient-derived primary tumors. Moreover, EF1α-driven CAR expressed at the CD7 locus enhances tumor rejection in a mouse xenograft model of T-cell acute lymphoblastic leukemia (T-ALL), suggesting great clinical application potential. Additionally, this 2-in-1 strategy was adopted to generate CD7-specific CAR-NK cells as NK also expresses CD7, which would prevent contamination from malignant cells. Thus, our synchronized antigen-knockout CAR-knockin strategy could reduce the fratricide and enhance anti-tumor activity, advancing clinical CAR-T treatment of T-cell malignancies.

Combining different CRISPR nucleases for simultaneous knock-in and base editing prevents translocations in multiplex-edited CAR T cells

BACKGROUND

Multiple genetic modifications may be required to develop potent off-the-shelf chimeric antigen receptor (CAR) T cell therapies. Conventional CRISPR-Cas nucleases install sequence-specific DNA double-strand breaks (DSBs), enabling gene knock-out or targeted transgene knock-in. However, simultaneous DSBs provoke a high rate of genomic rearrangements which may impede the safety of the edited cells.

RESULTS

Here, we combine a non-viral CRISPR-Cas9 nuclease-assisted knock-in and Cas9-derived base editing technology for DSB free knock-outs within a single intervention. We demonstrate efficient insertion of a CAR into the T cell receptor alpha constant (TRAC) gene, along with two knock-outs that silence major histocompatibility complexes (MHC) class I and II expression. This approach reduces translocations to 1.4% of edited cells. Small insertions and deletions at the base editing target sites indicate guide RNA exchange between the editors. This is overcome by using CRISPR enzymes of distinct evolutionary origins. Combining Cas12a Ultra for CAR knock-in and a Cas9-derived base editor enables the efficient generation of triple-edited CAR T cells with a translocation frequency comparable to unedited T cells. Resulting TCR- and MHC-negative CAR T cells resist allogeneic T cell targeting in vitro.

CONCLUSIONS

We outline a solution for non-viral CAR gene transfer and efficient gene silencing using different CRISPR enzymes for knock-in and base editing to prevent translocations. This single-step procedure may enable safer multiplex-edited cell products and demonstrates a path towards off-the-shelf CAR therapeutics.

Are we there yet? cellular therapies for cutaneous T cell lymphoma

Cutaneous T cell lymphomas (CTCLs) are a heterogenous group of skin-involved T-cell non-Hodgkin lymphoma which Mycosis Fungoides and Sezary Syndrome are the most common variants. Despite considerable progress in distinguishing the pathophysiology, the treatment options are still limited for advanced-stage disease. Recent approval of novel agents such as vorinostat, brentuximab vedotin and mogamulizumab paved a way. Allogeneic hematopoietic stem cell transplantation has been shown to be a feasible option in selected advanced-stage CTCL patients. Chimeric antigen receptor (CAR) T cells have been promising for the treatment of B-cell tumors and have been approved for second-line treatment in non-Hodgkin's lymphoma. Although several obstacles still need to be addressed, CAR T cell treatment for CTCLs seems not far off. This review discusses new discoveries in pathophysiology, the state of cellular therapies in current practice, challenges for cellular treatment in advanced CTCL, and how to overcome these challenges.

Genome-edited allogeneic donor "universal" chimeric antigen receptor T cells

αβ T cell receptor (TCRαβ) T cells modified to express chimeric antigen receptors (CAR), are now available as authorized therapies for certain B-cell malignancies. However the process of autologous harvest and generation of patient-specific products is costly, with complex logistics and infrastructure requirements. Premanufactured banks of allogeneic donor-derived CAR T cells could help widen applicability if the challenges of HLA-mismatched T-cell therapy can be addressed. Genome editing is being applied to overcome allogeneic barriers, most notably, by disrupting TCRαβ to prevent graft-versus-host disease, and multiple competing editing technologies, including CRISPR/Cas9 and base editing, have reached clinical phase testing. Improvements in accuracy and efficiency have unlocked applications for a wider range of blood malignancies, with multiplexed editing incorporated to target HLA molecules, shared antigens and checkpoint pathways. Clinical trials will help establish safety profiles and determine the durability of responses as well as the role of consolidation with allogeneic transplantation.

CAR T-Cell Immunotherapy Treating T-ALL: Challenges and Opportunities

T-cell acute lymphoblastic leukemia (T-ALL), a form of T-cell malignancy, is a typically aggressive hematological malignancy with high rates of disease relapse and a poor prognosis. Current guidelines do not recommend any specific treatments for these patients, and only allogeneic stem cell transplant, which is associated with potential risks and toxicities, is a curative therapy. Recent clinical trials showed that immunotherapies, including monoclonal antibodies, checkpoint inhibitors, and CAR T therapies, are successful in treating hematologic malignancies. CAR T cells, which specifically target the B-cell surface antigen CD19, have demonstrated remarkable efficacy in the treatment of B-cell acute leukemia, and some progress has been made in the treatment of other hematologic malignancies. However, the development of CAR T-cell immunotherapy targeting T-cell malignancies appears more challenging due to the potential risks of fratricide, T-cell aplasia, immunosuppression, and product contamination. In this review, we discuss the current status of and challenges related to CAR T-cell immunotherapy for T-ALL and review potential strategies to overcome these limitations.

The emerging scenario of immunotherapy for T-cell Acute Lymphoblastic Leukemia: advances, challenges and future perspectives

T-cell acute lymphoblastic leukemia (T-ALL) is a challenging pediatric and adult haematologic disease still associated with an unsatisfactory cure rate. Unlike B-ALL, the availability of novel therapeutic options to definitively improve the life expectancy for relapsed/resistant patients is poor. Indeed, the shared expression of surface targets among normal and neoplastic T-cells still limits the efficacy and may induce fratricide effects, hampering the use of innovative immunotherapeutic strategies. However, novel monoclonal antibodies, bispecific T-cell engagers (BTCEs), and chimeric antigen receptors (CAR) T-cells recently showed encouraging results and some of them are in an advanced stage of pre-clinical development or are currently under investigation in clinical trials. Here, we review this exciting scenario focusing on most relevant advances, challenges, and perspectives of the emerging landscape of immunotherapy of T-cell malignancies.

Feasibility and preclinical efficacy of CD7-unedited CD7 CAR T cells for T cell malignancies

Chimeric antigen receptor (CAR)-mediated targeting of T lineage antigens for the therapy of blood malignancies is frequently complicated by self-targeting of CAR T cells or their excessive differentiation driven by constant CAR signaling. Expression of CARs targeting CD7, a pan-T cell antigen highly expressed in T cell malignancies and some myeloid leukemias, produces robust fratricide and often requires additional mitigation strategies, such as CD7 gene editing. In this study, we show fratricide of CD7 CAR T cells can be fully prevented using ibrutinib and dasatinib, the pharmacologic inhibitors of key CAR/CD3ζ signaling kinases. Supplementation with ibrutinib and dasatinib rescued the ex vivo expansion of unedited CD7 CAR T cells and allowed regaining full CAR-mediated cytotoxicity in vitro and in vivo on withdrawal of the inhibitors. The unedited CD7 CAR T cells persisted long term and mediated sustained anti-leukemic activity in two mouse xenograft models of human T cell acute lymphoblastic leukemia (T-ALL) by self-selecting for CD7-, fratricide-resistant CD7 CAR T cells that were transcriptionally similar to control CD7-edited CD7 CAR T cells. Finally, we showed feasibility of cGMP manufacturing of unedited autologous CD7 CAR T cells for patients with CD7+ malignancies and initiated a phase I clinical trial (ClinicalTrials.gov: NCT03690011) using this approach. These results indicate pharmacologic inhibition of CAR signaling enables generating functional CD7 CAR T cells without additional engineering.

T-cell acute lymphoblastic leukemia: promising experimental drugs in clinical development

INTRODUCTION

Despite advances in treatment approaches in acute lymphoblastic leukemia (ALL), the prognosis of adults with newly diagnosed T-ALL remains poor, as well as that of adults and children with relapsed disease. Novel targeted therapies are therefore needed.

AREAS COVERED

This review summarizes promising emerging strategies for the treatment of T-ALL.

EXPERT OPINION

The recent molecular characterization of T-ALL has led to the identification of new therapeutic targets. Small-molecules inhibitors and other targeted therapies have therefore been recently developed and are currently under clinical investigations. Similarly, first studies involving monoclonal antibodies and chimeric antigen receptor (CAR) T cells have shown encouraging results. Improvement of outcome with these novel approaches, eventually combined with current standard chemotherapy, is therefore expected in a near future in T-ALL.

Efficient preclinical treatment of cortical T cell acute lymphoblastic leukemia with T lymphocytes secreting anti-CD1a T cell engagers

BACKGROUND

The dismal clinical outcome of relapsed/refractory (R/R) T cell acute lymphoblastic leukemia (T-ALL) highlights the need for innovative targeted therapies. Although chimeric antigen receptor (CAR)-engineered T cells have revolutionized the treatment of B cell malignancies, their clinical implementation in T-ALL is in its infancy. CD1a represents a safe target for cortical T-ALL (coT-ALL) patients, and fratricide-resistant CD1a-directed CAR T cells have been preclinically validated as an immunotherapeutic strategy for R/R coT-ALL. Nonetheless, T-ALL relapses are commonly very aggressive and hyperleukocytic, posing a challenge to recover sufficient non-leukemic effector T cells from leukapheresis in R/R T-ALL patients.

METHODS

We carried out a comprehensive study using robust in vitro and in vivo assays comparing the efficacy of engineered T cells either expressing a second-generation CD1a-CAR or secreting CD1a x CD3 T cell-engaging Antibodies (CD1a-STAb).

RESULTS

We show that CD1a-T cell engagers bind to cell surface expressed CD1a and CD3 and induce specific T cell activation. Recruitment of bystander T cells endows CD1a-STAbs with an enhanced in vitro cytotoxicity than CD1a-CAR T cells at lower effector:target ratios. CD1a-STAb T cells are as effective as CD1a-CAR T cells in cutting-edge in vivo T-ALL patient-derived xenograft models.

CONCLUSIONS

Our data suggest that CD1a-STAb T cells could be an alternative to CD1a-CAR T cells in coT-ALL patients with aggressive and hyperleukocytic relapses with limited numbers of non-leukemic effector T cells.

Harnessing the Potential of Chimeric Antigen Receptor T-Cell Therapy for the Treatment of T-Cell Malignancies: A Dare or Double Dare?

Historical standard of care treatments of T-cell malignancies generally entailed the use of cytotoxic and depleting approaches. These strategies are, however, poorly validated and record dismal long-term outcomes. More recently, the introduction and approval of chimeric antigen receptor (CAR)-T cell therapy has revolutionized the therapy of B-cell malignancies. Translating this success to the T-cell compartment has so far proven hazardous, entangled by risks of fratricide, T-cell aplasia, and product contamination by malignant cells. Several strategies have been utilized to overcome these challenges. These include the targeting of a selective cognate antigen exclusive to T-cells or a subset of T-cells, disruption of target antigen expression on CAR-T constructs, use of safety switches, non-viral transduction, and the introduction of allogeneic compounds and gene editing technologies. We herein overview these historical challenges and revisit the opportunities provided as potential solutions. An in-depth understanding of the tumor microenvironment is required to optimally harness the potential of the immune system to treat T-cell malignancies.

Chimeric antigen receptor T-cell therapy for T-ALL and AML

Non-B-cell acute leukemia is a term that encompasses T-cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML). Currently, the therapeutic effectiveness of existing treatments for refractory or relapsed (R/R) non-B-cell acute leukemia is limited. In such situations, chimeric antigen receptor (CAR)-T cell therapy may be a promising approach to treat non-B-cell acute leukemia, given its promising results in B-cell acute lymphoblastic leukemia (B-ALL). Nevertheless, fratricide, malignant contamination, T cell aplasia for T-ALL, and specific antigen selection and complex microenvironment for AML remain significant challenges in the implementation of CAR-T therapy for T-ALL and AML patients in the clinic. Therefore, designs of CAR-T cells targeting CD5 and CD7 for T-ALL and CD123, CD33, and CLL1 for AML show promising efficacy and safety profiles in clinical trials. In this review, we summarize the characteristics of non-B-cell acute leukemia, the development of CARs, the CAR targets, and their efficacy for treating non-B-cell acute leukemia.

Production and characterization of virus-free, CRISPR-CAR T cells capable of inducing solid tumor regression

BACKGROUND

Chimeric antigen receptor (CAR) T cells have demonstrated high clinical response rates against hematological malignancies (e.g., CD19+ cancers) but have shown limited activity in patients with solid tumors. Recent work showed that precise insertion of a CAR at a defined locus improves treatment outcomes in the context of a CD19 CAR; however, it is unclear if such a strategy could also affect outcomes in solid tumors. Furthermore, CAR manufacturing generally relies on viral vectors for gene delivery, which comprise a complex and resource-intensive part of the manufacturing supply chain.

METHODS

Anti-GD2 CAR T cells were generated using CRISPR/Cas9 within 9 days using recombinant Cas9 protein and nucleic acids, without any viral vectors. The CAR was specifically targeted to the T cell receptor alpha constant gene (TRAC). T cell products were characterized at the level of the genome, transcriptome, proteome, and secretome using CHANGE-seq, targeted next-generation sequencing, scRNA-seq, spectral cytometry, and ELISA assays, respectively. Functionality was evaluated in vivo in an NSG™ xenograft neuroblastoma model.

RESULTS

In comparison to retroviral CAR T cells, virus-free CRISPR CAR (VFC-CAR) T cells exhibit TRAC-targeted genomic integration of the CAR transgene, elevation of transcriptional and protein characteristics associated with a memory-like phenotype, and low tonic signaling prior to infusion arising in part from the knockout of the T cell receptor. On exposure to the GD2 target antigen, anti-GD2 VFC-CAR T cells exhibit specific cytotoxicity against GD2+ cells in vitro and induce solid tumor regression in vivo. VFC-CAR T cells demonstrate robust homing and persistence and decreased exhaustion relative to retroviral CAR T cells against a human neuroblastoma xenograft model.

CONCLUSIONS

This study leverages virus-free genome editing technology to generate CAR T cells featuring a TRAC-targeted CAR, which could inform manufacturing of CAR T cells to treat cancers, including solid tumors.

Generation and proof-of-concept for allogeneic CD123 CAR-Delta One T (DOT) cells in acute myeloid leukemia

Background

Chimeric antigen receptor (CAR)-T cells have emerged as a breakthrough treatment for relapse/refractory hematological tumors, showing impressive complete remission rates. However, around 50% of the patients relapse before 1-year post-treatment. T-cell ‘fitness’ is critical to prolong CAR-T persistence and activity. Allogeneic T cells from healthy donors are less dysfunctional or exhausted than autologous patient-derived T cells; in this context, Delta One T cells (DOTs), a recently described cellular product based on MHC/HLA-independent Vδ1⁺γδ T cells, represent a promising allogeneic platform.

Methods

Here we generated and preclinically validated, for the first time, 4-1BB-based CAR-DOTs directed against the interleukin-3α chain receptor (CD123), a target antigen widely expressed on acute myeloid leukemia (AML) blasts.

Results

CD123CAR-DOTs showed vigorous, superior to control DOTs, cytotoxicity against AML cell lines and primary samples both in vitro and in vivo, even on tumor rechallenge.

Conclusions

Our results provide the proof-of-concept for a DOT-based next-generation allogeneic CAR-T therapy for AML.

Genome-Edited T Cell Therapies

Chimeric antigen receptor (CAR) T-cells are widely being investigated against malignancies, and allogeneic 'universal donor' CAR-T cells offer the possibility of widened access to pre-manufactured, off-the-shelf therapies. Different genome-editing platforms have been used to address human leukocyte antigen (HLA) barriers to generate universal CAR-T cell therapy and early applications have been reported in children and adults against B cell malignancies. Recently developed Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based systems and related technologies offer the prospect of enhanced cellular immunotherapies for a wider range of hematological malignancies.

T cell receptor β-chain-targeting chimeric antigen receptor T cells against T cell malignancies

The success of chimeric antigen receptor (CAR) T cells in treating B cell malignancies comes at the price of eradicating normal B cells. Even though T cell malignancies are aggressive and treatment options are limited, similar strategies for T cell malignancies are constrained by the severe immune suppression arising from bystander T cell aplasia. Here, we show the selective killing of malignant T cells without affecting normal T cell-mediated immune responses in vitro and in a mouse model of disseminated leukemia. Further, we develop a CAR construct that carries the single chain variable fragment of a subtype-specific antibody against the variable TCR β-chain region. We demonstrate that these anti-Vβ8 CAR-T cells are able to recognize and kill all Vβ8⁺ malignant T cells that arise from clonal expansion while sparing malignant or healthy Vβ8⁻ T cells, allowing sufficient T cell-mediated cellular immunity. In summary, we present a proof of concept for a selective CAR-T cell therapy to eradicate T cell malignancies while maintaining functional adaptive immunity, which opens the possibility for clinical development.

Healthy T cells are polyclonal, while malignant T cells are developing via clonal expansion. Here authors show that T cell tumours could be eradicated by chimeric antigen receptor T cells targeting the T cell receptor (TCR) β-chain that is specific to malignant T cells, while healthy T cells using diverse TCR β-chains are spared.

Anti-CCR9 chimeric antigen receptor T cells for T-cell acute lymphoblastic leukemia

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of immature T lymphocytes, associated with higher rates of induction failure compared with those in B cell acute lymphoblastic leukemia. The potent immunotherapeutic approaches applied in B cell acute lymphoblastic leukemia, which have revolutionized the treatment paradigm, have proven more challenging in T-ALL, largely due to a lack of target antigens expressed on malignant but not healthy T cells. Unlike B cell depletion, T-cell aplasia is highly toxic. Here, we show that the chemokine receptor CCR9 is expressed in >70% of cases of T-ALL, including >85% of relapsed/refractory disease, and only on a small fraction (<5%) of normal T cells. Using cell line models and patient-derived xenografts, we found that chimeric antigen receptor (CAR) T-cells targeting CCR9 are resistant to fratricide and have potent antileukemic activity both in vitro and in vivo, even at low target antigen density. We propose that anti-CCR9 CAR-T cells could be a highly effective treatment strategy for T-ALL, avoiding T cell aplasia and the need for genome engineering that complicate other approaches.

Autologous nanobody-derived fratricide-resistant CD7-CAR T cell therapy for patients with relapsed and refractory T-cell acute lymphoblastic leukemia/lymphoma

Purpose: Since CD7 may represent a potent target for T-lymphoblastic leukemia/lymphoma (T-ALL/LBL) immunotherapy, this study aimed to investigate safety and efficacy of autologous CD7-chimeric antigen receptor (CAR) T cells in relapsed and refractory (R/R) T-ALL/LBL patients, as well as its manufacturing feasibility. Experimental Design: Preclinical phase was conducted in NPG{trade mark, serif} mice injected with Luc+ GFP+CCRF-CEM cells. Open label phase I clinical trial (NCT04004637) enrolled patients with R/R CD7-positive T-ALL/LBL who received autologous CD7-CAR T cells infusion. Primary endpoint was safety, secondary endpoints included efficacy, pharmacokinetic and pharmacodynamic parameters. Results: CD7 blockade strategy was developed using tandem CD7 nanobody VHH6 coupled with an ER/Golgi-retention motif peptide to intracellularly fasten CD7 molecules. In preclinical phase CD7 blockade CAR T-cells prevented fratricide and exerted potent cytolytic activity, significantly relieving leukemia progression and prolonged the median survival of mice. In clinical phase, the complete remission (CR) rate was 87.5% (7/8) three months after CAR T cells infusion; one leukemia patient achieved minimal residual disease negative CR and one lymphoma patient achieved CR for more than 12 months. Majority of patients (87.5%) only had grade 1 or 2 cytokine release syndrome with no T-cell hypoplasia or any neurological toxicities observed. The median maximum concentration of CAR T cells was 857.2 cells/µL at approximately 12 days and remained detectable up to 270 days. Conclusions: Autologous nanobody-derived fratricide-resistant CD7-CAR T cells demonstrated a promising and durable antitumor response in R/R T-ALL/LBL with tolerable toxicity, warranting further studies in highly aggressive CD7-positive malignancies.

Hurdles to breakthrough in CAR T cell therapy of solid tumors

Autologous T cells genetically engineered to express chimeric antigen receptor (CAR) have shown promising outcomes and emerged as a new curative option for hematological malignancy, especially malignant neoplasm of B cells. Notably, when T cells are transduced with CAR constructs, composed of the antigen recognition domain of monoclonal antibodies, they retain their cytotoxic properties in a major histocompatibility complex (MHC)-independent manner. Despite its beneficial effect, the current CAR T cell therapy approach faces myriad challenges in solid tumors, including immunosuppressive tumor microenvironment (TME), tumor antigen heterogeneity, stromal impediment, and tumor accessibility, as well as tribulations such as on-target/off-tumor toxicity and cytokine release syndrome (CRS). Herein, we highlight the complications that hamper the effectiveness of CAR T cells in solid tumors and the strategies that have been recommended to overcome these hurdles and improve infused T cell performance.

Increased Activity of a NK-Specific CAR-NK Framework Targeting CD3 and CD5 for T-Cell Leukemias

Simple Summary

Chimeric antigen receptors (CAR) can redirect the activity of NK cells to target T-cell malignancies. Our results identify that recognition of CD5 molecules in malignant T cells by the CAR leads to improved antitumor response compared to targeting CD3, due to strong downregulation of the CD3 antigen after CD3-CAR treatment. We have also identified that a specific CAR-NK framework has superior activity than a CAR-T framework on NK effector cells.

Abstract

NK effector cells expressing a CAR construct may be used to target T-lineage markers. In this work, we compared the activity of a NK-specific CAR-NK and a CAR-T framework when expressed on NK effector cells to target CD3 and CD5 in T-cell malignancies. Our results show that CD3-CAR-T is more active than CD5-CAR-T to eliminate malignant T cells in vitro, however, CD3-CAR-T were less efficient to eliminate tumor cells in vivo, while CD5-CAR-T had antitumor activity in a diffuse xenograft model. Lack of in vivo efficacy correlated with downregulation of CD3 levels in target T cells after coculture with CD3-CAR effector cells. The CAR-NK framework greatly improved the efficacy of CARs leading to increased degranulation, cytokine secretion and elimination of the tumor xenograft by CD5-CAR-NK effector cells. Finally, all CAR constructs were similarly effective to eliminate malignant T cells in vitro. Our results show that the NK-CAR framework improves the activity of CARs in NK cells and that CD5 would be a better target than CD3 for T-cell malignancies, as dynamic downregulation of target expression may affect in vivo efficacy.

Allogeneic gamma delta T cells as adoptive cellular therapy for hematologic malignancies

Cancer immunotherapy, especially T-cell driven targeting, has significantly evolved and improved over the past decade, paving the way to treat previously refractory cancers. Hematologic malignancies, given their direct tumor accessibility and less immunosuppressive microenvironment compared to solid tumors, are better suited to be targeted by cellular immunotherapies. Gamma delta (γδ) T cells, with their unique attributes spanning the entirety of the immune system, make a tantalizing therapeutic platform for cancer immunotherapy. Their inherent anti-tumor properties, ability to act like antigen-presenting cells, and the advantage of having no major histocompatibility complex (MHC) restrictions, allow for greater flexibility in their utility to target tumors, compared to their αβ T cell counterpart. Their MHC-independent anti-tumor activity, coupled with their ability to be easily expanded from peripheral blood, enhance their potential to be used as an allogeneic product. In this review, the potential of utilizing γδ T cells to target hematologic malignancies is described, with a specific focus on their applicability as an allogeneic adoptive cellular therapy product.

Genome Editing as a Vehicle to Drive Successful Chimeric Antigen Receptor T Cell Therapies to the Clinic

Chimeric antigen receptor (CAR) T cells have emerged as an effective therapy for patients with relapsed and refractory haematological malignancies. However, there are many challenges preventing clinical efficacy and thus broader translation of this approach. These hurdles include poor autologous T cell fitness, manufacturing issues and lack of conserved tumour-restricted antigens to target. Recent efforts have been directed toward incorporating genome editing technologies to address these challenges and develop potent CAR T cell therapies for a diverse array of haematopoietic cancers. In this review, the authors discuss gene editing strategies that have been employed to augment CAR T cell fitness, generate allogeneic ‘off-the-shelf’ CAR T cell products, and safely target elusive myeloid and T cell cancers that often lack appropriate tumour-specific antigens.

Genetically Modified T Cells for Esophageal Cancer Therapy: A Promising Clinical Application

Esophageal cancer is an exceedingly aggressive and malignant cancer that imposes a substantial burden on patients and their families. It is usually treated with surgery, chemotherapy, radiotherapy, and molecular-targeted therapy. Immunotherapy is a novel treatment modality for esophageal cancer wherein genetically engineered adoptive cell therapy is utilized, which modifies immune cells to attack cancer cells. Using chimeric antigen receptor (CAR) or T cell receptor (TCR) modified T cells yielded demonstrably encouraging efficacy in patients. CAR-T cell therapy has shown robust clinical results for malignant hematological diseases, particularly in B cell-derived malignancies. Natural killer (NK) cells could serve as another reliable and safe CAR engineering platform, and CAR-NK cell therapy could be a more generalized approach for cancer immunotherapy because NK cells are histocompatibility-independent. TCR-T cells can detect a broad range of targeted antigens within subcellular compartments and hold great potential for use in cancer therapy. Numerous studies have been conducted to evaluate the efficacy and feasibility of CAR and TCR based adoptive cell therapies (ACT). A comprehensive understanding of genetically-modified T cell technologies can facilitate the clinical translation of these adoptive cell-based immunotherapies. Here, we systematically review the state-of-the-art knowledge on genetically-modified T-cell therapy and provide a summary of preclinical and clinical trials of CAR and TCR-transgenic ACT.

Chimeric antigen receptor T cells derived from CD7 nanobody exhibit robust antitumor potential against CD7-positive malignancies

The great success of chimeric antigen receptor T (CAR-T)-cell therapy in B-cell malignancies has significantly promoted its rapid expansion to other targets and indications, including T-cell malignancies and acute myeloid leukemia. However, owing to the life-threatening T-cell hypoplasia caused by CD7-CAR-T cells specific cytotoxic against normal T cells, as well as CAR-T cell-fratricide caused by the shared CD7 antigen on the T-cell surface, the clinical application of CD7 as a potential target for CD7⁺ malignancies is lagging. Here, we generated ^CD7ΔT cells using an anti-CD7 nanobody fragment coupled with an endoplasmic reticulum/Golgi retention domain and demonstrated that these cells transduced with CD7-CAR could prevent fratricide and achieve expansion. Additionally, ^CD7ΔCD7-CAR-T cells exhibited robust antitumor potiential against CD7⁺ tumors in vitro as well as in cell-line and patient-derived xenograft models of CD7-positive malignancies. Furthermore, we confirmed that the antitumor activity of CD7-CAR-T cells was positively correlated with the antigen density of tumor cells. This strategy adapts well with current clinical-grade CAR-T-cell manufacturing processes and can be rapidly applied for the therapy of patients with CD7⁺ malignancies.

Gene editing to enhance the efficacy of cancer cell therapies

Adoptive T cell therapies have shown impressive signals of activity, but their clinical impact could be enhanced by technologies to increase T cell potency and diminish the cost and labor involved in manufacturing these products. Gene editing platforms are under study in this arena to (1) enhance immune cell potency by knocking out molecules that inhibit immune responses; (2) deliver genetic payloads into precise genomic locations and thereby enhance safety and/or improve the gene expression profile by leveraging physiologic promoters, enhancers, and repressors; and (3) enable off-the-shelf therapies by preventing alloreactivity and immune rejection. This review discusses gene editing approaches that have been the best studied in the context of human T cells and adoptive T cell therapies, summarizing their current status and near-term potential for translation.

Promise and pitfalls of allogeneic chimeric antigen receptor therapy in plasma cell and lymphoid malignancies

Chimeric antigen receptor (CAR) T-cell therapy is a promising immunotherapy in haematological malignancies. However, the currently approved products are generated from autologous T cells that require orchestration of several logistically complex steps, which include patient eligibility, apheresis capability, complex manufacturing processes and shipping logistics. Use of third-party donor-derived (allogeneic) effector cells that allows the generation of 'off-the-shelf" CAR T cells (allo-CAR) could circumvent many of the problems associated with autologous CAR T-cell therapy. Several allogeneic products are entering clinical trials, and though early, the results look promising. The recognised potential benefits of allo-CAR do not come without significant challenges, that must be overcome for their widespread use. Alloreactivity, i.e. graft-versus-host disease (GVHD), and rejection of donor T cells is one of the major barriers, while other potential barriers include immunogenicity, unknown in vivo persistence, and CAR T-cell yield. In the present review, we provide a comprehensive review of the challenges associated with autologous CAR, the benefits and potential challenges associated with allo-CAR. Finally, we review the available platforms for allo-CAR for B-cell and plasma cell malignancies.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

From CAR-T Cells to CAR-NK Cells: A Developing Immunotherapy Method for Hematological Malignancies

The approval of CD19 chimeric antigen receptor (CAR)-engineered T (CAR-T) cell products in B-cell malignancies represents a breakthrough in CAR-T cell immunotherapy. However, the remaining limitations concerning the graft-versus-host disease (GVHD) and other adverse effects (e.g., cytokine release syndromes [CRS] and neurotoxicity) still restrict their wider applications. Natural killer (NK) cells have been identified as promising candidates for CAR-based cellular immunotherapy because of their unique characteristics. No HLA-matching restriction and abundant sources make CAR-engineered NK (CAR-NK) cells potentially available to be off-the-shelf products that could be readily available for immediate clinical use. Therefore, researchers have gradually shifted their focus from CAR-T cells to CAR-NK cells in hematological malignancies. This review discusses the current status and applications of CAR-NK cells in hematological malignancies, as well as the unique advantages of CAR-NK cells compared with CAR-T cells. It also discusses challenges and prospects regarding clinical applications of CAR-NK cells.

A deep insight into CRISPR/Cas9 application in CAR-T cell-based tumor immunotherapies

To date, two chimeric antigen receptors (CAR)-T cell products from autologous T cells have been approved by The United States Food and Drug Administration (FDA). The case-by-case autologous T cell generation setting is largely considered as a pivotal restraining cause for its large-scale clinical use because of the costly and prolonged manufacturing procedure. Further, activated CAR-T cells mainly express immune checkpoint molecules, including CTLA4, PD1, LAG3, abrogating CAR-T anti-tumor activity. In addition, CAR-T cell therapy potently results in some toxicity, such as cytokine releases syndrome (CRS). Therefore, the development of the universal allogeneic T cells with higher anti-tumor effects is of paramount importance. Thus, genome-editing technologies, in particular, clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 are currently being used to establish "off-the-shelf" CAR-T cells with robust resistance to immune cell-suppressive molecules. In fact, that simultaneous ablation of PD-1, T cell receptor alpha constant (TRAC or TCR), and also β-2 microglobulin (B2M) by CRISPR-Cas9 technique can support the manufacture of universal CAR-T cells with robust resistance to PD-L1. . Indeed, the ablation of β2M or TARC can severely hinder swift elimination of allogeneic T cells those express foreign HLA-I molecules, and thereby enables the generation of CAR-T cells from allogeneic healthy donors T cells with higher persistence in vivo. Herein, we will deliver a brief overview of the CAR-T cell application in the context of tumor immunotherapy. More importantly, we will discuss recent finding concerning the application of genome editing technologies for preparing universal CAR-T cells or cells that can effectively counter tumor escape, with a special focus on CRISPR-Cas9 technology.

CRISPR/Cas9 technology: towards a new generation of improved CAR-T cells for anticancer therapies

Chimeric antigen receptor (CAR)-modified T cells have raised among other immunotherapies for cancer treatment, being implemented against B-cell malignancies. Despite the promising outcomes of this innovative technology, CAR-T cells are not exempt from limitations that must yet to be overcome in order to provide reliable and more efficient treatments against other types of cancer. The purpose of this review is to shed light on the field of CAR-T cell gene editing for therapy universalization and further enhancement of antitumor function. Several studies have proven that the disruption of certain key genes is essential to boost immunosuppressive resistance, prevention of fratricide, and clinical safety. Due to its unparalleled simplicity, feasibility to edit multiple gene targets simultaneously, and affordability, CRISPR/CRISPR-associated protein 9 system has been proposed in different clinical trials for such CAR-T cell improvement. The combination of such powerful technologies is expected to provide a new generation of CAR-T cell-based immunotherapies for clinical application.

Current Status of CAR T Cell Therapy for Leukemias

OPINION STATEMENT

Chimeric antigen receptor (CAR) T-cell therapy has become the standard of care for children and young adults with relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL), and it is a highly promising therapy under investigation for adults with relapsed disease. Despite having potentially life-threatening toxicities, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, the benefits of CAR T-cell therapy far outweigh these risks, particularly as increased experience and improved supportive care measures are mitigating these toxicities. CAR T cells can result in complete remission for significant proportion of patients with relapsed and refractory B-ALL and permit them to proceed to potentially curative allogeneic hematopoietic stem cell transplantation (allo-HSCT). CAR T cells may also be curative by themselves. Herein lie the greatest challenges and questions for clinical investigators, specifically, how are CAR T cells best employed and how do we overcome mechanisms of resistance to them? The primary clinical question is the timing and even the necessity of allo-HSCT. Relative to resistance, we know that target antigen loss, specifically CD19, is a major contributor to resistance. However, current investigations of alternative targets, such CD22, and CAR T cells expressing dual targeting antigen receptors have demonstrated encouraging initial results and provide a high degree of optimism that the efficacy and the broader application of CAR T-cell therapy will gradually increase in B-ALL. That optimism is not as high and the challenges are increased for the application of CAR T cells in T-cell leukemias and acute myeloid leukemia due to the relative lack of suitable leukemia surface targets that are not also expressed on normal hematopoietic progenitors. Despite these significant challenges, considerable research is being conducted into the development of CAR T cells for these diseases utilizing unique technologies, which may be applicable to other diseases.

State-of-Art of Cellular Therapy for Acute Leukemia

With recent clinical breakthroughs, immunotherapy has become the fourth pillar of cancer treatment. Particularly, immune cell-based therapies have been envisioned as a promising treatment option with curative potential for leukemia patients. Hence, an increasing number of preclinical and clinical studies focus on various approaches of immune cell-based therapy for treatment of acute leukemia (AL). However, the use of different immune cell lineages and subsets against different types of leukemia and patient disease statuses challenge the interpretation of the clinical applicability and outcome of immune cell-based therapies. This review aims to provide an overview on recent approaches using various immune cell-based therapies against acute B-, T-, and myeloid leukemias. Further, the apparent limitations observed and potential approaches to overcome these limitations are discussed.

The Transferrin Receptor-Directed CAR for the Therapy of Hematologic Malignancies

As many patients ultimately relapse after chimeric antigen receptor (CAR) T-cell therapy, identification of alternative targets is currently being evaluated. Substantial research efforts are underway to develop new targets. The transferrin receptor (TfR) is prevalently expressed on rapidly proliferating tumor cells and holds the potential to be the alternative target. In order to investigate the efficacy and challenges of TfR-targeting on the CAR-based therapy strategy, we generated a TfR-specific CAR and established the TfR-CAR–modified T cells. To take the advantage of TfR being widely shared by multiple tumors, TfR-CAR T cells were assessed against several TfR⁺ hematological malignant cell lines. Data showed that TfR-CAR T cells were powerfully potent in killing all these types of cells in vitro and in killing T-ALL cells in vivo. These findings suggest that TfR could be a universal target to broaden and improve the therapeutic efficacy of CAR T cells and warrant further efforts to use these cells as an alternative CAR T cell product for the therapy of hematological malignancies.

Allogeneic CAR T Cells: An Alternative to Overcome Challenges of CAR T Cell Therapy in Glioblastoma

Chimeric antigen receptor (CAR) T cell therapy has emerged as one of the major breakthroughs in cancer immunotherapy in the last decade. Outstanding results in hematological malignancies and encouraging pre-clinical anti-tumor activity against a wide range of solid tumors have made CAR T cells one of the most promising fields for cancer therapies. CAR T cell therapy is currently being investigated in solid tumors including glioblastoma (GBM), a tumor for which survival has only modestly improved over the past decades. CAR T cells targeting EGFRvIII, Her2, or IL-13Rα2 have been tested in GBM, but the first clinical trials have shown modest results, potentially due to GBM heterogeneity and to the presence of an immunosuppressive microenvironment. Until now, the use of autologous T cells to manufacture CAR products has been the norm, but this approach has several disadvantages regarding production time, cost, manufacturing delay and dependence on functional fitness of patient T cells, often reduced by the disease or previous therapies. Universal “off-the-shelf,” or allogeneic, CAR T cells is an alternative that can potentially overcome these issues, and allow for multiple modifications and CAR combinations to target multiple tumor antigens and avoid tumor escape. Advances in genome editing tools, especially via CRISPR/Cas9, might allow overcoming the two main limitations of allogeneic CAR T cells product, i.e., graft-vs.-host disease and host allorejection. Here, we will discuss how allogeneic CAR T cells could allow for multivalent approaches and alteration of the tumor microenvironment, potentially allowing the development of next generation therapies for the treatment of patients with GBM.

Immunogenicity of CAR T cells in cancer therapy

Patient-derived T cells genetically reprogrammed to express CD19-specific chimeric antigen receptors (CARs) have shown remarkable clinical responses and are commercially available for the treatment of patients with certain advanced-stage B cell malignancies. Nonetheless, several trials have revealed pre-existing and/or treatment-induced immune responses to the mouse-derived single-chain variable fragments included in these constructs. These responses might have contributed to both treatment failure and the limited success of redosing strategies observed in some patients. Data from early phase clinical trials suggest that CAR T cells are also associated with immunogenicity-related events in patients with solid tumours. Generally, the clinical implications of anti-CAR immune responses are poorly understood and highly variable between different CAR constructs and malignancies. These observations highlight an urgent need to uncover the mechanisms of immunogenicity in patients receiving CAR T cells and develop validated assays to enable clinical detection. In this Review, we describe the current clinical evidence of anti-CAR immune responses and discuss how new CAR T cell technologies might impact the risk of immunogenicity. We then suggest ways to reduce the risks of anti-CAR immune responses to CAR T cell products that are advancing towards the clinic. Finally, we summarize measures that investigators could consider in order to systematically monitor and better comprehend the possible effects of immunogenicity during trials involving CAR T cells as well as in routine clinical practice.

Base-edited CAR T cells for combinational therapy against T cell malignancies

Targeting T cell malignancies using chimeric antigen receptor (CAR) T cells is hindered by 'T v T' fratricide against shared antigens such as CD3 and CD7. Base editing offers the possibility of seamless disruption of gene expression of problematic antigens through creation of stop codons or elimination of splice sites. We describe the generation of fratricide-resistant T cells by orderly removal of TCR/CD3 and CD7 ahead of lentiviral-mediated expression of CARs specific for CD3 or CD7. Molecular interrogation of base-edited cells confirmed elimination of chromosomal translocations detected in conventional Cas9 treated cells. Interestingly, 3CAR/7CAR co-culture resulted in 'self-enrichment' yielding populations 99.6% TCR-/CD3-/CD7-. 3CAR or 7CAR cells were able to exert specific cytotoxicity against leukaemia lines with defined CD3 and/or CD7 expression as well as primary T-ALL cells. Co-cultured 3CAR/7CAR cells exhibited highest cytotoxicity against CD3 + CD7 + T-ALL targets in vitro and an in vivo human:murine chimeric model. While APOBEC editors can reportedly exhibit guide-independent deamination of both DNA and RNA, we found no problematic 'off-target' activity or promiscuous base conversion affecting CAR antigen-specific binding regions, which may otherwise redirect T cell specificity. Combinational infusion of fratricide-resistant anti-T CAR T cells may enable enhanced molecular remission ahead of allo-HSCT for T cell malignancies.

The immunopathogenesis and immunotherapy of cutaneous T cell lymphoma: Current and future approaches

In the past few decades, immunotherapy has emerged as an effective therapeutic option for patients with cutaneous T cell lymphoma (CTCL). CTCL is characterized by progressive impairment of multiple arms of the immune system. Immunotherapy targets these deficits to stimulate a more robust antitumor response, thereby both clearing the malignant T cells and repairing the immune dysfunction. By potentiating rather than suppressing the immune system, immunotherapy can result in longer treatment responses than alternatives such as chemotherapy. In recent years, advances in our understanding of the pathogenesis of CTCL have led to the development of several new agents with promising efficacy profiles. The second article in this continuing medical education series describes the current immunotherapeutic options for treatment of CTCL, with a focus on how they interact with the immune system and their treatment outcomes in case studies and clinical trials. We will discuss established CTCL immunotherapies, such as interferons, photopheresis, and retinoids; emerging therapies, such as interleukin-12 and Toll-like receptor agonists; and new approaches to targeting tumor antigens and checkpoint molecules, such as mogamulizumab, anti-programmed cell death protein 1, anti-CD47, and chimeric antigen receptor T cell therapy. We also describe the principles of multimodality immunotherapy and the use of total skin electron beam therapy in such regimens.

CAR T cells for other pediatric non-B-cell hematologic malignancies

As CAR T-cell therapy has advanced in B-cell acute lymphoblastic leukemia, research is now underway to develop similar therapies for other lymphoid and myeloid malignancies for pediatric patients. Barriers, including antigen selection and on-target/off-tumor toxicity, have prevented the rapid development of immune-based therapies for T-lineage and myeloid malignancies. More recently, unique strategies have been developed to overcome these barriers, with several products advancing to clinical trials. For T-lineage diseases, targets have focused on CD5, CD7, and CD38, whereas myeloid disease targets have predominately focused on CD123, CD33, and, more recently, CLL-1. This review provides a comprehensive overview of these targets and approaches to overcoming safety concerns in the development of CAR T-cell therapies for pediatric patients with T-lineage and myeloid malignancies.

Improving Cancer Immunotherapy with CRISPR-Based Technology

The rapidly evolving field of immunotherapy has attracted great attention in the field of cancer research and already revolutionized the clinical practice standard for treating cancer. Genetically engineered T cells expressing either T cell receptors or chimeric antigen receptors represent novel treatment modalities and are considered powerful weapons to fight cancer. The immune checkpoint blockade, which harnesses the negative control signaling behind the anti-tumor immune response with therapeutic antibodies by blocking cytotoxic T lymphocyte-associated protein 4 or the programmed cell death 1 pathways are another mainstream direction for cancer immunotherapy. In addition to cytotoxic T cells, other immune cell types such as nature killer cells and macrophages also possess the ability to eradicate cancer cells, which may serve as the basis to develop novel cancer immunotherapies. The advent of cutting-edge genome editing technology, especially clustered regularly interspaced palindromic repeats (CRISPR)-based tools, has greatly expedited many biomedical research areas, including cancer immunology and immunotherapy. In this review, the contribution of current CRISPR techniques to basic and translational cancer immunology research is discussed, and the future for cancer immunotherapy in the age of CRISPR is predicted.