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Tisagenlecleucel is a chimeric antigen receptor–T cell therapy that facilitates the killing of CD19+ B cells. A model was developed for the kinetics of tisagenlecleucel and the impact of therapies for treating cytokine release syndrome (tocilizumab and corticosteroids) on expansion. Data from two phase II studies in pediatric and young adult relapsed/refractory B cell acute lymphoblastic leukemia were pooled to evaluate this model and evaluate extrinsic and intrinsic factors that may impact the extent of tisagenlecleucel expansion. The doubling time, initial decline half‐life, and terminal half‐life for tisagenlecleucel were 0.78, 4.3, and 220 days, respectively. No impact of tocilizumab or corticosteroids on the expansion rate was observed. This work represents the first mixed‐effect model‐based analysis of chimeric antigen receptor–T cell therapy and may be clinically impactful as future studies examine prophylactic interventions in patients at risk of higher grade cytokine release syndrome and the effects of these interventions on chimeric antigen receptor–T cell expansion.

Virus-specific T cells (VST) from partially-HLA matched donors have been effective for treatment of refractory viral infections in immunocompromised patients in prior studies with a good safety profile, but rare adverse events have been described. Here we describe a unique and severe adverse event of VST therapy in an infant with severe combined immunodeficiency, who receives, as part of a clinical trial (NCT03475212), third party VSTs for treating cytomegalovirus viremia following bone marrow transplantation. At one-month post-VST infusion, rejection of graft and reversal of chimerism is observed, as is an expansion of T cells exclusively from the VST donor. Single-cell gene expression and T cell receptor profiling demonstrate a narrow repertoire of predominantly activated CD4 + T cells in the recipient at the time of rejection, with the repertoire overlapping more with that of peripheral blood from VST donor than the infused VST product. This case thus demonstrates a rare but serious side effect of VST therapy. Infusion of virus-specific T (VST) cells is used for treating drug-resistant viremia. Here the authors report, as part of the clinical trial, NCT03475212, a lethal case of unexpected bone marrow graft loss and chimerism reversal that is induced by the infusion of third-party VST intended to treat transplantation-related cytomegalovirus viremia.

BackgroundTisagenlecleucel, an anti-CD19 chimeric antigen receptor T cell therapy, has demonstrated efficacy in children and young adults with relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL) in two multicenter phase 2 trials (ClinicalTrials.gov, NCT02435849 (ELIANA) and NCT02228096 (ENSIGN)), leading to commercialization of tisagenlecleucel for the treatment of patients up to age 25 years with B-ALL that is refractory or in second or greater relapse.MethodsA pooled analysis of 137 patients from these trials (ELIANA: n=79; ENSIGN: n=58) was performed to provide a comprehensive safety profile for tisagenlecleucel.ResultsGrade 3/4 tisagenlecleucel-related adverse events (AEs) were reported in 77% of patients. Specific AEs of interest that occurred ≤8 weeks postinfusion included cytokine-release syndrome (CRS; 79% (grade 4: 22%)), infections (42%; grade 3/4: 19%), prolonged (not resolved by day 28) cytopenias (40%; grade 3/4: 34%), neurologic events (36%; grade 3: 10%; no grade 4 events), and tumor lysis syndrome (4%; all grade 3). Treatment for CRS included tocilizumab (40%) and corticosteroids (23%). The frequency of neurologic events increased with CRS severity (p<0.001). Median time to resolution of grade 3/4 cytopenias to grade ≤2 was 2.0 (95% CI 1.87 to 2.23) months for neutropenia, 2.4 (95% CI 1.97 to 3.68) months for lymphopenia, 2.0 (95% CI 1.87 to 2.27) months for leukopenia, 1.9 (95% CI 1.74 to 2.10) months for thrombocytopenia, and 1.0 (95% CI 0.95 to 1.87) month for anemia. All patients who achieved complete remission (CR)/CR with incomplete hematologic recovery experienced B cell aplasia; however, as nearly all responders also received immunoglobulin replacement, few grade 3/4 infections occurred >1 year postinfusion.ConclusionsThis pooled analysis provides a detailed safety profile for tisagenlecleucel during the course of clinical trials, and AE management guidance, with a longer follow-up duration compared with previous reports.

We analyzed late cardiovascular outcomes of 661 patients who survived at least 2 years from hematopoietic cell transplantation for childhood hematologic malignancy between 1995 and 2008. Center for International Blood and Marrow Transplant Research data was supplemented with surveys focused on cardiotoxicity and potential risk factors. The median duration of follow-up was 97 months (range 24–230). 4.2% of survivors experienced at least one of the primary outcomes including coronary artery disease (0.2%), cerebrovascular accident (0.6%), cardiomyopathy (3%), and cardiac-related death (0.5%). Patients who received anthracycline chemotherapy (HR 4.67, p  = 0.036) or cranial or chest radiation (HR 5.58, p  < 0.0001; HR 2.18, p  = 0.0087) were at increased risk for developing one of the primary outcomes. Dyslipidemia was diagnosed in 18% of survivors. Pre-transplant anthracycline (HR 1.74, p  < 0.0001) and chest radiation (HR 1.34, p  = 0.0371) were risk factors for dyslipidemia. Overweight/obese body mass status was present in 63% of patients at baseline, 65% at 2 years, and 52% at most recent evaluation. Diabetes was diagnosed in 7% of subjects. In conclusion, severe cardiovascular complications were infrequently reported. The incidence of risk factors including obesity and dyslipidemia were significant and will likely increase the risk of cardiovascular disease over time in transplant survivors.

Patient-derived T cells genetically reprogrammed to express CD19-specific chimeric antigen receptors (CARs) have shown remarkable clinical responses and are commercially available for the treatment of patients with certain advanced-stage B cell malignancies. Nonetheless, several trials have revealed pre-existing and/or treatment-induced immune responses to the mouse-derived single-chain variable fragments included in these constructs. These responses might have contributed to both treatment failure and the limited success of redosing strategies observed in some patients. Data from early phase clinical trials suggest that CAR T cells are also associated with immunogenicity-related events in patients with solid tumours. Generally, the clinical implications of anti-CAR immune responses are poorly understood and highly variable between different CAR constructs and malignancies. These observations highlight an urgent need to uncover the mechanisms of immunogenicity in patients receiving CAR T cells and develop validated assays to enable clinical detection. In this Review, we describe the current clinical evidence of anti-CAR immune responses and discuss how new CAR T cell technologies might impact the risk of immunogenicity. We then suggest ways to reduce the risks of anti-CAR immune responses to CAR T cell products that are advancing towards the clinic. Finally, we summarize measures that investigators could consider in order to systematically monitor and better comprehend the possible effects of immunogenicity during trials involving CAR T cells as well as in routine clinical practice.CD19-specific chimeric antigen (CAR)-modified T cells are approved for patients with advanced-stage forms of certain B cell malignancies. However, a subset of patients will have anti-CAR immune responses, leading to a lack of CAR T cell persistence and a rapid loss of any antitumour efficacy. In this Review, the authors describe the extent of anti-CAR immune responses in patients and suggest measures that could be used to better monitor for these events. Additionally, they describe novel approaches to CAR T cell therapy that might reduce the risk of such responses in the future.

Relapse following CD19‐targeting chimeric antigen receptor T‐cell therapy (CD19‐CAR) remains a major barrier to long‐term cure in relapsed/refractory B‐cell acute lymphoblastic leukemia, with nearly 50% of patients relapsing within 6 months. Early B‐cell recovery (BCR), as detected by the re‐emergence of CD19‐positive cells, has been strongly associated with relapse risk and serves as a surrogate marker for loss of CAR T‐cell persistence. However, clinical use of BCR is hindered by variability in monitoring practices, including inconsistent definitions, timing, and measurement across institutions. To address this gap, we convened an international working group of pediatric cellular therapy experts to establish a consensus definition for BCR. Our collaborative effort outlines standardized criteria for BCR assessment aimed at improving comparability across studies and guiding post‐CAR T‐cell surveillance strategies.

Down syndrome-associated acute lymphoblastic leukemia (DS-ALL) patients suffer risk of chemotherapy-associated toxicities and poor outcomes. We evaluated tisagenlecleucel in 16 patients with DS-ALL in two phase 2 trials (ELIANA [NCT02435849], ENSIGN [NCT02228096]) and a phase 3b, managed access protocol (B2001X [NCT03123939]). Patients were 5–22 years old, had a median of two prior lines of therapy (range, 1–4), and four (25%) had prior stem cell transplants. Fourteen of 16 patients (88%) achieved complete remission (CR) or CR with incomplete blood count recovery (CRi); 12 of 14 (86%) with CR/CRi were minimal residual disease-negative. With a median follow-up of 13.2 months (range, 0.5–49.3 months), six patients (43%) relapsed after CR (three, CD19-negative; three, unknown) between 80–721 days post-infusion. Ongoing remissions in nine patients ranged from 6–48 months. Any-grade and grade 3/4 AEs occurred in 16 and 14 patients, respectively; 44% experienced grade 3/4 cytokine release syndrome and 13% experienced grade 3/4 neurological events. Grade 3/4 prolonged cytopenias occurred in 44% of patients. No grade 3/4 infections were observed. Tisagenlecleucel expansion and long-term persistence were consistent with previous reports. Comparable to ALL patients without DS, tisagenlecleucel produced high remission rates, manageable side-effects, and promising long-term outcomes in pediatric/young adult patients with DS-ALL.Plain Language SummaryChildren with Down syndrome have a 20 times higher risk of developing a type of blood cancer called Down syndrome-associated acute lymphoblastic leukemia (ALL). Children who develop Down syndrome-associated ALL typically receive chemotherapy to treat their cancer; however, they can experience severe toxicity or other consequences from these therapies, especially stem cell transplant, and have a poor prognosis if their disease returns after treatment. These children need an effective but less toxic treatment option. Tisagenlecleucel is a chimeric antigen receptor-T cell therapy that specially modifies the patient’s own T-cells to recognize and attack the cancer cells. Tisagenlecleucel is approved for use in children and young adults with ALL whose disease reappears after two or more treatments or whose disease doesn’t respond to treatment. Here we present data from 16 patients across three clinical studies showing that tisagenlecleucel is well-tolerated and an effective treatment option for children and young adults with Down syndrome-associated ALL, and was similar to what is observed in patients without Down syndrome. Taken together, patients with Down syndrome-associated ALL have unique medical needs, and tisagenlecleucel may help them live longer, avoid stem cell transplantation, and the toxicity from chemotherapy.

An analysis of outcomes from 2000 through 2009 at 25 centers treating children with severe combined immunodeficiency (SCID) showed that early transplantation of hematopoietic cells in uninfected children had the best outcome, regardless of donor type. Severe combined immunodeficiency (SCID) is a genetically heterogeneous and lethal disorder of infancy. It is characterized by severe T-cell lymphocytopenia and a lack of antigen-specific T-cell and B-cell immune responses. 1 Allogeneic hematopoietic-cell transplantation with the use of bone marrow from an HLA-identical sibling 2 or an unrelated donor, 3 T-cell–depleted marrow or peripheral-blood stem cells from a haploidentical, related donor, 4 – 7 or umbilical-cord blood 8 – 10 can fully correct the T-cell deficiency and, less consistently, the B-cell deficiency in patients with SCID. 2 – 12 Expanded donor availability and advances in supportive care and treatment of infections have improved long-term outcomes after hematopoietic-cell transplantation. 10 , . . .

In this study of unrelated-donor transplantation for hematologic cancers, survival was similar with bone marrow and peripheral-blood stem-cell grafts. However, graft failure was more common with the former, and chronic graft-versus-host disease with the latter. In the early days of allogeneic hematopoietic stem-cell transplantation, the only graft source available was bone marrow harvested from the pelvis of a donor under anesthesia. When studies showed that an increased dose of bone marrow cells correlated with more robust hematopoietic engraftment and lower mortality from infectious complications, transplantation centers began to use filgrastim-stimulated peripheral blood, which has a much higher content of blood progenitor cells than bone marrow, although there was concern that the higher T-cell content might increase the risk of graft-versus-host disease (GVHD). 1 – 5 Several large, randomized trials of transplantation between HLA-identical siblings showed that peripheral-blood . . .

As clinical advances with chimeric antigen receptor (CAR) T cells are increasingly described and the potential for extending their therapeutic benefit grows, optimizing the implementation of this therapeutic modality is imperative. The recognition and management of cytokine release syndrome (CRS) marked a milestone in this field; however, beyond the understanding gained in treating CRS, a host of additional toxicities and/or potential late effects of CAR T cell therapy warrant further investigation. A multicentre initiative involving experts in paediatric cell therapy, supportive care and/or study of late effects from cancer and haematopoietic stem cell transplantation was convened to facilitate the comprehensive study of extended CAR T cell-mediated toxicities and establish a framework for new systematic investigations of CAR T cell-related adverse events. Together, this group identified six key focus areas: extended monitoring of neurotoxicity and neurocognitive function, psychosocial considerations, infection and immune reconstitution, other end organ toxicities, evaluation of subsequent neoplasms, and strategies to optimize remission durability. Herein, we present the current understanding, gaps in knowledge and future directions of research addressing these CAR T cell-related outcomes. This systematic framework to study extended toxicities and optimization strategies will facilitate the translation of acquired experience and knowledge for optimal application of CAR T cell therapies.A host of additional toxicities and/or potential late effects of chimeric antigen receptor (CAR) T cell therapy beyond cytokine release syndrome (CRS) warrant further investigation. Herein, experts in paediatric cell therapy, supportive care and/or study of late effects from cancer and haematopoietic stem cell transplantation present six key focus research areas related to CAR T cell-related outcomes beyond CRS.