We designed a CD19-targeted CAR comprising a calibrated signaling module, termed 1XX, that differs from that of conventional CD28/CD3z and 4-1BB/CD3z CARs. Here we report the first-in-human, phase 1 clinical trial of 19(T2)28z-1XX CAR T cells in relapsed/refractory large B-cell lymphoma. We hypothesized that 1XX CAR T cells may be effective at low doses and investigated 4 doubling dose levels starting from 25×106 CAR T cells. The overall response rate (ORR) was 82% and complete response (CR) rate 71% in the entire cohort (n=28) and 88% ORR and 75% CR in 16 patients treated at 25×106. With the median follow-up of 24 months, the 1-year EFS was 61% (95% CI: 45-82%). Overall, grade ≥3 CRS and ICANS rates were low at 4% and 7%. The calibrated potency of the 1XX CAR affords excellent efficacy at low cell doses and may benefit the treatment of other hematological malignancies, solid tumors and autoimmunity.

Supplementary Figure 1 Legend from Immunoediting Sculpts Tumor Epitopes during Immunotherapy

Modakafusp alfa (moda), a novel immunocytokine, is an innate immunity enhancer comprising two attenuated interferon (IFN) α2b molecules fused to an anti-CD38 IgG4 monoclonal antibody backbone, driving preferential IFNα signalling in CD38-expressing innate and adaptive immune cells as well as myeloma cells. Here, we present pharmacodynamic (PD) data from the first-in-human Phase 1/2 study of moda as a monotherapy in patients with RRMM (iinnovate-1; NCT03215030). A total of 37 patients treated with moda at 1.5 or 3 mg/kg every 4 weeks were included in the analysis. Peripheral blood (PB) and bone marrow (BM) samples were collected during screening or pre-dose on cycle 1 day 1 (C1D1) and at multiple timepoints after treatment. BM and PB samples were evaluated by cytometry time of flight (CyTOF) and bulk RNA sequencing (RNAseq) to assess pharmacodynamic changes in immune cell populations, cell activation, and gene expression. Administration of moda led to enhanced innate immune cell activation and cytotoxic function as demonstrated by increased proportions of CD69+ and granzyme B+ in peripheral NK cells analyzed by CyTOF. This was accompanied by a decrease in the proportion of TIGIT+ NK cells, indicating reduced inhibitory signaling. Furthermore, enhanced proliferation (%Ki67+) of NK cells was observed in both BM and PB. Moda also impacted myeloid cell populations in BM and PB. Dendritic cells (DCs) and monocytes in PB showed increased surface expression of the co-stimulatory molecule CD86, suggesting a potential for enhanced antigen presentation and co-stimulation ability. Increased proliferation (%Ki67) of DCs and monocytes was detected in both PB and BM, accompanied by a decrease in numbers of peripheral DCs which may indicate recruitment or homing to secondary lymphoid organs. Additionally, RNAseq analysis revealed that treatment with moda led to upregulation of CD68 expression in both PB and BM, indicating a proinflammatory M1 macrophage type response. Finally, CyTOF analysis also indicated that moda significantly impacted adaptive immunity. We observed enhanced activation (%CD69, %PD1 and %CD40L) and cytotoxic function (%granzyme B) of peripheral CD8 T cells, and increased CD8 T cell proliferation (%Ki67 CD8) in both PB and BM samples. Enhanced activation of peripheral CD4 T cells (%CD69, %CD40L) was also detected. Consistent with activation of the adaptive immune system, there was a reduction in naïve CD8 T cells accompanied by an increase in CD8 T effector memory cells in PB. Analysis of exhaustion markers (TIGIT, PD-1) in cycle 1 (C1D8, C1D15, and C2D1 predose) showed that moda did not induce CD8 T cell exhaustion in either PB or BM, and there was no change in FoxP3+ Treg cells. Moda-induced innate and adaptive immune cell phenotypic changes were evaluated for correlation with clinical response at timepoints with sufficient number of evaluable samples. While none of the associations were statistically significant after correcting for multiplicity testing (using the false discovery rate method), we observed trends warranting further investigation. There was a greater increase of CD40L+ NK cells and PD1+ CD8 cells in responders vs. non-responders at C1D2. Additionally, at C1D15 responders showed a lower increase in proliferation (%Ki67+) of classical monocytes, NK cells, and myeloid DCs in PBas compared to non-responders. A similar trend was also observed in the BM classical monocytes. Even though the peak of Ki67 expression was observed at C1D8, diminished increases of proliferating cells at C1D15 in responders was a surprising observation that needs further consideration. The PD biomarker data from this first-in-human clinical trial demonstrated that treatment with moda enhances both innate and adaptive immune cell activation in PB and BM. Importantly, moda-mediated immune activation did not result in T cell exhaustion during cycle 1, as evaluated in both PB and BM. We have observed interesting trends of immune phenotypic changes that may correlate with response. Follow-up analyses of the correlation of biomarkers with clinical response are in progress and will be presented. Further clinical trials are underway (iinnovate-2, NCT05556616; iinnovate-3, NCT05590377) to evaluate moda's novel immune activating mechanism in combination with standard of care anti-myeloma therapies.

TAK-940 (CD19(T2)28z1XX Chimeric Antigen Receptor (CAR) T) is an autologous CD19 CAR T cell therapy utilizing an optimized 1XX signaling domain substituting for the natural CD3ζ immunoreceptor tyrosine-based activation motifs. This 1XX design extends the functional persistence of CAR T cells with increased potency in mice (Feucht J et al. Nat Med 2019). TAK-940 is being evaluated in a Ph1 trial in patients with Relapsed or Refractory B-cell malignancies (NCT04464200) with demonstrated early signals of clinical efficacy (Park J et al. ASH 2022). The present study aims to provide a better understanding of the clinical performance of CD19(T2)28z1XX CAR T cells by in depth characterization of the cellular products and patient samples from this Ph1 trial. A total of 28 subjects were enrolled and treated in the dose escalation and expansion cohorts of the Ph1 trial. Responses were observed across all dose levels (25x10 6 to 200x10 6 CAR T cells), achieving ORR 82%, CR 71%. Immunophenotyping by flow cytometry was conducted on patient apheresis material, un-transduced cells, transduced cellular drug product and peripheral blood samples from infused subjects. Circulating cytokine profiling was performed on patient serum samples collected pre and post treatment with TAK-940. In the transduced cellular drug products, CAR+ and CAR- CD8+ central memory and transitional memory T cells were more abundant than naïve, stem cell memory or terminal effector populations. This elevation in central and transitional memory T cells seen in the drug product was not observed in the patient apheresis material, indicating that this effect is likely driven by the production process. CD57 and TIM3 expression in both CD4+ and CD8+ CAR+ T cells in the drug product showed a positive association with clinical response, while CTLA4 or LAG3 expression independently was negatively associated with response. The drug product also contained low numbers of dysregulated/exhausted T cells, with no observable difference between responders and non-responders. Interestingly, in the starting apheresis material, increased expression of TIM3 as well as decreased expression of either LAG3 or KLRG1 in CD8 T cells, independently associated with responses. Current analysis is based on associations with complete response. Additional analyses to be reported will include associations with ORR and durability of responses. These findings suggest potential utility of these T cell markers in predicting patient response and warrant evaluation in a larger population. Although CD57 expression has been associated with a senescent phenotype, we hypothesize that the observed increase in CD57 expression in CD4+ and CD8+ CAR+ T cells in the product may indicate higher cytotoxic potential of those cells. Increase in CD57+ CAR+ T cell subsets has been previously associated with durable CRs in large B cell lymphoma patients treated with axi-cel (Good Z et al. Nat Med 2022). Additional analyses to further characterize the CD57+ cell populations and establish their role in clinical responses to CAR T cell therapy with the 1XX CAR design are in progress. The increased expression of CD57 and the activation marker TIM3, and decreased expression of inhibitory receptors CTLA4 and LAG3 in the drug product from responders, together with the robust clinical responses observed with doses as low as 25x10 6 CAR T cells, suggest that the product consists of highly potent T cells, in accordance with the preclinical results obtained with the 1XX CAR. Low levels of circulating cytokines were observed following treatment with TAK-940, including IFNg, IL-6, IL-10, indicating a safe and tolerable CAR T product consistent with the observed clinical safety profile of TAK-940. Correlative analysis of T cell immunophenotypes observed in the product to clinical parameters including durability of responses, metabolic tumor volume/tumor burden, and induction of cytokines and chemokines is ongoing and will be reported. This will further contribute to our understanding of CD19 CAR T cells endowed with a 1XX signaling domain and potentially support the identification of product and/or apheresis biomarkers that may predict patient response.

Inflammation in cancer can both suppress tumor growth and promote tumorigenesis. In the tumor microenvironment (TME), inflammation characterized by inflammatory cells and other mediators including cytokines affects tumor development and progression and can have an impact on response to therapy. The inflammatory cytokine IL-1b is upregulated in several conditions including rheumatoid arthritis, chronic obstructive pulmonary disease, inflammatory bowel disease, as well as in different cancers including breast, gastric, pancreatic, and lung cancers. IL-1b contributes to the generation and accumulation of myeloid-derived suppressor cells (MDSCs). In the tumor microenvironment, MDSCs consist of a mixture of immature macrophages, immature dendritic cells and neutrophils, which can suppress the function of antitumor T cells. In addition, IL-1b is produced via activation of the inflammasome, which has been shown to promote the infiltration of MDSCs and tumor-associated macrophages (TAMs) into the TME. Downstream of IL-1b production are other inflammatory cytokines such as IL-6, IL-8, and IL-17, which can also suppress the immune system. Recently published data show that blocking IL-1b in patients without cancer can lead to a decrease in fatal cancer and more specifically lung cancer incidences and fatalities (Ridker et al., 2017). While the study was not designed to study the anticancer effects of canakinumab (Ilaris), this finding has led to increased interest in understanding the role of IL-1b and IL-1b blockade in cancer development and progression. Emerging data aim to elucidate the role of IL-1b blockade on tumor growth and progression, as well as characterize changes to tumor-infiltrating lymphocyte (TIL) populations and their function after treatment with an anti-IL-1b antibody. Reference: Ridker PM et al. Effect of interleukin-1b inhibition with canakinumab on incident lung cancer in patients with atherosclerosis: exploratory results from a randomized, double-blind, placebo-controlled trial. Lancet 2017;390:1833-42. Citation Format: Reshma Singh, Rohan Diwanji, Pushpa Jayaraman, Derek Chiang, Catherine Sabatos-Peyton, Glenn Dranoff. Anti IL-1b as a cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A76.

Abstract Cluster of differentiation 28 (CD28) and programmed death receptor 1 (PD-1) are members of the CD28 superfamily of co-receptors that have critical roles in the regulation of T cell-mediated immunity and inflammation. Ligation of CD28 synergizes with T cell receptor (TCR) signaling to enhance T cell activation through the PI3K-Akt pathway, while PD-1 ligation by its ligands (PD-L1/L2) sequesters critical mediators of signaling from the TCR complex, thereby shunting T cell activation and effector function. Thus, the expression of PD-L1/L2 in solid tumors may pose a significant barrier to anti-tumor immunity and the efficacy of adoptive T cell therapies (ACT). We have recently described a novel class of engineered T cells that integrate a T cell receptor fusion construct (TRuC®) into the natural TCR complex, thereby reprogramming the specificity of the T cell to recognize tumor surface antigen in a human leukocyte antigen (HLA)-independent fashion. TC-210 T cells expressing mesothelin (MSLN) specific TRuCs demonstrate robust anti-tumor immunity in preclinical models of mesothelioma, protecting mice from tumor re-challenge while inducing lower levels of inflammatory cytokine release when compared to a 2nd generation MSLN-targeted CAR T. Here, we show that co-expression of a PD-1:CD28 switch receptor comprising the PD-1 extracellular domain fused to the CD28 intracellular domain, enhances the activity of TC-210 T cells. When compared to TC-210 expressing only the TRuC, co-expression of PD1:CD28 was able to restore PD-L1 mediated inhibition of cytokine production and proliferation in co-culture with tumor cells. In vivo and molecular mechanistic studies are currently underway. Citation Format: Derrick P. McCarthy, Sarah Guyette, Michael Lofgren, Jyothi Sethuraman, Thamara DeSilva, Ahmar Aziz, Troy Patterson, Shruti Datari, Tiffany Chan, Philippe Kieffer-Kwon, Christopher J. Rold, Reshma Singh, Jian Ding, Holly Horton, R. Anthony Barnitz, Andrew Cornforth, Robert Tighe, Robert J. Hofmeister, Dario A. Gutierrez. A chimeric PD1-CD28 switch receptor enhances the activity of TRuC-T cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 893.

Inflammation in cancer can both suppress tumor growth and promote tumorigenesis. In the tumor microenvironment (TME), inflammation characterized by inflammatory cells and other mediators including cytokines affects tumor development and progression and can have an impact on response to therapy. The inflammatory cytokine IL-1b is upregulated in several conditions including rheumatoid arthritis, chronic obstructive pulmonary disease, inflammatory bowel disease, as well as in different cancers including breast, gastric, pancreatic, and lung cancers. IL-1b contributes to the generation and accumulation of myeloid-derived suppressor cells (MDSCs). In the tumor microenvironment, MDSCs consist of a mixture of immature macrophages, immature dendritic cells and neutrophils, which can suppress the function of antitumor T cells. In addition, IL-1b is produced via activation of the inflammasome, which has been shown to promote the infiltration of MDSCs and tumor-associated macrophages (TAMs) into the TME. Downstream of IL-1b production are other inflammatory cytokines such as IL-6, IL-8, and IL-17, which can also suppress the immune system. Recently published data show that blocking IL-1b in patients without cancer can lead to a decrease in fatal cancer and more specifically lung cancer incidences and fatalities (Ridker et al., 2017). While the study was not designed to study the anticancer effects of canakinumab (Ilaris), this finding has led to increased interest in understanding the role of IL-1b and IL-1b blockade in cancer development and progression. Emerging data aim to elucidate the role of IL-1b blockade on tumor growth and progression, as well as characterize changes to tumor-infiltrating lymphocyte (TIL) populations and their function after treatment with an anti-IL-1b antibody. Reference: Ridker PM et al. Effect of interleukin-1b inhibition with canakinumab on incident lung cancer in patients with atherosclerosis: exploratory results from a randomized, double-blind, placebo-controlled trial. Lancet 2017;390:1833-42. Citation Format: Reshma Singh, Rohan Diwanji, Pushpa Jayaraman, Derek Chiang, Catherine Sabatos-Peyton, Glenn Dranoff. Anti IL-1b as a cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A76.

Multiple myeloma has a continued need for more effective and durable therapies. B cell maturation antigen (BCMA), a plasma cell surface antigen and member of the tumor necrosis factor (TNF) receptor superfamily, is an attractive target for immunotherapy of multiple myeloma due to its high prevalence on malignant plasma cells. The current work details the pre-clinical evaluation of BCMA expression and development of a chimeric antigen receptor (CAR) targeting this antigen using a fully human single chain variable fragment (scFv). We demonstrate that BCMA is prevalently, but variably expressed by all MM with expression on 25-100% of malignant plasma cells. Extensive Immunohistochemical analysis of normal tissue expression using commercially available polyclonal antibodies demonstrated expression within B-lineage cells across a number of tissues as expected. Based upon the highly restricted expression of BCMA within normal tissues, we generated a set of novel, fully human scFv binding domains to BCMA by screening a naïve B-cell derived phage display library. Using a series of in vitro and pre-clinical in vivo studies, we identified a scFv with high specificity for BCMA and robust anti-myeloma activity when used as the binding domain of a second-generation CAR bearing a CD137 costimulatory domain. This BCMA-specific CAR is currently being evaluated in a Phase 1b clinical study in relapsed and refractory MM patients (NCT02546167).

Chemo-refractory acute myeloid leukemia (AML) is associated with poor prognosis and treatment options are extremely limited. Chemo-refractory AML is thought to arise due to selection pressure of resistant clones from prior use of chemotherapy or in some cases pre-exist due to properties of the leukemic stem cells (LSC). CLEC12A (also known as CLL1) has previously been described as being selectively over expressed in LSCs. Successful modalities to target CLEC12A and eradicate the LSC would overcome chemo-refractoriness in AML and would represent a vertical advance in the field. In this study, we confirm that CLEC12A is heterogenously expressed on AML blasts and over-expressed on AML LSC. We also show that CLEC12A is overexpressed on bone marrows from patients with AML that fail to achieve a complete remission after induction chemotherapy, suggesting that it could be a marker for residual disease that is refractory to chemotherapy. We then separated AML blasts into CLEC12A positive or negative cells by magnetic sorting. CLEC12A positive blasts were more resistant to chemotherapy compared to CLEC12A negative blasts (killing of 20% versus 43%, respectively when cultured with cytarabine 10 mg/ml, P = .01). We then evaluated CLEC12A resistance to chemotherapy in a patient derived AML xenograft model. We found a relative increase in CLEC12A positive cells post Ara-C induction chemotherapy in AML xenograft models (Figure 1). This observation provided a solid rationale to target CLEC12A with chimeric antigen receptor T (CART) cells. We therefore developed a CLEC12A directed CAR construct using CD3z and 41BB costimulatory domains and generated CLEC12A CART cells by lentiviral transduction with this construct. To test the in vivo anti-leukemic activity of CLEC12A CARTs, we used primary human AML blasts xenografted into NSG-S mice (NOD-SCID-γc−/−, additionally transgenic for human stem cell factor, IL3 and GM-CSF). Treatment with CLEC12A CART (single dose, 1 × 105 total T cells via tail vein injection) resulted in modest activity against AML when employed as monotherapy. To investigate the potential role of CLEC12A CART cells in eradication of MRD and LSC, mice were treated first with chemotherapy (cytarabine 60 mg/kg intraperitoneal injection daily for 5 days) followed by a single dose (1 × 105 total T cells via tail vein injection) of either CLEC12A CARTs or control untransduced T cells (UTD). Treatment with CLEC12A CART cells resulted in eradication of leukemia and prolonged survival in these mice (overall survival at 200 days of 100% after CLEC12A CARTs compared to 20% after UTD, P = .01, Figure 2). In conclusion, our preclinical studies reveal that CLEC12A positive cells in leukemia are resistant to chemotherapy and can be successfully targeted with CART cells. CLEC12A CART cells can potentially be employed as a consolidation regimen after induction chemotherapy to eradicate LSC and MRD in AML.

Abstract The purpose of this study was to generate a panel of donor-derived primary cells, expand them ex-vivo in to sufficient numbers to utilize as targets for evaluating potential normal tissue toxicity of epidermal growth factor receptor mutation variant three (EGFRvIII)-specific chimeric antigen receptors (CAR) prior to use in clinical trials for patients with glioblastoma (GBM). Nine cell types were obtained, including different epithelial, endothelial, bone, smooth muscle, cardiac, neural, hematopoetic, stem cells, and keratinocytes. Cells were expanded with individual specialized media and protocols for between 8-12 passages. After expansion, primary cell identity was confirmed by morphology, ICC and IHC for characteristic markers. Levels of EGFR and EGFRvIII in each cell type were determined by qRT-PCR. To evaluate potential normal-cell toxicity, CAR T cells were co-cultured with each type of primary cell and function was evaluated in two ways: i) T cell activation was measured by staining and flow cytometry of CD3+ T cells stained intracellularly for CD107a, or GzmB, TNFalpha, IFNgamma, IL-2 cytokines. ii) Target cell lysis was evaluated by labeling primary cells with 51Cr prior to 4 hour co-culture with increasing numbers of CAR T cells, and measuring chromium-release. None of the primary cells showed expression of EGFRvIII, although several, in particular keratinocytes and renal epithelial, had high levels of EGFR. In functional assays, while the EGFR CAR T cells recognized and lysed EGFR expressing cell types, EGFRvIII CARs showed T cell activation and target lysis only of EGFRvIII expressing tumors. EGFRvIII CAR 2173 was selected for use in clinical trials at UPENN and UCSD, treating patients with GBM. To date, 6 patients have been infused with 2173 EGFRvIII CAR T cells, with no observed toxicity. All patients had detectable expansion of CAR T cells in vivo in blood, and one patient with subsequent tumor resection had detectable intra-tumoral CAR T cells. These CARs appear to be safe, persist in vivo and traffic into GBM tumor. An update on the clinical trial will be presented at the conference. Note:This abstract was not presented at the conference. Citation Format: Alexandria P. Cogdill, Alina Boesteanu, Chong Xu, Kathleen Haines, John Scholler, Joseph Fraietta, Yangbing Zhao, Xiaojun Liu, Jennifer Morrissette, Bruce Levine, Simon Lacey, Andreas Loew, Reshma Singh, Jennifer Brogdon, Donald M. O'Rourke, Marcela V. Maus, Carl H. June, Laura A. Johnson. Toxicity testing of EGFRvIII CAR-based immunotherapy of glioblastoma: From bench to bedside. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B139.

Chemo-refractory acute myeloid leukemia (AML) is associated with poor prognosis and treatment options are extremely limited. Most of these patients are ineligible for allogeneic stem cell transplantation. Chemo-refractory AML is thought to arise due to selection pressure of resistant clones from prior use of chemotherapy or in some cases pre-exist due to properties of the leukemic stem cells (LSC). CLEC12A (also known as CLL1) has previously been described as being selectively over expressed in LSCs. Successful modalities to target CLEC12A and eradicate the LSC would overcome chemo-refractoriness in AML and would represent a vertical advance in the field. In this study, we confirm that CLEC12A is heterogenously expressed on AML blasts and over-expressed on AML LSC. We also show that CLEC12A is overexpressed on bone marrows from patients with AML that fail to achieve a complete remission after induction chemotherapy, suggesting that it could be a marker for residual disease that is refractory to chemotherapy. We then separated AML blasts into CLEC12A positive or negative cells by magnetic sorting. CLEC12A positive blasts selected from AML patients were more resistant to chemotherapy compared to CLEC12A negative blasts (20% killing of CLEC12A positive AML cells versus 43% of CLEC12A negative AML cells when cultured with cytarabine 10 µg/ml, P=0.01). This finding was confirmed by using the AML MOLM14 cell line engineered to overexpress CLEC12A. CLEC12Ahigh MOLM14 cells were more resistant to chemotherapy compared to wild type MOLM14 cells (P=0.003). We then evaluated CLEC12A resistance to chemotherapy in a patient derived AML xenograft model. We found a relative increase in CLEC12A positive cells post Ara-C induction chemotherapy in AML xenograft models (Figure 1). The observation that CLEC12A positive cells are more resistant to chemotherapy provided a solid rationale to target CLEC12A with chimeric antigen receptor T (CART) cells. We therefore developed a second generation CLEC12A directed CAR construct using CD3z and 41BB costimulatory domains and generated CLEC12A CART cells by lentiviral transduction with this construct. Upon incubation with primary AML samples or AML cell lines, CLEC12A CART cells resulted in modest effector functions, due to the heterogeneity of CLEC12A expression on AML blasts. However when CLEC12A overexpressed MOLM14 cell line or CLEC12Apos selected leukemic cells were used as targets, CLEC12A-CART cells resulted in potent cytotoxicity, proliferation and cytokine production, indicating that CLEC12A-CART cells are more specific for LSC. To test the in vivo anti-leukemic activity of CLEC12A CARTs, we used primary human AML blasts xenografted into NSG-S mice (NOD-SCID-γc-/-, additionally transgenic for human stem cell factor, IL3 and GM-CSF). Treatment with CLEC12A CART (single dose, 1x105 total T cells via tail vein injection) resulted in modest activity against AML when employed as monotherapy. To investigate the potential role of CLEC12A CART cells in eradication of MRD and LSC, mice were treated first with chemotherapy (cytarabine 60 mg/kg intraperitoneal injection daily for 5 days) followed by a single dose (1x105 total T cells via tail vein injection) of either CLEC12A CARTs or control untransduced T cells (UTD). Treatment with CLEC12A CART cells resulted in eradication of leukemia and prolonged survival in these mice (overall survival at 200 days of 100% after CLEC12A CARTs compared to 20% after UTD, p=0.01, Figure 2). In conclusion, our preclinical studies reveal that CLEC12A positive cells in leukemia are resistant to chemotherapy and can be successfully targeted with CART cells. CLEC12A CART cells can potentially be employed as a consolidation regimen after induction chemotherapy to eradicate LSC and MRD in AML. Disclosures Kenderian:Novartis: Patents & Royalties, Research Funding. Ruella:novartis: Patents & Royalties: Novartis, Research Funding. Singh:Novartis: Employment. Richardson:Novartis: Employment, Patents & Royalties, Research Funding. June:Tmunity: Equity Ownership, Other: Founder, stockholder ; Immune Design: Consultancy, Equity Ownership; Novartis: Honoraria, Patents & Royalties: Immunology, Research Funding; University of Pennsylvania: Patents & Royalties; Celldex: Consultancy, Equity Ownership; Johnson & Johnson: Research Funding; Pfizer: Honoraria. Gill:Novartis: Patents & Royalties, Research Funding.

Chimeric antigen receptors (CARs) are synthetic molecules designed to redirect T cells to specific antigens. CAR-modified T cells can mediate long-term durable remissions in B cell malignancies, but expanding this platform to solid tumors requires the discovery of surface targets with limited expression in normal tissues. The variant III mutation of the epidermal growth factor receptor (EGFRvIII) results from an in-frame deletion of a portion of the extracellular domain, creating a neoepitope. We chose a vector backbone encoding a second-generation CAR based on efficacy of a murine scFv-based CAR in a xenograft model of glioblastoma. Next, we generated a panel of humanized scFvs and tested their specificity and function as soluble proteins and in the form of CAR-transduced T cells; a low-affinity scFv was selected on the basis of its specificity for EGFRvIII over wild-type EGFR. The lead candidate scFv was tested in vitro for its ability to direct CAR-transduced T cells to specifically lyse, proliferate, and secrete cytokines in response to antigen-bearing targets. We further evaluated the specificity of the lead CAR candidate in vitro against EGFR-expressing keratinocytes and in vivo in a model of mice grafted with normal human skin. EGFRvIII-directed CAR T cells were also able to control tumor growth in xenogeneic subcutaneous and orthotopic models of human EGFRvIII(+) glioblastoma. On the basis of these results, we have designed a phase 1 clinical study of CAR T cells transduced with humanized scFv directed to EGFRvIII in patients with either residual or recurrent glioblastoma (NCT02209376).

L'invention concerne des compositions et des methodes de traitement de maladies associees a l'expression de CLL-1. L'invention concerne egalement un recepteur d'antigenes chimeriques (CAR) specifique de la CLL-1, des vecteurs codant ledit recepteur et des lymphocytes de recombinaison comprenant le CAR CLL-1. L'invention concerne egalement des methodes d'administration d'un lymphocyte genetiquement modifie exprimant un CAR qui presente un domaine de liaison a CLL-1.

Although there have been compelling advances in the cancer immunotherapy space recently in the form of chimeric antigen receptor (CAR) modified T-cells and checkpoint inhibitors, advanced tools to explore the therapeutic mechanisms of their combination are not adequately developed or widely available. To address this growing need, we developed a robust quantitative fluorescent immunohistochemistry platform using multiplex AQUA (Automated Quantitative Analysis) technology to evaluate checkpoint inhibitor expression, enumerate CAR T cells and determine the interaction between tumor cells and immune cells via novel co-localization algorithms. We explored utility of this method both in preclinical- and clinical model systems. In an immunodeficient mouse model of B-cell lymphoma, we evaluated homing of CAR T cells to malignant B-cells in primary lymphoid organs. We determined the phenotype and functional status of the CAR T cells via multiplex analyses of CD4, CD8, PD1 and FOXP3 expression. Additionally, to enable combination immunotherapies in Diffuse Large B-Cell Lymphoma (DLBCL) setting, we explored prevalence of adaptive immune resistance mechanisms in the form of PD1 and PD-L1 expression in immune- and tumor cell compartments via landmarks created by cytoplasmic and nuclear stains in both primary and secondary biopsies from DLBCL patients (n = 63). To support patient selection for CAR T trials, we quantified expression and prevalence of relevant tumor antigens that could not be scored reproducibly by traditional methods to yield objective cut points. We anticipate utilization of these quantitative multiplexed IHC methods for optimal selection of patients into upcoming novel combination immunotherapy trials Disclosures Tran:Genoptix: Employment. Scott:Genoptix: Employment. Lee:Genoptix: Employment. Singh:Novartis: Employment. Cogan:Novartis: Employment. Bordeaux:Genoptix: Employment. Jennifer:Genoptix: Employment. Lameh:Genoptix: Employment. Tribouley:Novartis: Employment. Kassim:Novartis: Employment. Tangri:Genoptix Inc., a Novartis company: Employment. Dakappagari:Genoptix Inc., a Novartis company: Employment.

Chimeric antigen receptors (CARs) are synthetic molecules designed to re-direct T cells to specific antigens; CAR-modified T cells can mediate long-term durable remissions in B cell malignancies, but expanding this platform to solid tumors requires the discovery of novel surface targets with limited expression in normal tissues. The variant III mutation of the epidermal growth factor receptor (EGFR variant III) results from an in-frame deletion of a portion of the extracellular domain. In glioblastoma, the EGFRvIII mutation is oncogenic, portends a poor prognosis, and is thought to be enriched in glioblastoma stem cells. However, because the neoepitope of EGFR variant III is based on a small peptide sequence, an antibody or single-chain variable fragment (scFv) directed to this epitope must be rigorously tested to confirm lack of cross-reactivity to the ubiquitously expressed wild-type EGFR. We chose a vector backbone encoding a second generation CAR based on efficacy of a murine scFv-based CAR in a xenograft model of glioblastoma. Next, we generated a panel of humanized scFv’s and tested their specificity and function as soluble proteins and in the form of CAR-transduced T cells; a low affinity scFv was chosen based on its specificity for EGFR variant III over wild type EGFR. The lead candidate scFv was tested in vitro for its ability to direct CAR-transduced T cells to specifically lyse, proliferate, and secrete cytokines in response to antigen-bearing targets. We further evaluated the specificity of the lead candidate CAR in vitro against EGFR expressing keratinocytes and in vivo in immunodeficient mice grafted with normal human skin; a cetuximab-based CAR served as a positive control. EGFRvIII-directed CAR-T cells were also able to control tumor growth in xenogeneic subcutaneous and orthotopic models of human EGFR variant III+ glioblastoma. We have designed a phase I clinical study of CAR T cells transduced with humanized scFv directed to EGFR variant III in patients with either residual or recurrent glioblastoma (NCT02209376).

Background: One of the significant tumor immune escape mechanisms and substantial barrier for successful immunotherapy is tumor-mediated inhibition of immune response through cell-to-cell or receptor/ligand interactions. Programmed death receptor-1 (PD-1) interaction with its ligands, PD-L1 and PD-L2, is one of the important strategies that many tumors employ to escape immune surveillance. Upon PD-Ls binding to PD-1, T cell receptor (TCR) signaling is dampened, causing inhibition of proliferation, decreased cytokine production, anergy and/or apoptosis. Thus PD-Ls expression by tumor cells serves as a protective mechanism, leading to suppression of tumor-infiltrating lymphocytes in the tumor microenvironment. Lm-LLO immunotherapies have been shown to be therapeutically effective due to their ability to induce potent antigen-specific immune responses. However, it has been demonstrated that infection with Lm leads to up-regulation of PD-L1 on mouse immune cells that can inhibit effector T cells through PD-1/PD-L1 pathway.Methods: Therapeutic and immune efficacy of Listeria-based vaccine (Lm-LLO-E7) in combination with anti-PD-1 antibody was tested in E7 antigen expressing TC-1 mouse tumor model. Tumor growth, survival, as well as peripheral and tumor-infiltrating immune cell profiles after immunotherapy were assessed.Results: Here we demonstrate that the combination of an Lm-LLO immunotherapy with anti-PD-1 antibody that blocks PD-1/PD-L1 interaction, significantly improves immune and therapeutic efficacy of treatment in TC-1 mouse tumor model. Importantly, we show that in addition to significant reduction of regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSC) in both spleen and tumor microenvironment that are mediated solely by the Lm-LLO immunotherapy, the addition of anti-PD-1 antibody to the treatment results in significant increase of antigen-specific immune responses in periphery and CD8 T cell infiltration into the tumor. As a result, this combinational treatment leads to significant inhibition of tumor growth and prolonged survival/complete regression of tumors in treated animals. We also demonstrate that in vitro infection with Lm results in significant upregulation of surface PD-L1 expression on human monocyte-derived dendritic cells suggesting the translational capacity of this finding.Conclusions: Our findings demonstrate that combination of Lm-LLO-based vaccine with blocking of PD-1/PD-L1 interaction is a feasible approach with clinical translation potential that can lead to overall enhancement of the efficacy of anti-tumor immunotherapy.

Abstract Bioengineered Listeria monocytogenes (Lm), which secrete antigens fused to a fragment of listeriolysin O (LLO) have been shown to be effective cancer immunotherapeutics in several mouse models of cancer, and are currently being evaluated in Phase 2 clinical trials for HPV-associated dysplasia and malignancies. Treatment with Lm-LLO immunotherapies results in a marked increase in tumor infiltrating lymphocytes, in particular CD8+T cells. The antigen-specific CD8+T cells have been observed to kill tumor cells in vitro, showing the functionality of the Lm-stimulated T cells. Lm-LLO immunotherapies also have an impact on suppressor cells in the tumor microenvironment. In various tumor models, treatment results in a decrease in the ratio of regulatory T cells (Tregs) to effector T cells in the tumors. Here, we report a corresponding decrease in the ratio, and number, of monocyte-derived suppressor cells (MDSCs) after Lm-LLO immunotherapy. These change are only seen in the tumor microenvironment. Further, both Tregs and MDSCs isolated from the tumor have a decreased ability to suppress the division of T cells after Lm-LLO immunotherapy. However, there is no change in functional ability of splenic Tregs or MDSCs. Thus, the efficacy of Lm-based immunotherapies on tumors is likely due to a combined increase in antigen-specific effector cells and a tumor specific decrease in the numbers and function of suppressor cells in the tumor microenvironment.

Radiation therapy (RT) is an integral part of prostate cancer treatment across all stages and risk groups. Immunotherapy using a live, attenuated, Listeria monocytogenes-based vaccines have been shown previously to be highly efficient in stimulating anti-tumor responses to impact on the growth of established tumors in different tumor models. Here, we evaluated the combination of RT and immunotherapy using Listeria monocytogenes-based vaccine (ADXS31-142) in a mouse model of prostate cancer. Mice bearing PSA-expressing TPSA23 tumor were divided to 5 groups receiving no treatment, ADXS31-142, RT (10 Gy), control Listeria vector and combination of ADXS31-142 and RT. Tumor growth curve was generated by measuring the tumor volume biweekly. Tumor tissue, spleen, and sera were harvested from each group for IFN-γ ELISpot, intracellular cytokine assay, tetramer analysis, and immunofluorescence staining. There was a significant tumor growth delay in mice that received combined ADXS31-142 and RT treatment as compared with mice of other cohorts and this combined treatment causes complete regression of their established tumors in 60 % of the mice. ELISpot and immunohistochemistry of CD8+ cytotoxic T Lymphocytes (CTL) showed a significant increase in IFN-γ production in mice with combined treatment. Tetramer analysis showed a fourfold and a greater than 16-fold increase in PSA-specific CTLs in animals receiving ADXS31-142 alone and combination treatment, respectively. A similar increase in infiltration of CTLs was observed in the tumor tissues. Combination therapy with RT and Listeria PSA vaccine causes significant tumor regression by augmenting PSA-specific immune response and it could serve as a potential treatment regimen for prostate cancer.