Immune Effector Cell-associated Neurotoxicity Research Articles

CTIM-02. PIONEERING QUAD-TARGETING CAR T CELL THERAPY IN PEDIATRIC CNS TUMORS – ANALYSIS FROM THE INITIAL PATIENTS TREATED ON THE FIRST-IN-HUMAN PHASE 1 TRIAL BRAINCHILD-04

Abstract BACKGROUND BrainChild-04 is a first-in-human clinical trial of quad-chimeric antigen receptor (CAR) T cell therapy for children and young adults with central nervous system (CNS) tumors. This trial administers repeated locoregional CAR T cells targeting B7-H3, EGFR, HER2, and IL-13Ralpha2 (“quad-CAR T cells”), leveraging multi-antigen targeting to address the tumor heterogeneity of high-grade CNS tumors. METHODS The primary endpoints are feasibility and safety, and secondary endpoints are disease response and correlative studies of CAR T cell activity. The trial utilized a Bayesian Optimal Interval (BOIN) statistical design with three planned dose regimens(DR). There are 2 arms with weekly delivery for 3 weeks of a 4-week cycle:(A) –diffuse intrinsic pontine glioma (DIPG), (B) –non-pontine diffuse midline glioma (DMG) or other relapsed CNS tumors. RESULTS Enrolled patients include DMG N=6, DIPG N=5, other CNS tumors N=4. Of the 15 enrolled patients, 7 have been infused with 8 awaiting infusions. A total of 33 intracranial CAR T doses have been delivered, including Arm A DR 1 (N=1), Arm B DR 1 (N=3), DR2 (N=3). The most common adverse events have been grade 1-2 fever (7/7 patients), grade 1-3 headache (6/7), and grade 1-2 nausea/vomiting (6/7). There have been no DLTs and no cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity (ICANS). CTCAE and tumor inflammation-associated neurotoxicity are both being captured. All treated patients are alive with median follow up time post-initial infusion of 93(14-198) days. CAR T cells were detected by flow cytometric analysis of CSF post-infusion in 14/24 CSF samples. Radiographic response, CSF circulating tumor DNA, targeted mass spectrometry, and cytokine analysis will be presented. CONCLUSIONS Our preliminary experience suggests tolerability of locoregional delivery of quad-CAR T cells at doses currently evaluated. The trial remains ongoing and these data support continued evaluation of this product to better assess anti-tumor activity in patients with CNS tumors, including DIPG/DMG.

Novel prognostic scoring systems for severe CRS and ICANS after anti-CD19 CAR T cells in large B-cell lymphoma

Autologous anti-CD19 chimeric antigen receptor (CAR) T cells are now used in routine practice for relapsed/refractory (R/R) large B-cell lymphoma (LBCL). Severe (grade ≥ 3) cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS) are still the most concerning acute toxicities leading to frequent intensive care unit (ICU) admission, prolonging hospitalization, and adding significant cost to treatment. We report on the incidence of CRS and ICANS and the outcomes in a large cohort of 925 patients with LBCL treated with axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel) in France based on patient data captured through the DESCAR-T registry. CRS of any grade occurred in 778 patients (84.1%), with 74 patients (8.0%) with grade 3 CRS or higher, while ICANS of any grade occurred in 375 patients (40.5%), with 112 patients (12.1%) with grade ≥ 3 ICANS. Based on the parameters selected by multivariable analyses, two independent prognostic scoring systems (PSS) were derived, one for grade ≥ 3 CRS and one for grade ≥ 3 ICANS. CRS-PSS included bulky disease, a platelet count < 150 G/L, a C-reactive protein (CRP) level > 30 mg/L and no bridging therapy or stable or progressive disease (SD/PD) after bridging. Patients with a CRS-PSS score > 2 had significantly higher risk to develop grade ≥ 3 CRS. ICANS-PSS included female sex, low level of platelets (< 150 G/L), use of axi-cel and no bridging therapy or SD/PD after bridging. Patients with a CRS-PSS score > 2 had significantly higher risk to develop grade ≥ 3 ICANS. Both scores were externally validated in international cohorts of patients treated with tisa-cel or axi-cel.

A systematic review and meta-analysis of nonrelapse mortality after CAR T cell therapy.

Although chimeric antigen receptor (CAR) T cell therapy represents a transformative immunotherapy, it is also associated with distinct toxicities that contribute to morbidity and mortality. In this systematic review and meta-analysis, we searched MEDLINE, Embase and CINAHL (Cochrane) for reports of nonrelapse mortality (NRM) after CAR T cell therapy in lymphoma and multiple myeloma up to March 2024. After extraction of causes and numbers of death, we analyzed NRM point estimates using random-effect models. We identified 7,604 patients across 18 clinical trials and 28 real-world studies. NRM point estimates varied across disease entities and were highest in patients with mantle-cell lymphoma (10.6%), followed by multiple myeloma (8.0%), large B cell lymphoma (6.1%) and indolent lymphoma (5.7%). Entity-specific meta-regression models for large B cell lymphoma and multiple myeloma revealed that axicabtagene ciloleucel and ciltacabtagene autoleucel were independently associated with increased NRM point estimates, respectively. Of 574 reported nonrelapse deaths, over half were attributed to infections (50.9%), followed by other malignancies (7.8%) and cardiovascular/respiratory events (7.3%). Conversely, the CAR T cell-specific side effects, immune effector cell-associated neurotoxicity syndrome/neurotoxicity, cytokine release syndrome and hemophagocytic lymphohistiocytosis, represented only a minority of nonrelapse deaths (cumulatively 11.5%). Our findings underline the critical importance of infectious complications after CAR T cell therapy and support the comprehensive reporting of NRM, including specific causes and long-term outcomes.

IMMU-01. PIONEERING QUAD-TARGETING CAR T CELL THERAPY IN PEDIATRIC CNS TUMORS – ANALYSIS FROM THE INITIAL PATIENTS TREATED ON THE FIRST-IN-HUMAN PHASE 1 TRIAL BRAINCHILD-04

Abstract BACKGROUND BrainChild-04 is a first-in-human clinical trial of quad-chimeric antigen receptor (CAR) T cell therapy for children and young adults with central nervous system (CNS) tumors. This trial administers repeated locoregional CAR T cells targeting B7-H3, EGFR, HER2, and IL-13Ralpha2 (“quad-CAR T cells”), leveraging multi-antigen targeting to address the tumor heterogeneity of high-grade CNS tumors. METHODS The primary endpoints are feasibility and safety, and secondary endpoints are disease response and correlative studies of CAR T cell activity. The trial utilized a Bayesian Optimal Interval (BOIN) design with three dose regimens (DR). There are 2 arms with weekly delivery for 3 weeks of a 4-week cycle:(A) –diffuse intrinsic pontine glioma (DIPG), (B) –non-pontine diffuse midline glioma (DMG) or other relapsed CNS tumors. RESULTS Enrolled patients include DMG N=6, DIPG N=5, other CNS tumors N=4. Of the 15 enrolled patients, 7 have been infused with 8 awaiting infusions. A total of 33 intracranial CAR T doses have been delivered, including Arm A DR 1 (N=1), Arm B DR 1 (N=3), DR2 (N=3). The most common adverse events have been grade 1-2 fever (7/7 patients), grade 1-3 headache (6/7), and grade 1-2 nausea/vomiting (6/7). There have been no DLTs and no cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity(ICANS). CTCAE and tumor inflammation-associated neurotoxicity are both being captured. All treated patients are alive with median follow up time post-initial infusion of 93(14-198) days. CAR T cells were detected by flow cytometric analysis of CSF post-infusion in 14/24 CSF samples. Radiographic response, CSF ct-DNA, targeted mass spectrometry, and cytokine analysis will be presented. CONCLUSIONS Our preliminary experience suggests tolerability of locoregional quad-CAR T therapy at doses evaluated. The trial remains ongoing and these data support continued evaluation of this product to better assess anti-tumor activity in patients with CNS tumors, including DIPG/DMG.

Biomaterial-Based Therapeutic Delivery of Immune Cells.

Immune cell therapy (ICT) is a transformative approach used to treat a wide range of diseases including type 1 diabetes, sickle cell disease, disorders of the hematopoietic system, and certain forms of cancers. Despite excellent clinical successes, the scope of adoptively transferred immune cells is limited because of toxicities like cytokine release syndrome and immune effector cell-associated neurotoxicity in patients. Furthermore, reports suggest that such treatment can impact major organ systems including cardiac, renal, pulmonary, and hepatic systems in the long term. Additionally, adoptively transferred immune cells cannot achieve significant penetration into solid tissues, thus limiting their therapeutic potential. Recent studies suggest that biomaterial-assisted delivery of immune cells can address these challenges by reducing toxicity, improving localization, and maintaining desired phenotypes to eventually regain tissue function. In this review, recent efforts in the field of biomaterial-based immune cell delivery for the treatment of diseases, their pros and cons, and where these approaches stand in terms of clinical treatment are highlighted.

Cardiovascular adverse events in patients with cancer treated with chimeric antigen receptor (CAR) T-cell therapy: A meta-analysis of both controlled and single-arm clinical trials.

e19006 Background: Chimeric antigen receptor (CAR-T) Chimeric antigen receptor (CAR) T-cell therapy presents a promising avenue in the treatment of hematological malignancies. However, the application of CAR-T cell therapy comes with a range of adverse effects, some of which are not fully understood yet. While previous research has primarily focused on immune effector cell-associated neurotoxicity (ICANs) and cytokine release syndrome (CRS), the cardiovascular safety profile of CAR-T cell therapy remains less defined. This meta-analysis assesses the incidence of cardiovascular (CV) events associated with CAR-T therapy, thereby providing critical insights into these events and guiding clinical decision-making. Methods: We conducted a Pubmed search of clinical trials evaluating the effect of CAR-T cell therapy in cancer patients with cardiovascular adverse events. For phase III trials, a quantitative assessment of Grade 3 or higher CV events was performed using the Review Manager (Rev-Man) Version 5.4 (The Cochrane Collaboration, 2020) and the results were reported as Odd Ratio (OR) with 95% Confidence Interval (CI). A fixed effect model was used. For phase I/II trials, the event rates were calculated for all-grade as well as grade 3 and higher CV adverse events. Results: A total of four Phase III clinical trials with 1345 patients were included for the comparison analysis. Among those trials, two involved multiple myeloma patients, and two involved large B cell lymphoma patients. The age range across trials was 20-83 years with a male-to-female ratio of 1.5:1. The analysis revealed that there was no statistically significant difference in Grade 3 or higher CV events between the CAR-T cell therapy and control (standard of care) groups: OR with 95% CI was 1.44 (0.73,2.82) (p=0.29). Grade 3 and above CV adverse event rates were 3.4% for the CAR-T and 2.1% for the control groups. Notably, there were two CV deaths in the CAR-T group and one CV death in the control group. Additionally, a total of 41 single-arm, Phase I/II clinical trials with 1479 participants were analyzed. Seven studies included solid cancers such as metastatic pancreatic cancer, biliary tract cancer and melanoma. The age range was 17-86 yr and male/female ratio was 1.5:1. Total all-grade CV adverse event rate was 21.83% and total grade 3 and above CV adverse event rate was 8.82%. There were eight CV deaths. Conclusions: There were significantly more CV adverse events reported in Phase I/II trials when compared to those reported in Phase III trials. This indicates that CV adverse events are important consequences of CAR-T cell therapy but are likely underreported in the Phase III clinical trials. Increased awareness and more standardized evaluation of CV adverse events of CAR-T is needed in the future clinical trials.

Neuroimaging Features of Cytokine-related Diseases.

Cytokines are small secreted proteins that have specific effects on cellular interactions and are crucial for functioning of the immune system. Cytokines are involved in almost all diseases, but as microscopic chemical compounds they cannot be visualized at imaging for obvious reasons. Several imaging manifestations have been well recognized owing to the development of cytokine therapies such as those with bevacizumab (antibody against vascular endothelial growth factor) and chimeric antigen receptor (CAR) T cells and the establishment of new disease concepts such as interferonopathy and cytokine release syndrome. For example, immune effector cell-associated neurotoxicity is the second most common form of toxicity after CAR T-cell therapy toxicity, and imaging is recommended to evaluate the severity. The emergence of COVID-19, which causes a cytokine storm, has profoundly impacted neuroimaging. The central nervous system is one of the systems that is most susceptible to cytokine storms, which are induced by the positive feedback of inflammatory cytokines. Cytokine storms cause several neurologic complications, including acute infarction, acute leukoencephalopathy, and catastrophic hemorrhage, leading to devastating neurologic outcomes. Imaging can be used to detect these abnormalities and describe their severity, and it may help distinguish mimics such as metabolic encephalopathy and cerebrovascular disease. Familiarity with the neuroimaging abnormalities caused by cytokine storms is beneficial for diagnosing such diseases and subsequently planning and initiating early treatment strategies. The authors outline the neuroimaging features of cytokine-related diseases, focusing on cytokine storms, neuroinflammatory and neurodegenerative diseases, cytokine-related tumors, and cytokine-related therapies, and describe an approach to diagnosing cytokine-related disease processes and their differentials. ©RSNA, 2024 Supplemental material is available for this article.

Glofitamab as a salvage treatment for B-cell lymphomas in the real world: A multicenter study in Taiwan.

Glofitamab is a bispecific antibody with promise for treating relapsed/refractory B-cell lymphoma according to a phase 1/2 clinical trial. This study examined its real-world effectiveness. This was an investigator-initiated, multicenter retrospective study including 34 patients who had relapsed/refractory B-cell lymphomas after at least three prior lines of therapy and received glofitamab monotherapy in a compassionate use program in Taiwan between January 2021 and October 2022. At a median follow-up of 15.9months, 56% of patients responded to glofitamab and 23% achieved complete remission. Response to the previous line of therapy significantly correlated with response to glofitamab (p=.020). Most responses were durable; only five out of the 19 responders had documented disease recurrence at the data cutoff date. The estimated progression-free survival (PFS) was 3.2months, and the estimated 1-year PFS was 33% for the entire cohort. PFS was better for responders than nonresponders (median PFS, 16.9vs. 1.8months; 1-year PFS, 60% vs. 0%). Forty-three cytokine release syndrome (CRS) events were observed, three of which were grade 3; all were manageable without glofitamab discontinuation. No immune effector cell-associated neurotoxicity was reported. Among seven hepatitis B virus (HBV) carriers (six had antiviral prophylaxis) and 14 patients with remote HBV (four had antiviral prophylaxis), no HBV reactivation was observed. In this real-world cohort, glofitamab exhibited effectiveness comparable to trial results without excessive CRS or new safety issues. With appropriate prophylaxis, glofitamab-treated patients with chronic or remote HBV infection are unlikely to experience virus reactivation.

Toxicity Profile of Brexucabtagene Autoleucel (brexu-cel; CD19-directed CAR T-cell therapy) in Adult Patients (pts) with Relapsed/Refractory (R/R) B-Cell Acute Lymphoblastic Leukemia (B-ALL): Results from a Multicenter Real-World Outcomes Study

Introduction: In October 2021, the FDA approved brexu-cel for the treatment of adults ≥ 18 years old with R/R B-ALL. Following this approval, a consortium of cancer centers was formed across the US to investigate outcomes following commercial brexu-cel use for adults with R/R B-ALL. One area of interest is the toxicity profile of brexu-cel when given in the real-world context, including the respective incidences and severity of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS). Methods: Eligible pts included adults ≥ 18 years old who received commercial brexu-cel starting in October 2021 onward at a participating center in the US (N = 25). Retrospective patient data were collected across participating institutions, with the most recent data lock occurring on June 30, 2023. Criteria from the ASTCT were used to grade CRS and ICANS severity. Statistical methods included the use of medians and simple ratios for descriptive outcomes; univariate logistic regression models were used to assess the association of various factors with the probability of CRS and ICANS, and Cox regression was used to examine the association of each with the hazards of mortality and failure for event-free survival (EFS; earliest of progression, relapse, or death). Results: Key demographics and toxicities are described in Tables 1 and 2 (respectively). Of the 152 pts infused with brexu-cel, 82% (N = 125) developed CRS and 56% (N = 85) developed ICANS. CRS and ICANS did NOT develop in 12% (N = 19). Twenty percent of all pts (N = 31) required ICU-level care for management of CAR-related toxicities, with a median LOS in ICU of 4 days (range 1-79). In univariate models, grade 3+ ICANS was most likely to occur in pts with active disease (≥ 5% marrow blasts and/or EMD) at the time of apheresis (OR 2.63, 1.28-5.38, p = 0.008); a numerical increase for grade 3+ CRS (OR 2.35, 0.69-8, p = 0.17) was seen in pts with active disease at apheresis. Therapies received for these CAR-related toxicities included steroids, tocilizumab (toci), and anakinra (Table 2). Among pts who received steroids (N = 94), 37% (N = 34) achieved a sufficient response to the first steroid trial and did not require subsequent therapies; otherwise, toxicities improved with the first steroid course but later worsened in 16% (N = 15); the first trial of steroids was not effective but improved when further steroids were given in 31% (N = 29); there were no responses to any doses of steroids in 10% (N = 9). In pts receiving toci (N = 103), 31% (N = 32) achieved a sufficient response to the first dose and did not require any further therapy; toxicities improved with the first dose but later worsened in 31% (N = 32); the first dose was ineffective but improvement was seen with subsequent doses in 21% (N = 22); 9% (N = 9) did not respond at all to toci. The rate of death within day +28 was 6% (N = 9), and the respective causes were typically multifactorial: CRS was implicated in 3 cases, ICANS in 3, infection in 5, disease relapse/progression in 2, and HLH in 1 case. In total, uncontrolled ICANS was implicated in the death of 6 pts (between day +9 to day +106). HLH was reported in 6 pts: in most cases, this was a biochemical diagnosis, and it either overlapped with concurrent CRS or infection or occurred following CRS/ICANS. The most common infections between day 0 and day +28 included bacteremia in 8% of pts (N = 12), fungal infections in 4% (N = 6), pneumonia in 3% (N = 5), and CMV infections in 3% (N = 4). The fungal infections included 4 instances of invasive sinopulmonary infections (2 due to aspergillus; 2 due to mucormycosis) and 2 cases of candidemia. With both CRS and ICANS treated as a time-varying covariate, the development of grade 3+ CRS was associated with a higher hazard of death (HR 2.38, 1.00-5.66, p = 0.05); grade 3+ ICANS was not associated with a demonstrably higher risk of death (HR 1.11, 0.60-2.05, p = 0.74). The HR of EFS failure for Grade 3+ CRS was 1.81 (0.87-3.79, p = 0.12) and for grade 3+ ICANS HR = 0.93 (0.56-1.53, p = 0.77). Conclusions: In this real-world study of toxicities from brexu-cel use for adults with R/R B-ALL, we observed CRS and ICANS in the majority of pts, and no new safety signals were observed. Rates of severe CRS and ICANS were more common with active disease. Interestingly, though CRS-related mortality was rare, grade 3+ CRS was associated with a higher risk of death. Efforts to identify mechanisms and mitigable risk factors for these toxicities are warranted.

Day +3/Day 0 Ferritin Ratio: A Simple Point-of-Care Index Predictive of Severe Immune Effector Cell-Associated Neurotoxicity Syndrome after CD19 CAR T-Cell Therapy

Introduction: Chimeric antigen receptor (CAR) T-cell therapy is transforming the management of patients with relapsed/refractory (R/R) B- and plasma-cell malignancies. However, a major limitation of CAR T-cell therapy is the development of severe, sometimes life-threatening, toxicities such as immune effector cell-associated neurotoxicity (ICANS) and cytokine release syndrome (CRS). While the management of CRS has dramatically improved with the early use of tocilizumab and corticosteroids, how to best predict and treat ICANS remains poorly understood, with up to 30% of patients developing severe ICANS after CD19 CAR T-cell therapy. Since we had previously observed features overlapping with hemophagocytosis lymphohistiocytosis in patients with severe CRS and ICANS, we hypothesized that the early kinetics of ferritin and soluble IL-2 receptor alpha [sIL-2Rα] post infusion could predict the development of severe ICANS. Methods: We retrospectively analyzed data from 195 patients with R/R B-cell malignancies previously treated on a phase I/II clinical trial (NCT01865617) of an investigational defined 1:1 CD8+:CD4+ composition CD19 CAR-T product (JCAR014; training set). CRS and ICANS severity were graded using Lee 2014 and CTCAE 4.03 criteria, respectively. Logistic regression was used to predict the occurrence of severe ICANS. Ferritin was measured using an enzyme immunoassay. sIL-2Rα was measured using Luminex®. Goodness of fit was assessed using the Akaike information criterion (AIC). Independent test set included 203 patients treated at our center with the standard-of-care CD19 CAR T-cell products axicabtagene or lisocabatagene maraleucel. Discrimination and calibration were assessed in both the training and test set. Results: In the training set (n=195), median age was 55 (range: 20-76). Disease type was as follows: acute lymphoblastic leukemia, n=64 (32.8%); B-cell non-Hodgkin lymphoma, n=82 (42.1%); chronic lymphocytic leukemia, n= 47 (24.1%). We observed any grade and grade ≥3 CRS in 134 (68.7%) and 27 (13.8%), respectively, and any grade and grade ≥3 ICANS in 72 (38.8%) and 37 (19.0%), respectively. Longitudinal analyses of serum ferritin (Figure 1) and sIL-2Rα values using locally estimated scatterplot smoothing suggested that the rate of increase of both analytes was markedly higher in patients with grade ≥3 ICANS compared to grade 0-2 ICANS. We applied univariate logistic regression to estimate the association between serum ferritin levels at early timepoints, select ratios of ferritin and sIL-2Rα values, and the occurrence of severe ICANS. The strongest association was observed between the ferritin day +3/day 0 ratio and severe ICANS (OR per log10 increase, 175; 95% CI, 19.1-2668; p &amp;lt; 0.001). We could further improve our model by modeling the ferritin day +3/day 0 ratio with a restricted cubic spline to allow for non-linear effects (unsplined model, AIC = 129, C-index, 0.74; splined model, AIC = 127, C-index, 0.78). Ferritin day +3/day 0 ratios of 3, 5, and 10 were associated with an 81%, 95%, and 99% probability of grade ≥3 ICANS, respectively (Figure 2). The splined model was associated with near-perfect calibration corrected for optimism using bootstrapping. We next evaluated the predictive ability of the ferritin day +3/day 0 ratio to predict severe ICANS in our independent test set. Predictions in the test set based on our splined model retained good discriminative ability with a C-index of 0.64, although with suboptimal calibration. In a refitted logistic regression model in the test set, the ferritin day +3/day 0 ratio remained strongly associated with the development of severe ICANS (OR = 18.8 per log10 increase, 95%CI, 2.48-142.01, p = 0.004). Conclusion: We validated the ability of a simple point-of-care index (day +3/day 0 ferritin ratio) to predict the development of severe ICANS after CD19 CAR T-cell therapy in our training and test set. Since serum ferritin levels can be quickly measured by most clinical laboratories, the day +3/day 0 ferritin ratio could become a practical and useful tool for practitioners taking care of CAR T-cell patients. The early identification of patients at high risk of developing severe ICANS days prior to symptoms onset could enable the evaluation of targeted prophylactic interventions in future clinical trials. We plan to refine our modeling approach to further improve the calibration in test set.

Immune Effector Cell-Associated Hemophagocytic Lymphohistiocytosis-like Syndrome (IEC-HS): A Review of Pharmacovigilance

Background: CAR-T cell therapies have revolutionized cancer therapeutics with durable responses in hematologic malignancies. However, toxicities such as cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS) are well-established off-target effects of CAR-T therapy. Immune effector cell (IEC) therapy can result in hemophagocytic lymphohistiocytosis (HLH)-like events, which are now understood as separate entities. Rare and fatal, HLH is characterized by abnormal activation of natural killer (NK) cells, macrophages, and cytotoxic T-lymphocytes; this leads to supraphysiologic production of cytokines and immune-mediated organ system damage. Expert consensus review defines IEC-HS as the development of pathologic features of HLH/macrophage activation independent from CRS and ICANS attributed to IEC therapy, including new onset or worsening cytopenia, hyperferritinemia (&amp;gt;2 times the upper limit of normal), coagulopathy with hypofibrinogenemia, and elevated transaminases. Few clinical studies have shown IEC-HS in Acute Lymphocytic Leukemia (ALL), especially in the pediatric and adolescent populations. However, the incidence and risk of IEC-HS exposure to CD19 and BCMA CAR-T are yet to be determined in B-cell lymphomas and Myelomas. The FDA Adverse Event Reporting System (FAERS) contains circumstantial case reports and serious post-CAR-T therapy IEC-HS. This retrospective analysis from the FAERS aims to address these questions and estimate the risk of IEC-HS with CAR-T cell therapies. Methods: FAERS is a publicly accessible database of adverse event reports associated with various therapies, including CAR-T cell therapies. To estimate the risk of HLH-like syndrome associated with CAR-T treatment, we analyzed the reporting of four CD19 CAR-T therapies (Axicabtagene Ciloleucel, Brexucabtagene Autoleucel, Tisagenlecleucel, and Lisocabtagene Maraleucel) and BCMA CAR-T (Idecabtagene Vicleucel) from the database between 2016 and 2023. Statistical analysis involved a disproportionality analysis using a reported odds ratio (ROR). OpenVigil, a software package used to analyze pharmacovigilance data, enabled the calculation of the ROR with a 95% confidence interval (CI). ROR greater than one, p&amp;lt;0.05, and a confidence interval not including one was considered significant. Results: Between 2016 and April 2023, the FAERS database recorded 8,302 CD19 CAR-T therapies (axicabtagene ciloleucel, n = 4,496; brexucabtagene autoleucel, n = 713; tisagenlecleucel n = 27,51; lisocabtagene maraleucel; n = 342) and 472 BCMA CAR-T therapies, Idecabtagene Vicleucel. We identified 177 reported HLH events as the primary events in patients receiving CAR-T therapies (CD19 CAR-T n = 165; BCMA n = 12). Thirty-six (20.3%) were reported as single IEC-HS, 96 (54.2%) as combined IEC-HS and CRS, 9 (5.1%) as combined IEC-HS and ICANS, and 36 (20.3%) as having all three IEC-related toxicities. The median age was 57 (4-89) years, and males &amp;gt; females at a ratio of 2:1. The study's limitation is that medical personnel reported most of the adverse events (n = 166 of 177 [94%]), and it is unclear if the diagnosis of IEC-HS followed current diagnostic criteria. The CD19 CAR-T was primarily associated with B-cell lymphomas (n = 104, 60.0%), followed by R/R ALL (n= 39, 22.0%) and Chronic Lymphocytic Leukemia, CLL (n = 3, 1.7%). Their combined elevated risk for IEC-HS was greater than that of patients in the database who had not been exposed [ROR, 63.6; 95% CI 54.7-74.1] [p&amp;lt;0.001]. In addition, we conducted a stratified analysis for each drug. Tisagenlecleucel had the highest risk for IEC-HS among the CD19 CAR-T drugs [ROR, 82.3; 95% CI 65.5-104.0] [p&amp;lt;0.001]. The risk was also significant with Idecabtagene Vicleucel [ROR, 73.5; 95% CI 41.4-130.5]. Overall, the results of the study indicate a strong association between CAR-T cell therapy exposure and IEC-HS. Conclusion: CAR-T cell therapy poses a risk for rare IEC-HS, CRS, and ICANS, necessitating early detection to minimize morbidity and mortality. The study's results will be compared to the institutional patient cohort for annual meeting. Understanding factors contributing to this rare complication is crucial for optimizing patient outcomes and ensuring safe CAR T cell therapy use.

Efficacy and Safety in Patients with Lenalidomide-Refractory Multiple Myeloma after 1-3 Prior Lines Who Received a Single Infusion of Ciltacabtagene Autoleucel As Study Treatment in the Phase 3 CARTITUDE-4 Trial

Introduction: CARTITUDE-4 (NCT04181827) is a randomized, phase 3 trial comparing ciltacabtagene autoleucel (cilta-cel), a BCMA-directed CAR-T cell therapy, with standard of care (SOC; pomalidomide, bortezomib, and dexamethasone [PVd] or daratumumab, pomalidomide, and dexamethasone [DPd]) in patients (pts) with lenalidomide (len)-refractory multiple myeloma (MM). The trial recently showed that pts in the cilta-cel arm experienced significantly improved progression-free survival (PFS) vs SOC (HR, 0.26; P&amp;lt;0.0001) and a significantly higher rate of complete response (CR) or better and overall response rate (ORR) in the intent-to-treat (ITT) set (San-Miguel et al, New Engl J Med 2023). We report efficacy and safety in pts who received cilta-cel as study treatment (‘as-treated’ set) in the experimental (cilta-cel) arm of the study. Methods: Pts had 1-3 prior lines of therapy (LOT), including a proteasome inhibitor and immunomodulatory drug. A single cilta-cel infusion (target dose, 0.75×10 6 CAR+ viable T cells/kg) was administered after apheresis, bridging therapy (DPd [28-day cycles] or PVd [21-day cycles]), and lymphodepletion. Treatment responses and disease progression were assessed per IMWG criteria; minimal residual disease (MRD) negativity at 10 -5 was assessed by next-generation sequencing starting at day 56 post infusion; time-to-event endpoints were analyzed using the Kaplan-Meier method. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS) were graded per ASTCT criteria; other adverse events (AEs) were graded per NCI-CTCAE criteria. Results: As of Nov 1, 2022, 176 of 208 pts randomized to the cilta-cel arm had received cilta-cel as study treatment (median age, 61 years; 34% with 1 prior LOT; 6% ISS stage III; 60% with high-risk cytogenetic profile; 17% with soft tissue plasmacytoma; 13% with high tumor burden; 11% triple-class refractory). Baseline characteristics were consistent with those of the ITT set. In the as-treated set, median follow-up from randomization was 16 months (mo), and 22% of pts had received 1 bridging therapy cycle, 59% 2 cycles, and 18% 3 cycles. Disease burden was effectively controlled in the as-treated set during bridging therapy. Median PFS was not reached and the 12-mo PFS rate from infusion was 85%; 12-mo overall survival rate from infusion was 92%. 175 of 176 pts who received cilta-cel as study treatment responded (99% ORR), including 86% who achieved ≥CR. Median time from randomization to first response was 2.1 mo and responses deepened over time; 2% of pts achieved ≥CR by 2 mo post randomization, and rates increased to 40% by 6 mo and 80% by 12 mo (Figure A). Median duration of response was not reached. 72% of the as-treated set (88% of 144 MRD evaluable) achieved MRD negativity at any time. 111 of 144 MRD-evaluable pts (77%) achieved both MRD negativity and ≥CR. These pts had improved PFS vs pts who remained MRD positive and/or had &amp;lt;CR (HR, 0.36; 95% CI, 0.15-0.88; P=0.0196); respective 12-mo PFS rates were 89% and 71% (Figure B). The most common CAR-T cell-related toxicity was CRS (76% any grade [gr]; 1% gr 3). The overall CAR-T cell neurotoxicity rate was 21% (3% gr 3/4). ICANS occurred in 5% of pts (no gr 3/4). Other neurotoxicities occurred in 17% of pts (2% gr 3/4); these included cranial nerve palsy (CNP) in 9% (1% gr 3/4), peripheral neuropathy in 3% (1% gr 3/4), and 1 pt with gr 1 movement/neurocognitive treatment-emergent AEs (MNT). By clinical cut-off, CRS and ICANS had resolved in all pts; CNP and peripheral neuropathy had resolved in all but 2 pts; and the 1 MNT case had not yet resolved. Conclusions: This analysis of the as-treated set in CARTITUDE-4 shows potent effects of cilta-cel in pts with len-refractory MM after 1-3 LOT. The PFS rate of 85% at 12 mo post infusion (89% in pts with MRD-negative ≥CR) compares favorably with real-world data in similar populations (12-mo PFS rate &amp;lt;50%; Lecat et al, Front Oncol 2021). Effective bridging therapy during the CAR-T manufacturing period may help ensure that pts can receive cilta-cel. In the context of longer-term data from cohort A of the CARTITUDE-2 study (Hillengass et al, ASH 2023, submitted) in a similar pt population, these results support the potential for prolonged disease control and the benefit of cilta-cel for pts with MM as early as after first relapse.

T-Cell Engaging Antibodies in Diffuse Large B Cell Lymphoma-An Update.

Novel cellular immunotherapies such as T-cell engaging antibodies (TCEAbs) are changing the landscape of treatment for diffuse large B cell lymphoma (DLBCL), especially in the relapsed/refractory (R/R) setting. TCEAbs harness the power of the host immune system to induce killing of tumor cells by binding to both the tumor antigen and the T-cell receptor. Since the approval of blinatumomab for R/R acute lymphoblastic leukemia, there has been significant development in novel TCEAbs. Many of these novel TCEAbs have shown promising effectiveness in R/R DLBCL, with favorable response rates including complete remissions, even in heavily pretreated patients. There are unique therapy-related toxicities with TCEAbs, namely cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS), and it is important to both recognize and manage these side effects appropriately. This review examines the development and mechanism of action of these TCEAbs, and the available published data from clinical trials. Their role in the treatment of DLBCL, the management of therapy-related adverse events, and the mechanisms of resistance will also be discussed.

Single center experience of using Anakinra prophylactically at Day 0 to reduce CD19 CART toxicities.

e19503 Background: Chimeric antigen receptor (CAR) T-cell therapy targeting CD19 is an effective line of the treatment for relapsed/refractory CD19 B cell cancers, however navigating Cytokine Release Syndrome (CRS) and Immune effector Cell-Associated Neurotoxicity (ICANS) still remains a challenging task. Corticosteroids and Tocilizumab are currently the mainstay treatment for toxicities but Anakinra, an IL-1 receptor antagonist has also been successfully used to treat patients receiving CART who develop CRS/ICANS. In this study we set out to describe the utility of prophylactic use of Anakinra in patients receiving CART. Methods: We conducted a single center retrospective analysis of patients who received Anakinra for CRS and ICANS prophylaxis per institutional protocol. Patient data including demographics, cancer history, CRS &amp; ICANS American Society for Transplantation and Cellular Therapy Grades, toxicity treatment history and outcomes during their hospitalization were extracted from our medical records. Institutional review board approval was obtained for this review. Results: A total of 19 patients {Diffuse Large B Cell Lymphoma = 10, Follicular = 2,Mantle cell = 2 and Acute Lymphoblastic Leukemia (ALL) = 5} were enrolled in our cohort. The median age of the patients at the time of T cell infusion was 63 years (range, 26-75). CD19 CAR products included Axicabtagene ciloleucel (8 pts; 42.1%), Brexucabtagene autoleucel (6 pts; 31.5%) and Tisagenlecleucel (5 pts; 26.3%). CRS of all grades was observed in 13 patients (68.4%) with severe CRS (grade 3-4) observed in 1 patient (5.2%) (grade 4;12 days). Median CRS duration was 3 days (range, 1-18). Median max CRS grade was observed for 2 days (range, 1-12). Median time to CRS was 5 days (range; 1-8). ICANS of all grades was observed in 12 patients (63.1%), with severe ICANS (grade3-4) in 5 patients (26.3%) {1 patient with grade 4 for 12 days; 4 patients with grade 3 for a median of 2 days (range;1-4)}. Median time to ICANS was 6 days (range, 1-11). Tocilizumab and corticosteroids were used in 9 patients (47.3%) and 11 patients (57.8%), respectively. Median starting day of Tocilizumab and steroid was on day 4(range, 1-6) and day4 (range, 1-21) respectively. Median dose of Tocilizumab was 2 (range, 1-3). Median dose of total Dexamethasone and Methylprednisolone use was 125mg (range, 10-276) and 3.92 g (range, 3-7.4) respectively for a median of 6 cumulative days (range, 1-22). Three patients (15.7%) required ICU transfer with a median stay of 5 days (range, 4-16). 1 patient died of Neurotoxicity on Day 27(Mantle cell) and 2 ALL patients died due to progression after discharge on Day61 and 256. Conclusions: We observed that prophylactically starting Anakinra at Day 0 appeared to improve CRS and ICANS toxicities in patients receiving CART. Further prospective investigations with larger population pools would be required to better understand its role in CAR T toxicity suppression.

Pre-existing frontal lobe dysfunction signs as predictors of subsequent neurotoxicity in CAR T cell therapy: insights from a case series.

Chimeric Antigen Receptor (CAR) T cell therapies are innovative treatments against hematological malignancies, with increasing therapeutic indications. Despite their great efficacy, these therapies are hampered by high rates of neurotoxicity (immune effector cell-associated neurotoxicity (ICANS)). In the past few years, several risk factors have been associated with ICANS and grouped together in the attempt to build validated models able to predict neurologic complications. However, little is known about pre-existing neurologic conditions possibly related to the development of neurotoxicity. In our case series, including sixteen consecutive patients treated with CAR T cells, we observed that (i) neurotoxicity only occurred in the two patients who presented subtle clinical signs of frontal lobe impairment at baseline and (ii) neurologic manifestations of ICANS consisted of language disturbances and cortical frontal myoclonus, which were both manifestations of a frontal predominant dysfunction. Based on our experience, we suggest that a pre-existing frontal lobe impairment, even if at a subclinical level, may eventually drive to ICANS, which in turn shows symptoms compatible with a frontal encephalopathy. It is remarkable that this focal neurotoxicity involved the same CNS regions that were responsible of subtle neurological signs at baseline. Future studies on larger numbers of patients are needed to confirm the possible role of baseline frontal lobe dysfunction as a predictor of ICANS, in order to enhance efforts to safely deliver CAR T cell therapy.

Thrombotic Events Are Unusual Toxicities of Chimeric Antigen Receptor T-Cell Therapies.

Chimeric antigen receptor (CAR) T-cell therapy has greatly transformed the treatment and prognosis of B-cell hematological malignancies. As CAR T-cell therapy continues to be more readily adopted and indications increase, the field's recognition of emerging toxicities will continue to grow. Among the adverse events associated with CAR T-cell therapy, cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS) are the most common toxicities, while thrombotic events represent an under-reported, life-endangering complication. To determine thrombosis incidence post CAR T-cell therapy, we performed a multi-center, retrospective study on CAR T-cell therapy adult patients (N = 140) from Indiana University Simon Cancer Center and the University of North Carolina Medical Center treated from 2017 to 2022 for relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL, N = 3), diffuse large B-cell lymphoma (DLBCL, N = 92), follicular lymphoma (FL, N = 9), mantle cell lymphoma (MCL, N = 2), and multiple myeloma (MM, N = 34). We report 10 (7.14%) thrombotic events related to CAR T-cell therapy (DLBCL: N = 8, FL: N = 1, MM: N = 1) including 9 primary venous events and 1 arterial event that occurred with median time of 23.5 days post CAR T-cell infusion. In search of parameters associated with such events, we performed multivariate analyses of coagulation parameters (i.e., PT, PTT, and D-Dimer), scoring for adverse events (Padua Score and ISTH DIC Score) and grading for CAR T-cell toxicity severity (CRS grade and ICANS grade) and found that D-Dimer peak elevation and ICANS grade were significantly associated with post-CAR T-cell infusion thrombosis. While the pathophysiology of CAR T-cell associated coagulopathy remains unknown, our study serves to develop awareness of these emerging and unusual complications.

Targeted Treatment of Relapsed or Refractory Follicular Lymphoma: Focus on the Therapeutic Potential of Mosunetuzumab.

Follicular lymphoma is the most common indolent non-Hodgkin's lymphoma, and because of the incurable nature of this disorder, new therapies are constantly needed. The recently approved T-cell-dependent bispecific antibody mosunetuzumab showed promising results and manageable toxicities for patients with relapsed or refractory follicular lymphoma. Namely, as opposed to cellular immunotherapy options, this agent has the potential of being effective in patients with unfavorable features with a tolerable rate and severity of cytokine release syndrome, immune effector cell-associated neurotoxicity, and infectious complications. Given the recent withdrawal from the market of PI3K inhibitors and the practical challenges in utilizing with chimeric antigen receptor T-cells (CAR-T) for some patients, mosunetuzumab represents a "breath of fresh air" for both patients and hemato-oncologists. More data are required to better define the real potential of this molecule, either alone or in combination with other agents, including antibody drug conjugates, immunomodulators, and checkpoint inhibitors. Future studies will also shed light on the efficacy of mosunetuzumab compared with CAR-T, in well-designed registries or ideally in randomized controlled trials.

Impact of Bridging Therapy on Infectious Complications Post CAR T-Cell Therapy: The UT Southwestern Experience

Background: CAR T-cell therapy (CAR T) has become a powerful new tool in the treatment of relapsed/refractory (r/r) hematologic malignancies. Infections are well-recognized risks of CAR T. Bridging therapy is often employed to allow patients to reach successful infusion but may also further immunosuppress this already vulnerable group. This study aims to identify patterns of infections post-CAR T and the potential impact of bridging therapy. Methods: Medical records of patients who underwent apheresis for CAR T from 2018-2022 for r/r lymphomas or multiple myeloma (MM) at UT Southwestern were analyzed. Demographics, treatment characteristics and infection data were collected via retrospective chart review. Post-CAR T infections were identified by reviewing patient hospitalizations after CAR T infusion for infectious complications confirmed by positive diagnostic studies during admission. Infections were categorized as bacterial, viral, fungal, or multi-pathogenic. Time-to-infection was calculated from lymphodepletion (LD) date. Categorical variables were compared using Fisher's exact test. Continuous variables were compared using Mann-Whitney U test. Overall- and progression-free survival (OS and PFS) were calculated from CAR T infusion date, estimated by the Kaplan-Meier method, and compared using a log-rank test. Results: Data were collected on 75 total patients, 44 with lymphoma and 31 with MM, who underwent apheresis and 74 (98.7%) underwent CAR T. Baseline patient characteristics are shown in Table 1. All patients received standardized opportunistic infection (OI) prophylaxis and intravenous immunoglobulin (IVIG) and growth factor support based on institutional guidelines. Thirty-eight patients (51%) had a post-CAR T infection. Post-CAR T infections manifested at a median of 117 days (range: 12 - 1344 days) after LD. Patients who received bridging therapy had an earlier median incidence of post CAR T infections (92 vs 113 days post-LD, p = 0.03). Number of prior lines of therapy did not predict infection rates or time to infection. Time-to-infection did not vary by lymphoma versus MM or by cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity (ICANS) grade. MM patients had a numerically higher rate of viral infections (77% vs 41%) while lymphoma patients had a higher bacterial infection rate (65% vs 55%). A majority (58%) of these patients had infectious events between 31- and 100-days post lymphodepletion [Figure 2]. Infection rates were not significantly associated with tocilizumab or steroid usage during CAR T. In our cohort, 77% of patients received bridging. Bridging therapy was associated with a significantly higher neutropenic fever rate (73% vs 37%, p = 0.006), which persisted after adjusting for prior lines of therapy. All patients with neutropenic fever received broad-spectrum antibiotic coverage. In lymphoma patients, bridging therapy was associated with higher grades of CRS (p = 0.018). Being hospitalized for infection within 6 months (p=0.01) or receiving antibiotics in the month (p=0.02) prior to lymphodepletion, were associated with grade ≥3 CRS. One-year PFS and OS were 55% and 74% for the entire cohort. Four patients died due to infectious complications after successful CAR T infusion at a median of 163 days post infusion. Patients who had post-CAR T infections trended towards worse progression-free survival (1-year PFS 65% vs 46%, p = 0.1) and had similar OS (1-year OS 70% vs 77%, p = 0.75). Conclusions: Bridging therapy prior to CAR T may increase the risk of neutropenic fever and be associated with earlier infectious risk. Febrile neutropenia and high-grade CRS drive more intensive resource utilization, which may be mitigated with more intentional patient selection for bridging therapy.Our findings show that post-CAR T infections contribute to significant morbidity, and thus calls for personalizing bridging strategies, peri-CAR T OI prophylaxis and infection management. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Phase 2/3, Randomized, Double Blind, Placebo-Controlled, Multicenter Study of NKTR-255 Vs Placebo Following CD-19 Directed CAR-T Therapy in Patients with Relapsed/Refractory Large B-Cell Lymphoma

Background: Autologous T cells engineered to express a CD19-directed chimeric antigen receptor (CAR) have shown high overall response rates in treatment-refractory CD19+ B-cell non-Hodgkin lymphoma (NHL). However, over half of these patients will have lymphoma that fails to achieve remission or will relapse; thus, strategies to further improve the long-term efficacy of CAR-T cell products are needed. NKTR-255 is a novel investigational polymer-conjugated IL-15 agonist, designed to activate, proliferate and expand natural killer (NK) and CD8+ T-cells in vivo. NKTR-255 also promotes the survival and expansion of memory CD8+ T cells. Preclinical data in B-cell lymphoma xenograft models have shown that NKTR-255 enhanced expansion, survival, and anti-tumor activity of human CD19 CAR-T cells. Further, clinical studies have demonstrated that NKTR-255 promoted CD8+ T cell expansion in patients with relapsed/refractory (r/r) NHL who previously received CAR-T cell therapy (NCT04136756). Here, we describe a planned Phase 2/3 clinical trial of NKTR-255 following CAR-T cell therapy. Methods: This is a phase 2/3, randomized, double blind, placebo-controlled, multicenter study of NKTR-255 vs placebo following CD-19 directed CAR-T therapy. Eligible patients who have r/r large B-cell lymphoma and are planned for treatment with an FDA-approved CAR-T product (axi-cel or liso-cel) will be enrolled. All patients will receive initial study drug administration of NKTR-255 intravenously, starting approximately 14 days following CAR-T therapy, with continued dosing every 21 days. The study will be comprised of two stages: 1) Phase 2: patients will be randomized to placebo or one of multiple dose cohorts of NKTR-255 (Stage 1) and 2) Phase 3: patients will be randomized to placebo or the selected NKTR-255 dose regimen (Stage 2). The primary objective for Stage 1 is to identify the dose of NKTR-255 for the Phase 3 part of the study based on the safety and tolerability of NKTR-255 as well as the complete response rate (CRR) at month 6. The primary efficacy endpoints of Stage 2 are CRR at month 6 and event-free survival. Efficacy analyses will be performed separately for Stage 1 and Stage 2. Efficacy, as measured by PET-CT, will be evaluated according to the Lugano Criteria (Cheson 2014). The key eligibility criteria following CD19 targeted CAR-T cell infusion include no grade ≥ 1 cytokine release syndrome (CRS) on the day of NKTR-255 administration, no grade ≥ 3 CRS within 72 hours proceeding NKTR-255 administration, no grade ≥ 3 immune effector cell-associated neurotoxicity (ICANS) of > 72 hours duration, no grade ≥ 2 ICANS on the day of NKTR-255 infusion and no tocilizumab and/or dexamethasone within 48 hours proceeding NKTR-255 administration. Conclusions: Based on preclinical and clinical evidence, NKTR-255 has the potential to improve efficacy of currently approved cellular therapies. This trial evaluates safety and efficacy of NKTR-255 following commercial CD19 CAR-T therapy to enhance antitumor effect and durability of responses. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Impact of High Disease Burden on Survival in Pediatric Patients with B-ALL Treated with Tisagenlecleucel

CD19-specific chimeric antigen receptor (CAR) T-cell therapies, including the FDA-approved tisagenlecleucel, induce high rates of remission in pediatric patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, post-treatment relapse remains an issue. Optimal management of B-ALL after tisagenlecleucel treatment remains elusive, and continued tracking of outcomes is necessary to establish a standard of care for this population. We sought to evaluate outcomes on the real-world use of tisagenlecleucel in a contemporary pediatric patient population and to identify risk factors influencing event-free survival (EFS) and overall survival (OS). Additionally, we aimed to describe post-tisagenlecleucel management strategies, including use of allogeneic hematopoietic cell transplantation (AlloHCT) or repeat CAR T-cell infusions. We report on 31 pediatric and adolescent and young adult patients (AYA) with B-ALL, treated with lymphodepleting chemotherapy followed by tisagenlecleucel. Patients were treated at Johns Hopkins Hospital and St. Jude Children's Research Hospital between March 2018 and November 2020. Data on patient, disease, and treatment characteristics were collected retrospectively from medical records and described. EFS and OS were estimated by the Kaplan-Meier method and compared by the log-rank test. Single-factor and multiple-factor analysis of EFS and OS were performed by fitting Cox regression models. Of the 30 evaluable patients, 25 (83.3%) experienced a complete response, with 21 having negative minimal residual disease. Treatment was well tolerated, with expected rates of cytokine release syndrome (61.3%) and immune effector cell-associated neurotoxicity (29%). After initial complete response, 12 patients (48%) had subsequent disease recurrence, with CD19-negative relapse (n=6) occurring sooner than CD19-positive relapse (P = .0125). With a median follow-up time of 386 days (range 11-1187 days), the EFS for the entire cohort (n = 31) at 6 and 12 months after infusion was 47% (95% confidence interval [CI], 28.4%-63.4%) and 35.2% (95% CI, 18.4%-52.5%), respectively. In multivariate analysis, high pretreatment leukemic burden (≥5% bone marrow blasts) was an independent risk factor for inferior EFS (HR 5.98 [95% CI, 1.1-32.4], P=.0380) and OS (HR 4.2 [95% CI, 1.33-13.39], P=.0148). Tisagenlecleucel induced high initial response rates in a contemporary cohort of pediatric and AYA patients with B-ALL. However, 48% of patients experienced subsequent disease relapse, including 6 with antigen-escape variants. This highlights a considerable limitation of single-agent autologous CD19-CAR T-cell therapy. Pretreatment leukemic disease burden of ≥5% blasts was significantly associated with worse outcomes in this study, including lower EFS and OS. Our findings suggest that reducing preinfusion leukemic burden is a viable treatment strategy to improve outcomes of CAR T-cell therapy.