160 TLR9-activated B cells imprint adoptively transferred CD8+ T cells with potent tumor immunity and persistence in vivo

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A174-A174
Author(s):  
Aubrey Smith ◽  
Hannah Knochelmann ◽  
Megan Wyatt ◽  
Connor Dwyer ◽  
Guillermo Rangel Rivera ◽  
...  
Keyword(s):  
T Cells ◽  
South Carolina ◽  
T Cell ◽  
B Cells ◽  
Cell Therapy ◽  
Cd8 T Cells ◽  
University Of South Carolina ◽  
T Cell Therapy ◽  
Tlr Agonists

BackgroundCompared to traditional therapies for advanced malignancies, adoptive T cell transfer (ACT) therapy has increased the number of patients who achieve complete regressions; however, only about 20% of patients achieve lasting progression-free survival. Thus, more potent cell therapies for cancer are urgently needed. Preconditioning patients with chemo- or radiotherapy prior to cell transfer provides several benefits to the transferred T cells. One of these benefits is activation of the host immune system Toll-like receptors (TLRs) via microbes leaked from the injured gut. Direct administration of TLR agonists has been used in numerous preclinical and clinical trial settings, but has shown toxicity and limited success in promoting tumor immunity in patients. We hypothesized that TLR agonists could be used in an alternative way – in the ex vivo propagation of potent T cells for ACT.MethodsTo test our hypothesis, we employed the pmel-1 ACT model, where all CD8+ T cells express a transgenic TCR which recognizes the gp100 epitope expressed by melanoma. To determine if TLR agonists could improve cell therapy, we activated CD8+ T cells in the presence of APCs and the TLR9 agonist, CpG, and transferred T cells to B16F10 melanoma-bearing mice.ResultsPmel-1 CD8+ T cell products expanded with CpG elicited potent anti-melanoma immunity in vivo and improved survival compared to traditionally expanded T cell therapy. CpG-derived T cells engrafted robustly and persisted longer than traditional T cells in the host. We explored the characteristics of CpG-expanded T cells and found that T cells generated from a CpG culture incur a unique proteomic and cell surface signature phenotype. Of all the cell types present in the starting culture (CD4+ T cells, NK cells, B cells, DCs, macrophages), B cells were the only cell type critical to achieve a more potent T cell therapy with CpG. In a direct comparison of CpG class A (targeting DCs) and CpG class B (targeting B cells), only the B cell-activating CpG improved cell therapy. Finally, we found that B cells alone could improve purified CD8+ T cells for ACT when the co-culture was activated with CpG, indicating that B cells become potent APCs in this context.ConclusionsCollectively, our findings indicate a novel way to use TLR agonists to improve ACT and reveal a critical role for B cells in the expansion of potent anti-tumor CD8+ T cells. Translating these findings to ACT therapies could provide dramatic improvements in patients with late stage malignancies.AcknowledgementsProteomic analysis was performed at the Mass Spectrometry Facility, a University Shared Research Resource at the Medical University of South Carolina, using instrumentation acquired through the NIH shared instrumentation grant program (S10 OD010731-Orbitrap Elite Mass Spectrometer or Orbitrap Fusion Lumos ETD/UVD MS (S10 OD025126).Trial RegistrationNAEthics ApprovalAll animal procedures were approved by the Institutional Animal Care & Use Committee of the Medical University of South Carolina, protocol number 0488.ConsentNAReferencesNA

scholarly journals First-in-Human Study of ET019003, a Next Generation Anti-CD19 T-Cell Therapy, in Patients with Relapsed/Refractory Diffuse Large B Cell Lymphoma (r/r DLBCL)

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2870-2870 ◽  
Author(s):  
Pengcheng He ◽  
Hong Liu ◽  
Haibo Liu ◽  
Mina Luo ◽  
Hui Feng ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
Cell Expansion ◽  
T Cell Therapy ◽  
Car T ◽  
Equity Ownership ◽  
T Cell Expansion ◽  
The Absolute

Background : CD19-targeted CAR-T therapies have shown promising efficacy in treating B-cell malignancies. However, treatment-related toxicities, such as cytokine-release syndrome (CRS) and CAR T-cell-related encephalopathy syndrome (CRES), have been one of the major obstacles limiting the use of CAR-T therapies. How to minimize occurrence and severity of toxicity while maintaining efficacy is a major focus for T-cell therapies in development. ET019003 is a next generation CD19-targeted T-cell therapy developed by Eureka Therapeutics, built on the proprietary ARTEMISTM T-cell platform. The ET019003 construct is optimized with the co-expression of an ET190L1 Antibody-TCR (Xu et al, 2018) and novel co-stimulation molecule. We are conducting a First-in-human (FIH) study of ET019003 T cells in CD19+ r/r DLBCL patients. Methods: This FIH study aims to evaluate the safety and efficacy of ET019003 T-cell therapy in CD19+ patients with r/r DLBCL. As of July 2019, six subjects were administered ET019003 T cells. These subjects were pathologically confirmed with DLBCL that is CD19+ (by immunohistochemistry), whose disease have progressed or relapsed after 2-5 lines of prior therapies. All were high-risk patients with rapid tumor progression and heavy tumor burden. Each subject had a Ki67 proliferative index over 60%, 2/6 of the subjects had a Ki67 proliferative index over 90%. Moreover, 5/6 of the subjects had extra-nodal involvement. Following a 3-day preconditioning treatment with Fludarabine (25mg/m2/day)/ Cyclophosphamide (250mg/m2/day), patients received i.v. infusions of ET019003 T cells at an initial dose of 2-3×106 cells/kg. Additional doses at 3×106 cells/kg were administered at 14 to 30-day intervals. Adverse events were monitored and assessed based on CTCAE 5.0. Clinical responses were assessed based on Lugano 2014 criteria. Results: As of July 2019, six subjects have received at least one ET019003 T-cell infusion, and four subjects have received two or more ET019003 T-cell infusions. No Grade 2 or higher CRS was observed in the six subjects. One subject developed convulsions and cognitive disturbance. This subject had lymphoma invasion in the central nervous system before ET019003 T-cell therapy. The subject was treated with glucocorticoid and the symptoms resolved within 24 hours. Other adverse events included fever (6/6, 100%), fatigue (3/6, 50%), thrombocytopenia (3/6, 50%), diarrhea (2/6, 33%), and herpes zoster (1/6, 17%). ET019003 T-cell expansion in vivo (monitored by flow cytometry and qPCR) was observed in all six subjects after first infusion. The absolute peak value of detected ET019003 T cells ranged between 26,000 - 348,240 (median 235,500) per ml of peripheral blood. Tmax (time to reach the absolute peak value) was 6 - 14 days (median 7.5 days). For the four subjects who received multiple ET019003 T-cell infusions, the absolute peak values of detected ET019003 T cells after the second infusion were significantly lower than the absolute peak values achieved after the first infusion. For the two subjects who received three or more infusions of ET019003 T cells, no significant ET019003 T-cell expansion in vivo was observed after the third infusion. All six subjects completed the evaluation of clinical responses at 1 month after ET019003 T-cell therapy. All subjects responded to ET019003 T cells and achieved either a partial remission (PR) or complete response (CR). Conclusions: Preliminary results from six CD19+ r/r DLBCL patients in a FIH study show that ET019003 T-cell therapy is safe with robust in vivo T-cell expansion. The clinical study is on-going and we are monitoring safety as well as duration of response in longer follow-up. Reference: Xu et al. Nature Cell Discovery, 2018 Disclosures Liu: Eureka Therapeutics: Employment, Equity Ownership. Chang:Eureka Therapeutics: Equity Ownership. Liu:Eureka Therapeutics: Employment, Equity Ownership.

scholarly journals 708 Novel ways to exploit IL-21 to augment adoptive T cell transfer therapy against tumors

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A737-A737
Author(s):  
Anna Cole ◽  
Guillermo Rangel RIvera ◽  
Aubrey Smith ◽  
Megan Wyatt ◽  
Brandon Ware ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Immune Cells ◽  
Striking Difference ◽  
T Cell Therapy ◽  
Cell Immunity ◽  
Emory University

BackgroundIL-21 enhances the anti-tumor capacity of adoptively transferred CD8+ T cells, while IL-2 and IL-15 impair T cell immunity by driving their expansion to a more differentiated status. Yet, these cytokines can act on many different immune cells. Given the potency of IL-21, we tested if this cytokine directly augments T cells or rather if it enhances other immune cells in the culture that indirectly improves T cell therapy.MethodsTo test this question, splenocytes from pmel-1 transgenic mice were used, as all CD8+ T cells express a transgenic TCR specific for tumor-antigen gp10025–33 overexpressed on melanoma. We then peptide activated naïve CD8+ T cells enriched or not from the spleen of pmel-1 mice and expanded them in the presence of IL-21 or IL-2 (10 ng/mL) for four days. Expanded pmel-1 from these various cultures were then restimulated with irradiated splenocytes pulsed with gp10025–33 and grown an additional seven days with IL-2 (10 ng/mL), irrespective of their initial cytokine condition. The in vitro memory phenotype, exhaustion profile, and cytokine secretion of these cultures were then assayed. Furthermore, mice bearing B16KVP melanoma tumors were infused with pmel-1 T cells expanded via these various approaches and compared for their relative capacity to engraft, persist, and regress tumor in vivo.ResultsInterestingly, we discovered that IL-21-treated T cells generated from bulk splenocytes are phenotypically and functionally distinct from IL-21-treated isolated T cells. Upon restimulation, IL-21-treated T cells from bulk splenocytes exhibited an exhausted phenotype that was like anergic IL-2-treated T cells. Moreover, few cells expressed CD62L but expressed heightened markers of suppression, including TIM3, PD-1, and EOMES. Moreover, they produced more effector molecules, including granzyme B and IFN-gamma. In vivo IL-21-treated T cells expanded from bulk splenocytes engrafted and persisted poorly, in turn mediating suboptimal regression of melanoma. Conversely, IL-21 dramatically bolstered the engraftment and antitumor activity of T cells only if they were first isolated from the spleen prior to their expansion and infusion into the animal.ConclusionsCollectively, our data shows that IL-21 may improve ACT therapy best when used directly on antitumor CD8+ T cells. Further studies will illuminate the mechanism behind this striking difference and determine whether other cell subsets reactive to IL-21 cause T cell dysfunction and/or reduced bioavailability. These findings are important for defining the best culture conditions in which to use IL-21 for ACT.AcknowledgementsWe would like to acknowledge Emory University, The Winship Cancer Institute, and the Pediatrics/Winship Flow Cytometry Core.Ethics ApprovalAll animal procedures were approved by the Institutional Animal Care and Use Committee of Emory University, protocol number 201900225.

scholarly journals 124 Functionalizing CAR T cells for selective proliferation and dual-targeting using the meditope technology

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A133-A133
Author(s):  
Cheng-Fu Kuo ◽  
Yi-Chiu Kuo ◽  
Miso Park ◽  
Zhen Tong ◽  
Brenda Aguilar ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
T Cell Therapy ◽  
Car T Cells ◽  
Car T Cell ◽  
Car T Cell Therapy ◽  
Car T

BackgroundMeditope is a small cyclic peptide that was identified to bind to cetuximab within the Fab region. The meditope binding site can be grafted onto any Fab framework, creating a platform to uniquely and specifically target monoclonal antibodies. Here we demonstrate that the meditope binding site can be grafted onto chimeric antigen receptors (CARs) and utilized to regulate and extend CAR T cell function. We demonstrate that the platform can be used to overcome key barriers to CAR T cell therapy, including T cell exhaustion and antigen escape.MethodsMeditope-enabled CARs (meCARs) were generated by amino acid substitutions to create binding sites for meditope peptide (meP) within the Fab tumor targeting domain of the CAR. meCAR expression was validated by anti-Fc FITC or meP-Alexa 647 probes. In vitro and in vivo assays were performed and compared to standard scFv CAR T cells. For meCAR T cell proliferation and dual-targeting assays, the meditope peptide (meP) was conjugated to recombinant human IL15 fused to the CD215 sushi domain (meP-IL15:sushi) and anti-CD20 monoclonal antibody rituximab (meP-rituximab).ResultsWe generated meCAR T cells targeting HER2, CD19 and HER1/3 and demonstrate the selective specific binding of the meditope peptide along with potent meCAR T cell effector function. We next demonstrated the utility of a meP-IL15:sushi for enhancing meCAR T cell proliferation in vitro and in vivo. Proliferation and persistence of meCAR T cells was dose dependent, establishing the ability to regulate CAR T cell expansion using the meditope platform. We also demonstrate the ability to redirect meCAR T cells tumor killing using meP-antibody adaptors. As proof-of-concept, meHER2-CAR T cells were redirected to target CD20+ Raji tumors, establishing the potential of the meditope platform to alter the CAR specificity and overcome tumor heterogeneity.ConclusionsOur studies show the utility of the meCAR platform for overcoming key challenges for CAR T cell therapy by specifically regulating CAR T cell functionality. Specifically, the meP-IL15:sushi enhanced meCAR T cell persistence and proliferation following adoptive transfer in vivo and protects against T cell exhaustion. Further, meP-ritiuximab can redirect meCAR T cells to target CD20-tumors, showing the versatility of this platform to address the tumor antigen escape variants. Future studies are focused on conferring additional ‘add-on’ functionalities to meCAR T cells to potentiate the therapeutic effectiveness of CAR T cell therapy.

scholarly journals Anti–4-1bb Monoclonal Antibodies Abrogate T Cell–Dependent Humoral Immune Responses in Vivo through the Induction of Helper T Cell Anergy

1999 ◽  
Vol 190 (10) ◽  
pp. 1535-1540 ◽  
Author(s):  
Robert S. Mittler ◽  
Tina S. Bailey ◽  
Kerry Klussman ◽  
Mark D. Trailsmith ◽  
Michael K. Hoffmann
Keyword(s):  
Immune Response ◽  
T Cells ◽  
Monoclonal Antibodies ◽  
T Cell ◽  
B Cells ◽  
Humoral Immunity ◽  
Cd8 T Cells ◽  
Immunodeficient Mice ◽  
Humoral Immune

The 4-1BB receptor (CDw137), a member of the tumor necrosis factor receptor superfamily, has been shown to costimulate the activation of T cells. Here we show that anti–mouse 4-1BB monoclonal antibodies (mAbs) inhibit thymus-dependent antibody production by B cells. Injection of anti–4-1BB mAbs into mice being immunized with cellular or soluble protein antigens induced long-term anergy of antigen-specific T cells. The immune response to the type II T cell–independent antigen trinintrophenol-conjugated Ficoll, however, was not suppressed. Inhibition of humoral immunity occurred only when anti–4-1BB mAb was given within 1 wk after immunization. Anti–4-1BB inhibition was observed in mice lacking functional CD8+ T cells, indicating that CD8+ T cells were not required for the induction of anergy. Analysis of the requirements for the anti–4-1BB–mediated inhibition of humoral immunity revealed that suppression could not be adoptively transferred with T cells from anti–4-1BB–treated mice. Transfer of BALB/c splenic T cells from sheep red blood cell (SRBC)-immunized and anti–4-1BB–treated mice together with normal BALB/c B cells into C.B-17 severe combined immunodeficient mice failed to generate an anti-SRBC response. However, B cells from the SRBC-immunized, anti–4-1BB–treated BALB/c mice, together with normal naive T cells, exhibited a normal humoral immune response against SRBC after transfer, demonstrating that SRBC-specific B cells were left unaffected by anti–4-1BB mAbs.

scholarly journals GPRC5D is a target for the immunotherapy of multiple myeloma with rationally designed CAR T cells

2019 ◽  
Vol 11 (485) ◽  
pp. eaau7746 ◽  
Author(s):  
Eric L. Smith ◽  
Kim Harrington ◽  
Mette Staehr ◽  
Reed Masakayan ◽  
Jon Jones ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
B Cell ◽  
T Cell Therapy ◽  
Car T Cells ◽  
Car T Cell Therapy ◽  
Car T

Early clinical results of chimeric antigen receptor (CAR) T cell therapy targeting B cell maturation antigen (BCMA) for multiple myeloma (MM) appear promising, but relapses associated with residual low-to-negative BCMA-expressing MM cells have been reported, necessitating identification of additional targets. The orphan G protein–coupled receptor, class C group 5 member D (GPRC5D), normally expressed only in the hair follicle, was previously identified as expressed by mRNA in marrow aspirates from patients with MM, but confirmation of protein expression remained elusive. Using quantitative immunofluorescence, we determined that GPRC5D protein is expressed on CD138+ MM cells from primary marrow samples with a distribution that was similar to, but independent of, BCMA. Panning a human B cell–derived phage display library identified seven GPRC5D-specific single-chain variable fragments (scFvs). Incorporation of these into multiple CAR formats yielded 42 different constructs, which were screened for antigen-specific and antigen-independent (tonic) signaling using a Nur77-based reporter system. Nur77 reporter screen results were confirmed in vivo using a marrow-tropic MM xenograft in mice. CAR T cells incorporating GPRC5D-targeted scFv clone 109 eradicated MM and enabled long-term survival, including in a BCMA antigen escape model. GPRC5D(109) is specific for GPRC5D and resulted in MM cell line and primary MM cytotoxicity, cytokine release, and in vivo activity comparable to anti-BCMA CAR T cells. Murine and cynomolgus cross-reactive CAR T cells did not cause alopecia or other signs of GPRC5D-mediated toxicity in these species. Thus, GPRC5D(109) CAR T cell therapy shows potential for the treatment of advanced MM irrespective of previous BCMA-targeted therapy.

T-cell therapy in metastatic melanoma: TIL 1383I TCR transduced T cells after infusion and activity in vivo.

2015 ◽  
Vol 33 (15_suppl) ◽  
pp. 3043-3043 ◽  
Author(s):  
Courtney Regan ◽  
Joseph Clark ◽  
Tamson Moore ◽  
Kelly Moxley ◽  
Gina Scurti ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
Metastatic Melanoma ◽  
T Cell Therapy

A phase Ia/Ib, open-label first-in-human study of the safety, tolerability, and feasibility of gene-edited autologous NeoTCR-T cells (NeoTCR-P1) administered to patients with locally advanced or metastatic solid tumors.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. TPS3151-TPS3151
Author(s):  
Bartosz Chmielowski ◽  
Samuel Ejadi ◽  
Roel Funke ◽  
Todd Stallings-Schmitt ◽  
Mitch Denker ◽  
...  
Keyword(s):  
Clinical Trial ◽  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
Solid Tumors ◽  
Cd8 T Cells ◽  
Adoptive T Cell Therapy ◽  
Autologous Tumor ◽  
T Cell Therapy ◽  
Trial Phase

TPS3151 Background: Neoepitopes (neoE) derived from private tumor-exclusive mutations represent compelling targets for personalized TCR-T cell therapy. An ultra-sensitive and high-throughput process was developed to capture tumor mutation-targeted CD8 T cells from patient blood. NeoTCRs cloned from the captured CD8 T cells, when engineered into fresh CD8 and CD4 T cells, effected killing of patients’ autologous tumor cells in vitro. These observations have been leveraged for the development of a fully personalized adoptive T cell therapy (NeoTCR-P1). A Phase 1 clinical trial testing NeoTCR-P1 in subjects with solid tumors is ongoing (NCT03970382). Methods: During the initial trial phase, escalating doses of NeoTCR-P1 T cells administered without and with IL-2 in the regimen, and following conditioning chemotherapy, will be evaluated in subjects with advanced or metastatic solid tumors (melanoma, urothelial cancer, colorectal cancer, ovarian cancer, HR+ breast cancer, and prostate cancer). The objective of the Phase 1a study is to establish a recommended Phase 2 dose. Primary endpoints include the incidence and nature of DLTs and overall process feasibility. The proliferation, persistence, and trafficking of NeoTCR-T cells will be characterized. In the expansion trial phase, preliminary anti-tumor activity of NeoTCR-P1 will be assessed in selected tumors. The combination of NeoTCR-P1 dosing plus nivolumab will be tested in a Phase 1b study. Conclusion: This is the first clinical study of an autologous, fully personalized adoptive T cell therapy directed against private tumor-exclusive mutations, generated without using recombinant viral vectors. Clinical trial information: NCT03970382 .

scholarly journals Detection and Functional Analysis of CD8+ T Cells Specific for PRAME: a Target for T-Cell Therapy

2006 ◽  
Vol 12 (10) ◽  
pp. 3130-3136 ◽  
Author(s):  
Marieke Griffioen ◽  
Jan H. Kessler ◽  
Martina Borghi ◽  
Ronald A. van Soest ◽  
Caroline E. van der Minne ◽  
...  
Keyword(s):  
Functional Analysis ◽  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
Cd8 T Cells ◽  
T Cell Therapy

scholarly journals The roles of T cell competition and stochastic extinction events in chimeric antigen receptor T cell therapy

2021 ◽  
Vol 288 (1947) ◽  
Author(s):  
Gregory J. Kimmel ◽  
Frederick L. Locke ◽  
Philipp M. Altrock
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
Chimeric Antigen Receptor ◽  
Antigen Receptor ◽  
T Cell Therapy ◽  
Car T Cells ◽  
Car T Cell ◽  
Car T

Chimeric antigen receptor (CAR) T cell therapy is a remarkably effective immunotherapy that relies on in vivo expansion of engineered CAR T cells, after lymphodepletion (LD) by chemotherapy. The quantitative laws underlying this expansion and subsequent tumour eradication remain unknown. We develop a mathematical model of T cell–tumour cell interactions and demonstrate that expansion can be explained by immune reconstitution dynamics after LD and competition among T cells. CAR T cells rapidly grow and engage tumour cells but experience an emerging growth rate disadvantage compared to normal T cells. Since tumour eradication is deterministically unstable in our model, we define cure as a stochastic event, which, even when likely, can occur at variable times. However, we show that variability in timing is largely determined by patient variability. While cure events impacted by these fluctuations occur early and are narrowly distributed, progression events occur late and are more widely distributed in time. We parameterized our model using population-level CAR T cell and tumour data over time and compare our predictions with progression-free survival rates. We find that therapy could be improved by optimizing the tumour-killing rate and the CAR T cells' ability to adapt, as quantified by their carrying capacity. Our tumour extinction model can be leveraged to examine why therapy works in some patients but not others, and to better understand the interplay of deterministic and stochastic effects on outcomes. For example, our model implies that LD before a second CAR T injection is necessary.

scholarly journals Efficient elimination of primary B-ALL cells in vitro and in vivo using a novel 4-1BB-based CAR targeting a membrane-distal CD22 epitope

2020 ◽  
Vol 8 (2) ◽  
pp. e000896
Author(s):  
Talia Velasco-Hernandez ◽  
Samanta Romina Zanetti ◽  
Heleia Roca-Ho ◽  
Francisco Gutierrez-Aguera ◽  
Paolo Petazzi ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Therapy ◽  
T Cell Therapy ◽  
High Affinity ◽  
Car T Cells ◽  
Car T Cell ◽  
Car T

BackgroundThere are few therapeutic options available for patients with B-cell acute lymphoblastic leukemia (B-ALL) relapsing as CD19– either after chemotherapy or CD19-targeted immunotherapies. CD22-chimeric antigen receptor (CAR) T cells represent an attractive addition to CD19-CAR T cell therapy because they will target both CD22+CD19– B-ALL relapses and CD19– preleukemic cells. However, the immune escape mechanisms from CD22-CAR T cells, and the potential contribution of the epitope binding of the anti-CD22 single-chain variable fragment (scFv) remain understudied.MethodsHere, we have developed and comprehensively characterized a novel CD22-CAR (clone hCD22.7) targeting a membrane-distal CD22 epitope and tested its cytotoxic effects against B-ALL cells both in in vitro and in vivo assays.ResultsConformational epitope mapping, cross-blocking, and molecular docking assays revealed that the hCD22.7 scFv is a high-affinity binding antibody which specifically binds to the ESTKDGKVP sequence, located in the Ig-like V-type domain, the most distal domain of CD22. We observed efficient killing of B-ALL cells in vitro, although the kinetics were dependent on the level of CD22 expression. Importantly, we show an efficient in vivo control of patients with B-ALL derived xenografts with diverse aggressiveness, coupled to long-term hCD22.7-CAR T cell persistence. Remaining leukemic cells at sacrifice maintained full expression of CD22, ruling out CAR pressure-mediated antigen loss. Finally, the immunogenicity capacity of this hCD22.7-scFv was very similar to that of other CD22 scFv previously used in adoptive T cell therapy.ConclusionsWe report a novel, high-affinity hCD22.7 scFv which targets a membrane-distal epitope of CD22. 4-1BB-based hCD22.7-CAR T cells efficiently eliminate clinically relevant B- CD22high and CD22low ALL primary samples in vitro and in vivo. Our study supports the clinical translation of this hCD22.7-CAR as either single or tandem CD22–CD19-CAR for both naive and anti-CD19-resistant patients with B-ALL.

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