A Concise Review of Neurologic Complications Associated with Chimeric Antigen Receptor T-cell Immunotherapy

Evolving strategies for addressing CAR T-cell toxicities

The field of chimeric antigen receptor (CAR) T-cell therapy has grown from a fully experimental concept to now boasting a multitude of treatments including six FDA-approved products targeting various hematologic malignancies. Yet, along with their efficacy, these therapies come with side effects requiring timely and thoughtful interventions. In this review, we discuss the most common toxicities associated with CAR T-cells to date, highlighting risk factors, prognostication, implications for critical care management, patient experience optimization, and ongoing work in the field of toxicity mitigation. Understanding the current state of the field and standards of practice is critical in order to improve and manage potential toxicities of both current and novel CAR T-cell therapies as they are applied in the clinic.

Patterns of neurotoxicity among patients receiving chimeric antigen receptor T-cell therapy: A single-centre cohort study

BACKGROUND AND PURPOSE

Immune effector cell-associated neurotoxicity syndrome (ICANS) is an important complication of chimeric antigen receptor T-cell (CAR-T) therapy. This study aims to identify the patterns of neurotoxicity among patients with ICANS at a tertiary referral centre in Australia.

METHODOLOGY

This single-centre, prospective cohort study included all consecutively recruited patients who underwent CAR-T therapy for eligible haematological malignancies. All patients underwent a comprehensive neurological assessment and cognitive screening before CAR-T infusion, during the development of ICANS, and 1 month after treatment. Baseline demographic characteristics, incidence, and neurological patterns of neurotoxicity management were evaluated.

RESULTS

Over a 19-month period, 23% (12) of the 53 eligible patients developed neurotoxicity (10/12 [83%] being grade 1). All patients showed changes in handwriting and tremor as their initial presentation. Changes in cognition were manifested in most of the patients, with a more substantial drop noted in their Montreal Cognitive Assessment compared to immune effector cell-associated encephalopathy scores. All manifestations of neurotoxicity were short-lived and resolved within a 1-month period, with a mean duration of 8.2 days (range = 1-33).

CONCLUSIONS

The patterns of CAR-T-related neurotoxicity often include change in handwriting, tremor, and mild confusional state, especially early in their evolution. These may remain undetected by routine neurological surveillance. These features represent accessible clinical markers of incipient ICANS.

Complications of Cancer Therapy in Children: A Comprehensive Review of Neuroimaging Findings

ABSTRACT

Complications of cancer therapy in children can result in a spectrum of neurologic toxicities that may occur at the initiation of therapy or months to years after treatment. Although childhood cancer remains rare, increasing survival rates mean that more children will be living longer after cancer treatment. Therefore, complications of cancer therapy will most likely occur with increasing frequency.At times, it is very difficult to differentiate between therapeutic complications and other entities such as tumor recurrence, development of secondary malignancy, and infection (among other conditions). Radiologists often play a key role in the diagnosis and evaluation of pediatric patients with malignancies, and thus, awareness of imaging findings of cancer complications and alternative diagnoses is essential in guiding management and avoiding misdiagnosis. The aim of this review article is to illustrate the typical neuroimaging findings of cancer therapy-related toxicities, including both early and late treatment effects, highlighting pearls that may aid in making the appropriate diagnosis.

Neurological adverse effects of chimeric antigen receptor T-cell therapy

INTRODUCTION

Chimeric antigen receptor (CAR) T-cell is among the most prevalent approaches that act by directing T-cells toward cancer; however, they need to be optimized to minimize side effects and maximize efficacy before being used as standard treatment for malignancies. Neurotoxicity associated with CAR T-cell therapy has been well-documented in recent works.

AREAS COVERED

In this regard, two established syndromes exist. Immune effector cell-associated neurotoxicity syndrome (ICANS), previously called cytokine release encephalopathy syndrome (CRES), is a neuropsychiatric condition which can occur after therapy by immune effector cells (IEC) and T-lymphocytes utilizing treatments. Another syndrome is cytokine release syndrome (CRS), which may overlap with ICANS.

EXPERT OPINION

ICANS clinical manifestations include cerebral edema, mild lethargy, aphasia, and seizures. Notably, ICANS is associated with changes to EEG and neuroradiological findings. Therefore, it is necessary to make a timely and accurate diagnosis of neurological complications of CAR T-cells by clinical presentations, neuroimaging, and EEG. Since neurological events by different CAR T-cell products are heterogeneous, guides should be developed according to each product. Here, we provide an updated review of general information on CAR T-cell therapies and applications, neurological syndromes associated with their use, and risk factors contributing to ICANS.

CAR-T cells neurotoxicity from consolidated practice in hematological malignancies to fledgling experience in CNS tumors: fill the gap

Chimeric antigen receptor (CAR-T) therapy has marked a paradigm shift in the treatment of hematological malignancies and represent a promising growing field also in solid tumors. Neurotoxicity is a well-recognized common complication of CAR-T therapy and is at the forefront of concerns for CAR-based immunotherapy widespread adoption, as it necessitates a cautious approach. The non-specific targeting of the CAR-T cells against normal tissues (on-target off-tumor toxicities) can be life-threatening; likewise, immune-mediate neurological symptoms related to CAR-T cell induced inflammation in central nervous system (CNS) must be precociously identified and recognized and possibly distinguished from non-specific symptoms deriving from the tumor itself. The mechanisms leading to ICANS (Immune effector Cell-Associated Neurotoxicity Syndrome) remain largely unknown, even if blood-brain barrier (BBB) impairment, increased levels of cytokines, as well as endothelial activation are supposed to be involved in neurotoxicity development. Glucocorticoids, anti-IL-6, anti-IL-1 agents and supportive care are frequently used to manage patients with neurotoxicity, but clear therapeutic indications, supported by high-quality evidence do not yet exist. Since CAR-T cells are under investigation in CNS tumors, including glioblastoma (GBM), understanding of the full neurotoxicity profile in brain tumors and expanding strategies aimed at limiting adverse events become imperative. Education of physicians for assessing individualized risk and providing optimal management of neurotoxicity is crucial to make CAR-T therapies safer and adoptable in clinical practice also in brain tumors.

Glycyrrhizin for treatment of CRS caused by CAR T-cell therapy: A pharmacological perspective

Chimeric antigen receptor T (CAR T)-cell therapy promises to revolutionize the management of hematologic malignancies and possibly other tumors. However, the main side effect of cytokine release syndrome (CRS) is a great challenge for its clinical application. Currently, treatment of CRS caused by CAR T-cell therapy is limited to tocilizumab (TCZ) and corticosteroids in clinical guidelines. However, the theoretical risks of these two agents may curb clinicians' enthusiasm for their application, and the optimal treatment is still debated. CAR T-cell therapy induced-CRS treatment is a current research focus. Glycyrrhizin, which has diverse pharmacological effects, good tolerance, and affordability, is an ideal therapeutic alternative for CRS. It can also overcome the shortcoming of TCZ and corticosteroids. In this brief article, we discuss the therapeutic potential of glycyrrhizin for treating CRS caused by CAR T-cell therapy from the perspective of its pharmacological action.

Rehabilitation Needs for Patients Undergoing CAR T-Cell Therapy

PURPOSE OF REVIEW

Chimeric antigen receptor (CAR) T-cell therapy is a relatively new, innovative treatment strategy to manage refractory hematological cancers, including some types of leukemia, lymphoma, and multiple myeloma. This article outlines the CAR T-cell therapy process, toxicity, and complications, along with an overview of the currently known short- and long-term physical and functional sequelae that will be helpful for general or oncology rehabilitation specialists caring for these patients.

RECENT FINDINGS

There is a dearth of literature on the topic of rehabilitation of patients receiving CAR T-cell therapy. Rehabilitation practices can be extrapolated from the limited functional information on patients who have completed treatment for lymphoma and multiple myeloma. Patients present with cognitive impairment, muscle weakness, reduced exercise capacity, neuropathy, and cancer-related fatigue. Physical activity and rehabilitation programs may be beneficial to address fatigue, psychological symptoms, and quality of life. There is limited rehabilitation research in patients receiving CAR T-cell therapy. These patients may present with general deconditioning and neurological complications which translate to neuromuscular and cognitive impairment that benefit from multidisciplinary rehabilitation intervention prior to, during, and after treatment. Studies measuring the impairments at baseline and evaluation of the impact of rehabilitation practices are much needed to support this.

CRISPR Takes the Front Seat in CART-Cell Development

Chimeric antigen receptor T (CART)-cell immunotherapies have opened a door in the development of specialized gene therapies for hematological and solid cancers. Impressive response rates in pivotal trials led to the FDA approval of CART-cell therapy for certain hematological malignancies. However, autologous CART products are costly and time-intensive to manufacture, and most patients experience disease relapse within 1 year of CART administration. Additionally, CART-cell efficacy in solid tumors is extremely limited. CART-cell therapy is also associated with serious toxicities. Manufacturing difficulties, intrinsic T-cell defects, CART exhaustion, and treatment-associated toxicities are some of the current barriers to widespread adoption of CART-cell therapy. Genome editing tools such as CRISPR/Cas systems have demonstrated efficacy in further engineering CART cells to overcome these limitations. In this review, we will summarize the current approaches that use CRISPR to facilitate off-the-shelf CART products, increase CART-cell efficacy, and minimize CART-associated toxicities.

A Review of Acute and Long-Term Neurological Complications Following Haematopoietic Stem Cell Transplant for Paediatric Acute Lymphoblastic Leukaemia

Despite advances in haematopoietic stem cell transplant (HSCT) techniques, the risk of serious side effects and complications still exists. Neurological complications, both acute and long term, are common following HSCT and contribute to significant morbidity and mortality. The aetiology of neurotoxicity includes infections and a wide variety of non-infectious causes such as drug toxicities, metabolic abnormalities, irradiation, vascular and immunologic events and the leukaemia itself. The majority of the literature on this subject is focussed on adults. The impact of the combination of neurotoxic drugs given before and during HSCT, radiotherapy and neurological complications on the developing and vulnerable paediatric and adolescent brain remains unclear. Moreover, the age-related sensitivity of the nervous system to toxic insults is still being investigated. In this article, we review current evidence regarding neurotoxicity following HSCT for acute lymphoblastic leukaemia in childhood. We focus on acute and long-term impacts. Understanding the aetiology and long-term sequelae of neurological complications in children is particularly important in the current era of immunotherapy for acute lymphoblastic leukaemia (such as chimeric antigen receptor T cells and bi-specific T-cell engager antibodies), which have well-known and common neurological side effects and may represent a future treatment modality for at least a fraction of HSCT-recipients.

Chimeric Antigen Receptor (CAR)-Modified Immune Effector Cell Therapy for Acute Myeloid Leukemia (AML)

Despite the availability of an increasing number of targeted therapeutics and wider use of allogeneic hematopoietic stem cell transplantation, many patients with acute myeloid leukemia (AML) ultimately succumb to this disease. Given their remarkable efficacy in B-acute lymphoblastic leukemia and other CD19-expressing B cell malignancies, there is hope adoptive cellular transfer, particularly chimeric antigen receptor (CAR)-modified immune effector cell (IEC) therapies, may afford a novel, potent immune-based approach for the treatment of AML that complements or replaces existing ones and improves cure rates. However, it is unclear how best to translate the success of these therapies from B cell malignancies, where use of highly potent immunotherapies is facilitated by identified target antigens with near ubiquitous expression on malignant cells and non-fatal consequences from "on-target, off-tumor cell" toxicities. Herein, we review the current status of CAR-modified IEC therapies for AML, with considerations regarding suitable, relatively leukemia-restricted target antigens, expected toxicities, and interactions of the engineered cells with a profoundly immunosuppressive tumor microenvironment that restricts their therapeutic efficacy. With these challenges in mind, we will discuss possible strategies to improve the cells' potency as well as their therapeutic window for optimal clinical use in AML.