Significant Tumor Growth Inhibition Research Articles

Abstract 1374: Targeting CD47/SIRPɑ axis in urologic cancer triggers enhanced phagocytosis of tumor cell and induces tumor growth inhibition

Abstract Signal regulatory protein-α (SIRPα; CD172a or SHPS-1) is a transmembrane molecule that highly expressed on myeloid population. Binding of CD47 (integrin-associated protein, IAP) to SIRPα inhibits phagocytosis in macrophages, which acts as a mechanism of maintaining homeostasis. Tumor cells however, often time upregulate CD47 to evade immune response. Using publicly available dataset, we found that human prostate cancer cells upregulate expression of both CD47 and calreticulin, a “eat me” signal when engaged with Low density lipoprotein receptor-related protein 1 (LRP1). In addition, macrophages, monocytes and dendritic cells in human prostate cancer do have relatively high level of SIRPɑ and LRP1 expression. This finding provides the rationale of targeting CD47/SIRPɑ axis in prostate cancer to shift the balance between pro-phagocytosis and anti-phagocytosis signaling. We then moved to RM1 and B6Cap, two syngeneic prostate cancer models in immunocompetent mice. Significant tumor growth inhibition was seen in both models with anti SIRPɑ blocking antibody. Furthermore, we observed in vitro that CD47 or SIRPɑ blockage led to enhanced PC3 cell line phagocytosis by human monocyte derived macrophages (HMDMs). Same finding was found using mouse bone marrow derived macrophages (BMDMs). We then utilized ovalbumin expressing MB49 bladder cancer cell line and cocultured those with BMDMs. CD8+ T cell from OT1 mice exhibited higher expression of activation makers when cocultured BMDMs treated by either anti CD47 or SIRPɑ antibody, indicating that enhanced phagocytosis subsequently increases antigen cross presentation in macrophages. In summary, we identified that CD47 is overexpressed in human prostate cancer; blocking CD47/SIRPɑ did inhibit tumor growth through enhanced phagocytosis and antigen presentation. Citation Format: Fan Shen, Monali Praharaj, Alex J. Lee, Thomas R. Nirschl, Xiaoxu Wang. Targeting CD47/SIRPɑ axis in urologic cancer triggers enhanced phagocytosis of tumor cell and induces tumor growth inhibition [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 1374.

Abstract 5936: A novel class of orally bioavailable small molecules induces potent and sustained tumor growth inhibition and T cell infiltration in various solid tumor mouse models

Abstract The introduction of targeted immunomodulating agents has transformed cancer treatment over the last decade by demonstrating unprecedented efficacy in patients who respond. However, limited clinical response rates as well as adverse events underline the need to identify additional novel modalities in cancer immunotherapy. Here we report on the discovery of a novel class of low molecular weight compounds for oral application that selectively enhance tumor-reactive T cell cytotoxicity. Hit-to-lead development of compound hit series A was performed based on medicinal chemistry to investigate structure-activity-relations. A-306, a representative of the A compound class, induced increased T cell proliferation, elevated levels of the activation markers CD25 and CD69 as well as enhanced secretion of IFN-γ, IL-2 and TNF-α upon anti-CD3/CD28 stimulation. A-306 treatment without T cell receptor ligation had no effect on T cell activation, suggesting selective activation potential only in the context of antigen encounter. Furthermore, A-306 strengthened T-cell mediated killing of M21 melanoma cells and enhanced T cell function in response to viral antigens by showing a Th1 signature. Medicinal chemistry efforts resulted in front runner compounds A-481 and A-687 that show a similar profile and potencies down to nanomolar level. In a murine B16-SIY melanoma and EO771 breast cancer model oral single-agent administration with front runner compounds was well tolerated, showed good bioavailability in lymphoid organs and plasma and resulted in significant tumor growth inhibition beyond the end of treatment (D21). T cells from tumor draining lymph nodes of long-term surviving mice in both cancer models showed a distinct activation pattern indicative of anti-tumor immunity. Furthermore, oral application of A-481 in combination with intra peritoneal administration of anti-PD1 antibodies eradicated B16-SIY melanoma cells in a synergistic manner. Taken together, we report on the identification of a novel class of small molecules possessing high potential for selective anti-tumor activation of the immune system upon oral administration. Front runner compounds A-481 and A-687, which significantly inhibit tumor growth in a B16-SIY melanoma and EO771 breast cancer mouse model, lead to prolonged survival beyond the end of treatment and display a good safety profile. The final candidate compound will undergo testing in toxicity studies and enter a first-in-human trial in selected solid tumors in 2025. Citation Format: Bianca Gapp, Gunther Zischinsky, Maria Urban, Nora Birnbacher, Alice Schwarzböck, Sabine Grünaug, Tommaso Gastaldi, Anton Stütz, Peter Nussbaumer, Stefan Stranner, Julia Buchberger, Andreas Birbach, Daniela Schögl, Mario Kuttke, Alexander Dohnal, Romana Gugenberger. A novel class of orally bioavailable small molecules induces potent and sustained tumor growth inhibition and T cell infiltration in various solid tumor mouse 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 5936.

Abstract 7268: The SOS1 inhibitor MRTX0902 demonstrates activity across cancer models with mutations in proximal components of the RAS-MAPK pathway

Abstract Genetic alterations in the RAS-MAPK pathway are one of the most frequent causes of human cancers. While targeted therapies are approved for patients harboring mutations in KRAS G12C in advanced or metastatic non-small cell lung cancer, there remains a need for an effective therapy for cancers characterized by additional RAS-MAPK pathway mutations across cancer types. Previous studies have shown that genetic or pharmacological inhibition of Son of Sevenless homolog 1 (SOS1) demonstrates antiproliferative activity in cancer cells addicted to KRAS signaling, including cell lines with oncogenic mutations in KRAS, SOS1, PTPN11, or EGFR or a loss-of-function mutation in NF1. These genetic alterations each function to increase SOS1-mediated GTP-loading of KRAS and increase signaling flux through the MAPK pathway. Inhibition of SOS1 by MRTX0902 is anticipated to shift the tumor cell equilibrium of KRAS towards the inactive GDP-bound KRAS, leading to MAPK pathway inhibition. MRTX0902 is a selective inhibitor of SOS1 under evaluation in clinical trials for the treatment of advanced, unresectable, or metastatic cancers with mutations in the KRAS-MAPK pathway. In the present studies, we have shown that MRTX0902 demonstrates single-agent anti-proliferative activity and modulates ERK1/2 phosphorylation (pERK) across a panel of human tumor cell lines harboring oncogenic mutations in SOS1, PTPN11, BRAF (class III) and NF1. Furthermore, oral administration of MRTX0902 as a monotherapy in preclinical human tumor cell-derived xenograft models harboring these oncogenic mutations results in significant tumor growth inhibition. Additionally, combination with the RAF/MEK clamp avutometinib demonstrated greater antitumor activity versus either monotherapy treatment. These data support the clinical utility of MRTX0902 as a single agent or combination partner of avutometinib for the treatment of human cancers harboring oncogenic mutations implicated in dysregulation of RAS-dependent signaling including SOS1, PTPN11, NF1, and BRAF (class III). Citation Format: Niranjan Sudhakar, Larry Yan, Fadia Qiryaqos, Jade Laguer, David Briere, Allan Hebbert, Andrew Calinisan, Silvia Coma, Jonathan Pachter, James G. Christensen, Peter Olson, Shilpi Khare. The SOS1 inhibitor MRTX0902 demonstrates activity across cancer models with mutations in proximal components of the RAS-MAPK pathway [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 7268.

Abstract 682: Development of novel eIF4E inhibitors to potently and selectively suppress tumor growth across multiple indications

Abstract Despite considerable progress in treating cancer, drug resistance remains the primary hurdle to achieving cures in patients. Tumors often develop resistance through reactivation of the drug-targeted pathway, or activation of alternative parallel pathways, thereby maintaining the original downstream signaling effects. One of the furthest downstream effectors and critical nodes for many oncogenic signaling pathways is eukaryotic translation initiation factor 4E (eIF4E); the main regulator and rate limiting factor for protein synthesis. eIF4E is reactivated by many resistance mechanisms to promote translation of multiple pro-oncogenic factors including Cyclin D1/3, making it an attractive target to potentiate the anti-cancer activity of targeted therapies and to overcome drug resistance. Here, we present the development of novel, potent, and selective eIF4E inhibitors for use in both treatment-naïve and resistance settings across multiple tumor indications. To capitalize on the potential of targeting eIF4E, we developed a series of compounds with unique properties that maintain anti-tumor efficacy while minimizing toxicity. Our novel, selective, and potent oral eIF4E inhibitors (RBX-eIF4Ei) elicit a reversible, dose-dependent cell cycle arrest. Unlike targeting eIF4A, eIF4E inhibition selectively regulates translation of cancer-dependent pathway proteins instead of global protein synthesis, thus reducing on-target toxicity and increasing tolerability. Cellular profiling demonstrates RBX-eIF4Ei are highly selective, nanomolar inhibitors across many tumor types including, NSCLC, CRC, breast, and melanoma. Additionally, RBX-eIF4Ei demonstrate consistent efficacy across both sensitive and resistant cell lines, including intrinsic and acquired resistance models. Combining RBX-eIF4Ei with standard of care targeted therapies produces additive responses in both settings, suggesting its potential anti-neoplastic benefits post progression. In vivo, daily oral monotherapy treatment with RBX-EIF4Ei causes significant tumor growth inhibition across a variety of indications including BRAFmut CRC, BRAFmut melanoma and ER+ breast cancer, with minimal signs of toxicity. Intratumoral concentration of RBX-eIF4Ei correlate with significant tumor cell growth inhibition, as well as reductions in eIF4E target proteins, ODC1 and Cyclin D1. Combination studies with standard of care in both the treatment naïve and resistant settings are ongoing. Collectively, these data support the addition of RBX-eIF4Ei to standard of care in both the naïve and treatment resistance settings across a variety of indications including NSCLC, breast, CRC, and melanoma. IND enabling studies are planned, marking a significant step toward advancing these promising eIF4E inhibitors into clinical development. Citation Format: Matthew B. Friedersdorf, Devon R. Blake, Sarah E. Thompson, Roheeth Pavana, Ramamurty V. Changalvala, Andrew S. Truong, Krista Marran, Abha Bias, Jessica A. Sorrentino. Development of novel eIF4E inhibitors to potently and selectively suppress tumor growth across multiple indications [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 682.

Abstract 6020: GPC3-targeted radiopharmaceutical therapy for neuroendocrine prostate cancer

Abstract Introduction: Glypican-3 (GPC3) is a membrane-anchored oncofetal protein with minimal expression in normal tissues. Besides hepatocellular carcinoma, upregulation of GPC3 protein has been observed in a significant subset of treatment-emergent neuroendocrine prostate cancer (NEPC), which accounts for to 30% of prostate cancer cases refractory to anti-androgen and other therapies. The differential expression of GPC3 between NEPC cells and normal tissues provides a theranostic opportunity for targeted radiopharmaceutical therapy (RPT). Methods: The novel RPT agent RYZ-GPC3 comprises a small macrocyclic peptide binder with high affinity to GPC3 linked with a tetraxetan moiety capable of chelating a variety of radioisotopes. The expression of GPC3 in NEPC cells was assessed by flow cytometry and immunohistochemistry (IHC). The affinity of peptide binders to GPC3 was determined by surface plasma resonance (SPR) and radioligand binding assays. In vivo biodistribution of [177Lu]Lu-RYZ-GPC3 and anti-tumor therapy with [177Lu]Lu-RYZ-GPC3 or [225Ac]Ac-RYZ-GPC3 were performed in NEPC xenografts. Results: The novel agent is a highly potent and selective peptide binder to GPC3 of human, mouse and NHP origins, and is compatible with multiple radiometal isotopes. In vivo biodistribution study of [177Lu]Lu-RYZ-GPC3 in GPC3-positive NEPC xenografts showed sustained tumor uptake of 10.8, 12.6, 5.1, and 2.2 %ID/g at 2, 24, 72 and 168 hours post dose, respectively, with fast renal clearance. Minimal or no uptake was observed in other normal tissues. A single injection of [225Ac]Ac-RYZ-GPC3 (11.1 kBq) resulted in significant tumor growth inhibition (TGI 109%) with durable regression and prolonged survival. All treatments were well tolerated. Conclusion: Preclinical in vitro and in vivo data demonstrated the potential of the novel binder as a theranostic agent for the treatment of patients with GPC3+ NEPC. Citation Format: Renee Clift, Fanching Lin, Katrina Salvador, Matt Guest, Daniel Kim, Guangzhou Han, Gary Li. GPC3-targeted radiopharmaceutical therapy for neuroendocrine prostate 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 6020.

Abstract 3230: Discovery of selective BRM (SMARCA2) ATPase inhibitors for the treatment of BRG1 (SMARCA4) mutant cancers

Abstract BRM (SMARCA2) and BRG1 (SMARCA4) are highly homologous ATPases that are members of the BAF (also known as the mSWI/SNF) chromatin remodeling complex. BRM and BRG1 are mutually exclusive enzymatic subunits of BAF complexes, and functional genomic screens have shown a synthetic lethal relationship between the two genes. BRG1 is frequently mutated in cancer, including in approximately 10% of non-small cell lung carcinomas. Selective inhibition of BRM is a mechanism by which BRG1-mutated cancer cell growth would be affected by losing BRM function, while normal tissues should be spared as they still express functional BRG1. Given that the ATPase domains of BRM and BRG1 are 92% identical, the identification of selective enzymatic inhibitors of BRM has been challenging. Here, we report the discovery of novel, highly potent compounds that selectively inhibit BRM over BRG1 as seen in cell-based transcription and proliferation assays, that also possess excellent oral pharmacokinetics. Our lead compounds inhibit BRM in a cell-based reporter assay with an unbound IC50 of 1 nM and are greater than 20-fold selective over BRG1. They are also selective against other helicases and do not show any significant activity in off-target screening panels. Dosing of mice carrying BRG1-mutant xenografts causes target gene modulation that is correlated with compound exposure. Treatment of A549 and RERF-LC-AI xenografts with lead compounds led to tumor growth inhibition of 87% and 96%, respectively, at well-tolerated doses, and significant tumor growth inhibition was also achieved in multiple other BRG1-mutant models. The results suggest that our compounds have first-in-class potential as potent and selective BRM ATPase inhibitors for the treatment of BRG1-mutated cancers, and we are planning to file an IND in 2024. Citation Format: Janice Y. Lee, Nathan Brooks, Brandon Antonakos, Bryan Perria, Candace Langan, Bonita D. Jones, Robert Stephen Flack, Zhifang Li, David Terry, Ross Wallace, Robert Bondi, Gereint Sis, Ronee Baracani, Maralee McVean, Gabrielle Kolakowski, Dayo Osimboni, Kevin Wilson. Discovery of selective BRM (SMARCA2) ATPase inhibitors for the treatment of BRG1 (SMARCA4) mutant cancers [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 3230.

Abstract 4378: Identification of novel TXNIP-dependent antitumor pathways in breast cancer

Abstract Thioredoxin-interacting protein (TXNIP) plays a critical role in glucose metabolism and redox signaling. TXNIP has recently emerged as a potent tumor suppressor in various cancer models. In previous studies, we found TXNIP was activated by UNC0642, an inhibitor of histone methyltransferase, in MDA-MB-231 breast cancer cells. TXNIP activation was coupled with significant suppression of cell proliferation and tumor growth. In contrast, TXNIP knockdown increased MDA-MB-231 cell proliferation and in tumor growth and metastasis in vivo. TXNIP-reconstitution in TXNIP-deficient HCC1954 cells reduced cell proliferation and migration coupled with increased reactive oxygen species production. TXNIP-reconstitution also significantly decreased mitochondrial respiration, mitochondrial membrane potential and glycolysis in HCC1954 cells. To understand the mechanisms underlying TXNIP’s antitumor activity, we performed co-immunoprecipitation and proteomic analyses to uncover TXNIP-interacting proteins. We identified calpastatin (CAST) as a novel TXNIP-interacting protein in breast cancer cells. CAST is an endogenous inhibitor of calpains, a family of calcium-activated cysteine proteases. Intriguingly, CAST association with TXNIP was readily detectable in TXNIP-low, but not in TXNIP-high breast cancer cells. The disassociation of CAST from TXNIP in TXNIP-high cells might allow CAST to inhibit calpain activity to augment TXNIP’s antitumor function. Through RNAseq analysis, we identified a positive correlation between TXNIP expression and IL-24 activation in various breast cancer cells, which were also confirmed by western blotting. IL-24 has emerged as an important cancer therapy target because of its role in promoting cancer-specific apoptosis. Our data also demonstrated that TXNIP upregulated the level of IL-24 and downregulated STAT-3. Moreover, TXNIP exerts multifaceted effects on BC development through the IL24-STAT3 signaling axis, deepening our understanding of its complex role in the disease. Taken together, these studies identified novel TNXIP-dependent pathways and their potential new mechanisms in breast cancer pathogenesis with significant clinical implications. Citation Format: Jasvinder Singh, Bindeshwar Sah, Robert Clarke, Liang Liu. Identification of novel TXNIP-dependent antitumor pathways in breast 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 4378.

Abstract 7300: Synergistic inhibition of prostate cancer growth by the combination of xanthohumol and ursolic acid

Abstract Within the United States, prostate cancer (PCa) is the most commonly diagnosed non-cutaneous cancer, and approximately 1 in 8 men will receive a diagnosis in their lifetime. As the second leading cause of cancer deaths in American men, about 1 in 41 will die because of prostate cancer. The World Health Organization has suggested that approximately one-third of all cancer deaths are preventable, and one of the suggested means of prevention is through the increased consumption of fruits and vegetables. Fruits and vegetables contain natural compounds known as phytochemicals which possess biological activity including some anti-cancer effects. By adapting the ATP-bioluminescence assay for cell viability, our laboratory screened a natural compound library to find combinations of these compounds that may synergistically inhibit PCa cell viability. One of the combinations to emerge from this screening process was xanthohumol (XAN) and ursolic acid (UA). We examined the ability of the combination to inhibit tumor growth in a mouse HMVP2 PCa allograft tumor model. Mice were fed diets supplemented with either XAN (0.2%) or UA (0.2%) alone or the combination. Mice on the combination diet showed a significant inhibition of HMVP2 PCa tumor growth compared to mice on the single-agent diets. In addition, in vitro studies were performed to support the allograft tumor study and to further examine the mechanism of action of the combination. A cell survival assay utilizing six different PCa cell lines indicated that the combination of XAN and UA synergistically inhibited the survival of all cell lines as calculated by the Bliss index. Mechanistic studies performed in PCa cells indicate that the combination of XAN and UA inhibits oncogenic signaling better than either agent alone. Additionally, unbiased metabolomics revealed that the tumors from mice fed the combination diet had significantly less S-adenosyl-L-methionine compared to all other groups. Overall, 13 metabolic pathways were significantly different in the tumors from mice fed the combination diet compared to all other groups. The current data suggest that using a combination of XAN and UA may be a valuable chemopreventive strategy for PCa in humans. Funding: This work was supported by NIH Grant CA228404. Citation Format: Rachel Clark, Achinto Saha, Chelsea A. Friedman, Ruggiero Gorgoglione, Stefano Tiziani, John DiGiovanni. Synergistic inhibition of prostate cancer growth by the combination of xanthohumol and ursolic acid [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 7300.

Abstract 5960: Targeting CDK8: A translatable therapeutic approach for fusion-positive aRMS

Abstract Alveolar rhabdomyosarcoma (aRMS), characterized by poor overall survival and limited advancements in therapy over the past four decades, poses a great challenge in childhood cancer treatment. More than 60% of high-risk aRMS is driven by the oncofusion protein PAX3-FOXO1. The direct targeting of transcription factor fusions, however, is quite difficult. Given that PAX3-FOXO1 is reported to drive disease by controlling transcriptional programs to maintain an undifferentiated myoblastic state, an alternative approach would be to target the transcriptional machinery recruited by the fusion. To identify potential novel targets in aRMS, we utilized the Broad Institute’s Cancer Dependency Map dataset, a collection of genome-wide CRISPR-Cas9 screens performed in over 1000 cancer cell line models. We focused on druggable dependencies that are selective to fusion-positive aRMS and intersected this data with PAX3-FOXO1-associated transcriptional complexes. Among these candidates, we identified CDK8 as a top selective dependency. Importantly, other components of the CDK8 kinase module in the mediator complex, such as CCNC, also scored as a strong selective dependency in fusion-positive aRMS. CDK8 expression is notably elevated in aRMS tumors compared to other pediatric tumors, and aRMS cell lines exhibit significantly higher CDK8 protein levels than non-transformed primary skeletal muscle cells. We next validated these in silico results through the application of shRNA knockdown, CRISPR knockout, and the use of CDK8 kinase inhibitory small molecules, including BI-1347, SEL-120-34A, and JH-XII-178, which demonstrated on-target activity as assessed by STAT1Ser727 phosphorylation. Both genetic loss of CDK8 function and kinase inhibition impaired aRMS cell line growth in vitro. In vivo studies demonstrated a significant inhibition of xenograft tumor growth with both doxycycline inducible CDK8-directed shRNAs and with pharmacologic inhibition of CDK8 with SEL120-34A treatment. To understand the mechanisms by which CDK8 inhibition impairs aRMS growth, we evaluated the transcriptional consequences of CDK8 inhibition by RNA-sequencing in aRMS, as well as the chromatin accessibility by ATAC-sequencing. We discovered that loss of CDK8 led to gain of chromatin accessibility and the upregulation of hallmark genes involved in myogenesis, such as MYH3, MYOG, MEF2C, and MYBPH, as well as alteration of PAX3-FOXO1 gene expression programs. We next validated this differentiation phenotype both in vitro through detection of increased myogenin staining by immunofluorescence and in vivo by visualization of myofibrils in the xenograft tumors and increased myoglobin quantified by qRT-PCR after CDK8 inhibition. In conclusion, this work identifies CDK8 as a novel and readily translatable therapeutic target in fusion-positive aRMS laying a robust foundation for further mechanistic and preclinical studies. Citation Format: Susu Zhang, Clare Malone, Brian Guedes, Kathleen Engel, Marissa Just, Kenneth Ross, Assil Fahs, Giulia Digiovanni, Diyana Granum, Rex Bentley, Leen Barbar, Christian Cerda-Smith, Elizabeth Mendes, Ozgun Erdogan, Alexander Kovach, Kristianne Oristian, Seth Zimmerman, Jack F. Shern, Kris Wood, Chris Counter, Corinne M. Linardic, Kimberly Stegmaier. Targeting CDK8: A translatable therapeutic approach for fusion-positive aRMS [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 5960.

Abstract 2731: CCR5-001, a novel drug Fc-conjugate (DFC) targeting CCR5, demonstrates potent efficacy in a colorectal cancer mouse model

Abstract Background The approval of immune checkpoint inhibitors (ICI) such as PD-(L)1 inhibitors has revolutionized cancer therapy and established a role for immune effector cells, most notably CD8+ T cells, in tumor control and destruction. While anti-PD-(L)1 therapy has demonstrated durable responses, only a small subset of patients benefit and respond to therapy. CCR5 is expressed on multiple immune cells (e.g. myeloid-derived suppressor cells) and CCR5-dependent migration of these cells contribute to an immune-suppressive tumor microenvironment (TME) thereby limiting response to ICI therapy. In addition, expression of CCR5 on cancer cells has been linked to increased metastasis and resistance to ICI therapy. Upregulation of CCL5/CCR5 has been associated with poor outcomes in multiple solid tumor indications, including colorectal cancer (CRC). Therefore, targeting CCR5 has the potential to increase response rates to ICI therapy and improve outcomes. Herein, we describe a first-in-class CCR5 targeting DFC, CCR5-001, a multivalent conjugate of a potent, small molecule CCR5 antagonist conjugated to an immune-silent proprietary human IgG1 Fc. This CCR5 targeting DFC has the potential to improve responses to ICI therapy by preventing pro-tumorigenic reprogramming of the TME induced by CCL5/CCR5 expressing tumor and myeloid cells. Methods Binding of CCR5-001 to hCCR5 was measured by surface plasmon resonance (SPR) and to CCR5+ PathHunter cells (DiscoverX) by flow cytometry. Functional activity was determined in CCR5+ PathHunter β-arrestin assay with CCL3 to induce CCR5 signaling according to manufacturer’s instructions. Efficacy was determined in an immune-competent syngeneic mouse model using the CRC cell line, MC38. CCR5-001 was dosed at 20 mg/kg twice per week for two weeks. Tumor volumes were recorded and statistical analysis was conducted by t-test (Mann-Whitney) or two-way ANOVA in Prism. Results CCR5-001 displayed a KD of 4.2 nM to immobilized hCCR5 by SPR and IC50 of 0.63-0.98 nM for binding to engineered CCR5+ PathHunter cells. This high affinity binding translated to potent functional inhibition of CCL3-induced CCR5 signaling with an IC50 of 12.7 nM in CCR5+ cell-based assay. CCR5-001 demonstrated potent, statistically significant (p = 0.0052) tumor growth inhibition of 76% by day 13 in a syngeneic mouse model. Conclusions CCR5-001 demonstrated potent CCR5 binding and functional inhibition of CCR5 signaling in cell-based assays. The in vitro activity translated to robust efficacy as a monotherapy in a syngeneic mouse model. Based on these results and other emerging data, CCR5-001 represents an exciting new avenue for targeting CCR5 with DFCs in solid cancers where the pathology is driven by the CCR5/CCL5 axis. Citation Format: Simon Döhrmann, James Levin, Nicholas Dedeic, Amanda Almaguer, Doug Zuill, Elizabeth Abelovski, Jeffrey B. Locke, Joanne Fortier, Maria Hernandez, Qiping Zhao, Karin Amundson, Madison Moniz, Hongyuan Chen, Dhanya Panickar, Thanh Lam, Grayson Hough, Thomas P. Brady, Allen Borchardt, Jason N. Cole, Leslie W. Tari. CCR5-001, a novel drug Fc-conjugate (DFC) targeting CCR5, demonstrates potent efficacy in a colorectal cancer mouse model [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 2731.

Abstract 1900: TORL-3-600, a novel antibody drug conjugate directed against cadherin 17 (CDH17), has preclinical efficacy in colorectal, gastric, and pancreatic cancer

Abstract Cadherin 17 (CDH17) is a cell-to-cell adhesion protein that is a member of the cadherin superfamily. In normal tissues, expression of this single pass transmembrane protein is restricted to the lateral surfaces of intestinal and pancreatic ductal epithelial cells. However, in cancer, CDH17 is frequently overexpressed in tumors of the colon, stomach, and pancreas. The selective expression of this cell surface protein in these hard-to-treat cancer makes it an attractive target for the development of antibody-based therapeutics. Here, we describe the preclinical development of TORL-3-600, a novel CDH17-targeting antibody drug conjugate (ADC). CDH17 specific monoclonal antibodies were generated using traditional hybridoma technology and splenocytes isolated from mice immunized with cocktails of NIH3T3 cells overexpressing full length hCHD17 plus purified mammalian expressed hCDH17 extracellular domain protein (aa 23-787). Selective mAb binding was confirmed by flow cytometry and mAb internalization rate was assessed by immunofluorescence (IF). TORL-3-600 was generated from a fully humanized CDH17 mAb by MMAE conjugation with a cleavable linker. Cell membrane staining of CDH17 in patient tumor microarrays (TMAs), cell line (CDX) and patient derived xenografts (PDX) was evaluated by IHC assay. Selective binding of the TORL-3-600 to CDH17 was confirmed in human cancer cell lines and cells engineered to overexpress CDH17. Binding of TORL-3-600 to cell surface CDH17 induced Internalization and translocation to the lysosome of the protein-ADC complex for release of the MMAE payload. Treatment with TORL-3-600 induced significant regressions and tumor growth inhibition (TGI) in four CDH17-positive (CDH17+) human colorectal cancer (CRC) CDXs (103.6 - 140.4% TGI) and three CDH17+ CRC PDXs (63.3 - 102.2% TGI). Responses in these models were sustained for up to nine-weeks following cessation of treatment. Sustained inhibition of xenograft tumor progression was also observed in a cell line model of CDH17+ pancreatic cancer (85.8% TGI). In contrast, greatly reduced responses (37.3 - 58.2% TGI) to TORL-3-600 were observed in the CDH17- human colon cancer CDX and PDX models. Each of the doses tested in this study were well tolerated in mice with no dose-limiting toxicities observed. Analyses of large human patient TMAs by CDH17 IHC assay demonstrated detectable expression of CDH17 in 90.1% (173/193) of CRC, 51.8% (86/166) of gastric and 20.4% (69/331) of pancreatic cancers. These numbers suggest that an ADC directed against CDH17 could provide benefit to a significant number of patients diagnosed with these cancers. These data support the clinical development of TORL-3-600 for the treatment of CDH17+ cancers. TORL-3-600 has completed IND enabling toxicity studies with acceptable PK and toxicity profiles and is now in phase 1 clinical testing (NCT05948826). Citation Format: Neil A. O'Brien, Martina SJ McDermott, Jun Zhang, Ming Lu, Ke Wei Gong, Benjamin Hoffstrom, Wei Ping Jia, Tong Luo, Athena M. Madrid, Min Liang, John A. Glaspy, Dennis J. Slamon. TORL-3-600, a novel antibody drug conjugate directed against cadherin 17 (CDH17), has preclinical efficacy in colorectal, gastric, and 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 1900.

Abstract 4072: Unleashing natural IL-18 activity using an anti-IL-18BP blocker antibody induces potent immune stimulation and anti-tumor effects

Abstract IL-18 is an inflammasome induced proinflammatory cytokine that augments T and NK cell activity and stimulates IFNγ production. The activity of IL-18 is naturally blocked by a high affinity endogenous binding protein (IL-18BP). IL-18BP is induced in the tumor microenvironment (TME) in response to IFNγ upregulation in a negative feedback mechanism. By evaluating 88 human tumor specimens and serum samples we were able to show that IL-18 is upregulated in the TME (median 11.2ng/gr) compared to serum samples (median 0.3ng/ml). Moreover, we showed that most of the IL-18 is bound by IL-18BP. IL-18BP-bound IL-18 levels were largely above the amount required for T cell activation in vitro (1.2ng/gr), implying that blocking IL-18BP has the potential to release IL-18 in tumors above the minimum range required for immune system stimulation. Next, to assess whether tumor endogenous IL-18 levels released by IL-18BP blockade are sufficient to provoke anti-tumor responses, COM503, a high affinity (<1pM) anti-IL-18BP Ab, was generated and examined in T and NK cell-based assays. In a co-culture assay of tumor cells with ex-vivo stimulated human tumor infiltrating CD8+ lymphocytes, COM503 was able to displace IL-18 from a pre-formed complex and enhance IFNγ (197%, p<0.01) and TNFα (84% p<0.01) secretion. Additionally, COM503 induced human NK cell activation as reflected by increased IFNγ secretion (26-fold, p<0.001). Finally, in human ex vivo dissociated tumor cells assay, COM503 mediated an increase in Granzyme B (25%), IFNγ (38%), TNFα (58%) and IL-12 (50%) production. In vivo, administration of an anti-mouse IL-18BP Ab resulted in potent anti-tumor responses and increased survival across multiple mouse tumor models. In orthotopic E0771 tumor model, anti-IL-18BP Ab induced significant tumor growth inhibition (91% TGI, p<0.0001), as well as pronounced TME-localized immune modulation. This modulation included an increase in CD8+ T cells expansion (108.5%, p=0.015) and activation, specifically in polyfunctional effector IFNγ+GrB+CD8+ T cells (259%, p=0.02) and IFNγ+TNFα+NK cells (77%, p=0.001). Similarly, anti-tumor effects were shown in MC38OVAdim model (58% TGI, p<0.001), accompanied by a robust TME-localized immune modulation including increased CD8+ T cells expansion (85%, p=0.009) and IFNγ secretion (76%, p=0.052). In contrast to immune modulation in the TME, no increase in inflammatory cytokines and lymphocyte numbers or activation state was observed in serum and spleen. Taken together, our data suggest that IL-18 is upregulated in the TME, mostly bound by IL-18BP, and could be exploited to induce pronounced TME-localized immune modulation. Anti-IL-18BP Ab approach has a leading edge in inhibiting tumor growth while avoiding peripheral toxicity associated with administration of a cytokine. COM503 is currently undergoing IND-enabling studies. Citation Format: Assaf Menachem, Zoya Alteber, Gady Cojocaru, Tal Fridman Kfir, Dan Blat, Olga Leiderman, Moran Galperin, Lital Sever, Nadav Cohen, Keren Cohen, Roy Zvi Granit, Sandra Vols, Masha Frenkel, Lior Faigenbloom, Liron Soffer, Karin Meyer, Keren Menachem, Hadas Galon Tilleman, Dina Morein, Itamar Borukhov, Amir Toporik, Michal Perpinial Shahor, Evgeny Tatirovsky, Pierre Ferre, Eran Ophir. Unleashing natural IL-18 activity using an anti-IL-18BP blocker antibody induces potent immune stimulation and anti-tumor effects [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 4072.

Abstract 7139: Anti-cancer effects of benzimidazole derivative BNZ-111 on paclitaxel-resistant ovarian cancer

Abstract Ovarian cancer, a leading cause of cancer-related deaths in women, remains a formidable challenge, especially in the context of platinum-resistant disease. This study investigated the potential of the benzimidazole derivative BNZ-111 as a novel treatment strategy for platinum-resistant ovarian cancer. With improved pharmacokinetic parameters, BNZ-111 effectively disrupts tubulin polymerization through hydrogen bonds and hydrophobic interactions. It demonstrated strong cytotoxicity in both chemo-sensitive and chemo-resistant epithelial ovarian cancer cell lines, inducing apoptosis and G2/M cell cycle arrest. In vivo experiments using orthotopic and patient-derived xenograft models showed significant tumor growth inhibition without apparent toxicity to vital organs. Unlike paclitaxel, BNZ-111 proved effective in paclitaxel-resistant cells, potentially by bypassing interaction with MDR1 and modulating β-3 tubulin expression to suppress microtubule dynamics. This study suggests that BNZ-111, with favorable drug-like properties, holds promise as a therapeutic option for platinum-resistant ovarian cancer, addressing a critical clinical need in gynecologic oncology Citation Format: Jeong-Won Lee, Kwangho Lee, Byumseok Koh, Yoo-Young Lee, Duk-Soo Bae. Anti-cancer effects of benzimidazole derivative BNZ-111 on paclitaxel-resistant ovarian 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 7139.

Abstract 6067: Identification of selective CBP degraders with robust preclinical PK, PD, efficacy and safety across solid tumor indications

Abstract CREB binding protein (CBP) and E1A binding protein (EP300) are paralog histone acetyltransferases involved in many cellular processes via their activity as transcription factor co-activators. Dysregulation of one or both proteins has been implicated in various cancer types, and functional genomic screens have revealed a bidirectional synthetic lethal relationship between these two paralogs in tumor cells. Due to the high homology between CBP and EP300, identifying selective chemical matter that selectively disrupts the activity of CBP has proven challenging. Small molecule inhibitors targeting the HAT or bromodomain of CBP/EP300 have been developed, however these agents exhibit hematopoietic toxicity resulting from dual inhibition, which limits their therapeutic window. Herein, we describe the PK, PD, and efficacy of selective, potent CBP degraders across various EP300-mutant cancer xenograft models. Our results show deep and sustained CBP degradation, leading to significant tumor growth inhibition in solid tumors. This anti-tumor activity was not associated with significant body weight loss or hematopoietic toxicity. Our CBP-selective protein degraders have the potential to be a first-in-class therapeutic option for patients with tumors harboring EP300 mutations. Citation Format: Darshan Sappal, Ammar Adam, Hafiz Ahmad, Benjamin Adams, Ketaki Adhikari, Wesley Austin, Breanna Bullock, Julie Di Bernardo, Thomas Dixon, Danette Daniels, Claudia Dominici, GiNell Elliot, Brian Ethell, Anais Gervais, Md Imran Hossain, David Huang, Dave Lahr, Mei Yun Lin, David Mayhew, Karolina Mizeracka, Solymar Negretti, Tyler Nguyen, Olga Prifti, Shawn Schiller, Brenna Sherbanee, David Terry, Nihan Ucisik, Elizabeth Wittenborn, Qianhe Zhou, Mark Zimmerman, Laura La Bonte. Identification of selective CBP degraders with robust preclinical PK, PD, efficacy and safety across solid tumor indications [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 6067.

Abstract 4503: Preclinical characterization of PRT7732: A highly potent, selective, and orally bioavailable targeted protein degrader of SMARCA2

Abstract SWI/SNF (BAF) complexes play an important role in controlling gene expression by remodeling chromatin. SMARCA2 (BRM) and SMARCA4 (BRG1) are the core catalytic subunits of the SWI/SNF complexes, containing an ATPase domain and a bromodomain. SMARCA4 protein expression is lost in some cancers due to loss-of-function (LOF) mutations and homozygous deletions, and SMARCA4-deleted cancer cells are highly dependent on its paralog gene SMARCA2 for their survival. Therefore, targeting SMARCA2 in SMARCA4-deficient cancers using selective SMARCA2 degraders induces synthetic lethality while sparing SMARCA4 wild type (WT) normal cells. We have recently identified a series of orally bioavailable SMARCA2 selective degraders that demonstrate robust efficacy in pre-clinical animal models with favorable pharmacokinetic properties and safety profiles. Our nomination candidate PRT7732 exhibits >1000x selectivity for SMARCA2 over SMARCA4 in cell-based assays, with DC50 values in cancer cell lines in the low nanomolar range. The PRT7732-induced SMARCA2 degradation was rescued by a proteasome inhibitor and neddylation inhibitor, indicating ubiquitin-proteasome dependent degradation. Furthermore, PRT7732 does not change levels of known CRBN ligand neo-substrates such as IKZF2/3, GSPT1 and SALL4. PRT7732 inhibits only SMARCA4-deficient cancer cell proliferation with IC50 values ranging from 5.0-50 nM, but not SMARCA4 WT cells in vitro. Oral administration of PRT7732 resulted in near-total degradation of SMARCA2 protein with complete selectivity over SMARCA4 protein in a SMARCA4 WT lung cancer model in mice, consistent with the SMARCA2 degradation kinetics-based pharmacodynamic prediction model. PRT7732 oral daily administration showed significant tumor growth inhibition of SMARCA4-deficient lung cancer xenograft models at well tolerated doses. The treated tumor tissues show robust SMARCA2 protein reduction for 24h post dosing. In summary, our orally bioavailable SMARCA2 degraders induce synthetic lethality in SMARCA4-deficient cancers in vitro and in vivo. Efforts to further evaluate these compounds in additional models and in combination with other agents are ongoing. Citation Format: Artem Shvartsbart, Koichi Ito, Joseph Rager, Michael Hulse, Anjana Agarwal, Komali Vykuntam, Jessica Burtell, Min Wang, Justin Kurian, Miles Cowart, Joy Cote, Nick Stahl, Monisha Sivakumar, Anthony Reichelderfer, Jack Carter, Alexander Grego, Andrew Moore, Neha Bhagwat, Ross Kuskovsky, Shanthi Ganesan, Stefan Ruepp, Tom Emm, Philip Pitis, Corey Basch, Klare Bersch, Yongchun Pan, Song Mei, Raul Leal, John Rose, Dani Roth, Chaoyi Xu, Ganfeng Cao, Kris Vaddi, Sang Hyun Lee, Sandy Geeganage, Andrew Combs, Peggy Scherle. Preclinical characterization of PRT7732: A highly potent, selective, and orally bioavailable targeted protein degrader of SMARCA2 [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 4503.

Abstract 5707: Preclinical evaluation of KRLS-017, a potent, highly selective and reversible CDK7 inhibitor with broad antitumor effect in preclinical models, in preparation for a Phase 1 clinical trial in advanced solid tumor malignancies

Abstract KRLS-017 is a potent, selective, and reversible inhibitor of Cyclin Dependent Kinase 7 (CDK7). Its molecular formula is C24H35N5O2Si and its molecular weight is 453.65 Daltons. KRLS-017 is being developed for the treatment of patients with advanced solid tumor malignancies. To differentiate KRLS-017 from other CDK7 inhibitors, we created a reversible inhibitor to allow for treatment schedule optimization and maximization of therapeutic index in clinic. High selectivity of KRLS-017 for CDK7 was confirmed using a panel of 313 recombinant human kinases. The IC50 of KRLS-017 against recombinant human CDK7 was determined to be 16 nM, and no other kinases in the panel showed IC50 values less than 300 nM. Antiproliferative activity of KRLS-017 was investigated in vitro using a broad panel of human tumor cell lines. KRLS-017 showed potent antiproliferative effect across a wide variety of both solid and hematologic tumor types, producing GI50 values <200 nM in 258/302 human tumorcell lines tested. Antitumor activity of KRLS-017 was investigated in vivo using multiple mouse xenograft tumormodels at dose levels ranging from 25 mg/kg to 200 mg/kg using both continuous (daily) andintermittent dosing schedules. Statistically significant tumor growth inhibition was seen at doselevels of 50 mg/kg and higher, with tumor regression observed at 100 mg/kg and 200 mg/kg. Better in vivo tolerability at efficacious doses was observed using intermittent dosing schedules in mouse xenograft models, which led to adoption of an intermittent schedule in the proposed first-in-human phase 1 trial. KRLS-017 is orally bioavailable in mice, rats, and dogs and plasma drug exposure increased in a proportional manner with dose. Comparing first dose and 28th dose in the dog, minimal plasma accumulation was observed, suggesting once daily dosing in humans would be initially tested. Repeat dose 28 day GLP toxicology studies in rat and dog showed adverse effects in highly proliferative bone marrow and gastrointestinal tissues which is consistent with the known mechanism of action for CDK7 and is considered to be monitorable and manageable in the setting of oncology. The clinical development plan for KRLS-017 includes an initial Phase 1 dose escalation study (KRLS-017-101) in patients with refractory solid tumor malignancies to assess pharmacokinetics/pharmacodynamics and to determine an optimal dose level and treatment schedule to test in expansion cohorts. Given the potential of CDK7 inhibitors in the treatment of hormone receptor positive breast cancer, combination work with other agents (such as selective estrogen receptor degraders) is on-going. Citation Format: Alison L. Hannah, Steve Ritland, Thomas Steele, Steven Smith, Ashwin Ram, BT Slingsby, Kapil Dhingra, James Chrisman, Rajesh Dua, Yasunori Tokunaga, Shigeyuki Kono, Yasuhiro Aga. Preclinical evaluation of KRLS-017, a potent, highly selective and reversible CDK7 inhibitor with broad antitumor effect in preclinical models, in preparation for a Phase 1 clinical trial in advanced solid tumor malignancies [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 5707.

Abstract 1872: A next generation treatment for Nectin-4 positive cancers - Preclinical characterization of LY4052031, an anti-Nectin-4 antibody, conjugated to a novel camptothecin payload

Abstract Nectin-4 is an immunoglobulin-like antigen overexpressed in a variety of cancers including bladder, breast, NSCLC, and gastric. Normal tissues including skin, salivary glands, bladder and esophagus express only low to medium levels of Nectin-4 making the protein an attractive target for cancer therapies. The approval of enfortumab vedotin-ejfv, an anti-Nectin-4 based antibody-drug conjugate (ADC) with a microtubule inhibitor payload, either as a single agent or in combination with pembrolizumab has been a significant advancement in the treatment of metastatic urothelial cancer. We have developed a novel anti-Nectin-4 ADC with a novel topoisomerase I (TOPO 1) inhibitor drug payload. Topoisomerase inhibitor payload-based ADCs offer potential advantages compared to microtubule payload-based ADCs including a different toxicity profile and the differentiated susceptibility to resistance mechanisms, such as P-gp mediated drug efflux. LY4052031 is a fully human monoclonal anti-Nectin-4 antibody conjugated to a novel TOPO 1 inhibitor by a cleavable peptide linker at a homogeneous drug antibody ratio (DAR) of 8:1. In vitro, both LY4052031 and its unconjugated parental antibody specifically bind to Nectin-4 expressing cell lines and are quickly and efficiently internalized. LY4052031 demonstrated potent cytotoxicity on tumor cells with high and low Nectin-4 expression. Additionally, bystander activity exerted by LY4052031 on antigen negative cells co-cultured with antigen positive cells was greater than that observed with the clinical benchmark enfortumab vedotin-ejfv. In vivo studies in xenografts expressing low to high levels of Nectin-4 showed significant tumor growth inhibition following treatment with LY4052031 as monotherapy. Overall, LY4052031 exhibits specificity, selectivity, potency, and effectiveness as a next generation therapy to treat Nectin-4 positive tumors. An IND submission is planned for 2024. Citation Format: Divya Sagar, Mohan Srinivasan, Kevin Lindquist, Qianxu Guo, Wailin Wong, Maria B. Lebron, Rose Marie Sattler, Jieyu Zhou, Whitney Helms, Jeffrey Boyles, Petra Verdino, Xuan Zhao, Yvonne Mak, Joshua Park, Rikke Holmgaard, Kyla Driscoll, Omar Duramad, Kristin Bedard. A next generation treatment for Nectin-4 positive cancers - Preclinical characterization of LY4052031, an anti-Nectin-4 antibody, conjugated to a novel camptothecin payload [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 1872.

Abstract 7215: Nectin-4 targeted therapy with MMAE protodrug results in anti-tumor efficacy mediated by click chemistry

Abstract Shasqi is advancing the Click Activated Protodrugs Against Cancer (CAPAC®) platform based on click chemistry, a Nobel Prize winning technology. The platform is modular and comprises 1) an activator that target specific antigens, and 2) inert cancer drugs, protodrugs, which are selectively activated at tumors via click chemistry. The CAPAC technology separates the tumor targeting function from the payload and reunite them at the tumor creating the flexibility to optimize activity while limiting toxicity during preclinical and clinical development. The modularity of the platform enables the rapid development of new therapies as well as unlocking unique treatment benefits such as tunable combinations and payload cycling. We envision that CAPAC will expand the scope of potential targets, widen the therapeutic index of antibody drug conjugates (ADCs). Here we present a Nectin-4-targeting activator with a monomethyl auristatin E (MMAE) payload. Nectin-4 is a clinically validated tumor target expressed in a wide range of solid tumors, making Nectin-4 an attractive target for developing new therapeutic approaches for cancer patients. Substantial numbers of Nectin-4 targeting drugs are being developed but exhibit high rates of drug toxicities and highlight the need for alternative approaches that are efficacious and safe. We have developed a Nectin-4 Fab binder conjugated with tetrazine (~2.3 tetrazines per protein), SQT03, and tested it in combination with SQP22, an attenuated protodrug of MMAE conjugated to trans-cyclooctene (TCO). The reaction between tetrazine and TCO moieties releases MMAE at the tumor site. We have previously demonstrated that SQP22 is highly attenuated in vivo at doses that are > 20x the toxic dose of free MMAE, and in combination with a HER2 targeting activator, led to significant tumor growth inhibition in NCI-N87 gastric cancer xenograft model. The separation of an antigen-targeting activator from the payload by CAPAC technology allowed the rapid development and subsequent testing of SQT03 in combination with SQP22 in vitro and in vivo. SQT03 displayed <10nM binding affinity to Nectin-4 positive cells by flow cytometry analysis. In vivo, dosing of SQT03 occurs 8-24hrs prior to SQP22 to reduce systemic activation and to enable specific release of the active cytotoxic payload at the tumor site. In the T47D breast cancer xenograft model, a single dose of SQP22 at 8-24hrs after SQT03 led to tumor regression without body weight loss, in contrast to the 5% of body weight loss presented by two doses of Enfortumab-vedotin required to lead to similar activity. The presented data illustrates how the CAPAC platform can be used to test various therapeutic combinations, accelerating development, and reducing the time it takes to bring treatments to the clinic. The results support further development and testing of MMAE protodrug with Nectin-4 targeting agent in clinical settings. Citation Format: George Coricor, Jesse M. McFarland, Sangeetha Srinivasan, Stefanie Wagner, Nathan Yee, Tri-Hung Nguyen, Jose M. Mejia Oneto. Nectin-4 targeted therapy with MMAE protodrug results in anti-tumor efficacy mediated by click chemistry [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 7215.

Abstract 2365: Disrupting IL-11/IL-11R signaling by an efficacious anti-IL-11 antibody 9MW3811 enhances T cell tumor infiltration and synergizes with anti-PD-1 therapies in vivo

Abstract Background: IL-11 is known as an inflammation-related factor, and it has been proved to be a key driver in fibrotic diseases. Besides, the roles of IL-11 in tumor immunopathology were recognized more in-depth and comprehensively in recent years. IL-11 expression is highly and positively correlated with overall survival in various cancer types, including colorectal cancer, hepatocellular carcinoma and lung cancer. It was reported that IL-11 promoted tumor cell growth and metastasis, mediated partly through its direct effects on macrophages, T cells and cancer-associated fibroblasts. All these studies indicated that blocking IL-11 signaling may be a promising therapeutic approach for the treatment of solid tumors. In this report, 9MW3811, a high-affinity IL-11 blocking antibody was developed to test its anti-tumor activity and synergistic effects with anti-PD-1 antibody in mouse tumor models. Methods: 9MW3811 was generated by mouse hybridoma technology followed by antibody humanization and affinity maturation. Affinity of 9MW3811 was measured by Octet system. Its blocking activity of IL-11/IL11Ra/gp130 protein interaction was detected by ELISA, and the inhibiting effect of IL-11-mediated signaling was assessed with a luciferase reporter cell-based assay. In vivo efficacy of 9MW3811 was tested on A549 xenograft and LUSC PDX models. ScRNA-seq data collection and computational analysis were used to investigate immune cell tumor infiltration and differentiation. The synergistic tumor-suppressing effect of 9MW3811 with anti-PD-1 antibody was evaluated in MC38, CT26 and Hepa1-6 syngeneic models. Results: 9MW3811 showed sub-nanomolar binding affinity to recombinant and membrane bound IL-11 derived from human, mouse, rat and dog. 9MW3811 effectively blocked the formation of IL-11/IL-11R/gp130 protein complex, and inhibited the downstream cell signaling transduction. In the NSCLC A549 xenograft model, as compared with isotype control hIgG, 9MW3811 (2mpk) showed significant tumor growth inhibition (TGI 62%). In two LUSC PDX models, the TGIs for 9MW3811 (10 mpk) were 50% and 28%, respectively. Further, in MC38 and Hepa1-6 syngeneic models, 9MW3811 addition increased the TGI of anti-PD-1 antibody from 45% to 83%, and 34% to 75%, respectively. Interestingly, in an anti-PD-1 non-responsive CT26 model, the combo of 9MW3811/anti-PD-1 antibody exhibited an impressive antitumor activity (TGI 67%). Mechanistic study showed that treatment with 9MW3811 could significantly ameliorate T cell exhaustion, increase CD8+ T cells tumor infiltration and enhance the cytotoxic function of these infiltrated T cells by modulating the expression of a variety of cytokines/chemokines Conclusion: Our results demonstrated profound antitumor activity of 9MW3811 in different tumor models. 9MW3811 is currently in phase I clinical trials in AU, CN and US. Citation Format: Shuang Wang, Chang Zhang, Shasha Jiao, Dadi Zeng, Rongjuan Wang, Min Wang, Weining Lu, Bin Zheng, Xun Gui, Jinchao Zhang. Disrupting IL-11/IL-11R signaling by an efficacious anti-IL-11 antibody 9MW3811 enhances T cell tumor infiltration and synergizes with anti-PD-1 therapies in vivo [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 2365.

Abstract 5947: Discovery of ACE-47228211, a highly potent and selective SOS1 inhibitor

Abstract Dysregulation of receptor tyrosine kinase (RTKs) and KRAS signaling is the most frequent causes of cancer development and progression. SOS1 is one of the major guanine nucleotide exchange factors (GEFs) that facilitates the conversion of the inactive GDP-bound KRAS “off” state to the activated GTP-bound KRAS “on” state. SOS1 is therefore required for dysregulated RTKs, and wildtype and mutant KRAS proteins to drive cancer cells. In addition, SOS1 plays a crucial role in modulating the reactivation of the RAS/MAPK signaling upon the treatment of RAS/MEK/ERK inhibitors. Thus, blocking SOS1 and KRAS protein-protein interactions could be an effective strategy for targeting KRAS-MAPK driven cancers. Here, we report the discovery of a highly potent and orally bioavailable small molecule SOS1 inhibitor, ACE-47228211. This molecule has a unique novel scaffold. It exhibits an IC50 of 8.5 nM in the SOS1-KrasG12D (GDP) exchange assay and 5.0 nM in cellular ERK phosphorylation assay in H1957 cells. ACE-47228211 at 3 mg/kg (BID) demonstrated significant tumor growth inhibition in MiaPaca-2 KRAS G12C tumor model than MRTX0920 at 50 mg/kg (BID). When combined with Sotorasib (5 mg/kg QD), a Kras G12C inhibitor, ACE-47228211 at 3 mg/kg exhibited synergistic effect similar to MRTX0920 at 50 mg/kg. Further, ACE-47228211 demonstrated synergistic effects with EGFR and FGFR2 inhibitors in RTK mutant tumor models. ACE-47228211 has excellent ADME and physical properties with low risks of hERG, CYP inhibition and drug-drug interactions. The evaluation of ACE-47228211 in a safety panel of 87 targets and a kinase panel of >500 targets shows that this molecule has favorable selectivity and safety profiles. The molecule is currently in IND enabling stage of development. Citation Format: Junmei Wang, Wenqian Li, Sanjeev Kumar, Weitao Pan, Zhiming Wen, Tinggui Yin, Genshi Zhao, Kuo-Long Yu. Discovery of ACE-47228211, a highly potent and selective SOS1 inhibitor [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 5947.