scholarly journals Tri-Specific CD19xCD20xCD22 VHH CAR-T Cells (LCAR-AIO) Eradicate Antigen-Heterogeneous B Cell Tumors, Enhance Expansion, and Prolong Persistence in Preclinical In Vivo Models

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1700-1700
Author(s):  
Zhe (joy) Zhou ◽  
Yue Han ◽  
Hong-Bo Pan ◽  
Cai-Jun Sang ◽  
Dong-Lin Shi ◽  
...  

Abstract Introduction: Anti-CD19 CAR-T therapy has achieved remarkable treatment efficacy in B cell lymphoma. However, targeting CD19 antigen alone can only benefit about half of patients with B cell malignancies. The FDA-approved CD19 CAR-T therapies all use same binder, which is murine FMC63 scFv targeting CD19 and up to 39%-88% of patients have relapsed. Possible mechanisms of relapse include mutations or downregulation of the targeted antigen, CD19, however, the targetable expression of CD20 and CD22 is preserved. In addition, immunogenicity against murine FMC63 scFv could have a negative impact on possible re-dosing regimen. To overcome these limitations, we designed and developed a novel tri-specific VHH CAR-T, targeting three antigens that include CD19, CD20 and CD22, for treating patients who relapsed from prior CAR-T therapies. Methods: We engineered mono-, bi-, or tri-specific VHH CAR constructs targeting CD19, CD20 and/or CD22 respectively in a lentiviral vector. The mono-, bi- or tri-specific CAR-T cells were tested against tumor lines expressing single, dual or triple antigens in an in vitro cytotoxicity assay. In addition, we evaluated the contribution of different CAR backbones, and possible combinations of scFv, VH or VHH to CAR design. We hypothesized that our lead tri-specific VHH CAR-T, LCAR-AIO, would potently inhibit tumors with heterogeneous Ag expression and prevent Ag escape. To validate this, we compared in vitro cytolytic activity and cytokine production of LCAR-AIO CAR-T to anti-CD19 FMC63 CAR-T against CD19 +CD20 +CD22 + Raji.Luc and CD19KOCD20 +CD22 +Raji.Luc cells . In vivo treatment efficacy and CAR-T persistence were also investigated in NCG murine model xenografted with Raji tumor line. 0.3x10 6 CAR +T cells or dose-matched untransduced T cells were given to NCG mice four days post i.v. implantation of Raji.Luc tumor cells. Tumor growth was monitored weekly by bioluminescence imaging until achieved endpoint (55 days), and CAR-T persistence was determined using genomic DNA level. Results: Tri-specific VHH CAR-T cells can mediate dose-dependent cytotoxicity against Raji tumor lines. Compared to mono- or bi-specific VHH or scFv CAR-T, tri-specific VHH CAR-T demonstrated equal or better cytolytic activity. Our lead tri-VHH CAR-T, LCAR-AIO, was able to specifically lyse K652 over-expressing single target such as CD19, CD20 or CD22, at the similar level to mono-specific CD19, CD20 or CD22 VHH CAR-T. Since no blocking effect of recognition against these three antigens was observed, our result suggested that all three VHHs in LCAR-AIO are functional. In comparison to anti-CD19 FMC63 scFv CAR-T, LCAR-AIO exhibited higher lytic activity and IFN-γ production against Raji.Luc tumor lines in vitro. In addition, LCAR-AIO retained its robust lytic activity and IFN-γ production when co-cultured with CD19KO-Raji.Luc cells while anti-CD19 FMC63 scFv CAR-T could not, suggesting LCAR-AIO may prevent tumor escape due to loss of CD19. Furthermore, comparison of LCAR-AIO to mono-scFv CAR-T (anti-CD19 FMC63-BBz, anti-CD20 Leu16-BBz or anti-CD22 m971-BBz) was performed in NCG mice xenografted with Raji cell line, LCAR-AIO exhibited better T cell expansion, longer persistence, and superior efficacy in eliminating tumors. Conclusions: Based on in vitro and in vivo preclinical data, tri-specific CD19xCD20xCD22 VHH CAR-T can be effective targeting tumors lack of CD19 expression, therefore, it has the potential of treating relapsed patients with prior CD19 CAR-T therapy. The feasibility of making tri-specific CAR-T would help to extend this technology to solid cancers where heterogeneity poses a major challenge at current stage. Figure 1 Figure 1. Disclosures Zhou: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Han: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Pan: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Sang: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Shi: Legend Biotech: Current Employment. Feng: Legend Biotech: Current Employment. Xiao: Legend Biotech: Current Employment. Zhuang: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Wang: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Fan: Legend Biotech: Current Employment, Current equity holder in publicly-traded company.

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 733-733
Author(s):  
Anisha M Loeb ◽  
Sommer Castro ◽  
Cynthia Nourigat-Mckay ◽  
LaKeisha Perkins ◽  
Laura Pardo ◽  
...  

Abstract Chimeric antigen receptor (CAR) Ts have been effective in pre-B ALL, but their efficacy in AML has yet to be established. A significant barrier to effective CAR T therapy for AML is the substantial overlap of cell surface antigens expressed on AML and normal hematopoietic cells. To overcome this barrier, we profiled the transcriptome of over 3000 AML cases in children and young adults and contrasted this to normal hematopoietic tissues in search for AML-restricted targets (high expression in AML, silence in normal hematopoiesis). This led to the discovery of over 200 AML-restricted genes. Of these, Preferentially Expressed Antigen in Melanoma (PRAME) is among one of the highest expressing AML-restricted genes (Figure 1A) and, given its previous track record as a target for a variety of cancers, we selected this target for further assessment and therapeutic development in AML. However, PRAME is intracellular and therefore is inaccessible for targeting with conventional CAR T. Recently, a novel approach to target intracellular antigens was developed using TCR mimic (mTCR) antibodies, which recognize peptide/human leukocyte antigen (HLA) complexes on the tumor cell surface in a similar mode of recognition as authentic T Cell Receptors (TCRs). The Pr20 antibody was developed to recognize the PRAME ALY peptide in the context of HLA-A*02. Utilizing this Pr20 antibody, we developed a mTCR CAR T targeting PRAME and evaluated its preclinical efficacy in AML. The VL and VH sequences from Pr20 were used to construct the single-chain fragment variable domain of the 41-BB/CD3ζ CAR vector. We evaluated PRAME mTCR CAR T cells against OCI-AML-2 and THP-1 AML cell lines (PRAME +/HLA-A*02 +), K562 CML cell line (PRAME +/HLA-A*02 -) and HEK293T (293T) (PRAME -/HLA-A*02 +). Using a PE-conjugated Pr20 antibody, we confirmed that OCI-AML2 and THP-1 express PRAME ALY: HLA-A*02 but not K562 and 293T by flow cytometry (Figure 1B). As further confirmation, AML blasts in primary patient samples also stained with the Pr20 antibody (Figure 1C). For in-vivo studies, leukemia-bearing mice were treated with unmodified T or PRAME mTCR CAR T cells at 5x10 6 cells (1:1 CD4:CD8) per mouse 1 week following leukemia injection. Leukemia burden was measured weekly by bioluminescence IVIS imaging. Cells were treated with 10ng/mL of IFN-γ prior to co-incubation with T cells for 16 hours. PRAME mTCR CAR T cells demonstrated potent cytolytic activity against OCI-AML2 and THP1 but not against K562 or 293T cells, following co-incubation with target cells for 24 hours (Figure 1D). Consistent with potent, target-specific reactivity against PRAME ALY: HLA-A*02 positive cells, increased levels of IFN-γ, IL-2 and TNF-α were detected in cocultures of CAR T cells with OCI-AML2 and THP1 but not with K562 and 293T cells (Figure 1D). The cytolytic activity of PRAME mTCR CAR T cells extended to primary AML specimens expressing the PRAME ALY: HLA-A*02 antigen (data not shown). In-vivo efficacy of PRAME mTCR CAR T was demonstrated in OCI-AML2 and THP-1 CDX models (Figure 1E). Treatment with CAR T cells induced leukemia clearance and significantly reduced leukemia burden in OCI-AML2 and THP-1 xenograft mice, respectively, while treatment with unmodified T cells exhibited leukemia progression (Figure 1E). The anti-leukemia activity of CAR T cells resulted in enhanced survival in OCI-AML2 (p=0.0035) and THP-1 (p=0.0047) xenografts (Figure 1F). The in-vivo activity of PRAME mTCR CAR T cells was target specific, as treatment with CAR T cells did not affect leukemia burden and survival in K562 xenograft mice (Figure 1F). Given that IFN-γ promotes PRAME presentation, we investigated whether treatment of IFN-γ would enhance cytolytic activity of PRAME mTCR CAR T cells. OCI-AML2 and THP-1 cells pretreated with IFN-γ were more sensitive to cytolysis compared to untreated controls (Figure 1G). In this study, we demonstrate the therapeutic potential of targeting PRAME with mTCR CAR T cells in AML. We show potent, target-specific reactivity of PRAME mTCR CAR T cells against PRAME ALY: HLA-A*02 positive AML cells, both in-vitro and in-vivo. We further demonstrate that the activity of PRAME mTCR CAR T cells can be enhanced with IFN-γ treatment, providing a useful strategy to increase efficacy. Thus, the results presented provide a novel approach to target PRAME with CAR T cells and compelling data to evaluate PRAME mTCR CAR T cells in AML clinical trials. Figure 1 Figure 1. Disclosures Pardo: Hematologics, Inc.: Current Employment. Hylkema: Quest Diagnostics Inc: Current equity holder in publicly-traded company; Moderna: Current equity holder in publicly-traded company. Scheinberg: Eureka Therapeutics: Current equity holder in publicly-traded company.


Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1675-1675
Author(s):  
Ashish Sharma ◽  
Anne Roe ◽  
Filipa Blasco Lopes ◽  
Ruifu Liu ◽  
Jane Reese ◽  
...  

Abstract BACKGROUND: Chimeric antigen receptor (CAR) T cells have shown enormous promise in the treatment of certain B cell malignancies. Access to treatment is still limited due to a variety of issues, including pricing and centralized manufacturing models. Generation of CAR-T cells using an automated platform, followed by rigorous functional phenotyping, may contribute to the development of a robust long-lasting therapy. METHODS: Here, we used the Miltenyi Prodigy (Miltenyi Biotech, Bergisch Gladbach, Germany) to automate the process of manufacturing genetically manipulated T cells in a closed system. The system obviates the need for clean room infrastructure. We tested the feasibility of utilizing the Miltenyi Prodigy to manufacture CAR-T cells using a CD19 scFV vector with the 4-1BB co-stimulatory domain. (Lentigen Technology, Inc, Gaithersburg, MD). The purity, differentiation capacity and effector function of the enriched CAR-T cells was studied using high-dimensional flow cytometry. Finally, the functional potential of these cells was tested in vitro and by treating NOD-SCID-gamma (NSG) mice infused with B cell lymphoma cells (Raji B cell), with the CAR-T cells. RESULTS: Starting with 1 x 108 CD4 and CD8 cells from donor apheresis products, CAR-T cells were expanded for 12 days in culture media containing with TransAct (Miltenyi Biotech), IL7 and IL15. The mean fold-expansion at day 12 was 44 ± 5.6, range 39-50 (n=3). The mean transduction efficiency of CAR-T vector was 20%, range 10-25% (n=3), which is similar to other reported methods. The CD19 CAR-T product was enriched in both the CD4 and CD8 T cells subsets, and showed high-level of cytotoxicity against CD19+ cell lines in vitro and in vivo (Figure 1: Mice treated with the CD19-CAR T demonstrated a marked reduction in disease burden as compared to T cell control as measured by bioluminescence imaging and flow cytometric analysis). The CAR-T product was enriched in cell subsets with both effector (CD27-CCR7-; ~20% of total cells) and central memory phenotypes (CD27+CCR7+; ~30% of total T cells). The effector CD4 and CD8 T cells showed increased expression of major functional T cell differentiation transcription factors (i.e. T-bet and GATA3) critical for the development of anti-tumor responses. Whereas, the central CD4 and CD8 T cells were enriched for the expression of TCF7 (a stemness related member of the WNT signaling known to increase longevity of these cells). The frequencies and phenotypes of these cells were maintained in peripheral blood of NSG mice infused with B cell lymphoma cells (Raji B cells), 1 week after treatment. A significant expansion of CD8+ effector T cells and a dramatic reduction in tumor burden was observed over the next 4 weeks in all major organs. Interestingly, we observed that smaller proportion of central-memory like cells (with higher TCF7 levels) continued to persist 6 weeks post-treatment, potentially contributing to a long-lived recallable response. Based on these data we have initiated a phase 1 clinical trial to test the therapeutic potential of the CAR-T product in patients with advanced/refractory B cell lymphoma. The first clinical grade manufacturing run resulted in a CD19 + cell yield of 1.4 x109. CONCLUSION: Our data highlight that the automated CAR-T generation platform (i.e. Miltenyi Prodigy) is effective at the generating purified functionally competent CAR-T cells. Further, findings from our phenotyping analyses show that the CAR-T product is enriched in both effector and central memory subsets and is effective at tumor clearance in vivo. Thus far, we have treated one patient with CD19 CAR-T manufactured on this platform and 2 more have been enrolled. Though this initial study is based on CD19 CAR-T cells, the approach described here could easily be utilized to genetically engineer T cells with gene constructs that are more relevant for specific cancers and infectious diseases. Disclosures No relevant conflicts of interest to declare.


2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Derek P. Wong ◽  
Nand K. Roy ◽  
Keman Zhang ◽  
Anusha Anukanth ◽  
Abhishek Asthana ◽  
...  

AbstractB cell-activating factor (BAFF) binds the three receptors BAFF-R, BCMA, and TACI, predominantly expressed on mature B cells. Almost all B cell cancers are reported to express at least one of these receptors. Here we develop a BAFF ligand-based chimeric antigen receptor (CAR) and generate BAFF CAR-T cells using a non-viral gene delivery method. We show that BAFF CAR-T cells bind specifically to each of the three BAFF receptors and are effective at killing multiple B cell cancers, including mantle cell lymphoma (MCL), multiple myeloma (MM), and acute lymphoblastic leukemia (ALL), in vitro and in vivo using different xenograft models. Co-culture of BAFF CAR-T cells with these tumor cells results in induction of activation marker CD69, degranulation marker CD107a, and multiple proinflammatory cytokines. In summary, we report a ligand-based BAFF CAR-T capable of binding three different receptors, minimizing the potential for antigen escape in the treatment of B cell cancers.


Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 816-816 ◽  
Author(s):  
Mauro P. Avanzi ◽  
Dayenne G. van Leeuwen ◽  
Xinghuo Li ◽  
Kenneth Cheung ◽  
Hyebin Park ◽  
...  

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.


Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5812-5812
Author(s):  
Alla Dolnikov ◽  
Swapna Rossi ◽  
Ning Xu ◽  
Guy Klamer ◽  
Sylvie Shen ◽  
...  

Abstract T cells modified to express CD19-specific chimeric antigen receptors (CAR) have shown anti-tumour efficacy in early phase clinical trials in patients with relapsed and refractory B-cell malignancies. In addition to direct cytotoxicity, chemotherapeutic drugs can have an immunomodulatory effect both through enhancing the tumour-specific immune response and increasing the tumour’s susceptibility to immune mediated destruction. Hence, combining immunomodulatory chemotherapy and CAR T-cells is an attractive approach for eliminating tumours, particularly in advanced stages. 5-aza-2'-deoxycytidine (5-AZA) is a hypomethylating agent that induces terminal differentiation, senescence or apoptosis in haematological malignancies. Here, we have explored a CAR-based immunotherapy combined with 5-AZA to maximise the effect of the CAR T-cells against CD19+ B-cell leukaemia. A second generation CAR including CD3zeta and the CD28 co-stimulatory domain was cloned into the PiggyBac-transposon vector and was used to generate CAR19 -T cells. Cord blood -derived mononuclear cells (MNC) were transfected with CAR19-transposon/transposase plasmids and expanded with CD3/28 beads for 2 weeks in the presence of 20ng/ml IL2 and 10ng/ml IL7. CAR19 T-cells efficiently induced cytolysis of CD19+ leukaemia cells in vitro and exhibited anti-tumour activity in vivo in a xenograft mouse model of leukaemia. Pre-treatment with 5-AZA produced greater leukaemia cell cytolysis in vitro and maximised anti-tumour activity of CAR19 T-cells in vivo against xenograft primary leukaemia compared to 5-AZA or CAR19 T-cells alone. In vitro analysis revealed that pre-treatment with 5-AZA up-regulates CD19 expression in leukaemia cells and improves CAR19 T-cell recognition of target cells increasing the formation of effector/ target cell conjugates and target cell cytolysis. Therefore using 5-AZA pre-treatment can be particularly useful for B-cell leukaemias with reduced expression of CD19. We have also demonstrated that pre-treatment of target cells with 5-AZA potentiates the effect of CAR19 T-cells used at low dose or low effector:target (E:T) suggesting that even small numbers of CAR19 T-cells can mediate a potent antitumor effect when combined with 5-AZA pre-treatment of target cells. This is particularly important for patients receiving limited numbers of CAR T-cells or for patients with large leukaemic burden. In addition, we speculate that the enhanced cellular cytotoxicity produced by 5-AZA-conditioning may allow the infusion of decreased numbers of CAR19 T-cells. Disclosures No relevant conflicts of interest to declare.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2848-2848
Author(s):  
Boris Engels ◽  
Xu Zhu ◽  
Jennifer Yang ◽  
Andrew Price ◽  
Akash Sohoni ◽  
...  

Abstract Background: Extended T-cell culture periods in vitro deplete the CAR-T final product of naive and stem cell memory T-cell (T scm) subpopulations that are associated with improved antitumor efficacy. YTB323 is an autologous CD19-directed CAR-T cell therapy with dramatically simplified manufacturing, which eliminates complexities such as long culture periods. This improved T-Charge™ process preserves T-cell stemness, an important characteristic closely tied to therapeutic potential, which leads to enhanced expansion ability and greater antitumor activity of CAR-T cells. Methods: The new T-Charge TM manufacturing platform, which reduces ex vivo culture time to about 24 hours and takes &lt;2 days to manufacture the final product, was evaluated in a preclinical setting. T cells were enriched from healthy donor leukapheresis, followed by activation and transduction with a lentiviral vector encoding for the same CAR used for tisagenlecleucel. After ≈24 hours of culture, cells were harvested, washed, and formulated (YTB323). In parallel, CAR-T cells (CTL*019) were generated using a traditional ex vivo expansion CAR-T manufacturing protocol (TM process) from the same healthy donor T cells and identical lentiviral vector. Post manufacturing, CAR-T products were assessed in T-cell functional assays in vitro and in vivo, in immunodeficient NSG mice (NOD-scid IL2Rg-null) inoculated with a pre-B-ALL cell line (NALM6) or a DLBCL cell line (TMD-8) to evaluate antitumor activity and CAR-T expansion. Initial data from the dose escalation portion of the Phase 1 study will be reported separately. Results: YTB323 CAR-T products, generated via this novel expansionless manufacturing process, retained the immunophenotype of the input leukapheresis; specifically, naive/T scm cells (CD45RO -/CCR7 +) were retained as shown by flow cytometry. In contrast, the TM process with ex vivo expansion generated a final product consisting mainly of central memory T cells (T cm) (CD45RO +/CCR7 +) (Fig A). Further evidence to support the preservation of the initial phenotype is illustrated by bulk and single-cell RNA sequencing experiments, comparing leukapheresis and final products from CAR-Ts generated using the T-Charge™ and TM protocols. YTB323 CAR-T cell potency was assessed in vitro using a cytokine secretion assay and a tumor repeat stimulation assay, designed to test the persistence and exhaustion of the cell product. YTB323 T cells exhibited 10- to 17-fold higher levels of IL-2 and IFN-γ secretion upon CD19-specific activation compared with CTL*019. Moreover, YTB323 cells were able to control the tumor at a 30-fold lower Effector:Tumor cell ratio and for a minimum of 7 more stimulations in the repeat stimulation assay. Both assays clearly demonstrated enhanced potency of the YTB323 CAR-T cells in vitro. The ultimate preclinical assessment of the YTB323 cell potency was through comparison with CTL*019 regarding in vivo expansion and antitumor efficacy against B-cell tumors in immunodeficient NSG mouse models at multiple doses. Expansion of CD3+/CAR+ T-cells in blood was analyzed weekly by flow cytometry for up to 4 weeks postinfusion. Dose-dependent expansion (C max and AUC 0-21d) was observed for both YTB323 and CTL*019. C max was ≈40-times higher and AUC 0-21d was ≈33-times higher for YTB323 compared with CTL*019 across multiple doses. Delayed peak expansion (T max) of YTB323 by at least 1 week compared with CTL*019 was observed, supporting that increased expansion was driven by the less differentiated T-cell phenotype of YTB323. YTB323 controlled NALM6 B-ALL tumor growth at a lower dose of 0.1×10 6 CAR+ cells compared to 0.5×10 6 CAR+ cells required for CTL*019 (Fig B). In the DLBCL model TMD-8, only YTB323 was able to control the tumors while CTL*019 led to tumor progression at the respective dose groups. This ability of YTB323 cells to control the tumor at lower doses confirms their robustness and potency. Conclusions: The novel manufacturing platform T-Charge™ used for YTB323 is simplified, shortened, and expansionless. It thereby preserves T-cell stemness, associated with improved in vivo CAR-T expansion and antitumor efficacy. Compared to approved CAR-T therapies, YTB323 has the potential to achieve higher clinical efficacy at its respective lower doses. T-Charge™ is aiming to substantially revolutionize CAR-T manufacturing, with concomitant higher likelihood of long-term deep responses. Figure 1 Figure 1. Disclosures Engels: Novartis: Current Employment, Current equity holder in publicly-traded company. Zhu: Novartis: Current Employment, Current equity holder in publicly-traded company. Yang: Novartis: Current Employment, Patents & Royalties. Price: Novartis: Current Employment. Sohoni: Novartis: Current Employment. Stein: Novartis: Current Employment. Parent: Novartis: Ended employment in the past 24 months; iVexSol, Inc: Current Employment. Greene: iVexSol, Inc: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Niederst: Novartis: Current Employment, Current equity holder in publicly-traded company. Whalen: Novartis: Current Employment. Orlando: Novartis: Current Employment. Treanor: Novartis: Current Employment, Current holder of individual stocks in a privately-held company, Divested equity in a private or publicly-traded company in the past 24 months, Patents & Royalties: no royalties as company-held patents. Brogdon: Novartis Institutes for Biomedical Research: Current Employment.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2788-2788
Author(s):  
Quy Le ◽  
Sommer Castro ◽  
Thao T. Tang ◽  
Cynthia Nourigat-Mckay ◽  
LaKeisha Perkins ◽  
...  

Abstract Background: A rare but highly aggressive type of AML that is only seen in infants with a unique immunophenotype (RAM phenotype) is caused by cryptic CBFA2T3-GLIS2 (CBF/GLIS) fusion. This infant AML is highly refractory to conventional chemotherapy with near uniform fatality despite highly intensive and myeloablative therapy (PMID 23153540). Transcriptome profiling of CBF/GLIS AML has revealed new insights into the pathogenesis of the fusion and uncovered fusion-specific molecular biomarkers that could be used for risk stratification and to inform treatment (PMID 30592296). Studying the largest cohort of these high-risk infants, we demonstrated several alterations in gene expression and transcriptional networks in these CBF/GLIS-positive patient samples that have potential for therapeutic targeting (PMID 31719049). FOLR1, which encodes for folate receptor alpha, was highly and uniquely expressed in CBF/GLIS AML but was entirely absent in AML with other cytogenetics abnormalities and in normal hematopoietic cells. Furthermore, we recently demonstrated that forced expression of CBF/GLIS enhances the proliferation and alters differentiation in cord blood (CB) CD34+ early precursors towards megakaryocytic lineage that recapitulates acute megakaryocytic leukemia seen in infants (PMID 31719049). Of significance, we showed that FOLR1 surface expression is causally linked to CBF/GLIS-induced malignant transformation, thus making it an attractive antigen for targeted therapies against CBF/GLIS AML cells. Given that chimeric antigen receptor (CAR) T cells are extremely effective at eradicating relapsed/refractory B-ALL malignancies, we developed FOLR1-directed CAR T cells for pre-clinical evaluation in CBF/GLIS AML. Methods: We generated a FOLR1-directed CAR using anti-FOLR1 binder (Farletuzumab), IgG4 intermediate spacer and 41-BB/CD3zeta signaling domains. The pre-clinical efficacy of FOLR1 CAR T cells was evaluated against CBF/GLIS AML cell lines in vitro and in vivo. CBF/GLIS AML models include CB CD34+ cells transduced with CBF/GLIS expression construct (CBF/GLIS-CB) and WSU-AML cell line. We also engineered Kasumi-1 cell line to express FOLR1 (Kasumi-1 FOLR1+) to evaluate target specificity (Figure 1A). Results: We tested the target specificity of FOLR1-directed CAR T cells against FOLR1-positive (CBF/GLIS-CB, WSU-AML, Kasumi-1 FOLR1+) and FOLR1-negative (Kasumi-1) cells. CD8 FOLR1 CAR T cells demonstrated cytolytic activity against FOLR1 positive but not FOLR1 negative cells (Figure 1B). Furthermore, both CD8 and CD4 FOLR1 CAR T cells produced higher levels of IL-2, IFN-γ, and TNF-α and proliferated more robustly than did unmodified T cells when co-incubated with FOLR1 positive but not FOLR1 negative cells (Figure 1C). These results indicate highly specific reactivity of FOLR1 CAR T cells against AML cells expressing FOLR1. We next investigated the in vivo efficacy of FOLR1-directed CAR T cells. In CBF/GLIS-CB, WSU-AML, and Kasumi-1 FOLR1+ xenograft models, treatment with FOLR1 CAR T cells induced leukemia clearance, while disease progression occurred in all mice that received unmodified T cells (Figure 1D). Activity of FOLR1 CAR T cells in vivo was target specific, as they did not limit the leukemia progression nor extend the survival of Kasumi-1 xenografts (Figure 1D). To determine whether FOLR1 is expressed on normal HSPCs, we characterized FOLR1 expression in normal CB CD34+ samples. FOLR1 expression was entirely silent in HSPC subsets (Figure 1E). Consistent with lack of expression, no cytolytic activity was detected against HPSCs Moreover, FOLR1 CAR T cells did not affect the self-renewal and multilineage differentiation capacity of normal HSPCs as compared to unmodified control T cells (Figure 1F), whereas significant eradication of colonies were detected in the CBF/GLIS-CB cells (Figure 1G). Conclusion: In this study, we demonstrate that FOLR1 CAR T effectively eradicates CBF/GLIS AML cells without compromising normal HSPCs, providing a promising approach for the treatment of high-risk CBF/GLIS AML. Transition of this CAR T to clinical development for infant AML is underway. Figure 1 Figure 1. Disclosures Hylkema: Moderna: Current equity holder in publicly-traded company; Quest Diagnostics Inc: Current equity holder in publicly-traded company. Pardo: Hematologics, Inc.: Current Employment. Eidenschink Brodersen: Hematologics, Inc.: Current Employment, Other: Equity Ownership. Loken: Hematologics, Inc.: Current Employment, Other: current equity holder in a privately owned company.


Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 34-35
Author(s):  
Moriah Rabin ◽  
Mengyan Li ◽  
Scott Garforth ◽  
Jacqueline Marino ◽  
Jian Hua Zheng ◽  
...  

Background: While chimeric antigen receptor T cells (CAR T-cells) induce dramatic remissions of refractory or recurrent B cell malignancies, the durability of these remissions is frequently limited by subsequent reduction in circulating CAR T-cells and/or by diminution of their effector function. We hypothesized that we could overcome this therapeutic limitation and increase the functional activity and longevity of CAR T-cells by selectively deriving them from virus-specific effector memory T cells. We have developed biologics we termed synTacs (artificial immunological synapse for T-cell activation), which selectively activate and expand antigen-specific CD8+ T cells in vitro and in vivo by recapitulating signals delivered at the immunological synapse. The synTacs consist of dimeric Fc domain scaffolds linking CD28- or 4-1BB-specific ligands to HLA-A2 MHC molecules covalently tethered to virus-derived peptides. Treatment of PBMCs from CMV-exposed donors with synTacs presenting a CMV-derived peptide (pp65-NLVPMVATV) induce vigorous and selective ex vivo and in vivo expansion of highly functional CMV-specific CD8+ T cells, with potent antiviral activity. We used these synTacs to selectively generate CAR T-cells from CMV-specific effector memory CD8+ T cells, which could be further expanded by restimulation with the CMV-specific synTacs. Methods: We treated PBMCs from CMV-exposed donors in media supplemented with either IL-2 or IL-7/12/15 with a synTac containing the CMV-derived pp65 peptide presented by HLA-A2 MHC molecules linked to ligands capable of stimulating CD28- or 4-1BB-dependent costimulatory pathways. PBMCs activated either with anti-CD3/CD28 or the CMV-specific synTacs were transduced with lentivirus expressing an anti-CD19 CAR and a GFP reporter gene. CMV-specific CD8+ T cells were quantified by tetramer staining and CAR T-cells were detected by GFP expression determined by flow cytometric analysis. The functional activity of the CD19 CAR T-cells was determined by a B cell-specific cytotoxic assay. Results: After 7 days, treatment of PBMCs with CMV-specific synTacs rapidly induced robust activation and &gt;50-fold expansion of CMV-specific CD8+ T cells expressing effector memory markers. Treatment of the PBMCs with CMV-specific synTacs selectively activated CMV-specific T cells and enabled them to be specifically transduced with a CD19-specific CAR lentivirus and converted into CD19 CAR T-cells. These CMV-specific CD19 CAR T-cells displayed potent dose-responsive cytotoxic activity targeting purified primary B cells. Furthermore, these CMV-specific CD19 CAR T-cells could be selectively expanded by in vitro treatment with CMV-specific synTacs. Conclusions: SynTacs are versatile immunotherapeutics capable of selective in vitro and in vivo activation and expansion of virus-specific CD8+ T cells with potent antiviral cytotoxic activity. After selective lentiviral transduction and conversion into CD19 CAR T-cells, their co-expression of the CMV-specific T cell receptor enabled them to be potently stimulated and activated by in vitro treatment with CMV synTacs. The modular design of synTacs facilitates efficient coupling of other costimulatory ligands - such as OX40 or GITRL - or cytokines, such as IL-2, IL-7, or IL-15, to enable the selective in vivo delivery of defined costimulatory signals or cytokines to the CAR T-cells expressing CMV-specific TCR. This strategy has the potential to boost the in vivo activity of tumor-specific CAR T-cells after infusion and enable more durable and potent treatment of refractory/recurrent B cell malignancies. Disclosures Almo: Cue Biopharma: Current equity holder in publicly-traded company, Patents & Royalties: Patent number: 62/013,715, Research Funding. Goldstein:Cue Biopharma: Research Funding.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1717-1717
Author(s):  
Matthew A Nix ◽  
William C Temple ◽  
William Karlon ◽  
Donghui Wang ◽  
Paul Phojanakong ◽  
...  

Abstract Background: Approximately 50% of pediatric B-ALL patients treated with clinically approved CD19-targeting CAR-T cells do not remain in remission one year after therapy. CD22-targeting CAR-T cells appear to be curative in only a small fraction of CD19-refractory patients and this therapeutic strategy is primarily used as a bridge to stem cell transplant. Additional immunotherapeutic targets thus remain urgently needed. Our laboratory recently used cell surface proteomics to identify CD72 as a B-cell specific marker especially upregulated on poor prognosis, KMT2A/MLL-rearranged B-ALL (Nix et al., Cancer Discovery (2021)). In this published work, we used a best-in-class nanobody library displayed on yeast to develop binders to CD72. We demonstrated for the first time that fully synthetic nanobodies can generate CAR-T cells that are highly potent in vitro and in vivo. While we previously focused on these "nanoCARs" in KMT2A/MLLr B-ALL, in this follow-up study we aimed to 1) further expand our nanoCAR indications to other CD72-expressing B-cell malignancies; 2) biophysically characterize our synthetic nanobodies; 3) evaluate the potential for further humanization of the nanobody binder amino acid sequence while retaining anti-tumor efficacy; and 4) characterize the potency and T-cell immunophenotypes in the context of our lead nanobody binder ("NbD4") placed on different CAR backbones. Methods: Flow cytometry of primary patient samples for CD72 was performed in a CLIA-certified laboratory. NbD4 nanobody was recombinantly expressed in E. coli and biolayer interferometry was used to determine the binding affinity to recombinantly-expressed CD72 extracellular domain. CAR-T cells were generated from peripheral blood donor CD4+ and CD8+ cells (1:1) ratio via lentiviral transduction. In vitro cytotoxicity assays were performed at a range of effector:tumor ratios. In vivo studies were performed in human cell line orthotopic xenografts in NSG mice. 1e6 luciferase-labeled Jeko cells were implanted at Day 0 followed by administration of 4e6 CAR-T cells at Day 6. Tumor burden was assessed by bioluminescence. Results: Flow cytometry on primary non-Hodgkin B-cell lymphoma obtained from fine needle aspiration biopsy (n = 5) confirmed CD72 surface expression (not shown), consistent with RNA-seq across larger cohorts. Biolayer interferometry demonstrated that NbD4 bound with surprisingly low affinity to recombinant CD72 (K D ~800 nM) (Fig. 1A), with both slow on rate (k on 8.38e4 M -1s -1) and rapid off rate (k off 6.82e-2 s -1). This affinity stands in contrast to that reported for FMC63 single chain variable fragment (scFv) used in clinically approved CD19-targeting CAR-T cells (K D 0.3-5 nM), despite similar in vitro and in vivo efficacy of both products. Our NbD4 framework region shows ~82% homology to a human IgG variable heavy domain, significantly higher than FMC63 (~59% homology). We made additional substitutions in the framework domain to increase human homology up to 89%. In vitro cytotoxicity assays with SEM B-ALL cells showed several humanized variants with similar efficacy to NbD4 (Fig. 1B). We further evaluated the impact of placing NbD4 on different CAR backbones, including combinations of CD28 or 4-1BB costimulatory domains and CD8 or IgG4-based transmembrane and hinge regions (Fig. 1C). In vivo, CD72 nanoCARs with Backbone 3 showed significantly increased potency (Fig. 1D). Indeed, tumors treated with Backbone 3 CAR-Ts showed complete tumor clearance and did not develop new tumors even after re-challenge with 1e6 Jeko cells at Day 52 (Fig. 1D). Preliminary characterization of effector and memory CAR-T cell phenotypes before exposure to tumor suggested that Backbone 3 had an increased number of naïve T cells compared to empty CAR and CD19 CAR-T cells (data not shown). Conclusions: Our results demonstrate that our fully synthetic CD72 nanoCARs can effectively eliminate CD72-expressing B-cell malignancy models despite low nanobody binding affinity. Humanized NbD4 variants may serve as clinical candidates with even further reduction in possible immunogenicity of the llama amino acid framework. Alterations to the CAR backbone have a major impact on anti-tumor efficacy and phenotypes of our synthetic nanobodies. CD72-targeting therapies may be effective therapeutics not only KMT2A/MLLr B-ALL but also across a broader spectrum of refractory B-cell malignancies. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.


Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 23-24
Author(s):  
Agnes E. Hamburger ◽  
Breanna DiAndreth ◽  
Mark E. Daris ◽  
Melanie L. Munguia ◽  
Kiran Deshmukh ◽  
...  

Background: Chimeric Antigen Receptor (CAR) T-cell therapy is a proven, powerful clinical modality. However, it is still limited by the fundamental obstacle of cancer therapy: discriminating cancer from normal cells. Current FDA-approved CAR T-cell therapies eliminate normal B cells, leaving patients with B cell aplasia, hypogammaglobulinemia, and susceptible to infection. HLA-Class I loss of heterozygosity (LOH) occurs at an average frequency of ~13% among cancers and specifically ~13% in DLBCL (Broad Institute TCGA database). These losses are irreversible and distinguish the cancer from normal cells. To exploit LOH at the HLA locus, we target the remaining allelic product in tumors with LOH. We evaluated a novel AND NOT Boolean logic gate CAR T module (Tmod) T-cell system to target HLA-A*02 (A2) LOH in lymphoma using both in vitro and in vivo models. Methods: To model tumor cells that have lost A2 via LOH, we used CD19+ Raji lymphoma tumor cells. To model the corresponding "normal" cells, we established CD19+ Raji cells stably expressing A2 (CD19+/A2+ Raji). We then engineered human primary T cells to express a modular signal-integration circuit designed to be activated only by CD19+ lymphoma that do not express A2 (CD19+/A2- Raji). Each primary Tmod CAR T cell expresses both a CD19 activator (A) module using a CD19-targeting 3rd generation CAR, and a separate A2-targeting blocker (B) module using a novel A2-targeting inhibitory receptor. Human primary Tmod CAR T cells were engineered to co-express the A/B modules. First, T cells were stimulated via CD3/CD28 activation, followed by A/B module lentivirus transduction, and enriched for the B module. In vitro Tmod CAR T cells were evaluated for selective killing of CD19+/A2- Raji compared with CD19+/A2+ Raji. For in vivo proof of concept, both CD19+/A2- Raji and CD19+/A2+ Raji cell lines were injected and established into flanks of immunocompromised NGS mice and challenged with adoptive transfer of engineered human primary Tmod CAR T cells. Results: Engineered primary Tmod CAR T cells selectively killed CD19+/A2- Raji and spared CD19+/A2+ Raji (Figure 1). Tmod CAR T cells reversibly cycled from a state of non-killing, "block", to cytotoxicity and back, depending on the CD19+/A2- Raji vs. CD19+/A2+ Raji cells to which they were exposed. Importantly, primary Tmod CAR T cells selectively eliminated only the CD19+/A2- Raji cells in mixed cultures. In vivo, Tmod CAR T cells selectively eradicated CD19+/A2- Raji. More importantly, Tmod CAR T cells did not eradicate CD19+/A2+ Raji in vivo. Conclusions: CD19-targeting Tmod CAR T cells demonstrated robust and selective killing, distinguishing Raji lymphoma lines, one with A2 (CD19+/A2+) and one without (CD19+/A2-), both in vitro and in vivo. A critical requirement for Tmod CAR T-cell therapy is to determine reversibility and lack of anergy in the kill-"block"-kill and "block"-kill-"block" scenarios. This result demonstrates that Tmod CAR T cells do not terminally differentiate into one state (blockade or activation), but rather can switch back and forth as they integrate signals from "normal" and tumor cells. Furthermore, because Tmod CAR T cells can selectively target malignant B cells, it may increase the clinical therapeutic window for CAR T. Tmod CAR T cells may provide a powerful system to address hematologic malignancies and solid tumors with HLA-Class I LOH. Disclosures Hamburger: A2 Biotherapeutics: Current Employment, Current equity holder in private company. DiAndreth:A2 Biotherapeutics: Current Employment. Daris:A2 Biotherapeutics: Current Employment, Current equity holder in private company. Munguia:A2 Biotherapeutics: Current Employment, Current equity holder in private company. Deshmukh:A2 Biotherapeutics: Current Employment. Mock:A2 Biotherapeutics: Current Employment, Current equity holder in private company. Asuelime:A2 Biotherapeutics: Current Employment, Current equity holder in private company. Lim:A2 Biotherapeutics: Current Employment, Current equity holder in private company. Kreke:A2 Biotherapeutics: Current Employment, Current equity holder in private company; Gilead: Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Tokatlian:A2 Biotherapeutics: Current Employment, Current equity holder in private company. Maloney:A2 Biotherapeutics: Consultancy, Current equity holder in publicly-traded company, Honoraria; Bioline Rx: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Genentech: Consultancy, Honoraria; Gilead Science: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Juno Therapeutics: Consultancy, Honoraria, Patents & Royalties, Research Funding. Go:A2 Biotherapeutics: Current Employment, Current equity holder in private company; Amgen: Current equity holder in publicly-traded company; Allogene: Divested equity in a private or publicly-traded company in the past 24 months; Gilead: Current equity holder in publicly-traded company; Illumina: Divested equity in a private or publicly-traded company in the past 24 months. Kamb:A2 Biotherapeutics: Current Employment, Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.


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