Cytokine Release Syndrome After Chimeric Antigen Receptor T Cell Therapy for Acute Lymphoblastic Leukemia

Immunotherapy Using Chimeric Antigen Receptor-Engineered T Cells: A Novel Cellular Therapy with Important Implications for the Clinical Laboratory

BACKGROUND

We have entered a new era of cancer therapy, with a number of immune-based therapies already used clinically as a standard of care. Adoptive cellular immunotherapy using T cells genetically modified with chimeric antigen receptors (CAR-T cells) represents a novel therapeutic approach. CAR-T cells have produced clinical responses in B-cell malignancies that are otherwise refractory to conventional therapies. Two CAR-T cell therapies obtained regulatory approval in 2017, with many more of these therapies under clinical development.

CONTENT

This review focuses on the current state of adoptive cellular immunotherapy, specifically CAR-T cells, in the clinic and how this therapy differs from traditional small molecule and biologic therapies. Areas in which the clinical laboratory is affected by these novel therapies are discussed. Opportunities for the clinical laboratory to help guide these therapies are also highlighted.

SUMMARY

The clinical laboratory will play an integral role in the care of patients undergoing adoptive cellular therapy with engineered T cells. There are many ways that this new therapeutic approach affects the clinical laboratory, and the clinical laboratory will likely play a critical role in managing patients that are treated with CAR-T cell therapy.

Off-label use of tocilizumab to treat non-juvenile idiopathic arthritis in pediatric rheumatic patients: a literature review

Tocilizumab, an anti-interleukin-6 (IL-6) agent, is indicated as a treatment for several autoimmune or inflammatory diseases, including rheumatoid arthritis and juvenile idiopathic arthritis (JIA). IL-6 plays roles in both immune system dysregulation and inflammation, and thus efforts to extend the utility of tocilizumab in patients with autoinflammatory conditions are ongoing. Here, we survey the literature on the off-label use of tocilizumab in patients with juvenile-onset rheumatic diseases including juvenile systemic lupus erythematosus (SLE), juvenile dermatomyositis (DM), vasculitis, juvenile scleroderma, and other autoinflammatory diseases. There is no real evidence that tocilizumab is useful for patients with SLE and juvenile DM, but several cases of childhood Takayasu arteritis have experienced promising outcomes. In juvenile-onset scleroderma, for which no therapy that can halt disease progression is available, tocilizumab may stop progression and the associated functional impairment. Tocilizumab prevents systemic inflammation in patients with Kawasaki's disease, but may develop coronary aneurysms. Tocilizumab has been used to treat several pediatric autoinflammatory diseases, including JIA-associated uveitis and Castleman's disease. Further work in larger populations is necessary to confirm the effects of tocilizumab in patients with pediatric rheumatic diseases.

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-CSF^k/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.

The adverse kidney effects of cancer immunotherapies

Cancer therapies are a common cause of acute and chronic kidney disease, which are increasingly being seen by nephrologists in clinical practice. Conventional chemotherapeutic drugs and novel targeted agents are effective cancer therapies but their use is complicated by nephrotoxicity. Cancer immunotherapies exploit various properties of immune cells to enhance immune-mediated tumor killing. Interferon and high-dose interleukin-2 are older immunotherapies first employed clinically in the 1980s and 1990s to treat a number of different cancers. While effective, these two therapies have well-known systemic toxicities, which include acute kidney disease. The emergence of the new cancer immunotherapies over the past decade brings more effective treatment options. The immune checkpoint inhibitors and chimeric antigen receptor T cells are exciting additions to the cancer treatment armamentarium. These agents effectively treat a several and a growing list of cancers that have otherwise failed other therapies. However, as with the conventional and targeted cancer agents, drug-induced acute and chronic kidney disease is an untoward effect of this group of drugs. We will undertake a case-based review: the newer immunotherapies followed by the older therapies, interferon and interleukin-2.

Recent advances in CAR T-cell toxicity: Mechanisms, manifestations and management

Chimeric antigen receptor (CAR) T-cell therapy is an effective new treatment for hematologic malignancies. Two CAR T-cell products are now approved for clinical use by the U.S. FDA: tisagenlecleucel for pediatric acute lymphoblastic leukemia (ALL) and adult diffuse large B-cell lymphoma subtypes (DLBCL), and axicabtagene ciloleucel for DLBCL. CAR T-cell therapies are being developed for multiple myeloma, and clear evidence of clinical activity has been generated. A barrier to widespread use of CAR T-cell therapy is toxicity, primarily cytokine release syndrome (CRS) and neurologic toxicity. Manifestations of CRS include fevers, hypotension, hypoxia, end organ dysfunction, cytopenias, coagulopathy, and hemophagocytic lymphohistiocytosis. Neurologic toxicities are diverse and include encephalopathy, cognitive defects, dysphasias, seizures, and cerebral edema. Our understanding of the pathophysiology of CRS and neurotoxicity is continually improving. Early and peak levels of certain cytokines, peak blood CAR T-cell levels, patient disease burden, conditioning chemotherapy, CAR T-cell dose, endothelial activation, and CAR design are all factors that may influence toxicity. Multiple grading systems for CAR T-cell toxicity are in use; a universal grading system is needed so that CAR T-cell products can be compared across studies. Guidelines for toxicity management vary among centers, but typically include supportive care, plus immunosuppression with tocilizumab or corticosteroids administered for severe toxicity. Gaining a better understanding of CAR T-cell toxicities and developing new therapies for these toxicities are active areas of laboratory research. Further clinical investigation of CAR T-cell toxicity is also needed. In this review, we present guidelines for management of CRS and CAR neurotoxicity.

The Two-Faced Cytokine IL-6 in Host Defense and Diseases

Interleukein-6 (IL-6), is produced locally from infectious or injured lesions and is delivered to the whole body via the blood stream, promptly activating the host defense system to perform diverse functions. However, excessive or sustained production of IL-6 is involved in various diseases. In diseases, the IL-6 inhibitory strategy begins with the development of the anti-IL-6 receptor antibody, tocilizumab (TCZ). This antibody has shown remarkable effects on Castleman disease, rheumatoid arthritis and juvenile idiopathic arthritis. In 2017, TCZ was proven to work effectively against giant cell arteritis, Takayasu arteritis and cytokine releasing syndrome, initiating a new era for the treatment of these diseases. In this study, the defensive functions of IL-6 and various pathological conditions are compared. Further, the diseases of which TCZ has been approved for treatment are summarized, the updated results of increasing off-label use of TCZ for various diseases are reviewed and the conditions for which IL-6 inhibition might have a beneficial role are discussed. Given the involvement of IL-6 in many pathologies, the diseases that can be improved by IL-6 inhibition will expand. However, the important role of IL-6 in host defense should always be kept in mind in clinical practice.

Oncologic Emergencies-The Old, the New, and the Deadly

Cancer continues to be a leading cause of death despite a broader understanding of its biology and the development of novel therapies. Nonetheless, with an increasing survival of this population, intensivists must be aware of the associated emergencies, both old and new. Oncologic emergencies can be seen as an initial presentation of the disease or precipitated by its treatment. In this review, we present key oncologic emergencies that may be encountered in daily practice, complications associated with innovative therapies, and treatment-related adverse events.

Cytokine release syndrome and neurotoxicity after CD19 chimeric antigen receptor-modified (CAR-) T cell therapy

Chimeric antigen receptor-modified (CAR)-T cells have demonstrated impressive results in the treatment of haematological malignancies. However, cytokine release syndrome (CRS) and neurotoxicity are common toxicities which are potentially life-threatening in severe cases. Risk factors for CRS and neurotoxicity identified so far include disease burden, lymphodepletion intensity and CAR-T cell dose administered. Risk-adapted dosing, with lower CAR-T cell doses administered to B-cell acute lymphoblastic leukaemia patients with high marrow blast counts, has been successful at decreasing severe CRS rates in this population. Intervention with therapies, such as tocilizumab and corticosteroids, have been effective at ameliorating toxicity, enabling CAR-T cells to be administered safely to many patients without significantly compromising efficacy. Deeper understanding of the pathophysiology of underlying CRS and neurotoxicity will enable the development of novel approaches to reduce toxicity and improve outcomes.

American Society for Blood and Marrow Transplantation Pharmacy Special Interest Group Survey on Chimeric Antigen Receptor T Cell Therapy Administrative, Logistic, and Toxicity Management Practices in the United States

Administration of immune effector cell (IEC) therapy is a complex endeavor requiring extensive coordination and communication of various healthcare and administrative teams. Chimeric antigen receptor (CAR) T cells are the most established IEC therapy available. As of July 2018 two commercial gene therapy products, tisagenlecleucel and axicabtagene ciloleucel, have been approved by the US Food and Drug Administration. To gain insight into the infrastructure and practices across the country, the American Society for Blood and Marrow Transplantation Pharmacy Special Interest Group conducted an electronic survey on the current administrative, logistic, and toxicity management practices of CAR T cell therapy across the United States. This survey consists of 52 responses from institutions of varying sizes, most of which (∼80%) had previous investigational experience with CAR T cell therapy. Absorbing the energy of this exciting new treatment has challenged hematopoietic cell transplant programs across the country to strengthen department infrastructure, develop new committees and policies, and implement significant education to ensure safe administration. With the variety of experience with CAR T cell therapy, we hope this survey can contribute to the existing published literature and provide support and consensus to established and developing IEC programs and practice guidelines.

Chimeric antigen receptor modified T-cells for cancer treatment

T cells engineered with the chimeric antigen receptor (CAR) are rapidly emerging as an important immunotherapy for hematologic malignancies. The anti-cluster of differentiation (CD)19 CAR-T cell therapy has been remarkably successful against refractory/relapsed acute lymphoblastic leukemia (ALL), and a complete remission rate as high as 90% was observed, in both children and adults. Although the achievement of clinical efficacy using CAR-T cell therapy for solid tumors has encountered several obstacles that were associated with the multiple mechanisms contributing to an immunosuppressive microenvironment, investigators are exploring more optimized approaches to improve the efficiency of CAR-T in solid tumors. In addition, cytokine release syndrome (CRS) and neurotoxicity following CAR-T cell therapy can be severe or even fatal; therefore, the management of these toxicities is significant. Herein, we briefly review the structure of CAR-T and some novel CAR designs, the clinical application of CAR-T cell therapies, as well as the assessment and management of toxicities.

The biological basis and clinical symptoms of CAR-T therapy-associated toxicites

Currently, immunotherapy is attracting a lot of attention and may potentially become a leading approach in the treatment of cancer. One emerging therapeutic, the chimeric-antigen receptor T-cell adoptive immunotherapy (CAR-T) is showing remarkable efficacy in the treatment of several B-cell malignancies. The popularity of CAR-T has been founded on two CAR T-cell products recently approved by FDA (during 2017) in the treatment of relapsed/refractory B-cell acute lymphoblastic leukemia and B-cell lymphoma. However, their toxicities observed in clinical trials were extremely significant and in some cases even fatal with no approved algorithms for toxicity prediction being available to date. A deeper understanding of the biological basis of such complications is the key to prompt and comprehensive clinical management. Here we review the wide spectrum of effects associated with CAR T cell therapy with a major focus on the pathogenesis of cytokine release syndrome and neurotoxicity as the most common, potentially life-threatening effects of this treatment. We discuss the basis of clinical management and the existing models that predict the severity of toxicity, as well as the key factors that modulate this event. Finally, we will summarize the literature detailing universal allogenic CAR T-cells and their toxicity profile.

The potential of CAR T therapy for relapsed or refractory pediatric and young adult B-cell ALL

Recent advancements in immunooncology have resulted in the generation of novel therapies such as chimeric antigen receptor (CAR) T cells, which have revolutionized the treatment of pediatric patients with relapsed or refractory B-cell acute lymphoblastic leukemia. The journey of tisagenlecleucel (formerly CTL019) from early preclinical success to the US Food and Drug Administration approval is summarized in this review. Strategies that are currently being investigated to improve the efficacy and safety profile of CAR T-cells are also explored, as well as the factors contributing to the present state of patient access to CAR T therapy.

The chimeric TAC receptor co-opts the T cell receptor yielding robust anti-tumor activity without toxicity

Engineering T cells with chimeric antigen receptors (CARs) is an effective method for directing T cells to attack tumors, but may cause adverse side effects such as the potentially lethal cytokine release syndrome. Here the authors show that the T cell antigen coupler (TAC), a chimeric receptor that co-opts the endogenous TCR, induces more efficient anti-tumor responses and reduced toxicity when compared with past-generation CARs. TAC-engineered T cells induce robust and antigen-specific cytokine production and cytotoxicity in vitro, and strong anti-tumor activity in a variety of xenograft models including solid and liquid tumors. In a solid tumor model, TAC-T cells outperform CD28-based CAR-T cells with increased anti-tumor efficacy, reduced toxicity, and faster tumor infiltration. Intratumoral TAC-T cells are enriched for Ki-67+ CD8+ T cells, demonstrating local expansion. These results indicate that TAC-T cells may have a superior therapeutic index relative to CAR-T cells.

Nephrotoxicity of Cancer Immunotherapies: Past, Present and Future

Nephrotoxicity from cancer therapies is common and increasingly encountered in clinical practice, such that the subfield of "onco-nephrology" has emerged. Conventional chemotherapeutic drugs and novel agents targeting specific genes/proteins are effective cancer therapies but suffer from a number of adverse kidney effects. An effective avenue of cancer treatment is immunotherapy, which uses drugs that augment immune system-mediated recognition and targeting of tumor cells. As such, leveraging the immune system to target malignant cells represents an important modality in eradicating cancer. IFN and high-dose IL-2 are older immunotherapies used in clinical practice to treat various malignancies, whereas new cancer immunotherapies have emerged over the past decade that offer even more effective treatment options. The immune checkpoint inhibitors are an exciting addition to the cancer immunotherapy armamentarium. Chimeric antigen receptor T cells are also a new immunotherapy used to treat various hematologic malignancies. However, as with the conventional and targeted cancer agents, the immunotherapies are also associated with immune-related adverse effects, which includes nephrotoxicity.

Cytokine release syndrome

During the last decade the field of cancer immunotherapy has witnessed impressive progress. Highly effective immunotherapies such as immune checkpoint inhibition, and T-cell engaging therapies like bispecific T-cell engaging (BiTE) single-chain antibody constructs and chimeric antigen receptor (CAR) T cells have shown remarkable efficacy in clinical trials and some of these agents have already received regulatory approval. However, along with growing experience in the clinical application of these potent immunotherapeutic agents comes the increasing awareness of their inherent and potentially fatal adverse effects, most notably the cytokine release syndrome (CRS). This review provides a comprehensive overview of the mechanisms underlying CRS pathophysiology, risk factors, clinical presentation, differential diagnoses, and prognostic factors. In addition, based on the current evidence we give practical guidance to the management of the cytokine release syndrome.

Cytokine release syndrome

During the last decade the field of cancer immunotherapy has witnessed impressive progress. Highly effective immunotherapies such as immune checkpoint inhibition, and T-cell engaging therapies like bispecific T-cell engaging (BiTE) single-chain antibody constructs and chimeric antigen receptor (CAR) T cells have shown remarkable efficacy in clinical trials and some of these agents have already received regulatory approval. However, along with growing experience in the clinical application of these potent immunotherapeutic agents comes the increasing awareness of their inherent and potentially fatal adverse effects, most notably the cytokine release syndrome (CRS). This review provides a comprehensive overview of the mechanisms underlying CRS pathophysiology, risk factors, clinical presentation, differential diagnoses, and prognostic factors. In addition, based on the current evidence we give practical guidance to the management of the cytokine release syndrome.

Human CD19-Targeted Mouse T Cells Induce B Cell Aplasia and Toxicity in Human CD19 Transgenic Mice

The clinical success of chimeric antigen receptor (CAR) T cell therapy for CD19+ B cell malignancies can be limited by acute toxicities and immunoglobulin replacement needs due to B cell aplasia from persistent CAR T cells. Life-threatening complications include cytokine release syndrome and neurologic adverse events, the exact etiologies of which are unclear. To elucidate the underlying toxicity mechanisms and test potentially safer CAR T cells, we developed a mouse model in which human CD19 (hCD19)-specific mouse CAR T cells were adoptively transferred into mice whose normal B cells express a hCD19 transgene at hemizygous levels. Compared to homozygous hCD19 transgenic mice that have ∼75% fewer circulating B cells, hemizygous mice had hCD19 frequencies and antigen density more closely simulating human B cells. Hemizygous mice given a lethal dose of hCD19 transgene-expressing lymphoma cells and treated with CAR T cells had undetectable tumor levels. Recipients experienced B cell aplasia and antigen- and dose-dependent acute toxicities mirroring patient complications. Interleukin-6 (IL-6), interferon γ (IFN-γ), and inflammatory pathway transcripts were enriched in affected tissues. As in patients, antibody-mediated neutralization of IL-6 (and IFN-γ) blunted toxicity. Apparent behavioral abnormalities associated with decreased microglial cells point to CAR-T-cell-induced neurotoxicity. This model will prove useful in testing strategies designed to improve hCD19-specific CAR T cell safety.

Clinical development of CAR T cells-challenges and opportunities in translating innovative treatment concepts

Chimeric antigen receptor (CAR) T cell therapy, together with checkpoint inhibition, has been celebrated as a breakthrough technology due to the substantial benefit observed in clinical trials with patients suffering from relapsed or refractory B‐cell malignancies. In this review, we provide a comprehensive overview of the clinical trials performed so far worldwide and analyze parameters such as targeted antigen and indication, CAR molecular design, CAR T cell manufacturing, anti‐tumor activities, and related toxicities. More than 200 CAR T cell clinical trials have been initiated so far, most of which aim to treat lymphoma or leukemia patients using CD19‐specific CARs. An increasing number of studies address solid tumors as well. Notably, not all clinical trials conducted so far have shown promising results. Indeed, in a few patients CAR T cell therapy resulted in severe adverse events with fatal outcome. Of note, less than 10% of the ongoing CAR T cell clinical trials are performed in Europe. Taking lead from our analysis, we discuss the problems and general hurdles preventing efficient clinical development of CAR T cells as well as opportunities, with a special focus on the European stage.

Dominant-Negative TGF-β Receptor Enhances PSMA-Targeted Human CAR T Cell Proliferation And Augments Prostate Cancer Eradication

Cancer has an impressive ability to evolve multiple processes to evade therapies. While immunotherapies and vaccines have shown great promise, particularly in certain solid tumors such as prostate cancer, they have been met with resistance from tumors that use a multitude of mechanisms of immunosuppression to limit effectiveness. Prostate cancer, in particular, secretes transforming growth factor β (TGF-β) as a means to inhibit immunity while allowing for cancer progression. Blocking TGF-β signaling in T cells increases their ability to infiltrate, proliferate, and mediate antitumor responses in prostate cancer models. We tested whether the potency of chimeric antigen receptor (CAR) T cells directed to prostate-specific membrane antigen (PSMA) could be enhanced by the co-expression of a dominant-negative TGF-βRII (dnTGF-βRII). Upon expression of the dominant-negative TGF-βRII in CAR T cells, we observed increased proliferation of these lymphocytes, enhanced cytokine secretion, resistance to exhaustion, long-term in vivo persistence, and the induction of tumor eradication in aggressive human prostate cancer mouse models. Based on our observations, we initiated a phase I clinical trial to assess these CAR T cells as a novel approach for patients with relapsed and refractory metastatic prostate cancer (ClinicalTrials.gov: NCT03089203).

Immunotherapy with CAR-Modified T Cells: Toxicities and Overcoming Strategies

T cells modified via chimeric antigen receptors (CARs) have emerged as a promising treatment modality. Unparalleled clinical efficacy recently demonstrated in refractory B-cell malignancy has brought this new form of adoptive immunotherapy to the center stage. Nonetheless, its current success has also highlighted its potential treatment-related toxicities. The adverse events observed in the clinical trials are described in this review, after which, some innovative strategies developed to overcome these unwanted toxicities are outlined, including suicide genes, targeted activation, and other novel strategies.

FDA Approval Summary: Tocilizumab for Treatment of Chimeric Antigen Receptor T Cell-Induced Severe or Life-Threatening Cytokine Release Syndrome

This article summarizes key review findings that supported the approval of tocilizumab for treatment of severe or life‐threatening CAR T cell‐induced cytokine release syndrome.

On August 30, 2017, the U.S. Food and Drug Administration approved Actemra (tocilizumab, Genentech, Inc., South San Francisco, CA) for the treatment of severe or life‐threatening chimeric antigen receptor (CAR) T cell‐induced cytokine release syndrome (CRS) in adults and in pediatric patients 2 years of age and older. The approval was based on a retrospective analysis of data for patients who developed CRS after treatment with CTL019 and KTE‐C19 on prospective clinical trials. Evaluable patients had been treated with intravenous tocilizumab 8 mg/kg (12 mg/kg for patients <30 kg) for severe or life‐threatening CRS; only the first episode of CRS was included in the analysis. The efficacy population for the CTL019 cohort included 24 male and 21 female patients (total 45 patients) of median age 12 years. The median time from the start of CRS to the first dose of tocilizumab was 4 days (range, 0–18 days). Patients were considered responders if CRS resolved within 14 days of the first dose of tocilizumab, if no more than 2 doses of tocilizumab were needed, and if no drugs other than tocilizumab and corticosteroids were used for treatment. Thirty‐one patients (69%; 95% confidence interval, 53%–82%) achieved a response as defined. In an independent cohort of 15 patients with KTE‐C19‐induced CRS, 53% responded. Further study is needed to determine the optimal dose of tocilizumab and to confirm the safety of its use for treatment of patients with CAR T cell‐induced CRS.

Implications for Practice.

Severe or life‐threatening chimeric antigen receptor (CAR) T cell‐induced cytokine release syndrome (CRS) requires urgent treatment to prevent fatal outcomes. In two independent cohorts, the majority of patients with severe or life‐threatening CAR T cell‐induced CRS responded to treatment with one or two doses of tocilizumab in addition to advanced supportive care. More research is needed to determine the optimal dose and schedule of tocilizumab for treatment of CAR T cell‐induced CRS.

Genetically enhanced T lymphocytes and the intensive care unit

Chimeric antigen receptor-modified T cells (CAR-T cells) and donor lymphocyte infusion (DLI) are important protocols in lymphocyte engineering. CAR-T cells have emerged as a new modality for cancer immunotherapy due to their potential efficacy against hematological malignancies. These genetically modified receptors contain an antigen-binding moiety, a hinge region, a transmembrane domain, and an intracellular costimulatory domain resulting in lymphocyte T cell activation subsequent to antigen binding. In present-day medicine, four generations of CAR-T cells are described depending on the intracellular signaling domain number of T cell receptors. DLI represents a form of adoptive therapy used after hematopoietic stem cell transplant for its anti-tumor and anti-infectious properties. This article covers the current status of CAR-T cells and DLI research in the intensive care unit (ICU) patient, including the efficacy, toxicity, side effects and treatment.

The Pharmacology of T Cell Therapies

Adoptive cellular therapy using T cells with tumor specificity derived from either natural T cell receptors (TCRs) or an artificial chimeric antigen receptor (CAR) has reached late phase clinical testing, with two CAR T cell therapies achieving regulatory approval within the United States in 2017. The effective use of these therapies depends upon an understanding of their pharmacology, which is quite divergent from traditional small molecule or biologic drugs. We review the different types of T cell therapy under clinical development, the factors affecting cellular kinetics following infusion, and the relationship between these cellular kinetics and anti-cancer activity. We also discuss the toxicity associated with T cell therapies, with an emphasis on cytokine release syndrome and neurotoxicity, and the gaps in knowledge regarding these frequent and unique adverse effects.

Grading of cytokine release syndrome associated with the CAR T cell therapy tisagenlecleucel

BACKGROUND

Anti-CD19 CAR T cell therapy has demonstrated high response rates in patients with relapsed or refractory (r/r) B cell malignancies but is associated with significant toxicity. Cytokine release syndrome (CRS) is the most significant complication associated with CAR T cell therapy, and it is critical to have a reproducible and easy method to grade CRS after CAR T cell infusions.

DISCUSSION

The Common Terminology Criteria for Adverse Events scale is inadequate for grading CRS associated with cellular therapy. Clinical experience with the anti-CD19 CAR T cell therapy tisagenlecleucel at the University of Pennsylvania (Penn) was used to develop the Penn grading scale for CRS. The Penn grading scale depends on easily accessible clinical features; does not rely on location of care or quantitation of supportive care; assigns grades to guide CRS management; distinguishes between mild, moderate, severe, and life-threatening CRS; and applies to both early-onset and delayed-onset CRS associated with T cell therapies. Clinical data from 55 pediatric patients with r/r B cell acute lymphoblastic leukemia and 42 patients with r/r chronic lymphocytic lymphoma treated with tisagenlecleucel were used to demonstrate the current application of the Penn grading scale.

CONCLUSION

We show that the Penn grading scale provides reproducible CRS grading that can be useful to guide therapy and that can be applied across clinical trials and treatment platforms.

Chimeric Antigen Receptor T-Cells for the Treatment of B-Cell Acute Lymphoblastic Leukemia

Chimeric antigen receptor (CAR) T-cell technology has seen a rapid development over the last decade mostly due to the potential that these cells may have in treating malignant diseases. It is a generally accepted principle that very few therapeutic compounds deliver a clinical response without treatment-related toxicity, and studies have shown that CAR T-cells are not an exception to this rule. While large multinational drug companies are currently investigating the potential role of CAR T-cells in hematological oncology, the potential of such cellular therapies are being recognized worldwide as they are expected to expand in the patient to support the establishment of the immune memory, provide a continuous surveillance to prevent and/or treat a relapse, and keep the targeted malignant cell subpopulation in check. In this article, we present the possible advantages of using CAR T-cells in treating acute lymphoblastic leukemia, presenting the technology and the current knowledge in their preclinical and early clinical trial use. Thus, this article first presents the main present-day knowledge on the standard of care for acute lymphoblastic leukemia. Afterward, current knowledge is presented about the use of CAR T-cells in cancer immunotherapy, describing their design, the molecular constructs, and the preclinical data on murine models to properly explain the background for their clinical use. Last, but certainly not least, this article presents the use of CAR T-cells for the immunotherapy of B-cell acute lymphoblastic leukemia, describing both their potential clinical advantages and the possible side effects.

Chimeric Antigen Receptor Expressing Natural Killer Cells for the Immunotherapy of Cancer

Adoptive cell therapy has emerged as a powerful treatment for advanced cancers resistant to conventional agents. Most notable are the remarkable responses seen in patients receiving autologous CD19-redirected chimeric antigen receptor (CAR) T cells for the treatment of B lymphoid malignancies; however, the generation of autologous products for each patient is logistically cumbersome and has restricted widespread clinical use. A banked allogeneic product has the potential to overcome these limitations, yet allogeneic T-cells (even if human leukocyte antigen-matched) carry a major risk of graft-versus-host disease (GVHD). Natural killer (NK) cells are bone marrow-derived innate lymphocytes that can eliminate tumors directly, with their activity governed by the integration of signals from activating and inhibitory receptors and from cytokines including IL-15, IL-12, and IL-18. NK cells do not cause GVHD or other alloimmune or autoimmune toxicities and thus, can provide a potential source of allogeneic “off-the-shelf” cellular therapy, mediating major anti-tumor effects without inducing potentially lethal alloreactivity such as GVHD. Given the multiple unique advantages of NK cells, researchers are now exploring the use of CAR-engineered NK cells for the treatment of various hematological and non-hematological malignancies. Herein, we review preclinical data on the development of CAR-NK cells, advantages, disadvantages, and current obstacles to their clinical use.

Adverse Effects Associated with Clinical Applications of CAR Engineered T Cells

Cancer has been ranked as the second leading cause of death in the United States. To reduce cancer mortality, immunotherapy is gaining momentum among other therapeutic modalities, due to its impressive results in clinical trials. The genetically engineered T cells expressing chimeric antigen receptors (CARs) are emerging as a new approach in cancer immunotherapy, with the most successful outcomes in the refractory/relapse hematologic malignancies. However, the widespread clinical applications are limited by adverse effects some of which are life-threatening. Strategies to reduce the chance of side effects as well as close monitoring, rapid diagnosis and proper treatment of side effects are necessary to take the most advantages of this valuable therapy. Here we review the reported toxicities associated with CAR engineered T cells, the strategies to ameliorate the toxicity, and further techniques and designs leading to a safer CAR T-cell therapy.

Chimeric Antigen Receptor-T Cell Therapy: Practical Considerations for Implementation in Europe

Chimeric antigen receptor (CAR)-T cell therapy is a new class of cellular immunotherapies that involves ex vivo genetic modification of T cells to incorporate an engineered CAR. After infusion into the patient, the CAR-expressing T cells recognize specific tumor targets and induce an immune response against them. The technology utilized is fundamentally different from previously available cancer treatments. Currently, most CAR-T cell therapies use autologous T cells. Tisagenlecleucel (formerly CTL019) is an anti-CD19 CAR-T cell therapy that was recently approved in the United States for the treatment of pediatric and young adult patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). Tisagenlecleucel has shown robust in vivo expansion and long-term persistence, clinically meaningful durable response and remission rates, and overall survival benefit in pediatric and young adult patients with relapsed/refractory B-ALL and in relapsed/refractory diffuse large B-cell lymphoma. Common adverse events (AEs) include cytokine release syndrome, which may require hospitalization and admission to an intensive care unit, neurological toxicities, and B-cell aplasia. These AEs are manageable when treated by an appropriately trained team. Additional research is required to further develop AE management protocols. In this review, we describe regulatory requirements, clinical considerations, and site-level requirements for clinical study implementation of CAR-T cell therapy in Europe. We also provide a case study of the European experience from the first global clinical trial for tisagenlecleucel, which may serve as a useful starting point for investigators and clinicians looking to implement CAR-T cell therapy at their institutions.

Biomarkers of cytokine release syndrome and neurotoxicity related to CAR-T cell therapy

Severe cytokine release syndrome (CRS) and neurotoxicity following chimeric antigen receptor T cell (CAR-T) therapy can be life-threatening in some cases, and management of those toxicities is still a great challenge for physicians. Researchers hope to understand the pathophysiology of CRS and neurotoxicity, and identify predictive biomarkers that can forecast those toxicities in advance. Some risk factors for severe CRS and/or neurotoxicity including patient and treatment characteristics have been identified in multiple clinical trials of CAR-T cell therapy. Moreover, several groups have identified some predictive biomarkers that are able to determine beforehand which patients may suffer severe CRS and/or neurotoxicity during CAR-T cell therapy, facilitating testing of early intervention strategies for those toxicities. However, further studies are needed to better understand the biology and related risk factors for CRS and/or neurotoxicity, and determine if those identified predictors can be extrapolated to other series. Herein, we review the pathophysiology of CRS and neurotoxicity, and summarize the progress of predictive biomarkers to improve CAR-T cell therapy in cancer.

Comparison of T Cell Activities Mediated by Human TCRs and CARs That Use the Same Recognition Domains

Adoptive T cell therapies have achieved significant clinical responses, especially in hematopoietic cancers. Two types of receptor systems have been used to redirect the activity of T cells, normal heterodimeric TCRs or synthetic chimeric Ag receptors (CARs). TCRs recognize peptide-HLA complexes whereas CARs typically use an Ab-derived single-chain fragments variable that recognizes cancer-associated cell-surface Ags. Although both receptors mediate diverse effector functions, a quantitative comparison of the sensitivity and signaling capacity of TCRs and CARs has been limited due to their differences in affinities and ligands. In this study we describe their direct comparison by using TCRs that could be formatted either as conventional αβ heterodimers, or as single-chain fragments variable constructs linked to CD3ζ and CD28 signaling domains or to CD3ζ alone. Two high-affinity TCRs (K_D values of ∼50 and 250 nM) against MART1/HLA-A2 or WT1/HLA-A2 were used, allowing MART1 or WT1 peptide titrations to easily assess the impact of Ag density. Although CARs were expressed at higher surface levels than TCRs, they were 10-100-fold less sensitive, even in the absence of the CD8 coreceptor. Mathematical modeling demonstrated that lower CAR sensitivity could be attributed to less efficient signaling kinetics. Furthermore, reduced cytokine secretion observed at high Ag density for both TCRs and CARs suggested a role for negative regulators in both systems. Interestingly, at high Ag density, CARs also mediated greater maximal release of some cytokines, such as IL-2 and IL-6. These results have implications for the next-generation design of receptors used in adoptive T cell therapies.

Cellular Immunotherapy for Hematologic Malignancies: Beyond Bone Marrow Transplantation

Immunotherapy has changed treatment practices for many hematologic malignancies. Even in the current era of targeted therapy, chemotherapy remains the backbone of treatment for many hematologic malignancies, especially in acute leukemias, where relapse remains the major cause of mortality. Application of novel immunotherapies in hematology attempts to harness the killing power of the immune system against leukemia and lymphoma. Cellular immunotherapy is evolving rapidly for high-risk hematologic disorders. Recent advances include chimeric antigen-receptor T cells, mesenchymal stromal/stem cells, dendritic cell tumor vaccines, cytokine-induced killer cells, and virus-specific T cells. The advantages of nontransplantation cellular immunotherapy include suitability for patients for whom transplantation has failed or is contraindicated, and a potentially less-toxic treatment alternative to transplantation for relapsed/refractory patients. This review examines those emerging cellular immunotherapies that are changing treatment paradigms for patients with hematologic malignancies.

Cellular kinetics of CTL019 in relapsed/refractory B-cell acute lymphoblastic leukemia and chronic lymphocytic leukemia

Tisagenlecleucel (CTL019) is an investigational immunotherapy that involves reprogramming a patient's own T cells with a transgene encoding a chimeric antigen receptor to identify and eliminate CD19-expressing cells. We previously reported that CTL019 achieved impressive clinical efficacy in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL), including the expansion and persistence of CTL019 cells, which correlates with response to therapy. Here, we performed formal cellular kinetic analyses of CTL019 in a larger cohort of 103 patients treated with CTL019 in 2 different diseases (ALL and CLL). CTL019 was measured in peripheral blood and bone marrow, using quantitative polymerase chain reaction and flow cytometry. CTL019 levels in peripheral blood typically peaked at 10 to 14 days postinfusion and then declined slowly over time. Patients with complete response (CR)/CR with incomplete count recovery had higher levels of CTL019 in peripheral blood, with greater maximal concentration and area under the curve values compared with nonresponding patients (P < .0001 for each). CTL019 transgene levels were measurable up to 780 days in peripheral blood. CTL019 trafficking and persistence were observed in bone marrow and cerebrospinal fluid. CTL019 expansion correlated with severity of cytokine release syndrome (CRS) and preinfusion tumor burden in pediatric ALL. The results described here are the first detailed formal presentation of cellular kinetics across 2 diseases and highlight the importance of the application of in vivo cellular kinetic analyses to characterize clinical efficacy and CRS severity associated with CTL019 therapy.

Emerging therapies for acute myeloid leukemia: translating biology into the clinic

Acute myeloid leukemia (AML) is an aggressive hematological malignancy with a poor outcome; overall survival is approximately 35% at two years and some subgroups have a less than 5% two-year survival. Recently, significant improvements have been made in our understanding of AML biology and genetics. These fundamental discoveries are now being translated into new therapies for this disease. This review will discuss recent advances in AML biology and the emerging treatments that are arising from biological studies. Specifically, we will consider new therapies that target molecular mutations in AML and dysregulated pathways such as apoptosis and mitochondrial metabolism. We will also discuss recent advances in immune and cellular therapy for AML.

Kinetics and biomarkers of severe cytokine release syndrome after CD19 chimeric antigen receptor-modified T-cell therapy

Lymphodepletion chemotherapy followed by infusion of CD19-specific chimeric antigen receptor-modified (CAR) T cells has produced impressive antitumor responses in patients with refractory CD19⁺ B-cell malignancies but is often associated with cytokine release syndrome (CRS). Our understanding of CRS continues to evolve, and identification of the kinetics of CRS and predictive clinical and laboratory biomarkers of severity are needed to evaluate strategies to mitigate toxicity. We report the clinical presentation of and identify biomarkers of severe CRS in 133 adult patients who received CD19 CAR T cells. CRS developed in 70% of patients, including 62.5% with grade 1 to 3 CRS (grade 1, 26%; grade 2, 32%; grade 3, 4.5%), 3.8% with grade 4, and 3.8% with grade 5. A majority of cases of grade ≥4 CRS occurred during CAR T-cell dose finding. Multivariable analysis of baseline characteristics identified high marrow tumor burden, lymphodepletion using cyclophosphamide and fludarabine, higher CAR T-cell dose, thrombocytopenia before lymphodepletion, and manufacturing of CAR T cells without selection of CD8⁺ central memory T cells as independent predictors of CRS. Severe CRS was characterized by hemodynamic instability, capillary leak, and consumptive coagulopathy. Angiopoietin-2 and von Willebrand factor, which are biomarkers of endothelial activation, were increased during severe CRS and also before lymphodepletion in patients who subsequently developed CRS. We describe a classification-tree algorithm to guide studies of early intervention after CAR T-cell infusion for patients at high risk of severe CRS. These data provide a framework for early intervention studies to facilitate safer application of effective CD19 CAR T-cell therapy.

Advances in immunopathogenesis of macrophage activation syndrome during rheumatic inflammatory diseases: toward new therapeutic targets?

INTRODUCTION

Macrophage activation syndrome (MAS) is a severe, hyperinflammatory life-threatening syndrome, generally complicating different rheumatic diseases. Despite the severity of the disease, little is known about the pathogenic mechanisms and, thus, possible targeted therapies in the management of these patients. Areas covered: In this review, we aimed to update the current pathogenic knowledge of MAS, during rheumatic diseases, focusing mainly on immunologic abnormalities and on new possible therapeutic strategies. Expert commentary: The difficult pathogenic scenario of MAS, in which genetic defects, predisposing diseases, and triggers are mixed together with the high mortality rate, make it difficult to manage these patients. Although most efforts have been focused on investigating the disease in children, in recent years, several studies are trying to elucidate the possible pathogenic mechanism in adult MAS patients. In this context, genetic and immunological studies might lead to advances in the knowledge of pathogenic mechanisms and possible new therapeutic targets. In the future, the results of ongoing clinical trials are awaited in order to improve the management and, thus, the survival of these patients.