Search

Background: Adoptive cell therapy, such as chimeric antigen receptor (CAR)-T cell therapy, has improved patient outcomes for hematological malignancies. Currently, four of the six FDA-approved CAR-T cell products use the FMC63-based αCD19 single-chain variable fragment, derived from a murine monoclonal antibody, as the extracellular binding domain. Clinical studies demonstrate that patients develop humoral and cellular immune responses to the non-self CAR components of autologous CAR-T cells or donor-specific antigens of allogeneic CAR-T cells, which is thought to potentially limit CAR-T cell persistence and the success of repeated dosing., Methods: In this study, we implemented a one-shot approach to prevent rejection of engineered T cells by simultaneously reducing antigen presentation and the surface expression of both Classes of the major histocompatibility complex (MHC) via expression of the viral inhibitors of transporter associated with antigen processing (TAPi) in combination with a transgene coding for shRNA targeting class II MHC transactivator (CIITA). The optimal combination was screened in vitro by flow cytometric analysis and mixed lymphocyte reaction assays and was validated in vivo in mouse models of leukemia and lymphoma. Functionality was assessed in an autologous setting using patient samples and in an allogeneic setting using an allogeneic mouse model., Results: The combination of the Epstein-Barr virus TAPi and an shRNA targeting CIITA was efficient and effective at reducing cell surface MHC classes I and II in αCD19 'stealth' CAR-T cells while retaining in vitro and in vivo antitumor functionality. Mixed lymphocyte reaction assays and IFNγ ELISpot assays performed with T cells from patients previously treated with autologous αCD19 CAR-T cells confirm that CAR T cells expressing the stealth transgenes evade allogeneic and autologous anti-CAR responses, which was further validated in vivo. Importantly, we noted anti-CAR-T cell responses in patients who had received multiple CAR-T cell infusions, and this response was reduced on in vitro restimulation with autologous CARs containing the stealth transgenes., Conclusions: Together, these data suggest that the proposed stealth transgenes may reduce the immunogenicity of autologous and allogeneic cellular therapeutics. Moreover, patient data indicate that repeated doses of autologous FMC63-based αCD19 CAR-T cells significantly increased the anti-CAR T cell responses in these patients., Competing Interests: Competing interests: KG, MJF, and MVM are inventors of patents related to the stealth technologies described here. CJT has received research funding from Juno Therapeutics, BMS, and Nektar Therapeutics and has the right to receive royalties from Fred Hutch as an inventor on patents related to CAR-T cell therapy that are licensed to Juno Therapeutics/BMS. CJT holds equity in Precision Biosciences, Eureka Therapeutics, Caribou Biosciences, Myeloid Therapeutics, and ArsenalBio, serves on Scientific Advisory Boards of Precision Biosciences, Eureka Therapeutics, Caribou Biosciences, T-CURX, Myeloid Therapeutics, ArsenalBio and Century Therapeutics, and serves on ad hoc advisory boards (last 12 months) of Genentech, GlaxoSmithKline and Decheng Capital. MVM is an inventor on patents related to adoptive cell therapies, held by Massachusetts General Hospital and the University of Pennsylvania (some licensed to Novartis). MVM holds equity in TCR2, Century Therapeutics, Genocea, Oncternal, and Neximmune, serves on the Board of Directors of 2Seventy Bio, and has served as a consultant for multiple companies involved in cell therapies. MVM’s interests were reviewed and are managed by Massachusetts General Hospital, and Mass General Brigham in accordance with their conflict-of-interest policies., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Based on a deterministic and stochastic process hybrid model, we use white noises to account for patient variabilities in treatment outcomes, use a hyperparameter to represent patient heterogeneity in a cohort, and construct a stochastic model in terms of Ito stochastic differential equations for testing the efficacy of three different treatment protocols in CAR T cell therapy. The stochastic model has three ergodic invariant measures which correspond to three unstable equilibrium solutions of the deterministic system, while the ergodic invariant measures are attractors under some conditions for tumor growth. As the stable dynamics of the stochastic system reflects long-term outcomes of the therapy, the transient dynamics provide chances of cure in short-term. Two stopping times, the time to cure and time to progress, allow us to conduct numerical simulations with three different protocols of CAR T cell treatment through the transient dynamics of the stochastic model. The probability distributions of the time to cure and time to progress present outcome details of different protocols, which are significant for current clinical study of CAR T cell therapy., Competing Interests: Declaration of competing interest There is non-financial interest in this research., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Abstract: More than half of the patients treated with CD19-targeted chimeric antigen receptor (CAR) T-cell immunotherapy for large B-cell lymphoma (LBCL) do not achieve durable remission, which may be partly due to PD-1/PD-L1-associated CAR T-cell dysfunction. We report data from a phase 1 clinical trial (NCT02706405), in which adults with LBCL were treated with autologous CD19 CAR T cells (JCAR014) combined with escalating doses of the anti-PD-L1 monoclonal antibody, durvalumab, starting either before or after CAR T-cell infusion. The addition of durvalumab to JCAR014 was safe and not associated with increased autoimmune or immune effector cell-associated toxicities. Patients who started durvalumab before JCAR014 infusion had later onset and shorter duration of cytokine release syndrome and inferior efficacy, which was associated with slower accumulation of CAR T cells and lower concentrations of inflammatory cytokines in the blood. Initiation of durvalumab before JCAR014 infusion resulted in an early increase in soluble PD-L1 (sPD-L1) levels that coincided with the timing of maximal CAR T-cell accumulation in the blood. In vitro, sPD-L1 induced dose-dependent suppression of CAR T-cell effector function, which could contribute to inferior efficacy observed in patients who received durvalumab before JCAR014. Despite the lack of efficacy improvement and similar CAR T-cell kinetics early after infusion, ongoing durvalumab therapy after JCAR014 was associated with re-expansion of CAR T cells in the blood, late regression of CD19+ and CD19- tumors, and enhanced duration of response. Our results indicate that the timing of initiation of PD-L1 blockade is a key variable that affects outcomes after CD19 CAR T-cell immunotherapy for adults with LBCL., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Antibodies against foreign human leukocyte antigen (HLA) molecules are barriers to successful organ transplantation. B cell-depleting treatments are used to reduce anti-HLA antibodies but have limited efficacy. We hypothesized that the primary source for anti-HLA antibodies is long-lived plasma cells, which are ineffectively targeted by B cell depletion. To study this, we screened for anti-HLA antibodies in a prospectively enrolled cohort of 49 patients who received chimeric antigen receptor T-cell therapy (CARTx), targeting naïve and memory B cells (CD19-targeted, n = 21) or plasma cells (BCMA-targeted, n = 28) for hematologic malignancies. Longitudinal samples were collected before and up to 1 year after CARTx. All individuals were in sustained remission. We identified 4 participants with anti-HLA antibodies before CD19-CARTx. Despite B cell depletion, anti-HLA antibodies and calculated panel reactive antibody scores were stable for 1 year after CD19-CARTx. Only 1 BCMA-CARTx recipient had pre-CARTx low-level anti-HLA antibodies, with no follow-up samples available. These data implicate CD19 neg long-lived plasma cells as an important source for anti-HLA antibodies, a model supported by infrequent HLA sensitization in BCMA-CARTx subjects receiving previous plasma cell-targeted therapies. Thus, plasma cell-targeted therapies may be more effective against HLA antibodies, thereby enabling improved access to organ transplantation and rejection management., (Copyright © 2022 American Society of Transplantation & American Society of Transplant Surgeons. Published by Elsevier Inc. All rights reserved.)

CD19-targeted chimeric antigen receptor-engineered (CD19 CAR) T cells are novel therapies showing great promise for patients with relapsed or refractory (R/R) aggressive B-cell non-Hodgkin lymphoma (B-NHL). Single-arm studies showed significant variations in outcomes across distinct CD19 CAR T-cell products. To estimate the independent impact of the CAR T-cell product type on outcomes, we retrospectively analyzed data from 129 patients with R/R aggressive B-NHL treated with cyclophosphamide and fludarabine lymphodepletion followed by either a commercially available CD19 CAR T-cell therapy (axicabtagene ciloleucel [axicel] or tisagenlecleucel [tisacel]), or the investigational product JCAR014 on a phase 1/2 clinical trial (NCT01865617). After adjustment for age, hematopoietic cell transplantation-specific comorbidity index, lactate dehydrogenase (LDH), largest lesion diameter, and absolute lymphocyte count (ALC), CAR T-cell product type remained associated with outcomes in multivariable models. JCAR014 was independently associated with lower cytokine release syndrome (CRS) severity compared with axicel (adjusted odds ratio [aOR], 0.19; 95% confidence interval [CI]; 0.08-0.46), with a trend toward lower CRS severity with tisacel compared with axicel (aOR, 0.47; 95% CI, 0.21-1.06; P = .07). Tisacel (aOR, 0.17; 95% CI, 0.06-0.48) and JCAR014 (aOR, 0.17; 95% CI, 0.06-0.47) were both associated with lower immune effector cell-associated neurotoxicity syndrome severity compared with axicel. Lower odds of complete response (CR) were predicted with tisacel and JCAR014 compared with axicel. Although sensitivity analyses using either positron emission tomography- or computed tomography-based response criteria also suggested higher efficacy of axicel over JCAR014, the impact of tisacel vs axicel became undetermined. Higher preleukapheresis LDH, largest lesion diameter, and lower ALC were independently associated with lower odds of CR. We conclude that CD19 CAR T-cell product type independently impacts toxicity and efficacy in R/R aggressive B-NHL patients., (© 2022 by The American Society of Hematology.)

CD19-targeted chimeric antigen receptor (CAR) T-cell therapy has demonstrated remarkable efficacy in patients with relapsed/refractory B-cell malignancies; however, it is associated with toxicities including cytokine release syndrome (CRS), neurotoxicity, and impaired hematopoietic recovery. The latter is associated with high-grade cytopenias requiring extended growth factor or transfusional support, potentially leading to additional complications such as infection or hemorrhage. To date, the factors independently associated with hematologic toxicity have not been well characterized. To address this deficit, we retrospectively analyzed 173 patients who received defined-composition CD19 CAR T-cell therapy in a phase 1/2 clinical trial (https://clinicaltrials.gov; NCT01865617), with primary end points of absolute neutrophil count and platelet count at day-28 after CAR T-cell infusion. We observed cumulative incidences of neutrophil and platelet recovery of 81% and 75%, respectively, at 28 days after infusion. Hematologic toxicity was noted in a significant subset of patients, with persistent neutropenia in 9% and thrombocytopenia in 14% at last follow-up. Using debiased least absolute shrinkage selector and operator regression analysis for high-dimensional modeling and considering patient-, disease-, and treatment-related variables, we identified increased CRS severity as an independent predictor for decreased platelet count and lower prelymphodepletion platelet count as an independent predictor of both decreased neutrophil and platelet counts after CD19 CAR T-cell infusion. Furthermore, multivariable models including CRS-related cytokines identified associations between higher peak serum concentrations of interleukin-6 and lower day-28 cell counts; in contrast, higher serum concentrations of transforming growth factor-β1 were associated with higher counts. Our findings suggest that patient selection and improved CRS management may improve hematopoietic recovery after CD19 CAR T-cell therapy., (© 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

The relative efficacy of autologous hematopoietic cell transplant (auto-HCT) vs chimeric antigen receptor T-cell (CAR-T) therapy in patients with diffuse large B-cell lymphoma (DLBCL) who achieve a partial remission (PR) after salvage chemotherapy is not known. Using the Center for International Blood & Marrow Transplant Research registry database, we identified adult patients with DLBCL who received either an auto-HCT (2013-2019) or CAR-T treatment with axicabtagene ciloleucel (2018-2019) while in a PR by computed tomography or positron emission tomography scan. We compared the clinical outcomes between the 2 cohorts using univariable and multivariable regression models after adjustment for relevant baseline and clinical factors. In the univariable analysis, the 2-year progression-free survival (52% vs 42%; P = .1) and the rate of 100-day nonrelapse mortality (4% vs 2%; P = .3) were not different between the 2 cohorts, but consolidation with auto-HCT was associated with a lower rate of relapse/progression (40% vs 53%; P = .05) and a superior overall survival (OS) (69% vs 47%; P = .004) at 2 years. In the multivariable regression analysis, treatment with auto-HCT was associated with a significantly lower risk of relapse/progression rate (hazard ratio = 1.49; P = .01) and a superior OS (hazard ratio = 1.63; P = .008). In patients with DLBCL in a PR after salvage therapy, treatment with auto-HCT was associated with a lower incidence of relapse and a superior OS compared with CAR-T. These data support the role of auto-HCT as the standard of care in transplant-eligible patients with relapsed DLBCL in PR after salvage therapy., (© 2022 by The American Society of Hematology.)

Purpose: We previously identified mesothelin (MSLN) as highly expressed in a significant fraction of acute myeloid leukemia (AML) but entirely silent in normal hematopoiesis, providing a promising antigen for immunotherapeutic targeting that avoids hematopoietic toxicity. Given that T cells genetically modified to express chimeric antigen receptors (CAR) are effective at eradicating relapsed/refractory acute lymphocytic leukemia, we developed MSLN-directed CAR T cells for preclinical evaluation in AML., Experimental Design: The variable light (VL) and heavy (VH) sequences from the MSLN-targeting SS1P immunotoxin were used to construct the single-chain variable fragment of the standard CAR containing 41-BB costimulatory and CD3Zeta stimulatory domains. The preclinical efficacy of MSLN CAR T cells was evaluated against AML cell lines and patient samples expressing various levels of MSLN in vitro and in vivo ., Results: We demonstrate that MSLN is expressed on the cell surface of AML blasts and leukemic stem cell-enriched CD34 + CD38 - subset, but not on normal hematopoietic stem and progenitor cells (HSPC). We further establish that MSLN CAR T cells are highly effective in eliminating MSLN-positive AML cells in cell line- and patient-derived xenograft models. Importantly, MSLN CAR T cells can target and eradicate CD34 + CD38 - cells without impacting the viability of normal HSPCs. Finally, we show that CAR T-cell functionality can be improved by inhibition of the ADAM17 metalloprotease that promotes shedding of MSLN., Conclusions: These findings demonstrate that MSLN is a viable target for CAR T-cell therapy in AML and that inhibiting MSLN shedding is a promising approach to improve CAR T-cell efficacy., (©2021 The Authors; Published by the American Association for Cancer Research.)

BACKGROUNDLittle is known about pathogen-specific humoral immunity after chimeric antigen receptor-modified T (CAR-T) cell therapy for B cell malignancies.METHODSWe conducted a prospective cross-sectional study of CD19-targeted or B cell maturation antigen-targeted (BCMA-targeted) CAR-T cell therapy recipients at least 6 months posttreatment and in remission. We measured pathogen-specific IgG against 12 vaccine-preventable infections and the number of viral and bacterial epitopes to which IgG was detected ("epitope hits") using a serological profiling assay. The primary outcome was the proportion of participants with IgG levels above a threshold correlated with seroprotection for vaccine-preventable infections.RESULTSWe enrolled 65 children and adults a median of 20 months after CD19- (n = 54) or BCMA- (n = 11) CAR-T cell therapy. Among 30 adults without IgG replacement therapy (IGRT) in the prior 16 weeks, 27 (90%) had hypogammaglobulinemia. These individuals had seroprotection to a median of 67% (IQR, 59%-73%) of tested infections. Proportions of participants with seroprotection per pathogen were comparable to population-based studies, but most individuals lacked seroprotection to specific pathogens. Compared with CD19-CAR-T cell recipients, BCMA-CAR-T cell recipients were half as likely to have seroprotection (prevalence ratio, 0.47; 95% CI, 0.18-1.25) and had fewer pathogen-specific epitope hits (mean difference, -90 epitope hits; 95% CI, -157 to -22).CONCLUSIONSeroprotection for vaccine-preventable infections in adult CD19-CAR-T cell recipients was comparable to the general population. BCMA-CAR-T cell recipients had fewer pathogen-specific antibodies. Deficits in both groups support the need for vaccine and immunoglobulin replacement therapy studies.FUNDINGSwiss National Science Foundation (Early Postdoc Mobility grant P2BSP3_188162), NIH/National Cancer Institute (NIH/NCI) (U01CA247548 and P01CA018029), NIH/NCI Cancer Center Support Grants (P30CA0087-48 and P30CA015704-44), American Society for Transplantation and Cellular Therapy, and Juno Therapeutics/BMS.

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.

Abstract: Immunotherapy with T cells engineered to express a chimeric antigen receptor (CAR T cells) is reshaping the management of patients with relapsed or refractory B-cell malignancies. High efficacy of CD19-targeted CAR T cells has been reported in children and adults with B-cell acute lymphoblastic leukemia (B-ALL), with complete responses without detectable minimal residual disease occurring in approximately 80% to 90% of patients. This led to the approval of tisagenlecleucel (Kymriah) by the Food and Drug Administration based on the results of the ELIANA trial. Although CD19 CAR T-cell therapy may be curative in children, responses are short-lived in most adult B-ALL patients. In addition, CAR T-cell therapy can be associated with severe, potentially life-threatening, toxicities, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. Here, we review the recent advances in CAR T-cell therapy for R/R B-ALL and discuss strategies to improve its efficacy while minimizing toxicities., Competing Interests: Conflicts of Interest and Source of Funding: J.G. has received consulting honoraria from JMP, Eusapharma, and Multerra Bio. C.J.T. receives research funding from Juno Therapeutics, Nektar Therapeutics, Minerva, TCR2, and AstraZeneca; is a member of scientific advisory boards and has options in Precision Biosciences, Eureka Therapeutics, Caribou Biosciences, Myeloid Therapeutics, and ArsenalBio; serves on scientific advisory boards for T-CURX and Century Therapeutics; has served on advisory boards for Nektar Therapeutics, Allogene, Kite/Gilead, Novartis, Humanigen, PACT Pharma, Amgen, and Astra Zeneca; and has patents licensed to Juno Therapeutics., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

CD19-targeted chimeric antigen receptor-engineered (CD19 CAR) T-cell therapy has shown significant efficacy for relapsed or refractory (R/R) B-cell malignancies. Yet, CD19 CAR T cells fail to induce durable responses in most patients. Second infusions of CD19 CAR T cells (CART2) have been considered as a possible approach to improve outcomes. We analyzed data from 44 patients with R/R B-cell malignancies (acute lymphoblastic leukemia [ALL], n = 14; chronic lymphocytic leukemia [CLL], n = 9; non-Hodgkin lymphoma [NHL], n = 21) who received CART2 on a phase 1/2 trial (NCT01865617) at our institution. Despite a CART2 dose increase in 82% of patients, we observed a low incidence of severe toxicity after CART2 (grade ≥3 cytokine release syndrome, 9%; grade ≥3 neurotoxicity, 11%). After CART2, complete response (CR) was achieved in 22% of CLL, 19% of NHL, and 21% of ALL patients. The median durations of response after CART2 in CLL, NHL, and ALL patients were 33, 6, and 4 months, respectively. Addition of fludarabine to cyclophosphamide-based lymphodepletion before the first CAR T-cell infusion (CART1) and an increase in the CART2 dose compared with CART1 were independently associated with higher overall response rates and longer progression-free survival after CART2. We observed durable CAR T-cell persistence after CART2 in patients who received cyclophosphamide and fludarabine (Cy-Flu) lymphodepletion before CART1 and a higher CART2 compared with CART1 cell dose. The identification of 2 modifiable pretreatment factors independently associated with better outcomes after CART2 suggests strategies to improve in vivo CAR T-cell kinetics and responses after repeat CAR T-cell infusions, and has implications for the design of trials of novel CAR T-cell products after failure of prior CAR T-cell immunotherapies., (© 2021 by The American Society of Hematology.)

Chimeric antigen receptor (CAR) T cells provide new therapeutic options for patients with relapsed/refractory hematologic malignancies. However, neurotoxicity is a frequent, and potentially fatal, complication. The spectrum of manifestations ranges from delirium and language dysfunction to seizures, coma, and fatal cerebral edema. This novel syndrome has been designated immune effector cell-associated neurotoxicity syndrome (ICANS). In this review, we draw an arc from our current understanding of how systemic and potentially local cytokine release act on the CNS, toward possible preventive and therapeutic approaches. We systematically review reported correlations of secreted inflammatory mediators in the serum/plasma and cerebrospinal fluid with the risk of ICANS in patients receiving CAR T cell therapy. Possible pathophysiologic impacts on the CNS are covered in detail for the most promising candidate cytokines, including IL-1, IL-6, IL-15, and GM-CSF. To provide insight into possible final common pathways of CNS inflammation, we place ICANS into the context of other systemic inflammatory conditions that are associated with neurologic dysfunction, including sepsis-associated encephalopathy, cerebral malaria, thrombotic microangiopathy, CNS infections, and hepatic encephalopathy. We then review in detail what is known about systemic cytokine interaction with components of the neurovascular unit, including endothelial cells, pericytes, and astrocytes, and how microglia and neurons respond to systemic inflammatory challenges. Current therapeutic approaches, including corticosteroids and blockade of IL-1 and IL-6 signaling, are reviewed in the context of what is known about the role of cytokines in ICANS. Throughout, we point out gaps in knowledge and possible new approaches for the investigation of the mechanism, prevention, and treatment of ICANS., Competing Interests: JG is a consultant for Johnson & Johnson. RP is employed by the company Shape Therapeutics but declares no overlap of commercial interests with this work. WL and CT are listed as inventors on the patent, “Biomarkers and uses thereof for selecting immunotherapy intervention”. CT receives research funding from Juno Therapeutics, Nektar Therapeutics, AstraZeneca, and TCR2 Therapeutics; serves on the Scientific Advisory Boards for Precision Biosciences, Eureka Therapeutics, Caribou Biosciences, T-CURX, Myeloid Therapeutics, ArsenalBio, and Century Therapeutics; ad hoc advisory boards (last 12 months): Nektar Therapeutics, Allogene, PACT Pharma, Astra Zeneca, Amgen; holds stock/options in Precision Biosciences, Eureka Therapeutics, Caribou Biosciences, Myeloid Therapeutics, and ArsenalBio, and holds a patent licensed to Juno Therapeutics. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Gust, Ponce, Liles, Garden and Turtle.)

In the United States the increasing number of Food and Drug Administration (FDA)-approved, innovative, and potentially effective commercial cancer therapies pose a significant financial burden on public and private payers. Chimeric antigen receptor (CAR) T cells are prototypical of this challenge. In 2017 and 2018, tisagenlecleucel (Kymriah, Novartis) and axicabtagene ciloleucel (Yescarta, Kite) were approved by the FDA for use after showing groundbreaking results in relapsed/refractory B-cell malignancies. In 2020 and 2021, four further submissions to the FDA are expected for CAR T-cell therapies for indolent and aggressive B-cell malignancies and plasma cell myeloma. Yet, with marketed prices of over $350,000 per infusion for the two FDA-approved therapies and similar price tags expected for the coming products, serious concerns are raised over value and affordability. In this review we summarize recent, peer-reviewed cost-effectiveness studies of tisagenlecleucel and axicabtagene ciloleucel in the United States; discuss key issues concerning the health plan budget impact of CAR T-cell therapy; and review policy, payment and scientific approaches that may improve the value and affordability of CAR T-cell therapy.

Introduction : The success of CD19 chimeric antigen receptor (CAR)-T cell therapy for treatment of CD19 positive malignancies has led to the FDA approval of two CD19 CAR-T cell products, tisagenlecleucel and axicabtagene ciloleucel, and ongoing clinical trials of new products. Cytokine release syndrome (CRS) and neurotoxicity are common toxicities associated with CD19 CAR-T cell therapies. Areas covered : This review will discuss CRS and neurotoxicity associated with CD19 CAR-T cell therapies, including clinical presentation, risk factors, pathophysiology, and therapeutic or prophylactic interventions. Expert opinion : In conjunction with improved understanding of the pathophysiology of CRS and neurotoxicity, we expect that the recent development of consensus guidelines for the evaluation of these toxicities will enhance management of patients undergoing CD19 CAR-T cell therapies.

We previously reported durable responses in relapsed or refractory (R/R) chronic lymphocytic leukemia (CLL) patients treated with CD19-targeted chimeric antigen receptor-engineered (CD19 CAR) T-cell immunotherapy after ibrutinib failure. Because preclinical studies showed that ibrutinib could improve CAR T cell-antitumor efficacy and reduce cytokine release syndrome (CRS), we conducted a pilot study to evaluate the safety and feasibility of administering ibrutinib concurrently with CD19 CAR T-cell immunotherapy. Nineteen CLL patients were included. The median number of prior therapies was 5, and 17 patients (89%) had high-risk cytogenetics (17p deletion and/or complex karyotype). Ibrutinib was scheduled to begin ≥2 weeks before leukapheresis and continue for ≥3 months after CAR T-cell infusion. CD19 CAR T-cell therapy with concurrent ibrutinib was well tolerated; 13 patients (68%) received ibrutinib as planned without dose reduction. The 4-week overall response rate using 2018 International Workshop on CLL (iwCLL) criteria was 83%, and 61% achieved a minimal residual disease (MRD)-negative marrow response by IGH sequencing. In this subset, the 1-year overall survival and progression-free survival (PFS) probabilities were 86% and 59%, respectively. Compared with CLL patients treated with CAR T cells without ibrutinib, CAR T cells with concurrent ibrutinib were associated with lower CRS severity and lower serum concentrations of CRS-associated cytokines, despite equivalent in vivo CAR T-cell expansion. The 1-year PFS probabilities in all evaluable patients were 38% and 50% after CD19 CAR T-cell therapy, with and without concurrent ibrutinib, respectively (P = .91). CD19 CAR T cells with concurrent ibrutinib for R/R CLL were well tolerated, with low CRS severity, and led to high rates of MRD-negative response by IGH sequencing., (© 2020 by The American Society of Hematology.)

Chimeric antigen receptor (CAR) T-cell therapy has produced remarkable anti-tumor responses in patients with B-cell malignancies. However, clonal kinetics and transcriptional programs that regulate the fate of CAR-T cells after infusion remain poorly understood. Here we perform TCRB sequencing, integration site analysis, and single-cell RNA sequencing (scRNA-seq) to profile CD8 + CAR-T cells from infusion products (IPs) and blood of patients undergoing CD19 CAR-T immunotherapy. TCRB sequencing shows that clonal diversity of CAR-T cells is highest in the IPs and declines following infusion. We observe clones that display distinct patterns of clonal kinetics, making variable contributions to the CAR-T cell pool after infusion. Although integration site does not appear to be a key driver of clonal kinetics, scRNA-seq demonstrates that clones that expand after infusion mainly originate from infused clusters with higher expression of cytotoxicity and proliferation genes. Thus, we uncover transcriptional programs associated with CAR-T cell behavior after infusion.

CD19-targeted chimeric antigen receptor-modified T cell (CAR-T cell) therapy has shown excellent antitumor activity in patients with relapsed/refractory B cell malignancies, with very encouraging response rates and outcomes. However, the late effects following this therapy remain unknown. Here we report late adverse events-defined as starting or persisting beyond 90 days after CAR-T cell infusion-in patients who survived at least 1 year after therapy. The median duration of follow-up was 28.1 months (range, 12.5 to 62.6 months). At last follow-up, 73% of patients were still alive and 24% were in ongoing complete remission (CR). The most common late adverse event was hypogammaglobulinemia (IgG <400 mg/dL or i.v immunoglobulinm (IVIG) replacement, observed in 67% of the patients with available data. Infection density was .55 infection/100 days at risk (2.08 per patient-year). The majority (80%) of the infections were treated in the outpatient setting, and 5% necessitated admission to the intensive care unit (ICU). Subsequent malignancies occurred in 15% of patients, including 5% with myelodysplastic syndrome (MDS). Among patients with ongoing CR and with no MDS, 16% experienced prolonged cytopenia requiring transfusions or growth factor support. Graft-versus-host disease occurred in 3 of 15 patients (20%) who had undergone previous allogeneic hematopoietic cell transplantation. Most of the late events observed in this cohort were not severe, and many could be related to previous or subsequent therapies, suggesting a safe long-term profile of CD19-targeted CAR-T cell immunotherapy., (Copyright © 2019 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

The long-term effects of CD19-targeted chimeric antigen receptor-modified T-cell immunotherapy (CD19-CARTx) for B-cell malignancies on humoral immunity are unclear. We examined antiviral humoral immunity in 39 adults with B-cell malignancies who achieved durable complete remission without additional therapy for >6 months after CD19-CARTx. Despite CD19+ B-cell aplasia in all patients, the incidence of viral infections occurring >90 days post-CD19-CARTx was low (0.91 infections per person-year). Because long-lived plasma cells are CD19- and should not be direct targets of CD19-targeted chimeric antigen receptor T cells, we tested the hypothesis that humoral immunity was preserved after CD19-CARTx based on linear mixed-effects models of changes in serum total immunoglobulin G (IgG) concentration, measles IgG concentration, and the number of viruses or viral epitopes to which serum IgG was directed (the "antivirome") using the novel VirScan assay. Samples were tested pre-CD19-CARTx and ∼1, 6, and 12 months post-CD19-CARTx. Although total IgG concentration was lower post-CD19-CARTx (mean change, -17.5%), measles IgG concentration was similar (mean change, 1.2%). Only 1 participant lost measles seroprotection post-CD19-CARTx but had undergone allogeneic hematopoietic cell transplantation before CD19-CARTx. The antivirome was also preserved, with mean absolute losses of 0.3 viruses and 6 viral epitopes detected between pre- and post-CD19-CARTx samples. Most participants gained IgG to ≥2 epitopes for ≥2 viruses, suggesting that humoral immunity to some viruses may be maintained or recover after successful CD19-CARTx. These findings may differ in children. Studies of immunoglobulin replacement and vaccination after CARTx are warranted., (© 2019 by The American Society of Hematology.)

Allogeneic hematopoietic cell transplantation (allo-HCT) is offered to selected patients after chimeric antigen receptor-modified T-cell (CAR-T) therapy. Lymphodepleting chemotherapy and CAR-T therapy have immunosuppressive and immunomodulatory effects that could alter the safety profile of subsequent allo-HCT. We reviewed our experience with 32 adults (acute lymphoblastic leukemia [ALL], n = 19; B-cell non-Hodgkin lymphoma [NHL]/chronic lymphocytic leukemia [CLL], n = 13) who received an allo-HCT after CAR-T therapy, with a focus on posttransplant toxicities. Myeloablative conditioning (MAC) was used in 74% of ALL patients and 39% of NHL/CLL patients. The median time from CAR-T therapy to allo-HCT was 72 days in ALL patients and 122 days in NHL/CLL patients. Cumulative incidences of grade 3-4 acute graft-versus-host disease (GVHD) and chronic GVHD were 25% and 10%, respectively. All patients had neutrophil recovery (median, 18.5 days) and all but 3 had platelet recovery (median, 12 days). Twenty-two percent had viral or systemic fungal infection within 100 days after allo-HCT. The 100-day and 1-year cumulative incidences of NRM were 16% and 21%, respectively, for ALL patients and 15% and 33%, respectively, for NHL/CLL patients. In ALL patients, later utilization of allo-HCT after CAR-T therapy was associated with higher mortality. In NHL/CLL patients, MAC was associated with higher mortality. Toxicities did not exceed the expected incidences in this high-risk population., (© 2019 by The American Society of Hematology.)

Patients with follicular lymphoma (FL) with early relapse after initial chemoimmunotherapy, refractory disease, or histologic transformation (tFL) have limited progression-free and overall survival. We report efficacy and long-term follow-up of 21 patients with relapsed/refractory (R/R) FL (n = 8) and tFL (n = 13) treated on a phase 1/2 clinical trial with cyclophosphamide and fludarabine lymphodepletion followed by infusion of 2 × 106 CD19-directed chimeric antigen receptor-modified T (CAR-T) cells per kilogram. The complete remission (CR) rates by the Lugano criteria were 88% and 46% for patients with FL and tFL, respectively. All patients with FL who achieved CR remained in remission at a median follow-up of 24 months. The median duration of response for patients with tFL was 10.2 months at a median follow-up of 38 months. Cytokine release syndrome occurred in 50% and 39%, and neurotoxicity in 50% and 23% of patients with FL and tFL, respectively, with no severe adverse events (grade ≥3). No significant differences in CAR-T cell in vivo expansion/persistence were observed between FL and tFL patients. CD19 CAR-T cell immunotherapy is highly effective in adults with clinically aggressive R/R FL with or without transformation, with durable remission in a high proportion of FL patients. This trial was registered at clinicaltrials.gov as #NCT01865617., (© 2019 by The American Society of Hematology.)

CD19-targeted chimeric antigen receptor (CAR)-modified T (CAR-T) cell immunotherapy has demonstrated impressive results in B-cell malignancies, and CAR-T cell therapies targeting other antigens are in development for other cancers. Cytokine release syndrome (CRS) and neurotoxicity can be life-threatening in a subset of patients. The severity of CRS and neurotoxicity can be impacted by the disease burden, lymphodepletion regimen, and CAR-T cell dose. Tocilizumab and corticosteroids have been used to manage these toxicities, enabling CD19 CAR-T cells to be administered without obvious compromise in efficacy. Consensus criteria for grading and managing toxicities will facilitate the widespread application of this treatment modality., (© 2019 Wiley Periodicals, Inc.)

Autologous T cells engineered to express a CD19-specific chimeric antigen receptor (CAR) have produced impressive minimal residual disease-negative (MRD-negative) complete remission (CR) rates in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, the factors associated with durable remissions after CAR T-cell therapy have not been fully elucidated. We studied patients with relapsed/refractory B-ALL enrolled in a phase 1/2 clinical trial evaluating lymphodepletion chemotherapy followed by CD19 CAR T-cell therapy at our institution. Forty-five (85%) of 53 patients who received CD19 CAR T-cell therapy and were evaluable for response achieved MRD-negative CR by high-resolution flow cytometry. With a median follow-up of 30.9 months, event-free survival (EFS) and overall survival (OS) were significantly better in the patients who achieved MRD-negative CR compared with those who did not (median EFS, 7.6 vs 0.8 months; P < .0001; median OS, 20.0 vs 5.0 months; P = .014). In patients who achieved MRD-negative CR by flow cytometry, absence of the index malignant clone by IGH deep sequencing was associated with better EFS ( P = .034). Stepwise multivariable modeling in patients achieving MRD-negative CR showed that lower prelymphodepletion lactate dehydrogenase concentration (hazard ratio [HR], 1.38 per 100 U/L increment increase), higher prelymphodepletion platelet count (HR, 0.74 per 50 000/μL increment increase), incorporation of fludarabine into the lymphodepletion regimen (HR, 0.25), and allogeneic hematopoietic cell transplantation (HCT) after CAR T-cell therapy (HR, 0.39) were associated with better EFS. These data allow identification of patients at higher risk of relapse after CAR T-cell immunotherapy who might benefit from consolidation strategies such as allogeneic HCT. This trial was registered at www.clinicaltrials.gov as #NCT01865617., (© 2019 by The American Society of Hematology.)

Neurotoxicity is an important and common complication of chimeric antigen receptor-T cell therapies. Acute neurologic signs and/or symptoms occur in a significant proportion of patients treated with CD19-directed chimeric antigen receptor-T cells for B-cell malignancies. Clinical manifestations include headache, confusion, delirium, language disturbance, seizures and rarely, acute cerebral edema. Neurotoxicity is associated with cytokine release syndrome, which occurs in the setting of in-vivo chimeric antigen receptor-T cell activation and proliferation. The mechanisms that lead to neurotoxicity remain unknown, but data from patients and animal models suggest there is compromise of the blood-brain barrier, associated with high levels of cytokines in the blood and cerebrospinal fluid, as well as endothelial activation. Corticosteroids, interleukin-6-targeted therapies, and supportive care are frequently used to manage patients with neurotoxicity, but high-quality evidence of their efficacy is lacking.

Chimeric antigen receptor (CAR) T-cell immunotherapy has revolutionized the treatment of refractory leukemias and lymphomas, but is associated with significant toxicities, namely cytokine release syndrome (CRS) and neurotoxicity. A major barrier to developing therapeutics to prevent CAR T cell-mediated neurotoxicity is the lack of clinically relevant models. Accordingly, we developed a rhesus macaque (RM) model of neurotoxicity via adoptive transfer of autologous CD20-specific CAR T cells. Following cyclophosphamide lymphodepletion, CD20 CAR T cells expand to 272 to 4,450 cells/μL after 7 to 8 days and elicit CRS and neurotoxicity. Toxicities are associated with elevated serum IL6, IL8, IL1RA, MIG, and I-TAC levels, and disproportionately high cerebrospinal fluid (CSF) IL6, IL2, GM-CSF, and VEGF levels. During neurotoxicity, both CD20 CAR and non-CAR T cells accumulate in the CSF and in the brain parenchyma. This RM model demonstrates that CAR T cell-mediated neurotoxicity is associated with proinflammatory CSF cytokines and a pan-T cell encephalitis. Significance: We provide the first immunologically relevant, nonhuman primate model of B cell-directed CAR T-cell therapy-mediated CRS and neurotoxicity. We demonstrate CAR and non-CAR T-cell infiltration in the CSF and in the brain during neurotoxicity resulting in pan-encephalitis, accompanied by increased levels of proinflammatory cytokines in the CSF. Cancer Discov; 8(6); 750-63. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 663 ., (©2018 American Association for Cancer Research.)

T-cells engineered to express CD19-specific chimeric antigen receptors (CD19 CAR-T cells) can achieve high response rates in patients with refractory/relapsed (R/R) CD19+ hematologic malignancies. Nonetheless, the efficacy of CD19-specific CAR-T cell therapy can be offset by significant toxicities, such as cytokine release syndrome (CRS) and neurotoxicity. In this report of our presentation at the 2018 Second French International Symposium on CAR-T cells (CAR-T day), we describe the clinical presentations of CRS and neurotoxicity in a cohort of 133 adults treated with CD19 CAR-T cells at the Fred Hutchinson Cancer Research Center, and provide insights into the mechanisms contributing to these toxicities., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Lymphodepletion chemotherapy followed by infusion of CD19-targeted chimeric antigen receptor-modified T (CAR-T) cells can be complicated by neurologic adverse events (AE) in patients with refractory B-cell malignancies. In 133 adults treated with CD19 CAR-T cells, we found that acute lymphoblastic leukemia, high CD19 + cells in bone marrow, high CAR-T cell dose, cytokine release syndrome, and preexisting neurologic comorbidities were associated with increased risk of neurologic AEs. Patients with severe neurotoxicity demonstrated evidence of endothelial activation, including disseminated intravascular coagulation, capillary leak, and increased blood-brain barrier (BBB) permeability. The permeable BBB failed to protect the cerebrospinal fluid from high concentrations of systemic cytokines, including IFNγ, which induced brain vascular pericyte stress and their secretion of endothelium-activating cytokines. Endothelial activation and multifocal vascular disruption were found in the brain of a patient with fatal neurotoxicity. Biomarkers of endothelial activation were higher before treatment in patients who subsequently developed grade ≥4 neurotoxicity. Significance: We provide a detailed clinical, radiologic, and pathologic characterization of neurotoxicity after CD19 CAR-T cells, and identify risk factors for neurotoxicity. We show endothelial dysfunction and increased BBB permeability in neurotoxicity and find that patients with evidence of endothelial activation before lymphodepletion may be at increased risk of neurotoxicity. Cancer Discov; 7(12); 1404-19. ©2017 AACR. See related commentary by Mackall and Miklos, p. 1371 This article is highlighted in the In This Issue feature, p. 1355 ., (©2017 American Association for Cancer Research.)

Lymphodepletion chemotherapy followed by infusion of CD19-specific chimeric antigen receptor-modified (CAR) T cells has produced impressive antitumor responses in patients with refractory CD19 + B-cell malignancies but is often associated with cytokine release syndrome (CRS). Our understanding of CRS continues to evolve, and identification of the kinetics of CRS and predictive clinical and laboratory biomarkers of severity are needed to evaluate strategies to mitigate toxicity. We report the clinical presentation of and identify biomarkers of severe CRS in 133 adult patients who received CD19 CAR T cells. CRS developed in 70% of patients, including 62.5% with grade 1 to 3 CRS (grade 1, 26%; grade 2, 32%; grade 3, 4.5%), 3.8% with grade 4, and 3.8% with grade 5. A majority of cases of grade ≥4 CRS occurred during CAR T-cell dose finding. Multivariable analysis of baseline characteristics identified high marrow tumor burden, lymphodepletion using cyclophosphamide and fludarabine, higher CAR T-cell dose, thrombocytopenia before lymphodepletion, and manufacturing of CAR T cells without selection of CD8 + central memory T cells as independent predictors of CRS. Severe CRS was characterized by hemodynamic instability, capillary leak, and consumptive coagulopathy. Angiopoietin-2 and von Willebrand factor, which are biomarkers of endothelial activation, were increased during severe CRS and also before lymphodepletion in patients who subsequently developed CRS. We describe a classification-tree algorithm to guide studies of early intervention after CAR T-cell infusion for patients at high risk of severe CRS. These data provide a framework for early intervention studies to facilitate safer application of effective CD19 CAR T-cell therapy., (© 2017 by The American Society of Hematology.)

Purpose We evaluated the safety and feasibility of anti-CD19 chimeric antigen receptor-modified T (CAR-T) cell therapy in patients with chronic lymphocytic leukemia (CLL) who had previously received ibrutinib. Methods Twenty-four patients with CLL received lymphodepleting chemotherapy and anti-CD19 CAR-T cells at one of three dose levels (2 × 10 5 , 2 × 10 6 , or 2 × 10 7 CAR-T cells/kg). Nineteen patients experienced disease progression while receiving ibrutinib, three were ibrutinib intolerant, and two did not experience progression while receiving ibrutinib. Six patients were venetoclax refractory, and 23 had a complex karyotype and/or 17p deletion. Results Four weeks after CAR-T cell infusion, the overall response rate (complete response [CR] and/or partial response [PR]) by International Workshop on Chronic Lymphocytic Leukemia (IWCLL) criteria was 71% (17 of 24). Twenty patients (83%) developed cytokine release syndrome, and eight (33%) developed neurotoxicity, which was reversible in all but one patient with a fatal outcome. Twenty of 24 patients received cyclophosphamide and fludarabine lymphodepletion and CD19 CAR-T cells at or below the maximum tolerated dose (≤ 2 × 10 6 CAR-T cells/kg). In 19 of these patients who were restaged, the overall response rate by IWCLL imaging criteria 4 weeks after infusion was 74% (CR, 4/19, 21%; PR, 10/19, 53%), and 15/17 patients (88%) with marrow disease before CAR-T cells had no disease by flow cytometry after CAR-T cells. Twelve of these patients underwent deep IGH sequencing, and seven (58%) had no malignant IGH sequences detected in marrow. Absence of the malignant IGH clone in marrow of patients with CLL who responded by IWCLL criteria was associated with 100% progression-free survival and overall survival (median 6.6 months follow-up) after CAR-T cell immunotherapy. The progression-free survival was similar in patients with lymph node PR or CR by IWCLL criteria. Conclusion CD19 CAR-T cells are highly effective in high-risk patients with CLL after they experience treatment failure with ibrutinib therapy.

Background: T cells that have been modified to express a CD19-specific chimeric antigen receptor (CAR) have antitumor activity in B cell malignancies; however, identification of the factors that determine toxicity and efficacy of these T cells has been challenging in prior studies in which phenotypically heterogeneous CAR-T cell products were prepared from unselected T cells., Methods: We conducted a clinical trial to evaluate CD19 CAR-T cells that were manufactured from defined CD4+ and CD8+ T cell subsets and administered in a defined CD4+:CD8+ composition to adults with B cell acute lymphoblastic leukemia after lymphodepletion chemotherapy., Results: The defined composition product was remarkably potent, as 27 of 29 patients (93%) achieved BM remission, as determined by flow cytometry. We established that high CAR-T cell doses and tumor burden increase the risks of severe cytokine release syndrome and neurotoxicity. Moreover, we identified serum biomarkers that allow testing of early intervention strategies in patients at the highest risk of toxicity. Risk-stratified CAR-T cell dosing based on BM disease burden decreased toxicity. CD8+ T cell-mediated anti-CAR transgene product immune responses developed after CAR-T cell infusion in some patients, limited CAR-T cell persistence, and increased relapse risk. Addition of fludarabine to the lymphodepletion regimen improved CAR-T cell persistence and disease-free survival., Conclusion: Immunotherapy with a CAR-T cell product of defined composition enabled identification of factors that correlated with CAR-T cell expansion, persistence, and toxicity and facilitated design of lymphodepletion and CAR-T cell dosing strategies that mitigated toxicity and improved disease-free survival., Trial Registration: ClinicalTrials.gov NCT01865617., Funding: R01-CA136551; Life Science Development Fund; Juno Therapeutics; Bezos Family Foundation.

Administration of lymphodepletion chemotherapy followed by CD19-specific chimeric antigen receptor (CAR)-modified T cells is a remarkably effective approach to treating patients with relapsed and refractory CD19(+) B-cell malignancies. We treated 7 patients with B-cell acute lymphoblastic leukemia (B-ALL) harboring rearrangement of the mixed lineage leukemia (MLL) gene with CD19 CAR-T cells. All patients achieved complete remission (CR) in the bone marrow by flow cytometry after CD19 CAR-T-cell therapy; however, within 1 month of CAR-T-cell infusion, 2 of the patients developed acute myeloid leukemia (AML) that was clonally related to their B-ALL, a novel mechanism of CD19-negative immune escape. These reports have implications for the management of patients with relapsed and refractory MLL-B-ALL who receive CD19 CAR-T-cell therapy., (© 2016 by The American Society of Hematology.)

The ability to engineer T cells to recognize tumor cells through genetic modification with a synthetic chimeric antigen receptor has ushered in a new era in cancer immunotherapy. The most advanced clinical applications are in targeting CD19 on B-cell malignancies. The clinical trials of CD19 chimeric antigen receptor therapy have thus far not attempted to select defined subsets before transduction or imposed uniformity of the CD4 and CD8 cell composition of the cell products. This review will discuss the rationale for and challenges to using adoptive therapy with genetically modified T cells of defined subset and phenotypic composition.

Adoptive transfer of tumor-reactive T cells into cancer patients with the intent of inducing a cytotoxic anti-tumor effector response and durable immunity has long been proposed as a novel therapy for a broad range of malignancies; however, local and systemic tolerance mechanisms have hindered the generation of effective T cell therapies and limited the clinical efficacy of this approach in cancer patients. Chimeric antigen receptors (CARs) are recombinant receptors that comprise an extracellular antigen-targeting domain in conjunction with one or more intracellular T cell signaling domains that can be introduced into T cells by genetic modification to redirect their specificity to the CAR-targeted antigen. Administration of CD19-specific CAR-modified T cells that target B cell non-Hodgkin lymphomas and leukemia has been remarkably effective in recent clinical trials, energizing the field and stimulating new efforts to identify the critical parameters of CAR design and T cell engineering that are necessary for effective cancer therapy.

Recent advances enabling efficient delivery of transgenes to human T cells have created opportunities to address obstacles that previously hindered the application of T cell therapy to cancer. Modification of T cells with transgenes encoding TCRs or chimeric antigen receptors allows tumor specificity to be conferred on functionally distinct T cell subsets, and incorporation of costimulatory molecules or cytokines can enable engineered T cells to bypass local and systemic tolerance mechanisms. Clinical studies of genetically modified T cell therapy for cancer have shown notable success; however, these trials demonstrate that tumor therapy with engineered high avidity tumor-reactive T cells may be accompanied by significant on-target toxicity, necessitating careful selection of target antigens and development of strategies to eliminate transferred cells., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The observation that T cells can recognize and specifically eliminate cancer cells has spurred interest in the development of efficient methods to generate large numbers of T cells with specificity for tumor antigens that can be harnessed for use in cancer therapy. Recent studies have demonstrated that during encounter with tumor antigen, the signals delivered to T cells by professional antigen-presenting cells can affect T-cell programming and their subsequent therapeutic efficacy. This has stimulated efforts to develop artificial antigen-presenting cells that allow optimal control over the signals provided to T cells. In this review, we will discuss the advantages and disadvantages of cellular and acellular artificial antigen-presenting cell systems and their use in T-cell adoptive immunotherapy for cancer.

Dendritic cells (DCs) loaded with tumor-associated antigens are a promising treatment to prevent disease relapse in patients with multiple myeloma (MM). Early-phase clinical trials have shown safety, efficacy, and immunologic responses in MM, but a key issue now is the isolation of a functional, clinically relevant DC preparation. The authors have described a unique blood DC (BDC) isolation platform based on positive immunoselection with the CMRF-56 antibody. To validate this as a feasible source of BDCs for immunotherapy, the authors undertook a quantitative and functional analysis of BDCs in MM patients and healthy donors. These data show that MM patients have similar numbers of CD11c+CD16+ and CD11c+CD16- BDCs but about half the number of CD11c-CD123+ BDCs in whole blood compared with healthy donors. BDCs could be isolated by CMRF-56+ immunoselection from all MM patients tested, with similar yields and purity to healthy donors. These BDCs could be activated ex vivo with poly I:C or LPS. Furthermore, CMRF-56+ preparations could induce potent CD4+ and CD8+ T-lymphocyte responses in both MM patients and healthy donors. These data suggest that BDCs with in vitro functional integrity can be isolated from MM patients in sufficient numbers to justify a clinical trial.

Dendritic cells (DC) for cancer immunotherapy protocols are generated most commonly by in vitro differentiation of monocytes with exogenous cytokines (Mo-DC). However, Mo-DC differ in their molecular phenotype and function from blood DC (BDC). Clinical isolation of BDC has been limited to the use of density gradients, which result in low yields of variable purity. We have developed a DC enrichment platform, which uses the CMRF-44 (IgM) or CMRF-56 (IgG) monoclonal antibodies (mAb) to select BDC that express these antigens after a short overnight incubation. After culture of peripheral blood mononuclear cells (PBMC) in autologous/AB serum, biotinylated CMRF-44 was used to select DC in a single step immuno-magnetic bead procedure; this produced populations containing up to 99% CMRF-44(+) cells, including up to 67% CMRF-44(+) CD14(-) CD19(-) DC, from an initial starting population of approximately 0.5%. We observed consistent differences in the purities obtained from individual donors with a mean of 54% CMRF-44(+) cells (range 19-99%). Similar results were obtained using biotinylated CMRF-56 mAb, an antibody identifying a comparable population in cultured PBMC. We recovered an average of 54% and 66% of the available BDC in separations performed with the CMRF-44 and CMRF-56 mAb, respectively. The reproducibility of the procedure and the ability to perform it in a closed sterile system makes it suitable for clinical use. Larger scale preparations starting from apheresis derived PBMC will produce sufficient BDC for immunotherapy protocols. The purified BDC elicited strong allogeneic mixed leukocyte reactions and HLA classes II- and I-restricted antigen-specific primary immune responses.