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

Time to evolve: predicting engineered T cell-associated toxicity with next-generation models

Despite promising clinical results in a small subset of malignancies, therapies based on engineered chimeric antigen receptor and T-cell receptor T cells are associated with serious adverse events, including cytokine release syndrome and neurotoxicity. These toxicities are sometimes so severe that they significantly hinder the implementation of this therapeutic strategy. For a long time, existing preclinical models failed to predict severe toxicities seen in human clinical trials after engineered T-cell infusion. However, in recent years, there has been a concerted effort to develop models, including humanized mouse models, which can better recapitulate toxicities observed in patients. The Accelerating Development and Improving Access to CAR and TCR-engineered T cell therapy (T2EVOLVE) consortium is a public–private partnership directed at accelerating the preclinical development and increasing access to engineered T-cell therapy for patients with cancer. A key ambition in T2EVOLVE is to design new models and tools with higher predictive value for clinical safety and efficacy, in order to improve and accelerate the selection of lead T-cell products for clinical translation. Herein, we review existing preclinical models that are used to test the safety of engineered T cells. We will also highlight limitations of these models and propose potential measures to improve them.

Allogeneic TCRαβ deficient CAR T-cells targeting CD123 in acute myeloid leukemia

Acute myeloid leukemia (AML) is a disease with high incidence of relapse that is originated and maintained from leukemia stem cells (LSCs). Hematopoietic stem cells can be distinguished from LSCs by an array of cell surface antigens such as CD123, thus a candidate to eliminate LSCs using a variety of approaches, including CAR T cells. Here, we evaluate the potential of allogeneic gene-edited CAR T cells targeting CD123 to eliminate LSCs (UCART123). UCART123 cells are TCRαβneg T cells generated from healthy donors using TALEN® gene-editing technology, decreasing the likelihood of graft vs host disease. As safety feature, cells express RQR8 to allow elimination with Rituximab. UCART123 effectively eliminates AML cells in vitro and in vivo with significant benefits in overall survival of AML-patient derived xenograft mice. Furthermore, UCART123 preferentially target AML over normal cells with modest toxicity to normal hematopoietic stem/progenitor cells. Together these results suggest that UCART123 represents an off-the shelf therapeutic approach for AML.

CD123, the interleukin-3 receptor alpha chain, is aberrantly expressed in acute myeloid leukemia blasts and leukemia stem cells. Here the authors report the design and characterize the anti-tumor activity of allogeneic CD123-targeted CAR-T cells as a therapeutic approach for acute myeloid leukemia.

Targeting CD123 in blastic plasmacytoid dendritic cell neoplasm using allogeneic anti-CD123 CAR T cells

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with poor outcomes with conventional therapy. Nearly 100% of BPDCNs overexpress interleukin 3 receptor subunit alpha (CD123). Given that CD123 is differentially expressed on the surface of BPDCN cells, it has emerged as an attractive therapeutic target. UCART123 is an investigational product consisting of allogeneic T cells expressing an anti-CD123 chimeric antigen receptor (CAR), edited with TALEN^® nucleases. In this study, we examine the antitumor activity of UCART123 in preclinical models of BPDCN. We report that UCART123 have selective antitumor activity against CD123-positive primary BPDCN samples (while sparing normal hematopoietic progenitor cells) in the in vitro cytotoxicity and T cell degranulation assays; supported by the increased secretion of IFNγ by UCART123 cells when cultured in the presence of BPDCN cells. UCART123 eradicate BPDCN and result in long-term disease-free survival in a subset of primary patient-derived BPDCN xenograft mouse models. One potential challenge of CD123 targeting therapies is the loss of CD123 antigen through diverse genetic mechanisms, an event observed in one of three BPDCN PDX studied. In summary, these results provide a preclinical proof-of-principle that allogeneic UCART123 cells have potent anti-BPDCN activity.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematologic malignancy derived from the precursors of plasmacytoid dendritic cells. Here the authors characterize the anti-tumor activity of allogeneic anti-CD123 CAR-T cells in preclinical models of BPDCN.

Development of CAR T Cell Therapy in Children-A Comprehensive Overview

CAR T cell therapy has revolutionized immunotherapy in the last decade with the successful establishment of chimeric antigen receptor (CAR)-expressing cellular therapies as an alternative treatment in relapsed and refractory CD19-positive leukemias and lymphomas. There are fundamental reasons why CAR T cell therapy has been approved by the Food and Drug administration and the European Medicines Agency for pediatric and young adult patients first. Commonly, novel therapies are developed for adult patients and then adapted for pediatric use, due to regulatory and commercial reasons. Both strategic and biological factors have supported the success of CAR T cell therapy in children. Since there is an urgent need for more potent and specific therapies in childhood malignancies, efforts should also include the development of CAR therapeutics and expand applicability by introducing new technologies. Basic aspects, the evolution and the drawbacks of childhood CAR T cell therapy are discussed as along with the latest clinically relevant information.

Reprogramming the tumor microenvironment by genome editing for precision cancer therapy

The tumor microenvironment (TME) is essential for immune escape by tumor cells. It plays essential roles in tumor development and metastasis. The clinical outcomes of tumors are often closely related to individual differences in the patient TME. Therefore, reprogramming TME cells and their intercellular communication is an attractive and promising strategy for cancer therapy. TME cells consist of immune and nonimmune cells. These cells need to be manipulated precisely and safely to improve cancer therapy. Furthermore, it is encouraging that this field has rapidly developed in recent years with the advent and development of gene editing technologies. In this review, we briefly introduce gene editing technologies and systematically summarize their applications in the TME for precision cancer therapy, including the reprogramming of TME cells and their intercellular communication. TME cell reprogramming can regulate cell differentiation, proliferation, and function. Moreover, reprogramming the intercellular communication of TME cells can optimize immune infiltration and the specific recognition of tumor cells by immune cells. Thus, gene editing will pave the way for further breakthroughs in precision cancer therapy.

Pharmacotherapeutic Treatment of Glioblastoma: Where Are We to Date?

The clinical management of glioblastoma (GBM) is still bereft of treatments able to significantly improve the poor prognosis of the disease. Despite the extreme clinical need for novel therapeutic drugs, only a small percentage of patients with GBM benefit from inclusion in a clinical trial. Moreover, often clinical studies do not lead to final interpretable conclusions. From the mistakes and negative results obtained in the last years, we are now able to plan a novel generation of clinical studies for patients with GBM, allowing the testing of multiple anticancer agents at the same time. This assumes critical importance, considering that, thanks to improved knowledge of altered molecular mechanisms related to the disease, we are now able to propose several potential effective compounds in patients with both newly diagnosed and recurrent GBM. Among the novel compounds assessed, the initially great enthusiasm toward trials employing immune checkpoint inhibitors (ICIs) was disappointing due to the negative results that emerged in three randomized phase III trials. However, novel biological insights into the disease suggest that immunotherapy can be a convincing and effective treatment in GBM even if ICIs failed to prolong the survival of these patients. In this regard, the most promising approach consists of engineered immune cells such as chimeric antigen receptor (CAR) T, CAR M, and CAR NK alone or in combination with other treatments. In this review, we discuss several issues related to systemic treatments in GBM patients. First, we assess critical issues toward the planning of clinical trials and the strategies employed to overcome these obstacles. We then move on to the most relevant interventional studies carried out on patients with previously untreated (newly diagnosed) GBM and those with recurrent and pretreated disease. Finally, we investigate novel immunotherapeutic approaches with special emphasis on preclinical and clinical data related to the administration of engineered immune cells in GBM.

Hurdles to breakthrough in CAR T cell therapy of solid tumors

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

Immunotherapy and CRISPR Cas Systems: Potential Cure of COVID-19?

The COVID-19 has plunged the world into a pandemic that affected millions. The continually emerging new variants of concern raise the question as to whether the existing vaccines will continue to provide sufficient protection for individuals from SARS-CoV-2 during natural infection. This narrative review aims to briefly outline various immunotherapeutic options and discuss the potential of clustered regularly interspaced short palindromic repeat (CRISPR Cas system technology against COVID-19 treatment as specific cure. As the development of vaccine, convalescent plasma, neutralizing antibodies are based on the understanding of human immune responses against SARS-CoV-2, boosting human body immune responses in case of SARS-CoV-2 infection, immunotherapeutics seem feasible as specific cure against COVID-19 if the present challenges are overcome. In cell based therapeutics, apart from the high costs, risks and side effects, there are technical problems such as the production of sufficient potent immune cells and antibodies under limited time to treat the COVID-19 patients in mild conditions prior to progression into a more severe case. The CRISPR Cas technology could be utilized to refine the specificity and safety of CAR-T cells, CAR-NK cells and neutralizing antibodies against SARS-CoV-2 during various stages of the COVID-19 disease progression in infected individuals. Moreover, CRISPR Cas technology are proposed in hypotheses to degrade the viral RNA in order to terminate the infection caused by SARS-CoV-2. Thus personalized cocktails of immunotherapeutics and CRISPR Cas systems against COVID-19 as a strategy might prevent further disease progression and circumvent immunity escape.

Recent Advances in CAR T-Cell Therapy for Patients with Chronic Lymphocytic Leukemia

Chimeric antigen receptor T cells (CAR T cells) have resulted in dramatic treatment responses for patients with hematologic malignancies, resulting in improved survival for patients with intractable disease. The first patient treated with CD19 directed CAR T cell therapy had chronic lymphocytic leukemia (CLL) and achieved a complete remission. Subsequent clinical trials have focused largely on patients with other B-cell hematologic malignancies, owing to the fact that CAR T cell therapy for patients with CLL has met with challenges. More recent clinical trials have demonstrated CAR T cell therapy can be well tolerated and effective for patients with CLL, making it a potential treatment option for patients with this disease. In this article we review the background on CAR T cells for the treatment of patients with CLL, focusing on the unique obstacles that patients with CLL present for the development of adoptive T cell therapy, and the novel approaches currently under development to overcome these hurdles.

Emerging Novel Combined CAR-T Cell Therapies

Simple Summary

As a result of FDA approval of CAR-T cell treatments in the last few years, this immunotherapy has provided further direction to precision medicine through its combination with other therapeutic approaches. In the past year, several review articles have been published focusing on advances in this fast-developing field, especially with respect to efforts to overcome hurdles associated with applying CAR-T cells in solid tumors. This review paper focuses on combining CAR-T cell therapy with small molecule drugs, up-to-date progress in CAR-T cell therapy research, and advances in combined CAR-T immunotherapy with other treatments targeting solid tumors.

Abstract

Chimeric antigen receptors (CAR) T cells are T cells engineered to express membrane receptors with high specificity to recognize specific target antigens presented by cancer cells and are co-stimulated with intracellular signals to increase the T cell response. CAR-T cell therapy is emerging as a novel therapeutic approach to improve T cell specificity that will lead to advances in precision medicine. CAR-T cells have had impressive outcomes in hematological malignancies. However, there continue to be significant limitations of these therapeutic responses in targeting solid malignancies such as heterogeneous antigens in solid tumors, tumor immunosuppressive microenvironment, risk of on-target/off-tumor, infiltrating CAR-T cells, immunosuppressive checkpoint molecules, and cytokines. This review paper summarizes recent approaches and innovations through combination therapies of CAR-T cells and other immunotherapy or small molecule drugs to counter the above disadvantages to potentiate the activity of CAR-T cells.

3D-organoid culture supports differentiation of human CAR+ iPSCs into highly functional CAR T cells

Unlimited generation of chimeric antigen receptor (CAR) T cells from human-induced pluripotent stem cells (iPSCs) is an attractive approach for "off-the-shelf" CAR T cell immunotherapy. Approaches to efficiently differentiate iPSCs into canonical αβ T cell lineages, while maintaining CAR expression and functionality, however, have been challenging. We report that iPSCs reprogramed from CD62L⁺ naive and memory T cells followed by CD19-CAR engineering and 3D-organoid system differentiation confers products with conventional CD8αβ-positive CAR T cell characteristics. Expanded iPSC CD19-CAR T cells showed comparable antigen-specific activation, degranulation, cytotoxicity, and cytokine secretion compared with conventional CD19-CAR T cells and maintained homogeneous expression of the TCR derived from the initial clone. iPSC CD19-CAR T cells also mediated potent antitumor activity in vivo, prolonging survival of mice with CD19⁺ human tumor xenografts. Our study establishes feasible methodologies to generate highly functional CAR T cells from iPSCs to support the development of "off-the-shelf" manufacturing strategies.

Engineering CAR T cells for enhanced efficacy and safety

Despite its success in treating hematologic malignancies, chimeric antigen receptor (CAR) T cell therapy faces two major challenges which hinder its broader applications: the limited effectiveness against solid tumors and the nonspecific toxicities. To address these concerns, researchers have used synthetic biology approaches to develop optimization strategies. In this review, we discuss recent improvements on the CAR and other non-CAR molecules aimed to enhance CAR T cell efficacy and safety. We also highlight the development of different types of inducible CAR T cells that can be controlled by environmental cues and/or external stimuli. These advancements are bringing CAR T therapy one step closer to safer and wider applications, especially for solid tumors.

CD3 engagement as a new strategy for allogeneic “off-the-shelf” T cell therapy

Allogeneic “off-the-shelf” (OTS) chimeric antigen receptor T cells (CAR-T cells) hold promise for more accessible CAR-T therapy. Here, we report a novel and simple way to make allogeneic OTS T cells targeting cancer. By engineering T cells with a bispecific T cell engager (BiTE), both TCRαβ and CD3ε expression on the T cell surface are dramatically reduced. BiTE-engineered T (BiTE-T) cells show reduced reaction to TCR stimulation in vitro and have low risk of graft-versus-host disease (GvHD) in vivo. BiTE-T cells down-regulated CD3ε/TCRαβ on bystander T cells by releasing BiTEs. BiTE-T cells produce much fewer cytokines and are comparable to CAR-T cells on anti-cancer efficacy in xenograft mouse models with pre-existing HLA-mismatched T cells. Co-expressing co-stimulatory factors or T cell-promoting cytokines enhanced BiTE-T cells. Our study suggests CD3ε engagement could be a new strategy for allogeneic T cell therapy worthy of further evaluation.

Allogeneic Chimeric Antigen Receptor Therapy in Lymphoma

The therapeutic armamentarium has significantly expanded since the approval of various CD19-targeting chimeric antigen receptor T cell (CAR-T) therapies in non-Hodgkin lymphoma (NHL). These CAR-Ts are patient-specific and require a complex, resource, and time-consuming process. While this appears promising, autologous CAR-Ts are limited due to the lack of accessibility, manufacturing delays, and variable product quality. To overcome these, allogeneic (allo) CARs from healthy donors appear appealing. These can be immediately available as “off the shelf” ready-to-use products of standardized and superior quality exempt from the effects of an immunosuppressive tumor microenvironment and prior treatments, and potentially with lower healthcare utilization using industrialized scale production. Allogeneic CARs, however, are not devoid of complications and require genomic editing, especially with αβ T cells to avoid graft versus host disease (GvHD) and allo-rejection by the recipient’s immune system. Tools for genomic editing such as TALEN and CRISPR provide promise to develop truly “off the shelf” universal CARs and further advance the field of cellular immunotherapy. Several allogeneic CARs are currently in early phase clinical trials, and preliminary data is encouraging. Longer follow-up is required to truly assess the feasibility and safety of these techniques in the patients. This review focuses on the strategies for developing allogeneic CARs along with cell sources and clinical experience thus far in lymphoma.

Chimeric antigen receptor T cell therapy: challenges and opportunities in lung cancer

Chimeric antigen receptor (CAR) T-cell therapy has revolutionized the paradigm in hematological malignancies treatment, driving an ever-expanding number of basic research and clinical trials of genetically engineering T cells to treat solid tumors. CAR T-cell therapies based on the antibodies targeting Mesothelin, CEA, EGFR, EGFR, MUC1, DLL3, and emerging novel targets provide promising efficacy for lung cancer patients. However, clinical application of CAR T-cell therapy against lung cancer remains limited on account of physical and immune barriers, antigen escape and heterogeneity, on-target off-tumor toxicity, and many other reasons. Understanding the evolution of CAR structure and the generalizable requirements for manufacturing CAR T cells as well as the interplay between lung tumor immunology and CAR T cells will improve clinical translation of this therapeutic modality in lung cancer. In this review, we systematically summarize the latest advances in CAR T-cell therapy in lung cancer, focusing on the CAR structure, target antigens, challenges, and corresponding new strategies.

Challenges of CAR T-cell Therapy in CLL: Lessons Learned

Development of chimeric antigen receptor T (CART) cell therapy has led to unprecedented success against B cell leukemia and lymphoma and resulted in FDA-approved treatment protocols. Despite the initial clinical response in B cell-related malignancies, high relapse rates suggest that much work is needed to uncover mechanisms of resistance. In chronic lymphocytic leukemia (CLL), the durable activity of CAR T-cells is limited, and CART cell success is lower than in other malignancies. T cells from these patients are vulnerable to a state of dysfunction due to stresses including chronic infection, rapid cell cycle upon antigen recognition, immunosuppressive tumor microenvironment, and cancer-related treatments. T cells are also introduced to additional stresses when cultured ex vivo during the CART manufacturing process. All these factors contribute to the limited regenerative capacity of T cells, which can lead to CART treatment failure. In this short report, we will review the challenges of CAR T-cell therapy in patients with CLL and discuss potential strategies to overcome these challenges.

Strategies to Circumvent the Side-Effects of Immunotherapy Using Allogeneic CAR-T Cells and Boost Its Efficacy: Results of Recent Clinical Trials

Despite the outstanding results of treatment using autologous chimeric antigen receptor T cells (CAR-T cells) in hematological malignancies, this approach is endowed with several constraints. In particular, profound lymphopenia in some patients and the inability to manufacture products with predefined properties or set of cryopreserved batches of cells directed to different antigens in advance. Allogeneic CAR-T cells have the potential to address these issues but they can cause life-threatening graft-versus-host disease or have shorter persistence due to elimination by the host immune system. Novel strategies to create an “off the shelf” allogeneic product that would circumvent these limitations are an extensive area of research. Here we review CAR-T cell products pioneering an allogeneic approach in clinical trials.

The Application of CRISPR/Cas9 Technology for Cancer Immunotherapy: Current Status and Problems

Cancer is one of the main causes of disease-related deaths in the world. Although cancer treatment strategies have been improved in recent years, the survival time of cancer patients is still far from satisfied. Cancer immunotherapy, such as Oncolytic virotherapy, Immune checkpoints inhibition, Chimeric antigen receptor T (CAR-T) cell therapy, Chimeric antigen receptor natural killer (CAR-NK) cell therapy and macrophages genomic modification, has emerged as an effective therapeutic strategy for different kinds of cancer. However, many patients do not respond to the cancer immunotherapy which warrants further investigation to optimize this strategy. The clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR/Cas9), as a versatile genome engineering tool, has become popular in the biology research field and it was also applied to optimize tumor immunotherapy. Moreover, CRISPR-based high-throughput screening can be used in the study of immunomodulatory drug resistance mechanism. In this review, we summarized the development as well as the application of CRISPR/Cas9 technology in the cancer immunotherapy and discussed the potential problems that may be caused by this combination.

New Indications and platforms for CAR-T therapy in lymphomas beyond DLBCL

CD19 directed chimeric antigen receptor T-cell therapy (CAR-T) represents a significant advancement for patients with relapsed/refractory large B-cell lymphoma (LBCL). Long term follow-up confirms durable remissions in nearly half of the patients, a population which was previously estimated to have a median survival of around 6 months with standard salvage therapy. This initial success of CAR-T has led to significant expansion across other lymphoma histologies resulting in the recent regulatory approval of CAR-T in mantle cell lymphoma and follicular lymphoma. Additionally, multiple novel platforms of CAR-T therapy are under development to improve efficacy and limit toxicity such dual antigen targeting, allogeneic and natural killer CAR's. In this review, we focus on the new indications of CAR-T in lymphomas beyond LBCL as well as emerging platforms of CAR-T therapy.

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

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

The Potential Applications of Stem Cells for Cancer Treatment

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Scientists encounter many obstacles in traditional cancer therapies, including the side effects on the healthy cells, drug resistance, tumor relapse, the short half-life of employed drugs in the blood circulation, and the improper delivery of drugs toward the tumor site. The unique traits of stem cells (SCs) such as self-renewal, differentiation, tumor tropism, the release of bioactive molecules, and immunosuppression have opened a new window for utilizing SCs as a novel tool in cancer treatment. In this regard, engineered SCs can secrete anti-cancer proteins or express enzymes used in suicide gene therapy which locally induce apoptosis in neoplastic cells via the bystander effect. These cells also stand as proper candidates to serve as careers for drug-loaded nanoparticles or to play suitable hosts for oncolytic viruses. Moreover, they harbor great potential to be employed in immunotherapy and combination therapy. However, tactful strategies should be devised to allow easier transplantation and protection of SCs from in vivo immune responses. In spite of the great hope concerning SCs application in cancer therapy, there are shortcomings and challenges to be addressed. This review tends to elaborate on recent advances on the various applications of SCs in cancer therapy and existing challenges in this regard.

[Development of allogeneic CAR T-cells]

Chimeric antigen receptor (CAR) T-cell therapy represents a major breakthrough in the field of hematology. "Off-the-shelf" allogeneic CAR T-cells from donors have many potential advantages over autologous approaches, such as the immediate availability of cryopreserved batches, possible standardization of the cell product, time for multiple cell modifications, redosing and decreased cost. However, allogeneic T-cells possess foreign immunological identities that can lead to graft-versus-host disease (GvHD) and their rejection by the host immune system. In this review, we describe the different approaches to produce allogeneic CAR T-cells with limited potential for GvHD and that can persist in the recipient. The preliminary clinical results obtained with the first generation of allogeneic CAR T-cells are presented as well as the perspectives in hematological malignancies and solid tumors.

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

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

Multiplex CRISPR/Cas9 genome editing in hematopoietic stem cells for fetal hemoglobin reinduction generates chromosomal translocations

Sickle cell disease and β-thalassemia are common monogenic disorders that cause significant morbidity and mortality globally. The only curative treatment currently is allogeneic hematopoietic stem cell transplantation, which is unavailable to many patients due to a lack of matched donors and carries risks including graft-versus-host disease. Genome editing therapies targeting either the BCL11A erythroid enhancer or the HBG promoter are already demonstrating success in reinducing fetal hemoglobin. However, where a single locus is targeted, reliably achieving levels high enough to deliver an effective cure remains a challenge. We investigated the application of a CRISPR/Cas9 multiplex genome editing approach, in which both the BCL11A erythroid enhancer and HBG promoter are disrupted within human hematopoietic stem cells. We demonstrate superior fetal hemoglobin reinduction with this dual-editing approach without compromising engraftment or lineage differentiation potential of edited cells post-xenotransplantation. However, multiplex editing consistently resulted in the generation of chromosomal rearrangement events that persisted in vivo following transplantation into immunodeficient mice. The risk of oncogenic events resulting from such translocations therefore currently prohibits its clinical translation, but it is anticipated that, in the future, alternative editing platforms will help alleviate this risk.

Clustered regularly interspaced short palindromic repeats, a glimpse - impacts in molecular biology, trends and highlights

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) is a novel molecular tool. In recent days, it has been highlighted a lot, as the Nobel prize was awarded for this sector in 2020, and also for its recent use in Covid-19 related diagnostics. Otherwise, it is an eminent gene-editing technique applied in diverse medical zones of therapeutics in genetic diseases, hematological diseases, infectious diseases, etc., research related to molecular biology, cancer, hereditary diseases, immune and inflammatory diseases, etc., diagnostics related to infectious diseases like viral hemorrhagic fevers, Covid-19, etc. In this review, its discovery, working mechanisms, challenges while handling the technique, recent advancements, applications, alternatives have been discussed. It is a cheaper, faster technique revolutionizing the medicinal field right now. However, their off-target effects and difficulties in delivery into the desired cells make CRISPR, not easily utilizable. We conclude that further robust research in this field may promise many interesting, useful results.

Current Limitations and Perspectives of Chimeric Antigen Receptor-T-Cells in Acute Myeloid Leukemia

Simple Summary

Acute myeloid leukemia (AML) is the most frequent type of acute leukemia in adults. Allogeneic hematopoietic cell transplantation (allo-HCT) has been the only potentially curative treatment for the majority of patients. The ability of chimeric antigen receptor (CAR)-modified T-cell therapy directed against the CD19 antigen to induce durable remissions in patients with acute lymphoblastic leukemia (ALL) has provided optimism that this novel treatment paradigm can be extrapolated to AML. In this review, we provide an overview of candidate target antigens for CAR-T-cells in AML, an update on recent progress in preclinical and clinical development of investigational CAR-T-cell products, and discuss challenges for the clinical implementation of CAR-T-cell therapy in AML.

Abstract

Adoptive transfer of gene-engineered chimeric antigen receptor (CAR)-T-cells has emerged as a powerful immunotherapy for combating hematologic cancers. Several target antigens that are prevalently expressed on AML cells have undergone evaluation in preclinical CAR-T-cell testing. Attributes of an ‘ideal’ target antigen for CAR-T-cell therapy in AML include high-level expression on leukemic blasts and leukemic stem cells (LSCs), and absence on healthy tissues, normal hematopoietic stem and progenitor cells (HSPCs). In contrast to other blood cancer types, where CAR-T therapies are being similarly studied, only a rather small number of AML patients has received CAR-T-cell treatment in clinical trials, resulting in limited clinical experience for this therapeutic approach in AML. For curative AML treatment, abrogation of bulk blasts and LSCs is mandatory with the need for hematopoietic recovery after CAR-T administration. Herein, we provide a critical review of the current pipeline of candidate target antigens and corresponding CAR-T-cell products in AML, assess challenges for clinical translation and implementation in routine clinical practice, as well as perspectives for overcoming them.

T Cell Engaging Immunotherapies, Highlighting Chimeric Antigen Receptor (CAR) T Cell Therapy

In the past decade, chimeric antigen receptor (CAR) T cell technology has revolutionized cancer immunotherapy. This strategy uses synthetic CARs to redirect the patient's own immune cells to recognize specific antigens expressed on the surface of tumor cells. The unprecedented success of anti-CD19 CAR T cell therapy against B cell malignancies has resulted in its approval by the US Food and Drug Administration (FDA) in 2017. However, major scientific challenges still remain to be addressed for the broad use of CAR T cell therapy. These include severe toxicities, limited efficacy against solid tumors, and immune suppression in the hostile tumor microenvironment. Furthermore, CAR T cell therapy is a personalized medicine of which the production is time- and resource-intensive, which makes it very expensive. All these factors drive new innovations to engineer more powerful CAR T cells with improved antitumor activity, which are reviewed in this manuscript.

Optimizing the Clinical Impact of CAR-T Cell Therapy in B-Cell Acute Lymphoblastic Leukemia: Looking Back While Moving Forward

Chimeric antigen receptor T-cell (CAR-T) therapy has been successful in creating extraordinary clinical outcomes in the treatment of hematologic malignancies including relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). With several FDA approvals, CAR-T therapy is recognized as an alternative treatment option for particular patients with certain conditions of B-ALL, diffuse large B-cell lymphoma, mantle cell lymphoma, follicular lymphoma, or multiple myeloma. However, CAR-T therapy for B-ALL can be surrounded by challenges such as various adverse events including the life-threatening cytokine release syndrome (CRS) and neurotoxicity, B-cell aplasia-associated hypogammaglobulinemia and agammaglobulinemia, and the alloreactivity of allogeneic CAR-Ts. Furthermore, recent advances such as improvements in media design, the reduction of ex vivo culturing duration, and other phenotype-determining factors can still create room for a more effective CAR-T therapy in R/R B-ALL. Herein, we review preclinical and clinical strategies with a focus on novel studies aiming to address the mentioned hurdles and stepping further towards a milestone in CAR-T therapy of B-ALL.

Gene editing to enhance the efficacy of cancer cell therapies

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

Allogeneic CAR Invariant Natural Killer T Cells Exert Potent Antitumor Effects through Host CD8 T-Cell Cross-Priming

PURPOSE

The development of allogeneic chimeric antigen receptor (CAR) T-cell therapies for off-the-shelf use is a major goal that faces two main immunologic challenges, namely the risk of graft-versus-host disease (GvHD) induction by the transferred cells and the rejection by the host immune system limiting their persistence. In this work we assessed the direct and indirect antitumor effect of allogeneic CAR-engineered invariant natural killer T (iNKT) cells, a cell population without GvHD-induction potential that displays immunomodulatory properties.

EXPERIMENTAL DESIGN

After assessing murine CAR iNKT cells direct antitumor effects in vitro and in vivo, we employed an immunocompetent mouse model of B-cell lymphoma to assess the interaction between allogeneic CAR iNKT cells and endogenous immune cells.

RESULTS

We demonstrate that allogeneic CAR iNKT cells exerted potent direct and indirect antitumor activity when administered across major MHC barriers by inducing tumor-specific antitumor immunity through host CD8 T-cell cross-priming.

CONCLUSIONS

In addition to their known direct cytotoxic effect, allogeneic CAR iNKT cells induce host CD8 T-cell antitumor responses, resulting in a potent antitumor effect lasting longer than the physical persistence of the allogeneic cells. The utilization of off-the-shelf allogeneic CAR iNKT cells could meet significant unmet needs in the clinic.

Advances in Universal CAR-T Cell Therapy

Chimeric antigen receptor T (CAR-T) cell therapy achieved extraordinary achievements results in antitumor treatments, especially against hematological malignancies, where it leads to remarkable, long-term antineoplastic effects with higher target specificity. Nevertheless, some limitations persist in autologous CAR-T cell therapy, such as high costs, long manufacturing periods, and restricted cell sources. The development of a universal CAR-T (UCAR-T) cell therapy is an attractive breakthrough point that may overcome most of these drawbacks. Here, we review the progress and challenges in CAR-T cell therapy, especially focusing on comprehensive comparison in UCAR-T cell therapy to original CAR-T cell therapy. Furthermore, we summarize the developments and concerns about the safety and efficiency of UCAR-T cell therapy. Finally, we address other immune cells, which might be promising candidates as a complement for UCAR-T cells. Through a detailed overview, we describe the current landscape and explore the prospect of UCAR-T cell therapy.

From Hematopoietic Stem Cell Transplantation to Chimeric Antigen Receptor Therapy: Advances, Limitations and Future Perspectives

Chimeric antigen receptor (CAR) T-cell therapy was envisioned as a mechanism to re-direct effector T-cells to eliminate tumor cells. CARs are composed of the variable region of an antibody that binds a native cancer antigen coupled to the signaling domain of a TCR and co-stimulatory molecules. Its success and approval by the U.S. Food and Drug Administration for the treatment of B-cell malignancies revolutionized the immunotherapy field, leading to extensive research on its possible application for other cancer types. In this review, we will focus on the evolution of CAR-T cell therapy outlining current technologies as well as major obstacles for its wide application. We will highlight achievements, the efforts to increase efficacy and to evolve into an off-the-shelf treatment, and as a possible future treatment for non-cancer related diseases.

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

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

Choosing the Right Tool for Genetic Engineering: Clinical Lessons from Chimeric Antigen Receptor-T Cells

T cell modification with genes that encode chimeric antigen receptors (CAR-T cells) has shown tremendous promise for the treatment of B cell malignancies. The successful translation of CAR-T cell therapy to other tumor types, including solid tumors, is the next big challenge. As the field advances from second- to next-generation CAR-T cells comprising multiple genetic modifications, more sophisticated methods and tools to engineer T cells are being developed. Viral vectors, especially γ-retroviruses and lentiviruses, are traditionally used for CAR-T cell engineering due to their high transduction efficiency. However, limited genetic cargo, high costs of production under good manufacturing practice (GMP) conditions, and the high regulatory demands are obstacles for widespread clinical translation. To overcome these limitations, different nonviral approaches are being explored at a preclinical or clinical level, including transposon/transposase systems and mRNA electroporation and nonintegrating DNA nanovectors. Genome editing tools that allow efficient knockout of particular genes and/or site-directed integration of the CAR and/or other transgenes into the genome are also being evaluated for CAR-T cell engineering. In this review, we discuss the development of viral and nonviral vectors used to generate CAR-T cells, focusing on their advantages and limitations. We also discuss the lessons learned from clinical trials using the different genetic engineering tools, with special focus on safety and efficacy.

Cellular Therapy Updates in B-Cell Lymphoma: The State of the CAR-T

Simple Summary

B-cell lymphomas are the most commonly occurring blood cancer and the second leading cause of cancer-related death among blood cancers. Chemotherapy and stem cell transplantation have long served as the standard therapies for relapsed or refractory aggressive B-cell lymphomas with very poor survival, historically. Recently, the development of multiple chimeric antigen receptor T-cell (CAR-T) products has translated into dramatically improved outcomes and survival for patients with relapsed or refractory B-cell lymphoma. Meanwhile, basic, translational and clinical development within the field has progressed rapidly. The aim of this review is to summarize the current state of the art of CAR-T therapies for B-cell lymphomas within this rapidly evolving field, focusing on current United States Food and Drug Administration (US FDA)-approved products and a selection of promising areas of future clinical development.

Abstract

Non-Hodgkin Lymphoma accounts for >460,000 cases and >240,000 deaths globally and >77,000 cases and >20,000 deaths in the U.S. annually, with ~85% of cases being B-cell malignancies. Until recently, patients with relapsed/refractory B-cell lymphoma following standard chemotherapy in combination with anti-CD20 monoclonal antibodies and autologous stem cell transplantation experienced a median overall survival (OS) of <6 months. However, with the approval of four different CD-19 CAR-T therapies between 2017 and 2021, approximately 60–80% of patients receiving CAR-T therapy now achieve an objective response with >3 years median OS. Here, we review the current state of the art of CD19 CAR-T therapies for B-cell lymphomas, focusing on current updates in US FDA-approved products, along with their associated efficacy and toxicities. Lastly, we highlight a selection of promising clinical developments in the field, including various novel strategies to increase CAR-T therapy efficacy while mitigating toxicity.

Challenges and Prospects for Designer T and NK Cells in Glioblastoma Immunotherapy

Glioblastoma (GBM) is the most prevalent, aggressive primary brain tumour with a dismal prognosis. Treatment at diagnosis has limited efficacy and there is no standardised treatment at recurrence. New, personalised treatment options are under investigation, although challenges persist for heterogenous tumours such as GBM. Gene editing technologies are a game changer, enabling design of novel molecular-immunological treatments to be used in combination with chemoradiation, to achieve long lasting survival benefits for patients. Here, we review the literature on how cutting-edge molecular gene editing technologies can be applied to known and emerging tumour-associated antigens to enhance chimeric antigen receptor T and NK cell therapies for GBM. A tight balance of limiting neurotoxicity, avoiding tumour antigen loss and therapy resistance, while simultaneously promoting long-term persistence of the adoptively transferred cells must be maintained to significantly improve patient survival. We discuss the opportunities and challenges posed by the brain contexture to the administration of the treatments and achieving sustained clinical responses.

Mutant B2M-HLA-E and B2M-HLA-G fusion proteins protects universal chimeric antigen receptor-modified T cells from allogeneic NK cell-mediated lysis

Recent studies have indicated the antitumor activity and reduced allogeneic response of universal chimeric antigen receptor-modified T (UCAR T) cells lacking endogenous T cell receptors and beta-2 microglobulin (B2M) generated using gene-editing technologies. However, these cells are vulnerable to lysis by allogeneic natural killer (NK) cells due to their lack of human leukocyte antigen (HLA) class I molecule expression. Here, constitutive expression of mutant B2M-HLA-E (mBE) and B2M-HLA-G (mBG) fusion proteins in anti-CD19 UCAR T (UCAR T-19) cells was conducted to protect against allogeneic NK cell-mediated lysis. The ability of cells expressing mBE or mBG to resist NK cell-mediated lysis was observed in gene-edited Jurkat CAR19 cells. UCAR T-19 cells constitutively expressing the mBE and mBG fusion proteins were manufactured and showed effective and specific anti-tumor activity. Constitutive expression of the mBE and mBG fusion proteins in UCAR T-19 cells prevented allogeneic NK cell-mediated lysis. In addition, these cells were not recognizable by allogeneic T cells. Additional experiments, including those in animal models and clinical trials, are required to evaluate the safety and efficacy of UCAR T-19 cells that constitutively express mBE and mBG.

Advances in Adoptive Cell Therapy Using Induced Pluripotent Stem Cell-Derived T Cells

Adoptive cell therapy (ACT) using chimeric antigen receptor (CAR) T cells holds impressive clinical outcomes especially in patients who are refractory to other kinds of therapy. However, many challenges hinder its clinical applications. For example, patients who undergo chemotherapy usually have an insufficient number of autologous T cells due to lymphopenia. Long-term ex vivo expansion can result in T cell exhaustion, which reduces the effector function. There is also a batch-to-batch variation during the manufacturing process, making it difficult to standardize and validate the cell products. In addition, the process is labor-intensive and costly. Generation of universal off-the-shelf CAR T cells, which can be broadly given to any patient, prepared in advance and ready to use, would be ideal and more cost-effective. Human induced pluripotent stem cells (iPSCs) provide a renewable source of cells that can be genetically engineered and differentiated into immune cells with enhanced anti-tumor cytotoxicity. This review describes basic knowledge of T cell biology, applications in ACT, the use of iPSCs as a new source of T cells and current differentiation strategies used to generate T cells as well as recent advances in genome engineering to produce next-generation off-the-shelf T cells with improved effector functions. We also discuss challenges in the field and future perspectives toward the final universal off-the-shelf immunotherapeutic products.

Scalable Manufacturing of CAR T cells for Cancer Immunotherapy

As of April 2021, there are five commercially available chimeric antigen receptor (CAR) T cell therapies for hematological malignancies. With the current transition of CAR T cell manufacturing from academia to industry, there is a shift toward Good Manufacturing Practice (GMP)-compliant closed and automated systems to ensure reproducibility and to meet the increased demand for cancer patients. In this review we describe current CAR T cells clinical manufacturing models and discuss emerging technological advances that embrace scaling and production optimization. We summarize measures being used to shorten CAR T-cell manufacturing times and highlight regulatory challenges to scaling production for clinical use.

Statement of Significance ∣

As the demand for CAR T cell cancer therapy increases, several closed and automated production platforms are being deployed, and others are in development.This review provides a critical appraisal of these technologies that can be leveraged to scale and optimize the production of next generation CAR T cells.

Combination strategies to maximize the benefits of cancer immunotherapy

Immunotherapies such as immune checkpoint blockade (ICB) and adoptive cell therapy (ACT) have revolutionized cancer treatment, especially in patients whose disease was otherwise considered incurable. However, primary and secondary resistance to single agent immunotherapy often results in treatment failure, and only a minority of patients experience long-term benefits. This review article will discuss the relationship between cancer immune response and mechanisms of resistance to immunotherapy. It will also provide a comprehensive review on the latest clinical status of combination therapies (e.g., immunotherapy with chemotherapy, radiation therapy and targeted therapy), and discuss combination therapies approved by the US Food and Drug Administration. It will provide an overview of therapies targeting cytokines and other soluble immunoregulatory factors, ACT, virotherapy, innate immune modifiers and cancer vaccines, as well as combination therapies that exploit alternative immune targets and other therapeutic modalities. Finally, this review will include the stimulating insights from the 2020 China Immuno-Oncology Workshop co-organized by the Chinese American Hematologist and Oncologist Network (CAHON), the China National Medical Product Administration (NMPA) and Tsinghua University School of Medicine.

Optimized two-step electroporation process to achieve efficient nonviral-mediated gene insertion into primary T cells

The development of gene editing technologies over the past years has allowed the precise and efficient insertion of transgenes into the genome of various cell types. Knock‐in approaches using homology‐directed repair and designer nucleases often rely on viral vectors, which can considerably impact the manufacturing cost and timeline of gene‐edited therapeutic products. An attractive alternative would be to use naked DNA as a repair template. However, such a strategy faces challenges such as cytotoxicity from double‐stranded DNA (dsDNA) to primary cells. Here, we sought to study the kinetics of transcription activator‐like effector nuclease (TALEN)‐mediated gene editing in primary T cells to improve nonviral gene knock‐in. Harnessing this knowledge, we developed a rapid and efficient gene insertion strategy based on either short single‐stranded oligonucleotides or large (2 Kb) linear naked dsDNA sequences. We demonstrated that a time‐controlled two‐step transfection protocol can substantially improve the efficiency of nonviral transgene integration in primary T cells. Using this approach, we achieved modification of up to ˜ 30% of T cells when inserting a chimeric antigen receptor (CAR) at the T‐cell receptor alpha constant region (TRAC) locus to generate ‘off‐the shelf’ CAR‐T cells.

Genetical engineering for NK and T cell immunotherapy with CRISPR/Cas9 technology: Implications and challenges

Immunotherapy has become one of the most promising strategies in cancer therapies. Among the therapeutic alternatives, genetically engineered NK/T cell therapies have emerged as powerful and innovative therapeutic modalities for cancer patients with precise targeting and impressive efficacy. Nonetheless, this approach still faces multiple challenges, such as immunosuppressive tumor microenvironment, exhaustion of immune effector cells in tumors, off-target effects manufacturing complexity, and poor infiltration of effector cells, all of which need to be overcome for further utilization to cancers. Recently, CRISPR/Cas9 genome editing technology, with the goal of enhancing the efficacy and increasing the availability of engineered effector cell therapies, has shown considerable potential in the novel strategies and options to overcome these limitations. Here we review the current progress of the applications of CRISPR in cancer immunotherapy. Furthermore, we discuss issues related to the NK/T cell applications, gene delivery methods, efficiency, challenges, and implications of CRISPR/Cas9.

BCMA in Multiple Myeloma-A Promising Key to Therapy

Despite the discoveries of numerous agents including next generation proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies, multiple myeloma (MM) remains an incurable disease. The field of myeloma treatment in refractory or relapsed patients after standard therapy entered a new era due to the B-cell maturation antigen (BMCA) targeted approach. BCMA is a member of the tumor necrosis factor receptor family with high expression in mature B-lymphocytes and plasma cells. Given the understanding of BCMA mechanism of action in MM, BCMA plays a promising role as a therapeutic target. Several clinical trials are underway to evolve the current BCMA targeted treatment concept such as antibody-drug conjugates (ADCs), bispecific T cell engagers (BITEs) and chimeric antigen receptor (CAR) T cell therapy. Current results of representative BCMA trials may close the gap of the unmet clinical need to further improve the outcome of heavily pretreated MM patients with the potency to change the paradigm in newly diagnosed and refractory MM. This comprehensive review will give an update on various BMCA targeted treatment modalities (ADCs, BITEs, CAR T cell therapy) and its existing results on efficacy and safety from preclinical and clinical trials.

Recent Progress in Genome Editing for Gene Therapy Applications: The French Perspective

Recent advances in genome editing tools, especially novel developments in the clustered regularly interspaced short palindromic repeats associated to Cas9 nucleases (CRISPR/Cas9)-derived editing machinery, have revolutionized not only basic science but, importantly, also the gene therapy field. Their flexibility and ability to introduce precise modifications in the genome to disrupt or correct genes or insert expression cassettes in safe harbors in the genome underline their potential applications as a medicine of the future to cure many genetic diseases. In this review, we give an overview of the recent progress made by French researchers in the field of therapeutic genome editing, while putting their work in the general context of advances made in the field. We focus on recent hematopoietic stem cell gene editing strategies for blood diseases affecting the red blood cells or blood coagulation as well as lysosomal storage diseases. We report on a genome editing-based therapy for muscular dystrophy and the potency of T cell gene editing to increase anticancer activity of chimeric antigen receptor T cells to combat cancer. We will also discuss technical obstacles and side effects such as unwanted editing activity that need to be surmounted on the way toward a clinical implementation of genome editing. We propose here improvements developed today, including by French researchers to overcome the editing-related genotoxicity and improve editing precision by the use of novel recombinant nuclease-based systems such as nickases, base editors, and prime editors. Finally, a solution is proposed to resolve the cellular toxicity induced by the systems employed for gene editing machinery delivery.

Molecular Markers and Targets in Melanoma

Melanoma develops as a result of several genetic alterations, with UV radiation often acting as a mutagenic risk factor. Deep knowledge of the molecular signaling pathways of different types of melanoma allows better characterization and provides tools for the development of therapies based on the intervention of signals promoted by these cascades. The latest World Health Organization classification acknowledged the specific genetic drivers leading to melanoma and classifies melanocytic lesions into nine distinct categories according to the associate cumulative sun damage (CSD), which correlates with the molecular alterations of tumors. The largest groups are melanomas associated with low-CSD or superficial spreading melanomas, characterized by frequent presentation of the BRAFV600 mutation. High-CSD melanomas include lentigo maligna type and desmoplastic melanomas, which often have a high mutation burden and can harbor NRAS, BRAFnon-V600E, or NF1 mutations. Non-CSD-associated melanomas encompass acral and mucosal melanomas that usually do not show BRAF, NRAS, or NF1 mutations (triple wild-type), but in a subset may have KIT or SF3B1 mutations. To improve survival, these driver alterations can be treated with targeted therapy achieving significant antitumor activity. In recent years, relevant improvement in the prognosis and survival of patients with melanoma has been achieved, since the introduction of BRAF/MEK tyrosine kinase inhibitors and immune checkpoint inhibitors. In this review, we describe the current knowledge of molecular pathways and discuss current and potential therapeutic targets in melanoma, focusing on their clinical relevance of development.