High Unmet Medical Need Research Articles

Characterization of a Clinically and Biologically Defined Subgroup of Patients with Autism Spectrum Disorder and Identification of a Tailored Combination Treatment

Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders (NDDs) with a high unmet medical need. The diagnosis of ASD is currently based on behavior criteria, which overlooks the diversity of genetic, neurophysiological, and clinical manifestations. Failure to acknowledge such heterogeneity has hindered the development of efficient drug treatments for ASD and other NDDs. DEPI (Databased Endophenotyping Patient Identification) is a systems biology, multi-omics, and machine learning-driven platform enabling the identification of subgroups of patients with NDDs and the development of patient-tailored treatments. In this study, we provide evidence for the validation of a first clinically and biologically defined subgroup of patients with ASD identified by DEPI, ASD Phenotype 1 (ASD-Phen1). Among 313 screened patients with idiopathic ASD, the prevalence of ASD-Phen1 was observed to be ~24% in 84 patients who qualified to be enrolled in the study. Metabolic and transcriptomic alterations differentiating patients with ASD-Phen1 were consistent with an over-activation of NF-κB and NRF2 transcription factors, as predicted by DEPI. Finally, the suitability of STP1 combination treatment to revert such observed molecular alterations in patients with ASD-Phen1 was determined. Overall, our results support the development of precision medicine-based treatments for patients diagnosed with ASD.

Thiazides for kidney stone recurrence prevention.

Kidney stones are the most common condition affecting the kidney, and characterized by a high rate of recurrence. Thiazide and thiazide-like diuretics (thiazides) are commonly prescribed to prevent the recurrence of kidney stones. This review offers a comprehensive up-to-date assessment of the evidence supporting the use of thiazides for kidney stone recurrence prevention, highlights potential harms associated with treatment, and identifies areas of knowledge that require further investigation. The clinical routine to prescribe thiazides for kidney stone prevention has recently been challenged by the findings of the large NOSTONE trial that failed to show superiority of hydrochlorothiazide at doses up to 50 mg daily over placebo in preventing a composite of clinical or radiological recurrence in patients at high risk of recurrence. Yet, adverse events such as new onset diabetes mellitus and gout were more common in patients receiving hydrochlorothiazide compared to placebo. As demonstrated by a novel meta-analysis presented in this review encompassing all randomized placebo-controlled trials with thiazide monotherapy, current trial evidence does not indicate that thiazide monotherapy is significantly better than placebo in preventing kidney stone recurrence. Given the limited efficacy and possible adverse effects, we advocate for a restrictive use of thiazides for kidney stone recurrence prevention. Clearly, there remains a high unmet medical need for effective, targeted therapies to prevent recurrence of kidney stones.

Abstract CT246: Open-label, single-arm, multicenter, phase 2 trial of garsorasib in KRAS G12C-mutated non-small-cell lung cancer

Abstract Background: Garsorasib (D-1553), a potent KRAS G12C inhibitor, has previously demonstrated promising anti-tumor activity in KRAS G12C-mutated non-small-cell lung cancer (NSCLC) in a phase 1 study. Here we present the efficacy and safety of garsorasib in a pivotal phase 2 study. Methods: In this open-label, multicenter, single-arm phase 2 study, patients received garsorasib 600 mg twice daily in 21-day cycles. Eligible criteria included patients with locally advanced or metastatic NSCLC harboring KRAS G12C mutation, who had disease progression after prior anti-PD-(L)1 therapy and platinum-based chemotherapy or intolerance to the above regimens due to toxicity, and had measurable tumor lesions according to the RECIST, v1.1. The primary end point was objective response rate (ORR) evaluated by independent review committee (IRC) per RECIST v1.1. The secondary end points included duration of response (DOR), disease control rate (DCR), time to response (TTR), progression-free survival (PFS), overall survival (OS), and safety. Results: As of November 17, 2023, 123 patients (108 [87.8%] male, median age 64 [range: 33-80], and 11.4%/88.6% ECOG PS 0/1) were enrolled and treated, with a median follow-up of 7.92 months (range, 0.7, 16.5) and a median duration of treatment of 6.24 months (range, 0.7, 15.9). At data cutoff date, 82 patients (66.7%) discontinued treatment, with disease progression (46 patients [37.4%]) being the most common reason. Among 123 patients, IRC confirmed-ORR was 49.6% (61/123, 95% CI, 40.5 to 58.8) and DCR was 88.6% (109/123, 95% CI, 81.6 to 93.6). The median TTR was 1.38 months (range, 1.12 to 5.55). The median DOR was 12.78 months (95% CI, 6.21 to NE). The median PFS was 7.56 months (95% CI, 5.55 to 9.69), and the median OS was not reached. A total of 117 (95.1%) patients reported treatment-related adverse events (TRAEs) with 61 (49.6%) patients experiencing grade 3 or higher events. The most commonly reported (≥25%) TRAEs (any grade) were increased AST, ALT and γ-GGT, anemia, increased blood bilirubin, and increased blood ALP. No new safety signals were identified, and most of the adverse events were well managed. No TRAE resulted in permanent discontinuation of garsorasib. Conclusions: Garsorasib has shown a high tumor response rate and long response duration in patients with KRAS G12C mutated NSCLC that have progressed after prior anti-PD-(L)1 therapy and platinum-based chemotherapy. Its safety profile was also shown to be well-tolerated and manageable. Garsorasib could be considered as a promising treatment option for KRAS G12C-mutant NSCLC patients with a high unmet medical need. Citation Format: Ziming Li, Xiaomin Dang, Dingzhi Huang, Shi Jin, Weiwei Li, Jianhua Shi, Xicheng Wang, Yiping Zhang, Zhengbo Song, Junping Zhang, Wu Zhuang, Xuewen Liu, Liyan Jiang, Xiangjiao Meng, Mingfang Zhao, Jianying Zhou, Liangming Zhang, Pingli Wang, Hui Luo, Junquan Yang, Shundong Cang, Xiang Wang, Jing Wang, Jiuwei Cui, Yan Yu, Zhihong Zhang, Junguo Lu, Weihua Yang, Gaofeng Li, Jifeng Feng, Dongqing Lv, Lin Wu, Yong Fang, Yan Wang, Yanqiu Zhao, Baoshan Cao, Wei Zhu, Zhixiang Zhuang, Qingshan Li, Mingxi Wang, Huan Zhou, Xiaorong Dong, Sheng Hu, Jian Fang, Yihong Zhang, Wenjia Wang, Ziyong Xiang, Zhe Shi, Ling Zhang, Shun Lu. Open-label, single-arm, multicenter, phase 2 trial of garsorasib in KRAS G12C-mutated non-small-cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT246.

Abstract ND08: M3554, a novel anti-GD2 antibody drug conjugate

Abstract The glycosphingolipid GD2 is a cell membrane component of a limited number of normal tissues including nerve cells, melanocytes or lymphocytes. However, in some tumor types as neuroblastoma, osteosarcoma, glioma, or soft tissue sarcoma, GD2 is found on cell membranes with high levels. This tumor associated expression pattern makes GD2 an attractive target for therapeutic antibodies like dinutuximab (ch14.18) and naxitamab, which have been approved for neuroblastoma. M3554 is designed a be novel anti-GD2 ADC based on the humanized ch14.18 anti-GD2 antibody. The payload linker consists of the Topoisomerase I inhibitor (TOP1i) payload exatecan and a cleavable beta-glucuronide linker structure, which demonstrated higher potency, better bystander effects and improved activity in multidrug resistant cancer cells compared to other TOP1i payloads. While the antitumor effect of approved anti-GD2 antibodies is presumably related to Antibody-Dependent Cellular Cytotoxicity (ADCC) and Complement- Dependent Cytotoxicity (CDC), M3554 will exploit the high antigen density for direct tumor cytotoxicity by the payload. As the ADCC and CDC effector functions are believed to cause side effects for the approved GD2 antibodies, we have modified the M3554 antibody moiety with mutations in the Fc-region to reduce or eliminate these Fcγ receptor mediated functions. The cytotoxicity of M3554 was in the subnanomolar IC50 range for the GD2-positive neuroblastoma cell line CHP134. M3554 showed strong in vivo antitumor activity with tumor regressions in the CHP134 xenograft model and in patient-derived xenografts from neuroblastoma, osteosarcoma or glioma at doses ranging from 3 to 10 mg/kg. In addition, M3554 showed favorable pharmacokinetics in rats and monkeys, indicating a very stable linker-payload, and a favorable safety profile. In conclusion, M3554 represents a novel therapeutic approach for oncology indications with a high unmet medical need and high GD2 prevalence. Disclosures: Christiane Amendt, Christine Knuehl, Willem Sloot, Stanley Sweeney-Lasch, Joao NS Pereira, Julia Dotterweich, Hans-Henning Boehm and Jan Anderl are employees of the healthcare business of Merck KGaA, Darmstadt, Germany. Timothy Crandall is an employee of EMD Serono. Mira Toister-Achituv is an employee of Inter-Lab Ltd., Yavne, Israel, an affiliate of Merck KGaA, Darmstadt, Germany.Sponsor: This study was sponsored by the healthcare business of Merck KGaA, Darmstadt, Germany (CrossRef Funder ID: 10.13039/100009945). Citation Format: Christiane Amendt, Christine Knuehl, Timothy Crandall, Willem Sloot, Mira Toister-Achituv, Stanley Sweeney-Lasch, Joao NS Pereira, Julia Dotterweich, Hans_Henning Boehm, Jianguo Ma, Jan Anderl. M3554, a novel anti-GD2 antibody drug conjugate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr ND08.

Abstract 5301: Tumor-targeted activation of CD137 using Bicycles: New insights into mechanism of action and discovery of BT7455, a clinical candidate for the treatment of EphA2-expressing cancers

Abstract Introduction: Clinical studies in cancer patients have validated CD137 agonism as an activator of the immune system to enable tumor rejection. We have demonstrated that small, chemically synthetic bicyclic peptides can drive tumor-localized agonism of CD137 and anti-tumor immunity in mouse models. Here, we report the next stage of our work - delving into the mechanism of action of these novel agents and extending our program to serve patients whose tumors express EphA2. Experimental Procedures: MultiOmyx™ hyperplexed immunofluorescence assay was used to evaluate the expression of CD137 and EphA2 in head and neck squamous cell carcinoma samples. Human PBMC/tumor cell co-culture assays were used to assess CD137 Bicycle TICA™ in vitro bioactivity and syngeneic mouse tumor models were used to evaluate CD137 Bicycle TICA anti-tumor activity as mono- or combination therapies. Pharmacodynamic activity was evaluated by transcriptional profiling using NanoString assays or single cell RNA sequencing. Summary of the Data: Studies utilizing a syngeneic mouse model and deep RNA sequencing of tumors from CD137 Bicycle TICA-treated mice implicated intratumoral dendritic cells in addition to T cells as early responders to localized CD137 agonism and potential contributors to the anti-tumor response. Furthermore, a mouse efficacy model demonstrated synergy with checkpoint inhibitor therapy. Multiplex imaging revealed that EphA2 and CD137 are co-expressed in human tumors of high unmet medical need and therefore, using our highly modular Bicycle platform, we discovered BT7455, a Bicycle TICA that engages EphA2 and CD137 with high affinity, resulting in potent EphA2-dependent activity in vitro and robust anti-tumor activity in vivo with intermittent dosing in mouse models. Gene expression profiling of tumors revealed that BT7455 led to increased production of cytokines and chemokines known to drive T cell infiltration, the extent of which differentiated it from both a checkpoint inhibitor and an anti-CD137 monoclonal antibody agonist. BT7455 was well tolerated in preclinical species and liver function tests indicated no evidence of hepatic toxicity. Statement of Conclusions: In summary, we have identified EphA2 as a promising target to pair with a CD137 agonist. In addition to CD8+ T cells, tumor-resident dendritic cells are a likely contributor to anti-tumor immunity following treatment with Bicycle® TICAs, supporting utility for Bicycle® tumor-targeted CD137 agonists in solid tumors beyond those that are highly T cell-infiltrated. We have advanced a clinical development candidate, BT7455, to realize this potential for patients with EphA2-expressing cancers. Citation Format: Johanna Lahdenranta, Kristen Hurov, Heather Cohen, Lia Luus, Cara Bray, Peter Brown, Anna Devlen, Carly Campbell, Matthew Gray, Mike Kelly, Gemma Mudd, Punit Upadhyaya, Sailaja Battula, Kelvin Zhang, Anne-Sophie Dugast, Kevin McDonnell, Phil Brandish, Nicholas Keen. Tumor-targeted activation of CD137 using Bicycles: New insights into mechanism of action and discovery of BT7455, a clinical candidate for the treatment of EphA2-expressing 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 5301.

Abstract 1974: Discovery of TRX-211-399, a potent, CNS-penetrant, highly selective inhibitor of EGFR exon 20 insertion mutations

Abstract Lung cancer is the leading cause of cancer-related deaths worldwide, accounting for approximately 2 million new cases and 1.8 million deaths annually. Various types of EGFR-activating mutations are one of the most important oncogenic drivers in non-small cell lung cancer (NSCLC). Among NSCLC patients with EGFR mutations, 5-10% of patients have EGFR exon 20 insertion (ex20ins) mutations that are insensitive to clinically available EGFR tyrosine kinase inhibitors (TKIs). Recently, as mobocertinib (EXKIVITY®) failed to improve progression-free survival in Phase 3 clinical trial, there remains a high unmet medical need to develop new drugs with wider therapeutic window to treat NSCLC harboring EGFR ex20ins mutations. Herein, we report a novel EGFR-TKI, TRX-211-399, specifically designed to target ex20ins mutations. TRX-211-399 potently inhibited the proliferation of not only Ba/F3 cells overexpressing near-loop (A767dupASV, S768dupSVD) and far-loop (H773insNPH, H773dupH) mutations but also patient-derived NSCLC cell line. In particular, TRX-211-399 demonstrated high selectivity against wild-type EGFR. With favorable DMPK profiles, once-daily oral administration of TRX-211-399 showed significant tumor regression in multiple Ba/F3 xenograft models carrying different EGFR exon20ins mutations. Furthermore, in a PC-9-luc cell intracranial xenograft model, TRX-211-399 induced substantial anti-tumor effects and prolonged survival without body weight loss. TRX-211-399 is currently undergoing further preclinical evaluation as a potential candidate for clinical development for patients with EGFR exon20ins mutations. Citation Format: Kwangwoo Chun, Sumin Lim, Joohyun Lee, Seulgi Choi, Seongrak Kim, Youngil Choi, Areum Park, Bohee Kim, Yongseo Park, Eunhyun Choi, Sungwon Lee, Koo Lee. Discovery of TRX-211-399, a potent, CNS-penetrant, highly selective inhibitor of EGFR exon 20 insertion mutations [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 1974.

Abstract 6716: DLL3 TriTCE Co-Stim: A next generation trispecific T cell engager with integrated CD28 costimulation for the treatment of DLL3-expressing cancers

Abstract Small cell lung cancer (SCLC) is an aggressive neuroendocrine cancer with a poor prognosis and high unmet medical need. Current standards of care, including chemotherapy, targeted therapy and immunotherapy, are associated with limited duration of response. Furthermore, SCLC is characterized by an immunosuppressive microenvironment and poor T cell infiltration which present additional treatment challenges. Delta-like ligand 3 (DLL3) is an inhibitory Notch ligand that is aberrantly overexpressed in SCLC and other neuroendocrine tumors, but minimally expressed in normal tissues, and is a new therapeutic target. Bispecific T cell engagers (TCE) targeting DLL3 have entered the clinic and demonstrated promising anti-tumor activity in SCLC patients; however, we believe there is room to improve on the rate and depth of response. To address treatment challenges and enhance the durability and sustainability of T cell activation, we have engineered a trispecific co-stimulatory T cell engager (TriTCE Co-stim) molecule that optimally engages CD3 and CD28 and redirects and enhances cytotoxic T cell responses to DLL3-expressing tumor cells while maintaining a desired safety profile. A panel of DLL3xCD3xCD28 trispecific antibodies (Abs) was engineered with a conventional anti-CD28 agonist paratope in a variety of Ab formats, geometries, paratope affinities and specificities. Geometry and design features of the tri-specific Abs were informed by prior TriTCE Co-stim molecule optimization1. AzymetricTM and EFECTTM platforms were used to facilitate heterodimeric multi-chain antibody assembly with silenced Fc gamma function. Lead TriTCE Co-stim Abs were selected for enhanced DLL3-dependent antitumor cytotoxic activity and increased T cell function including T cell activation, proliferation and cytokine production, compared to competitor bispecific TCEs. DLL3-independent activity and cytokine release were assessed with human PBMCs in solid and solution phase assays to evaluate the potential for cytokine release induction. In summary, we have identified multiple TriTCE Co-Stim Ab formats with improved DLL3-dependent cytotoxicity and T cell activation over competitor bispecific TCEs across multiple DLL3-expressing tumors. By screening various Ab formats, geometries and paratope affinities, we have selected lead DLL3 TriTCE Co-stim Abs displaying target-dependent activation of T cells with potent anti-tumor activity which may translate to improved and more durable antitumor responses in the treatment DLL3-expressing cancers. Citation Format: Peter Repenning, Desmond Lau, Diana C. Hernaez, Alec Robinson, Diego P. Escanda, Mariana Rocha, Begonia S. Moreno, John Zhang, Polly Shao, Nichole Escalante, Lisa Newhook, Purva Bhojane, Chayne L. Piscitelli, Paul A. Moore, Thomas Spreter Von Kreudenstein, Nina E. Weisser. DLL3 TriTCE Co-Stim: A next generation trispecific T cell engager with integrated CD28 costimulation for the treatment of DLL3-expressing 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 6716.

Abstract 2623: Enabling 5T4 for targeted cancer therapy: TUB-030, a novel ADC built with ethynylphosphonamidate conjugation chemistry, shows long-lasting anti-tumor activity via Topoisomerase-I inhibition with an optimized therapeutic index

Abstract TUB-030 is a novel Antibody-Drug Conjugate (ADC) targeting the oncofetal 5T4 antigen, a glycoprotein, that is functionally involved in regulation of the Wnt signalling pathway and promoting cellular motility and adhesion. Immunohistochemical analysis identified 5T4 overexpressed in many types of cancers, including bladder, lung, breast, stomach, esophagus, head and neck, colon, and ovarian. Analysis in fresh frozen healthy human tissue with the therapeutic mAb candidate of TUB-030 revealed limited cross reactivity. Ethynylphosphonamidate conjugation chemistry was used to build TUB-030 with a homogenous DAR (drug-antibody-ratio) of 8 and the Topoisomerase I inhibitor Exatecan as payload, which is connected to a humanized, Fc-silenced IgG1 antibody targeting 5T4 using a cleavable linker system. Overall, TUB-030 contrasts previous ADC designs targeting 5T4, implementing several layers of differentiation in terms of antibody, payload and conjugation technology. In vitro, TUB-030 is characterized by sub-nanomolar affinity to 5T4, efficient target-mediated internalization and strong cytotoxicity towards cancer cells from different tumor indications with a broad range of 5T4 expression levels. Differently to previous 5T4-targeting ADCs, TUB-030 has efficient bystander activity against co-cultured target-negative cells, which facilitates targeting of tumors with heterogenous 5T4 expression. Pharmacokinetic analysis showed that TUB-030 is highly stable - and does not lose or transfer its linker-payload to serum proteins during blood circulation and antibody-like clearance profile contrasting maleimide-conjugated ADCs and enabling most efficient and continued delivery of Exatecan to the tumor site. Single-dose treatment with TUB-030 results in long-lasting tumor regression with high complete remission rates across a variety of both cell-line derived xenograft (CDX) and patient-derived xenograft (PDX) cancer models of multiple tumor indications in vivo, including models with low target expression. Preliminary repeat-dose toxicological assessment of TUB-030 in a pharmacologically relevant non-human primate species demonstrated that TUB-030 is well tolerated. The preclinical results underline that TUB-030 with novel ADC technology has the potential to enable 5T4 as a therapeutic target and provide treatment options in numerous solid cancer indications with high unmet medical need supporting further development towards the clinic. Citation Format: Saskia Schmitt, Isabelle Mai, Paul Machui, Sarah Herterich, Danila Hauswald, Philipp Ochtrop, Philipp Cyprys, Izabela Kozlowska, Annabel Kitowski, Marcus Gerlach, Olivier Marcq, Pamela A. Trail, Dominik Schumacher, Marc-André Kasper, Günter Fingerle-Rowson, Björn Hock, Jonas Helma-Smets, Annette M. Vogl. Enabling 5T4 for targeted cancer therapy: TUB-030, a novel ADC built with ethynylphosphonamidate conjugation chemistry, shows long-lasting anti-tumor activity via Topoisomerase-I inhibition with an optimized therapeutic index [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2623.

Abstract 674: Novel anti-cancer small molecule targeting the protein regulator of cytokinesis pathway

Abstract Aberrant migration and proliferation of cancer cells are the hallmark of metastatic tumors. Protein Regulator of Cytokinesis 1 (PRC1) is a scaffold protein that regulates metabolic pathways of cancer cell proliferation, survival, and metastasis. BKT300 is a small molecule (MW 399.33, C22H25NO6), that selectively inhibits the migration and survival of hematological and solid cancer cells. BKT300 inhibits, at high affinity, both actin and microtubule formation and organization leading to G2/M cell cycle arrest, mitotic catastrophe, and apoptosis through the caspase 3 pathway. These effects are selective to cancer cells and were not observed on normal cells. BKT300 was found to arrest PRC1 in a phosphorylated form at position T481, down regulates the expression of CDC25C and up regulate p21. Suppression of PRC1 using SiRNA ablation inhibited BKT300 induced apoptosis on several tumor cell lines and inhibited the effect of BKT300 on G2M cell cycle arrest. Furthermore, using Biacore SPR, microscale thermophoresis (MST), and ELISA assays we were able to demonstrate the direct binding of BKT300 to PRC1. Beyond its single agent activity, BKT300 was shown to synergize with standard of care (SoC) treatments, including anti PD-1 immunotherapy, BCL-2 inhibitor (Ventoclax), topoisomerase I inhibitor (Irinotecan) topoisomerase II inhibitor (Doxorubicin), anti-metabolite Fluorouracil (5-FU) and alkylating agent (Temozolomide). BKT300 has a remarkable safety profile when administered at high doses to mice rats, minipigs and non-human primates. Treatment with BKT300 showed almost no effects on hematopoiesis and biochemistry in doses far higher than the affective ones. The in-vivo activity of BKT300 was demonstrated in multiple Xenograft, Syngeneic and PDX models in mice. In-vivo treatment with BKT300 resulted in preventive (small tumors) as well as therapeutic (large tumors) activity in triple negative breast cancer (TNBC) xenograft, MDA-MB-453 and MDA-MB-468 models leading to over then 70%-90% reduction in tumor size following one to two treatments cycles. Similar results were obtained using PDX models derived from patients with Colon, Ovarian and Pancreatic cancer. BKT300 is a novel, first in class, targeted anti-cancer treatment that inhibits the activity of the scaffold protein PRC1. BKT300 is expected to provide a new treatment option to, the high unmet medical need of, advanced difficult to treat cancers, specifically ones that overexpress PRC1 and CDC25C. Citation Format: Amnon Peled, Michal Abraham, Hanna Wald, Rakefet Rosenfeld, Orly Eizenberg, Arnon Aharon. Novel anti-cancer small molecule targeting the protein regulator of cytokinesis 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 674.

Abstract 2095: Peptide-based pivoting of p53 to target metastatic breast cancer

Abstract The inability to target distant metastases limits the treatment of late-stage cancers. At least in part, this is due to the lack of optimal targeted therapies and treatment resistance to the remaining standard of care consisting of chemo-/radio- therapy. Here, we show that cancer cells that are irreparably damaged can withstand cell death through a process we define as “scarring”. In scarred cells, p53 is phosphorylated at Ser46 and Ser392 and localizes into progressive multifocal leukemia (PML) nuclear bodies. We have identified scarring in over a quarter of metastatic breast, colon, stomach and ovarian cancer. Thus, pivoting scarred p53 towards cell death in scarred cancer could establish a novel broad-range therapeutic opportunity against metastatic cancer. Targeting p53 with small molecules has proven challenging. We developed cell-penetrating peptides that selectively bind scarred p53. One of our lead compounds, CL04177 dissociates p53 from its PML scaffold leading to its a nuclear exclusion and initiation of the transcription-independent mitochondrial apoptosis. To examine the role of scarring as a therapeutic target, we focused on triple-negative breast cancer (TNBC). TNBC cells are marked by the expression of p53 and PML compared to other breast cancer subtypes. In cytotoxicity experiments, CL04177 specifically targeted TNBC over other breast cancer subtypes. Further investigation into how this compound can target metastatic cells revealed that scarred features are upregulated in metastasis-initiating cells of organoids when induced to invade in contact with collagen and that CL04177 can induce apoptosis specifically in these invading strands. In vivo, CL04177 showed favorable pharmacokinetics and -dynamics and a clear safety profile. Importantly, when dosed at 10-fold below its Maximally Tolerated Dose, CL04177 strongly reduced primary tumor mass and metastatic dissemination to the liver of TNBC cell line-derived orthotopic xenografts. This data indicates a new concept of scarred p53 in cancer progression and metastasis. Moreover, peptides that release scarring markers from nuclear structures can eliminate aggressive cancers in vitro and, most importantly, in vivo, e.g., in p53-mutated, metastatic TNBC. This ability introduces a conceptually new therapeutic option, especially for types of cancer for which there is a high unmet medical need. Citation Format: Diana Putavet, Marjolein P. Baar, Johannes H. Lehmann, Antoine Khalil, Tao Shi, Thijs Koorman, Tobias B. Dansen, Patrick WB Derksen, Michael Teifel, Tobias Madl, Nicholas Sarlis. Peptide-based pivoting of p53 to target metastatic 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 2095.

Abstract 5924: RNAi mediated inhibition of beta-catenin demonstrates anti-tumor efficacy and immune microenvironment modulation in preclinical hepatocellular carcinoma models

Abstract Hepatocellular carcinoma (HCC) is the fifth most common solid tumor worldwide, and the third most common cause of cancer-related deaths. For the 40% to 50% of HCC patients who are candidates for systemic therapies, the landscape has evolved significantly in the last 10 years, with most recently, immunotherapies such as combination of atezolizumab and bevacizumab emerging as the current first-line systemic therapy for patients with intermediate or advanced disease. However, there are no predictive biomarkers for patients with HCC to enable selection of those most likely to benefit from these therapies and this remains a disease with high unmet medical need. Activation of the WNT pathway via mutational events or indirect pathway activation is implicated in many cancers including up to 50% of HCC patient tumors. High expression of beta-catenin, encoded by the CTNNB1 gene, has been shown to correlate with decreased survival and more rapid disease progression in HCC patients. In addition, WNT/beta-catenin pathway activation has been shown to result in immune exclusion and resistance to immunotherapy in HCC. ALN-BCAT comprises a chemically modified siRNA encapsulated in a lipid nanoparticle formulation which generates robust and highly specific reductions of CTNNB1 mRNA, downstream biomarkers and tumor cell proliferation in in vitro model systems. Anti-tumor activity has been demonstrated in multiple in vivo orthotopic HCC mouse models, in both early and late treatment settings as measured by liver to body weight ratio. Reductions in tumor burden were orthogonally confirmed by histology analysis and shown to be associated with changes in CTNNB1-related biomarkers. Finally, ALN-BCAT treatment results in changes in the tumor microenvironment in a mouse syngeneic HCC model, with increases in CD4+ and CD8+ T cells and reductions in M2 macrophages, consistent with a shift to a more immune stimulatory anti-tumor microenvironment. Here, we demonstrate that ALN-BCAT provides a novel approach to the inhibition of the WNT pathway as a therapeutic approach for treatment of HCC patients and WNT pathway activated tumors. Citation Format: Tulin Dadali, Spencer Miller, Gaurav Saawant, Stephen Abbott, Mikyung Yu, Svetlana Morskaya, Brandon Lehrich, Satdarshan Monga, Gloria Lau, Martin Maier, Wendy Broom. RNAi mediated inhibition of beta-catenin demonstrates anti-tumor efficacy and immune microenvironment modulation in preclinical hepatocellular carcinoma 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 5924.

Abstract 3124: MRG006A, a novel glypican-3-targeting antibody-drug conjugate, demonstrated potent anti-tumor activity and good safety profile in preclinical studies

Abstract Background: Hepatocellular carcinoma (HCC) is one of the most challenging cancers with high unmet medical need. Glypican-3 (GPC3) is an oncofetal glycoprotein anchored to the cell surface via GPI (glycosylphosphatidylinositol) and frequently over-expressed in HCC with limited expression in normal adult tissues, which makes it an appealing antibody-drug conjugate (ADC) target for HCC. MRG006A is a potentially first-in-class GPC3-targeting ADC composed of a novel humanized IgG1 antibody conjugated to a proprietary linker-payload platform utilizing a potent topoisomerase 1 inhibitor via a peptide-based cleavable linker. Materials and Methods: As a GPC3-targeting ADC intended for clinical therapy of GPC3-expressing cancers, the mechanism of action and therapeutic potential of MRG006A were investigated in a series of preclinical studies, including (1) MRG006A and its antibody moiety binding to human GPC3 expressed on cells assessed by flow cytometry; (2) binding affinity to human and cynomolgus monkey GPC3 measured by SPR (surface plasmon resonance); (3) internalization in Huh7 cells assessed by pHAb Reactive Dye and confocal microscopy; (4) in vitro cytotoxicity against a panel of HCC cell lines (Huh7, HepG2, Hep3B and GPC3-negative SK-HEP-1); (5) anti-tumor activity of MRG006A evaluated in Huh7 and HepG2 cell line-derived xenograft (CDX) as well as a panel of HCC patient-derived xenograft (PDX) mouse models with a different expression level of GPC3; (6) plasma stability of MRG006A evaluated in human, cynomolgus monkey, rat and mouse plasma; and (7) an exploratory pharmacokinetic (PK) and toxicology study of MRG006A in cynomolgus monkey. Results: The GPC3-targeting ADC, MRG006A, and its antibody moiety exhibited superior binding activity to GPC3-expressing cancer cell lines than a clinical antibody benchmark and similar nanomolar binding affinity to both human and cynomolgus monkey GPC3, which makes cynomolgus monkey suitable for toxicological studies. Rapid internalization of MRG006A antibody was observed in GPC3-expressing Huh7 cells, and MRG006A maintained comparable internalization capability to the naked antibody. More importantly, MRG006A exhibited potent GPC3-dependent cytotoxic activity in a panel of HCC cells expressing varying levels of GPC3. Administrations of MRG006A resulted in a robust and dose-dependent tumor growth inhibition of multiple CDX models and HCC PDX models. Remarkable stability of MRG006A was shown in the plasma of various species tested. MRG006A demonstrated a favorable PK and safety profile with good tolerability in the exploratory toxicology study. Conclusion: Overall, the preclinical study results suggest that MRG006A is a feasible ADC drug candidate for treating GPC3-expressing cancers in clinical studies. MRG006A was aimed to submit IND in China and the U.S in 2024. Citation Format: Yanchun Wang, Hongfeng Li, Hao Shen, Wenchao Liu, Shoujia Liu, Kequan Yin, Haili Xu, Xueyuan Cui, Wei Li, Wei Liu, Xiangyu Wu, Liu Yang, Tian Ma, Zhongrun Zhao, Jun Wang, Feifei Cui, Lei Fang, Minmin Qin, Chaohong Hu. MRG006A, a novel glypican-3-targeting antibody-drug conjugate, demonstrated potent anti-tumor activity and good safety profile in preclinical studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3124.

Abstract 514: Salt-inducible kinase inhibitor OMX-0407 drives cell-cycle arrest in vitro and in vivo: An in-depth MoA analysis by phospho-proteomics

Abstract Based on iOmx’ proprietary iOTargTM genetic screening platform, salt-inducible kinase (SIK) 3 was identified as a novel cell signaling modulator in cancer biology. OMX-0407, an orally available, spectrum-selective kinase inhibitor targets several members of the SIK family and is known to prevent tumor-promoting function of the SIK-family through repolarization of the tumor microenvironment by enhancing caspase-mediated apoptosis upon death-receptor signaling. In addition, OMX-0407 inhibits individual key members of the tyrosine and tyrosine-like kinase family that are involved in cancer cell proliferation and cell cycle regulation. Via this dual mode of action, OMX-0407 has the potential to effectively fight solid tumors as exemplified by its striking single-agent efficacy in multiple pre-clinical tumor models. A comprehensive anti-tumor viability screen of >200 human cancer cell lines revealed striking effects of OMX-0407 on cancer cell viability across various cancer indications, resulting in a distinct sensitivity profile across various tumor indications with particularly strong effects on renal cell carcinoma (RCC) and squamous non-small cell lung cancer (sqNSCLC). Phospho-proteomics screening demonstrated pharmacodynamic activity of OMX-0407 in sensitive tumor cell lines via inhibition of key cellular processes such as cell motility, proliferation, and cell cycle regulation across different indications. Orthogonal functional in vitro assays confirmed the association of the OMX-0407-mediated anti-tumor efficacy with the arrest of G1/S transition and corresponding downregulation of cell cycle associated proteins PAK1/2 and ARHGAP35. The profound impact of OMX-0407 on fundamental regulatory mechanisms of cell division and cancer cell apoptosis translates into dose-dependent single-agent, anti-tumor efficacy in various pre-clinical tumor models of selected indications. Combination with Axitinib, a selective orally available inhibitor of vascular endothelial growth factor receptor 2, significantly enhanced anti-tumor efficacy and pharmacodynamic inhibition of cell growth as well as angiogenesis. These data further strengthen the potential of OMX-0407 in the treatment of RCC as well as other indications. In summary, OMX-0407 is a novel spectrum selective kinase inhibitor, currently under evaluation in a clinical Phase I trial (NCT05826600). OMX-0407 demonstrates strong anti-tumor efficacy in monotherapy in selected sensitive indications through a dual-pronged MoA, by modulating the tumor microenvironment and exerting direct anti-tumor activity in solid tumor indications with high unmet medical need. Citation Format: Ilona-Petra Maser, Marisa Stebegg-Wagner, Bettina Bauer, Filippos Konstantinidis, Andreas Schirmer, Moritz Zulley, Sonja Lacher, Barbara Kracher, Parastou Kohvaei, Murray Yule, Hannes Loferer, Stefan Bissinger. Salt-inducible kinase inhibitor OMX-0407 drives cell-cycle arrest in vitro and in vivo: An in-depth MoA analysis by phospho-proteomics [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 514.

Abstract 1362: IOMX-0675, a LILRB1 and LILRB2 cross-specific antibody, effectively repolarizes immunosuppressive myeloid cells and activates T cells leading to potent tumor cell killing

Abstract Recently, myeloid checkpoints in the tumor microenvironment have gained increased attention in the context of tumor immune evasion. LILRB1 (ILT2) and LILRB2 (ILT4) are immunosuppressive receptors of the leukocyte immunoglobulin-like receptor (LILR) family that recognize both classical and non-classical MHC-I molecules (e.g., HLA-G). While tumor-infiltrating myeloid cells express both LILRB1 and LILRB2, lymphoid cells are restricted to LILRB1 expression. LILRB1 and LILRB2 are frequently co-expressed with immune-activating LILR family members LILRA1 and LILRA3 in several tumor indications and upregulated in patients non-responsive to T cell checkpoint blockade. Furthermore, the non-classical MHC-I molecule HLA-G, a major ligand of LILRB1 and LILRB2 in the tumor environment, is overexpressed and associated with poor prognosis in multiple solid cancer types. IOMX-0675, a fully human, Fc-silenced, monoclonal immunoglobulin G1 (IgG1) antibody with a highly differentiated binding profile, that binds selectively with high affinity to the inhibitory receptors LILRB1 and LILRB2, while binding only weakly to the closely related immune-activating LILR family members LILRA1 and LILRA3, was identified from iOmx’ proprietary phage display library. A high-resolution Fab-based Octet assay was established to monitor the IOMX-0675-mediated blocking of LILRB1 or LILRB2 binding to HLA-G. The LILRB1/2 cross-specific antibody promotes phagocytic and pro-inflammatory activity of various macrophage subtypes, which was monitored by flow cytometry and cytokine profiling. In co-cultures of monocyte-derived macrophages with autologous T cells, IOMX-0675 shows high potential to reprogram dose-dependently immunosuppressive macrophage, to further activate pro-inflammatory macrophage subtypes and thereby rescues the activity of the lymphoid immune compartment. Even in environments dominated by LILRA1/A3, IOMX-0675 shows a strong binding capacity to the immunosuppressive LILRB1/B2 receptors and significantly repolarizes the immune environment. In summary, we discovered IOMX-0675, a cross-specific antibody antagonizing both LILRB1 and LILRB2 with high selectivity, that exhibits potent reprogramming of the immunosuppressive myeloid compartment and restores cytotoxic T cell activity in the tumor microenvironment. Negligible binding to immune-activating LILR family members by IOMX-0675 could unleash full anti-tumor activity. The differential binding profile of IOMX-0675 provides best-in-class potential and may maximize anti-tumor efficacy for the benefit of patients with high-unmet medical need, who are resistant to T cell checkpoint blockade. Citation Format: Christina Hartl, Jonas Zantow, Ilona-Petra Maser, Marisa Stebegg-Wagner, Simone Friedrich, Jonas Schilz, Stefan Kaden, Ronny Milde, Eugenia Korotkova, Michail Maraslis, Bettina Langer, Michal Swiat, Carmen Ginzel, Carmen Ammerhauser, Lucille Albert, Leonie Majunke, Alina Huth, Kritika Sudan, Murray Yule, Christine Rothe, Hannes Loferer, Maximilian Aigner, Alexander N. Marziale, Stefan Bissinger. IOMX-0675, a LILRB1 and LILRB2 cross-specific antibody, effectively repolarizes immunosuppressive myeloid cells and activates T cells leading to potent tumor cell killing [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 1362.

Riboswitch-controlled IL-12 gene therapy reduces hepatocellular cancer in mice.

Hepatocellular carcinoma (HCC) and solid cancers with liver metastases are indications with high unmet medical need. Interleukin-12 (IL-12) is a proinflammatory cytokine with substantial anti-tumor properties, but its therapeutic potential has not been realized due to severe toxicity. Here, we show that orthotopic liver tumors in mice can be treated by targeting hepatocytes via systemic delivery of adeno-associated virus (AAV) vectors carrying the murine IL-12 gene. Controlled cytokine production was achieved in vivo by using the tetracycline-inducible K19 riboswitch. AAV-mediated expression of IL-12 led to STAT4 phosphorylation, interferon-γ (IFNγ) production, infiltration of T cells and, ultimately, tumor regression. By detailed analyses of efficacy and tolerability in healthy and tumor-bearing animals, we could define a safe and efficacious vector dose. As a potential clinical candidate, we characterized vectors carrying the human IL-12 (huIL-12) gene. In mice, bioactive human IL-12 was expressed in a vector dose-dependent manner and could be induced by tetracycline, suggesting tissue-specific AAV vectors with riboswitch-controlled expression of highly potent proinflammatory cytokines as an attractive approach for vector-based cancer immunotherapy.

Epidemiology and Real-World Treatment of Incident Diffuse Large B-cell Lymphoma (DLBCL): A German Claims Data Analysis.

The objective of this study was to investigate the prevalence, incidence, and treatment patterns (treatment regimens, switches, duration) for diffuse large B-cell lymphoma (DLBCL) in a real-world setting. This was a retrospective German claims data analysis of patients with DLBCL diagnosed between January 1, 2012, and December 31, 2020. The prevalence and cumulative incidence of DLBCL were found for 2019/2020. Line of treatment (LOT) and treatment setting from first DLBCL diagnosis to end of follow-up were described. Kaplan-Meier overall survival (OS) estimates since DLBCL diagnosis and start of treatment lines were calculated. Overall, 2633 incident DLBCL cases were identified (median age 75years, 51% male). Of these, 2119 patients received at least one DLBCL-related treatment (LOT1), and 1567 patients died during follow-up. In 2019/2020, the prevalence and cumulative incidence of DLBCL was 34.8/36.7 per 100,000 patients and 14.0/12.7 per 100,000 patients, respectively. For LOT1, 1922 patients were given a chemotherapy-based regimen (1530 with CD20 antibodies). A total of 403 patients were administered a second line (LOT2), of which 183 patients received a CD20 antibody-containing chemotherapy regimen and 100 patients received stem cell transplantation or chimeric antigen receptor (CAR)-T therapy. Of the 136 LOT3+ treatments, 74 were chemotherapy regimens (54 with CD20 antibodies) and 18 were kinase inhibitors. The median time between treatment lines was less than 6 months. Among patients with at least LOT2, approximately 50% received more than one LOT during the first year after diagnosis. Approximately 25% of treated patients died within 6months of treatment initiation. Of the 2633 included patients, the median OS from diagnosis was 31.0months (treated patients: 46.8months, untreated patients: 3.0months). Despite advances in the field, high unmet medical need in DLBCL remains. The treatment landscape is very heterogeneous, particularly in second- or later-line treatments, with few patients receiving potentially curative treatment beyond the first line. Treatment for DLBCL, particularly for transplant-ineligible patients, remains challenging.

Abstract B103: Development and characterisation of KRASmulti inhibitors for the treatment of KRAS mutant pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is predicted to become the second most common cause of cancer related death within the next decade. Late detection and limited therapeutic options drive the dismal prognosis for PDAC patients. Activating mutations within the KRAS gene occur within the vast majority (>85%) of PDAC tumors. KRAS mutations occur at an early stage within PDAC development but remain necessary for continued tumor growth. Clinical responses observed in patients with KRASG12C mutant PDAC treated with selective KRASG12C inhibitors have driven drug development programmes that can address other, more frequently occurring KRAS alleles. Here we report the characterization of a KRASmulti inhibitor, BI-2493, that potently inhibits the proliferation of mutant KRAS PDAC cancer cell lines in vitro. The DMPK properties of the compound have been optimized so that oral administration resulted in regression of KRAS mutant PDAC xenograft models. These data support the continued development of compounds capable of addressing the most prevalent KRAS mutant alleles in PDAC with the potential to provide a therapeutic option to patients in an indication with a high unmet medical need. Citation Format: Antonio Tedeschi, Otmar Schaaf, Michael Gmachl, Lorenz Herdeis, Francesca Rocchetti, Johannes Popow, Fiorella Schischlik, Daniel Gerlach, Jesse Lipp, Joachim Bröker, Andreas Mantoulidis, Chris Smethurst, Dirk Kessler, Jark Boettcher, Tobias Wunberg, Valeria Santoro, Alex Waterson, Jason Phan, Andrew Little, Jason Abbott, Qi Sun, Stephen Fesik, Darryl Mcconnell, Mark A. Pearson, Norbert Kraut, Dorothea Rudolph. Development and characterisation of KRASmulti inhibitors for the treatment of KRAS mutant pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B103.

Translational PK/PD for the Development of Novel Antibiotics-A Drug Developer's Perspective.

Antibiotic development traditionally involved large Phase 3 programs, preceded by Phase 2 studies. Recognizing the high unmet medical need for new antibiotics and, in some cases, challenges to conducting large clinical trials, regulators created a streamlined clinical development pathway in which a lean clinical efficacy dataset is complemented by nonclinical data as supportive evidence of efficacy. In this context, translational Pharmacokinetic/Pharmacodynamic (PK/PD) plays a key role and is a major contributor to a "robust" nonclinical package. The classical PK/PD index approach, proven successful for established classes of antibiotics, is at the core of recent antibiotic approvals and the current antibacterial PK/PD guidelines by regulators. Nevertheless, in the case of novel antibiotics with a novel Mechanism of Action (MoA), there is no prior experience with the PK/PD index approach as the basis for translating nonclinical efficacy to clinical outcome, and additional nonclinical studies and PK/PD analyses might be considered to increase confidence. In this review, we discuss the value and limitations of the classical PK/PD approach and present potential risk mitigation activities, including the introduction of a semi-mechanism-based PK/PD modeling approach. We propose a general nonclinical PK/PD package from which drug developers might choose the studies most relevant for each individual candidate in order to build up a "robust" nonclinical PK/PD understanding.

Abstract IA014: From targeted phenotypic screen to NXP800: A clinical stage activator of the integrated stress response for the treatment of ARID1A-mutated ovarian carcinoma

Abstract My presentation will describe our work on the discovery, nonclinical antitumor properties, mechanism of action (MOA), identification of initial target patient population, and early clinical development of NXP-800. We discovered this agent in our academic drug discovery centre at ICR following our initial identification of the ‘bisamide’ hit CCT245232 from a diverse ~200,000-compound library using an innovative, imaging-based (ArrayScan™) phenotypic screen for inhibitors of the HSF1-mediated activation of the heat shock response in U2OS human osteosarcoma cells. Subsequent multiparameter medicinal chemistry optimisation of the bisamide series, containing the N,N′-4-methyl-1,3-phenylenediamide core, focused on establishing the cell-based SAR for both inhibition of cell proliferation and linked HSF-1 mediated HSP72 induction in the sensitive ARID1A-mutant, platinum-resistant SK-OV-3 human ovarian carcinoma cell line. This generated our orally bioavailable, in vivo-active lead compound and chemical tool CCT251236 – exhibiting oral antitumor efficacy in the SK-OV-3 human ovarian cancer xenograft model in nude mice (Cheeseman et al J Med Chem 60 180-201 2017). Final multiparameter optimization yielded the clinical development candidate CCT361814/NXP800 (Pasqua et al J Med Chem 66 5907-36 2023). With the screening hit bisamide compound already active in the single to low double digit nanomolar range, the early focus was on improving kinetic solubility while retaining the desired antiproliferative and linked HSF1 pathway inhibitory activity together with simultaneous optimisation of PK/PD properties to maximize oral antitumour efficacy; finally requiring modification to the fluorobisamide NXP800 to eliminate PGP-mediated efflux and achieve optimal PK/PD, Pharmacologic Audit Trail, antitumor efficacy and tolerability. In view of these properties, its clean safety panel profile, clear therapeutic index and acceptable dose-to-human prediction, NXP800 was progressed into clinical development. Evaluation in a mini-panel of human cancer cell lines and tumor xenografts revealed high sensitivity to NXP800 in ARIDIA-deficient human ovarian cancer models, confirmed in the large Sanger cancer cell line panel and in isogenic pair systems. Activity exceeded that of cisplatin in both platinum-sensitive and platinum-resistant ARID1A-mutant ovarian cancer xenograft models. By RNA-Seq we identified two sets of consistent, major gene expression profile changes in human cancer cell lines exposed to NXP800, namely: 1) the expected changes in HSF1-regulated genes, together with 2) activation of the integrated stress response (ISR), including ATF4-regulated gene expression. This latter did not indicate a global stress response to NXP800 as we saw no activation of the unfolded protein response (UPR). Physiologically, ISR activation is mediated by phosphorylation of EIF2α which is tightly regulated by four stress-controlled kinases, GCN2, HRI, PKR and PERK. Using each of systematic siRNA knockdown or pharmacologic inhibition by two small-molecule tool compounds from different chemotypes, we discovered that GCN2 alone was necessary and sufficient for ISR activation and cell growth inhibition by NXP800 in SK-OV-3 ovarian cancer cells. Also, orthogonal siRNA depletion or pharmacologic inhibition of GCN2 both markedly reduced the antiproliferative activity of NXP800 in these cells. Global phospho-proteome analysis demonstrated defined changes in response to NXP800 which were reversed by co-treatment with a GCN2 inhibitor. Other follow-on studies at the protein level demonstrated that pharmacological concentrations of NXP800 induced GCN2-dependent phosphorylation of EIF2α, inhibition of global cap-dependent protein translation, and selective translation of ATF4 – a transcription factor that activates downstream genes such as CHAC1 and CHOP in the ISR – both in ARID1A-mutant human ovarian cells in vitro and in corresponding tumor xenograft models in vivo. Using siRNA silencing, we showed that prevention of ATF4 induction substantially reduced the antiproliferative response of SK-OV-3 human ovarian carcinoma cells to NXP800 treatment. Controls used in these experiments included a closely matched, inactive regioisomer. Furthermore, we showed that ISR induction by NXP800 inhibited HSF1 activation, in SK-OV-3 cells, confirming the mechanistic link between ISR activation and inhibition of HSF1-mediated transcription. We further showed that GCN2 activation was not due to the canonical mechanism of amino acid starvation. In summary, we used an HSF1 pathway-focused phenotypic screen to discover the mechanistically novel, first-in-class drug NXP800, which acts potently on ARID1A-mutant, human ovarian cancer cells to stimulate GCN2 and thereby activate the ISR pathway, leading to ATF4 induction and inhibition of HSF1-mediated gene transcription in ARID1A-mutant, platinum-resistant human ovarian cancer cells. Through this mechanism, NXP800 shows highly promising activity in models of this cancer type, including potent inhibition of proliferation in vitro and substantial regression of tumor xenografts in vivo. Studies are currently underway to determine precisely how NXP800 stimulates GCN2 activity and the role of ARID1A deficiency in its pharmacological effects. Recent ChIP-Seq studies are informing on the molecular interactions between ARID1A mutation and the expression of ISR/ATF4 and HSF1-regulated genes. With Nuvectis Pharma, the Phase 1a dose escalation study has been completed and a multicentre Phase 1b expansion cohort study in ARID1A-mutated, platinum-resistant ovarian cancer – a high unmet medical need – has been initiated (NCT05226507) in collaboration with the GOG Foundation and the European Network of Gynaecological Oncological Trial Group (ENGOT). FDA has issued a Fast Track designation to NXP800 in this setting. In addition, NXP800 shows therapeutic potential in non-clinical models of endometrial, gastro-intestinal and bile duct cancer, with FDA Orphan Drug status granted in the last of these indications. Citation Format: Paul Workman. From targeted phenotypic screen to NXP800: A clinical stage activator of the integrated stress response for the treatment of ARID1A-mutated ovarian carcinoma [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr IA014.

Abstract A007: Preclinical bone metastasis technology platform – Predictive evaluation of experimental therapies on bone metastasis

Abstract Most cancer deaths are due to metastases, and bone metastases are a considerable problem especially in breast and prostate cancer, being developed in 70-90% of advanced-stage patients. Despite major investments in oncology drug development, bone metastases are currently incurable and a high unmet medical need with only 5% of patients being alive 5 years after the diagnosis. Development of therapies for bone metastasis has been challenging due to lack of appropriate preclinical models available to support decision making in next phases of drug development. In the absence of clinically relevant preclinical bone metastasis models, the current strategy is to rely on preclinical efficacy data obtained with subcutaneous models that lack the clinically relevant local tissue microenvironment, which has a major impact on tumor growth. The use of clinically non-relevant models in preclinical-stage development may be one important reason for the current >95% failure rate of oncology drugs in clinical trials. To support predictive evaluation of therapies for bone metastatic cancers, we describe a preclinical bone metastasis technology platform for evaluating efficacy of novel therapies on bone metastases. The platform utilizes tumors growing in bone microenvironment, mimicking growth of bone metastases in patients. Syngeneic or humanized mouse models with tumor and immune cells of same species are needed for supporting development of immunotherapies, allowing interactions of tumor and immune cells in the bone metastatic microenvironment, according to the novel osteoimmuno-oncology concept. The platform provides a predictive tool for studying unique biological features associated with different types of bone metastases in cancer-type specific manner. Here we summarize case examples where results from preclinical bone metastasis studies align with clinical findings of different therapies approved or evaluated for bone metastasis. Zoledronic acid, an anti-resorptive bisphosphonate that is currently used in breast cancer patients with bone metastases to prevent cancer-induced bone loss, showed improved bone health but no effects on tumor growth. Radium-223 dichloride, an approved treatment for bone metastatic castration-resistant prostate cancer in patients, showed reduced prostate cancer growth and decreased tumor-induced bone changes. As for immunotherapies, an IDO1 inhibitor had no effects on breast cancer bone metastases and the anti-PD-1 antibody pembrolizumab had no effects on breast and prostate cancer bone metastases, predicting recent clinical findings that demonstrate lack of efficacy of anti-PD-1 in clinical prostate cancer trials. We conclude that the bone metastasis technology platform is a biologically relevant tool for preclinical evaluation of the efficacy of experimental therapies on bone metastasis, and it has been validated with positive and negative case examples, demonstrating its clinically predictive power. Citation Format: Tiina E Kähkönen, Jussi M Halleen, Jenni Bernoulli. Preclinical bone metastasis technology platform – Predictive evaluation of experimental therapies on bone metastasis [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A007.