Cell Killing Research Articles

Abstract 4586: ITF3756 increases NKG2D expression and cytotoxic activity of activated human CD8 T cells

Abstract Effector cytolytic CD8 T cells play a major role in the recognition and killing of cancer cells. These cells are short living due to the loss of their self-renewal capacity and rapid exhaustion. Enduring antitumor immune response relies on the capacity of regenerating effector cells upon antigen re-encounter by memory cells. Focusing on molecules that could modulate the differentiation of T cells towards a memory subset with a prolonged anti-tumor activity is strategic for an efficient anti-tumor immunotherapy. Thus, we developed a selective HDAC6 inhibitor currently in Phase I clinical trial, ITF3756, which in vitro drives the differentiation of human CD8 T cells towards a central memory phenotype with reduced expression of exhaustion markers and higher expression of IFNγ and Granzyme b upon tumor cells coculture. This suggests that ITF3756-treated CD8 T cells could have a greater tumor killing activity. Moreover, if this augmented cytotoxic activity is directed not only towards tumor cells expressing MHC I but also towards MHC I negative cells, the anti-tumor efficacy could be improved. We thus selected the MHC I negative K562 leukemic cell line as target in an in vitro model of CD8 T cell killing assay. CD8 T cells were stimulated with anti CD3CD28 beads with or without ITF3756, and then co-cultivated with K562 cells for 4h. ITF3756 treatment improved significantly CD8 mediated K562 killing over this short period of time. However, since the effectiveness of memory cells is based on their capacity of maintaining a long-lasting immune response, we monitored the cytolytic activity over a period of 2 weeks. After 14 days of co-culture, ITF3756 treated CD8 T cells showed a higher cytotoxic capacity compared to control cells. These results indicate that ITF3756-treated CD8 T cells can kill a target tumor cell in a more efficient way independently of MHC I restricted tumor recognition, both after short and long term in vitro co-culture. Since it has been described that CD8 T cells can also kill MHC I-negative tumor cells through the NKG2D-NKG2DL axis, we assessed if ITF3756 could modulate the expression of NKG2D on CD8 T cells. Indeed, ITF3756-treated CD8 T cells had a significantly higher expression of NKG2D compared to untreated cells. In conclusion, we show that ITF3756 promotes the differentiation of cells that possess better effector activity when co-cultured with tumor cells for both short and long periods of time. ITF3756 increased the expression of NKG2D and this could be a driver of the increased cytolytic activity. One mechanism of tumor immune escape is the downregulation of MHC I. Our results suggest that ITF3756 could be used to improve the efficacy of T cell therapy by enhancing the cytolytic activity even in the absence of MHC I. Citation Format: Chiara Ripamonti, Valeria Spadotto, Christian Steinkuhler, Gianluca Fossati. ITF3756 increases NKG2D expression and cytotoxic activity of activated human CD8 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 4586.

Abstract 2631: HMGA1 chromatin regulators drive immune evasion in myeloproliferative neoplasms by repressing gene networks involved in antigen presentation

Abstract Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell disorders caused by hyperactive JAK/STAT signaling and increased risk of transformation to acute myeloid leukemia (AML). However, targetable mechanisms driving progression remain elusive and therapies are ineffective after leukemia develops. We discovered that HMGA1 chromatin regulators are required for leukemogenesis in JAK2V617F models of MPN AML by dysregulating transcriptional networks involved in proliferation and cell fate (Li et al, Blood 2022). Multi-omics analyses also showed that HMGA1 represses gene networks involved in interferon γ signaling in JAK2V617F AML cells, a pathway that drives immune escape in solid tumors. We therefore sought to test whether HMGA1 drives immune evasion during leukemic transformation in MPN. Integrating RNA/ChIP/ATACseq in JAK2V617F AML cells revealed that HMGA1 represses transcriptional networks involved in antigen presentation, including genes encoding major histocompatibility complex (MHC) class I and II proteins. Silencing HMGA1 via CRISPR or shRNA results in up-regulation of MHC genes, with greatest induction of MHC class II (MHC II) genes (HLA-DRA, DRB1, DPA1, DPB1). Further, HMGA1 depletion increases protein levels of MHC II. To determine how HMGA1 represses MHCII genes, we examined genome architecture at the MHC II loci. We found that HMGA1 recruits repressive histone marks to regulatory regions for MHC II genes which preclude binding by CTCF, a chromatin regulator involved in genome organization, and CIITA, a transcription factor that activates MHC II genes. HMGA1 depletion enhances chromatin accessibility at critical enhancers (super enhancers) involved in MHC II expression, which allows CIITA and CTCF to activate MHC II genes. Because the histone acetylase inhibitor, entinostat, induces MHC II genes in solid tumors, we assessed MHC II with entinostat and HMGA1 depletion. HMGA1 silencing enhances up-regulation of MHC II by entinostat. To test the functional significance of HMGA1 in immune evasion, we performed co-culture experiments with T cells and JAK2V617F AML cells which showed that HMGA1 silencing in AML cells activates T cells, resulting in cytotoxic T cell killing of JAK2V617F AML cells. To examine the relevance of this pathway in patients, we interrogated RNAseq from peripheral blood mononuclear cells and found that HMGA1 overexpression is associated with repression in MHC II genes in about 30% of MPN patients after progression to AML. Together, these data define a new mechanism of gene repression by HMGA1 through chromatin compaction and repressive histone marks that preclude CIITA and CTCF binding to the MHC II loci. Both HMGA1 depletion and entinostat up-regulate MHCII genes, thus illuminating HMGA1 as a potential therapeutic target to stimulate an immune attack and prevent MPN progression. Citation Format: Linda M. S. Resar, Joseph Kim, Audrey-Ann Supreme, Bailey West, Mariah Antopia, Hyungsung Woo, Karen Reddy, Jung-Hyun Kim, Leslie Cope, Jerry Spivak, Alison Moliterno. HMGA1 chromatin regulators drive immune evasion in myeloproliferative neoplasms by repressing gene networks involved in antigen presentation [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 2631.

Abstract 6341: Targeting myeloid epithelial tyrosine kinase (MERTK) receptor in acute myeloid leukemia using a novel antibody-drug conjugate, RGX-019-MMAE

Abstract Background: Myeloid epithelial reproductive tyrosine kinase (MERTK), a transmembrane protein receptor from the TAM (Tyro3, Axl, Mertk) family, is overexpressed in cancer and associated with reduced apoptosis and chemoresistance, making it an attractive therapeutic target. RGX-019-MMAE, a novel humanized IgG1-MMAE antibody-drug conjugate (ADC) (Inspirna, Inc), selectively binds to MERTK with high affinity on tumor cells, resulting in internalization and degradation of the receptor. It then induces cytotoxicity through the release of the payload, MMAE (monomethyl auristatin E), which disrupts mitosis. We hypothesize that targeting MERTK via RGX-019-MMAE exerts an antileukemic effect. Methods: First, to determine the clinical relevance of MERTK, using the Oregon Health and Science University (OHSU) acute myeloid leukemia (AML) dataset, we divided patients into low and high MERTK mRNA expression based on mean expression and compared their overall survival. To identify the AML subtypes with the highest MERTK expression, we analyzed samples from 810 AML patients at MD Anderson using reverse phase protein arrays (RPPA), as well as 8 AML cell lines and the peripheral blood of 9 AML patients using flow cytometry. Then, the cell lines with the highest MERTK expression were treated with varying doses of RGX-019-MMAE or isotype control for 120 hours and assessed for viability with CellTiter-Glo 2.0. Likewise, we administered RGX-019-MMAE to primary cells from AML patients and determined the anti-leukemic effect. Finally, we investigated the synergistic effect of RGX-019-MMAE with venetoclax, a BCL2 inhibitor, or cytarabine, a chemotherapy agent, in vitro. Results: In the AML OHSU dataset, patients with high MERTK mRNA expression had significantly worse overall survival (p=0.02). RPPA revealed that patients with PTPN11 mutation, t (9;11), and monocytic AML subtypes had significantly higher MERTK protein expression. MERTK protein expression varied in AML cell lines and was highest in Kasumi-1 and OCI-AML3. Treatment of these two cell lines with RGX-019-MMAE resulted in significantly more killing of leukemic cells than the isotype control ADC in a dose-dependent manner (p<0.01). Similarly, in primary AML cells with high MERTK expression, RGX-019-MMAE treatment induced significant cell death compared to the control ADC. In addition, Kasumi-1 and OCl-AML3 cells treated with RGX-019-MMAE combined with venetoclax or cytarabine showed a synergistic cytotoxic effect in a dose-dependent manner. Conclusion: High MERTK expression in monocytic AML suggested that MERTK is a promising therapeutic target in this subtype. RGX-019-MMAE significantly induced AML cell death and produced a synergistic anti-leukemic effect in combination with chemotherapeutic agents and targeted therapy in vitro, suggesting its potential for targeting patients with high-risk AML. Citation Format: Anudishi Tyagi, Maryam Siddiqui, Isabel Kurth, Shugaku Takeda, Amanda Eckstrom, Jenny Borgman, Abhishek Maiti, Venkata Lokesh Battula. Targeting myeloid epithelial tyrosine kinase (MERTK) receptor in acute myeloid leukemia using a novel antibody-drug conjugate, RGX-019-MMAE [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 6341.

Abstract 2732: NB203: A Novel therapeutic bispecific antibody targeting CEACAM1/VEGF for tumor immunity and angiogenesis modulation in the tumor microenvironment

Abstract The carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is detected on leukocytes, epithelia and endothelia, and involved in cell adhesion through homophilic or heterophilic binding. In various gastrointestinal cancers, NSCLC (non-small cell lung cancer), and melanoma, CEACAM1 is highly expressed on tumor cells and tumor stroma, with its levels increasing as the disease progresses. Notably, CEACAM1 has been found to dampen T and NK cell functions while promoting tumor angiogenesis and metastasis. In this study, we present NB203, a novel CEACAM1/VEGF bispecific antibody developed using Neologics CEACAM-plus, a bifunctional molecule engineering platform designed to target and modulate the tumor microenvironment (TME). NB203 effectively accumulated in the TME and hindered the homophilic or heterophilic interactions of CEACAM1. It demonstrated a significant enhancement in T cell activities and NK cell-mediated killing of CEACAM1-expressing tumor cells, and the inhibition of tumor cell migration and polyploidy through macrophages. More importantly, NB203 was specifically designed to impede tumor angiogenesis. It exhibited an increased binding capacity to both CEACAM1 and VEGF in pro-angiogenic TME, and undermined intratumoral vessel maturation by blocking VEGF and negatively regulating myeloid cell-dependent tumor angiogenesis. In summary, our preclinical data indicate that NB203 exhibits effective anti-tumor activity by mediating NK and cytotoxic T cell activities, improving the immune-suppressive TME, and suppressing tumor angiogenesis. The use of NB203 holds promise in overcoming resistance to anti-VEGF therapy and substantially improving the safety of therapeutic targeting of angiogenesis in cancer treatment. Citation Format: Jinyu Dong, Binbin Wang, Dong Wang, Jie Ni, Tingting Bu, Haojie Wang, Bishnu Nayak, Baiyang Wang, Xin Dong, Yu Zhang. NB203: A Novel therapeutic bispecific antibody targeting CEACAM1/VEGF for tumor immunity and angiogenesis modulation in the tumor microenvironment [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 2732.

Abstract 1899: Novel combinations of aplitabart, a DR5 agonist IgM antibody, with ADCs or chemotherapeutic agents lead to robust anti-tumor responses in solid tumor models

Abstract Agonism of death receptor 5 (DR5), a tumor necrosis factor receptor superfamily member, induces the killing of tumor cells via the extrinsic apoptotic pathway upon receptor multimerization. We have engineered a multivalent IgM DR5 agonist antibody, aplitabart (IGM-8444), that induces robust anti-tumor activity in both in vitro and in vivo preclinical models. We also demonstrated potent synergistic in vitro activity of aplitabart with different classes of chemotherapeutic agents including microtubule inhibitors, nucleoside analogs and topoisomerase inhibitors in a range of solid cancer cell lines. Preliminary results from an ongoing phase 1a/ab clinical study show that aplitabart has an encouraging safety profile and promising activity in combination with FOLFIRI ± bevacizumab in heavily pretreated metastatic colorectal cancer patients. To further explore the combination therapies for aplitabart in lung and breast cancers, we evaluated standard of care chemotherapies, such as paclitaxel, carboplatin, and antibody drug conjugates (ADCs) in vitro on a range of human lung and breast cancer cell lines. We observed dose-dependent synergistic cytotoxic effects of aplitabart on tumor cells when combined with these agents. Additionally, these agents increased the expression of DR5 on tumor cells and could explain their synergistic combinatorial activity with aplitabart. Representative cancer cell lines were selected to evaluate these combinations in vivo using xenograft mouse models where robust anti-tumor responses were demonstrated in the xenograft lung and breast cancer models, resulting in enhanced tumor growth inhibition and extended survival. Our findings demonstrate potent in vitro synergistic cytotoxicity and enhanced anti-tumor response in preclinical models in vivo by combining aplitabart with ADCs, or carboplatin and paclitaxel. These results support the combination of DR5 agonist IgM antibodies with agents known to upregulate DR5 expression on solid tumors. Aplitabart is currently under evaluation in a randomized clinical study in combination with FOLFIRI + bevacizumab in comparison with FOLFIRI + bevacizumab in patients with colorectal cancer (NCT04553692). Citation Format: Mélanie Desbois, Susan E. Calhoun, Kevin C. Hart, Carolyn R. Denson, Poonam Yakkundi, Thomas J. Matthew, Maya K. Leabman, Sanela Bilic, Genevive Hernandez, Eric W. Humke, Albert F. Candia, Bruce Keyt, Angus M. Sinclair, Maya F. Kotturi, Beatrice T. Wang. Novel combinations of aplitabart, a DR5 agonist IgM antibody, with ADCs or chemotherapeutic agents lead to robust anti-tumor responses 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 1899.

Abstract 5277: The ROCK-2 inhibitor belumosudil exerts a direct antimyeloma effect and improves isatuximab-mediated cytotoxicity against multiple myeloma cells

Abstract Multiple myeloma (MM) is a plasma cell malignancy characterized by clonal accumulation of malignant plasma cells in the bone marrow. Isatuximab (Sarclisa®) is a monoclonal antibody used for the treatment of MM. Isatuximab binds to CD38 (highly expressed on MM cells) and induces tumor cell killing via several mechanisms including antibody dependent cellular cytotoxicity (ADCC) and direct apoptosis. Belumosudil (RezurockTM) is a ROCK2 inhibitor that is approved for the treatment of chronic graft versus host disease (cGVHD). Recent reports suggest that inhibition of ROCK2 induces apoptosis and prevents growth of MM cells. Here, we investigated the potential antimyeloma effect of belumosudil alone or in combination with isatuximab with different readouts of viability, apoptosis and cytotoxicity. The potential cytotoxic effect of belumosudil (as single agent or in combination with isatuximab) against MM cells was assessed in vitro by flow cytometry apoptosis assay, CellTiter-Glo® luminescent cell viability assay or long-term cytotoxic assay (Incucyte). The effect of belumosudil on healthy donor-derived NK cells viability was also assessed by flow cytometry. Belumosudil reduced the number and viability of several MM cell lines without affecting healthy donor NK cell number and viability. Moreover, belumosudil induced apoptosis of MOLP-8 MM cells in a dose-dependent manner and further increased MOLP-8 cell apoptosis when combined with isatuximab after 2, 3 and 4 days of in vitro treatment. Belumosudil induced killing of MM cells in a dose-dependent manner over time (up to 4 days), independently of the presence of NK cells, as measured by Incucyte-based cytotoxicity assay. In addition, the combination of belumosudil (3.3 µM) with isatuximab (10 µg/ml) in presence of NK cells enhanced the killing of different MM cell lines over time compared to single agents.Finally, the expression of CD38 on MM cells has been documented to be decreased after treatment with anti-CD38 antibodies. Interestingly, analysis of CD38 expression on MM cells indicated that belumosudil induces an increase of CD38 on the surface of MOLP-8 MM cells and prevents isatuximab-induced decrease of CD38 expression. These data suggest that belumosudil has a direct antimyeloma effect and increases isatuximab-mediated cytotoxicity against MM cells, without affecting the viability of NK cells. Taken together, this study provides evidence of the therapeutic potential of belumosudil in combination with isatuximab in the setting of MM. Citation Format: Marco Meloni, Pauline Perrin, Claire Nouguier, Stephane Poirier, Monsif Bouaboula, Kamlesh Bisht, Helgi Van de Velde, Angela Virone-Oddos, Marielle Chiron. The ROCK-2 inhibitor belumosudil exerts a direct antimyeloma effect and improves isatuximab-mediated cytotoxicity against multiple myeloma 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 5277.

Abstract 4099: AMP-peptide vaccination against multiple p53 mutant epitopes promotes lymph node delivery to generate potent, functional T cell immunity

Abstract Background p53 is the most commonly mutated gene in human cancer, prevalent in nearly all tumor types. Despite its significant medical relevance and the knowledge that human T cells recognize these mutations[1,2], immunotherapies designed to promote responses against mutated p53 (mp53) have not had the hoped-for clinical impact[3]. The Amphiphile (AMP) platform improves the potency of vaccine immunotherapy by programming the delivery of vaccine components to the lymph nodes where efficient uptake by immune cells initiates tumor-targeted immune responses. AMP-modification of vaccine components (peptide antigens, molecular adjuvants) results in covalent conjugation to albumin-binding lipids. Upon injection, AMP-vaccines associate with tissue-resident albumin which efficiently distributes to draining lymph nodes. This approach was shown to promote activation of polyfunctional, cytotoxic T cells with promising safety and improved clinical outcomes in a Phase 1 trial of ELI-002, an mKRAS AMP therapeutic vaccine (AMPLIFY-201 NCT05726864). Application of this strategy to p53 mutations with ELI-008 offers the potential for improved immunotherapeutic activity in a setting of significant unmet need. Methods Following immunization of C57BL/6J mice with AMP-modified or soluble comparator vaccines consisting of mp53 peptides and CpG adjuvant, analyses were performed 7 days after the third bi-weekly dose. To assess antigen-specific T cell responses, ELISpot (IFNγ, GzmB), multiplexed proteomic, and flowcytometric analysis of effector cytokines (IFNγ, TNFα, IL-2) were performed following antigenic stimulation. Responses were determined in secondary lymphoid tissues and lung. Cytolytic capabilities of antigen-specific T cells were evaluated by monitoring specific killing of IV-transferred antigen-pulsed target cells. Results AMP-immunization generated robust immune responses yielding strong T cell activation against common p53 hot spot mutations (R248W, R248Q, R175H, G245S, R273H, Y220C, C135Y, R158H, H214R). Responses to AMP-vaccination were characterized by the generation of increased frequency of polyfunctional T cells (IFNγ, TNFα, IL2) specific to mp53 epitopes. Induced T cells demonstrated significant levels of cytolytic activity including GzmB production and elimination of target cells in vivo. Non-lymph targeted vaccines using soluble comparators were inactive. Conclusions AMP-conjugation permits efficient delivery directly to the lymph nodes and thus improves the immunogenicity of peptide vaccination. These substantially improved immune responses induced by ELI-008 represent a promising therapeutic opportunity for targeting cancer in a large fraction of human tumors. The AMP-platform technology is simple, rapid and scalable, promising broad clinical, off-the-shelf application for treating p53 mutated tumors. Citation Format: Martin P. Steinbuck, Xavier Cabana-Puig, Erica Palmer, Mimi M. Jung, Thomas Williams, Kristen Osaer, Jeff Zhang, Christopher M. Haqq, Peter C. DeMuth. AMP-peptide vaccination against multiple p53 mutant epitopes promotes lymph node delivery to generate potent, functional T cell immunity [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 4099.

Abstract 6706: An anti-claudin 18.2/CD3 bispecific antibody for the treatment of claudin 18.2 positive gastric cancer

Abstract The claudin18.2 (CLDN18.2) protein shows four transmembrane domains (TMDs) with two extracellular loops (ECL), ECL-1 and ECL-2. It is a highly selective biomarker with limited expression in normal tissues and often exhibits abnormal expression during the occurrence and development of various primary malignant tumors. The specific expression pattern supports the notion that CLDN18.2 is a distinctive molecule for targeted therapy in various cancers, particularly gastric and pancreatic cancers. Various drugs targeting CLDN18.2, including monoclonal antibodies, ADCs, CAR-T, and bispecific antibodies, have also entered clinical trials. As of this writing, there are currently no commercially available products worldwide that specifically target CLDN18.2. However, Zolbetuximab (IMAB362) has successfully reached the Phase III end point, indicating positive clinical outcomes and establishing CLDN18.2 as a promising cellular and antibody therapeutic option. Here, we describe LNF2007, an anti-CLDN 18.2/CD3 bispecific antibody that can redirect CD3+ effector T cells to CLDN18.2+ tumor sites, resulting in the activation of T cells and subsequent killing of target cells. The design of LNF2007 focuses on selecting a relatively weak and reasonable affinity to CD3, accompanied by the suppression of Fc-mediated effector functions. This aim is to minimize off-target toxicity and maximize therapeutic efficacy. In vitro data demonstrate that LNF2007 binds more strongly to CLDN18.2+cells than to CD3+ cells. LNF2007 exhibited good dose-dependent activation and cytotoxicity against engineered cell lines BXPC3-hCLDN18.2-Luc and CHOK1-hCLDN18.2-Luc, which are positive for CLDN18.2 expression .In the in vivo pharmacodynamics assay, LNF2007 also demonstrated superior efficacy in the humanized NUGC4-CLDN18.2 model and BxPC3-CLDN18.2 model. Furthermore, a 4-week repeated dose (up to 1 mg/kg) toxicity study in cynomolgus monkeys showed that LNF2007 was safe and well tolerated. In vitro cytokine release was lower in the LNF2007 group than that in the AMG 910 and AZD5863 (two another anti-claudin18.2/CD3 bispecific antibody) groups. In conclusion, the novel anti-CLDN18.2 × anti-CD3 bispecific antibody LNF2007 demonstrates similar efficacy to AMG 910 and AZD5863 and is safer. LNF2007 provides a promising therapy for claudin 18.2-positive cancer patients.Taishan Industry Leading Talents Project of Shandong Province was a sponsor of this research. Citation Format: Lili Zhao, Guimin Zhang, Zhong Liu, Jinhua Xu, Lizhi Zhao, Guangyan Li, Bin Li, Zhongsong Zhu, Wei Peng, Yuqiang Zhu, Zhaowei Chen, Zhenyu Li. An anti-claudin 18.2/CD3 bispecific antibody for the treatment of claudin 18.2 positive gastric cancer [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 6706.

Abstract 4109: Discovery of a novel cancer-specific antigen for therapeutic targeting using the Oncotope platform

Abstract Identification of druggable cancer-specific surface antigens is hindered by the complexity of cancer's molecular diversity and the risk of normal cell cross-reactivity. We developed the Oncotope Platform that rapidly identifies multiple cancer-specific cell surface targets not expressed on normal cells (JCO 2022). In this study, we generated polyclonal antibodies to human Triple Negative Breast Cancer (TNBC; Hs578T, ATCC). Following this, we used the Oncotope Platform to filter the anti-TNBC antibody-enriched serum, to yield cancer specific polyclonal antibodies. Using a Protein Microarray, we assessed the binding affinity of both the Total Anti-TNBC Serum (before filtration) and the Oncotope Filtered Anti-TNBC Serum towards approximately 25,000 human proteins. Our results identified antigens that exhibited significantly higher affinity binding to the Oncotope Filtered Anti-TNBC Serum than the Total Anti-TNBC Serum. One of these antigens ZIP7, a zinc transporter situated in the ER and Golgi, has been shown to activate cell proliferation related signaling pathways in TNBC. Our findings revealed the aberrant cell surface expression of ZIP7 on TNBC cells and its potential as a therapeutic target. Flow cytometry analysis using rabbit polyclonal antibodies against ZIP7 revealed substantial binding to TNBC cells, while no significant binding was observed with normal breast epithelial (NBE) cells from the same patient (Hs578BsT, ATCC). Additionally, cytotoxicity assays, employing the same antibodies and a secondary anti-rabbit ADC, showed the preferential killing of TNBC cells over NBE cells (Table 1). In summary, our study marks a breakthrough in identifying cancer-specific antigens with therapeutic potential. The Oncotope Platform, in combination with protein microarrays, enables rapid identification of unique cancer-specific antigens absent in normal cells. Specifically targeting ZIP7 on TNBC cell surfaces highlights its promise for precision cancer therapy. Table 1. Cell Line Incubated with: %Binding Flow Cytometry (1:400 Ab dilution) %Cytotoxicity (4ug/ml Ab conc.) TNBC (Hs578T) Total Anti-TNBC Serum 96.65 94.5 +/- 2.5 Oncotope Filtered Anti-TNBC Serum 97.46 79.2 +/- 2.1 ZIP7 Polyclonal antibody ((Proteintech 11200-1-AP) 46.2 73.2 +/- 0.5 Normal Breast Epithelial cells (Hs578Bst) Total Anti-TNBC Serum 92.95 92.3 +/- 3.0 Oncotope Filtered Anti-TNBC Serum 20.39 17.9 +/- 4.5 ZIP7 Polyclonal antibody ((Proteintech 11200-1-AP) 6.37 14.1 +/- 1.6 Citation Format: John Sanil Manavalan, Danielle Mor, Joseph Davis, Sharanjot Saini, Ipsita Pal, David Feith, Yuichi Hikichi, Elliot Davis. Discovery of a novel cancer-specific antigen for therapeutic targeting using the Oncotope platform [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 4109.

Abstract 2355: SGN-EGFRd2 binding and activity are agnostic to common EGFR extracellular resistance mutations acquired in response to anti-EGFR targeted antibody therapies

Abstract SGN-EGFRd2 is an investigational bispecific antibody comprised of two camelid-derived humanized variable heavy chain only (VHH) domains, one targeting Vγ9Vδ2 (gamma delta) T cells and the other targeting the epidermal growth factor receptor (EGFR). Selective antitumor activity occurs when two conditions are met: 1) the molecule engages both EGFR-expressing tumor cells and gamma delta T cells and 2) butyrophilins, in complex with phosphoantigens (pAgs), are expressed by EGFR-positive tumor cells, resulting in gamma delta T cell directed tumor cell killing by activation, degranulation and secretion of cytolytic molecules. The tumor specific proximity of gamma delta T cells and expression of the butyrophilins/pAgs complex results in the killing of EGFR-expressing tumor cells but not EGFR-expressing normal cells. EGFR is an oncogenic receptor tyrosine kinase and target of several classes of therapeutic modalities, including antibodies. Two antibodies are currently approved for the treatment of EGFR-expressing, KRAS wild-type metastatic colorectal cancer (mCRC): cetuximab (CET) and panitumumab (PAN). Although these anti-EGFR therapies provide significant survival benefits to patients, the duration of response is transient, and most patients progress and develop secondary resistance [1]. One such escape mechanism is the acquisition of mutations in the extracellular domain (ECD) of EGFR, which prevent binding of therapeutic antibodies [2]. Because SGN-EGFRd2 will be tested on patients previously exposed to anti-EGFR therapeutic antibodies, it is paramount to assess its binding to EGFR ECD mutations identified in antibody resistant mCRC patients. EGFR-negative A2058 cells were transduced to express wild type EGFR and a panel of EGFR ECD resistance mutations (N=16). The binding specificity and kinetics of SGN-EGFRd2 were compared to CET and PAN by flow cytometry on engineered cell lines and biolayer interferometry, respectively. Results indicated SGN-EGFRd2 maintained the ability to bind to all tested EGFR ECD mutants, whereas CET and PAN were unable to bind several ECD mutants, as previously described [3,4]. SGN-EGFRd2 binding to EGFR ECD mutant cell lines induced the production of interferon gamma and expression of cell surface CD107a on gamma delta T cells, confirming functional engagement. In contrast to current anti-EGFR therapeutic antibodies, SGN-EGFRd2 binding and activity was unaffected by commonly identified EGFR ECD mutations. These findings highlight SGN-EGFRd2 as a novel molecule targeting wild-type EGFR and common EGFR ECD mutations identified in the mCRC setting. Citation Format: Liem Nguyen, Chun-Shu Wong, Serena Wo, Bryan Grogan, Daniel Diolaiti, Maria Corinna Palanca-Wessels, Astrid Clarke. SGN-EGFRd2 binding and activity are agnostic to common EGFR extracellular resistance mutations acquired in response to anti-EGFR targeted antibody therapies [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 2355.

Abstract 529: Investigating the synergistic effect of milciclib and PD0325901 in colorectal cancer therapy

Abstract Milciclib, characterized as a potent nanomolar inhibitor of multiple cyclin-dependent kinases, has recently emerged as a promising therapeutic agent in cancer treatment, particularly with its additional role as a spliceosome modulator. Our recent studies employing RNA sequencing technology revealed a comprehensive profile of Milciclib-induced transcriptional changes in colorectal cancer cells, identifying several key regulated pathways. In light of these findings, we explored a novel therapeutic strategy: combining Milciclib with specific inhibitors targeting pathways upregulated by Milciclib treatment. This hypothesis is based on the rationale that such a combination could exert a synergistic effect. We have assessed the efficacy of this combinational therapy and found that the combination of Milciclib and PD0325901 greatly potentiates the killing of colorectal cancer cells versus either treatment alone. PD0325901 has been extensively studied for its efficacy in targeting the MEK/ERK signaling pathway, a critical pathway in many cancers, including colorectal cancer. To further characterize the underlying molecular mechanisms contributing to the observed synergistic effect, we applied quantitative proteomic analysis of 8107 proteins in human colorectal cancer cells with the treatment of different doses of Milciclib and PD0325901 administered alone, or in combination. Our results demonstrate 49 proteins were significantly decreased in a dose-dependent manner, and that many of these proteins are key players regulating pathways associated with the cell cycle, apoptosis, gene expression, metabolism, WNT signaling, and the MEK/ERK signaling pathway. The discovery of the down-regulation of these proteins and pathways after treatment provides a molecular basis to elucidate the synergistic mechanism underlying Milciclib and PD0325901 combination therapy. In conclusion, our study establishes the combinatorial use of Milciclib and PD0325901 as a potential breakthrough in the treatment of colorectal cancer, offering a promising prospect for enhancing future patient outcomes. Citation Format: Xinyu Pei, Anh Nguyen, Hannah Neiger, Wenjia Wang, William Bautista, Lily Wang, Alvan Cai, Valerie A. Gerriets, John K. Cusick, Yihui Shi. Investigating the synergistic effect of milciclib and PD0325901 in colorectal cancer therapy [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 529.

Abstract 1884: DXC006, Anti-CD56-CPT113 ADC displays favorable anti-tumor efficacy, pharmacokinetic and safety profiles in preclinical studies

Abstract CD56, also known as neural cell adhesion molecule 1 (NCAM1), is a type I plasma membrane glycoprotein involved in cell-cell and cell-matrix adhesion. It is overexpressed in almost all neuroblastomas, 95% of small cell lung cancers and 78% of multiple myeloma patients[1], whereas CD56 is less frequently or less abundantly expressed in normal tissues, making it a potential target for tumor therapy. So far, no CD56-targeting ADCs have entered late-stage clinical trials.DXC006 is an antibody-drug conjugate of a humanized anti-CD56 antibody (DXA006) linked to the topoisomerase I inhibitor CPT113 through a cleavable peptidyl linker and CROSSCONJU™ technology. The pharmacologic activity and mechanism of action of DXC006 were investigated in several human cancer cell lines and xenograft mouse models. Pharmacokinetic and safety profiles were also assessed in rats and cynomolgus monkeys.DXC006 binds specifically to CD56 and internalizes into tumor cells, after intracellular trafficking to lysosome and CPT113 releasing, induces DNA damage. In vitro cell based assays showed that DXC006 remarkably inhibited the cell growth of CD56-positive cell lines of IMR-32 (neuroblastoma), NCI-H526 (small cell lung cancer), and NCI-H929 (multiple myeloma), with IC50 of 0.0046~0.061 nmol/L. Although DXC006 also binds to CD56 expressed NK cells, we found that the inhibition of DXC006 to human NK cells was much less effective, with IC50 higher than 675 nmol/L, which is ten thousand-folds less potent than that of targeted abnormal cells. In vivo, DXC006 demonstrated good durable antitumor activities in three CD56-positive xenograft models of IMR-32, NCI-H526 and NCI-H929 cell lines, with a single dose of 2 mg/Kg, 3 mg/Kg, and 5 mg/Kg, respectively. No animal death or moribund outcome was observed in two months during preclinical safety studies in 150 mg/Kg Q2W dosed rats. For cynomolgus monkeys, the highest non-severely toxic dose (HNSTD) of DXC006 was 20 mg/Kg, in Q2W, four times of administration. PK profiles of both DXC006 the naked antibody DXA006 were comparable in both rats and monkeys. In summary, DXC006 demonstrated strong antitumor activity in various types of cancer cells both in vitro and in vivo, and good pharmacokinetic and safety profiles in rat and monkeys, a potential to be explored in clinical applications. [1] Yang Feng, Yanping Wang, Zhongyu Zhu, et al. Differential killing of CD56-expressing cells by drug-conjugated human antibodies targeting membrane-distal and membrane-proximal nonoverlapping epitopes. mAbs 2016; 799-810. Citation Format: Xiangfei Kong, Huihui Guo, Yong Du, Zhicang Ye, Yongxiang Chen, Zhixiang Guo, Lingli Zhang, Lu Bai, Junxiang Jia, Yunxia Zheng, Wei Zheng, Jun Zheng, Wenjun Li, Yuanyuan Huang, Zhongliang Fan, Mengmeng Liu, Binbin Chen, Meng Dai, Juan Wang, Fang Du, Miaomiao Chen, Qingliang Yang, Robert Y. Zhao. DXC006, Anti-CD56-CPT113 ADC displays favorable anti-tumor efficacy, pharmacokinetic and safety profiles in preclinical studies [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 1884.

Abstract 4641: Preclinical evaluation of the novel curcumin Analogue AKT-100 demonstrates therapeutic effectiveness in p53-mutated cancer cells

Abstract Among the myriad of molecular alterations associated with cancer, loss of the normal tumor suppressive functions of p53, the “guardian of the genome,” is the most consistent. Thus, the possibility of targeting oncogenic, mutant p53 proteins has long been a therapeutic goal. However, that aspiration has not been fully realized, leaving patients vulnerable to aggressive disease that is resistant to chemotherapy and to targeted agents such as PARP inhibitors and immunotherapy owing to the loss of wild type p53 functionality and the gain of new oncogenic functions when mutant p53 is expressed. An effective therapeutic strategy is urgently needed for p53 mutant cancers, and our team is developing novel analogues of curcumin with the potential to convert mutant p53 to a wild type conformation and restore its tumor suppressive functions. In this study, we investigated the effects of AKT-100, which was developed from the parent molecule and curcumin analogue HO-3867. Effects were compared to another drug believed to reactivate p53 functionality, APR-246, using CyQUANT IC50 cell proliferation assays and bulk and single cell RNA sequencing. Structural analyses are underway investigating the specific sites of interaction of AKT-100 with various mutant forms of p53. Our findings indicate that, first, AKT-100 exhibits impressive cell killing in multiple ovarian and serous endometrial cancer cells at concentrations ranging from 100-300 nM and is synergistic with the PARP inhibitor olaparib. Second, RNA sequencing demonstrates the reactivation of wild type p53 genes associated with normal cell cycle regulation (induction of CDKN1A encoding p21 and GADD45A), apoptosis (induction of PMAIP1 encoding Noxa and DR5 encoding Death Receptor 5), and the inhibition of DNA replication and multiple alternative mechanisms of DNA repair employed by malignant cells. Third, RNA sequencing indicates that AKT-100 acts through both p53-dependent and independent pathways to inhibit cancer cell proliferation. Gene expression is impacted in ways that portend a therapeutic effect as well as highlight potential resistance pathways (e.g. significant induction of PLK5 encoding polo like kinase 5) that can be further targeted to create synthetic lethal drug combinations with AKT-100 chosen specifically to target the various mutant forms of p53. Taken together, these results identify novel curcumin analogues in early development with the potential to improve therapy for p53 mutant cancers. Through this strategy it is also possible to identify and block resistance pathways that are activated by different forms of mutant p53 in response to AKT-100 and to create synthetic lethal precision drug combinations. Citation Format: Kimberly K. Leslie, Jamie L. Padilla, Geneva L. Williams, Hua-Ying Fan, Cristian G. Bologa, Eric R. Prossnitz, Jun-Yong Choe, Lane E. Smith, Alexander Goss, Robert J. Lake, Avinash D. Sahu. Preclinical evaluation of the novel curcumin Analogue AKT-100 demonstrates therapeutic effectiveness in p53-mutated cancer 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 4641.

Abstract 5342: Evaluation of autologous and allogeneic T cell-based therapies in ex-vivo and in-vivo xenograft tumor models

Abstract The field of adoptive T cell-based immunotherapy, including tumor-infiltrating lymphocytes (TILs), T cell receptor (TCR) & Chimeric antigen receptor (CAR) - T cells, has undergone unprecedented growth, specifically later in delivering effective and durable clinical response. Notable success with CAR-T cells is limited to hematological malignancies while clinical gains with solid tumors is still a challenge. Solid tumors’ heterogenous target expression and loss, T cell status and metabolic fitness, T cell trafficking into the tumor, and the hostile immunosuppressive tumor microenvironment (TME) have hampered T cell efficacy in the patients. There is a lack of clinically relevant solid tumor models for the translation of T cell-based therapies into the clinic. We report the development of translational ex-vivo and in-vivo platforms for evaluating cell line-derived and patient-derived xenografts (CDX and PDX) models (BarneyOI™️ model), validated with hCD3 T-cells, autologous TILs and/or allogeneic 3rd generation CAR-T cells (scFv(HER2)-CD28-4-1BB-CD3zeta CAR-T). Anti-hPDL1 but not anti-hPD1 significantly enhanced hCD3 T-cell and autologous TIL-mediated killing of tumor cells in an ex-vivo co-culture assay using Incucyte-based live cell imaging. Also, a dose-dependent killing of HER-2 expressing CDX (A549 & Colo205) and PDX was observed with HER-2 targeting CAR-T cells in an ex-vivo co-culture assay. This was in concordance with the activation, effector function, and differentiation status of the CAR-T cells, immune phenotype by Cytek aurora spectral flow cytometry. Further, to imitate the patient population and the effect of solid TME, HER-2 targeting CAR-T cells were assessed for their in-vivo efficacy and immune response differences in the subcutaneous and orthotopically implanted HER-2 expressing PDX in immunodeficient NOG mice. Our findings highlight the importance of testing T cell-based immune therapies in the appropriate translational tumor models with better certainty of clinical outcome. Citation Format: Sherry Liu, Jasmine Borroel, Carmen Sunico, Emily Eastwood, Bridget Corcoran, Bianca Carapia, Jantzen Sperry, Jonathan Nakashima, Rajeev Shrimali. Evaluation of autologous and allogeneic T cell-based therapies in ex-vivo and in-vivo xenograft 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 5342.

Abstract 7547: Enhancers as targets for improvements in immunotherapy

Abstract Role of epigenetic elements in mediating tumor immune interaction remains poorly understood. We previously identified enrichment of active enhancer states on a set of genomic loci in non-responders to immune checkpoint blockade (ICB) therapy. We noted that the activated non-responder enhancers marked a group of key regulators of in melanoma cells that are known to mediate resistance to ICB therapy and several checkpoint receptors in T cells. Through spatial epigenomics (Spatial ATAC and CUT&Tag) approaches, we identified the tumor-immune niches harboring unique gene regulatory elements and transcription factors that could mediate melanoma-T cell interaction. Further, we aimed to identify functional epigenetic elements through custom CRISPRi screening of enhancers in patient tumor-derived melanoma and T cells. CRISPRi approaches identified novel functional enhancers that mediate T cell mediated killing. For example, we identified distal c-MET enhancers as important contributors to T cell mediated killing. In T cells, we identified enhancer hubs that target multiple genes. These hubs could be targeted to activate interferon gamma, reduce T cell exhaustion, and improve T cell mediated killing of melanoma cells. Such enhancer hubs could serve as targets in the ex vivo setting to improve adoptive T cell therapy. Overall, our results suggest that enhancers with unique spatial patterns in melanoma tumors contribute to the response to immunotherapy and could be novel targets for therapy. Citation Format: Anand Singh, Veena Kochat, Emre Arslan, Suresh Satpati, Wentao Deng, Sandeep Yadav, Efthalia Bataki, Cassian Yee, Kunal Rai. Enhancers as targets for improvements in immunotherapy [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 7547.

Abstract 2362: Preclinical efficacy and safety of M9140, a novel antibody-drug conjugate (ADC) with topoisomerase 1 (TOP1) inhibitor payload targeting carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5)-expressing colorectal tumors

Abstract Background: M9140 is the first clinical-stage TOP1 inhibitor payload ADC directed against CEACAM5, which is expressed in colorectal cancer (CRC) and other cancer indications. M9140 is composed of a CEACAM5-specific antibody conjugated to eight, highly stable and hydrophilic ß-glucuronide-exatecan linker-payloads. After linker cleavage, the highly potent and membrane permeable TOP1 inhibitor exatecan is released. Methods: M9140 potency was tested in viability assays using cancer cell lines with different levels of CEACAM5 expression. Potency shift viability assays were conducted using two CRC cell lines, with zosuquidar used as multidrug resistance-1 (MDR-1) inhibitor. The M9140 bystander effect was assessed in co-culture experiments with CEACAM5-negative and -positive cancer cells. Antitumor efficacy and safety were evaluated in patient-derived xenograft (PDX) mouse models and in cynomolgus monkeys, respectively. Results: M9140 demonstrated specific binding to CEACAM5 and selective killing of target-positive cancer cells with potencies between 0.09 nM and 0.62 nM. A potent bystander effect of M9140 was demonstrated in co-culture experiments indicating the potential to treat tumors with heterogeneous target expression. Unlike other ADC payloads such as monomethyl auristatin E (MMAE) and the maytansine derivative DM4, exatecan potency was not affected by MDR-1 inhibition, indicating that this drug efflux resistance mechanism may not be relevant for exatecan. A single treatment with 10 mg/kg M9140 caused strong antitumor effects in all 14 CRC PDX models tested, with tumor stasis in 10 models and tumor regression in four models as the best response. The TOP1 inhibitor-based ADC M9140 caused strong antitumor efficacy with a tumor volume reduction of 74% and 88% as best response in two CRC PDX models where a maytansine-based CEACAM5 ADC was not effective. In cynomolgus monkeys, M9140 showed dose-dependent hematolymphoid and intestinal effects, consistent with exatecan payload, with no indication of any other toxicities such as interstitial lung disease (ILD) or ocular toxicity. Conclusions: M9140 demonstrated high potency, strong antitumor activity, and bystander effect in preclinical models. The side effect profile in monkeys was favorable and in line with the expected toxicity of exatecan. Notably, ILD and ocular toxicity, which are known adverse effects of deruxtecan and maytansine-based ADCs respectively, were absent. A first-in-human study to evaluate the safety, tolerability, pharmacokinetics, and preliminary clinical activity of M9140 in advanced solid tumors is ongoing (NCT05464030). Citation Format: Sabine Raab-Westphal, Felix Hart, Willem Sloot, Min Shan, Nicolas Rasche, Christiane Amendt, Jan Anderl. Preclinical efficacy and safety of M9140, a novel antibody-drug conjugate (ADC) with topoisomerase 1 (TOP1) inhibitor payload targeting carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5)-expressing colorectal tumors [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 2362.

Abstract 7243: CRISPR-cas9 genetic targeting of metastatic pancreatic cancer

Abstract Metastatic cancer affects millions of people worldwide annually and is the leading cause of cancer-related deaths. Most patients with metastatic disease are not eligible for surgical resection, and current therapeutic regimens have varying success rates, some with 5-year survival rates below 5%. Here we test the hypothesis that metastatic cancer can be genetically targeted by exploiting somatic single base substitution mutations that occur as part of normal aging prior to transformation. These passenger mutations are targetable because ~10% of them form novel tumor-specific “NGG” protospacer adjacent motif (PAM) sites targetable by CRISPR-Cas9. We studied five patients with pancreatic cancer (pc) who underwent a rapid autopsy to determine areas of evolutionary conservation that were maintained throughout all metastases in each patient’s cancer. Using whole genome sequencing validated by high-depth capture sequencing, we found that 90% of somatic PAM targets were maintained between primary carcinomas and metastases. We identified regions of loss of heterozygosity (LOH) surrounding tumor suppressor genes and oncogenes in the primary tumor where PAMs were 100% conserved in metastases. These regions of truncal LOH represent genetic vulnerabilities in these carcinomas and a CRISPR-based gene therapy approach targeting PAMs in these regions may be a novel way to genetically target metastatic cancer. Using multitarget sgRNA which cut at a known number of sites in the human genome, we determined a relationship between the number of CRISPR-Cas9 cuts and growth inhibition in PC cells. We found that 8-10 target sites in non-coding regions were sufficient to induce >95% cancer cell death. Furthermore, only 2-3 targets were required to achieve a comparable level of cell death in the presence of a DNA double strand break inhibitor. Finally, using cocultures of PC cells transduced with sgRNA targeting multiple tumor specific PAMs, we demonstrate selective cell killing of three different PC cell lines. Importantly, deep sequencing of patient-matched normal lymphocytes lacking the tumor-specific PAMs treated with the same sgRNA array exhibited no editing at the targeted loci. This work establishes a bioinformatic platform for the discovery of tumor-specific CRISPR targets in the context of metastatic disease and demonstrates selective killing of cancer cells while sparing the patient’s normal cells. These data establish the proof of principle for a gene therapy approach targeting metastatic disease. Citation Format: Kirsten Bowland, Jiaying Lai, Selina Shiqing K. Teh, Alexis Bennett, Alyza Skaist, Yan Zhang, Elizabeth Thompson, Ralph H. Hruban, Nicholas J. Roberts, Rachel Karchin, Christine A. Iacobuzio-Donahue, James R. Eshleman. CRISPR-cas9 genetic targeting of metastatic pancreatic cancer [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 7243.

Abstract 1372: BTN1A1 regulates T cell-mediated cancer immunotherapy by interacting with Galectin-9, PD-1, and TIM3

Abstract Butyrophilin 1A1 (BTN1A1) is a novel immune checkpoint protein belonging to the butyrophilin family and is expressed on immune cells such as macrophages, B cells, or activated CD8 T cells and in human tumors. Our results indicate that BTN1A1 and PD-L1 expression are mutually exclusive in various human solid tumors. Furthermore, it was observed that BTN1A1 had a significantly higher detection level than PD-L1 in cancer patient samples. We have reported that BTN1A1 plays an immunomodulatory role in T cell activation and proliferation. BTN1A1 inhibited the proliferation of T cells that are activated by anti-CD3 and anti-CD28 antibodies in vitro. Overexpression of BTN1A1 in PC3 cells also inhibits T cell-mediated killing of cancer cells. BTN1A1 is a bona fide immune checkpoint inhibitor and has anti-tumor activity in a human immune setting. BTN1A1 represents a novel cancer immunotherapy target that goes beyond the low expression levels of PD-1/PD-L1 in tumors. BNT1A1 is an immune checkpoint and cell membrane protein that, together with its binding partners, serves as a starting point for signaling pathways. The BNT1A1 complex, which has various abilities by combining with a specific partner, plays a vital role as an immune checkpoint. In this study, we identified binding partners of BTN1A that regulate immune activity in a mutually interaction relationship with BTN1A1 in various ways. We identified binding partners for the extracellular domain of human BTN1A1 using cell microarrays from Retrogenix (Whaley Bridge, UK). Through this screening approach, we found that BTN1A1 binds to galectin-1 (Gal1), galectin-9 (Gal9), and neuropilin 2 (NRP2). These three putative binding partners could specifically bind to wild-type BTN1A1 but not to this protein's unglycosylated (2NQ) form. Of these three targets, immunoprecipitation and Biacore binding assays revealed that Gal9 exhibited the greatest affinity for human BTN1A1. Since Gal9 is a known PD-1 and TIM3 binding protein, we predicted the potential formation of a BTN1A1/Gal9/PD-1 or BTN1A1/Gal9/TIM3 complex. Indeed, it reveals that immunoprecipitation and confocal microscopy assays performed using cells expressing Myc-tagged versions of these four proteins demonstrated the formation of BTN1A1/Gal9, PD-1/Gal9, TIM3/Gal9, BTN1A1/Gal9/TIM3, and BTN1A1/Gal9/PD-1 complexes. In T cell activation assay using these complexes, when present BTN1A1 alongside the complex inhibits activated T cells. As high Gal9 expression levels are correlated with poor prognosis in multiple cancers, our results highlight this BTN1A1-Gal9-PD-1 or BTN1A1-Gal9-TIM3 axis as a novel therapeutic target for immunotherapeutic drug development. Citation Format: Seung Hoon Lee, Young-Seung Kim, Chunai Wu, Andrew H Park, Stephen S. Yoo. BTN1A1 regulates T cell-mediated cancer immunotherapy by interacting with Galectin-9, PD-1, and TIM3 [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 1372.

Abstract 4045: Dependence of human immune cell type, and impact of IL-7R or TLR1/2 agonism, upon trastuzumab-mediated ADCC

Abstract Targeting of tumors over-expressing HER2 using trastuzumab provides clinical benefit for patients by inhibiting HER2 signalling and enhancing immune responses against the tumor by antibody-dependent cell-mediated cytotoxicity (ADCC). Cytokines such as IL-7 augment cytotoxic anti-viral responses through up-regulation of FasL, whereas TLR1/2 agonists enhance T cell cytotoxic responses but may also promote tumor cell survival. We therefore investigated the ability of IL-7R or TLR1/2 agonism to enhance trastuzumab-mediated ADCC. We first determined the contribution of various human immune cell subsets (e.g. monocytes, T cells, NK cells) to deliver ADCC of human tumor cells using a live high-content imaging assay in both 2D and 3D formats. Our results demonstrate that trastuzumab evoked immune cell dependent, concentration-dependent killing of tumor cells that exhibited some differential sensitivity dependent upon the cell culture format. We then tested trastuzumab-mediated killing in the absence or presence of IL-7R or TLR1/2 agonism, and noted evident donor and immune cell dependent modulation of the cytotoxic response. Modulation of this cytotoxic response was associated with differential immune cell marker expression when analysed by flow cytometry. Our findings provide mechanistic insight into trastuzumab-mediated ADCC and highlight how cytokine receptor and TLR pathways may modulate this response. Citation Format: Mark Bryant, Gokhan Tut, Neale Harrison, Emma Welsh, Ines Morano, Arshpreet Kaur, Ashley Pegg, Hujo Chan, Zhi Li, Jamie Cowley, Catherine Brady, John Gordon, Nicholas Barnes, Omar Qureshi. Dependence of human immune cell type, and impact of IL-7R or TLR1/2 agonism, upon trastuzumab-mediated ADCC [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 4045.

Abstract 6582: Preclinical characterization of IPH45, a novel topoisomerase I inhibitor ADC targeting Nectin-4 for the treatment of Nectin-4 expressing tumors

Abstract Background: Nectin-4 is a cell membrane adhesion protein overexpressed in several solid tumors, including urothelial, breast, lung, ovarian, and pancreatic cancers, with limited expression in normal tissues, making it an ideal target for antibody-drug conjugates (ADC). Enfortumab Vedotin (EV, PADCEV®) is an ADC targeting Nectin-4 with a monomethyl auristatin E (MMAE) payload approved for the treatment of patients with urothelial carcinoma (UC), but with limited clinical activity reported beyond UC. In addition, EV causes peripheral neuropathy and skin toxicity, leading to treatment discontinuation. To overcome these limitations and the mechanism of resistance to EV, IPH45, a novel topoisomerase I inhibitor ADC targeting Nectin-4 with an improved therapeutic index, was developed. Methods: In vitro studies were performed to investigate internalization, tumor cell killing and bystander effect, antibody-dependent cellular cytotoxicity (ADCC) and complement activation. In vivo efficacy studies were performed on cell line-derived xenografts (CDX) of triple negative breast cancer, patient-derived xenografts (PDX) of urothelial carcinoma and syngeneic tumor models expressing human Nectin-4. IPH45 efficacy was compared to EV. Toxicology studies to determine the dose range were conducted in rat and non-human primates (NHP). Results: IPH45 consists of a humanized IgG1 targeting a unique epitope in human Nectin-4, non-overlapping with EV, a cleavable linker, and a topoisomerase I inhibitor with a high drug-to-antibody ratio (DAR). In vitro, IPH45 is internalized upon binding to its target and induces direct killing of Nectin-4 expressing tumor cells as well as bystander killing of Nectin-4 non-expressing tumor cells in mixed culture. IPH45 mediates ADCC and complement-mediated killing. IPH45 demonstrates activity in CDX and PDX models with similar effective dose as EV. Moreover, IPH45 shows anti-tumor efficacy in vitro and in vivo in primary and secondary EV resistant models. In dose-range finding toxicology studies in rats and NHP, IPH45, unlike EV, does not elicit skin toxicity. IPH45 remains well tolerated up to the highest dose tested, suggesting a potentially larger therapeutic index than MMAE-based ADCs. Pharmacokinetic analyses in mice, rats, and NHP show minimal release of free toxin in the serum and half-life compatible with Q2W or less frequent dosing schedules in clinic. Conclusion: IPH45 is a topoisomerase I ADC targeting Nectin-4 with the potential for larger therapeutic index than EV, improved safety and dosing regimen, and ability to overcome primary and secondary resistance to EV or other Nectin-4 ADC in development. IPH45 is progressing to the clinic where the translatability of this unique profile into improved patient outcomes will be assessed across indications. Citation Format: Romain Remark, Cécile Bonnafous, Laura Chiossone, Caroline Soulas, Cyril Perrier, Guillaume Habif, Sivan Bokobza, Aurélie Maguer, Rachel Courtois, Julie Lopez, Grégory Fenaux, Olivier Benac, Barbara Carrette, Robin Letay-Drouet, Raja Bonifay, Séverine Augier, Léa Simon, Benjamin Rossi, Ariane Morel, Agnès Represa, Nicola Beltraminelli, Yannis Morel, Carine Paturel, Eric Vivier. Preclinical characterization of IPH45, a novel topoisomerase I inhibitor ADC targeting Nectin-4 for the treatment of Nectin-4 expressing tumors [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 6582.