Identification of Predictive Biomarkers for Cytokine Release Syndrome after Chimeric Antigen Receptor T-cell Therapy for Acute Lymphoblastic Leukemia

A combination of humanised anti-CD19 and anti-BCMA CAR T cells in patients with relapsed or refractory multiple myeloma: a single-arm, phase 2 trial

BACKGROUND

Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy has been shown to have activity in patients with relapsed or refractory multiple myeloma. Reports have suggested that a small subgroup of less differentiated myeloma clones express CD19 and anti-CD19 CAR T-cell therapy has shown activity in some of these patients. We aimed to assess the activity and safety of a combination of humanised anti-CD19 and anti-BCMA CAR T cells in patients with relapsed or refractory multiple myeloma.

METHODS

We did a single-centre, single-arm, phase 2 trial at the Affiliated Hospital of Xuzhou Medical University in China. Patients were eligible if they were aged 18-69 years, had histologically confirmed multiple myeloma, a Karnofsky Performance Score of 50 points or more, and met the International Myeloma Working Group diagnostic criteria for relapsed or refractory disease. Fludarabine (three daily doses of 30mg/m²) and cyclophosphamide (one daily dose of 750 mg/m²) were used to deplete lymphocytes before infusion of humanised anti-CD19 CAR T cells (1 × 10⁶ cells per kg) and murine anti-BCMA CAR T cells (1 × 10⁶ cells per kg). The primary outcome was the proportion of patients who achieved an overall response. Responses were assessed according to the International Myeloma Working Group criteria. This study is registered with the Chinese Clinical Trial Registration Center, number ChiCTR-OIC-17011272.

FINDINGS

From May 1, 2017, to Jan 20, 2019, 22 patients were enrolled and 21 received an infusion of CAR T cells and were evaluable for safety and activity analyses. At a median follow-up of 179 days (IQR 72-295), 20 (95%) of 21 patients had an overall response, including nine (43%) stringent complete responses, three (14%) complete responses, five (24%) very good partial responses, and three (14%) partial responses. The most common adverse events included cytokine release syndrome (19 [90%] of 21), including 18 patients (86%) with grade 1-2 cytokine release syndrome. The most common serious adverse events were haematological toxicities, which occurred in 20 (95%) of 21 patients. Common grade 3 or higher adverse events included neutropenia (18 [86%]), anaemia (13 [62%]), and thrombocytopenia (13 [62%]). One patient died due to cerebral hemorrhage, which was considered related to sustained thrombocytopenia. No deaths were judged to be treatment-related.

INTERPRETATION

Our results confirm that combined infusion of humanised anti-CD19 and anti-BCMA CAR T cells is feasible in patients with relapsed or refractory multiple myeloma, and the preliminary activity observed warrants further investigation in randomised trials. This dual CAR-T cell combinations might be a promising treatment option for relapsed or refractory multiple myeloma.

FUNDING

National Natural Science Foundation of China, Natural Science Foundation, Key Research and Development Plan of Jiangsu.

Phase I Study of Lentiviral-Transduced Chimeric Antigen Receptor-Modified T Cells Recognizing Mesothelin in Advanced Solid Cancers

This phase I study investigated the safety and activity of lentiviral-transduced chimeric antigen receptor (CAR)-modified autologous T cells redirected against mesothelin (CART-meso) in patients with malignant pleural mesothelioma, ovarian carcinoma, and pancreatic ductal adenocarcinoma. Fifteen patients with chemotherapy-refractory cancer (n = 5 per indication) were treated with a single CART-meso cell infusion. CART-meso cells were engineered by lentiviral transduction with a construct composed of the anti-mesothelin single-chain variable fragment derived from the mouse monoclonal antibody SS1 fused to intracellular signaling domains of 4-1BB and CD3zeta. Patients received 1-3 × 10⁷ or 1-3 × 10⁸ CART-meso cells/m² with or without 1.5 g/m² cyclophosphamide. Lentiviral-transduced CART-meso cells were well tolerated; one dose-limiting toxicity (grade 4, sepsis) occurred at 1-3 × 10⁷/m² CART-meso without cyclophosphamide. The best overall response was stable disease (11/15 patients). CART-meso cells expanded in the blood and reached peak levels by days 6-14 but persisted transiently. Cyclophosphamide pre-treatment enhanced CART-meso expansion but did not improve persistence beyond 28 days. CART-meso DNA was detected in 7/10 tumor biopsies. Human anti-chimeric antibodies (HACA) were detected in the blood of 8/14 patients. CART-meso cells were well tolerated and expanded in the blood of all patients but showed limited clinical activity. Studies evaluating a fully human anti-mesothelin CAR are ongoing.

DNA sensing by the cGAS-STING pathway in health and disease

The detection of pathogens through nucleic acid sensors is a defining principle of innate immunity. RNA-sensing and DNA-sensing receptors sample subcellular compartments for foreign nucleic acids and, upon recognition, trigger immune signalling pathways for host defence. Over the past decade, our understanding of how the recognition of nucleic acids is coupled to immune gene expression has advanced considerably, particularly for the DNA-sensing receptor cyclic GMP-AMP synthase (cGAS) and its downstream signalling effector stimulator of interferon genes (STING), as well as the molecular components and regulation of this pathway. Moreover, the ability of self-DNA to engage cGAS has emerged as an important mechanism fuelling the development of inflammation and implicating the cGAS-STING pathway in human inflammatory diseases and cancer. This detailed mechanistic and biological understanding is paving the way for the development and clinical application of pharmacological agonists and antagonists in the treatment of chronic inflammation and cancer.

A Modeling Framework to Characterize Cytokine Release upon T-Cell-Engaging Bispecific Antibody Treatment: Methodology and Opportunities

T‐cell–engaging bispecific antibodies (T‐BsAbs) are an important class of antibody therapeutics in immuno‐oncology. T‐BsAbs simultaneously bind to CD3 on T cells and a tumor‐associated antigen on tumor cells, activate T cells, and redirect T cells’ cytotoxicity against tumor cells. Cytokine release syndrome (CRS), a common dose‐limiting adverse event for T‐BsAbs, is associated with T‐cell activation. A “priming” dose strategy (i.e., a lower initial dose followed by a higher maintenance dose) has been implemented in the clinic to mitigate CRS and to achieve efficacious doses with T‐BsAbs. So far, the selection of the optimal priming dosing regimen is largely empirical. A “fit‐for‐purpose” semimechanistic pharmacokinetic/pharmacodynamic model was developed to characterize the cytokine release profiles upon T‐BsAb treatment, including the priming effect observed with repeated dosing. This model can be utilized to simulate cytokine profiles following various dosing regimens and may assist the design of clinical dosing strategies for T‐BsAbs programs.

Bispecific Antibodies Enable Synthetic Agonistic Receptor-Transduced T Cells for Tumor Immunotherapy

PURPOSE

Genetically engineered T cells are powerful anticancer treatments but are limited by safety and specificity issues. We herein describe an MHC-unrestricted modular platform combining autologous T cells, transduced with a targetable synthetic agonistic receptor (SAR), with bispecific antibodies (BiAb) that specifically recruit and activate T cells for tumor killing.

EXPERIMENTAL DESIGN

BiAbs of different formats were generated by recombinant expression. T cells were retrovirally transduced with SARs. T-cell activation, proliferation, differentiation, and T-cell-induced lysis were characterized in three murine and human tumor models in vitro and in vivo.

RESULTS

Murine T cells transduced with SAR composed of an extracellular domain EGFRvIII fused to CD28 and CD3ζ signaling domains could be specifically recruited toward murine tumor cells expressing EpCAM by anti-EGFRvIII × anti-EpCAM BiAb. BiAb induced selective antigen-dependent activation, proliferation of SAR T cells, and redirected tumor cell lysis. Selectivity was dependent on the monovalency of the antibody for EGFRvIII. We identified FAS ligand as a major mediator of killing utilized by the T cells. Similarly, human SAR T cells could be specifically redirected toward mesothelin-expressing human pancreatic cancer cells. In vivo, treatment with SAR T cells and BiAb mediated antitumoral activity in three human pancreatic cancer cell xenograft models. Importantly, SAR activity, unlike CAR activity, was reversible in vitro and in vivo.

CONCLUSIONS

We describe a novel ACT platform with antitumor activity in murine and human tumor models with a distinct mode of action that combines adoptive T-cell therapy with bispecific antibodies.

Cellular therapy: Immune-related complications

The advent of chimeric antigen receptor T (CAR-T) and the burgeoning field of cellular therapy has revolutionized the treatment of relapsed/refractory leukemia and lymphoma. This personalized "living therapy" is highly effective against a number of malignancies, but this efficacy is tempered by side effects relatively unique to immunotherapies, including CAR-T. The overwhelming release of cytokines and chemokines by activated CAR-T and other secondarily activated immune effector cells can lead to cytokine release syndrome (CRS), which can have clinical and pathophysiology similarities to systemic inflammatory response syndrome and macrophage activating syndrome/hemophagocytic lymphohistiocytosis. Tocilizumab, an anti-IL6 receptor antibody, was recently FDA approved for treatment of CRS after CAR-T based on its ability to mitigate CRS in many patients. Unfortunately, some patients are refractory and additional therapies are needed. Patients treated with CAR-T can also develop neurotoxicity and, as the biology is poorly understood, current therapeutic interventions are limited to supportive care. Nevertheless, a number of recent studies have shed new light on the pathophysiology of CAR-T-related neurotoxicity, which will hopefully lead to effective treatments. In this review we discuss some of the mechanistic contributions intrinsic to the CAR-T construct, the tumor being treated, and the individual patient that impact the development and severity of CRS and neurotoxicity. As CAR-T and cellular therapy have redefined the concept of personalized medicine, so too will personalization be necessary in managing the unique side effects of these therapies.

What is the Role of Hematopoietic Cell Transplantation (HCT) for Pediatric Acute Lymphoblastic Leukemia (ALL) in the Age of Chimeric Antigen Receptor T-Cell (CART) Therapy?

CD19 chimeric antigen receptor T-cell (CART) therapy has revolutionized the treatment of patients with relapsed/refractory hematologic malignancies, especially B-cell acute lymphoblastic leukemia. As CART immunotherapy expands from clinical trials to FDA-approved treatments, a consensus among oncologists and hematopoietic cell transplant (HCT) physicians is needed to identify which patients may benefit from consolidative HCT post-CART therapy. Here, we review CD19 CART therapy and the outcomes of published clinical trials, highlighting the use of post-CART HCT and the pattern of relapse after CD19 CART. At this time, the limited available long-term data from clinical trials precludes us from making definitive HCT recommendations. However, based on currently available data, we propose that consolidative HCT post-CART therapy be considered for all HCT-eligible patients and especially for pediatric patients with KMT2A-rearranged B-cell acute lymphoblastic leukemia.

Chimeric Antigen Receptor T-Cell Therapy: Reach to Solid Tumor Experience

Chimeric antigen receptor (CAR) modified T-cell therapy, a unique platform technology highlighting precision medicine through utilization of molecular biology and cell-based therapeutics has shown unprecedented rates in patients with hematological malignancies such as acute lymphocyte leukemia, non-Hodgkin's lymphoma and multiple myeloma (MM). With the approval of CD19-targeted CAR T-cells by the Food and Drug Administration in acute lymphoblastic leukemia (ALL) and NHL, this technology is positioned for aggressive expansion to combination therapeutic opportunities and proof of principle towards utility in other malignant disorders. However, despite the impressive results seen with hematological malignancies, CAR T-cells have shown limited efficacy in solid tumors with several unsuccessful preclinical studies. Regardless, these attempts have provided us with a better understanding of the imminent challenges specific to solid tumors even if they have not so far led to expanded clinical treatment opportunities outside ALL/NHL/MM. This review summarizes our current understanding of CAR T-cell mechanism of action, while presenting the major limitations of CAR T-cell derived treatments in solid tumors. We further discuss recent findings and present new potential strategies to overcome the challenges facing solid tumor targeting by CAR T-cell platforms.

IFN-γ and TNF-α aggravate endothelial damage caused by CD123-targeted CAR T cell

Background: CD123-targeted chimeric antigen receptor (CAR) T cell (CART123) for the treatment of acute myeloid leukemia (AML) and blastic plasmacytoid dendritic cell neoplasm has exhibited potential in clinical trials. However, capillary leakage syndrome, which is associated with endothelial cells damage, is under intensive focus in CART123 therapy.

Purpose: The present study aimed to explore the change in CD123 in endothelial cells and the injury to endothelial cells caused by CART123.

Methods: The expression of CD123 and cytotoxicity were assessed by flow cytometry. Cytokine release was assessed by ELISA. An in vitro co-culture model was designed to mimic the status, wherein CART123 was stimulated and cytokines were released.

Results: In the current study, CART123 exhibited cytotoxicity and the effects of cytokine production on endothelium, and the upregulation of CD123 enhanced the cytotoxicity. The addition of interferon (IFN)-γ and tumor necrosis factor (TNF)-α neutralizing antibodies can effectively reverse the upregulation of CD123 on the endothelial cells caused by CART123, while the cytotoxicity of CART123 in AML cell lines was not affected in vitro. Second, we proved that CD123 expresses in CART123 and would be upregulated after activation, putatively causing an overactivated and fratricide effect.

Conclusion: In summary, this study identified that the expression of CD123 on endothelial cells could be upregulated when co-cultured with CART123. Furthermore, IFN-γ and TNF-α could aggravate endothelial damage caused by CART123 in vitro.

Tocilizumab for the treatment of chimeric antigen receptor T cell-induced cytokine release syndrome

Introduction: Cancer-directed immunotherapies are transforming the landscape in oncology as new and exciting therapies move from the laboratory to the bedside. Chimeric antigen receptor T (CAR-T) cells are one of these novel therapies, demonstrating impressive efficacy against B-cell malignancies. With the development of new therapies, it is not uncommon to identify new and unanticipated toxicities. CAR-T cells cause unique toxicities not typically found with traditional cytotoxic chemotherapy or small molecule inhibitors. Areas covered: CAR-T cell associated toxicities include cytokine release syndrome (CRS) and CAR-T cell-related encephalopathy syndrome (CRES), alternatively known as immune effector cell-associated neurotoxicity syndrome (ICANS). Prompt identification and management of CRS and CRES are imperative for the prevention of life-threatening complications of these innovative therapies. This literature review describes the seminal trials of CD19-directed immunotherapy and the pathophysiology and management of the toxicities found with CAR-T cells. In addition, the use of the interleukin-6 receptor antibody tocilizumab for CRS is reviewed. Expert opinion: This review describes the recommended management of CRS and CRES and examines the current limitations in management. Alternative therapies for the treatment of CAR-T cell related toxicities are also explored. Furthermore, the review proposes future directions for research.

Evaluating tisagenlecleucel and its potential in the treatment of relapsed or refractory diffuse large B cell lymphoma: evidence to date

Chimeric antigen receptor (CAR) T cells have changed the treatment landscape of relapsed or refractory diffuse large B cell lymphoma. This review focuses on the biology of tisagenlecleucel and the clinical data that support its use in this setting. In addition, we discuss how it compares to other CAR T products, the financial implications for payers, and ongoing trials.

Cytokine release syndrome and neurologic toxicities associated with chimeric antigen receptor T-cell therapy: A comprehensive review of emerging grading models

Advances in the fields of immuno-oncology and T-cell engineering have brought autologous chimeric antigen receptor T-cell (CART) therapies from the bench to the bedside. At present, two CART products that target CD19 are commercially available: tisagenlecleucel and axicabtagene ciloleucel. They have demonstrated remarkable efficacy for their particular indications. One challenge is to compare the safety among commercially available and clinical trial CART treatments due to the use of different grading models to assess the severity of cytokine release syndrome and neurotoxicity. An unmet need exists to harmonize current grading models in order to develop uniform treatment strategies to manage these toxicities. Here, we attempt to summarize the evolution of the various grading systems for cytokine release syndrome and neurotoxicity and also highlight the major differences among them, whenever applicable.

Mechanisms of resistance to CAR T cell therapy

The successes with chimeric antigen receptor (CAR) T cell therapy in early clinical trials involving patients with pre-B cell acute lymphoblastic leukaemia (ALL) or B cell lymphomas have revolutionized anticancer therapy, providing a potentially curative option for patients who are refractory to standard treatments. These trials resulted in rapid FDA approvals of anti-CD19 CAR T cell products for both ALL and certain types of B cell lymphoma - the first approved gene therapies in the USA. However, growing experience with these agents has revealed that remissions will be brief in a substantial number of patients owing to poor CAR T cell persistence and/or cancer cell resistance resulting from antigen loss or modulation. Furthermore, the initial experience with CAR T cells has highlighted challenges associated with manufacturing a patient-specific therapy. Understanding the limitations of CAR T cell therapy will be critical to realizing the full potential of this novel treatment approach. Herein, we discuss the factors that can preclude durable remissions following CAR T cell therapy, with a primary focus on the resistance mechanisms that underlie disease relapse. We also provide an overview of potential strategies to overcome these obstacles in an effort to more effectively incorporate this unique therapeutic strategy into standard treatment paradigms.

Glial injury in neurotoxicity after pediatric CD19-directed chimeric antigen receptor T cell therapy

OBJECTIVE

To test whether systemic cytokine release is associated with central nervous system inflammatory responses and glial injury in immune effector cell-associated neurotoxicity syndrome (ICANS) after chimeric antigen receptor (CAR)-T cell therapy in children and young adults.

METHODS

We performed a prospective cohort study of clinical manifestations as well as imaging, pathology, CSF, and blood biomarkers on 43 subjects ages 1 to 25 who received CD19-directed CAR/T cells for acute lymphoblastic leukemia (ALL).

RESULTS

Neurotoxicity occurred in 19 of 43 (44%) subjects. Nine subjects (21%) had CTCAE grade 3 or 4 neurological symptoms, with no neurotoxicity-related deaths. Reversible delirium, headache, decreased level of consciousness, tremor, and seizures were most commonly observed. Cornell Assessment of Pediatric Delirium (CAPD) scores ≥9 had 94% sensitivity and 33% specificity for grade ≥3 neurotoxicity, and 91% sensitivity and 72% specificity for grade ≥2 neurotoxicity. Neurotoxicity correlated with severity of cytokine release syndrome, abnormal past brain magnetic resonance imaging (MRI), and higher peak CAR-T cell numbers in blood, but not cerebrospinal fluid (CSF). CSF levels of S100 calcium-binding protein B and glial fibrillary acidic protein increased during neurotoxicity, indicating astrocyte injury. There were concomitant increases in CSF white blood cells, protein, interferon-γ (IFNγ), interleukin (IL)-6, IL-10, and granzyme B (GzB), with concurrent elevation of serum IFNγ IL-10, GzB, granulocyte macrophage colony-stimulating factor, macrophage inflammatory protein 1 alpha, and tumor necrosis factor alpha, but not IL-6. We did not find direct evidence of endothelial activation.

INTERPRETATION

Our data are most consistent with ICANS as a syndrome of systemic inflammation, which affects the brain through compromise of the neurovascular unit and astrocyte injury. ANN NEUROL 2019.

The Other Side of CAR T-Cell Therapy: Cytokine Release Syndrome, Neurologic Toxicity, and Financial Burden

Immune effector cells, including T cells and natural killer cells, which are genetically engineered to express a chimeric antigen receptor (CAR), constitute a powerful new class of therapeutic agents to treat patients with hematologic malignancies. Several CAR T-cell trials have shown impressive remission rates in patients with relapsed/refractory hematologic cancers. Although the clinical responses of these agents in hematologic malignancies have been very encouraging, they have also produced substantial morbidity and occasionally mortality resulting from toxicity. With more experience and collaboration, hopefully the toxicities and the costs will come down, increasing the availability of CAR T cells to patients in need.

Synthetic TRuC receptors engaging the complete T cell receptor for potent anti-tumor response

T cells expressing CD19-targeting chimeric antigen receptors (CARs) reveal high efficacy in the treatment of B cell malignancies. Here, we report that T cell receptor fusion constructs (TRuCs) comprising an antibody-based binding domain fused to T cell receptor (TCR) subunits can effectively reprogram an intact TCR complex to recognize tumor surface antigens. Unlike CARs, TRuCs become a functional component of the TCR complex. TRuC-T cells kill tumor cells as potently as second-generation CAR-T cells, but at significant lower cytokine release and despite the absence of an extra co-stimulatory domain. TRuC-T cells demonstrate potent anti-tumor activity in both liquid and solid tumor xenograft models. In several models, TRuC-T cells are more efficacious than respective CAR-T cells. TRuC-T cells are shown to engage the signaling capacity of the entire TCR complex in an HLA-independent manner.

Improving the safety of CAR-T cell therapy by controlling CRS-related coagulopathy

The CD19-targeted chimeric antigen receptor T cell (CAR-T) therapy has been widely proved effective on relapsed and refractory (r/r) B cell acute lymphoblastic leukemia (B-ALL). Meanwhile, CAR-T therapy-related toxicities, including cytokine release syndrome (CRS) and neurological toxicities, are drawing researchers' attention. In addition, our research team notices that coagulopathy and even disseminated intravascular coagulation (DIC) are common problems during CAR-T therapy. In our phase 1/2 clinical trial (NCT02965092), 53 r/r B-ALL patients underwent leukapheresis on day - 11 and received lymphodepleting chemotherapy on day - 7 to day - 5. Finally, they received split infusions of anti-CD19 CAR-T cells on day 0 to day 2. Plasma concentrations of tissue factor (TF) and platelet endothelial cell adhesion molecular-1 (PECAM-1) were also measured to identify the mechanism of coagulation disorders. The overall 1-month remission rate of the 53 patients was 88.7%. During the treatment course, 19 patients experienced grade 3-4 CRS, 8 patients developed grade 2-3 neurological toxicities. Beyond that, 30 patients (30/53, 56.6%) suffered from coagulation disorders, and half of them should be diagnosed as DIC. Benefiting from replacement and anticoagulant therapy, 14 patients successfully got out of the conditions of DIC. Remarkably, the severity of coagulopathy was positively correlated with CRS grade. What is more, plasma TF and PECAM-1 levels indicated that vascular endothelial factors played key roles in the process of CRS-related coagulopathy. To conclude, coagulation disorders frequently happen during CAR-T therapy. TF and PECAM-1 are of great importance in the etiology and pathogenesis of coagulation problems. Early and proper interventions targeted at CRS-related coagulopathy contribute a lot to the control of side effects in CAR-T therapy.

CAR T-Cell Therapy: Adverse Events and Management

Chimeric antigen receptor (CAR) T-cell therapy is an exciting innovation in the treatment of cancer. However, CAR T-cell therapies have been associated with unique adverse events (AEs), including cytokine release syndrome (CRS) and neurologic events (also known as CAR T-cell-related encephalopathy syndrome [CRES] or, most recently, immune effector cell-associated neurotoxicity syndrome [ICANS]). Cytopenias and infection have also been observed. These AEs are treatable and reversible with appropriate treatment strategies but can become severe if not managed early. Therefore, it is essential for the advanced practitioner caring for patients undergoing these therapies to have a thorough understanding of the associated AEs, in particular their grading and management. Cytokine release syndrome and neurologic events can range in severity from low-grade symptoms that require supportive care only to a high-grade syndrome that can become life-threatening. While several grading and management recommendations have been used in clinical trials, until recently, there were no consistent grading and management guidelines. Here we provide the most recent recommendations, which have the ultimate goal of maintaining the benefits of CAR T-cell therapy, while minimizing life-threatening AEs. Improved understanding and management of AEs associated with CAR T-cell therapy will provide broader access to this innovative and potentially curative technology.

Toxicities of CD19 CAR-T cell immunotherapy

CD19-targeted chimeric antigen receptor (CAR)-modified T (CAR-T) cell immunotherapy has demonstrated impressive results in B-cell malignancies, and CAR-T cell therapies targeting other antigens are in development for other cancers. Cytokine release syndrome (CRS) and neurotoxicity can be life-threatening in a subset of patients. The severity of CRS and neurotoxicity can be impacted by the disease burden, lymphodepletion regimen, and CAR-T cell dose. Tocilizumab and corticosteroids have been used to manage these toxicities, enabling CD19 CAR-T cells to be administered without obvious compromise in efficacy. Consensus criteria for grading and managing toxicities will facilitate the widespread application of this treatment modality.

Innate and adaptive immune responses against human Puumala virus infection: immunopathogenesis and suggestions for novel treatment strategies for severe hantavirus-associated syndromes

Two related hyperinflammatory syndromes are distinguished following infection of humans with hantaviruses: haemorrhagic fever with renal syndrome (HFRS) seen in Eurasia and hantavirus pulmonary syndrome (HPS) seen in the Americas. Fatality rates are high, up to 10% for HFRS and around 35%-40% for HPS. Puumala virus (PUUV) is the most common HFRS-causing hantavirus in Europe. Here, we describe recent insights into the generation of innate and adaptive cell-mediated immune responses following clinical infection with PUUV. First described are studies demonstrating a marked redistribution of peripheral blood mononuclear phagocytes (MNP) to the airways, a process that may underlie local immune activation at the site of primary infection. We then describe observations of an excessive natural killer (NK) cell activation and the persistence of highly elevated numbers of NK cells in peripheral blood following PUUV infection. A similar vigorous CD8 Tcell response is also described, though Tcell responses decline with viraemia. Like MNPs, many NK cells and CD8 T cells also localize to the lung upon acute PUUV infection. Following this, findings demonstrating the ability of hantaviruses, including PUUV, to cause apoptosis resistance in infected target cells, are described. These observations, and associated inflammatory cytokine responses, may provide new insights into HFRS and HPS disease pathogenesis. Based on similarities between inflammatory responses in severe hantavirus infections and other hyperinflammatory disease syndromes, we speculate whether some therapeutic interventions that have been successful in the latter conditions may also be applicable in severe hantavirus infections.

Adverse Events Following Cancer Immunotherapy: Obstacles and Opportunities

Oncology has recently undergone a revolutionary change with widespread adoption of immunotherapy for many cancers. Immunotherapy using monoclonal antibodies against checkpoint molecules, including programmed death (PD)-1, PD ligand (PD-L)1, and cytotoxic T lymphocyte-associated antigen (CTLA)-4, is effective in a significant subset of patients. However, immune-related adverse events (irAEs) have emerged as frequent complications of checkpoint blockade, likely due to the physiological role of checkpoint pathways in regulating adaptive immunity and preventing autoimmunity. As immunotherapy becomes more common, a better understanding of the etiology of irAEs and ways to limit these events is needed. At the same time, studying these new therapy-related disorders provides an opportunity to better understand naturally occurring human autoimmune and inflammatory disorders, with the potential to improve therapies for cancer and autoimmune diseases.

Emerging Cellular Therapies for Cancer

Genetically engineered T cells are powerful new medicines, offering hope for curative responses in patients with cancer. Chimeric antigen receptor (CAR) T cells were recently approved by the US Food and Drug Administration and are poised to enter the practice of medicine for leukemia and lymphoma, demonstrating that engineered immune cells can serve as a powerful new class of cancer therapeutics. The emergence of synthetic biology approaches for cellular engineering provides a broadly expanded set of tools for programming immune cells for enhanced function. Advances in T cell engineering, genetic editing, the selection of optimal lymphocytes, and cell manufacturing have the potential to broaden T cell-based therapies and foster new applications beyond oncology, in infectious diseases, organ transplantation, and autoimmunity.

A safe and potent anti-CD19 CAR T cell therapy

Anti-CD19 chimeric antigen receptor (CAR) T cell therapies can cause severe cytokine-release syndrome (CRS) and neurotoxicity, impeding their therapeutic application. Here we generated a new anti-CD19 CAR molecule (CD19-BBz(86)) derived from the CD19-BBz prototype bearing co-stimulatory 4-1BB and CD3ζ domains. We found that CD19-BBz(86) CAR T cells produced lower levels of cytokines, expressed higher levels of antiapoptotic molecules and proliferated more slowly than the prototype CD19-BBz CAR T cells, although they retained potent cytolytic activity. We performed a phase 1 trial of CD19-BBz(86) CAR T cell therapy in patients with B cell lymphoma (ClinicalTrials.gov identifier NCT02842138 ). Complete remission occurred in 6 of 11 patients (54.5%) who each received a dose of 2 × 10⁸-4 × 10⁸ CD19-BBz(86) CAR T cells. Notably, no neurological toxicity or CRS (greater than grade 1) occurred in any of the 25 patients treated. No significant elevation in serum cytokine levels after CAR T cell infusion was detected in the patients treated, including in those who achieved complete remission. CD19-BBz(86) CAR T cells persistently proliferated and differentiated into memory cells in vivo. Thus, therapy with the new CD19-BBz(86) CAR T cells produces a potent and durable antilymphoma response without causing neurotoxicity or severe CRS, representing a safe and potent anti-CD19 CAR T cell therapy.

Quantitative Systems Pharmacology Model of Chimeric Antigen Receptor T-Cell Therapy

Chimeric antigen receptor T‐cell (CART) therapy is a new and promising cancer therapy. However, severe toxicity due to cytokine release syndrome (CRS) in CART‐treated patients highlighted the possible danger of this new therapy. Disease burden and CART doses are the potential factors associated with CRS but the detail relationships between these factors and the severity of the CRS remain largely unknown. In this study, the quantitative systems pharmacology (QSP) approach is used to quantify the complex relationships among CART doses, disease burden, and pro inflammatory cytokines in human subjects and to gain relevant insights into the determinant of clinical toxicity/efficacy in development of CART therapy. The expansion of CART and elimination of B cells are more highly correlated with disease burden than the administered CART doses. To our best knowledge, this is the first QSP model that can describe the observed clinical data from CART‐treated patients with cancer. This QSP model is a valuable tool for deepening our understanding of how the mechanism of action connects to the clinical outcomes and, therefore, may serve as an important model‐based platform to guide the development and personalized dosing of the CART therapy.

Recommendations for the management of hemophagocytic lymphohistiocytosis in adults

Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome induced by aberrantly activated macrophages and cytotoxic T cells. The primary (genetic) form, caused by mutations affecting lymphocyte cytotoxicity and immune regulation, is most common in children, whereas the secondary (acquired) form is most frequent in adults. Secondary HLH is commonly triggered by infections or malignancies but may also be induced by autoinflammatory/autoimmune disorders, in which case it is called macrophage activation syndrome (MAS; or MAS-HLH). Most information on the diagnosis and treatment of HLH comes from the pediatric literature. Although helpful in some adult cases, this raises several challenges. For example, the HLH-2004 diagnostic criteria developed for children are commonly applied but are not validated for adults. Another challenge in HLH diagnosis is that patients may present with a phenotype indistinguishable from sepsis or multiple organ dysfunction syndrome. Treatment algorithms targeting hyperinflammation are frequently based on pediatric protocols, such as HLH-94 and HLH-2004, which may result in overtreatment and unnecessary toxicity in adults. Therefore, dose reductions, individualized tailoring of treatment duration, and an age-dependent modified diagnostic approach are to be considered. Here, we present expert opinions derived from an interdisciplinary working group on adult HLH, sponsored by the Histiocyte Society, to facilitate knowledge transfer between physicians caring for pediatric and adult patients with HLH, with the aim to improve the outcome for adult patients affected by HLH.

CAR T Cell Immunotherapy in Human and Veterinary Oncology: Changing the Odds Against Hematological Malignancies

The advent of the genome editing era brings forth the promise of adoptive cell transfer using engineered chimeric antigen receptor (CAR) T cells for targeted cancer therapy. CAR T cell immunotherapy is probably one of the most encouraging developments for the treatment of hematological malignancies. In 2017, two CAR T cell therapies were approved by the US Food and Drug Administration: one for the treatment of pediatric acute lymphoblastic leukemia (ALL) and the other for adult patients with advanced lymphomas. However, despite significant progress in the area, CAR T cell therapy is still in its early days and faces significant challenges, including the complexity and costs associated with the technology. B cell lymphoma is the most common hematopoietic cancer in dogs, with an incidence approaching 0.1% and a total of 20-100 cases per 100,000 individuals. It is a widely accepted naturally occurring model for human non-Hodgkin's lymphoma. Current treatment is with combination chemotherapy protocols, which prolong life for less than a year in canines and are associated with severe dose-limiting side effects, such as gastrointestinal and bone marrow toxicity. To date, one canine study generated CAR T cells by transfection of mRNA for CAR domain expression. While this was shown to provide a transient anti-tumor activity, results were modest, indicating that stable, genomic integration of CAR modules is required in order to achieve lasting therapeutic benefit. This commentary summarizes the current state of knowledge on CAR T cell immunotherapy in human medicine and its potential applications in animal health, while discussing the potential of the canine model as a translational system for immuno-oncology research.

Fevers post infusion of T-cell replete hla mismatched haploidentical hematopoietic stem cells with post-transplant cyclophosphamide: risk factors and impact on transplant outcomes

Fever is a common early complication after infusion of stem cells in patients undergoing T-replete HLA haploidentical transplantation using post-transplant cyclophosphamide (PTCY). We analyzed the records of 172 haploidentical transplant patients to identify risk factors and to assess the impact of such fevers on transplant morbidity and mortality. One hundred and seventy-two patients received haploidential hematopoietic stem cell transplantation (haplo-HSCT) using PBSC (n = 103) or marrow (n = 69) grafts. One hundred and forty patients (81%) experienced fever (T ≥ 100.5 °F or >38 °C) with median onset on d + 2. Compared to patients who did not develop fevers, patients with fevers received higher median CD34+ cell dose (5.00 vs. 3.08 × 10⁶/kg, p < 0.001), CD3+ cell dose (12.8 vs. 4.5 × 10⁷/kg), were more likely to have received a myeloablative regimen (50% vs. 9%, p < 0.001), and PBSC source (71% vs. 9%, p < 0.001). Cox model showed that fever had no impact on TRM, GVHD, OS, and DFS. In the logistic regression to identify correlation with fevers, higher degree of HLA mismatches and use of PBSC were all predictors of developing fever. Fevers between infusion of the T-Cell replete graft and administration of PTCY are very common in Haplo-HSCT. This complication is transient and had no impact on post-transplant morbidity and mortality.

Chimeric antigen receptor T-cell toxicity

PURPOSE OF REVIEW

Chimeric antigen receptor -(CAR) T-cell therapy has become a commonly used immunotherapy originally used in the treatment of B-cell leukemias but which are now applied broadly across tumor classes. Although high rates of remission are associated with CAR T-cell therapy, toxicities associated with these novel treatment regimens can be lethal if not recognized in a timely manner.

RECENT FINDINGS

Cytokine release syndrome and neurotoxicity are the two most common toxicities associated with CAR T-cell therapy. Cytokine release syndrome is characterized by a flu-like illness accompanied by significant hemodynamic instability; treatments include administration of tocilizumab and corticosteroids. Neurotoxicity is associated with nonpattern-specific neurological changes and can rapidly progress to a comatose state from cerebral edema and death. Other potential toxicities from CAR T-cell therapy include tumor lysis syndrome, B-cell aplasia, graft versus host disease, and dermatological eruptions.

SUMMARY

Clinical awareness of CAR T-cell toxicities is important because prompt treatment leads to improved survival and remission rates.

In the Eye of the Storm: Immune-mediated Toxicities Associated With CAR-T Cell Therapy

The success of chimeric antigen receptor (CAR)-T cell therapy with impressive response rates in hematologic malignancies but also promising data in solid tumors came along with the cognition of unexpected, potentially life-threatening immune-mediated toxicities, namely the cytokine release syndrome (CRS) and neurotoxicity recently referred to as "immune effector cell-associated neurotoxicity syndrome" (ICANS). These toxicities require urgent diagnostic and therapeutic interventions and targeted modulation of key cytokine pathways represents the mainstay of CRS treatment. However, as the underlying mechanisms of ICANS are not well understood, treatment options remain limited and further investigation is warranted. Importantly, after the recent market approval of 2 CAR-T cell constructs, the application of CAR-T cells will expand to nonacademic centers with limited experience in the management of CAR-T cell-associated toxicities. Here, we review the current evidence of CRS and ICANS pathophysiology, diagnostics, and treatment.

CAR T Cell Toxicity: Current Management and Future Directions

By late 2018, 2 chimeric antigen receptor T (CAR T) cell products have been approved by US and European regulatory authorities. Tisagenlecleucel (Kymriah, Novartis) is indicated in the treatment of patients up to 25 years of age with B-cell acute lymphoblastic leukemia (ALL) that is refractory or in second or later relapse, or adult patients with large B-cell lymphoma relapsed or refractory (r/r) after 2 or more lines of systemic therapy, including diffuse large B-cell lymphoma (DLBCL) not otherwise specified, high grade B-cell lymphoma and DLBCL arising from follicular lymphoma. Axicabtagene ciloleucel (Yescarta, Kite) is indicated for the treatment of adult patients with large B-cell lymphoma relapsed or refractory after 2 or more lines of systemic therapy, including DLBCL not otherwise specified, primary mediastinal large B-cell lymphoma, high grade B-cell lymphoma, and DLBCL arising from follicular lymphoma (ZUMA-1 trial). This review will offer a practical guide for the recognition and management of the most important toxicities related to the use of the current commercial CAR T cells, and also highlight strategies to diminish these side effects in the future.

Cytokine release syndrome. Reviewing a new entity in the intensive care unit

Immunotherapy seeks to harness the power of the immune system to eradicate malignant tissues. Despite impressive therapeutic success, however, it can be accompanied by severe adverse effects such as cytokine release syndrome (CRS). These therapies cause the release of a great amount of cytokines, with IL-6 playing a central role, that can potentially lead to multiple organ dysfunction. The diagnosis is based on the presence of compatible clinical symptoms, elevated biomarkers and recent treatment with a biological agent. Mild cases can be managed through symptomatic treatment and fluids, while more severe episodes may need supportive therapy and specific care with the anti-IL-6 receptor monoclonal antibody tocilizumab. Although corticosteroids are also effective, they suppress T-cell activity, and so should only be considered as second line therapy or in cases of severe neurological involvement, since tocilizumab does not cross the blood-brain barrier. Cytokine release syndrome generally has a good prognosis, often being reversible and with a good response to specific treatment. Despite possible concerns about the admission of such patients (mainly with advanced oncological disease), we consider that the Intensive Care Unit should remain an option, since these individuals present a potentially reversible drug-related adverse event and are being treated with a new drug that could change the prognosis of the disorder. Intensive care medicine will become a key component in the management of the complications of modern cancer therapies, dealing with patients presenting an overactive immune system producing organ dysfunction while also trying to maintain treatment efficacy. This is the new paradigm.

B cell maturation antigen-specific CAR T cells are clinically active in multiple myeloma

BACKGROUND

Chimeric antigen receptor (CAR) T cells are a promising therapy for hematologic malignancies. B-cell maturation antigen (BCMA) is a rational target in multiple myeloma (MM).

METHODS

We conducted a phase I study of autologous T cells lentivirally-transduced with a fully-human, BCMA-specific CAR containing CD3ζ and 4-1BB signaling domains (CART-BCMA), in subjects with relapsed/refractory MM. Twenty-five subjects were treated in 3 cohorts: 1) 1-5 x 108 CART-BCMA cells alone; 2) Cyclophosphamide (Cy) 1.5 g/m2 + 1-5 x 107 CART-BCMA cells; and 3) Cy 1.5 g/m2 + 1-5 x 108 CART-BCMA cells. No pre-specified BCMA expression level was required.

RESULTS

CART-BCMA cells were manufactured and expanded in all subjects. Toxicities included cytokine release syndrome and neurotoxicity, which were grade 3-4 in 8 (32%) and 3 (12%) subjects, respectively, and reversible. One subject died at day 24 from candidemia and progressive myeloma, following treatment for severe CRS and encephalopathy. Responses (based on treated subjects) were seen in 4/9 (44%) in cohort 1, 1/5 (20%) in cohort 2, and 7/11 (64%) in cohort 3, including 5 partial, 5 very good partial, and 2 complete responses, 3 of which were ongoing at 11, 14, and 32 months. Decreased BCMA expression on residual MM cells was noted in responders; expression increased at progression in most. Responses and CART-BCMA expansion were associated with CD4:CD8 T cell ratio and frequency of CD45RO-CD27+CD8+ T cells in the pre-manufacturing leukapheresis product.

CONCLUSION

CART-BCMA infusions with or without lymphodepleting chemotherapy are clinically active in heavily-pretreated MM patients.

TRIAL REGISTRATION

NCT02546167.

FUNDING

University of Pennsylvania-Novartis Alliance and NIH.

Management of cytokine release syndrome and neurotoxicity in chimeric antigen receptor (CAR) T cell therapy

INTRODUCTION

Chimeric antigen receptor (CAR) T cell immunotherapy has demonstrated remarkable anti-tumor activity in B-cell malignancies and is under investigation in other hematologic malignancies and solid tumors. While highly efficacious, post-infusion T cell activity often results in massive cytokine release precipitating cytokine release syndrome (CRS), the signature toxicity of CAR T cells. This toxicity is characterized by systemic immune activation resulting in fever, hypotension, respiratory insufficiency and capillary leak. Either in conjunction with or in the absence of CRS, a subset of patients may also develop mild to severe neurotoxicity. Although the precise pathogenesis of CRS and neurotoxicity aren't fully elucidated, risk factors and mitigation strategies have been reported. Areas covered: This manuscript provides an in-depth overview of the pathogenesis, clinical characteristics, current toxicity management strategies, and future perspectives pertaining to CRS and neurotoxicity. Expert Opinion: As CAR T cell based therapies gain popularity in the management of various malignancies, the complimentary toxicities of CRS and neurotoxicity pose a clinical challenge in practice. Risk adaptive modeling incorporating disease profile, patient demographics, lymphodepletion, cell dosing, CAR T construct, and potentially cytokine gene polymorphisms may be instructive to assess individualized risk and optimal CRS/neurotoxicity management.

Current approaches in the grading and management of cytokine release syndrome after chimeric antigen receptor T-cell therapy

With immunotherapy innovations for cancer treatment, in particular chimeric antigen receptor (CAR) T cells, becoming more successful and prevalent, strategies to mitigate and manage their toxicities are required. Anti-CD19 CAR T-cell therapy has revolutionized the treatment of relapsed/refractory pediatric and adult acute lymphoblastic leukemia and refractory adult non-Hodgkin lymphoma, resulting in the expanded use of CAR T cells in multicenter trials and as US FDA-approved products. Cytokine release syndrome (CRS) and CAR-associated neurotoxicity, which can occur independently or concurrently with CRS, are two potentially life-threatening toxicities of CAR T-cell therapy. In this review, we will focus on describing the pathophysiology behind CRS, the proposed definitions of and grading systems for CRS, and innovative options for treating this potentially lethal systemic inflammatory condition.

Early and late hematologic toxicity following CD19 CAR-T cells

Autologous T cells transduced with CD19-directed chimeric antigen receptors have recently been approved by several regulatory agencies for the treatment of relapsed and refractory leukemia and lymphoma, after demonstrating remarkable remission rate in advanced patients. The most common adverse events reported are cytokine-release syndrome (CRS), neurotoxicity, and hematologic toxicity. Here, we focus on early and late cytopenia occurring after CD19 CAR-T cells in 38 patients treated with CD19 CAR-T cells. Neutropenia, thrombocytopenia, and anemia occur frequently (94, 80, and 51%, respectively) after CAR-T cell infusion, and are associated with a biphasic nature, as in 93% of patients hematologic toxicity occurs after 21 days from cell infusion. Late hematologic toxicity was more common in patients with high grade CRS and in patients treated after a recent stem cell transplantation. Interestingly, since these events occur late after the lymphodepleting chemotherapy and after resolution of CRS, we found perturbations in SDF-1 levels to correlate with events of late neutropenia, likely associated with B-cell recovery.

Outsmarting and outmuscling cancer cells with synthetic and systems immunology

Adoptive T-cell therapy has shown remarkable clinical efficacy in treating refractory hematological cancers. However, challenges presented by solid tumors impede the applicability of adoptive T-cell therapy to the majority of cancers. In order to engineer effective T-cell therapies targeting solid tumors, two synergistic design criteria-T-cell therapeutic programs and anti-tumor T-cell chassis-should be taken into consideration. Recent advances in synthetic biology have enabled genetic programming of therapeutic sense-and-respond modalities in T cells. Furthermore, systems-level integration of multi-omics datum have allowed researchers to holistically profile robust anti-tumor T-cell populations. In this review, we feature novel strategies that can be incorporated into adoptive T-cell therapy design-ushering in a new paradigm of solid tumor treatment options.

Granulocyte-macrophage colony-stimulating factor inactivation in CAR T-cells prevents monocyte-dependent release of key cytokine release syndrome mediators

Chimeric antigen receptor T-cell (CAR T-cell) therapy has been shown to be clinically effective for managing a variety of hematological cancers. However, CAR T-cell therapy is associated with multiple adverse effects, including neurotoxicity and cytokine release syndrome (CRS). CRS arises from massive cytokine secretion and can be life-threatening, but it is typically managed with an anti-IL-6Ra mAb or glucocorticoid administration. However, these treatments add to a patient's medication burden and address only the CRS symptoms. Therefore, alternative strategies that can prevent CRS and neurotoxicity associated with CAR T-cell treatment are urgently needed. Here, we explored a therapeutic route aimed at preventing CRS rather than limiting its consequences. Using a cytokine-profiling assay, we show that granulocyte-macrophage colony-stimulating factor (GMCSF) is a key CRS-promoting protein. Through a combination of in vitro experiments and gene-editing technology, we further demonstrate that antibody-mediated neutralization or TALEN-mediated genetic inactivation of GMCSF in CAR T-cells drastically decreases available GMCSF and abolishes macrophage-dependent secretion of CRS biomarkers, including monocyte chemoattractant protein 1 (MCP-1), interleukin (IL) 6, and IL-8. Of note, we also found that the genetic inactivation of GMCSF does not impair the antitumor function or proliferative capacity of CAR T-cells in vitro We conclude that it is possible to prevent CRS by using "all-in-one" GMCSF-knockout CAR T-cells. This approach may eliminate the need for anti-CRS treatment and may improve the overall safety of CAR T-cell therapies for cancer patients.

The response to lymphodepletion impacts PFS in patients with aggressive non-Hodgkin lymphoma treated with CD19 CAR T cells

Factors associated with durable remission after CD19 chimeric antigen receptor (CAR)-modified T-cell immunotherapy for aggressive B-cell non-Hodgkin lymphoma (NHL) have not been identified. We report multivariable analyses of factors affecting response and progression-free survival (PFS) in patients with aggressive NHL treated with cyclophosphamide and fludarabine lymphodepletion followed by 2 × 10⁶ CD19-directed CAR T cells/kg. The best overall response rate was 51%, with 40% of patients achieving complete remission. The median PFS of patients with aggressive NHL who achieved complete remission was 20.0 months (median follow-up, 26.9 months). Multivariable analysis of clinical and treatment characteristics, serum biomarkers, and CAR T-cell manufacturing and pharmacokinetic data showed that a lower pre-lymphodepletion serum lactate dehydrogenase (LDH) level and a favorable cytokine profile, defined as serum day 0 monocyte chemoattractant protein-1 (MCP-1) and peak interleukin-7 (IL-7) concentrations above the median, were associated with better PFS. MCP-1 and IL-7 concentrations increased after lymphodepletion, and higher intensity of cyclophosphamide and fludarabine lymphodepletion was associated with higher probability of a favorable cytokine profile. PFS was superior in patients who received high-intensity lymphodepletion and achieved a favorable cytokine profile compared with those who received the same intensity of lymphodepletion without achieving a favorable cytokine profile. Even in high-risk patients with pre-lymphodepletion serum LDH levels above normal, a favorable cytokine profile after lymphodepletion was associated with a low risk of a PFS event. Strategies to augment the cytokine response to lymphodepletion could be tested in future studies of CD19 CAR T-cell immunotherapy for aggressive B-cell NHL. This trial was registered at www.clinicaltrials.gov as #NCT01865617.

GM-CSF inhibition reduces cytokine release syndrome and neuroinflammation but enhances CAR-T cell function in xenografts

Chimeric antigen receptor T (CAR-T) cell therapy is a new pillar in cancer therapeutics; however, its application is limited by the associated toxicities. These include cytokine release syndrome (CRS) and neurotoxicity. Although the IL-6R antagonist tocilizumab is approved for treatment of CRS, there is no approved treatment of neurotoxicity associated with CD19-targeted CAR-T (CART19) cell therapy. Recent data suggest that monocytes and macrophages contribute to the development of CRS and neurotoxicity after CAR-T cell therapy. Therefore, we investigated neutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) as a potential strategy to manage CART19 cell–associated toxicities. In this study, we show that GM-CSF neutralization with lenzilumab does not inhibit CART19 cell function in vitro or in vivo. Moreover, CART19 cell proliferation was enhanced and durable control of leukemic disease was maintained better in patient-derived xenografts after GM-CSF neutralization with lenzilumab. In a patient acute lymphoblastic leukemia xenograft model of CRS and neuroinflammation (NI), GM-CSF neutralization resulted in a reduction of myeloid and T cell infiltration in the central nervous system and a significant reduction in NI and prevention of CRS. Finally, we generated GM-CSF–deficient CART19 cells through CRISPR/Cas9 disruption of GM-CSF during CAR-T cell manufacturing. These GM-CSFk/o CAR-T cells maintained normal functions and had enhanced antitumor activity in vivo, as well as improved overall survival, compared with CART19 cells. Together, these studies illuminate a novel approach to abrogate NI and CRS through GM-CSF neutralization, which may potentially enhance CAR-T cell function. Phase 2 studies with lenzilumab in combination with CART19 cell therapy are planned.

Purification of mRNA Encoding Chimeric Antigen Receptor Is Critical for Generation of a Robust T-Cell Response

T cells made with messenger RNA (mRNA) encoding chimeric antigen receptor (CAR) offer a safe alternative to those transduced with viral CARs by mitigating the side effects of constitutively active T cells. Previous studies have shown that mRNA CAR T cells are transiently effective but lack persistence and potency across tumor types. It was hypothesized that the efficacy of mRNA CARs could be improved by utilizing recent advancements in RNA technology, such as incorporating a modified nucleoside, 1-methylpseudouridine, into the mRNA and applying a novel purification method using RNase III to eliminate dsRNA contaminants. T cells electroporated with nucleoside-modified and purified mRNA encoding CD19 CAR showed an initial twofold increase in CAR surface expression, as well as a twofold improvement in cytotoxic killing of leukemia cells that persisted up to 5 days. T cells generated with nucleoside-modified and purified CAR mRNA also showed reduced expression of checkpoint regulators and a differential pattern of genetic activation compared to those made with conventional mRNA. In vivo studies using a leukemia mouse model revealed that the most robust 100-fold suppression of leukemic burden was achieved using T cells electroporated with purified mRNAs, regardless of their nucleoside modification. The results provide a novel approach to generate mRNA for clinical trials, and poise mRNA CAR T cells for increased efficacy during testing as new CAR targets emerge.

Chimeric Antigen Receptor T Cells: A Race to Revolutionize Cancer Therapy

For years, cancer treatment was dominated by chemotherapy, radiation therapy, and stem cell transplantation. New insights into genetic characteristics of leukemic cells have initiated the development of the chimeric antigen receptor (CAR) T-cell therapy. This type of adoptive cell immunotherapy has been a breakthrough in the treatment of aggressive B-cell lymphoma and B-cell precursor acute lymphoblastic leukemia. In August 2018, the European Commission has approved the first CAR T-cell products - tisagenlecleucel (Kymriah®, Novartis) and axicabtagene ciloleucel (Yescarta®, Gilead) - for hematological neoplasms in Europe. As CAR T cells are a living drug, its benefits can last for many years. The administration of CAR T cells is a complex and costly endeavor involving cell manufacture, shipping of apheresis products, and management of novel and severe adverse reactions. The most common toxicities observed after CAR T-cell therapy are cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. Current research focuses on improved safety and efficacy in hematological malignancies as well as the translation of CAR T-cell therapy to solid tumors. This review covers the development and current status of CAR T-cell therapy in a clinical setting with focus on challenges and future opportunities.

Mechanisms and Management of Chimeric Antigen Receptor T-Cell Therapy-Related Toxicities

Chimeric antigen receptor T-cell (CAR-T) therapy has proven to be a very effective cancer immunotherapy. Axicabtagene ciloleucel and tisagenlecleucel are the first-in-class anti-CD19 CAR-T currently available for relapsed/refractory adult large B-cell lymphoma. Tisagenlecleucel is also available for pediatric and young adult (up to age 25 years) patients with relapsed/refractory B-acute lymphoblastic leukemia. Cytokine release syndrome (CRS) and CAR-T-associated encephalopathy syndrome (neurotoxicity) are the most common adverse effects associated with CAR-T therapy. They can lead to significant morbidity and preclude widespread use of this treatment modality. Treatment-related deaths from severe CRS and cerebral edema have been reported. There is a significant heterogeneity in the side-effect profile of different CAR-T products under investigation and there is a need to develop standardized guidelines for toxicity grading and management. Here, we summarize the current literature on pathogenesis, clinical presentation, and management of CRS and neurotoxicity. The different grading systems of CRS and management protocols used in different trials have made it difficult to compare the outcomes of different CAR-T therapies. Several prevention strategies such as predictive biomarkers of CRS and neurotoxicity and modified CAR-T with 'built-in' safety mechanisms are being studied, with the potential to greatly expand the safety and applicability of CAR-T treatment across various malignancies.

Gestion des toxicités des lymphocytes T exprimant un récepteur à l’antigène chimérique (CAR-T cells)

TOXICITY MANAGEMENT OF CHIMERIC ANTIGEN RECEPTOR T-CELLS

Chimeric antigen receptor T-cells (CAR T-cells) represent a very promising treatment for both hematological malignancies and solid tumors. Many clinical trials are currently on-going to establish the role of this emerging therapy. The toxicities observed after CAR T-cells infusion are mostly represented by a cytokine release syndrome and neurological symptoms. Athough reversible, these adverse events remain associated with morbidity and mortality in patients. The objective of this review is to describe these adverse events, also discussing their physiopathology and management, based on the recent recommendations published by the CARTOX working group (CAR T-cell-therapy-associated TOXicity working group) in the US. Cet article fait partie du numéro supplément Les cellules CAR-T : une révolution thérapeutique ? réalisé avec le soutien institutionnel des partenaires Gilead : Kite et Celgene.

Unleash the power of the mighty T cells-basis of adoptive cellular therapy

Adoptive cellular therapy (ACT) is an immunotherapy which involves the passive transfer of lymphocytes into a lymphodepleted host after ex vivo stimulation and expansion. Tumor-infiltrating lymphocytes (TILs) have shown objective tumor responses mainly restricted to melanoma and rely on a laborious manufacturing process. These limitations led to emergence of engineered cells, where normal peripheral blood lymphocytes are modified to express T cell receptors (TCRs) or chimeric antigen receptors (CARs) specific for tumor-associated antigens (TAAs). To date, CD19-targeted chimeric antigen receptor T (CAR T) cells have been the most extensively studied, showing complete and durable responses in B-cell malignancies. Antitumor responses with engineered T cells have often been accompanied by undesired toxicities in clinical trials including cytokine release syndrome (CRS) and neurotoxicity. In this review, we provide an overview of adoptive cellular strategies, early and ongoing clinical trials, adverse events and strategies to mitigate side effects and overcome limitations.