From the mouse cage to human therapy: a personal perspective of the emergence of T-bodies/chimeric antigen receptor T cells

Plasticity and resistance of cancer stem cells as a challenge for innovative anticancer therapies - do we know enough to overcome this?

According to the CSC hypothesis, cancer stem cells are pivotal in initiating, developing, and causing cancer recurrence. Since the identification of CSCs in leukemia, breast cancer, glioblastoma, and colorectal cancer in the 1990s, researchers have actively investigated the origin and biology of CSCs. However, the CSC hypothesis and the role of these cells in tumor development model is still in debate. These cells exhibit distinct surface markers, are capable of self-renewal, demonstrate unrestricted proliferation, and display metabolic adaptation. CSC phenotypic plasticity and the capacity to EMT is strictly connected to the stemness state. CSCs show high resistance to chemotherapy, radiotherapy, and immunotherapy. The plasticity of CSCs is significantly influenced by tumor microenvironment factors, such as hypoxia. Targeting the genetic and epigenetic changes of cancer cells, together with interactions with the tumor microenvironment, presents promising avenues for therapeutic strategies. See also the Graphical abstract(Fig. 1).

CAR T-Cell Therapy for Multiple Myeloma: A Clinical Practice-Oriented Review

The emergence of chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of hematologic malignancies, including multiple myeloma (MM). Two BCMA-directed CAR T-cell products - idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel) - have received US Food and Drug Administration (FDA) approval for patients with relapsed/refractory MM who underwent four or more prior lines of therapy (including an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody). Despite producing unprecedented response rates in an otherwise difficult to treat patient population, CAR T-cell therapies are commonly associated with immune-related adverse events (e.g., cytokine release syndrome and neurotoxicity), cytopenias, and infections. Moreover, many patients continue to exhibit relapse post-treatment, with resistance mechanisms yet to be fully understood. Ongoing basic, translational, and clinical research efforts are poised to generate deeper insights into the optimal utilization of these therapies, improve their efficacy, minimize associated toxicity, and identify new target antigens in patients with MM.

More than Just Skin-Deep: A Review of Imaging's Role in Guiding CAR T-Cell Therapy for Advanced Melanoma

Advanced melanoma is one of the deadliest cancers, owing to its invasiveness and its propensity to develop resistance to therapy. Surgery remains the first-line treatment for early-stage tumors but is often not an option for advanced-stage melanoma. Chemotherapy carries a poor prognosis, and despite advances in targeted therapy, the cancer can develop resistance. CAR T-cell therapy has demonstrated great success against hematological cancers, and clinical trials are deploying it against advanced melanoma. Though melanoma remains a challenging disease to treat, radiology will play an increasing role in monitoring both the CAR T-cells and response to therapy. We review the current imaging techniques for advanced melanoma, as well as novel PET tracers and radiomics, in order to guide CAR T-cell therapy and manage potential adverse events.

Modulating tumor physical microenvironment for fueling CAR-T cell therapy

Chimeric antigen receptor (CAR) T cell therapy has achieved unprecedented clinical success against hematologic malignancies. However, the transition of CAR-T cell therapies for solid tumors is limited by heterogenous antigen expression, immunosuppressive microenvironment (TME), immune adaptation of tumor cells and impeded CAR-T-cell infiltration/transportation. Recent studies increasingly reveal that tumor physical microenvironment could affect various aspects of tumor biology and impose profound impacts on the antitumor efficacy of CAR-T therapy. In this review, we discuss the critical roles of four physical cues in solid tumors for regulating the immune responses of CAR-T cells, which include solid stress, interstitial fluid pressure, stiffness and microarchitecture. We highlight new strategies exploiting these features to enhance the therapeutic potency of CAR-T cells in solid tumors by correlating with the state-of-the-art technologies in this field. A perspective on the future directions for developing new CAR-T therapies for solid tumor treatment is also provided.

Better by design: What to expect from novel CAR-engineered cell therapies?

Chimeric antigen receptor (CAR) technology, and CAR-T cells in particular, have emerged as a new and powerful tool in cancer immunotherapy since demonstrating efficacy against several hematological malignancies. However, despite encouraging clinical results of CAR-T cell therapy products, a significant proportion of patients do not achieve satisfactory responses, or relapse. In addition, CAR-T cell applications to solid tumors is still limited due to the tumor microenvironment and lack of specifically targetable tumor antigens. All current products on the market, as well as most investigational CAR-T cell therapies, are autologous, using the patient's own peripheral blood mononuclear cells as starting material to manufacture a patient-specific batch. Alternative cell sources are, therefore, under investigation (e.g. allogeneic cells from an at least partially human leukocyte antigen (HLA)-matched healthy donor, universal "third-party" cells from a non-HLA-matched donor, cord blood-derived cells, immortalized cell lines or cells differentiated from induced pluripotent stem cells). However, genetic modifications of CAR-engineered cells, bioprocesses used to expand cells, and improved supply chains are still complex and costly. To overcome drawbacks associated with CAR-T technologies, novel CAR designs have been used to genetically engineer cells derived from alpha beta (αβ) T cells, other immune cells such as natural killer (NK) cells, gamma delta (γδ) T cells, macrophages or dendritic cells. This review endeavours to trigger ideas on the next generation of CAR-engineered cell therapies beyond CAR-T cells and, thus, will enable effective, safe and affordable therapies for clinical management of cancer. To achieve this, we present a multidisciplinary overview, addressing a wide range of critical aspects: CAR design, development and manufacturing technologies, pharmacological concepts and clinical applications of CAR-engineered cell therapies. Each of these fields employs a large number of ground-breaking scientific advances, where coordinated and complex process and product development occur at their interfaces.

A Primer on Chimeric Antigen Receptor T-cell Therapy: What Does It Mean for Pathologists?

CONTEXT.—

Chimeric antigen receptor T-cell (CAR-T) technology has shown great promise in both clinical and preclinical models in mediating potent and specific antitumor activity. With the advent of US Food and Drug Administration-approved CAR-T therapies for B-cell lymphoblastic leukemia and B-cell non-Hodgkin lymphomas, CAR-T therapy is poised to become part of mainstream clinical practice.

OBJECTIVE.—

To educate pathologists on CAR-T and chimeric antigen receptor-derived cellular therapy, provide a better understanding of their role in this process, explain important regulatory aspects of CAR-T therapy, and advocate for pathologist involvement in the delivery and monitoring of chimeric antigen receptor-based treatments. Much of the focus of this article addresses US Food and Drug Administration-approved therapies; however, more general issues and future perspectives are considered for therapies in development.

DESIGN.—

A CAR-T workgroup, facilitated by the College of American Pathologists Personalized Health Care Committee and consisting of pathologists of various backgrounds, was convened to develop a summary guidance paper for the College of American Pathologists Council on Scientific Affairs.

RESULTS.—

The workgroup identified gaps in pathologists' knowledge of CAR-T therapy, including uncertainty in the role of the clinical laboratory in supporting CAR-T therapy. The workgroup considered these issues and summarized the findings to assist pathologists to become stakeholders in CAR-T therapy administration.

CONCLUSIONS.—

This manuscript serves to both educate pathologists on CAR-T therapy and serve as a point of initial discussions in areas of CAR-T science, clinical therapy, and regulatory issues as CAR-T therapies continue to be introduced into clinical practice.

The Evolution of Cancer Immunotherapy

Immunotherapy has changed the environment of cancer treatment by providing new and efficacious therapy options for many solid and hematologic malignancies. Although not a new field of oncology, immunotherapy has quickly developed into one of the most flourishing fields in medicine. In this review article, we explore key discoveries which helped to shape our current understanding of the immune system’s role in neoplasms. Many landmark developments include the advancements in checkpoint inhibitors, monoclonal antibodies, CAR-T cells and anti-cancer vaccines. We also explore the drawbacks and efficacy of various categories of immunotherapy. Ongoing investigations within immunotherapy, such as the gut microbiome, combining checkpoint inhibitors and gene sequencing, continue to personalize treatments for cancer patients, providing exciting and endless possibilities for the future.

Global Perspective on the Development of Genetically Modified Immune Cells for Cancer Therapy

Since the first genetically-engineered clinical trial was posted to clinicaltrials.gov in 2003 (NCT00019136), chimeric antigen receptor (CAR) and T-cell receptor (TCR) therapies have exhibited unprecedented growth. USA, China, and Europe have emerged as major sites of investigation as many new biotechnology and established pharmaceutical companies invest in this rapidly evolving field. Although initial studies focused primarily on CD19 as a target antigen, many novel targets are now being evaluated. Next-generation genetic constructs, starting materials, and manufacturing strategies are also being applied to enhance efficacy and safety and to treat solid tumors as well as hematologic malignancies. Fueled by dramatic clinical efficacy and recent regulatory approvals of CD19-targeted CAR cell therapies, the field of engineered cell therapeutics continues to expand. Here, we review all 745 genetically modified CAR and TCR clinical trials with anticipated accrual of over 28,000 patients posted to clinicaltrials.gov until 31st of December 2019. We analyze projected patient enrollment, geographic distribution and phase of studies, target antigens and diseases, current strategies for optimizing efficacy and safety, and trials expected to yield important clinical data in the coming 6-12 months.

Immunobiology of chimeric antigen receptor T cells and novel designs

Advances in the development of immunotherapies have offered exciting new options for the treatment of malignant diseases that are refractory to conventional cytotoxic chemotherapies. The adoptive transfer of T cells expressing chimeric antigen receptors (CARs) has demonstrated dramatic results in clinical trials and highlights the promise of novel immune-based approaches to the treatment of cancer. As experience with CAR T cells has expanded with longer follow-up and to a broader range of diseases, new obstacles have been identified which limit the potential lifelong benefits of CAR T cell therapy. These obstacles highlight not only the gaps in knowledge of the optimal clinical application of this "living drug", but also gaps in our understanding of the fundamental biology of CAR T cells themselves. In this review, we discuss the obstacles facing CAR T cell therapy, how these relate to our current understanding of CAR T cell biology and approaches to enhance the clinical efficacy of this therapy.

Factor VIII: Perspectives on Immunogenicity and Tolerogenic Strategies

Therapeutic treatment of bleeds with FVIII can lead to an antibody response that effectively inhibits its function. Herein, we review the factors that contribute to this immunogenicity and possible ways to overcome it.

Breakthrough Cancer Treatments Raise Difficult Questions

The approval of a first-of-its kind cancer therapy creates new challenges related to safety, access, and costs.

Overcoming Resistance of Human Non-Hodgkin's Lymphoma to CD19-CAR CTL Therapy by Celecoxib and Histone Deacetylase Inhibitors

Patients with B-cell non-Hodgkin’s lymphoma (B-NHL) who fail to respond to first-line treatment regimens or develop resistance, exhibit poor prognosis. This signifies the need to develop alternative treatment strategies. CD19-chimeric antigen receptor (CAR) T cell-redirected immunotherapy is an attractive and novel option, which has shown encouraging outcomes in phase I clinical trials of relapsed/refractory NHL. However, the underlying mechanisms of, and approaches to overcome, acquired anti-CD19CAR CD8⁺ T cells (CTL)-resistance in NHL remain elusive. CD19CAR transduced primary human CTLs kill CD19⁺ human NHLs in a CD19- and caspase-dependent manner, mainly via the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) apoptotic pathway. To understand the dynamics of the development of resistance, we analyzed several anti-CD19CAR CTL-resistant NHL sublines (R-NHL) derived by serial exposure of sensitive parental lines to excessive numbers of anti-CD19CAR CTLs followed by a limiting dilution analysis. The R-NHLs retained surface CD19 expression and were efficiently recognized by CD19CAR CTLs. However, R-NHLs developed cross-resistance to CD19CAR transduced human primary CTLs and the Jurkat human T cell line, activated Jurkat, and lymphokine activated killer (LAK) cells, suggesting the acquisition of resistance is independent of CD19-loss and might be due to aberrant apoptotic machinery. We hypothesize that the R-NHL refractoriness to CD19CAR CTL killing could be partially rescued by small molecule sensitizers with apoptotic-gene regulatory effects. Chromatin modifiers and Celecoxib partially reversed the resistance of R-NHL cells to the cytotoxic effects of anti-CD19CAR CTLs and rhTRAIL. These in vitro results, though they require further examination, may provide a rational biological basis for combination treatment in the management of CD19CAR CTL-based therapy of NHL.

Engineered MBP-specific human Tregs ameliorate MOG-induced EAE through IL-2-triggered inhibition of effector T cells

Expanded polyclonal T regulatory cells (Tregs) offer great promise for the treatment of immune-mediated diseases. Inhibition by Tregs is under the control of the T-cell receptor (TCR). Therefore, we created Tregs with defined antigen specificity, using a recombinant T-cell receptor isolated from a myelin-basic protein specific T-cell clone of a multiple sclerosis (MS) patient (Ob2F3). We expressed this TCR using a retroviral expression vector in human Tregs from peripheral blood. We observed that transduced Tregs were activated in vitro in response to myelin basic protein (MBP) peptide on DR15 antigen-presenting cells (APC) and upregulated Treg markers, Foxp3, LAP and Helios. These engineered MBP-specific Tregs could suppress MBP-specific T effector cells, and were also able to suppress T cells with other specificities after Tregs had been activated through the TCR. Importantly, we showed that these engineered Tregs were able to function effectively in the presence of strong TLR-induced inflammatory signals, and that MBP-specific Tregs ameliorated EAE in myelin oligodendrocyte glycoprotein (MOG)-immunized DR15 transgenic mice. We further demonstrated in vitro that IL-2 produced by neighboring effector T cells activated MBP-specific Tregs, initiating contact-independent suppression to T effectors in local milieu. Mechanistic studies demonstrated that bystander suppression in vivo may involve transfer of soluble mediators, enhanced by cell contact between Tregs and effectors. Taken together, we show that engineered clonal MBP-specific Tregs are able to suppress autoimmune pathology in EAE. This approach may serve as a cellular therapy for MS patients with the common DR15 haplotype that is associated with disease susceptibility.

Chimeric antigen receptor T-cell therapy for glioblastoma

Chimeric antigen receptor (CAR) T-cell therapy has shown great promise in the treatment of hematological disease, and its utility for treatment of solid tumors is beginning to unfold. Glioblastoma continues to portend a grim prognosis and immunotherapeutic approaches are being explored as a potential treatment strategy. Identification of appropriate glioma-associated antigens, barriers to cell delivery, and presence of an immunosuppressive microenvironment are factors that make CAR T-cell therapy for glioblastoma particularly challenging. However, insights gained from preclinical studies and ongoing clinical trials indicate that CAR T-cell therapy will continue to evolve and likely become integrated with current therapeutic strategies for malignant glioma.

Combination of celecoxib (Celebrex®) and CD19 CAR-redirected CTL immunotherapy for the treatment of B-cell non-Hodgkin's lymphomas

The nonsteroidal anti-inflammatory drug (NSAID) Celecoxib (Celebrex^®) received Food and Drug Administration (FDA) approval in 1998 for treatment of osteoarthritis and rheumatoid arthritis, and in recent years, its use has been extended to various types of malignancies, such as breast, colon, and urinary cancers. To maintain the survival of malignant B cells, non-Hodgkin's Lymphoma (NHL) is highly dependent on inflammatory microenvironment, and is inhibited by celecoxib. Celecoxib hinders tumor growth interacting with various apoptotic genes, such as cyclooxygenase-2 (Cox-2), B-cell lymphoma 2 (Bcl-2) family, phosphor-inositide-3 kinase/serine-threonine-specific protein kinase (PI3K/Akt), and inhibitors of apoptosis proteins (IAP) family. CD19-redirected chimeric antigen-receptor (CD19 CAR) T cell therapy has shown promise in the treatment of B cell malignancies. Considering its regulatory effect on apoptotic gene products in various tumor types, Celecoxib is a promising drug to be used in combination with CD19 CAR T cell therapy to optimize immunotherapy of NHL.

Current status and perspectives of chimeric antigen receptor modified T cells for cancer treatment

Chimeric antigen receptor (CAR) is a recombinant immunoreceptor combining an antibody-derived targeting fragment with signaling domains capable of activating cells, which endows T cells with the ability to recognize tumor-associated surface antigens independent of the expression of major histocompatibility complex (MHC) molecules. Recent early-phase clinical trials of CAR-modified T (CAR-T) cells for relapsed or refractory B cell malignancies have demonstrated promising results (that is, anti-CD19 CAR-T in B cell acute lymphoblastic leukemia (B-ALL)). Given this success, broadening the clinical experience of CAR-T cell therapy beyond hematological malignancies has been actively investigated. Here we discuss the basic design of CAR and review the clinical results from the studies of CAR-T cells in B cell leukemia and lymphoma, and several solid tumors. We additionally discuss the major challenges in the further development and strategies for increasing anti-tumor activity and safety, as well as for successful commercial translation.

Efficacy and toxicity management of CAR-T-cell immunotherapy: a matter of responsiveness control or tumour-specificity?

Chimaeric antigen receptor (CAR)-expressing T-cells have demonstrated potent clinical efficacy in patients with haematological malignancies. However, the use of CAR-T-cells targeting solid tumour-associated antigens (TAAs) has been limited by organ toxicities related to activation of T-cell effector functions through the CAR. Most existing CARs recognize TAAs, which are also found in normal tissues. CAR-T-cell-mediated destruction of normal tissues constitutes a major roadblock to CAR-T-cell therapy, and must be avoided or mitigated. There is a broad range of strategies for modulating antigen responsiveness of CAR-T-cells, with varying degrees of complexity. Some of them might ameliorate the acute and chronic toxicities associated with current CAR constructs. However, further embellishments to CAR therapy may complicate clinical implementation and possibly create new immunogenicity issues. In contrast, the development of CARs targeting truly tumour-specific antigens might circumvent on-target/off-tumour toxicities without adding additional complexity to CAR-T-cell therapies, but these antigens have been elusive and may require novel selection strategies for their discovery.

Therapeutic Potential of T Cell Chimeric Antigen Receptors (CARs) in Cancer Treatment: Counteracting Off-Tumor Toxicities for Safe CAR T Cell Therapy

A chimeric antigen receptor (CAR) is a recombinant fusion protein combining an antibody-derived targeting fragment with signaling domains capable of activating T cells. Recent early-phase clinical trials have demonstrated the remarkable ability of CAR-modified T cells to eliminate B cell malignancies. This review describes the choice of target antigens and CAR manipulations to maximize antitumor specificity. Benefits and current limitations of CAR-modified T cells are discussed, with a special focus on the distribution of tumor antigens on normal tissues and the risk of on-target, off-tumor toxicities in the clinical setting. We present current methodologies for pre-evaluating these risks and review the strategies for counteracting potential off-tumor effects. Successful implementation of these approaches will improve the safety and efficacy of CAR T cell therapy and extend the range of cancer patients who may be treated.

Patient-derived glioblastoma stem cells are killed by CD133-specific CAR T cells but induce the T cell aging marker CD57

The AC133 epitope of CD133 is a cancer stem cell (CSC) marker for many tumor entities, including the highly malignant glioblastoma multiforme (GBM). We have developed an AC133-specific chimeric antigen receptor (CAR) and show that AC133-CAR T cells kill AC133+ GBM stem cells (GBM-SCs) both in vitro and in an orthotopic tumor model in vivo. Direct contact with patient-derived GBM-SCs caused rapid upregulation of CD57 on the CAR T cells, a molecule known to mark terminally or near-terminally differentiated T cells. However, other changes associated with terminal T cell differentiation could not be readily detected. CD57 is also expressed on tumor cells of neural crest origin and has been preferentially found on highly aggressive, undifferentiated, multipotent CSC-like cells. We found that CD57 was upregulated on activated T cells only upon contact with CD57+ patient-derived GBM-SCs, but not with conventional CD57-negative glioma lines. However, CD57 was not downregulated on the GBM-SCs upon their differentiation, indicating that this molecule is not a bona fide CSC marker for GBM. Differentiated GBM cells still induced CD57 on CAR T cells and other activated T cells. Therefore, CD57 can apparently be upregulated on activated human T cells by mere contact with CD57+ target cells.

Rapid and efficient transfer of the T cell aging marker CD57 from glioblastoma stem cells to CAR T cells

Adoptive transfer of T cells expressing chimeric antigen receptors (CARs) holds great promise for cancer treatment. We recently developed CAR T cells targeting the prototypic cancer stem cell marker AC133 and showed that these CAR T cells killed AC133+ glioblastoma stem cells (GBM-SCs) in vitro and inhibited the growth of brain tumors initiated from GBM-SCs in xenograft mouse models in vivo. Upon coincubation with GBM-SCs, we observed strong upregulation of the T cell aging marker CD57, but other phenotypical or functional changes usually associated with terminal T cell differentiation could not immediately be detected. Here, we provide evidence suggesting that CD57 is rapidly and efficiently transferred from CD57+ GBM-SCs to preactivated T cells and that the transfer is greatly enhanced by specific CAR/ligand interaction. After separation from CD57+ tumor cells, CD57 epitope expression on T cells decreased only slowly over several days. We conclude that CD57 transfer from tumor cells to T cells may occur in patients with CD57+ tumors and that it may have to be considered in the interpretation of phenotyping results for tumor-infiltrating lymphocytes and perhaps also in the characterization of tumor-specific T cells from tumor or lymph node homogenates or peripheral blood mononuclear cells.