The impact of granulocyte colony stimulating factor on patients receiving chimeric antigen receptor T-cell therapy

Immune effector cell-associated haematotoxicity after CAR T-cell therapy: from mechanism to management

Genetically engineered chimeric antigen receptor (CAR) T cells have become an effective treatment option for several advanced B-cell malignancies. Haematological side-effects, classified in 2023 as immune effector cell-associated haematotoxicity (ICAHT), are very common and can predispose for clinically relevant infections. As haematopoietic reconstitution after CAR T-cell therapy differs from chemotherapy-associated myelosuppression, a novel classification system for early and late ICAHT has been introduced. Furthermore, a risk stratification score named CAR-HEMATOTOX has been developed to identify candidates at high risk of ICAHT, thereby enabling risk-based interventional strategies. Therapeutically, growth factor support with granulocyte colony-stimulating factor (G-CSF) is the mainstay of treatment, with haematopoietic stem cell (HSC) boosts available for patients who are refractory to G-CSF (if available). Although the underlying pathophysiology remains poorly understood, translational studies from the past 3 years suggest that CAR T-cell-induced inflammation and baseline haematopoietic function are key contributors to prolonged cytopenia. In this Review, we provide an overview of the spectrum of haematological toxicities after CAR T-cell therapy and offer perspectives on future translational and clinical developments.

Mechanisms and management of CAR T toxicity

Chimeric antigen receptor (CAR) T cell therapies have dramatically improved treatment outcomes for patients with relapsed or refractory B-cell acute lymphoblastic leukemia, large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, and multiple myeloma. Despite unprecedented efficacy, treatment with CAR T cell therapies can cause a multitude of adverse effects which require monitoring and management at specialized centers and contribute to morbidity and non-relapse mortality. Such toxicities include cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, neurotoxicity distinct from ICANS, immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome, and immune effector cell-associated hematotoxicity that can lead to prolonged cytopenias and infectious complications. This review will discuss the current understanding of the underlying pathophysiologic mechanisms and provide guidelines for the grading and management of such toxicities.

Associations of granulocyte colony-stimulating factor with toxicities and efficacy of chimeric antigen receptor T-cell therapy in relapsed or refractory B-cell acute lymphoblastic leukemia

Few studies have reported the associations of granulocyte colony-stimulating factor (G-CSF) with cytokine release syndrome (CRS), neurotoxic events (NEs) and efficacy after chimeric antigen receptor (CAR) T-cell therapy for relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). We present a retrospective study of 67 patients with R/R B-ALL who received anti-CD19 CAR T-cell therapy, 41 (61.2%) patients received G-CSF (G-CSF group), while 26 (38.8%) did not (non-G-CSF group). Patients had similar duration of grade 3-4 neutropenia between the two groups. The incidences of CRS and NEs were higher in G-CSF group, while no differences in severity were found. Further stratified analysis showed that the incidence and severity of CRS were not associated with G-CSF administration in patients with low bone marrow (BM) tumor burden. None of the patients with low BM tumor burden developed NEs. However, there was a significant increase in the incidence of CRS after G-CSF administration in patients with high BM tumor burden. The duration of CRS in patients who used G-CSF was longer. There were no significant differences in response rates at 1 and 3 months after CAR T-cell infusion, as well as overall survival (OS) between the two groups. In conclusion, our results showed that G-CSF administration was not associated with the incidence or severity of CRS in patients with low BM tumor burden, but the incidence of CRS was higher after G-CSF administration in patients with high BM tumor burden. The duration of CRS was prolonged in G-CSF group. G-CSF administration was not associated with the efficacy of CAR T-cell therapy.

Mucormycosis after CD19 chimeric antigen receptor T-cell therapy: results of a US Food and Drug Administration adverse events reporting system analysis and a review of the literature

Chimeric antigen receptor (CAR) T-cell therapy leads to durable remissions in relapsed B-cell cancers, but treatment-associated immunocompromise leads to a substantial morbidity and mortality risk from atypical infection. Mucormycosis is an aggressive and invasive fungal infection with a mortality risk of 40-80% in patients with haematological malignancies. In this Grand Round, we report a case of mucormycosis in a 54-year-old patient undergoing CAR T-cell therapy who reached complete clinical control of Mucorales with combined aggressive surgical debridement, antifungal pharmacotherapy, and reversal of underlying risk factors, but with substantial morbidity from extensive oro-facial surgery affecting the patient's speech and swallowing. For broader context, we present our case alongside an US Food and Drugs Administration adverse events reporting database analysis and a review of the literature to fully evaluate the clinical burden of mucormycosis in patients treated with CAR T-cell therapy. We discuss epidemiology, clinical features, diagnostic tools, and current frameworks for treatment and prophylaxis. We did this analysis to promote increased vigilance for mucormycosis among physicians specialising in CAR T-cell therapy and microbiologists and to illustrate the importance of early initiation of therapy to effectively manage this condition. Mucormycosis prevention and early diagnosis, through targeted surveillance and mould prevention in patients at highest risk and Mucorales-specific screening assays, is likely to be key to improving outcomes in patients treated with CAR T-cell therapy.

Hematopoiesis and immune reconstitution after CD19 directed chimeric antigen receptor T-cells (CAR-T): A comprehensive review on incidence, risk factors and current management

Impaired function of hematopoiesis after treatment with chimeric antigen T-cells (CAR-T) is a frequent finding and can interest a wide range of patients, regardless of age and underlying disease. Trilinear cytopenias, as well as hypogammaglobulinemia, B-cell aplasia, and T-cell impairment, can severely affect the infectious risk of CAR-T recipients, as well as their quality of life. In this review, we provide an overview of defects in hematopoiesis after CAR-T, starting with a summary of different definitions and thresholds. We then move to summarize the main pathogenetic mechanisms of cytopenias, and we offer insight into cytomorphological aspects, the role of clonal hematopoiesis, and the risk of secondary myeloid malignancies. Subsequently, we expose the major findings and reports on T-cell and B-cell quantitative and functional impairment after CAR-T. Finally, we provide an overview of current recommendations and leading experiences regarding the management of cytopenias and defective B- and T-cell function.

Recognizing, defining, and managing CAR-T hematologic toxicities

Autologous CAR-T cell therapy (CAR-T) has improved outcomes for patients with B-cell malignancies. It is associated with the well-described canonical toxicities cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), which may be abrogated by corticosteroids and the anti-IL6 receptor antagonist tocilizumab. Practitioners and researchers should be aware of additional toxicities. Here we review current understanding and management of hematologic toxicities after CAR-T, including cytopenias, coagulopathies, bleeding and clotting events, hemophagocytic-lymphohistiocytosis, and tumor lysis syndrome. We pay particular attention to cytopenias, recently termed immune effector cell-associated hematological toxicity (ICAHT). While the "H" is silent, hematotoxicity is not: ICAHT has the highest cumulative incidence of all immune adverse events following CAR-T. Early cytopenia (day 0-30) is closely linked to lymphodepleting chemotherapy and CRS-related inflammatory stressors. Late ICAHT (after day 30) can present either with or without antecedent count recovery (e.g., "intermittent" vs "aplastic" phenotype), and requires careful evaluation and management strategies. Growth factor support is the mainstay of treatment, with recent evidence demonstrating safety and feasibility of early granulocyte colony-stimulating factor (G-CSF) (e.g., within week 1). In G-CSF refractory cases, autologous stem cell boosts represent a promising treatment avenue, if available. The CAR-HEMATOTOX scoring system, validated for use across lymphoid malignancies (B-NHL, multiple myeloma), enables pretherapeutic risk assessment and presents the potential for risk-adapted management. Recent expert panels have led to diagnostic scoring criteria, severity grading systems, and management strategies for both ICAHT and the recently termed immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS), now clarified and defined as a distinct entity from CRS.

Managing side effects: guidance for use of immunotherapies in multiple myeloma

Chimeric antigen receptor T-cell therapy and bispecific T-cell recruiting antibodies have transformed the treatment landscape for relapsed/refractory multiple myeloma, with B-cell maturation antigen being the most common target and other targets in clinical development. However, these therapies are associated with unique and severe toxicities, including cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), delayed neurotoxicity, cytopenias, and infection. In addition, immune effector cell-associated hemophagocytic lymphohistiocytosis (HLH)-like syndrome (IEC-HS), which exhibits overlap between CRS and HLH, can be challenging to diagnose and treat. In this review, we provide an overview of toxicities associated with novel immunotherapies for treatment of multiple myeloma and describe management recommendations. The pathophysiology and risk factors behind these toxicities are not yet comprehensively understood. Based on consensus recommendations, treatment for CRS consists of tocilizumab and steroids, while treatment for ICANS includes steroids and anakinra in severe cases. Management of cytopenias and infection is similar to post-hematopoietic cell transplantation principles with antimicrobial prophylaxis, growth factor support, immunoglobulin replacement, and vaccinations. In contrast, effective treatments for delayed neurotoxicity and IEC-HS are lacking, although steroids and anakinra are commonly used. Management of all these toxicities should include a broad differential and multidisciplinary collaboration with infectious diseases, neurology, and/or critical care providers.

Early granulocyte colony stimulating factor administration increases the risk of cytokine release syndrome in acute lymphoblastic leukemia patients receiving anti-CD19 chimeric antigen receptor T-cell therapy

Cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS) and neutropenia are common toxicities associated with chimeric antigen receptor T (CAR-T) cell therapy. The role of granulocyte colony stimulating factor (G-CSF) in CAR-T-cell-treated patients remains unclear. To explore the efficacy and safety of early G-CSF administration in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) who were receiving autologous anti-CD19 CAR-T cells, we retrospectively collected and summarized clinical data to compare patients receiving G-CSF within 14 days (early G-CSF group) to patients receiving later or no G-CSF (control group) after their CART infusion. The results showed that there was no significant difference in the incidence and duration of neutropenia between the early G-CSF group and the control group (77% vs. 63%, p = 0.65; 8 vs. 4 days, p = 0.37, respectively). However, the incidence and duration of CRS were significantly higher in the early G-CSF group than in the control group (81% vs. 38%, p = 0.03; 3 vs. 0 days, p = 0.004, respectively). Moreover, early G-CSF application had no significant effect on the expansion and efficacy of CAR-T cells. In conclusion, our study suggested that early G-CSF administration did not reduce the incidence and duration of neutropenia but rather increased the incidence and duration of CRS.

Immune effector cell-associated hematotoxicity: EHA/EBMT consensus grading and best practice recommendations

Hematological toxicity is the most common adverse event after chimeric antigen receptor (CAR) T-cell therapy. Cytopenias can be profound and long-lasting and can predispose for severe infectious complications. In a recent worldwide survey, we demonstrated that there remains considerable heterogeneity in regard to current practice patterns. Here, we sought to build consensus on the grading and management of immune effector cell-associated hematotoxicity (ICAHT) after CAR T-cell therapy. For this purpose, a joint effort between the European Society for Blood and Marrow Transplantation (EBMT) and the European Hematology Association (EHA) involved an international panel of 36 CAR T-cell experts who met in a series of virtual conferences, culminating in a 2-day meeting in Lille, France. On the basis of these deliberations, best practice recommendations were developed. For the grading of ICAHT, a classification system based on depth and duration of neutropenia was developed for early (day 0-30) and late (after day +30) cytopenia. Detailed recommendations on risk factors, available preinfusion scoring systems (eg, CAR-HEMATOTOX score), and diagnostic workup are provided. A further section focuses on identifying hemophagocytosis in the context of severe hematotoxicity. Finally, we review current evidence and provide consensus recommendations for the management of ICAHT, including growth factor support, anti-infectious prophylaxis, transfusions, autologous hematopoietic stem cell boost, and allogeneic hematopoietic cell transplantation. In conclusion, we propose ICAHT as a novel toxicity category after immune effector cell therapy, provide a framework for its grading, review literature on risk factors, and outline expert recommendations for the diagnostic workup and short- and long-term management.

Management of Adverse Reactions for BCMA-Directed Therapy in Relapsed Multiple Myeloma: A Focused Review

Anti-B-cell maturation antigen therapies consisting of bispecific antibodies, antibody-drug conjugates, and chimeric antigen receptor T cells have shown promising results in relapsed refractory multiple myeloma (RRMM). However, the severe side effects include cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, cytopenia(s), infections, hemophagocytic lymphohistiocytosis, and organ toxicity, which could sometimes be life-threatening. This review focuses on these most common complications post-BCMA therapy. We discussed the risk factors, pathogenesis, clinical features associated with these complications, and how to prevent and treat them. We included four original studies for this focused review. All four agents (idecabtagene vicleucel, ciltacabtagene autoleucel, teclistamab, belantamab mafodotin) have received FDA approval for adult RRMM patients. We went through the FDA access data packages of the approved agents to outline stepwise management of the complications for better patient outcomes.

An International Survey on Grading, Diagnosis, and Management of Immune Effector Cell-Associated Hematotoxicity (ICAHT) Following CAR T-cell Therapy on Behalf of the EBMT and EHA

Hematological toxicity represents the most common grade ≥3 toxicity after chimeric antigen receptor (CAR) T-cell therapy. However, its underlying pathophysiology is incompletely understood and its grading and management remains ill-defined. To inform the forthcoming European Hematology Association/European Society for Blood and Marrow Transplantation (EHA/EBMT) guidelines on the management of "immune effector cell-associated hematotoxicity" (ICAHT), we undertook a survey of experienced clinicians using an online survey focusing on (1) grading, (2) risk-stratification and diagnostic work-up, (3) short-term, and (4) long-term management of ICAHT. There were 81 survey respondents across 18 countries. A high degree of variability was noted for cytopenia grading in regards to depth, duration, and time from CAR-T infusion. The majority of experts favored pre-CAR-T bone marrow studies, especially in case of a high-risk profile. Most respondents felt that the work-up for patients with severe hematotoxicity should rule-out viral infections (96%), substrate deficiency (80%), or coincident sHLH/MAS (serum ferritin, 92%), and should include bone marrow aspiration (86%) and/or biopsy (61%). Clinicians were divided as to whether the occurrence of coincident immunotoxicity should influence the decision to apply G-CSF, and when to initiate G-CSF support. In case of prolonged thrombocytopenia, most survey participants favored thrombopoietin agonists (86%). Conversely, autologous hematopoietic cell boosts represented the preferred choice for neutropenia (63%), although they were frequently not available and no consensus was reached regarding the optimal trigger point. These findings underline the current heterogeneity of practice patterns regarding ICAHT and invite the development of consensus guidelines, which may harmonize grading, establish standard operating procedures for diagnosis, and set management guidelines.

Chimeric Antigen Receptor T-Cell Therapy and Hematopoiesis

Chimeric Antigen Receptor (CAR) T-cell therapy is a promising treatment option for patients suffering from B-cell- and plasma cell-derived hematologic malignancies and is being adapted for the treatment of solid cancers. However, CAR T is associated with frequently severe toxicities such as cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), macrophage activation syndrome (MAS), and prolonged cytopenias-a reduction in the number of mature blood cells of one or more lineage. Although we understand some drivers of these toxicities, their mechanisms remain under investigation. Since the CAR T regimen is a complex, multi-step process with frequent adverse events, ways to improve the benefit-to-risk ratio are needed. In this review, we discuss a variety of potential solutions being investigated to address the limitations of CAR T. First, we discuss the incidence and characteristics of CAR T-related cytopenias and their association with reduced CAR T-cell efficacy. We review approaches to managing or mitigating cytopenias during the CAR T regimen-including the use of growth factors, allogeneic rescue, autologous hematopoietic stem cell infusion, and alternative conditioning regimens. Finally, we introduce novel methods to improve CAR T-cell-infusion products and the implications of CAR T and clonal hematopoiesis.

Effect of granulocyte colony-stimulating factor on toxicities after CAR T cell therapy for lymphoma and myeloma

Chimeric antigen receptor T cells (CAR T) are groundbreaking therapies but may cause significant toxicities including cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and cytopenias. Granulocyte colony-stimulating factor (G-CSF) is often used to mitigate neutropenia after CAR T, but there is no consensus recommended strategy due to hypothesized, but largely unknown risks of exacerbating toxicities. To investigate the impact of G-CSF, we retrospectively analyzed 197 patients treated with anti-CD19 CAR T for lymphoma and 47 patients treated with anti-BCMA CAR T for multiple myeloma. In lymphoma, 140 patients (71%) received prophylactic G-CSF before CAR T (mostly pegylated G-CSF) and were compared with 57 patients (29%) treated with G-CSF after CAR T or not exposed. Prophylactic G-CSF was associated with faster neutrophil recovery (3 vs. 4 days, P < 0.01) but did not reduce recurrent neutropenia later. Prophylactic G-CSF was associated with increased grade ≥2 CRS (HR 2.15, 95% CI 1.11-4.18, P = 0.02), but not ICANS. In multiple myeloma, prophylactic G-CSF was not used; patients were stratified by early G-CSF exposure (≤2 days vs. ≥3 days after CAR T or no exposure), with no significant difference in toxicities. Future trials should clarify the optimal G-CSF strategy to improve outcomes after CAR T.

Infectious complications, immune reconstitution, and infection prophylaxis after CD19 chimeric antigen receptor T-cell therapy

CD19-targeted chimeric antigen receptor (CAR) T-cell becomes a breakthrough therapy providing excellent remission rates and durable disease control for patients with relapsed/refractory (R/R) hematologic malignancies. However, CAR T-cells have several potential side effects including cytokine release syndrome, neurotoxicities, cytopenia, and hypogammaglobulinemia. Infection has been increasingly recognized as a complication of CAR T-cell therapy. Several factors predispose CAR T-cell recipients to infection. Fortunately, although studies show a high incidence of infection post-CAR T-cells, most infections are manageable. In contrast to patients who undergo hematopoietic stem cell transplant, less is known about post-CAR T-cell immune reconstitution. Therefore, evidence regarding antimicrobial prophylaxis and vaccination strategies in these patients is more limited. As CAR T-cell therapy becomes the standard treatment for R/R B lymphoid malignancies, we should expect a larger impact of infections in these patients and the need for increased clinical attention. Studies exploring infection and immune reconstitution after CAR T-cell therapy are clinically relevant and will provide us with a better understanding of the dynamics of immune function after CAR T-cell therapy including insights into appropriate strategies for prophylaxis and treatment of infections in these patients. In this review, we describe infections in recipients of CAR T-cells, and discuss risk factors and potential mitigation strategies.

The CAR-HEMATOTOX risk-stratifies patients for severe infections and disease progression after CD19 CAR-T in R/R LBCL

Background

CD19-directed chimeric antigen receptor T-cell therapy (CAR-T) represents a promising treatment modality for an increasing number of B-cell malignancies. However, prolonged cytopenias and infections substantially contribute to the toxicity burden of CAR-T. The recently developed CAR-HEMATOTOX (HT) score—composed of five pre-lymphodepletion variables (eg, absolute neutrophil count, platelet count, hemoglobin, C-reactive protein, ferritin)—enables risk stratification of hematological toxicity.

Methods

In this multicenter retrospective analysis, we characterized early infection events (days 0–90) and clinical outcomes in 248 patients receiving standard-of-care CD19 CAR-T for relapsed/refractory large B-cell lymphoma. This included a derivation cohort (cohort A, 179 patients) and a second independent validation cohort (cohort B, 69 patients). Cumulative incidence curves were calculated for all-grade, grade ≥3, and specific infection subtypes. Clinical outcomes were studied via Kaplan-Meier estimates.

Results

In a multivariate analysis adjusted for other baseline features, the HT score identified patients at high risk for severe infections (adjusted HR 6.4, 95% CI 3.1 to 13.1). HT^high patients more frequently developed severe infections (40% vs 8%, p<0.0001)—particularly severe bacterial infections (27% vs 0.9%, p<0.0001). Additionally, multivariate analysis of post-CAR-T factors revealed that infection risk was increased by prolonged neutropenia (≥14 days) and corticosteroid use (≥9 days), and decreased with fluoroquinolone prophylaxis. Antibacterial prophylaxis significantly reduced the likelihood of severe bacterial infections in HT^high (16% vs 46%, p<0.001), but not HT^low patients (0% vs 2%, p=n.s.). Collectively, HT^high patients experienced worse median progression-free (3.4 vs 12.6 months) and overall survival (9.1 months vs not-reached), and were hospitalized longer (median 20 vs 16 days). Severe infections represented the most common cause of non-relapse mortality after CAR-T and were associated with poor survival outcomes. A trend toward increased non-relapse mortality in HT^high patients was observed (8.0% vs 3.7%, p=0.09).

Conclusions

These data demonstrate the utility of the HT score to risk-stratify patients for infectious complications and poor survival outcomes prior to CD19 CAR-T. High-risk patients likely benefit from anti-infective prophylaxis and should be closely monitored for potential infections and relapse.

CAR-T-OPENIA: Chimeric antigen receptor T-cell therapy-associated cytopenias

Chimeric antigen receptor (CAR) T-cell is the most recent version in the evolution of cellular therapy with promising responses, which has revolutionized the management of some hematological malignancies in the current times. As the clinical use has progressed rather rapidly since the first approval in 2017, toxicities beyond cytokine release syndrome and immune effector cell-associated neurological syndrome have surfaced. Cytopenias are common in <30 days ("early"), 30-90 days ("short-term") as well as >90 days ("prolonged"); and have clinical implications to patient care as well as resource utilization. We review the details of etiology, factors associated with cytopenias, and management considerations for patients with cytopenias for each of these time-frames. This would potentially serve as a clinical guide for hematological toxicity or CAR-T-OPENIA, which is commonly encountered with the use of CAR T-cell therapy.