Therapeutic Options Research Articles

Non-coding RNAs in adipose-derived stem cell exosomes: Mechanisms, therapeutic potential, and challenges in wound healing

The treatment of complex wounds presents a significant clinical challenge due to the limited availability of standardized therapeutic options. Adipose-derived stem cell exosomes (ADSC-Exos) are promising for their capabilities to enhance angiogenesis, mitigate oxidative stress, modulate inflammatory pathways, support skin cell regeneration, and promote epithelialization. These exosomes deliver non-coding RNAs, including microRNAs, long non-coding RNAs, and circular RNAs, which facilitate collagen remodeling, reduce scar formation, and expedite wound healing. This study reviews the mechanisms, therapeutic roles, and challenges of non-coding RNA-loaded ADSC-Exos in wound healing and identifies critical directions for future research. It aims to provide insights for researchers into the potential mechanisms and clinical applications of ADSC-Exos non-coding RNAs in wound healing.

Fedratinib in 2025 and beyond: indications and future applications.

Dysregulated JAK/STAT signaling underlies the pathogenesis of myelofibrosis, a myeloproliferative neoplasm characterized by cytopenias, splenomegaly, and constitutional symptoms. JAK inhibitors, such as fedratinib, are the primary therapeutic option for patients with high-risk or symptomatic myelofibrosis. Fedratinib has characteristics that distinguish it from other commercially available JAK inhibitors, such as its preferential inhibition of JAK2 and its inhibitory effects on kinases such as Fms-like tyrosine kinase 3 and BRD4. Fedratinib is most often used in the second-line setting after intolerance or resistance to other JAK inhibitors, but there is substantial evidence that it is an effective first-line option in the appropriate patient population. Prevention and early treatment of fedratinib-related gastrointestinal toxicity is key to maintaining adequate drug exposure, and clinicians must remain vigilant for Wernicke encephalopathy during treatment. Fedratinib's JAK2 selectivity and kinome profile make it an appealing agent for alternative indications, such as myelodysplastic/myeloproliferative neoplasms and maintenance after bone marrow transplantation, which are under active investigation.

Abstract 1645: Developing first-in-class AR-V7/AR-fl molecular glue degrader to revolutionize prostate cancer therapeutics

Abstract Metastatic castration resistance prostate cancer (mCRPC) is a lethal disease due to the resistance of standard-of-care (SoC) treatments, including androgen receptor (AR) pathway inhibitors and taxanes. Treatment resistance occurs partly due to the expression of constitutively active AR splice variants, that hijack AR signaling even after castration. AR-V7 is the most prevalent variant and is expressed in ∼75% of patients with mCRPC, which confers resistance to SoC treatment. Currently, there is no AR-V7 pharmacologic inhibitor, limiting patients’ therapeutic options. Thus, AR-V7 inhibition remains an urgent clinically unmet need. To address this gap, we performed a robust high-throughput phenotypic screen of ∼170K compounds to identify the first AR-V7 protein glue degraders. In addition to degrading AR-V7, our hit compound also degraded full-length AR (AR-fl), having a unique chemotype compared to all existing AR modulators. Hit-to-lead optimization through medicinal chemistry and SAR studies has yielded more potent lead AR-V7/AR-fl degraders (IC50 of <100 nM). Mechanistically, our lead compounds promoted Cullin-RING E3 ligase-mediated proteasomal degradation of AR-V7 and AR-fl within 4 hours, which was blocked by the proteasome inhibitor, bortezomib. Currently, while several AR-fl-PROTAC degraders are in preclinical and early clinical development, no AR-V7 degrader exists. Our lead compounds are the only degraders that target both AR-fl and AR-V7. They bind to the TAU1 and AF-1 functional subdomains within the AR N-terminus (NTD), which is shared by both AR isoforms. Preliminary molecular docking experiments using RoseTTAFold2 further supported this binding. Additionally, Cryo-EM analysis identified conformational changes of AR-fl in the presence of our compounds indicating direct binding, which was also confirmed by cellular thermal shift assays. Importantly, our lead compounds effectively reversed SoC treatment-resistance in preclinical models and demonstrated higher potency than enzalutamide or ARV-110 (AR-fl-PROTAC). Our lead compounds showed excellent on-target activity, favorable drug-likeness, and promising pharmacokinetics, with strong stability, oral bioavailability, and efficacy in enzalutamide-resistant mCRPC xenografts expressing both AR-V7 and AR-fl. We are also conducting an E3-ligase CRISPR screen to nominate the E3 ligase that mediates the degradation activity and using global proteomics to assess potential off-target effects. Collectively, these data support a first-in-class molecular glue degrader mechanism, enabling rapid degradation of both AR-fl and AR-V7 through targeting the AR NTD. In summary, our compounds offer a dual-targeting approach in a single treatment and have the potential to dramatically improve survival for patients with mCRPC and prevent the emergence of AR-V7 expression in patients with earlier-stage disease. Citation Format: CheukMan Cherie Au, Michelle Naidoo, Catrina Estrella, Prerna Vatsa, Ying Wang, Zhao Wang, David M. Nanus, Urko del Castillo, Paraskevi Giannakakou. Developing first-in-class AR-V7/AR-fl molecular glue degrader to revolutionize prostate cancer therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1645.

Abstract 1289: A preclinical platform of PDX breast cancer models and their cellular counterparts to identify resistance mechanisms and novel therapeutic options

Abstract Despite significant advancements in understanding the biology and genetics of breast cancer, the development of effective therapies requires predictive and physiologically relevant preclinical models for their evaluation. In this context, patient-derived xenografts (PDX) have become a standard tool as they reproduce the biology of the original tumors in terms of histology, genotype, and response to chemotherapy. They have proven their relevance in studying pathways leading to cancer development and progression, mechanisms related to tumor resistance, and identifying new effective therapies. We offer a preclinical platform of over 60 fully characterized breast cancer PDX models and their in vitro cell derivatives for preclinical evaluation of new treatment modalities. Our platform consists of a PDX collection of 43 TNBC models, 9 ER+, 5 HER2+, 3 Luminal B (ER+ HER2+) models, and 14 cellular models derived from a subset of these PDX (PDXDC), representing the diversity of breast cancer. PDX models were obtained by transplanting post-operative tumor samples, either by grafting tumor fragments into the interscapular region of nude mice or by injecting dissociated tumor cells into the mammary fat pad of NOD-Scid mice. PDXDC were obtained from dissociated PDX tumors cultured under various media and matrix conditions. All models (PDX and PDXDC) were characterized at molecular level, including transcriptomic, whole exome sequencing, IHC marker staining and/or cytometry analysis. PDX were characterized pharmacologically for response to standards of care as a single agent or in combination. Our PDX and PDXDC panels primarily reflects the molecular heterogeneity of breast cancer and accurately reproduces the molecular and drug response profile of patient tumors. It is widely used for standard drug evaluations, but also for in vivo "mouse clinical trials" (MCT) which provide more predictive preclinical data on the efficacy of a single agent or drug combination. Additionally, we generated standard-of-care resistant models from our PDX panel to study the resistance mechanisms underlying breast cancer progression and to mimic what is observed in the clinic. Associated to in vitro cell derivatives, our collection provides a powerful preclinical platform for translational and preclinical research to identify mechanisms underlying acquired resistance to current therapies and develop novel treatment strategies against breast Cancers. Citation Format: Emilie Indersie, Léa Sinayen, Aurore Gorse, Marie Tavernier, Enora Le Ven, Ester Morgado, Laurent Pouyet, François Romagné, Olivier Déas. A preclinical platform of PDX breast cancer models and their cellular counterparts to identify resistance mechanisms and novel therapeutic options [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1289.

Cognitive impairment in depression and cerebrovascular disease

The treatment of patients with cognitive impairment (CI) remains an urgent problem of modern neurology and psychiatrydue to the widespread prevalence of CI and the predicted increase in the number of patients in the future. Among the most common reasons for the development of cognitive deficits in young patients are depressive disorders, and in the elderly – vascular disease of the brain, Alzheimer's disease and their combination. We discuss pathophysiological features of CI in depression, and possible therapeutic options that allow to choose personalized therapy and improve the quality of life of patients.

Abstract 7461: Identifying molecular vulnerabilities in rare cancers using a novel graph-based therapeutic discovery model

Abstract Background: Rare cancers, as defined by the WHO criteria with an incidence of fewer than 6 cases per 100, 000 people annually, pose significant challenges in diagnosis and treatment due to their low prevalence, heterogeneity, and limited therapeutic options. Patients with rare cancers represent a historically neglected population. Traditional statistical approaches predominantly focus on altered genes, overlooking molecular vulnerabilities that are not explicitly mutated but could still be exploited therapeutically. Methods: We analyzed a cohort of over 1, 000 patients spanning more than 120 distinct rare cancer types (Futreal, A., "Rare cancer patient profiling and engagement", AACR Annual Meeting 2022). By systematically evaluating whole-exome sequencing and RNA sequencing data, we identified genes representing key alterations across the cohort. To uncover both altered and latent molecular vulnerabilities, we applied an integrative, generalizable graph-based AI model explicitly designed for therapeutic discovery. Unlike traditional methods, this model integrates multimodal patient data into a network-based framework, connects genomic alterations with latent dependencies, and identifies hidden signals of molecular vulnerabilities, irrespective of their mutational status. Results were validated using public resources, including the DepMap dataset, without incorporating cell line data as inputs or for model training. Results: Unsupervised clustering revealed 15 molecular subgroups across the cohort. Some clusters, such as CNS (Brain and Spine), exhibited high molecular homogeneity (e.g., 92% of cluster members), while heterogeneous diagnoses like sarcoma were distributed across four clusters, reflecting distinct molecular subtypes. For each cluster, we constructed networks to predict molecular vulnerabilities. Each subgroup yielded at least five prioritized targets associated with FDA-approved or late-stage investigational drugs. Additionally, we identified novel targets that hold promise for innovative drug discovery, offering new avenues for therapeutic exploration. Validation using DepMap data confirmed significant enrichment of these predicted vulnerabilities. Further integration with PRISM and the Genomics of Drug Sensitivity in Cancer (GDSC) datasets refined and prioritized key therapeutic opportunities. Conclusions: This study demonstrates the power of a graph-based therapeutic discovery model to identify key molecular vulnerabilities in rare cancers. By uncovering both altered and latent dependencies, we have laid the foundation for safe and effective therapeutic development in these neglected malignancies. This integrative approach provides a scalable framework for advancing precision oncology in rare tumors, addressing a critical unmet need for novel and repurposed therapeutic options. Citation Format: Li Zhao, Ying Zhu, Randy Chu, Haifeng Zhu, Yuntao Yang, Chunjie Jiang, Mark Knafl, Xingzhi Song, Xiaogang Wu, Jianhua Zhang, Sabitha Prabhakaran, Scott Woodman, Timothy Heffernan, Elizabeth Burton, Rare Tumor Initiative Team, Andy Futreal, Bissan Al-Lazikani. Identifying molecular vulnerabilities in rare cancers using a novel graph-based therapeutic discovery model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7461.

Abstract 6944: Transient pan-RAF inhibitor treatment for melanoma prevention

Abstract Therapeutic options are currently limited for the 15-25% of cutaneous melanomas driven by an oncogenic NRAS mutation. Our previous findings showed that melanoma-associated NRAS substitutions stabilize conformations optimal for BRAF binding, thereby promoting RAF dimerization, proliferative signaling, and ultimately melanomagenesis. Building on these discoveries, we hypothesized that NRAS-mutant melanoma precursors would exhibit substitution-specific sensitivity to pan-RAF inhibition, and that a temporary blockade of RAF signaling would eliminate NRAS mutant-melanocytes in the skin. BRET and NanoBiT complementation assays revealed that pan-RAF inhibitors promote RAS-RAF and RAF-RAF interactions at lower doses in human melanoma cell lines with a weakly melanomagenic NRAS substitution (Q61H) compared to those with a stronger melanomagenic NRAS substitution (Q61R). Surprisingly, these drug-induced RAF complexes were associated with decreased MAPK>ERK signaling and higher drug sensitivity, suggesting that fully inhibited, drug-bound protomers drive increases in NRAS-RAF interactions. To test the mutation-specific sensitivity of NRAS-mutant melanoma precursors in vivo, mouse models of spontaneous NRAS Q61R- or Q61H-driven melanoma were prophylactically treated with a pan-RAF inhibitor for three days and then followed for tumor formation. Consistent with our in vitro data, short-term pan-RAF inhibitor treatment delayed melanoma onset in NRAS Q61H, but not Q61R mice. These findings highlight the critical role of RAF signaling in NRAS-mutant melanoma formation, suggesting that short-term use of effective, targeted therapies could prevent melanoma formation. Citation Format: Rachel E. Lew, Harsha S. Sanaka, Venkat R. Chirasani, Sharon L. Campbell, Christin E. Burd. Transient pan-RAF inhibitor treatment for melanoma prevention [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6944.

Abstract 3495: QL535, A novel CD2-costimulating T cell engager targeting PSMA-positive prostate cancer matching CD28 trispecific antibody in cytotoxicity, minimizing cytokine release and T-cell exhaustion

Prostate cancer is a leading cause of cancer-related mortality in men, highlighting the resistance to current treatments and need for new therapeutic options. PSMA (Prostate-Specific Membrane Antigen) is overexpressed in prostate cancer tissues compared to normal prostatic tissue, rendering it an ideal target for prostate cancer therapies, enabling precise delivery of therapeutic agents to cancer cells. We evaluated PSMA expression in 77 Chinese prostate cancer patients using immunohistochemistry (IHC), confirming its high expression in Chinese malignant prostate tissues. Due to the lack of clinical activity from T cell targeted therapies in solid tumors, recent developments in the field have focused on providing a co-stimulatory signal via CD28 or more recently, CD2. Analysis of single-cell RNA sequencing data from 2,170 cells across 14 mCRPC patients revealed that CD2 expression on tumor-infiltrating lymphocytes (TILs), particularly CD8+ T cells, exceeds that of CD28, underscoring the potential for CD2 targeting in enhancing antitumor immunity. We developed QL535, a novel trispecific antibody in a 2+1+1 format designed to bridge tumor cells via PSMA and activate T cells through CD3 (signal 1) and CD2 (signal 2) via its ligand CD58. This design aims to stabilize the immune synapse and enhance T-cell cytotoxicity. Additionally, this combination overcomes T-cell exhaustion, with fine-tuned CD3 affinity to improve safety and reduce the risk of cytokine release syndrome (CRS). Comparative analysis was conducted with three trispecific antibody formats targeting CD28, and three formats targeting CD2, resulting in a lead CD2 trispecific antibody, QL535, alongside a CD28 trispecific antibody as a control. QL535 demonstrated superior tumor-specific killing both in vitro and in vivo compared to bispecific CD2-deficient antibodies, and exhibited a favorable safety profile, characterized by low IL-6, TNFα, IFN-γ and IL-8 levels compared to the CD28 trispecific control, which achieved comparable cytotoxicity. Further evaluation using repeated stimulation assays of prostate cancer patient-derived PBMCs showed that QL535 outperformed the CD28 trispecific control, an analog of the clinical benchmark PSMA targeted T cell engager, and our bispecific antibody control in overcoming T-cell exhaustion. Whereas other agents showed diminished cytotoxicity, potentially due to T-cell exhaustion, QL535 maintained durable tumor-specific lysis. Favorable manufacturing (CMC) studies further support QL535’s developability for clinical applications. In conclusion, QL535 is a novel trispecific T cell engager with improved anti-tumor efficacy and safety profile. These findings warrant further clinical investigation to evaluate its safety and efficacy in patients. Citation Format: Xiao Liu, Shenda Gu, Ke Liu, Joshua Morrissette, Jiantao Kong, Guangjie Guo, Yuxia Wang, Xin Zhang, Jiaming Cao, Moyan Hu, Min Sun, Ruixue Ma, Jane Chen, Nathan Ngo, Hejie Zhu, Liwei Wang, Yan Fang, Hao Liu, Shuyong Zhao, Shihao Chen. QL535, A novel CD2-costimulating T cell engager targeting PSMA-positive prostate cancer matching CD28 trispecific antibody in cytotoxicity, minimizing cytokine release and T-cell exhaustion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3495.

Abstract 4186: Discovery of novel PARP1-selective inhibitors for treatment of brain tumors using artificial intelligence

Abstract Introduction: Brain tumors, including primary brain tumors and central nervous system (CNS) metastases, remain among the most challenging malignancies to treat, with therapeutic options often limited by the inability of drugs to penetrate the blood-brain barrier (BBB). Poly(ADP-ribose) polymerase (PARP) is a key enzyme in DNA repair, and inhibition of PARP1 specifically drives synthetic lethality in BRCA-mutated disease. While they have achieved commercial success, first generation PARP inhibitors are limited in their utility as they cannot readily pass through the blood-brain barrier and produce adverse side effects, likely driven by the collateral inhibition of PARP2. Development of a PARP1-selective CNS penetrant inhibitor could reduce toxicity, while providing a new therapeutic option for brain tumors. Traditional drug discovery methods are time-consuming and costly, necessitating innovative approaches. Here, we describe the application of Deep Docking combined with generative artificial intelligence (AI), to discover a novel, PARP1-selective inhibitor for use against brain tumors. Methods: Deep Docking utilizes deep learning to accelerate the prediction of the binding affinity of a large number of compounds to target proteins, streamlining the virtual screening process and allowing for rapid docking of billions of compounds against the PARP1 protein. Additionally, state-of-the-art generative algorithms and deep learning techniques for predicting CNS penetrance can be combined with Deep Docking to rapidly perform hit-to-lead optimization of a CNS-penetrating PARP1-selective inhibitor. Results: We will present Deep Docking screening results from billions of compounds. Validating in vitro and in vivo data, including PARP1 inhibition and selectivity, BBB permeability, metabolic stability, pharmacokinetic profile, and CNS penetration will be described. Conclusion: The Deep Docking platform is being used in concert with generative AI approaches to discover and finetune a selective PARP-1 inhibitor for brain tumors. This approach will not only improve the efficiency of drug discovery but also enhance the specificity and efficacy of potential therapeutics. Citation Format: Sarah Truong, Beibei Zhai, Louise Ramos, Mona Marzban, Fariba Ghaidi, Fuqiang Ban, Jason Smith, Mohit Pandey, Ekaterina Manskaia, Kally Singh, Hans Adomat, Xiaoqi Chen, John Langlands, Dennis Brown, Jeffrey Bacha, Colin Collins, Artem Cherkasov, Mads Daugaard. Discovery of novel PARP1-selective inhibitors for treatment of brain tumors using artificial intelligence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4186.

Abstract 367: Temporal dynamics of the senescence-associated secretory phenotype triggered by CDK4/6 inhibitor or doxorubicin treatment in liposarcoma

Abstract Liposarcoma is a rare cancer that frequently exhibits amplification of the cyclin-dependent kinase CDK4 gene. CDK4/6 inhibitors (CDK4/6i) represent a promising targeted therapy to halt proliferation in these tumors, particularly when therapeutic options are limited, and surgical resection is no longer viable. CDK4/6 inhibition can result in either reversible or irreversible exit from the cell cycle (quiescence or senescence, respectively), but the mechanisms driving these outcomes remain unclear. Since CDK4/6 inhibitors appear to induce cell cycle arrest without causing extensive DNA damage, we hypothesize that the senescence-associated secretory phenotype (SASP)—a collection of secreted proinflammatory molecules—induced by CDK4/6i differs significantly from the SASP triggered by cytotoxic chemotherapeutics such as doxorubicin. To investigate this, we characterized differences in SASP gene expression and its upstream regulators using RNA-seq and ATAC-seq in a 28 day time-course study of a patient-derived liposarcoma cell line responsive to both drugs. Our findings reveal that extracellular matrix (ECM) genes are upregulated early in CDK4/6i treatment, a response largely absent in doxorubicin-treated cells. Many of these ECM genes are previously identified SASP components, suggesting a CDK4/6i-specific SASP module. We identified the Hippo pathway regulator TEAD as a key player in shaping this response. Pharmacological inhibition of TEAD suppresses the upregulation of key SASP genes, ANGPTL4 and IGFBP3, which are more strongly induced by CDK4/6i compared to doxorubicin. While the SASP profiles differ between drugs early in treatment, we observe emergence of a shared SASP signature characterized by NF-κB signaling at later time points. This is indicated by upregulation of NF-κB target genes and enrichment of NF-κB motifs in the regions with increased chromatin accessibility under both drugs. In both cases, we detect increased nuclear localization of p65, a subunit of NF-κB, confirming NF-κB activation. Furthermore, addition of an NF-κB inhibitor suppresses the upregulation of NF-κB target SASP genes in both treatments. These results highlight how the composition of therapy-induced SASP evolves over time and contains both common and treatment-specific modules. We also demonstrate that NF-κB activity contributes to shaping part of the CDK4/6i-induced senescence response, addressing an area of ongoing debate in the field. Our study provides new insights into how cancer therapies regulate the SASP profile, with implications for understanding the effects of therapy-induced senescence on the tumor microenvironment. Citation Format: Joanna Lan Hing Yeung, Justin Rendleman, Nicole Pagane, Irene Duba, Andrew Scortea, Lauren Anderson, Ria Hosuru, Bat Ider Tumenbayar, Andrew Koff, Viviana Risca. Temporal dynamics of the senescence-associated secretory phenotype triggered by CDK4/6 inhibitor or doxorubicin treatment in liposarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 367.

Abstract 5340: Simultaneous targeting of CDK4/6 and BETs is independent of RB status in osteosarcoma

Osteosarcoma (OS) is the most prevalent primary bone cancer in children and adolescents, characterized by genetic instability and aggressive progression leading to poor survival. Despite the use of multimodal therapies, survival rates have stagnated around 60% highlighting a critical need for the identification of effective drug targets to improve outcomes. Sequencing efforts reveal cell-cycle dysregulation which may be targeted via CDK4/6 inhibitors (CDK4/6i) such as palbociclib and abemaciclib. While Retinoblastoma proficiency (RB+) has been used as a biomarker of response to CDK4/6i clinically, over 70% of OS patients exhibit RB deficiency (RB-). Therefore, it is imperative to understand to what degree RB- affects response to CDK4/6i in OS. Based on in vitro screening data, we hypothesize a combination of CDK4/6i with bromodomain and extraterminal domain inhibitors (BETi) will potentiate the CDK4/6i anti-tumorigenic effects in both RB+ and RB- OS. A hallmark of OS is high levels of genomic instability and BETi may further induce DNA damage to kill DNA repair-deficient cells. In-vitro combination studies identified dose ratios of CDK4/6i and bivalent BETi (AZD5153) that induce synergistic growth inhibition in a panel of monoallelic and biallelic RB OS cell lines. CRISPR-mediated RB-knockout (KO) clones were developed in human (143B, MG63.3) and murine (K7M2) metastatic OS cell lines. In comparison to wildtype (WT) clones, KO clones were 2-10-fold more resistant to palbociclib and at most 2-fold more resistant to abemaciclib; with differences attributed to broader selectivity profile of abemaciclib. However, dual CDK4/6i and BETi therapy resulted in synergistic growth inhibition in both WT and KO clones. To track emergence of therapeutic resistance, a longitudinal growth assay indicated that dual therapy induced cytotoxicity over time with greater effects observed in KO clones, presumably due to increased genome instability. CDK4/6i therapy with abemaciclib, but not palbociclib, increased C-PARP expression by 2-fold in WT cells and 50-fold in KO cells. Annexin V flow cytometry corroborated these findings, showing apoptosis in 25% of WT cells and 75% of KO cells. Limiting dilution assays revealed that dual CDK4/6i and BETi therapy reduced clonogenic cell frequency, with a more pronounced effect in KO clones. Additionally, RB monoallelic OS PDX models TT2 (pretreated) and PDX96 (naïve), were treated for 6 weeks with CDK4/6i (palbociclib, 40mg/kg, BETi (AZD5153,1 mg/kg), or their combination and significantly reduced tumor growth compared to single agents in both models (p<0.05) and was well tolerated. A trend for increased probability of survival was observed in PDX96. Future studies will extend dosing duration and focus on metastatic and RB- variant models. These findings provide rationale for further study of novel therapeutic options which may expand the clinical utility of CDK4/6i regardless of RB status. Citation Format: Rada Malko, Pankita H. Pandya, Harlan E. Shannon, Erika A. Dobrota, Barbara J. Bailey, Niknam Riyahi, Keiko E. Kreklau, Ryli E. Justice, Melissa A. Trowbridge, Kathryn L. Coy, Anthony L. Sinn, Khadijeh Bijangi-Vishehsaraei, M R. Saadatzadeh, Micheal J. Ferguson, Kyle W. Jackson, Brian D. Weiss, Karen E. Pollok. Simultaneous targeting of CDK4/6 and BETs is independent of RB status in osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5340.

Abstract 4378: BBO-11818, an orally bioavailable, highly potent and non-covalent pan-KRAS inhibitor demonstrates robust anti-tumor activity in KRAS-mutant preclinical models

Abstract KRAS is the most commonly mutated oncogene, altered in approximately 15% of human cancers. While inhibitors of KRASG12C have shown promising clinical efficacy, there are currently no approved targeted therapies against other KRAS variants, resulting in a significant underserved patient population across several major cancer types, including pancreatic carcinoma (PDAC), colorectal cancer (CRC), and non-small cell lung cancer (NSCLC). To address this unmet clinical need, we have developed BBO-11818: a potent, selective, orally bioavailable non-covalent pan-KRAS inhibitor with activity against multiple KRAS mutants, including KRASG12D and KRASG12V, in both their inactive GDP-bound and active GTP-bound states. BBO-11818 binds mutant KRAS with high affinity and selectivity in its active and inactive conformations, locking it in the inactive State 1 to disrupt the association of GTP-bound KRAS with its key effector RAF1. Cell-based assays confirm that BBO-11818 potently inhibits several driver KRAS mutants, resulting in the suppression of MAPK signaling and inhibition of cell proliferation with low nanomolar EC50 values. The selectivity of BBO-11818 for KRAS is demonstrated by its >1000-fold lower potency against NRAS- and BRAF-mutant cell lines. BBO-11818 exhibits favorable pharmacokinetic (PK) and pharmacodynamic (PD) properties in mouse models of cancer. Single dose, oral administration results in strong dose- and time-dependent inhibition of pERK in KRASG12D and KRASG12V cell-derived xenograft (CDX) models. Importantly, BBO-11818 monotherapy induces strong anti-tumor responses, including regression at well-tolerated doses in CDX models of KRAS-mutant pancreatic, non-small cell lung, and colorectal cancer. In combination with either BBO-10203, a selective RAS:PI3Kα breaker that blocks RAS-mediated activation of AKT; or cetuximab, an anti-EGFR monoclonal antibody, BBO-11818 shows significantly enhanced efficacy in models harboring KRASG12D or KRASG12V mutations. BBO-11818 also shows a combination benefit with anti-PD-1 treatment, resulting in complete tumor regressions in the CT-26 syngeneic tumor mouse model. BBO-11818 is a potent pan-KRAS inhibitor with activity against both GTP and GDP forms of KRAS, presenting the opportunity to address, as monotherapy or combination, a large fraction of KRAS mutant tumors currently lacking targeted therapeutic options. Citation Format: Carlos Ernesto Stahlhut Espinosa, Kanchan Singh, Zuhui Zhang, Kyle Sullivan, Nadege Gitego, Megan Rigby, Roger Ma, Patrick Alexander, Saman Setoodeh, Jin Shu, Ken Lin, Dana Rabara, Erik Larsen, Alok Sharma, Albert Chan, Brian P. Smith, Andrew Stephen, Yue Yang, Jun Pei, Felice C. Lightstone, Dhirendra Simanshu, Rui Xu, Chunmei Ji, Keshi Wang, Bin Wang, Kerstin Sinkevicius, Dwight V. Nissley, Eli Wallace, Frank McCormick, Anna E. Maciag, Pedro J. Beltran. BBO-11818, an orally bioavailable, highly potent and non-covalent pan-KRAS inhibitor demonstrates robust anti-tumor activity in KRAS-mutant preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4378.

Abstract 792: Immunoprotective effects of metformin against delayed doxorubicin-induced immune perturbation in C57BL/6 mice

Abstract Introduction: Chronic immunological perturbations that leave cancer survivors with a long list of sequelae, such as an increased risk of death due to infection, remain a major complication of traditional chemotherapy. This risk is particularly pronounced in childhood cancer survivors treated with doxorubicin (DOX), a well-known culprit of immunosuppressive activities that may linger for years following the cessation of chemotherapy. Metformin is a first-line drug against Type-2 Diabetes Mellitus and has recently entered the pharma-oncology limelight due to its senomorphic and immunoprotective properties. In this study, we determined the potential immunoprotective effects of metformin against delayed DOX-induced immune perturbation in a mouse model of childhood cancer survivors. Methods: Five-week-old C57BL/6N mice were randomly assigned to four groups: Control, Metformin, DOX, and Metformin/DOX. DOX-treated mice received intraperitoneal injections with either DOX (4 mg/kg/week) or saline for three weeks. Metformin-treated mice were administered metformin (250 mg/kg/day) via drinking water. Metformin treatment began three days before the first DOX injection and was continued throughout and five weeks post DOX injections. Five weeks following the last dose of DOX, all mice were humanely euthanized in accordance with institutional guidelines. Blood and bone marrow samples were collected during the necroscopy and analyzed with a Flow Cytometer and a Hematological Analyzer to provide insight into individual immune cell populations. Results: Metformin alleviated delayed DOX-induced perturbations in several immune subpopulations. In the innate immune system, metformin decreased neutrophil and monocyte frequency in the blood and bone marrow. However, metformin also ameliorated DOX-induced depletion of the CCR2+ activated and CD86+ invasive monocyte frequencies. In the adaptive immune system, metformin increased the frequency of lymphocytes, particularly B cells, in the blood. This trend is supported by the increased population of Ki67+ proliferating B cells in the bone marrow across all stages of maturation. Conclusion: DOX-induced lingering effects on immune cell populations were partially mitigated by metformin. Metformin improved the functionality of the attenuated monocyte population in the bone marrow and increased the frequency of B lymphocytes in the blood, which can be traced to the expanded population of proliferating B cells in the bone marrow. These results suggest metformin has dual effects on the immune system and may serve as a therapeutic option to mitigate chronic immune perturbations in childhood cancer survivors. Citation Format: Ian J. Ahlberg, Mary R. Daniel, Benu George, Marianne K.O. Grant, Korbyn J.V. Dahlquist, Christina D. Camell, Beshay N. Zordoky. Immunoprotective effects of metformin against delayed doxorubicin-induced immune perturbation in C57BL/6 mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 792.

Abstract 54: Comparative preclinical antitumor assessment of 5FU versus anti-PD1 using in vivo imaging system in MC38 orthotopic tumor model

Abstract Immunotherapy has evolved as potential and practical therapeutic options for primary and metastatic tumors. Orthotopically implanted tumor models are clinically relevant and however growth monitoring of orthotopic tumor & assessing efficacy outcomes poses a practical challenge. Optical imaging by In Vivo Imaging System (IVIS) is a valuable method to monitor the real time progression of in vivo tumor growth without implying the need for interim termination during the study. In the present study, we have evaluated the preclinical efficacy of 5- Fluorouracil in combination with mouse anti-PD1 antibody in orthotopic MC38 model in immunocompetent mice. Subcutaneous tumor was generated in donor mice by inoculation of MC38 luciferase reporter cell line. Tumor fragments (∼30mg) harvested from the donor mice were orthotopically implanted on the subserosal layer of cecum of C57BL/6 mice. Tumor growth was monitored twice weekly by IVIS optical imaging system. Mice were randomized based on total flux signal intensity (1-3 X 106 photons/second). Standalone & combination treatment was initiated with 5-FU; 25 mg/kg, i.p; Q2D and anti-PD-1 at 5 mg/kg, ip; Q4D x 4 doses. Total flux (photons/second), changes in body weight, clinicals signs, mortality were monitored twice weekly up to 2 weeks. At the end of the study, ex vivo bioluminescence signal intensity and tumor weights were recorded. In the current MC38 orthotopic tumor model, standalone treatment of anti-PD-1 and 5-FU resulted in moderate tumor regression. However, combination of 5-FU with anti-PD1 resulted in improved efficacy when compared with individual treatments which was evident from the reduction in signal intensity. In conclusion, evaluating efficacy of combinations treatment in preclinical orthotopic tumor models using IVIS imaging will be helpful tool for an accurate, non-invasive longitudinal monitoring of tumor growth over extended duration. Citation Format: Balaji Ramachandran, Ravindra Ghodke, Satheeshkumar Rajendiran, Bhanupranav Skanda, Krishnappa Haladasappa, Sachin Joshi. Comparative preclinical antitumor assessment of 5FU versus anti-PD1 using in vivo imaging system in MC38 orthotopic tumor model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 54.

Abstract 4117: ADAR1-mediated RNA editing of KCTD13s promotes pancreatic cancer metastasis by impeding RhoA ubiquitination

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with limited therapeutic options and a poor prognosis. Adenosine-to-inosine (A-to-I) RNA editing, a crucial post-transcriptional modification, introduces nucleotide changes in RNA sequences. However, few protein-recoding editing targets with functional significance have been identified. In this study, we propose that the ADAR1-KCTD13s-RhoA/ROCK1 signaling axis plays a critical role in PDAC progression. Methods: We performed an in-depth analysis of A-to-I RNA editing using RNA-sequencing, validated by Sanger sequencing. In vitro phenotypic assays, including proliferation, colony formation, migration, and invasion tests, were conducted. In vivo studies included an orthotopic pancreatic tumor growth model and a lung metastasis model. Protein interactions were evaluated using immunoprecipitation, protein stability was assessed with cycloheximide (CHX) treatment, and ubiquitination was examined with MG132 treatment. Results: Our analysis of A-to-I modifications in PDAC tissues and cell lines identified KCTD13s as a novel protein-recoding RNA editing target. Increased KCTD13s editing levels, driven by the overexpression of adenosine deaminase acting on RNA 1 (ADAR1), were associated with poor survival in PDAC patients. Functional experiments demonstrated that KCTD13s editing promotes pancreatic cancer metastasis. Mechanistically, this amino acid alteration stabilizes the KCTD13s protein by preventing its ubiquitination. The stabilized KCTD13s competes with KCTD13 for binding to CUL3, inhibiting RhoA ubiquitination. This results in elevated RhoA protein levels and activation of the RhoA/ROCK1 signaling pathway. Conclusion: Our findings illuminate the malignancy-promoting role of the ADAR1-KCTD13s-RhoA/ROCK1 signaling axis in PDAC. This study reveals an epigenetic regulatory mechanism mediated by A-to-I RNA editing and highlights the potential of targeting epitranscriptomic pathways for therapeutic intervention in PDAC. Citation Format: Lingxing Zeng, Xiaoyu Wu, Ziming Chen, Jian Zheng. ADAR1-mediated RNA editing of KCTD13s promotes pancreatic cancer metastasis by impeding RhoA ubiquitination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4117.

Abstract 5652: Olverembatinib (HQP1351) in combination with lisaftoclax (APG-2575) overcomes venetoclax resistance in preclinical models of acute myeloid leukemia (AML)

Abstract Background: Combining BCL-2 inhibitor venetoclax with hypomethylating agents is the standard of care for older patients with AML or those ineligible for intensive chemotherapy. However, resistance to venetoclax is a major clinical challenge, necessitating alternative therapeutic options. Olverembatinib targets kinases associated with leukemogenesis and venetoclax resistance, including FLT3, KIT, PDGFR, Src family kinases, PI3K, and FGFR. Here, we evaluated the effects of olverembatinib combined with investigational BCL-2 inhibitor lisaftoclax in venetoclax-resistant AML models. Methods: Primary venetoclax-resistant AML cell line OCI-AML-3 and venetoclax-induced resistant (VEN-RES) FLT3-ITD mutant AML cell lines MOLM-13 and MV-4-11 were used for in vitro experiments. Cellular proliferation was assessed using CellTiter-Glo® assays, and apoptosis was measured by flow cytometry. Western blotting was used to explore mechanisms of action. Both subcutaneous and systemic models using MOLM-13-VEN-RES models were used to evaluate antitumor effects in vivo. Results: Olverembatinib combined with lisaftoclax synergistically inhibited proliferation in all three VEN-RES AML cell lines vs. either drug alone. Flow cytometry confirmed this, revealing limited apoptotic effects with single agents but a significant increase in apoptosis when combined (p < 0.0001). In vivo, in a subcutaneous MOLM-13-VEN-RES model, lisaftoclax (100 mg/kg) administered daily for 14 days exerted no antitumor activity, with a treatment-to-control (T/C) value of 96.54%; olverembatinib (10 mg/kg) alone yielded a T/C value of 12.31%. When coadministered, the combination enhanced antitumor activity (T/C value, 5.05%), with a synergistic index of 2.36. This synergy was recapitulated in a systemic MOLM13-VEN-RES model. Mechanistically, western blot analysis showed that the combination synergistically downregulated FLT3 and its phosphorylation, along with downstream proteins such as AKT, STAT, and ERK and antiapoptotic proteins MCL-1 and BCL-xL; notably, significant upregulated phosphorylated FLT3, AKT, MCL-1, and others have been reported to be associated with mechanisms of venetoclax resistance. The combination also promoted upregulation of proapoptotic proteins BAX, BAK, BID, PUMA, and Noxa, resulting in increased cleavage of caspase-3 and PARP-1. Conclusions: In summary, olverembatinib in combination with lisaftoclax successfully overcame venetoclax resistance in preclinical AML models by downregulating key signaling pathways shown to mediate such resistance. Overall, these findings suggest a potential new therapeutic strategy for venetoclax-resistant AML. Citation Format: Yan Xiong, Zhiyan Liang, Ping Min, Bingxing Wu, Huidan Yu, Guoqin Zhai, Zhou Yu, Dajun Yang, Yifan Zhai. Olverembatinib (HQP1351) in combination with lisaftoclax (APG-2575) overcomes venetoclax resistance in preclinical models of acute myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5652.

Abstract 3155: High-throughput drug repositioning identifies dinaciclib as a potent osteosarcoma inhibitor

Abstract Background: Osteosarcoma (OS) is the most common primary malignant bone tumor, predominantly affecting adolescents and young adults. Despite multimodal treatment combining chemotherapy and surgical resection, survival rates for metastatic OS remain below 20%, underscoring the urgent need for novel therapies. Recent studies implicate chromothripsis, a phenomenon of chromosomal shattering and reassembly, in OS pathogenesis, contributing to its aggressive behavior and treatment resistance. However, therapeutic options for OS have remained largely stagnant over the past two decades. Advancing our understanding of OS biology and identifying new therapeutic approaches are essential to improving outcomes for patients with metastatic and relapsed disease. Methods and Findings: We conducted a high-throughput screen of 3, 800 compounds across eight OS cell lines. Two-thirds of the drug library consists of FDA approved drugs and one-third consists of drugs in early phase clinical trials. Each compound was tested in five concentrations (1 nM to 10, 000 nM), generating over 200, 000 data points to identify active single agents. Dinaciclib, a CDK1/2/5/9 inhibitor, emerged as one of the top-performing agents, ranking in the top 0.5% based on cytotoxicity across all cell lines. Notably, clinically relevant agents Gemcitabine and Docetaxel, components of active retrieval regimens for relapsed OS, also ranked in the top 0.5%. To investigate drug synergy, combinations of Gemcitabine and Docetaxel were tested at varying molar ratios (1:10, 10:1, 1:5, 5:1, and 1:1) across the eight cell lines. The 1:10 molar ratio demonstrated the highest cytotoxicity, consistent with the clinically established 1:9 ratio. Subsequently, an iterative screen assessed the synergy of third agents with the Gemcitabine+Docetaxel regimen in the MG-63 OS cell line. Dinaciclib exhibited additive effects when layered onto this regimen, further supporting its therapeutic potential. Conclusions: This study identifies Dinaciclib as a potent inhibitor of osteosarcoma, with additive cytotoxicity when combined with the clinically relevant Gemcitabine+Docetaxel regimen. These findings, coupled with prior evidence of Dinaciclib's efficacy in reducing metastatic burden in OS patient-derived xenograft models, highlight its potential as part of a triple combination therapy. This research underscores the value of high-throughput drug repurposing in identifying innovative treatment strategies for osteosarcoma and supports further preclinical and clinical evaluation of Dinaciclib to improve outcomes for patients with metastatic or treatment-resistant disease. Citation Format: Mithun Sarangdhar, Jonah Snyder, Eric O'Brien, Brett VanCauwenbergh, Mitali Basu, Joseph Pressey, John Perentesis. High-throughput drug repositioning identifies dinaciclib as a potent osteosarcoma inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3155.

Abstract 5931: Unraveling the genetic complexity of Ph-like ALL: development of a cost-effective diagnostic qPCR panel

Abstract Background: Advancements in high-throughput sequencing have significantly expanded our understanding of B-cell Acute Lymphoblastic Leukemia (B-ALL). In particular, whole-transcriptome sequencing (WTS) has facilitated the discovery of the Ph-like ALL subtype. However, clinical integration of WTS remains challenging due to high costs and lack of standardized workflows. Ph-like ALL is marked by genetic heterogeneity, including diverse fusions and mutations, which complicates its diagnosis and limits targeted therapeutic options. This genetic complexity correlates with poor prognosis, emphasizing the need for accessible and effective diagnostic approaches. Aim: To develop a cost-effective, qPCR-based diagnostic panel for its detection and classification in clinical settings. Methods: A cohort of 394 newly diagnosed B-ALL cases were analyzed using RT-PCR and FISH for initial genetic screening. WTS was employed for comprehensive fusion detection, mutation analysis, and subtype classification. Kaplan-Meier survival analysis was used to evaluate patient outcomes, and a qPCR-based likelihood scoring model was developed based on differential gene expression (DEGs) to identify Ph-like ALL. Results: Whole transcriptome sequencing revealed that 13.1% of the B-ALL cases have Ph-like phenotype, found in different age groups: 9.7% in pediatric patients (n=15), 20.5% in adolescents and young adults (AYA, n=8), and 50% in adults (n=3). Ph-like ALL cases predominantly exhibited fusions involving JAK-STAT pathway genes (n=10), ABL-class genes (n=9), or NTRK1 (n=1), in addition to a novel RUNX1::FGF13 fusion (n=2). Differentially expressed genes were tested for diagnostic potential, with 9 genes (FZH2, PON2, CA6, OLFML2A, BAALC, PRKCZ, ZFPM2, TCFL5 and ENPP2) demonstrating significant ROC (p<0.0001 and sensitivity and specificity >80%) curves in a discovery cohort (n=79). This likelihood model also effectively distinguished Ph-like ALL in a validation cohort (n=150). Additionally, survival analysis revealed significantly worse event-free survival (EFS) and overall survival (OS) in Ph-like ALL patients compared to non-Ph-like patients (EFS: 0% vs. 43.3%, HR 3.40, p=0.006; OS: 0% vs. 45.4%, HR 3.57, p=0.005). Conclusion: This study underscores the genetic diversity of Ph-like ALL. The poor prognosis of Ph-like ALL, marked by significantly reduced EFS and OS, highlights the need for targeted therapeutic approaches. The cost-effective qPCR-based diagnostic panel provides a promising tool for the early detection of Ph-like ALL, offering potential for improved patient outcomes through timely intervention. Citation Format: Anita Chopra, Jay Singh, Mercilena Benjamin, Avanish Pandey, Jayanth Kumar Palanichamy, Sameer Bakhshi, Deepam Pushpam, Akash Kumar Jha, Pranay Tanwar. Unraveling the genetic complexity of Ph-like ALL: development of a cost-effective diagnostic qPCR panel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5931.

Abstract 1624: Stat1 promotes lesion growth and tumor immunity of tuberin-deficient cells in lymphangioleiomyomatosis

Abstract Lymphangioleiomyomatosis (LAM) is a cystic lung disease that primarily affects women, with an estimated global prevalence of 19 per million women. LAM is caused by the invasion of metastatic smooth muscle-like cells into the lung parenchyma, leading to abnormal cell proliferation and progressive respiratory failure. LAM cells have TSC gene mutations, which occur sporadically or in people with Tuberous Sclerosis Complex. Although it is known that hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) due to TSC2 mutations contributes to aberrant cell growth in LAM lung, tumor origin and invasive mechanism remain unclear. Integrative single-cell omics and validation analyses revealed the activation of a novel uterine-similar HOX/PBX transcriptional network in the LAM lung compared to other lung cells, suggesting that the uterus is one of the origins of LAM cells. Further omics studies indicated that STAT1 and STAT3 interact with PBX1 to increase LAM cell survival. The objective of this study is to delineate mechanisms by which STAT signaling may regulate LAM pathogenesis, with hopes to find potential therapeutic options for LAM and TSC-associated disorders. We hypothesize that STAT1 suppression attenuates LAM patient-derived (TSC2-null) cell viability and tumor growth in LAM. We first confirmed our network prediction analysis by showing that aberrant PBX1 activation upregulates STAT1 in LAM cells and tissues. Our cell viability assays show that STAT1 suppression induced TSC2-null cell apoptosis compared to controls. Similarly, our mouse models show that STAT1 suppression attenuates lung lesion and uterine tumor growth in TSC2-deficient LAM models. We also show that STAT1 activation induced PD-L1 upregulation, indicating that STAT1 helps tumor cells to evade immune surveillance in LAM. Our findings provide proof of concept that STAT1 mediates LAM tumor proliferation through two mechanisms. (1) by promoting lesion growth and (2) by promoting immune evasion via upregulation of PD-L1. STAT1 signaling is critical for LAM cell survival and could be targeted to treat LAM and TSC-associated disorders. Citation Format: Tasnim Olatoke, Jane Yu. Stat1 promotes lesion growth and tumor immunity of tuberin-deficient cells in lymphangioleiomyomatosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1624.

Abstract 1789: Preclinical characterization of BGB-B3227, a MUC1 x CD16A bispecific engager, for the treatment of MUC1-expressing solid tumors

Abstract Background: MUC1 is frequently overexpressed in various human epithelial cancers, including NSCLC, gastrointestinal, breast, pancreatic, ovarian, and colon carcinomas. Despite the development of MUC1 targeted therapies, none have shown significant clinical efficacy. BGB-B3227, a novel bispecific antibody targeting MUC1 and CD16A, is designed to induce NK cell activation and subsequent cytotoxicity against MUC1-expressing tumor cells. Methods: The target binding activity of BGB-B3227 was characterized using biochemical and cell-based assays. The ability of BGB-B3227 to avoid the interference from soluble MUC1 was assessed by a competitive FACS assay. The ADCC and ADCP activities of BGB-B3227 were evaluated in co-culture systems consisting of effector cells and tumor cells expressing varying levels of MUC1, both in the presence and absence of human IgG proteins. Furthermore, the in vivo anti-tumor efficacy of BGB-B3227, both as a monotherapy and in combination with anti-PD-1 antibody, was evaluated in the MC-38/hMUC1X model in human CD16A knock-in mice. Results: BGB-B3227 demonstrated high binding affinity to recombinant human CD16A protein and CD16A expressing cells, with comparable binding affinities to both CD16A-158V and 158F variants. BGB-B3227 displayed no detectable binding to either human CD16B NA1 (A) and NA2 variants, underscoring its high selectivity for CD16A. Additionally, BGB-3227 demonstrated high binding affinity to the recombinant SEA domain of human MUC1 protein and MUC1 expressing tumor cells. Compared to HMFG1, which targets MUC1-N, the BGB-B3227’s binding to MUC1 expressing cells was less interfered by soluble MUC1. In cellular assays, BGB-B3227 induced potent ADCC and ADCP activity against MUC1-expressing cells in a dose-dependent manner, which was greater than that of Fc-enhanced mAb and was less affected by human IgG. No activity was observed in MUC1-negative tumor cells, indicating the effect of BGB-B3227 is MUC1 dependent. In mouse models, BGB-B3227 monotherapy demonstrated a dose-dependent anti-tumor efficacy, which was further enhanced when combining with an anti-PD-1 antibody. Importantly, no significant changes in animal body weight were observed across all treatments, suggesting good tolerability of BGB-B3227 in mouse models. Conclusion: BGB-B3227 is a bispecific MUC1xCD16A NK engager demonstrating potent ADCC and ADCP activity, along with notable in-vivo anti-tumor efficacy when used as a monotherapy or in combination with anti-PD-1 therapy. BGB-B3227 represents a promise therapeutic option for MUC1-expressing cancers, with the potential to overcome the limitations of MUC1-N antibodies by mitigating the sink effect from soluble MUC1. Currently, BGB-B3227 alone and in combination with Tislelizumab is under clinical investigation in participants with advanced or metastatic solid tumors (NCT06540066). Citation Format: Hengrui Zhu, Hui Li, Zhuo Li, Qi Liu, Liu Xue, Liang Qu, Ming Jiang, Jie Li, Xin Chen, Wenjie Wang, Yun Chen, Jie Pan, Yuanyuan Xie, Ting Shao, Peiqi Li, Renke Li, Caizhi Liu, Xiaoliang Chen, Lei Jiang, jingyuan Sun, Lingmin Zheng, Xiangli Ma, Juan Yang, Haoxuan Song, Fuyun Sun, Jiyuan Zhang, Xi Wu, Xianyan Tang, Qiansheng Ren, Chichi Huang, Mingchao Kang, Xiaomin Song, Zhirong Shen, Lai Wang. Preclinical characterization of BGB-B3227, a MUC1 x CD16A bispecific engager, for the treatment of MUC1-expressing solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1789.