Plasma IFN-γ and IL-6 levels correlate with peripheral T-cell numbers but not toxicity in RCC patients treated with CAR T-cells
Enhanced CAR-T activity against established tumors by polarizing human T cells to secrete interleukin-9
AbstractCAR-T cell therapy is effective for hematologic malignancies. However, considerable numbers of patients relapse after the treatment, partially due to poor expansion and limited persistence of CAR-T cells in vivo. Here, we demonstrate that human CAR-T cells polarized and expanded under a Th9-culture condition (T9 CAR-T) have an enhanced antitumor activity against established tumors. Compared to IL2-polarized (T1) cells, T9 CAR-T cells secrete IL9 but little IFN-γ, express central memory phenotype and lower levels of exhaustion markers, and display robust proliferative capacity. Consequently, T9 CAR-T cells mediate a greater antitumor activity than T1 CAR-T cells against established hematologic and solid tumors in vivo. After transfer, T9 CAR-T cells migrate effectively to tumors, differentiate to IFN-γ and granzyme-B secreting effector memory T cells but remain as long-lived and hyperproliferative T cells. Our findings are important for the improvement of CAR-T cell-based immunotherapy for human cancers.
Abstract Chimeric antigen receptor-modified T lymphocytes (CART cells) have shown benefit as an adjuvant immunotherapy in the treatment of B cell malignancies. This success of re-targeted T cells has not been extended to other hematologic malignancies. We have developed an immunotherapeutic approach to treat acute myeloid leukemia (AML) using CAR T cells re-directed against the myeloid-specific antigen CD33 (CART-33). CART-33 cells are potent and specific in eliminating AML cells in vitro and in vivo. Despite this, CART-33 cells have shown poor in vivo expansion and persistence in NOD-SCID IL2rγ (-/-) (NSG) AML xenograft models. To address the reason for this, we assessed the impact of AML-expressed programmed death ligands 1 & 2 (PD-L1/2) on CART-33 cell activity. PD-L1 inhibits T cell functions upon binding PD-1, which is upregulated with T cell activation. Less is known about PD-L2's effect. Interferon-gamma (IFN-γ), a primary effector cytokine secreted by CD4+ and CD8+ effector T cells, is a known potent inducer of PD-L1 on AML blasts. Using AML cell lines U937, Oci-AML3, CMK, and MV4-11 we show that IFN-γ, TNF-α, and activated CART-33 supernatant can induce up-regulation of PD-L1 and PD-L2 on AML. IFN-γ and TNF-α synergize strongly in up-regulating PD-1 ligands on AML. The kinetics and induction of PD-L2 are distinct from that of PD-L1. Although PD-L1 is well documented to suppress T cell function via ligation of T cell expressed PD-1, induction of PD-L1/L2 had no effect on the cytolytic activity of CART-33 cells against AML in short term (<48 h) cultures. Paradoxically, 24 hr pre-treatment of AML with either IFN-γ or CART-33 supernatant increased AML susceptibility to killing by CART-33 cells despite elevated expression of PD-L1/L2 by AML. Our results highlight the regulatory complexity of AML cytolysis by re-targeted T lymphocytes, and argue that tumor-expressed PD-L1 and PD-L2 impacts the sustainability, but not short-term killing activity, of adoptively transferred CAR T cells in the treatment of AML. Disclosures No relevant conflicts of interest to declare.
Introduction A novel approach that can cover the therapeutic gap in NHL treatment are the autologous T cells, expressing Chimeric Antigen Receptors (CAR-T cells) against tumor markers. Such clinical-grade products based on Lenti (LV) or Retro- vectors have hit the market. An alternative vector system for CAR gene transfer in T-cells are Foamy Viruses (FV). To evaluate the potential of FV vectors in CAR-T cell development, we synthesized an antiCD19 scFv cDNA and cloned it in both an FV and an LV backbone; both vectors were tested in paired experiments Material and Methods The anti-CD19 CAR was under the control of the EF1a promoter; EGFP expression was under the control of an IRES2 element. The anti-CD19 CAR sequence was deduced from published data. FV vectors were made with a 4-plasmid vector system in 293T cells. 2nd generation LV vectors were purchased from Addgene. Cord blood (CB), healthy donor peripheral blood (PB) and CLL patients' PB was used as a source for CD3+ cells using immunomagnetic enrichment. Informed consent has been obtained in all cases of human sample use. T cells were activated by antiCD3/CD28 beads and transduced with antiCD19 LV or FV vectors. Transduction efficiency was assayed by flow cytometry (FCM) using a PE-conjugated anti-mouse Fab antibody. FV and LV CAR-T cells were expanded with Rapid Expansion Protocol (REP) and their cytotoxicity assays was evaluated against the CD19+ cell lines Raji and Daudi. The CLL patient derived CAR-Ts were evaluated against autologous B cells. Cytotoxicity was evaluated with an FCM protocol using CFSE-stained target cells vs unstained effector CARTs in different ratios. At the end of the incubation cells were stained with 7AAD to discriminate against live/dead cells. CAR-T cell activation was also assayed by INF-γ ELISA, following cocultures with target cells at a ratio of 1:1 for 24h. Results Vector titers: LV vector titers were between 3-5x10^5 TU/ml for both LV vectors (with or without EGFP cassette). FV vector titers were between 2-4x10^5 TU/ml regardless of the presence of the EGFP cassette. Tx efficiency: FV can mediate efficient gene transfer on T cells in the presence of heparin at an effective dose of 20-40 U/ml using a spinoculation technique. Transduction efficiency ranged from 40-65% at MOI=3-5, and was comparable to the transduction efficiency of LV vectors at a much higher MOI (10 to 30). Cytotoxicity data on lines: Following REP, the cell population consisted mostly (close to 96% purity) of CAR-T cells regardless of the vector used or of the T cell source. Effector cells were cocultured with the CD19+ cell lines, Daudi and Raji at varying ratios. With cord blood derived FV-CAR-T cells, at 4h post coculture we observed a 39.4% cell lysis at a ratio of 10:1 effector to target (n=1). Similar results were obtained for LV vectors. Peripheral blood derived CAR-T cells at THE same ratio (10:1), demonstrated 83.9% and 93.1% cell lysis for FV-CART and LV-CART cells respectively (n=2). Cytotoxicity data on CLL cells: T-cells from peripheral blood of CLL patients were used to generate LV- and FV-CAR-T cells. At the ratio of 10:1, we observed 73.1% and 69,8% cytotoxicity for FV-CAR-Ts and 70.1% and 70.7% with LV-CAR-Ts, in 2 independent paired experiments. IFN as activation marker: In two paired activation experiments, CB-derived FV-CAR-T cells secrete 560 and 437pg/ml of IFN-γ; similarly, LV-CAR-Ts secrete 534 and 554pg/ml IFN-γ. Untransduced control cells, produced 68pg/ml and 12pg/ml for FV-CAR-T and LV-CAR-T experimental arm respectively. Conclusion In the current work, we developed and tested FV vectors for anti- CD19 CAR-T cell production. We proved that FV viral vectors are capable of mediating efficient gene transfer to human T cells. We developed a method to efficiently transfer FV vectors into T-cells, using a clinically relevant protocol with heparin. The FV-derived CAR T cells demonstrate the same cytotoxic properties in vitro as their LV-derived counterpart and the same activation levels in the presence of CD19 expressing target cells as measured by IFN-γ secretion. FV CARTs derived from PB of CLL patients were capable of mediating comparable cytotoxicity levels as their LV-derived counterparts. Overall, we provide a proof of concept that FVs could be a safe and efficient alternative to LV derived vectors for CAR-T cells. Disclosures No relevant conflicts of interest to declare.
Abstract Abstract 348 Chimeric antigen receptors (CARs) are artificial molecules that can be used to redirect T cell immune response against antigens expressed on the surface of tumor cells. Recent encouraging clinical data from our group and others has shown that T cells engineered with these molecules can effectively traffic to distant tumor sites, penetrate even bulky disease, and eradicate disseminated tumors. Although promising, most current protocols expand engineered T cells non-specifically using IL2 and OKT3, which often results in a decrease in the frequency of transgenic populations over time. Additionally, cell expansion using conventional cultureware is complicated and labor intensive, which limits the broader application of this therapy. With the purpose of optimizing and streamlining CAR-T cell manufacture, we assessed whether cell expansion could be improved by: (i) supplementing non-specific stimuli (IL2) with an artificial antigen presenting cell (a-APC) engineered to express cognate antigen and co-stimulatory molecules, and (ii) efficiently and rapidly expanding cells in a simple and scalable gas permeable culture device (G-Rex), developed by Wilson Wolf Manufacturing for expanding suspension cells. As a proof of principle, we sought to expand T cells engineered with a CAR targeting the prostate cancer antigen, PSCA. We first generated an antigen-expressing a-APC cell line by modifying K562 cells, which already expressed a range of co-stimulatory molecules including CD80, CD86, and 41BBL, with a retroviral vector encoding the PSCA antigen. After the co-culture of CAR-PSCA T cells with the irradiated a-APC, we found that a-APCs co-expressing PSCA antigen, CD80, and 41BBL were the most effective in inducing T cell expansion, with a 1.9 fold increase in total cell numbers when compared with CAR T cells expanded in the presence of IL2 alone. We also saw an increase in the frequency of transgenic CAR-modified T cells in cultures expanded in the presence of a-APCs co-expressing PSCA antigen, CD80, and 41BBL, which increased from 36.5% CAR-modified cells to 88.1% after 10 days of culture. In contrast, the percentage of transgenic T cells was sustained when culture in the presence of IL2 (36.5% on day 0 and 37.2% on day 10). Thus, culture of CAR-T cells with antigen-expressing a-APCs not only improves total cell output, but also enriches for transgene-expressing. Next, to assess whether we could scale up cell production for clinical application we transferred the engineered a-APCs and CAR-PSCA modified T cells (at a 2:1 ratio) into a static GMP-compliant G-Rex with a surface area of 100cm2. In these G-Rex devices, O2 and CO2 are exchanged across a silicone membrane at the base, which allows for the addition of an increased depth of medium above the cells, providing more nutrients while the waste products are diluted. These culture conditions have been shown to increase cell output when compared with conventional commercial products such as bags, flasks, and 24-well tissue culture plates, without increasing the number of cell doublings. From an initial seeding density of 25E+06 CAR-modified T cells (0.25E+06 cells per cm2), we obtained a total of 2200–2500E+06 cells (22-25E+06 T cells per cm2) within 10 days of culture. Thus, without any intervention we obtained a 93 fold increase in cell numbers using only 1 liter of T cell culture media. As expected, the co-culture of antigen-expressing a-APCs with CAR-T cells also resulted in an enrichment of transgenic T cells (from 33.2% to 81.7% after 10 days of culture). Thus, we achieved a 2.4±1.2 fold increase in the frequency of transgenic T cells. Taken together the total T cell fold expansion (93) and the enrichment for the transgene (2.4±1.2), we calculate a 223.5±111.6 fold expansion of CAR T cells with 10 days of culture. Importantly we demonstrated the robustness of this manufacture process by successfully extending this approach to other CAR T cell products. Disclosures: Vera: Wilson Wolf Manufacturing: Consultancy.
Abstract Chimeric antigen receptor (CAR) T cell therapy has consistently shown significant results against acute lymphoblastic leukemia (ALL) in clinical trials1. However, results with other hematological or solid malignancies have been far more modest2. These disparate outcomes could be partially due to an inhibitory tumor microenvironment that suppresses CAR T cell function3. Thus, in order to expand the anti-tumor CAR T cell applications, a novel strategy in which these cells are capable of overcoming the hostile tumor microenvironment is needed. The cytokine interleukin-18 (IL-18) induces IFN-γ secretion, enhances the Th1 immune response and activates natural killer and cytotoxic T cells4. Early phase clinical trials that utilized systemic administration of recombinant IL-18 for the treatment of both solid and hematological malignancies have demonstrated the safety of this therapy5. We hypothesize that CAR T cells that constitutively secrete IL-18 could enhance CAR T cell survival and anti-tumor activity, and also activate cells from the endogenous immune system. To generate CAR T cells that constitutively secrete IL-18, we modified SFG-1928z and SFG-19m28mz CAR T cell constructs and engineered bicistronic human and murine vectors with a P2A element to actively secrete the IL-18 protein (1928z-P2A-hIL18 and 19m28mz-P2A-mIL18, respectively). Human and mouse T cells were transduced with these constructs and in vitro CAR T cell function was validated by coculturing the CAR T cells with CD19+ tumor cells and collecting supernatant for cytokine analysis. Both human and mouse CAR T cells secreted increased levels of IL-18, IFN-γ and IL-2. Proliferation and anti-tumor cytotoxic experiments were conducted with human T cells by coculturing CAR T cells with hCD19+ expressing tumor cells. 1928z-P2A-hIL18 CAR T cells had enhanced proliferation over 7 days and enhanced anti-tumor cytotoxicity over 72 hours when compared to 1928z CAR T cells (p=0.03 and 0.01, respectively) Next, the in vivo anti-tumor efficacy of the IL-18 secreting CAR T cell was tested in xenograft and syngeneic mouse models. Experiments were conducted without any prior lympho-depleting regimen. In the human CAR T cell experiments, Scid-Beige mice were injected with 1x106 NALM-6 tumor cells on day 0 and 5x106 CAR T cells on day 1. Survival curves showed a significant improvement in mouse survival with the 1928z-P2A-hIL18 CAR T cell treatment when compared to 1928z CAR T cell (p=0.006). Subsequently, to determine if IL-18 secreting CAR T cells could also improve anti-tumor efficacy in immunocompetent mice, we tested the murine 19m28mz-P2A-mIL18 CAR T cells in a syngeneic mouse model. The C57BL/6 hCD19+/- mCD19+/- mouse model was utilized and injected with 1x106 EL4 hCD19+ tumor cells on day 0 and 2.5 x106 CAR T cells on day 1. Mice treated with 19m28mz-P2A-mIL18 CAR T cells had 100% long-term survival, when compared to 19m28mz (p<0.0001). 19m28mz-P2A-mIL18 CAR T cells were detected in peripheral blood for up to 30 days after injection, whereas the 19m28mz CAR T cells were not detectable at any time point. In addition, 19m28mz-P2A-mIL18 CAR T cells were capable of inducing B cell aplasia for greater than 70 days, whereas 19m28mz treatment was not capable of inducing B cell aplasia. In vivo serum cytokine analysis demonstrated that 19m28mz-P2A-mIL18 CAR T cells, as compared to 19m28mz, significantly increased the levels of IFN-γ and TNF-α in the peripheral blood for up to 14 days after injection (p<0.0001 and 0.01, respectively). Despite the increase in IFN-γ and TNF-α cytokines, there was no increase in IL-6 levels. Our findings demonstrate that anti-CD19 CAR T cells that constitutively secrete IL-18 significantly increase serum cytokine secretion, enhance CAR T cell persistence, induce long-term B cell aplasia and improve mouse survival, even without any prior preconditioning. To our knowledge, this is the first description of an anti-CD19 CAR T cell that constitutively secretes IL-18 and that induces such high levels of T cell proliferation, persistence and anti-tumor cytotoxicity. We are currently investigating other mechanisms by which this novel CAR T cell functions, its interactions with the endogenous immune system, as well as testing its applicability in other tumor types. We anticipate that the advances presented by this new technology will expand the applicability of CAR T cells to a wider array of malignancies. Disclosures Brentjens: Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.
Abstract BACKGROUND: Chemotherapy followed by autologous T cells that are genetically modified to express a CD19-specific chimeric antigen receptor (CAR) has shown promise as a novel therapy for patients with relapsed or refractory B cell acute lymphoblastic leukemia (B-ALL); however, the risk of severe cytokine release syndrome (sCRS) and neurotoxicity has tempered enthusiasm for widespread application of this approach. The functional heterogeneity that is inherent in CAR-T cell products that are manufactured from undefined T cell subsets has hindered definition of dose-response relationships and identification of factors that may impact efficacy and toxicity. METHODS: We are conducting the first clinical trial that administers CD19 CAR-T cells manufactured from a defined composition of T cell subsets to adults with relapsed or refractory B-ALL. CD8+ and CD4+ T cells were enriched from each patient, transduced with a CD19 CAR lentivirus and separately expanded in vitro before formulation for infusion in a 1:1 ratio of CD8+:CD4+ CAR+ T cells at 2x105, 2x106 or 2x107 CAR-T cells/kg. Prior to CAR-T cell infusion, patients underwent lymphodepletion with a high-dose cyclophosphamide (Cy)-based regimen with or without fludarabine (Flu). RESULTS: Twenty-nine adults with B-ALL (median age 40, range 22 - 73 years; median 17% marrow blasts, range 0 - 97%), including 10 patients who had relapsed after allogeneic transplantation, received at least one CAR-T cell infusion. Twenty-four of 26 restaged patients (92%) achieved bone marrow (BM) complete remission (CR) by flow cytometry. CD4+ and CD8+ CAR-T cells expanded in vivo after infusion and their number in blood correlated with the infused CAR-T cell dose. Thirteen patients received lymphodepletion with Cy-based regimens without Flu. Ten of 12 restaged patients (83%) achieved BM CR by flow cytometry; however, 7 of these (70%) relapsed a median of 66 days after CAR-T cell infusion. Disease relapse correlated with a loss of CAR-T cell persistence in blood. We observed a CD8 cytotoxic T cell response to the murine scFv component of the CAR transgene that contributed to CAR-T cell rejection, and resulted in lack of CAR-T cell expansion after a second CAR-T cell infusion in 5 patients treated for persistent or relapsed disease. To minimize immune-mediated CAR-T cell rejection 14 patients were treated with Cy followed by Flu lymphodepletion (Cy/Flu, Cy 60 mg/kg x 1 and Flu 25 mg/m2 x 3-5) before CAR-T cell infusion. All patients (100%) who received Cy/Flu lymphodepletion achieved BM CR after CAR-T cell infusion. CAR-T cell expansion and persistence in blood was higher in Cy/Flu-lymphodepleted patients compared to their counterparts who received Cy alone (Day 28 after 2x106 CAR-T cells/kg: CD8+ CAR-T cells, mean 55.8/μL vs 0.10/μL, p<0.01; CD4+ CAR-T cells, 2.1/μL vs 0.02/μL, p<0.01), enabling reduction in CAR-T cell dose for Cy/Flu-treated patients. Patients who received Cy/Flu lymphodepletion appear to have longer disease-free survival (DFS) than those who received Cy alone (Cy/Flu, median, not reached; Cy alone, 150 days, p=0.09). CAR-T cell infusion was associated with sCRS, characterized by fever and hypotension requiring intensive care in 7 of 27 patients (26%) and neurotoxicity (≥ grade 3 CTCAE v4.03) in 13 of 27 patients (48%). Two patients died following complications of sCRS. Patients with sCRS or neurotoxicity had higher peak serum levels of IL-6, IFN-γ, ferritin and C-reactive protein compared to those without serious toxicity. Importantly IL-6, IFN-γ and TNF-α levels in serum collected on day 1 after CAR-T cell infusion from those who subsequently developed neurotoxicity were higher than those collected from their counterparts who did not develop neurotoxicity (IL-6, p<0.01; IFN-γ, p=0.05; TNF-α, p=0.04), providing potential biomarkers to test early intervention strategies to prevent neurotoxicity. The risks of sCRS and neurotoxicity correlated with higher leukemic marrow infiltration and increasing CAR-T cell dose. We have now adopted a risk-stratified approach to CAR-T cell dosing in which the CAR-T cell dose inversely correlates to the patient's bone marrow tumor burden. CONCLUSION: Risk-stratified dosing of CD19 CAR-T cells of defined subset composition is feasible and safe in a majority of patients with refractory B-ALL, and results in a CR rate of 92%. Addition of Flu to Cy-based lymphodepletion improves CAR-T cell expansion, persistence and DFS. Disclosures Turtle: Juno Therapeutics: Patents & Royalties, Research Funding. Berger:Juno Therapeutics: Patents & Royalties. Jensen:Juno Therapeutics: Equity Ownership, Patents & Royalties, Research Funding. Riddell:Adaptive Biotechnologies: Consultancy; Juno Therapeutics: Equity Ownership, Patents & Royalties, Research Funding; Cell Medica: Membership on an entity's Board of Directors or advisory committees. Maloney:Seattle Genetics: Honoraria; Janssen Scientific Affairs: Honoraria; Roche/Genentech: Honoraria; Juno Therapeutics: Research Funding.
The cell-surface protein B cell maturation antigen (BCMA, CD269) has emerged as a promising target for CAR-T cell therapy for multiple myeloma. In order to create a novel BCMA CAR, we generated a new BCMA monoclonal antibody, clone 4C8A. This antibody exhibited strong and selective binding to human BCMA. BCMA CAR-T cells containing the 4C8A scFv were readily detected with recombinant BCMA protein by flow cytometry. The cells were cytolytic for RPMI8226, H929, and MM1S multiple myeloma cells and secreted high levels of IFN-γ in vitro. BCMA-dependent cytotoxicity and IFN-γ secretion were also observed in response to CHO (Chinese Hamster Ovary)-BCMA cells but not to parental CHO cells. In a mouse subcutaneous tumor model, BCMA CAR-T cells significantly blocked RPMI8226 tumor formation. When BCMA CAR-T cells were given to mice with established RPMI8226 tumors, the tumors experienced significant shrinkage due to CAR-T cell activity and tumor cell apoptosis. The same effect was observed with 3 humanized BCMA-CAR-T cells in vivo. These data indicate that novel CAR-T cells utilizing the BCMA 4C8A scFv are effective against multiple myeloma and warrant future clinical development.
Introduction In recent years, CAR T-cell therapy has emerged as a potentially curative intent treatment for some patients with relapsed, refractory hematologic malignancies. Despite the exciting results, not all patients are able to receive CAR T-cells due to manufacturing failures. T-cells for CAR products are typically autologous and isolated from heavily pre-treated patients, which might account for some of the manufacturing failures and suboptimal clinical efficacy. T-cells collected either early into cancer diagnosis or prior to diagnosis may improve CAR T-cell expansion and limit manufacturing failure. We evaluated the feasibility of generating a CAR T-cell product manufactured from 50 ml of healthy donor blood. Methods Collaborators at Cell Vault collected 50 ml of whole blood from 3 healthy donors, isolated peripheral blood mononuclear cells (PBMCs), and cryopreserved the cells in cryovials at 5e6/vial (1.05-1.35e8 total cells). The vials were shipped to the Medical College of Wisconsin and stored frozen in liquid nitrogen until use. All PBMC vials for a given donor were thawed and pooled. Thawed PBMCs (0.93-1.17e8 cells) were loaded onto a CliniMACS Prodigy device, CD4 and CD8 T cells enriched by immunomagnetic sorting, and T cells placed in the culture chamber with IL-7, IL-15 and TransAct reagent to induce proliferation. On the second day of manufacturing, T cells were transduced with a lentiviral CAR vector encoding anti-CD19, 4-1BB and CD3z. Final CAR T-cell products for these pre-clinical studies were harvested on day 8 of manufacture. Results Starting enriched T-cell numbers from the 3 healthy donors ranged from 4.0-4.8e7 cells, the cells were 74-79% CD4/8+, and the average CD4/CD8 ratio was 1.4. On the day of CAR T harvest (day 8), total cells in the chamber had expanded to 3.6-4.6e9 cells (74-115 fold expansion), the cells were >99% CD3+, and the average CD4/CD8 ratio was 2.9 (Table 1). Final cell numbers were similar to what previously published CAR T manufacturing runs on the CliniMACS Prodigy (Zhu et al., Cytotherapy, 2018), that started with 1x108 enriched T-cells obtained from apheresed mononuclear cells. Cell surface CD19 CAR expression on the final cell products varied from 19.2-48.1%. While more than 50% of the starting T cells had a naïve (CD62L+ CD45RO-) phenotype, the final cell products contained greater than 80% central-memory (CD62L+ CD45RO+) T cells. Finally, the number of CD19 CAR T cells obtained from these pre-clinical manufacturing runs ranged from 7.82e8 to 2.21e9 cells. Conclusions 50 ml of cryopreserved PBMCs was adequate to manufacture clinically relevant CAR T-cell therapy doses from healthy donors not previously exposed to chemotherapy. Sufficient numbers of CAR T-cells were obtained to dose an 80 kg individual with at least 9e6 cells/kg which is greater than prescribed commercial doses of CD19 CAR T-cells. Further studies are indicated to determine if T-cells collected prior to disease modifying chemotherapies result in an improved product. These results demonstrate feasibility for generating CAR T cells from small volumes of whole blood collected at a time point before a cancer patient has been treated with multiple lines of therapy that could negatively impact starting T cell numbers and function. Disclosures Hari: GSK: Consultancy; Amgen: Consultancy; BMS: Consultancy; Takeda: Consultancy; Incyte Corporation: Consultancy; Janssen: Consultancy. Shah:TG Therapeutics: Consultancy; Celgene: Consultancy, Honoraria; Incyte: Consultancy; Kite Pharma: Consultancy, Honoraria; Cell Vault: Research Funding; Miltenyi Biotec: Honoraria, Research Funding; Lily: Consultancy, Honoraria; Verastim: Consultancy. Johnson:Miltenyi Biotec: Research Funding; Cell Vault: Research Funding.
Abstract Background: Cytokine release syndrome (CRS) in the setting of CAR T cell therapy manifests as a wide constellation of symptoms with multi-organ involvement. CRS can vary from a mild, self-limited course to a life-threatening systemic inflammatory response which, in severe cases, may be associated with manifestations similar to those seen in hemophagocytic lymphohistiocytosis (HLH). Tocilizumab, an anti-human IL-6 receptor antibody, has become a widely accepted pharmacologic intervention of first choice in severe CRS based on the observation of elevated levels of inflammatory cytokines, most notably interleukin (IL)-6 and interferon (IFN)-γ. Indeed, following administration of tocilizumab, most patients show rapid signs of improvement. However, in rare circumstances, CRS may be refractory to tocilizumab, and repeat administration or institution of additional immunosuppression is needed. Here we summarize cytokine profiles and CRS seen in patients treated with anti-CD22-CAR T cells and propose tocilizumab-refractory CRS as a potentially distinct pathophysiological entity from typical CRS that may merit alternative immunosuppressive interventions other than tocilizumab. Methods: Children and young adults with relapsed/refractory CD22+ ALL were treated with anti-CD22 CAR T cells. Serial samples for serum cytokine levels (IFN-γ, IL-6, IL-2, IL-10, IL-12p70, IL-1β, IL-15, IL-13, IL-4, IL-8, TNF-α, GM-CSF, MIP1-α) were obtained at pre-specified time points (0, 12, 24, 48, 72 hours, then daily on days 4 - 14 and 28 following CAR T cell infusion). Transduced CAR T cell dosage ranged from 3x10e5 cells/kg (dose level [DL] 1), 1x10e6 cells/kg (DL2), and 3x10e6 cells/kg (DL3). CRS severity was determined according to recently proposed grading system (Lee DW et al., Blood. 2014). Disease burden was assessed using standard morphology and flow cytometry analysis of bone marrow and peripheral blood samples. Results: Cytokine profiles are available on 10 patients treated: first 9 patients enrolled in our phase I trial (NCT02315612), and the tenth patient was treated off-protocol on an emergency investigational new drug protocol given lack of alternative treatment option for rapidly progressing disease. All subjects, median age 20 years (range, 6-22 years), had a diagnosis of multiply relapsed ALL. Seven of 10 subjects developed CRS. Five subjects with CRS were complete responders to CAR therapy (Table). The median time to the onset of CRS was 9 days (range, 7-12 days) post-infusion and resolved within 1 week with supportive care alone except in one patient who received pharmacologic intervention for grade 4 CRS. Rise in C-reactive protein (CRP) tended to correlate with clinical severity of CRS. Chronological changes in the level of IFN-γ, IL-6, IL-1β, IL-8, TNF-α, and MIP1-α generally mirrored the CRP trend, typically preceding CRP change by 1-2 days. In contrast to the CRS (maximum grade 2) seen in the first 9 patients, the 10th patient treated at DL3 developed grade 4 CRS with manifestations characteristic of HLH unresponsive to tocilizumab. Cytokine profile for this patient, compared to those of other CRS patients, was notable for a substantially higher serum IL-2 (35 pg/mL vs median 6.1 (range, 1.2-13.5)) and GM-CSF level (28 pg/mL vs median 1.0 (range, 0-6.1)) at 12 hours post infusion. Subsequent CRP elevation was not initially accompanied by a rise in IL-6 as in other patients, which may have explained the lack of response to tocilizumab (Figure). Evaluation for a genetic cause of HLH did not reveal any mutations (PRF1, MUNC13-4, RAB27A, STX11, STXBP2). Although this patient was a complete responder to therapy, the clinical course was complicated by pre-existing respiratory compromise and bacteremia, which may have contributed to increased CAR toxicity with variability in the cytokine profile. Conclusion: Based on our early experience, we postulate that patients with an early increase in GM-CSF and IL-2 may potentially experience more atypical and severe CRS, which without a concomitant rise in IL-6, may not respond to tocilizumab and thus early intervention with other immunosuppression may be indicated. Analysis of larger numbers of patients is required to better delineate clinical confounders and to develop rational pharmacological approach to CAR-mediated inflammatory responses. Ongoing efforts are underway to further analyze clinical samples for biomarkers. Disclosures Mackall: NCI: Patents & Royalties: B7H3 CAR.
Abstract Relapsed and refractory B-precursor acute lymphoblastic leukemia (B-ALL) remains a major therapeutic problem. Chimeric antigen receptor (CAR) modified T cells targeting CD19 are promising treatment options for these patients with the potential to induce hematological remission in adult and pediatric patients with refractory B-ALL. Despite the promising data, some patients do not respond to T-cell treatment. Until now it is not possible to fully understand and predict critical factors for response or non-response, but proliferation and persistence of CAR T cells in vivo is an essential precondition for treatment efficacy. Central memory T cells (Tcm) and stem cell-like memory T cells (Tscm) are known to be the best candidates for a sustained in vivo expansion after T-cell therapy with small cell doses. Therefore, we set up a protocol for the generation of anti-CD19 CAR T cells in a closed system that is compliant to current GMP regulations. Starting samples were mononuclear cells from pediatric ALL patients at diagnosis and under chemotherapy using up to 100cc peripheral blood. After separation for CD4+/CD8+ cells, T cells were activated with anti-CD3/CD28 beads. The lentiviral vector encoded the anti-CD19 single-chain variable fragment, 4-1BB (CD137) co-stimulation and T cell receptor (TCR) zeta chain. The whole process including separation of T cells, activation, transduction and cultivation was performed in a closed and fully automated system. Despite a broad variety in cellular composition including high blast counts, low cell numbers and a rather exhausted phenotype in the starting fraction, a robust T-cell composition was achieved at day five after activation with a mean of 63% CD4+ and 37% CD8+ T cells and a transduction rate of up to 38 %. The vast majority of CAR T cells were of a Tcm (47%) and Tscm (44%) phenotype leading to a strong proliferative potential of more than 100-fold expansion. In addition, a reduced sensitivity to inhibitory signals was documented (programmed cell death protein 1 (PD-1) expression ≤10%). CAR T cells showed effective cytotoxic functionality when co-cultured with CD19+ target cells with only little background of the un-transduced control. At an effector to target ratio of 5:1 up to 80 % of the CD19+ target cells were killed. In addition, a significant release of Interferon gamma (IFN-ɣ), Tumor necrosis factor (TNF-α) and Interleukin-2 (IL-2) was detected upon recognition of the target cell lines, confirming a strong and target-specific Th1 response. In conclusion, generation of CAR T cells from small pediatric blood samples was feasible in a closed GMP-compatible fully automated system. Despite variety of cell numbers, cellular composition and T cell phenotype in the starting sample, a uniform T cell product of Tcm and Tscm could be produced with a balanced CD4 / CD8 ratio leading to high expansion potential and functionality of the T cell graft. Disclosures Blaeschke: Miltenyi Biotec GmbH: Other: Miltenyi Biotec GmbH provided reagents free of charge.. Kaiser:Miltenyi Biotec GmbH: Employment. Assenmacher:Miltenyi Biotec GmbH: Employment.
