Antigen-specific Killing Research Articles

Preclinical evaluation of antigen-sensitive B7-H3-targeting nanobody-based CAR-T cells in glioblastoma cautions for on-target, off-tumor toxicity

BackgroundGlioblastoma is the most common lethal primary brain tumor, urging evaluation of new treatment options. Chimeric antigen receptor (CAR)-T cells targeting B7 homolog 3 (B7-H3) are promising because of the...

EphA3-targeted chimeric antigen receptor T cells are effective in glioma and generate curative memory T cell responses

BackgroundHigh-grade gliomas including glioblastoma (GBM) and diffuse midline gliomas (DMG) represent the most lethal and aggressive brain cancers where current treatment modalities offer limited efficacy. Chimeric antigen receptor (CAR) T...

Abstract PO4-06-08: ZP4 AS A NOVEL TARGET FOR CAR T CELL THERAPY IN TRIPLE NEGATIVE BREAST CANCER

Abstract Triple negative breast cancer (TNBC) has the worst prognosis of BC subtypes, largely due to lack of approved targeted therapies. Chimeric antigen receptor (CAR) T cells have demonstrated great success in certain hematological malignancies; however, in the treatment of solid cancers, CAR T cells are faced with a variety of obstacles that limit their efficacy, including on-target/off-tumor toxicity. To minimize these toxicities, the ideal CAR T cell target must be overexpressed by the tumor and absent from vital organs. Cancer/germline (CG) antigens satisfy this need, as their expression is restricted to male or female germ cells. Using a bioinformatic pipeline to identify novel CG antigens expressed in TNBC and other solid cancers, we have identified zona pellucida glycoprotein 4 (ZP4) as a candidate CG antigen target for CAR T cell therapy. This protein is a component of the human zona pellucida matrix, an extracellular structure that surrounds the oocyte and functions in folliculogenesis, species-specific fertilization, and early development. We have identified ZP4 expression in approximately 10% of TNBC cases from available RNAseq and proteomic databases and have confirmed ZP4 expression in several TNBC PDX models. The overall purpose of this study is to redirect T cells against ZP4 by engineering and validating a second generation ZP4-specific CAR. We have generated a library of monoclonal antibody (mAb) candidates against the extracellular portion of human ZP4. Antibody clones were screened, and their specificity validated via ELISA and flow cytometry, and the three strongest binders (z108, z128, and z164) were selected for further investigation. By IHC, we confirmed that the ZP4 mAb clones stained the area surrounding normal oocytes and did not show binding to any of the 23 normal tissues screened. The variable regions of the antibody heavy and light chains were sequenced using 5’RACE and used to assemble second generation CAR constructs composed of the variable heavy and light chain fragments separated by a linker, a CH2/CH3 hinge domain, a CD28 transmembrane domain, a CD28 co-stimulatory domain, and the CD3z signaling domain. Activated T cells transduced with retroviral supernatant express the ZP4 CAR constructs at high levels. While all ZP4 CAR T cells demonstrate antigen-specific cytotoxic killing of ZP4+ target tumor cells in short-term in vitro assays, z128 ZP4 CAR T cells demonstrate superior persistence and efficacy in long-term repeat tumor challenge in vitro assays and orthotopic in vivo mouse models. In summary, ZP4 is a promising target for TNBC and we have successfully engineered ZP4 specific CAR T cells. ZP4 CAR T cells effectively target and kill ZP4+ cells in in vitro cytotoxicity assays but perform differently in repeat tumor challenge assays and in vivo. Future studies will elucidate the precise differences between our three candidate CAR constructs and further test the effector function, trafficking, proliferation, and persistence of z128 ZP4 CAR T cells in vivo using ZP4+ PDX models. This work has exciting potential to bring a novel CAR T cell therapy to patients with TNBC, without concerns for on-target off-tumor toxicity. Citation Format: Lauren Somes, Jonathan Lei, Paul Shafer, Xinpei Yi, Diego Chamorro, Emily Madaras, Michael Lewis, Bing Zhang, Valentina Hoyos. ZP4 AS A NOVEL TARGET FOR CAR T CELL THERAPY IN TRIPLE NEGATIVE BREAST CANCER [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-06-08.

Chimeric Antigen Receptor T-Cell Recruitment and Killing can be Evaluated on an Organ-Chip model system

Abstract Objective. Chimeric antigen (CAR) T-cell therapies for solid tumors are challenging to develop due to the lack of human relevant models that adequately capture the mechanisms of CAR T-cell recruitment-a critical yet often overlooked rate-limiting step. The current study aimed to develop a novel system for investigating both the recruitment and killing capacity of CAR T cells in Organ-Chips. Methods. Chip-S1™ Stretchable Chips (Emulate) were seeded with a human HER2+ non-small cell lung cancer cell line (NSCLC) in the top channel and lung microvascular endothelial cells in the vascular (bottom) channel to create a tumor-vascular interface. Both channels were primed with an NSCLC-specific mix of chemokines and cytokines. HER2-specific CAR T cells were perfused through the vascular channel. Total CAR T-cell recruitment into the top channel and CAR T-mediated killing were measured over 48 hours. The IL-2 cytokine was also co-administered with CAR T cells as immunotherapy. Results. HER2 CAR T cells demonstrated significant antigen-specific killing when recruited to the top channel as measured by caspase activity and cytokine release compared to the control. Furthermore, IL-2 co-therapy increased CAR T-cell recruitment and antigen-specific killing compared to the control group. Conclusion. These findings suggest that human-centric Organ-Chips can evaluate CAR T-cell therapies for solid tumors by integrating the critical rate-limiting steps of CAR T recruitment and killing.

Abstract LB080: iOTarg screening platform reveals novel mechanisms of colorectal cancer evasion from antigen-specific tumor cell killing by T cells

Abstract While immune checkpoint therapies have revolutionized cancer treatment, their efficacy remains limited in colorectal cancer (CRC) and other malignancies. Tumors employ diverse strategies to evade immune-mediated destruction, hindering the success of immunotherapies. We introduce iOTarg, a robust high-throughput screening platform designed to uncover resistance pathways against T cell-mediated tumor killing within the tumor microenvironment. Focusing on CRC, we utilized iOTarg to dissect evasion mechanisms against antigen-specific T cell (TC) killing. In a representative CRC cell line co-culture system (SW480, HCT116 or COLO-678) with various TC sources, we gained key insights of tumor resistance towards killing. Survivin-specific TCs induce strong tumor lysis while tumor-infiltrating lymphocyte 412 (TIL412) represent a weaker basal killing representative of the situation in the tumor. Knockout of β₂-microglobulin abrogated TC-mediated killing, while c-FLIP knockout significantly enhanced tumor lysis. Intriguingly, PD-L1 blockade had no impact on TC activation or killing, underlining its lack of efficacy in CRC. Screening over 6000 druggable genes revealed several critical candidates, including anti-apoptotic BIRC family members (BIRC2, 3), apoptosis regulators (Bcl-xL, XIAP), TNF signaling regulators (TRAF2, MAP3K7), and genes recently described as sensitization mediators (B3GNT3, CHMP4B). Caspase-8 knockout prevented TC-mediated killing of CRC cells, confirming its crucial role in immune-mediated tumor cell clearance. Further validation in secondary screenings reinforced a subset of genes as strong regulators of tumor cell killing, uncovering an array of CRC resistance mechanisms. Our findings present a pioneering platform delineating resistance mechanisms against T cell-mediated colorectal tumor killing. We identify established and novel targets, offering prospects for novel therapeutics and expanding immune oncology treatment options. This platform holds promise for developing first-in-class therapies targeting the tumor microenvironment, potentially transforming CRC treatment paradigms. Citation Format: Tillmann Michels, Valentina Volpin, Carmen Amerhauser, Claudia Tschulik, Leonie Majunke, Aleksandra Weglarz, Kilian Baritz, Kritika Sudan, Szilvia Bak-Kiss, Alina Huth, Carolin Strobl, Adriana Turqueti-Neves, Nisit Khandelwal. iOTarg screening platform reveals novel mechanisms of colorectal cancer evasion from antigen-specific tumor cell killing by T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB080.

Abstract 2604: Evaluating the potency of antibody-drug conjugate (ADC) free-drugs on T cells

Abstract Antibody-drug conjugates (ADCs) combine the targeting specificity of antibodies with powerful cytotoxic payloads to direct antigen-specific tumor cell killing. Multiple ADCs have shown single-agent clinical activity against solid and hematological cancers and are currently being evaluated in combination with immune checkpoint inhibitors (CPIs). Therapeutic benefit from CPIs relies on the presence and quality of responding antitumor T cells, both in the tumor and from new T cell priming and expansion outside the tumor. Select cytotoxic ADC payloads, like monomethyl auristatin E (MMAE), have the potential to amplify T cell responses through immunogenic cell death (ICD) and, as such, may be optimal combination partners with CPIs. However, ADC payloads released in the tumor (bystander drug) or released systemically also have the potential to negatively impact T cell viability, proliferation, and priming. The compatibility of different ADC payload chemotypes (Auristatins, camptothecins (CPTs), Pyrrolobenzodiazepine (PBDs), Tubulysins) with CPIs may depend on both the direct and indirect effects of payloads and their associated free-drugs on immune cells. Here, we determined the relative potencies of ADC payload free-drugs MMAE and DXd on activated human and murine T cells in vitro and in a model of xeno-graft versus host disease (xeno-GVHD) to evaluate the impact of ADC bystander effects on human immune cell expansion and function in vivo. In vitro, ADC payloads showed a range of potencies on activated T cells, with IC50 values skewing lower for CD4 compared to CD8 T cells. For each payload, murine T cells were significantly less sensitive than human T cells, which may have implications for modeling combinations of ADCs and CPIs. Mouse CD8 T cells were ~10-fold less sensitive to MMAE and 20-25-fold less sensitive to clinical CPT payloads compared to human T cells. In an in vivo model of human immune cell activation, xeno-GVHD, bystander effects from a non-targeted MMAE-ADC did not impair the expansion of human immune cells, however, a non-targeted DXd-ADC reduced CD4 T cells and robustly reduced populations of non-T cells in spleens. Consistent with reduced immune cell expansion, the DXd-ADC significantly slowed the xeno-GVHD disease course compared to the MMAE-ADC treated and control groups. These data suggest that the most commonly used ADC payload classes, MMAE and DXd, may have different direct effects on proliferating human immune cells as bystander free-drugs, which may have clinical relevance for combinations of ADCs with CPIs. Continued research exploring the balance between ADC potency on tumor cells, direct and indirect effects of payloads on immune cells, and dose timing and sequencing could help maximize the potential of ADCs in combination with immunotherapies. Citation Format: Reice D. James, Michelle L. Ulrich, J Hartsuyker, Alyson J. Smith, Ryan A. Heiser. Evaluating the potency of antibody-drug conjugate (ADC) free-drugs on T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2604.

Abstract 3132: A novel dual drug antibody-drug conjugate targeting hTrop2 has synergetic anti-tumor activity in solid tumor models

Abstract Antibody-drug conjugates (ADCs) are emerging therapeutic agents for targeted cancer treatment with remarkable clinical success. However, tumor heterogeneity and microenvironment complexity are still the major factors contributing to drug resistance, recurrence, and metastasis, which cannot be resolved with a mono therapy strategy. We’ve developed a novel dual drug ADC (BiADC), BR113, by conjugating an anti-hTrop2 antibody with a drug linker of a Topoisomerase I inhibitor payload, and another drug linker of an immune stimulator. Our studies show that the homogeneous ADC containing two distinct payloads is a new promising drug class, with two different anti-tumor MOAs, synergistic antigen-specific cell killing potency, desirable pharmacokinetic profiles, and minimal toxicity at therapeutic doses. In the cancer cells and human PBMC co-culture assay, BR113 exerts significantly more potent killing on cancer cells than two individual single-drug ADCs and the combination of two single-drug ADCs, which suggested a synergy on anti-tumor effects of this dual-drug ADC. In the xenograft mouse model studies, BR113 exhibits greater treatment effect and survival benefit than the combo of two single-drug ADCs at various doses. This robust superior anti-tumor activity is further confirmed in a hTrop2-MC38 syngeneic model with a prolonged anti-tumor protection against the tumor re-challenge. Finally, the novel BiADC, BR113, is well tolerated in hTop2 humanized mice after repeated administration. Our findings highlight the therapeutic potential of the BiADC format for treating refractory advanced solid tumors. The outstanding anti-tumor activity across various CDX tumor models and its favorable safety profile in mice support further evaluation of the innovative BiADC, BR113. Citation Format: Jie Zhu, Xiaobei Zhao, Eileen Li, Hong Xu, Lei Nie, Gang Chen, Haibing Wang. A novel dual drug antibody-drug conjugate targeting hTrop2 has synergetic anti-tumor activity in solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3132.

Abstract 6766: Assessing the impact of immunotherapies and cell therapies in 3D heterospheroid models mimicking tumor microenvironments

Abstract Immunotherapies and cell therapies show substantial potential in the treatment of cancer. However, their efficacy within the complex microenvironment of solid tumors remains a critical area of investigation. In this study, we employ physiologically relevant 3D multicellular heterospheroid models to quantitatively assess the impact of these therapies on immune and tumor cells residing in tumor-like microenvironments. The spheroids are composed of cancer cell lines, fibroblasts and various primary immune cell types matched to the specific target of immunotherapy. We have previously reported that interactions between cancer cells and fibroblasts promote a tumor-like environment, recruiting and polarizing monocytes into M2 macrophages. Treatment of spheroids with immunomodulating compounds successfully reprogrammed the macrophages into M1-like macrophages with increased pro-inflammatory cytokine secretion. To mimic tumor-specific T cell responses observed in cancer patients, we here educated T cells to recognize target cell antigens through a 14-day co-culture of PBMCs and PANC-1 tumor cells. Subsequent re-challenge with PANC-1 heterospheroids revealed 70% specific killing by educated T cells, whereas T cells educated with a breast cancer cell line did not exhibit this targeted cytotoxicity. FACS analysis demonstrated increased expression of activation markers and immune checkpoint molecules such as PD-1, LAG-3 and TIGIT on educated T cells. Furthermore, we observed infiltration of educated CD4+ and CD8+ T cells into heterospheroids by immunohistochemistry, indicating the replication of a tumor-specific response within solid tumors. We are currently investigating the enhancement of educated T cell killing using various immune checkpoint inhibitors including antibodies targeting PD-1, TIGIT and LAG-3. Another means of eliciting tumor-specific responses is by employing CAR T cells. Antigen-specific CAR-T cells or untransduced CAR-T cells derived from the same donor were added to HT-29 and HCT-116 heterospheroids at various target-to-effector ratios. By using cancer cells genetically engineered to express a luciferase enzyme, we assessed the specific killing of cancer cells within the heterospheroids. Analysis showed a clear dose-dependent increase in luminescence, indicating greater antigen-specific CAR-T cell killing potential (60-80% specific lysis) compared to the non-specific killing observed with untransduced CAR-T cells (<5% specific lysis). Additionally, preliminary data demonstrate the killing of heterospheroids by γδ T cells and that this killing is enhanced by immune checkpoint inhibitors. In conclusion, we have developed 3D heterospheroids from various cancer types that faithfully mimic tumor-like microenvironments, enabling us to evaluate the effects of immunotherapies and cell therapies in physiologically relevant models. Citation Format: Natasha Helleberg Madsen, Boye Schnack Nielsen, Kim Holmstrøm, Gitte Olofsson, Per thor Straten, Søren Skov, Carlos Rodriguez-Pardo, Maria Ormhøj, Jesper Larsen, Monika Gad. Assessing the impact of immunotherapies and cell therapies in 3D heterospheroid models mimicking tumor microenvironments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6766.

Abstract 3849: Frontline ibrutinib-based therapy enhances CART cell functions in patients with CLL: Analysis of the phase 3 randomized clinical trial ECOG-ACRIN E1912

Abstract Introduction: Despite the remarkable activity of CD19-directed chimeric antigen receptor T cell therapy (CART19), durable remissions remain low, especially in chronic lymphocytic leukemia (CLL). Ibrutinib is an oral irreversible inhibitor of Bruton’s tyrosine kinase and is a first line therapy for CLL. Preclinical and early clinical data indicate that ibrutinib plus CART19 may be synergistic through inhibition of IL2-inducible T cell kinase. To systematically study the effects of prior ibrutinib treatment on subsequent CART functions, we utilized blood samples from the pivotal clinical trial E1912 (NCT02048813). E1912 was a phase 3 randomized trial comparing treatment with ibrutinib/rituximab (IR) to fludarabine/cyclophosphamide/rituximab (FCR) in previously untreated patients with CLL, which led to the FDA approval of ibrutinib as a first-line therapy in CLL. Methods: We evaluated the ex vivo expansion and effector functions of T cells and CART19 generated from patients (n=12) with CLL progression following treatment with IR or FCR. We generated CART19 from longitudinal samples obtained at baseline (pretreatment), 6 months post-treatment, 12 months post-treatment, and disease progression. Isolated T cells were lentivirally transduced to express CD28- or 41BB-costimulated CAR19. To assess antigen specific killing and proliferation, untransduced T cells or CART19 were co-cultured at a 1:1 ratio with the CD19+ cell line, JeKo-1, as a surrogate for CLL cells. Results: Ex vivo T cell expansion increased from an average of 1.5-fold at baseline to 6.7-fold at 6 months, 11.6-fold at 12 months, and 16.9-fold at progression, following ibrutinib-based therapy (p = 0.02, 0.04, and 0.04, respectively). Improved T cell expansion was independent of disease burden (p = 0.89, 0.73, and 0.54 for expansion vs B cell count at 6 months, 12 months, and progression). T cell expansion significantly worsened following treatment with FCR-based therapy compared to ibrutinib-based therapy (0.6- vs 11.6-fold at 12 months and 0.9- vs 16.9-fold at progression; p = 0.031 and 0.039, respectively). Starting at 6 months post-IR, CART19 demonstrated improved antitumor activity and antigen-specific proliferation against JeKo-1. There was no significant difference in the expansion of 41BB- vs CD28-costimulated CART19 following ibrutinib treatment. However, 41BB-CART19 showed enhanced antigen-specific proliferation upon stimulation with JeKo-1 (p = 0.008, 0.02, and 0.02 at 6 months, 12 months, and progression). Conclusion: Our results indicate significant improvement in T cell expansion and CART19 cell functions in patients with CLL following frontline ibrutinib-based therapy, and worsening T cell functions after FCR treatment. Improvement in T cell functions is independent of malignant B cell eradication and is more significant in 41BB-costimulated CART19. Citation Format: Truc Ngoc Huynh, Victoria Wang, Tait Shanafelt, Elizabeth L. Siegler, Carli M. Stewart, Kun Yun, Long K. Mai, Olivia Sirpilla, James H. Girsch, Claudia Manriquez-Roman, Jennifer M. Feigin, Makena Rodriguez, Brooke L. Kimball, Hong Xia, Reona L. Sakemura, Ismail Can, Omar L. Gutierrez-Ruiz, Ekene J. Ogbodo, Erin E. Tapper, Lionel A. Fonkoua, Mehrdad T. Hefazi, Michael W. Ruff, Sameer Parikh, Neil E. Kay, Saad J. Kenderian. Frontline ibrutinib-based therapy enhances CART cell functions in patients with CLL: Analysis of the phase 3 randomized clinical trial ECOG-ACRIN E1912 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3849.

Abstract 3975: A therapeutic screening platform for assessing antigen-specific T cell-mediated tumor killing in vitro

Abstract Many cancers remain resistant to conventional therapies, consequently there has been an exponential rise in the number of therapeutics harnessing the power of the immune system in an oncology setting, with several remarkable examples of success. High frequencies of infiltrating tumor-specific T cells have been linked to improved patient outcomes, which highlights the importance of uncovering how therapeutics can enhance their function. To explore this functionality in a preclinical setting it is critical to have physiologically relevant models. Here, we demonstrate that common issues, such as low precursor frequencies and restricted HLA-types can be overcome via access to HLA-typed samples and use of expansion platforms which attain high numbers of antigen-specific T cells. Furthermore, we show how these systems enable vaccine immunogenicity screening and assessment of therapeutic efficacy. Healthy blood donations were screened for HLA type and antigen-specific T cells were expanded by either co-culture with peptide-pulsed dendritic cells or polyclonal stimulation following multimer enrichment and FACS sorting. Following expansion, the large number of antigen-specific T cells generated enabled the T cells to be assessed via phenotyping, cytokine secretion, or functional killing assays in a 2D or 3D tumor setting. Tumor targets with either 1) endogenous antigen expression, 2) antigen introduced via lentiviral overexpression or 3) peptide loading of MHC class I were utilized. Validated readouts for measuring antigen-specific killing included flow cytometry and time-lapse imaging (IncuCyte), alongside quantification of antigen-specific IFNɣ responses by ELISpot. These pre-clinical platforms represent a suite of physiologically relevant T cell assays which can be used to perform candidate selection in tumor associated antigen/neoantigen vaccine drug development programs, pharmacological inhibition of checkpoint pathways, or co-stimulatory agonist discovery. In combinatorial approaches with radio- or chemotherapy, the development of novel immunotherapies offers hope to many patients with treatment-resistant cancers. Citation Format: Elsenoor Klaver, Henry Leonard, Elizabeth Lieverse, Oliver Brand, Olivier Reelfs, Christopher Kirkham, Lauren Schewitz-Bowers, Louise Brackenbury. A therapeutic screening platform for assessing antigen-specific T cell-mediated tumor killing in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3975.

Abstract 6714: AI-guided tailor-made anti-TROP2 T-cell engagers for T-cell mediated cancer immunotherapy with enhanced therapeutic index

Abstract Bispecific T-cell engagers (TCEs) have shown significant therapeutic advances in the treatment of hematologic cancers. However, the clinical efficacy of TCEs in treating solid tumors remains to be demonstrated. Accumulating evidence suggests novel TCE modalities that simultaneously engage both CD3 (signal 1) and CD28 (signal 2) co-stimulatory signals may offer potential advantage to enhance clinical efficacy of TCEs with improved therapeutic index. To explore the full potential of TCEs as a powerful approach of immunotherapy for solid tumors, we developed an integrated AI-guided TCE platform to streamline the discovery, optimization and high-throughput function screening and characterization of TCE molecules. Here we report the construction and characterization of a novel panel of TROP2-targeting TCEs by leveraging our AI-guided optimization technology, plus a high-throughput in vitro screening platform. These tailor-made TCE molecules exhibit favorable developability and functional properties. Our data show that a novel TROP2 × CD3 x CD28 trispecific TCE that contains a CD3-targeting arm in concomitant with a CD28-targeting arm can induce potent T-cell co-stimulation and promising synergistic T cell-mediated tumor cell killing in vitro, compared to its counterparts with a single CD3-targeting arm. We further generate a trivalent TROP2 x CD3 bispecific TCE constructed as an asymmetric ‘2+1’ format with bivalent binding to TROP2 but a monovalent CD3-targeting arm. This molecule stimulates very low levels of cytokine release, but drives robust antigen-specific killing in in vitro assessment. Anti-tumor activity of the various TROP2 x CD3 TCEs is currently being investigated in multiple tumor xenograft mouse models. Citation Format: Chuan Chen, Liang Tian, Chenpeng Su, Dandan Liu, Xiaoqian Chen, Yifei Zhou, Suze Jiang, Guifang Wang, Jiyuan Tian, Yuan Yuan, Bing Yang, Jian Peng. AI-guided tailor-made anti-TROP2 T-cell engagers for T-cell mediated cancer immunotherapy with enhanced therapeutic index [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6714.

Sokotrasterol Sulfate Suppresses IFN-γ-Induced PD-L1 Expression by Inhibiting JAK Activity.

PD-1/PD-L1 monoclonal antibodies exhibit promising therapeutic effectiveness in multiple cancers. However, developing a simple and efficient non-antibody treatment strategy using the PD-1/PD-L1 signaling pathway still remains challenging. In this study, we developed a flow cytometry assay to screen bioactive compounds with PD-L1 inhibitory activity. A total of 409 marine natural products were screened, and sokotrasterol sulfate (SKS) was found to efficiently suppress the IFN-γ-induced PD-L1 expression. SKS sensitizes the tumor cells to antigen-specific T-cell killing in the T cell-tumor cell coculture system. Mechanistically, SKS directly targeted Janus kinase (JAK) to inhibit the downstream activation of signal transducer and activator of transcription (STAT) and the subsequent transcription of PDL1. Our findings highlight the immunological role of SKS that may act as a basis for a potential immunotherapeutic agent.

Immunomodulatory effects and improved outcomes with cisplatin- versus carboplatin-based chemotherapy plus atezolizumab in urothelial cancer

In metastatic urothelial cancer (mUC), cisplatin versus carboplatin leads to durable disease control in a subset of patients. The IMvigor130 trial reveals more favorable effects with atezolizumab combined with gemcitabine and cisplatin (GemCis) versus gemcitabine and carboplatin (GemCarbo). This study investigates the immunomodulatory effects of cisplatin as a potential explanation for these observations. Our findings indicate that improved outcomes with GemCis versus GemCarbo are primarily observed in patients with pretreatment tumors exhibiting features of restrained adaptive immunity. In addition, GemCis versus GemCarbo± atezolizumab induces transcriptional changes in circulating immune cells, including upregulation of antigen presentation and Tcell activation programs. Invitro experiments demonstrate that cisplatin, compared with carboplatin, exerts direct immunomodulatory effects on cancer cells, promoting dendritic cell activation and antigen-specific Tcell killing. These results underscore the key role of immune modulation in cisplatin's efficacy in mUC and highlight the importance of specific chemotherapy backbones in immunotherapy combination regimens.

Nanobody-based trispecific T cell engager (Nb-TriTE) enhances therapeutic efficacy by overcoming tumor-mediated immunosuppression

BackgroundT cell engagers (TCEs) have been established as an emerging modality for hematologic malignancies, but solid tumors remain refractory. However, the upregulation of programmed cell death 1 (PD-1) is correlated with T cell dysfunction that confer tumor-mediated immunosuppression. Developing a novel nanobody-based trispecific T cell engager (Nb-TriTE) would be a potential strategy to improve therapeutic efficacy.MethodsGiven the therapeutic potential of nanobodies (Nbs), we first screened Nb targeting fibroblast activation protein (FAP) and successfully generated a Nb-based bispecific T cell engager (Nb-BiTE) targeting FAP. Then, we developed a Nb-TriTE by fusing an anti-PD-1 Nb to the Nb-BiTE. The biological activity and antitumor efficacy of the Nb-TriTE were evaluated in vitro and in both cell line-derived and patient-derived xenograft mouse models.ResultsWe had for the first time successfully selected a FAP Nb for the generation of novel Nb-BiTE and Nb-TriTE, which showed good binding ability to their targets. Nb-TriTE not only induced robust tumor antigen-specific killing, potent T cell activation and enhanced T cell function in vitro, but also suppressed tumor growth, improved survival and mediated more T cell infiltration than Nb-BiTE in mouse models of different solid tumors without toxicity.ConclusionsThis novel Nb-TriTE provides a promising and universal platform to overcome tumor-mediated immunosuppression and improve patient outcomes in the future.

Ex-vivo CS1-OKT3 dual specific bivalent antibody-armed effector T cells mediate cellular immunity against multiple myeloma

Bispecific T cell engaging antibodies (bsAbs) have emerged as novel and powerful therapeutic agents for redirecting T cells towards antigen-specific tumor killing. The cell surface glycoprotein and SLAM family member, CS1, exhibits stable and high-level expression on malignant plasma cells including multiple myeloma, which is indicative of an ideal target for bsAb therapy. Here, we developed a CS1 bsAb (CS1-dbBiTE) using Click chemistry to conjugate intact anti-CS1 antibody (Elotuzumab) and anti-huOKT3 antibody at their respective hinge regions. Using a cellular therapy approach, human T cells were armed ex-vivo with CS1-dbBiTE prior to examining effector activity. Our data indicates that arming T cells with CS1-dbBiTE induced T cell activation and expansion and subsequent cytotoxic activity against CS1-bearing MM tumors, demonstrated by significant CD107a expression as well as inflammatory cytokine secretion. As expected, CS1-dbBiTE armed T cells showed significantly reduced effector activity in the absence of CS1 expression. Similarly, in MM mouse xenograft studies, armed T cells exhibited effective anti-tumor efficacy highlighted by reduced tumor burden in MM.1S tumor-bearing mice compared to controls. On the basis of these findings, the rationale for CS1 targeting by human T cells armed with CS1-dbBiTE presents a potentially effective therapeutic approach for targeting MM.

Therapeutic targeting of tumor spheroids in a 3D microphysiological renal cell carcinoma-on-a-chip system

Metastatic renal cell carcinoma (RCC) remains an incurable disease for most patients highlighting an urgent need for new treatments. However, the preclinical investigation of new therapies is limited by traditional two-dimensional (2D) cultures which do not recapitulate the properties of tumor cells within a collagen extracellular matrix (ECM), while human tumor xenografts are time-consuming, expensive and lack adaptive immune cells. We report a rapid and economical human microphysiological system (“RCC-on-a-chip”) to investigate therapies targeting RCC spheroids in a 3D collagen ECM. We first demonstrate that culture of RCC cell lines A498 and RCC4 in a 3D collagen ECM more faithfully reproduces the gene expression program of primary RCC tumors compared to 2D culture. We next used bortezomib as a cytotoxin to develop automated quantification of dose-dependent tumor spheroid killing. We observed that viable RCC spheroids exhibited collective migration within the ECM and demonstrated that our 3D system can be used to identify compounds that inhibit spheroid collective migration without inducing cell death. Finally, we demonstrate the RCC-on-a-chip as a platform to model the trafficking of tumor-reactive T cells into the ECM and observed antigen-specific A498 spheroid killing by engineered human CD8+ T cells expressing an ROR1-specific chimeric antigen receptor. In summary, the phenotypic differences between the 3D versus 2D environments, rapid imaging-based readout, and the ability to carefully study the impact of individual variables with quantitative rigor will encourage adoption of the RCC-on-a-chip system for testing a wide range of emerging therapies for RCC.

Vivovec™ Surface-Engineered Lentiviral Particles Mediate In Vivo CAR T Generation with Potent and Highly Durable Activity in Non-Human Primates and Tumor-Bearing Humanized Mice

Introduction: Ex-vivo generated autologous CAR T cell therapy has transformed the treatment of hematologic malignancies, driving deep and durable responses in patients refractory to conventional therapies. However, multiple challenges including complex manufacturing, high cost, and toxic pre-conditioning regimens limits access to these therapies. To overcome these challenges, a novel lentiviral vector platform, VivoVec™, is being developed. The VivoVec™ platform comprises lentiviral particles surface-engineered with a multi-domain fusion (MDF) protein assembled from T cell activating and costimulatory ligands along with a CAR transgene payload, designed to provide an off-the-shelf solution for generation of CAR T cells in vivo. Here we have evaluated the performance of VivoVec™ particles in multiple preclinical models. Following a single VivoVec™ particle injection, CAR T cells are efficiently generated in vivo and expand in response to cognate antigen, eradicate target antigen expressing cells, and form CAR T cell memory populations, in the absence of lymphodepleting chemotherapy or exogenous supportive cytokines. Methods: Mice (NSG MHCI/II knockout): Mice were engrafted with CD19+ Nalm6 tumors and resting human PBMCs, followed by intraperitoneal administration of varying doses of VivoVec™ carrying an aCD19 CAR payload. Absolute CAR T-cell numbers in peripheral blood were quantified by flow cytometry, and Nalm6 tumor burden was assessed by bioluminescence imaging. Non-Human Primates ( Macaca nemestrina): VivoVec™ surface engineered with NHP-specific surrogate MDF and carrying a human/NHP cross-reactive aCD20 CAR payload. VivoVec™ was administered via intranodal injection to 3 animals at doses of 0.77e8/kg TU in 1 animal and 2.50 e8/kg TU in 2 animals. aCD20 CAR T expansion and B-cell depletion were continuously evaluated by flow cytometry approximately weekly over ~4 months. Body weight, body temperature, neurological exams, serum chemistry panels, and complete blood counts were assessed weekly for the duration of the study. Results: VivoVec™ cultured with resting PBMCs selectively bind T cells and some NK cells in an MDF surface engineering-dependent manner, resulting in T cell activation, transduction, and CAR expression. The resultant CAR T cells demonstrate polyfunctional activity through antigen-specific tumor cell killing of Nalm6 tumor cells, cytokine secretion, and proliferation in response to serial antigen exposure. VivoVec™ administration led to dose-dependent generation of CAR T cells in Nalm6-tumor bearing humanized NSG MHCI/II knockout mice. In vivo generated CAR T cells expanded and mediated potent and durable anti-Nalm6 tumor activity. Non-Human Primates: In the two animals receiving 2.50e8 TU/kg of particles, aCD20 CAR T cells were detected in peripheral blood by flow cytometry with an early peak expansion by day 10 (representing 25.9% or 61.3% of total T cells, respectively). In the first animal, B-cell aplasia was observed from day 7 to day 42, when a small recovering B-cell population was detectable. This was closely followed by a secondary CAR T-cell expansion peaking at day 51: the CAR T cell population represented 43.2% of T cells present in the blood and resulted in recurrent B-cell aplasia sustained through day 70. Persistent B cell aplasia in the second animal receiving the 2.50e8 TU/kg dose began at day 7 and continues to be monitored. VivoVec™ was well-tolerated with no evidence of toxicity associated within, or shortly after the period of administration. Mild CRS was observed in association with both early and late CAR T cell expansions. Conclusions: VivoVec™ with MDF surface engineering enables potent and specific generation of functional CAR T cells in vivo in multiple preclinical models, including immune competent NHPs. Importantly, the generation and expansion of CAR T cells occurs in the absence of lymphodepleting chemotherapy, or supportive exogenous cytokines, thus the MDF engineering could impart properties consistent with a natural T cell effector response followed by formation of functional memory T cells. VivoVec™ represents a novel therapeutic platform in oncology that has the potential to overcome many of the challenges associated with the current ex vivo CAR T cell approaches. Additional data from ongoing NHP studies will be provided at the time of presentation.

Complementary CRISPR screen highlights the contrasting role of membrane-bound and soluble ICAM-1 in regulating antigen-specific tumor cell killing by cytotoxic T cells.

Cytotoxic CD8 +T lymphocytes (CTLs) are key players of adaptive anti-tumor immunity based on their ability to specifically recognize and destroy tumor cells. Many cancer immunotherapies rely on unleashing CTL function. However, tumors can evade killing through strategies which are not yet fully elucidated. To provide deeper insight into tumor evasion mechanisms in an antigen-dependent manner, we established a human co-culture system composed of tumor and primary immune cells. Using this system, we systematically investigated intrinsic regulators of tumor resistance by conducting a complementary CRISPR screen approach. By harnessing CRISPR activation (CRISPRa) and CRISPR knockout (KO) technology in parallel, we investigated gene gain-of-function as well as loss-of-function across genes with annotated function in a colon carcinoma cell line. CRISPRa and CRISPR KO screens uncovered 187 and 704 hits, respectively, with 60 gene hits overlapping between both. These data confirmed the role of interferon-γ (IFN-γ), tumor necrosis factor α (TNF-α) and autophagy pathways and uncovered novel genes implicated in tumor resistance to killing. Notably, we discovered that ILKAP encoding the integrin-linked kinase-associated serine/threonine phosphatase 2 C, a gene previously unknown to play a role in antigen specific CTL-mediated killing, mediate tumor resistance independently from regulating antigen presentation, IFN-γ or TNF-α responsiveness. Moreover, our work describes the contrasting role of soluble and membrane-bound ICAM-1 in regulating tumor cell killing. The deficiency of membrane-bound ICAM-1 (mICAM-1) or the overexpression of soluble ICAM-1 (sICAM-1) induced resistance to CTL killing, whereas PD-L1 overexpression had no impact. These results highlight the essential role of ICAM-1 at the immunological synapse between tumor and CTL and the antagonist function of sICAM-1.

Lipid mediators in the regulation of innate and adaptive immunity.

Lipid mediators in the regulation of innate and adaptive immunity.

Abstract 6344: Recombinant Immunotoxin exhibited targeted killing of Trop2 overexpressing tumour cells lines

Abstract Introduction: The high prevalence of cervical cancer remains a global challenge particularly in developing countries where its therapy is principally by chemoradiation marked by severe toxicities. Antibody-based therapy targeting specific overexpressed surface antigen has proven as a promising strategy. Tumor-associated calcium signal transducer 2 (Trop2), also known as epithelial glycoprotein-1 antigen, is a membrane protein found in epithelial tissues involved in cellular signalling, migration, proliferation, and differentiation in normal cells. Its overexpression is validated in several tumor types including basal, squamous and adenocarcinomas of the cervix, breast, colon, and gastrointestinal tracts. Due to its differential overexpression, Trop2 is a viable therapeutic marker whereby a recombinant immunotoxin composed of a single chain variable antibody fragment (scFv) armed with Pseudomonas exotoxin A (Anti-Trop2-ETA) may be delivered for targeted killing of such tumors. Methods: Plasmids encoding Anti-Trop2-ETA were designed in silico by fusion of anti-Trop2 single chain variable fragment (scFv) antibody to the N-terminus of Pseudomonas exotoxin A and then cloned into an pMT backbone. Expression was performed in BL21 E. Coli cells under osmotic stress and then Anti-Trop2-ETA was purified by IMAC via an N-terminus encoded polyhistidine tag. Purified fractions were structurally characterized by SDS PAGE gel and immunoblotting to confirm the presence of the Anti-Trop2-ETA protein to be used for treatment of tumor cell lines. Trop2 expression cervical cancer and breast tumor cell lines were confirmed, and cells were treated with Anti-Trop2-ETA. Results: Dose dependent killing by Anti-Trop2-ETA was observed in the Trop2 expressing tumor cell lines. IC50 values were significantly lower for Trop2 expressing cells as compared to control cells lacking Trop2 expression. Conclusion: Here, we demonstrated antigen specific killing of Trop2 overexpressing tumor cells in vitro. Targeted deployment of recombinant immunotoxin to specifically engage and kill Trop2 positive cells is a potential approach for cancer therapeutics. As such, the ability of the rIT to specifically target and kill Trop2 expressing tumors is an important initial finding towards the possibility of antigen-dependent elimination of Trop2 expressing cancer cells. Ongoing evaluations are aimed at antigen dependent biological activity as well as pharmacokinetics of the rIT in tumor bearing in vivo models. Citation Format: Dennis Makafui Dogbey, Sizalobuhle Masuku, Stefan Barth. Recombinant Immunotoxin exhibited targeted killing of Trop2 overexpressing tumour cells lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6344.