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

Genome engineering and disease modeling via programmable nucleases for insulin gene therapy: Promises of CRISPR/Cas9 technology

Targeted genome editing is a continually evolving technology employing programmable nucleases to specifically change, insert, or remove a genomic sequence of interest. These advanced molecular tools include meganucleases, zinc finger nucleases, transcription activator-like effector nucleases and RNA-guided engineered nucleases (RGENs), which create double-strand breaks at specific target sites in the genome, and repair DNA either by homologous recombination in the presence of donor DNA or via the error-prone non-homologous end-joining mechanism. A recently discovered group of RGENs known as CRISPR/Cas9 gene-editing systems allowed precise genome manipulation revealing a causal association between disease genotype and phenotype, without the need for the reengineering of the specific enzyme when targeting different sequences. CRISPR/Cas9 has been successfully employed as an ex vivo gene-editing tool in embryonic stem cells and patient-derived stem cells to understand pancreatic beta-cell development and function. RNA-guided nucleases also open the way for the generation of novel animal models for diabetes and allow testing the efficiency of various therapeutic approaches in diabetes, as summarized and exemplified in this manuscript.

A Deep Insight Into CAR-T Cell Therapy in Non-Hodgkin Lymphoma: Application, Opportunities, and Future Directions

Non-Hodgkin's lymphoma (NHL) is a cancer that starts in the lymphatic system. In NHL, the important part of the immune system, a type of white blood cells called lymphocytes become cancerous. NHL subtypes include marginal zone lymphoma, small lymphocytic lymphoma, follicular lymphoma (FL), and lymphoplasmacytic lymphoma. The disease can emerge in either aggressive or indolent form. 5-year survival duration after diagnosis is poor among patients with aggressive/relapsing form of NHL. Therefore, it is necessary to understand the molecular mechanisms of pathogenesis involved in NHL establishment and progression. In the next step, we can develop innovative therapies for NHL based on our knowledge in signaling pathways, surface antigens, and tumor milieu of NHL. In the recent few decades, several treatment solutions of NHL mainly based on targeted/directed therapies have been evaluated. These approaches include B-cell receptor (BCR) signaling inhibitors, immunomodulatory agents, monoclonal antibodies (mAbs), epigenetic modulators, Bcl-2 inhibitors, checkpoint inhibitors, and T-cell therapy. In recent years, methods based on T cell immunotherapy have been considered as a novel promising anti-cancer strategy in the treatment of various types of cancers, and particularly in blood cancers. These methods could significantly increase the capacity of the immune system to induce durable anti-cancer responses in patients with chemotherapy-resistant lymphoma. One of the promising therapy methods involved in the triumph of immunotherapy is the chimeric antigen receptor (CAR) T cells with dramatically improved killing activity against tumor cells. The CAR-T cell-based anti-cancer therapy targeting a pan-B-cell marker, CD19 is recently approved by the US Food and Drug Administration (FDA) for the treatment of chemotherapy-resistant B-cell NHL. In this review, we will discuss the structure, molecular mechanisms, results of clinical trials, and the toxicity of CAR-T cell-based therapies. Also, we will criticize the clinical aspects, the treatment considerations, and the challenges and possible drawbacks of the application of CAR-T cells in the treatment of NHL.

Therapeutic Gene Editing with CRISPR: A Laboratory Medicine Perspective

Therapeutic gene editing with the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas system offers significant improvements in specificity and programmability compared with previous methods. CRISPR editing strategies can be used ex vivo and in vivo with many theoretic disease applications. Off-target effects of CRISPR-mediated gene editing are an important outcome to be aware of, minimize, and detect. The current methods of regulatory approval for personalized therapies are complex and may be proved inefficient as these therapies are implemented more widely. The role of pathologists and laboratory medicine practitioners is vital to the clinical implementation of therapeutic gene editing.

CD38-specific Chimeric Antigen Receptor Expressing Natural Killer KHYG-1 Cells: A Proof of Concept for an "Off the Shelf" Therapy for Multiple Myeloma

Chimeric antigen receptor (CAR) T cells are highly successful in the treatment of hematologic malignancies. We recently generated affinity-optimized CD38CAR T cells, which effectively eliminate multiple myeloma (MM) cells with little or no toxicities against nonmalignant hematopoietic cells. The lack of universal donors and long manufacturing times however limit the broad application of CAR T cell therapies. Natural killer (NK) cells generated from third party individuals may represent a viable source of "off the shelf" CAR-based products, as they are not associated with graft-versus-host disease unlike allogeneic T cells. We therefore explored the preclinical anti-MM efficacy and potential toxicity of the CD38CAR NK concept by expressing affinity-optimized CD38CARs in KHYG-1 cells, an immortal NK cell line with excellent expansion properties. KHYG-1 cells retrovirally transduced with the affinity-optimized CD38CARs expanded vigorously and mediated effective CD38-dependent cytotoxicity towards CD38^high MM cell lines as well as primary MM cells ex vivo. Importantly, the intermediate affinity CD38CAR transduced KHYG-1 cells spared CD38^neg or CD38^int nonmalignant hematopoietic cells, indicating an optimal tumor nontumor discrimination. Irradiated, short living CD38CAR KHYG-1 cells also showed significant anti-MM effects in a xenograft model with a humanized bone marrow-like niche. Finally, CD38CAR KHYG-1 cells effectively eliminated primary MM cells derived from patients who are refractory to CD38 antibody daratumumab. Taken together, the results of this proof-of-principle study demonstrate the potential value of engineering affinity-optimized CD38CARs in NK cells to establish effective anti-MM effects, with an excellent safety profile, even in patients who failed to response to most advanced registered myeloma therapies, such as daratumumab.

Avoiding Stops and Overcoming Roadblocks: Considerations for Improving Patient Access to CAR-Based Cell Therapies

Adoptive cell therapy has significantly impacted the immuno-oncology landscape. The number of strategies currently in preclinical and clinical development is increasing at a rapid rate. Indeed, we are experiencing a transformative movement in cancer care as we shift toward highly personalized treatments designed to confront the specific challenges of each cancer. Advancements in genetic engineering methods and single-cell profiling technologies provide a level of understanding of the interactions between the immune system and cancer never before achieved. This knowledge, in turn, can be applied to the design and engineering of effective cancer-fighting treatments. As these promising new therapies progress toward clinical application, it becomes evident that we must develop robust methods for production and validation of cellular products to ensure consistency, safety, and efficacy, irrespective of cell type or indication. Herein, we provide an overview of the innovative approaches guiding the new generation of cell therapies and describe the benefits and challenges associated with emerging autologous and allogeneic platforms. Moreover, we discuss important considerations pertaining to process development, cost of goods, and manufacturing, and highlight their impact on the transfer of therapies from bench to bedside.

Approaches for refining and furthering the development of CAR-based T cell therapies for solid malignancies

Introduction: Chimeric antigen receptor-engineered T-cells typically use the binding domains of antibodies to target cytotoxicity toward tumors. This approach has produced great efficacy against selected hematological cancers, but benefit in solid tumors has been limited. Characteristically, the microenvironment in solid tumors restricts CAR T cell function, thereby limiting success. Enhancing efficacy will depend on novel target discovery to refine specificity and reduce toxicity. Additionally, overcoming immunosuppressive mechanisms may be achieved by altering the structure of the CAR itself, together with ancillary gene expression or additional therapeutic interventions.Areas covered: Herein, the authors discuss approaches for refining and further developing CAR T cell therapies specifically for use with solid malignancies. The authors survey the existing literature and provide perspectives for the future.Expert opinion: Pronounced efficacy in solid tumors will likely require combination therapies, targeting both the tumor itself and associated immunosuppressive mechanisms. Future exploration of CAR T cell therapies for solid tumors is likely to incorporate next-generation designs that couple more precise targeting of cancer-associated targets with enhanced potency and resistance to exhaustion.

Graft-versus-host disease risk after chimeric antigen receptor T-cell therapy: the diametric opposition of T cells

Chimeric antigen receptor (CAR) T-cell therapy has brought a paradigm shift in the management of haematological malignancies and has opened novel avenues of investigational therapeutic strategies. Given these encouraging responses, it has become imperative to understand the full spectrum of biology and potential toxicities that can arise from these novel agents, as well as those under investigation. With the increasing use of CAR T-cell therapy for relapse following allogeneic haematopoietic cell transplantation (HCT) and the imminence of allogeneic CAR T cells, risks from T cell-based therapy, such as the previously well-recognised graft-versus-host disease (GVHD), have gained prominence and warrant explanation. In the present review, we discuss the risk of GVHD in the: (1) post-HCT setting using recipient or donor-derived CAR T cells, as well as (2) non-HCT setting using autologous, as well as allogeneic T-cell therapies. A better understanding of this risk is important to advance the field and ensure safe development and use of these agents in the clinic.

CRISPR/Cas9 Gene-Editing in Cancer Immunotherapy: Promoting the Present Revolution in Cancer Therapy and Exploring More

In recent years, immunotherapy has showed fantastic promise in pioneering and accelerating the field of cancer therapy and embraces unprecedented breakthroughs in clinical practice. The clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein 9 (CRISPR-Cas9) system, as a versatile gene-editing technology, lays a robust foundation to efficiently innovate cancer research and cancer therapy. Here, we summarize recent approaches based on CRISPR/Cas9 system for construction of chimeric antigen receptor T (CAR-T) cells and T cell receptor T (TCR-T) cells. Besides, we review the applications of CRISPR/Cas9 in inhibiting immune checkpoint signaling pathways and highlight the feasibility of CRISPR/Cas9 based engineering strategies to screen novel cancer immunotherapy targets. Conclusively, we discuss the perspectives, potential challenges and possible solutions in this vivid growing field.

How Can We Engineer CAR T Cells to Overcome Resistance?

Chimeric antigen receptor (CAR) T cell therapy has achieved unrivalled success in the treatment of B cell and plasma cell malignancies, with five CAR T cell products now approved by the US Food and Drug Administration (FDA). However, CAR T cell therapies for solid tumours have not been nearly as successful, owing to several additional challenges. Here, we discuss mechanisms of tumour resistance in CAR T cell therapy and the emerging strategies that are under development to engineer CAR T cells to overcome resistance.

Cell therapy in transplantation: A comprehensive review of the current applications of cell therapy in transplant patients with the focus on Tregs, CAR Tregs, and Mesenchymal stem cells

Organ transplantation is a practical treatment for patients with end-stage organ failure. Despite the advances in short-term graft survival, long-term graft survival remains the main challenge considering the increased mortality and morbidity associated with chronic rejection and the toxicity of immunosuppressive drugs. Since a novel therapeutic strategy to induce allograft tolerance seems urgent, focusing on developing novel and safe approaches to prolong graft survival is one of the main goals of transplant investigators. Researchers in the field of organ transplantation are interested in suppressing or optimizing the immune responses by focusing on immune cells including mesenchymal stem cells (MSCs), polyclonal regulatory Tcells (Tregs), and antigen-specific Tregs engineered with chimeric antigen receptors (CAR Tregs). We review the mechanistic pathways, phenotypic and functional characteristics of these cells, and their promising application in organ transplantation.

[Chimeric antigen receptors (CARs): universal tools in adoptive cell therapy]

BACKGROUND

The observation that tumor-infiltrating lymphocytes (TIL) after ex vivo amplification can control tumors in the long term led to the concept of redirecting patients' cytolytic T‑cells by a receptor with defined specificity against the tumor.

OBJECTIVES

Development of a recombinant receptor-signal molecule (chimeric antigen receptor, CAR) to increase selectivity and enhance anti-tumor immunity.

METHODS

Description of a prototype CAR, overview of the modular composition and further development of CAR technology for use in adoptive immune cell therapy.

RESULTS

Intensive research over the last two decades has shown how CAR-mediated T‑cell activation is influenced by factors such as binding affinity, the epitope of the target antigen, its expression density and accessibility on the tumor cells, as well as by the signaling domains and their combination to induce T‑cell activation. The quality and duration of the T‑cell response can be specifically modulated by modifying the modular composition of the CAR; CAR T‑cells can act as "biopharmaceutical factories" (T-cells redirected for unrestricted cytokine-mediated killing, TRUCK) in the tissue by CAR-mediated release of transgenic therapeutic proteins.

CONCLUSION

Adoptive CAR T‑cell therapy has shown clinical efficacy in the treatment of hematological malignancies; the treatment of solid tumors, however, is more challenging. Allogeneic CAR T‑cell technology is aimed at generating "off-the-shelf" CAR T‑cells that are accessible for a large number of patients. A further promising approach is the use of CAR T‑cells for other therapeutic applications such as the treatment of autoimmune diseases.

Non-viral transfection technologies for next-generation therapeutic T cell engineering

Genetically engineered T cells have sparked interest in advanced cancer treatment, reaching a milestone in 2017 with two FDA-approvals for CD19-directed chimeric antigen receptor (CAR) T cell therapeutics. It is becoming clear that the next generation of CAR T cell therapies will demand more complex engineering strategies and combinations thereof, including the use of revolutionary gene editing approaches. To date, manufacturing of CAR T cells mostly relies on γ-retroviral or lentiviral vectors, but their use is associated with several drawbacks, including safety issues, high manufacturing cost and vector capacity constraints. Non-viral approaches, including membrane permeabilization and carrier-based techniques, have therefore gained a lot of interest to replace viral transductions in the manufacturing of T cell therapeutics. This review provides an in-depth discussion on the avid search for alternatives to viral vectors, discusses key considerations for T cell engineering technologies, and provides an overview of the emerging spectrum of non-viral transfection technologies for T cells. Strengths and weaknesses of each technology will be discussed in relation to T cell engineering. Altogether, this work emphasizes the potential of non-viral transfection approaches to advance the next-generation of genetically engineered T cells.

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.

Delivery technologies for T cell gene editing: Applications in cancer immunotherapy

While initial approaches to adoptive T cell therapy relied on the identification and expansion of rare tumour-reactive T cells, genetic engineering has transformed cancer immunotherapy by enabling the modification of primary T cells to increase their therapeutic potential. Specifically, gene editing technologies have been utilized to create T cell populations with improved responses to antigens, lower rates of exhaustion, and potential for use in allogeneic applications. In this review, we provide an overview of T cell therapy gene editing strategies and the delivery technologies utilized to genetically engineer T cells. We also discuss recent investigations and clinical trials that have utilized gene editing to enhance the efficacy of T cells and broaden the application of cancer immunotherapies.

Immunotherapy to get on point with base editing

Engineered immune cell therapy is revolutionising the field of cancer therapeutics. US Food and Drug Administration (FDA) approval of two chimeric antigen receptor (CAR)-T cell products for the treatment of haematological malignancies paved the way for individualised cancer treatment. However, multiple genetic edits will be required to improve the efficacy of CAR-T cell therapies if they are to treat refractory malignancies successfully, particularly solid tumours. Off-target effects of CRISPR-Cas9-mediated multiplex editing are likely to hinder its safety and application in the clinic. Novel base editing technologies offer a promising and safer alternative for simultaneous editing that could enhance allogeneic engineered immunotherapies for targeting solid tumours and other complex human diseases.

CAR-T cells and BiTEs in solid tumors: challenges and perspectives

Chimeric antigen receptor (CAR)-modified T cells and BiTEs are both immunotherapies which redirect T cell specificity against a tumor-specific antigen through the use of antibody fragments. They demonstrated remarkable efficacy in B cell hematologic malignancies, thus paving the way for their development in solid tumors. Nonetheless, the use of such new drugs to treat solid tumors is not straightforward. So far, the results from early phase clinical trials are not as impressive as expected but many improvements are under way. In this review we present an overview of the clinical development of CAR-T cells and BiTEs targeting the main antigens expressed by solid tumors. We emphasize the most frequent hurdles encountered by either CAR-T cells or BiTEs, or both, and summarize the strategies that have been proposed to overcome these obstacles.

Current Perspectives on the Use of off the Shelf CAR-T/NK Cells for the Treatment of Cancer

Simple Summary

CAR T cells are a type of immunotherapy whereby a patient’s own cells are genetically modified to recognise and kill the patient’s own cancer cells. Currently, each patient has CAR T cells made from their own blood cells. This type of therapy has had a big impact on the treatment of blood cancers, however making an individual treatment from each patient is expensive and labour intensive. This review discusses the potential of making CAR T cells more widely available by producing them in large numbers from healthy donors.

Abstract

CAR T cells have revolutionised the treatment of haematological malignancies. Despite this, several obstacles still prohibit their widespread use and efficacy. One of these barriers is the use of autologous T cells as the carrier of the CAR. The individual production of CAR T cells results in large variation in the product, greater wait times for treatment and higher costs. To overcome this several novel approaches have emerged that utilise allogeneic cells, so called “off the shelf” CAR T cells. In this Review, we describe the different approaches that have been used to produce allogeneic CAR T to date, as well as their current pre-clinical and clinical progress.

Cellular Therapy and Cytokine Treatments for Melanoma

Cancer immunotherapy plays an important role in the treatment of patients with advanced stage melanoma. Recombinant cytokines were the first tested and approved treatments; however, due to disappointing response rates and severe toxicities, their use has significantly decreased. More recently, adoptive cell transfer therapies have shown to be a promising new treatment strategy able to induce complete and durable remissions in patients with melanoma progressive on first-line treatment. This review provides an overview of the cellular therapies (tumor-infiltrating lymphocytes, T-cell receptor T cells, chimeric antigen receptor T cells) and cytokine treatments (interleukin-2 [IL-2], IL-15, IL-7, IL-10, IL-21, interferon alpha, granulocyte-macrophage colony-stimulating factor) for melanoma.

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.

Genome editing of donor-derived T-cells to generate allogenic chimeric antigen receptor-modified T cells: Optimizing αβ T cell-depleted haploidentical hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation is an effective therapy for high-risk leukemias. In children, graft manipulation based on the selective removal of αβT cells and B cells has been shown to reduce the risk of acute and chronic graft-versus-host disease, thus allowing the use of haploidentical donors which expands the population of recipients in whom allogeneic hematopoietic stem cell transplantation can be used. Leukemic relapse, however, remains a challenge. T cells expressing chimeric antigen receptors can potently eliminate leukemia, including those in the central nervous system. We hypothesized that by engineering the donor αβT cells that are removed from the graft by genome editing to express a CD19-specific chimeric antigen receptor, while simultaneously inactivating the T-cell receptor, we could create a therapy that enhances the anti-leukemic efficacy of the stem cell transplant without increasing the risk of graft-versus-host disease. Using genome editing with Cas9 ribonucleoprotein and adeno-associated virus serotype 6, we integrated a CD19-specific chimeric antigen receptor inframe into the TRAC locus. More than 90% of cells lost T-cell receptor expression, while >75% expressed the chimeric antigen receptor. The initial product was further purified with less than 0.05% T-cell receptorpositive cells remaining. In vitro, the chimeric antigen receptor T cells efficiently eliminated target cells and produced high cytokine levels when challenged with CD19⁺ leukemia cells. In vivo, the gene-modified T cells eliminated leukemia without causing graft-versus-host disease in a xenograft model. Gene editing was highly specific with no evidence of off-target effects. These data support the concept that the addition of αβ T-cell-derived, genome-edited T cells expressing CD19-specific chimeric antigen receptors could enhance the anti-leukemic efficacy of αβT-celldepleted haploidentical hematopoietic stem cell transplantation without increasing the risk of graft-versus-host disease.

Taking T-Cell Oncotherapy Off-the-Shelf

Banked allogeneic or 'off-the-shelf' (OTS) T cells from healthy human donors are being developed to address the limitations of autologous cell therapies. Potential challenges of OTS T cell therapies are associated with their allogeneic origin and the possibility of graft-versus-host disease (GvHD) and host-versus-graft immune reactions. While the risk of GvHD from OTS T cells has been proved to be manageable in clinical studies, approaches to prevent immune rejection of OTS cells are at an earlier stage of development. We provide an overview of strategies to generate OTS cell therapies and mitigate alloreactivity-associated adverse events, with a focus on recent advances for preventing immune rejection.

CRISPR/Cas-Dependent and Nuclease-Free In Vivo Therapeutic Gene Editing

Precise gene manipulation by gene editing approaches facilitates the potential to cure several debilitating genetic disorders. Gene modification stimulated by engineered nucleases induces a double-stranded break (DSB) in the target genomic locus, thereby activating DNA repair mechanisms. DSBs triggered by nucleases are repaired either by the nonhomologous end-joining or the homology-directed repair pathway, enabling efficient gene editing. While there are several ongoing ex vivo genome editing clinical trials, current research underscores the therapeutic potential of CRISPR/Cas-based (clustered regularly interspaced short palindrome repeats-associated Cas nuclease) in vivo gene editing. In this review, we provide an overview of the CRISPR/Cas-mediated in vivo genome therapy applications and explore their prospective clinical translatability to treat human monogenic disorders. In addition, we discuss the various challenges associated with in vivo genome editing technologies and strategies used to circumvent them. Despite the robust and precise nuclease-mediated gene editing, a promoterless, nuclease-independent gene targeting strategy has been utilized to evade the drawbacks of the nuclease-dependent system, such as off-target effects, immunogenicity, and cytotoxicity. Thus, the rapidly evolving paradigm of gene editing technologies will continue to foster the progress of gene therapy applications.

Off-the-Shelf Chimeric Antigen Receptor T Cells: How Do We Get There?

ABSTRACT

Banked chimeric antigen receptor (CAR) T cells immediately available for off-the-shelf (OTS) application can solve key limitations of patient-specific CAR T-cell products while retaining their potency. The allogeneic nature of OTS cell therapies requires additional measures to minimize graft-versus-host disease and host-versus-graft immune rejection in immunocompetent recipients. In this review, we discuss engineering and manufacturing strategies aimed at minimizing unwanted interactions between allogeneic CAR T cells and the host. Overcoming these limitations will improve safety and antitumor potency of OTS CAR T cells and facilitate their wider use in cancer therapy.

CRISPR/Cas9-Engineered Universal CD19/CD22 Dual-Targeted CAR-T Cell Therapy for Relapsed/Refractory B-cell Acute Lymphoblastic Leukemia

PURPOSE

Autologous chimeric antigen receptor T (CAR-T) cell therapy is an effective treatment for relapsed/refractory acute lymphoblastic leukemia (r/r ALL). However, certain characteristics of autologous CAR-T cells can delay treatment availability. Relapse caused by antigen escape after single-targeted CAR-T therapy is another issue. Therefore, we aim to develop CRISPR-edited universal off-the-shelf CD19/CD22 dual-targeted CAR-T cells as a novel therapy for r/r ALL.

PATIENTS AND METHODS

In this open-label dose-escalation phase I study, universal CD19/CD22-targeting CAR-T cells (CTA101) with a CRISPR/Cas9-disrupted TRAC region and CD52 gene to avoid host immune-mediated rejection were infused in patients with r/r ALL. Safety, efficacy, and CTA101 cellular kinetics were evaluated.

RESULTS

CRISPR/Cas9 technology mediated highly efficient, high-fidelity gene editing and production of universal CAR-T cells. No gene editing-associated genotoxicity or chromosomal translocation was observed. Six patients received CTA101 infusions at doses of 1 (3 patients) and 3 (3 patients) × 10⁶ CAR⁺ T cells/kg body weight. Cytokine release syndrome occurred in all patients. No dose-limiting toxicity, GvHD, neurotoxicity, or genome editing-associated adverse events have occurred to date. The complete remission (CR) rate was 83.3% on day 28 after CTA101 infusion. With a median follow-up of 4.3 months, 3 of the 5 patients who achieved CR or CR with incomplete hematologic recovery (CR/CRi) remained minimal residual disease (MRD) negative.

CONCLUSIONS

CRISPR/Cas9-engineered universal CD19/CD22 CAR-T cells exhibited a manageable safety profile and prominent antileukemia activity. Universal dual-targeted CAR-T cell therapy may offer an alternative therapy for patients with r/r ALL.

A Review of Clinical Outcomes of CAR T-Cell Therapies for B-Acute Lymphoblastic Leukemia

Introduction: Treatment of relapsed and refractory (R/R) B acute lymphoblastic leukemia (B-ALL) represents an unmet medical need in children and adults. Adoptive T cells engineered to express a chimeric antigen receptor (CAR-T) is emerging as an effective technique for treating these patients. Areas covered: Efficacy and safety of CAR-T therapy in R/R B-ALL patients. Expert opinion: CD19 CAR-T infusion induce high CR rates in patients with poor prognosis and few therapeutic options, while real-life data demonstrate similar results with an interestingly lower incidence of grade 3/4 toxicity. Nevertheless, despite impressive in-depth responses, more than half of patients will experience a relapse. Therefore, rather than using CAR-T cell therapy as a stand-alone option, consolidation with allogeneic stem-cell transplant (Allo-SCT) after CAR-T treatment might increase long-term outcome. Moreover, CD19 is one target, but several other targets are being examined, such as CD20 and CD22 and dual-targeting CARs or combination therapy. Another issue is the time consuming process of CAR-T engineering. New platforms have shortened the CAR-T cell manufacturing process, and studies are underway to evaluate the effectiveness. Another way to mitigate waiting is the development of allogeneic “off the shelf” therapy. In conclusion, CD19-targeted CAR-modified T-cell therapy has shown unprecedented results in patients without curative options. Future work focusing on target identification, toxicity management and reducing manufacturing time will broaden the clinical applicability and bring this exciting therapy to more patients, with longer-term remissions without additional Allo-SCT.

CRISPR-Cas9 in cancer therapeutics

Cancer is a disease mainly caused by an accumulation of mutations in cells. Consequently, correcting those genetic aberrations could be a potential treatment strategy. The traditional route for cancer drug development is tedious, laborious, and time-consuming. Due to target identification, drug formulation, pre-clinical testing, clinical testing, and regulatory hurdles, on average, it takes 10-15 years for a cancer drug to go from target discovery to a marketable oncology drug. The advent of CRISPR-Cas9 technology has greatly expedited this procedure. CRISPR-Cas9 has single-handedly accelerated target identification and pre-clinical testing. Furthermore, CRISPR-Cas9 has also been used in ex vivo editing of T-cells to specifically target tumor cells. In this chapter, we will discuss the various ways in which CRISPR-Cas9 has been used for the betterment of the cancer drug development process. Additionally, we will discuss various ways in which it is currently being used as therapy and the drawbacks which restrict the use of this groundbreaking technology as direct therapy.

Current State of the Art of Allogeneic CAR Approaches - Pile 'Em High and Sell 'Em Cheap

The advent and rapid propagation of Chimeric Antigen Receptor (CAR)-based therapeutics in recent years has taken the oncology field by storm and delivered considerable benefit to cancer patients, many of whom previously had no other treatment options available to them. CAR-based therapies are now a bona fide therapeutic modality in the fight against cancer, along with more "traditional" treatments, such as small molecule and antibody drugs. For the technology to take the next step and reach much larger numbers of patients in need, it will be necessary for those treatments to become "off-the-shelf" offering patients a standardised, consistent, and cost-effective product. This article offers an overview of the evolution and development options for off-the-shelf CAR-based treatments, the advantages and disadvantages of the various approaches, along with key optimisation parameters that must be considered.

Targeted multi-epitope switching enables straightforward positive/negative selection of CAR T cells

Chimeric antigen receptor (CAR) T cell technology has enabled successfully novel concepts to treat cancer patients, with substantial remission rates in lymphoid malignancies. This cell therapy is based on autologous T lymphocytes that are genetically modified to express a CAR that recognizes tumor-associated antigens and mediates the elimination of the respective tumor cells. Current limitations include laborious manufacturing procedures as well as severe immunological side effects upon administration of CAR T cells. To address these limitations, we integrated RQR8, a multi-epitope molecule harboring a CD34 epitope and two CD20 mimotopes, alongside a CD19-targeting CAR, into the CD52 locus. Using CRISPR-Cas9 and adeno-associated virus-based donor vectors, some 60% of genome-edited T cells were CAR⁺/CD20⁺/CD34⁺/CD52⁻ without further selection. This could be increased to >95% purity after CD34 tag-based positive selection. These epitope-switched CAR T cells retained cell killing competence against CD19⁺ tumor cells, and were resistant to alemtuzumab (anti-CD52) but sensitive to rituximab (anti-CD20) in complement-dependent cytotoxicity assays. In conclusion, gene editing-based multiple epitope switching represents a promising development with the potential to improve both the manufacturing procedure as well as the clinical safety of CAR T cells.

CRISPR/Cas9-mediated knockout of clinically relevant alloantigenes in human primary T cells

Background

The ability of CRISPR/Cas9 to mutate any desired genomic locus is being increasingly explored in the emerging area of cancer immunotherapy. In this respect, current efforts are mostly focused on the use of autologous (i.e. patient-derived) T cells. The autologous approach, however, has drawbacks in terms of manufacturing time, cost, feasibility and scalability that can affect therapeutic outcome or wider clinical application. The use of allogeneic T cells from healthy donors may overcome these limitations. For this strategy to work, the endogenous T cell receptor (TCR) needs to be knocked out in order to reduce off-tumor, graft-versus-host-disease (GvHD). Furthermore, CD52 may be knocked out in the donor T cells, since this leaves them resistant to the commonly used anti-CD52 monoclonal antibody lymphodepletion regimen aiming to suppress rejection of the infused T cells by the recipient. Despite the great prospect, genetic manipulation of human T cells remains challenging, in particular how to deliver the engineering reagents: virus-mediated delivery entails the inherent risk of altering cancer gene expression by the genomically integrated CRISPR/Cas9. This is avoided by delivery of CRISPR/Cas9 as ribonucleoproteins, which, however, are fragile and technically demanding to produce. Electroporation of CRISPR/Cas9 expression plasmids would bypass the above issues, as this approach is simple, the reagents are robust and easily produced and delivery is transient.

Results

Here, we tested knockout of either TCR or CD52 in human primary T cells, using electroporation of CRISPR/Cas9 plasmids. After validating the CRISPR/Cas9 constructs in human 293 T cells by Tracking of Indels by Decomposition (TIDE) and Indel Detection by Amplicon Analysis (IDAA) on-target genomic analysis, we evaluated their efficacy in primary T cells. Four days after electroporation with the constructs, genomic analysis revealed a knockout rate of 12–14% for the two genes, which translated into 7–8% of cells showing complete loss of surface expression of TCR and CD52 proteins, as determined by flow cytometry analysis.

Conclusion

Our results demonstrate that genomic knockout by electroporation of plasmids encoding CRISPR/Cas9 is technically feasible in human primary T cells, albeit at low efficiency.

HLA Class I Knockout Converts Allogeneic Primary NK Cells Into Suitable Effectors for "Off-the-Shelf" Immunotherapy

Cellular immunotherapy using chimeric antigen receptors (CARs) so far has almost exclusively used autologous peripheral blood-derived T cells as immune effector cells. However, harvesting sufficient numbers of T cells is often challenging in heavily pre-treated patients with malignancies and perturbed hematopoiesis and perturbed hematopoiesis. Also, such a CAR product will always be specific for the individual patient. In contrast, NK cell infusions can be performed in non-HLA-matched settings due to the absence of alloreactivity of these innate immune cells. Still, the infused NK cells are subject to recognition and rejection by the patient's immune system, thereby limiting their life-span in vivo and undermining the possibility for multiple infusions. Here, we designed genome editing and advanced lentiviral transduction protocols to render primary human NK cells unsusceptible/resistant to an allogeneic response by the recipient's CD8+ T cells. After knocking-out surface expression of HLA class I molecules by targeting the B2M gene via CRISPR/Cas9, we also co-expressed a single-chain HLA-E molecule, thereby preventing NK cell fratricide of B2M-knockout (KO) cells via "missing self"-induced lysis. Importantly, these genetically engineered NK cells were functionally indistinguishable from their unmodified counterparts with regard to their phenotype and their natural cytotoxicity towards different AML cell lines. In co-culture assays, B2M-KO NK cells neither induced immune responses of allogeneic T cells nor re-activated allogeneic T cells which had been expanded/primed using irradiated PBMNCs of the respective NK cell donor. Our study demonstrates the feasibility of genome editing in primary allogeneic NK cells to diminish their recognition and killing by mismatched T cells and is an important prerequisite for using non-HLA-matched primary human NK cells as readily available, "off-the-shelf" immune effectors for a variety of immunotherapy indications in human cancer.

Establishment of a cell processing laboratory to support hematopoietic stem cell transplantation and chimeric antigen receptor (CAR)-T cell therapy

Cell processing laboratories are an important part of cancer treatment centers. Cell processing laboratories began by supporting hematopoietic stem cell (HSC) transplantation programs. These laboratories adapted closed bag systems, centrifuges, sterile connecting devices and other equipment used in transfusion services/blood banks to remove red blood cells and plasma from marrow and peripheral blood stem cells products. The success of cellular cancer immunotherapies such as Chimeric Antigen Receptor (CAR) T-cells has increased the importance of cell processing laboratories. Since many of the diseases successfully treated by CAR T-cell therapy are also treated by HSC transplantation and since HSC transplantation teams are well suited to manage patients treated with CAR T-cells, many cell processing laboratories have begun to produce CAR T-cells. The methods that have been used to process HSCs have been modified for T-cell enrichment, culture, stimulation, transduction and expansion for CAR T-cell production. While processing laboratories are well suited to manufacture CAR T-cells and other cellular therapies, producing these therapies is challenging. The manufacture of cellular therapies requires specialized facilities which are costly to build and maintain. The supplies and reagents, especially vectors, can also be expensive. Finally, highly skilled staff are required. The use of automated equipment for cell production may reduce labor requirements and the cost of facilities. The steps used to produce CAR T-cells are reviewed, as well as various strategies for establishing a laboratory to manufacture these cells.

Allogeneic CAR Cell Therapy-More Than a Pipe Dream

Adoptive cellular immunotherapy using immune cells expressing chimeric antigen receptors (CARs) has shown promise, particularly for the treatment of hematological malignancies. To date, the majority of clinically evaluated CAR cell products have been derived from autologous immune cells. While this strategy can be effective it also imposes several constraints regarding logistics. This includes i) availability of center to perform leukapheresis, ii) necessity for shipment to and from processing centers, and iii) time requirements for product manufacture and clinical release testing. In addition, previous cytotoxic therapies can negatively impact the effector function of autologous immune cells, which may then affect efficacy and/or durability of resultant CAR products. The use of allogeneic CAR cell products generated using cells from healthy donors has the potential to overcome many of these limitations, including through generation of “off the shelf” products. However, allogeneic CAR cell products come with their own challenges, including potential to induce graft-versus-host-disease, as well as risk of immune-mediated rejection by the host. Here we will review promises and challenges of allogeneic CAR immunotherapies, including those being investigated in preclinical models and/or early phase clinical studies.

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.

Automated generation of gene-edited CAR T cells at clinical scale

The potential of adoptive cell therapy can be extended when combined with genome editing. However, variation in the quality of the starting material and the different manufacturing steps are associated with production failure and product contamination. Here, we present an automated T cell engineering process to produce off-the-shelf chimeric antigen receptor (CAR) T cells on an extended CliniMACS Prodigy platform containing an in-line electroporation unit. This setup was used to combine lentiviral delivery of a CD19-targeting CAR with transfer of mRNA encoding a TRAC locus-targeting transcription activator-like effector nuclease (TALEN). In three runs at clinical scale, the T cell receptor (TCR) alpha chain encoding TRAC locus was disrupted in >35% of cells with high cell viability (>90%) and no detectable off-target activity. A final negative selection step allowed the generation of TCRα/β-free CAR T cells with >99.5% purity. These CAR T cells proliferated well, maintained a T cell memory phenotype, eliminated CD19-positive tumor cells, and released the expected cytokines when exposed to B cell leukemia cells. In conclusion, we established an automated, good manufacturing practice (GMP)-compliant process that integrates lentiviral transduction with electroporation of TALEN mRNA to produce functional TCRα/β-free CAR19 T cells at clinical scale.

Why Immunotherapy Fails in Multiple Myeloma

Multiple myeloma remains an incurable disease despite great advances in its therapeutic landscape. Increasing evidence supports the belief that immune dysfunction plays an important role in the disease pathogenesis, progression, and drug resistance. Recent efforts have focused on harnessing the immune system to exert anti-myeloma effects with encouraging outcomes. First-in-class anti-CD38 monoclonal antibody, daratumumab, now forms part of standard treatment regimens in relapsed and refractory settings and is shifting to front-line treatments. However, a non-negligible number of patients will progress and be triple refractory from the first line of treatment. Antibody-drug conjugates, bispecific antibodies, and chimeric antigen receptors (CAR) are being developed in a heavily pretreated setting with outstanding results. Belantamab mafodotin-blmf has already received approval and other anti-B-cell maturation antigen (BCMA) therapies (CARs and bispecific antibodies are expected to be integrated in therapeutic options against myeloma soon. Nonetheless, immunotherapy faces different challenges in terms of efficacy and safety, and manufacturing and economic drawbacks associated with such a line of therapy pose additional obstacles to broadening its use. In this review, we described the most important clinical data on immunotherapeutic agents, delineated the limitations that lie in immunotherapy, and provided potential insights to overcome such issues.

Overcoming key challenges in cancer immunotherapy with engineered T cells

PURPOSE OF REVIEW

A number of clinical trials are currently testing chimeric antigen receptor (CAR) and T cell receptor (TCR) engineered T cells for the treatment of haematologic malignancies and selected solid tumours, and CD19-CAR-T cells have produced impressive clinical responses in B-cell malignancies. Here, we summarize the current state of the field, highlighting the key aspects required for the optimal application of CAR and TCR-engineered T cells for cancer immunotherapy.

RECENT FINDINGS

Toxicities, treatment failure and disease recurrence have been observed at different rates and kinetics. Several strategies have been designed to overcome these hurdles: the identification and combination of known and new antigens, together with the combination of immunotherapeutic and classical approaches may overcome cancer immune evasion. New protocols for genetic modification and T cell culture may improve the overall fitness of cellular products and their resistance to hostile tumour immunomodulatory signals. Finally, the schedules of T cell administration and toxicity management have been adapted to improve the safety of this transformative therapeutic approach.

SUMMARY

In order to develop effective adoptive T cell treatments for cancer, therapeutic optimization of engineered CAR and TCR T cells is crucial, by simultaneously focusing on intrinsic and extrinsic factors. This review focuses on the innovative approaches designed and tested to overcome the hurdles encountered so far in the clinical practice, with new excitement on novel laboratory insights and ongoing clinical investigations.

Genome-edited, donor-derived allogeneic anti-CD19 chimeric antigen receptor T cells in paediatric and adult B-cell acute lymphoblastic leukaemia: results of two phase 1 studies

BACKGROUND

Genome-edited donor-derived allogeneic anti-CD19 chimeric antigen receptor (CAR) T cells offer a novel form of CAR-T-cell product that is available for immediate clinical use, thereby broadening access and applicability. UCART19 is one such product investigated in children and adults with relapsed or refractory B-cell acute lymphoblastic leukaemia. Two multicentre phase 1 studies aimed to investigate the feasibility, safety, and antileukaemic activity of UCART19 in children and adults with relapsed or refractory B-cell acute lymphoblastic leukaemia.

METHODS

We enrolled paediatric or adult patients in two ongoing, multicentre, phase 1 clinical trials to evaluate the safety and antileukaemic activity of UCART19. All patients underwent lymphodepletion with fludarabine and cyclophosphamide with or without alemtuzumab, then children received UCART19 at 1·1-2·3 × 106 cells per kg and adults received UCART19 doses of 6 × 106 cells, 6-8 × 107 cells, or 1·8-2·4 × 108 cells in a dose-escalation study. The primary outcome measure was adverse events in the period between first infusion and data cutoff. These studies were registered at ClinicalTrials.gov, NCT02808442 and NCT02746952.

FINDINGS

Between June 3, 2016, and Oct 23, 2018, seven children and 14 adults were enrolled in the two studies and received UCART19. Cytokine release syndrome was the most common adverse event and was observed in 19 patients (91%); three (14%) had grade 3-4 cytokine release syndrome. Other adverse events were grade 1 or 2 neurotoxicity in eight patients (38%), grade 1 acute skin graft-versus-host disease in two patients (10%), and grade 4 prolonged cytopenia in six patients (32%). Two treatment-related deaths occurred; one caused by neutropenic sepsis in a patient with concurrent cytokine release syndrome and one from pulmonary haemorrhage in a patient with persistent cytopenia. 14 (67%) of 21 patients had a complete response or complete response with incomplete haematological recovery 28 days after infusion. Patients not receiving alemtuzumab (n=4) showed no UCART19 expansion or antileukaemic activity. The median duration of response was 4·1 months with ten (71%) of 14 responders proceeding to a subsequent allogeneic stem-cell transplant. Progression-free survival at 6 months was 27%, and overall survival was 55%.

INTERPRETATION

These two studies show, for the first time, the feasibility of using allogeneic, genome-edited CAR T cells to treat patients with aggressive leukaemia. UCART19 exhibited in-vivo expansion and antileukaemic activity with a manageable safety profile in heavily pretreated paediatric and adult patients with relapsed or refractory B-cell acute lymphoblastic leukaemia. The results this study are an encouraging step forward for the field of allogeneic CAR T cells, and UCART19 offers the opportunity to treat patients with rapidly progressive disease and where autologous CAR-T-cell therapy is unavailable.

FUNDING

Servier.

CRISPR-Mediated Base Conversion Allows Discriminatory Depletion of Endogenous T Cell Receptors for Enhanced Synthetic Immunity

Emerging base editing technology exploits CRISPR RNA-guided DNA modification effects for highly specific C > T conversion, which has been used to efficiently disrupt gene expression. These tools can enhance synthetic T cell immunity by restricting specificity, addressing histocompatibility leukocyte antigen (HLA) barriers, and promoting persistence. We report lentiviral delivery of a hepatitis B-virus (HBV)-specific recombinant T cell receptor (rTCR) and a linked CRISPR single-guide RNA for simultaneous disruption of endogenous TCRs (eTCRs) when combined with transient cytosine deamination. Discriminatory depletion of eTCR and coupled expression of rTCR resulted in enrichment of HBV-specific populations from 55% (SEM, ±2.4%) to 95% (SEM, ±0.5%). Intensity of rTCR expression increased 1.8- to 2.9-fold compared to that in cells retaining their competing eTCR, and increased cytokine production and killing of HBV antigen-expressing hepatoma cells in a 3D microfluidic model were exhibited. Molecular signatures confirmed that seamless conversion of C > T (G > A) had created a premature stop codon in TCR beta constant 1/2 loci, with no notable activity at predicted off-target sites. Thus, targeted disruption of eTCR by cytosine deamination and discriminatory enrichment of antigen-specific T cells offers the prospect of enhanced, more specific T cell therapies against HBV-associated hepatocellular carcinoma (HCC) as well as other viral and tumor antigens.

Paving the Way Towards Universal Chimeric Antigen Receptor Therapy in Cancer Treatment: Current Landscape and Progress

Chimeric antigen receptor (CAR) therapy has been proved effective in a stream of clinical trials, especially in hematologic malignancies. However, current CAR therapy is highly personalized as cells used are derived from patients themselves, which can be costly, time-consuming, and sometimes fails to achieve optimal therapeutic results due to poor quality/quantity of patient-derived cells. On the contrary, universal CAR therapy, which is based on healthy individuals’ cells, circumvents several limitations of current autologous CAR therapy. To achieve the universality of CAR therapy, the allogeneic cell transplantation related issues, such as graft-versus-host disease (GVHD) and host-versus-graft activities (HVGA), must be addressed. In this review, we focus on current progress regarding GVHD and HVGA in the universal CAR therapy, followed by a universal CAR design that may be applied to allogeneic cells and a summary of key clinical trials in this field. This review may provide valuable insights into the future design of universal CAR products.

Immune Modulation in Lung Cancer: Current Concepts and Future Strategies

Cancer immunotherapy represents the most dynamic field of biomedical research currently, with thoracic immuno-oncology as a forerunner. PD-(L)1 inhibitors are already part of standard first-line treatment for both non-small-cell and small-cell lung cancer, while unprecedented 5-year survival rates of 15-25% have been achieved in pretreated patients with metastatic disease. Evolving strategies are mainly aiming for improvement of T-cell function, increase of immune activation in the tumor microenvironment (TME), and supply of tumor-reactive lymphocytes. Several novel therapeutics have demonstrated preclinical efficacy and are increasingly used in rational combinations within clinical trials. Two overarching trends dominate: extension of immunotherapy to earlier disease stages, mainly as neoadjuvant treatment, and a shift of focus towards multivalent, individualized, mutatome-based antigen-specific modalities, mainly adoptive cell therapies and cancer vaccines. The former ensures ample availability of treated and untreated patient samples, the latter facilitates deeper mechanistic insights, and both in combination build an overwhelming force that is accelerating progress and driving the greatest revolution cancer medicine has seen so far. Today, immune modulation represents the most potent therapeutic modality in oncology, the most important topic in clinical and translational cancer research, and arguably our greatest, meanwhile justified hope for achieving cure of pulmonary neoplasms and other malignancies in the next future.

Practical aspects of building a new immunotherapy program: the future of cell therapy

Cellular-redirecting therapies, including bispecific T-cell engagers and chimeric antigen receptor (CAR) T cells, are rapidly changing the treatment landscape of hematologic malignancies and solid tumor malignancies. I will discuss the unique safety profile and logistical aspects that pose challenges and opportunities for the safe and successful delivery of these therapies. Close interaction, communication, and established partnerships between the primary oncologist, the disease specialist, and the immune effector cell provider will be needed to provide optimal care longitudinally for any patient. I will discuss practical ways for any program to deliver these therapies and how future advances may widen availability beyond just a few centers.

Function and evolution of the prototypic CD28ζ and 4-1BBζ chimeric antigen receptors

T cells engineered to express chimeric antigen receptors (CARs) specific for CD19 have yielded remarkable clinical outcomes in patients with refractory B-cell malignancies. The first CARs to be approved by the US Food and Drug Administration and the European Medicines Agency are CD19 CARs that comprise either CD28/CD3ζ or 4-1BB/CD3ζ dual-signalling domains. While their efficacy and safety profiles in patients with B-cell malignancies are comparable overall, the functional properties these two CAR designs impart upon engineered T cells differ significantly. Remarkably, alternative costimulatory domains have not, to date, superseded these foundational designs. Rather, recent CAR advances have focused on perfecting the original CD28- and 4-1BB-based CD19 CARs by calibrating strength of activation, pre-empting T-cell exhaustion and increasing the functional persistence of CAR T cells. This article reviews the essential biological properties of these first-in-class prototypes and their recent evolution.

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CD19 chimeric antigen receptor (CAR) therapy has shown remarkable success against B-cell malignancies.

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The prototypic CD19 CARs comprise either CD28/CD3ζ or 4-1BB/CD3ζ signalling domains.

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Both CD19 CARs yield similar efficacy but impart distinct T-cell functionalities.

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Novel CAR designs aim to enhance the persistence or effector potency of T cells.

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Genome editing averts variegated CAR expression and sustains T-cell function.

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.

CRISPR FokI Dead Cas9 System: Principles and Applications in Genome Engineering

The identification of the robust clustered regularly interspersed short palindromic repeats (CRISPR) associated endonuclease (Cas9) system gene-editing tool has opened up a wide range of potential therapeutic applications that were restricted by more complex tools, including zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs). Nevertheless, the high frequency of CRISPR system off-target activity still limits its applications, and, thus, advanced strategies for highly specific CRISPR/Cas9-mediated genome editing are continuously under development including CRISPR–FokI dead Cas9 (fdCas9). fdCas9 system is derived from linking a FokI endonuclease catalytic domain to an inactive Cas9 protein and requires a pair of guide sgRNAs that bind to the sense and antisense strands of the DNA in a protospacer adjacent motif (PAM)-out orientation, with a defined spacer sequence range around the target site. The dimerization of FokI domains generates DNA double-strand breaks, which activates the DNA repair machinery and results in genomic edit. So far, all the engineered fdCas9 variants have shown promising gene-editing activities in human cells when compared to other platforms. Herein, we review the advantages of all published variants of fdCas9 and their current applications in genome engineering.

CRISPR-Based Editing Techniques for Genetic Manipulation of Primary T Cells

While clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing techniques have been widely adapted for use in immortalised immune cells, efficient manipulation of primary T cells has proved to be more challenging. Nonetheless, the rapid expansion of the CRISPR toolbox accompanied by the development of techniques for delivery of CRISPR components into primary T cells now affords the possibility to genetically manipulate primary T cells both with precision and at scale. Here, we review the key features of the techniques for primary T cell editing and discuss how the new generation of CRISPR-based tools may advance genetic engineering of these immune cells. This improved ability to genetically manipulate primary T cells will further enhance our fundamental understanding of cellular signalling and transcriptional networks in T cells and more importantly has the potential to revolutionise T cell-based therapies.

High-throughput continuous-flow microfluidic electroporation of mRNA into primary human T cells for applications in cellular therapy manufacturing

Implementation of gene editing technologies such as CRISPR/Cas9 in the manufacture of novel cell-based therapeutics has the potential to enable highly-targeted, stable, and persistent genome modifications without the use of viral vectors. Electroporation has emerged as a preferred method for delivering gene-editing machinery to target cells, but a major challenge remaining is that most commercial electroporation machines are built for research and process development rather than for large-scale, automated cellular therapy manufacturing. Here we present a microfluidic continuous-flow electrotransfection device designed for precise, consistent, and high-throughput genetic modification of target cells in cellular therapy manufacturing applications. We optimized our device for delivery of mRNA into primary human T cells and demonstrated up to 95% transfection efficiency with minimum impact on cell viability and expansion potential. We additionally demonstrated processing of samples comprising up to 500 million T cells at a rate of 20 million cells/min. We anticipate that our device will help to streamline the production of autologous therapies requiring on the order of 10[Formula: see text]-10[Formula: see text] cells, and that it is well-suited to scale for production of trillions of cells to support emerging allogeneic therapies.

Engineering Tolerance toward Allogeneic CAR-T Cells by Regulation of MHC Surface Expression with Human Herpes Virus-8 Proteins

Allogeneic, off-the-shelf (OTS) chimeric antigen receptor (CAR) cell therapies have the potential to reduce manufacturing costs and variability while providing broader accessibility to cancer patients and those with other diseases. However, host-versus-graft reactivity can limit the durability and efficacy of OTS cell therapies requiring new strategies to evade adaptive and innate-immune responses. Human herpes virus-8 (HHV8) maintains infection, in part, by evading host T and natural killer (NK) cell attack. The viral K3 gene encodes a membrane-tethered E3 ubiquitin ligase that discretely targets major histocompatibility complex (MHC) class I components, whereas K5 encodes a similar E3 ligase with broader specificity, including MHC-II and the MHC-like MHC class I polypeptide-related sequence A (MIC-A)- and sequence B (MIC-B)-activating ligands of NK cells. We created γ-retroviruses encoding K3 and/or K5 transgenes that efficiently transduce primary human T cells. Expression of K3 or K5 resulted in dramatic downregulation of MHC-IA (human leukocyte antigen [HLA]-A, -B, and -C) and MHC class II (HLA-DR) cell-surface expression. K3 expression was sufficient for T cells to resist exogenously loaded peptide-MHC-specific cytotoxicity, as well as recognition in one-way allogeneic mixed lymphocyte reactions. Further, in immunodeficient mice engrafted with allogeneic T cells, K3-transduced T cells selectively expanded in vivo. Ectopic K5 expression in MHC class I^-, MIC-A⁺/B⁺ K562 cells also reduced targeting by primary NK cells. Coexpression of K3 in prostate stem cell antigen (PSCA)-directed, inducible MyD88/CD40 (iMC)-enhanced CAR-T cells did not impact cytotoxicity, T cell growth, or cytokine production against HPAC pancreatic tumor target cells, whereas K5-expressing cells showed a modest reduction in interleukin (IL)-2 production without effect on cytotoxicity. Together, these results support application of these E3 ligases to advance development of OTS CAR-T cell products.

Abrogation of HLA surface expression using CRISPR/Cas9 genome editing: a step toward universal T cell therapy

As recent advancements in the chimeric antigen receptor-T cells have revolutionized the way blood cancers are handled, potential benefits from producing off-the-shelf, standardized immune cells entail the need for development of allogeneic immune cell therapy. However, host rejection driven by HLA disparity in adoptively transferred allogeneic T cells remains a key obstacle to the universal donor T cell therapy. To evade donor HLA-mediated immune rejection, we attempted to eliminate T cell’s HLA through the CRISPR/Cas9 gene editing system. First, we screened 60 gRNAs targeting B2M and multiple sets of gRNA each targeting α chains of HLA-II (DPA, DQA and DRA, respectively) using web-based design tools, and identified specific gRNA sequences highly efficient for target deletion without carrying off-target effects. Multiplex genome editing of primary human T cells achieved by the newly discovered gRNAs yielded HLA-I- or HLA-I/II-deficient T cells that were phenotypically unaltered and functionally intact. The overnight mixed lymphocyte reactions demonstrated the HLA-I-negative cells induced decreased production of IFN-γ and TNF-α in alloreactive T cells, and deficiency of HLA-I/II in T cells further dampened the inflammatory responses. Taken together, our approach will provide an efficacious pathway toward the universal donor cell generation by manipulating HLA expression in therapeutic T cells.