Strong Antitumor Activity Research Articles

OS08.7.A Lomustine and the immunocytokine L19TNF are a promising treatment combination for recurrent glioblastoma

Abstract Background Treatment options for recurrent glioblastoma are limited and with the possible exception of regorafenib, no agent has demonstrated superior activity to lomustine. Therefore, there is an urgent need for more effective treatment strategies for recurrent glioblastoma. Here, we investigated different treatment combinations based on the tumor-stroma targeting antibody-cytokine fusion protein L19TNF in preclinical glioma models and translated the most effective treatment combination to patients with recurrent glioblastoma. Material and Methods Orthotopic immunocompetent mouse glioma models were used to study the anti-glioma activity of L19TNF in combination with anti-PD1, bevacizumab or lomustine. Tumor growth was monitored by MRI. Flow cytometry and microscopy were used to characterize tumor-infiltrating-immune cells. MHC immunoaffinity purification and mass spectrometry were used to characterize the MHC immunopeptidome. Genetic mouse models were used to study immune-dependent effects. Subsequently, we translated the most efficient treatment combination to patients with recurrent glioblastoma within a phase I/II clinical trial (NCT04573192). Results The combination of L19TNF and lomustine demonstrated strong synergistic anti-tumor activity in two immunocompetent orthotopic glioma models and cured a majority of tumor-bearing mice. In contrast, combinations with anti-PD-1 or bevacizumab had only limited anti-glioma activity. Furthermore, compared to the monotherapies, the combination of L19TNF and lomustine led to the strongest increase in tumor-infiltrating lymphoid cells as demonstrated by flow cytometry and microsopy and to the highest number of peptides presented in the context of MHC-I. The treatment effect was abrograted in different genetic immunodeficient mouse models. The treatment combination of L19TNF and lomustine was well tolerated in the first patients treated within a phase I/II clinical trial and we observed partial tumor responses also in patients with an unmethylated MGMT promoter. Conclusion The combination of L19TNF and lomustine demonstrated promising anti-glioma activity and patients are currently recruited within a phase I/II clinical trial for patients with recurrent glioblastoma.

EP08.02-029 Sunvozertinib in NSCLC Patients with EGFR Exon20 Insertion Mutations: Effect of Prior Treatment

While platinum-based chemotherapy is the standard of care for the 1st line treatment of NSCLC with EGFR Exon20 insertion (Exon20ins) mutations, there is no consensus for further treatment once disease progresses. EGFR TKIs, anti-PD(L)1, anti-angiogenesis, among others, are frequently used. Sunvozertinib is a rationally designed EGFR Exon20ins inhibitor with wildtype selectivity. Results from the ongoing phase 1/2 studies showed sunvozertinib’s strong anti-tumor activity and benign safety profile.

617O Lemzoparlimab, a differentiated anti-CD47 monoclonal antibody, in combination with azacitidine (AZA) in patients with newly diagnosed higher risk myelodysplastic syndrome (HR-MDS): Initial clinical results

Lemzoparlimab (TJ011133) is a differentiated CD47 antibody targeting a distinct epitope to enable a unique red blood cell sparing property while retaining strong anti-tumor activity. We report initial data in an ongoing phase 2 trial in HR-MDS (NCT04202003).

Dual drug loaded polyhydroxy butyric acid/gelatin nanofibrous scaffold for possible post-surgery cancer treatment

The design of nanofibrous scaffold with dual-drugs have gained much interest for treatment of tissue defect after the post-surgery cancer site. Herein, we report the electrospinning of poly (3-hydroxybutyric acid) (P) and gelatin (G) nanofibrous scaffold with incorporation of 5-flurouracil (FU) (hydrophilic) and methotrexate (MT) (hydrophobic) as a dual-drug carrier to impart synergetic effect at post-surgery cancer site. The surface morphology of the nanofibrous scaffold were examined at different magnification. The in vitro release results demonstrated the sustained release over the period of 96 h. The in vitro cell cytotoxicity and fluorescent images of live and dead cells clearly exhibited strong antitumor activity against MCF-7 and MIA PaCa-2 cells. Moreover, both hydrophilic and hydrophobic drug showed a reasonable burst release from the scaffold. Thus, the nanofibrous scaffold could be a versatile system for the delivery of dual-drugs and as an implantable scaffold for post-surgery cancer treatment.

Lisaftoclax (APG-2575) Is a Novel BCL-2 Inhibitor with Robust Antitumor Activity in Preclinical Models of Hematologic Malignancy.

Development of B-cell lymphoma 2 (BCL-2)-specific inhibitors poses unique challenges in drug design because of BCL-2 homology domain 3 (BH3) shared homology between BCL-2 family members and the shallow surface of their protein-protein interactions. We report herein discovery and extensive preclinical investigation of lisaftoclax (APG-2575). Computational modeling was used to design "lead" compounds. Biochemical binding, mitochondrial BH3 profiling, and cell-based viability or apoptosis assays were used to determine the selectivity and potency of BCL-2 inhibitor lisaftoclax. The antitumor effects of lisaftoclax were also evaluated in several xenograft models. Lisaftoclax selectively binds BCL-2 (Ki < 0.1 nmol/L), disrupts BCL-2:BIM complexes, and compromises mitochondrial outer membrane potential, culminating in BAX/BAK-dependent, caspase-mediated apoptosis. Lisaftoclax exerted strong antitumor activity in hematologic cancer cell lines and tumor cells from patients with chronic lymphocytic leukemia, multiple myeloma, or Waldenström macroglobulinemia. After lisaftoclax treatment, prodeath proteins BCL-2‒like protein 11 (BIM) and Noxa increased, and BIM translocated from cytosol to mitochondria. Consistent with these apoptotic activities, lisaftoclax entered malignant cells rapidly, reached plateau in 2 hours, and significantly downregulated mitochondrial respiratory function and ATP production. Furthermore, lisaftoclax inhibited tumor growth in xenograft models, correlating with caspase activation, poly (ADP-ribose) polymerase 1 cleavage, and pharmacokinetics of the compound. Lisaftoclax combined with rituximab or bendamustine/rituximab enhanced antitumor activity in vivo. These findings demonstrate that lisaftoclax is a novel, orally bioavailable BH3 mimetic BCL-2-selective inhibitor with considerable potential for the treatment of certain hematologic malignancies.

Discovery of 1,2-diphenylethene derivatives as human DNA topoisomerase II catalytic inhibitors and antitumor agents

Human DNA topoisomerase II (TopoII) is highly correlated with cell proliferation, and involved in tumor biogenesis and development. The classic chemotherapeutic agents etoposide (VP-16) and adriamycin (ADR) targeting TopoII are wildly used in clinical applications. Herein, fifty-eight pinosylvin (1,2-diphenylethene) derivatives as TopoII inhibitors were designed and synthesized through three generations of structural optimizations on the basis of the structure of the initial hit A1 from in-house chemical library. The most potent compound F2 showed high in vitro inhibitory efficacy against TopoII (IC50 α 3.8, β 10.1 μM), compared to that of VP-16 (IC50 α 110.0, β 36.1 μM) for pBR322 DNA relaxation with no evident TopoII poisons in DNA cleavage assay. Meanwhile, F2 exhibited strong antitumor activities against human cancer cell lines HeLa, HCT-116, PC-3, MDA-MB-231, HepG2 and A549 (IC50 0.1–0.3 μM), compared to that of VP-16 (IC50 1.5–15.1 μM). F2 showed less cytotoxicity against normal murine cell line CCL-226 (IC50 > 50 μM) than that of VP-16 (IC50 20.8 μM). The selectivity index of F2 and VP-16 are larger than 52.1 and 1.3–26.2 in cell lines, respectively. Additionally, F2 exhibited potent potency in apoptosis induction and cell cycle arrest in HepG2 cells. These results provide a promising strategy and good starting point for the development of potent TopoII inhibitors as antitumor agents.

Anlotinib exerts potent antileukemic activities in Ph chromosome negative and positive B-cell acute lymphoblastic leukemia via perturbation of PI3K/AKT/mTOR pathway

ObjectivesDespite advances in the development of novel targeted therapies, the need for B-ALL alternative treatments has not been met. Anlotinib could blunt the proangiogenic activity of VEGFR, PDGFR, and FGFR, and has shown strong antitumor activities across multiple tumors. However, anlotinib cytotoxicity against B-ALL has not ever been evaluated, thus prompting us to initiate this study. MethodsExpression2Kinases program was used to identify potential treatment targets. Cell viability and apoptosis were determined by CCK-8 and Annexin V/PI staining kit, respectively. qRT-PCR and Western blotting were utilized to investigate the molecular mechanisms. In vivo antileukemia activity of Anlotinib was evaluated in a Ph+ B-ALL patient-Derived Xenograft (PDX) model. ResultsCompared with treatment-naive B-ALL cases, RR B-ALL patients had higher activities in the VEGF/VEGFR signaling and the PI3K/AKT/mTOR pathway. Exposure of Ph− and Ph+ B-ALL cells to anlotinib resulted in significant cell viability reduction, apoptosis enhancement, and cell cycle arrest at G2/M phase. Importantly, anlotinib treatment led to remarkably decreased leukemia burdens and extended the survival period in a Ph+ B-ALL PDX model. Blockade of the role of the proangiogenic mediators, comprising VEGFR2, PDGFR-beta, and FGFR3, played a critical role in the cytotoxicity of anlotinib against Ph− and Ph+ B-ALL. Moreover, anlotinib dampened the activity of PI3K/AKT/mTOR pathway that resides in the convergence of the three mentioned proangiogenic signals. ConclusionThis work provides impressive preclinical evidence of anlotinib against Ph− and Ph+ B-ALL and raises a rationale for future clinical evaluation of this drug in the management of Ph− and Ph+ B-ALL.

Synthetic oleanane triterpenoid derivative CDDO-Me disrupts cellular bioenergetics to suppress pancreatic ductal adenocarcinoma via targeting SLC1A5.

To investigate the potential antitumor activity of synthetic triterpenoid, methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate(CDDO-Me) in pancreatic ductal adenocarcinoma (PDAC), MTT cytotoxicity assay, and xenograft nude mice assay were performed to evaluate tumor growth in vitro and in vivo. Seahorse XFe96 bioenergetics analyzer was applied to determine aerobic glycolysis and mitochondrial respiration. Western blot and quantitative reverse transcription-polymerase chain reactions areused to detect protein and messenger RNA transcripts of SLC1A5 and metabolic enzymes. We confirmed the strong antitumor activity of CDDO-Me in suppressing PDAC growth. Mechanistically, we demonstrated CDDO-Me induced mitochondrial respiration and aerobic glycolysis dysfunction. We also verified CDDO-Me downregulated glutamine transporter SLC1A5, resulting in excessive reactive oxygen species(ROS) levels that suppressed tumor growth. Moreover, we confirmed thatSLC1A5 depletion reduced the ratio of glutathione/oxidized glutathione.We also found CDDO-Me could inhibit N-linked glycosylation of SLC1A5, which promotes protease-mediated degradation. Finally, we confirmed SLC1A5 was significantly overexpressed in PDAC and closely correlated with the poor prognosis of PDAC patients. Our work uncovers CDDO-Me is effective at suppressing PDAC cell growth in vitro and in vivo and illuminates CDDO-Me caused excessive ROS and cellular bioenergetics disruption which contributed to CDDO-Me inhibited PDAC growth. Our data highlights CDDO-Me could be considered a potential compound for PDAC therapy, and SLC1A5 could be a novel biomarker for PDAC patients.

BRD4 Inhibitor GNE-987 Exerts Anticancer Effects by Targeting Super-Enhancer-Related Gene LYL1 in Acute Myeloid Leukemia.

Background AML (acute myeloid leukemia) is a common hematological malignancy in children with poor treatment effects and poor prognosis. Recent studies have shown that as a novel BRD4 (bromodomain containing 4) PROTACs (proteolysis targeting chimeras) degrader, GNE-987 can slow down the growth of various tumors and increase apoptosis, with promising clinical prospects. However, the function and molecular mechanism of GNE-987 in AML remain unclear. This study is aimed at investigating the therapeutic effect of GNE-987 on AML and its underlying mechanism. Methods The association between BRD4 and AML was assessed by studying public databases. After GNE-987 was added to AML cells, cell proliferation slowed down, the cycle was disturbed, and apoptosis increased. Western blotting was used to detect BRD2 (bromodomain containing 2), BRD3 (bromodomain containing 3), BRD4, and PARP (poly ADP-ribose polymerase) proteins. The effect of GNE-987 on AML cells was analyzed in vivo. RNA-seq (RNA sequencing) and ChIP-seq (chromatin immunoprecipitation sequencing) validated the function and molecular pathways of GNE-987 in processing AML. Results BRD4 expression was significantly elevated in pediatric AML samples compared with healthy donors. GNE-987 inhibited AML cell proliferation by inhibiting the cell cycle and inducing apoptosis. BRD2, BRD3, and BRD4 were consistent with decreased VHL (Von Hippel Lindau) expression in AML cells. In an AML xenograft model, GNE-987 significantly reduced the hepatosplenic infiltration of leukemia cells and increased the mouse survival time. Based on analysis of RNA-seq and ChIP-seq analyses, GNE-987 could target multiple SE- (super-enhancer-) related genes, including LYL1 (lymphoblastic leukemia 1), to inhibit AML. Conclusions GNE-987 had strong antitumor activity in AML. GNE-987 could effectively inhibit the expression of SE-related oncogenes including LYL1 in AML. Our results suggested that GNE-987 had broad prospects in the treatment of AML.

Targeting the extra domain A of fibronectin for cancer therapy with CAR-T cells

BackgroundOne of the main difficulties of adoptive cell therapies with chimeric antigen receptor (CAR)-T cells in solid tumors is the identification of specific target antigens. The tumor microenvironment can present...

LIGHT (TNFSF14) Costimulation Enhances Myeloid Cell Activation and Antitumor Immunity in the Setting of PD-1/PD-L1 and TIGIT Checkpoint Blockade.

Coinhibition of TIGIT (T cell immunoreceptor with Ig and ITIM domains) and PD-1/PD-L1 (PD-1/L1) may improve response rates compared with monotherapy PD-1/L1 blockade in checkpoint naive non-small cell lung cancer with PD-L1 expression >50%. TIGIT mAbs with an effector-competent Fc can induce myeloid cell activation, and some have demonstrated effector T cell depletion, which carries a clinical liability of unknown significance. TIGIT Ab blockade translates to antitumor activity by enabling PVR signaling through CD226 (DNAM-1), which can be directly inhibited by PD-1. Furthermore, DNAM-1 is downregulated on tumor-infiltrating lymphocytes (TILs) in advanced and checkpoint inhibition-resistant cancers. Therefore, broadening clinical responses from TIGIT blockade into PD-L1low or checkpoint inhibition-resistant tumors, may be induced by immune costimulation that operates independently from PD-1/L1 inhibition. TNFSF14 (LIGHT) was identified through genomic screens, in vitro functional analysis, and immune profiling of TILs as a TNF ligand that could provide broad immune activation. Accordingly, murine and human bifunctional fusion proteins were engineered linking the extracellular domain of TIGIT to the extracellular domain of LIGHT, yielding TIGIT-Fc-LIGHT. TIGIT competitively inhibited binding to all PVR ligands. LIGHT directly activated myeloid cells through interactions with LTβR (lymphotoxin β receptor), without the requirement for a competent Fc domain to engage Fcγ receptors. LIGHT costimulated CD8+ T and NK cells through HVEM (herpes virus entry mediator A). Importantly, HVEM was more widely expressed than DNAM-1 on T memory stem cells and TILs across a range of tumor types. Taken together, the mechanisms of TIGIT-Fc-LIGHT promoted strong antitumor activity in preclinical tumor models of primary and acquired resistance to PD-1 blockade, suggesting that immune costimulation mediated by LIGHT may broaden the clinical utility of TIGIT blockade.

Pharmacologic screen identifies active combinations with BET inhibitors and LRRK2 as a novel putative target in lymphoma.

Inhibitors of the Bromo‐ and Extra‐Terminal domain (BET) family proteins have strong preclinical antitumor activity in multiple tumor models, including lymphomas. Limited single‐agent activity has been reported in the clinical setting. Here, we have performed a pharmacological screening to identify compounds that can increase the antitumor activity of BET inhibitors in lymphomas.The germinal center B‐cell like diffuse large B‐cell lymphoma (DLBCL) cell lines OCI‐LY‐19 and WSU‐DLCL2 were exposed to 348 compounds given as single agents at two different concentrations and in combination with the BET inhibitor birabresib. The combination partners included small molecules targeting important biologic pathways such as PI3K/AKT/MAPK signaling and apoptosis, approved anticancer agents, kinase inhibitors, epigenetic compounds. The screening identified a series of compounds leading to a stronger antiproliferative activity when given in combination than as single agents: the histone deacetylase (HDAC) inhibitors panobinostat and dacinostat, the mTOR (mechanistic target of rapamycin) inhibitor everolimus, the ABL/SRC (ABL proto‐oncogene/SRC proto oncogene) inhibitor dasatinib, the AKT1/2/3 inhibitor MK‐2206, the JAK2 inhibitor TG101209. The novel finding was the benefit given by the addition of the LRRK2 inhibitor LRRK2‐IN‐1, which was validated in vitro and in vivo. Genetic silencing demonstrated that LRRK2 sustains the proliferation of lymphoma cells, a finding paired with the association between high expression levels and inferior outcome in DLBCL patients.We identified combinations that can improve the response to BET inhibitors in lymphomas, and LRRK2 as a gene essential for lymphomas and as putative novel target for this type of tumors.

Ultrasonic Extraction and Separation of Taxanes from Taxus cuspidata Optimized by Response Surface Methodology

Taxanes are natural compounds with strong antitumor activity. In this study, we first extracted taxanes from the needles of Taxus cuspidata using ultrasonic (US) extraction, and then assessed the effects of different extraction conditions on the yields of eight target compounds. Response surface methodology (RSM) was further used to optimize the extraction conditions: when the liquid-to-solid ratio was 20.88 times, ultrasonic power was 140.00 W, ultrasonic time was 47.63 min, and ethanol content in solvent was 83.50%, taxane yields reached the maximum value of 354.28 μg/g. Under these conditions, the actual extraction rate of taxanes from the needles was 342.27 μg/g. The scanning electron microscopy (SEM) results indicated that the morphology of the needles, suspension cells, and callus of Taxus cuspidata extracted by ultrasonic wave had changed, the pores of the sections of the needles extracted by ultrasonic wave had become relatively loose, and the pore diameter had obviously increased. The callus and overall structure of the suspension cells extracted by ultrasonic wave were destroyed, forming cell fragments. The components of Taxus cuspidata are complex; the high-performance liquid chromatography (HPLC) method established in this paper is suitable for the rapid and effective separation of taxanes in Taxus cuspidata. We systematically and comprehensively compared the yields of taxanes in needles, callus, and suspension cells of Taxus cuspidata, and the taxane yields were increased by the suspension cell culture.

Panoramic comparison between NK cells in healthy and cancerous liver through single-cell RNA sequencing.

Objective:NK cells play crucial roles in the immune defense mechanisms against viral infections and transformed cells. However, the developmental progression, transcriptomic landscape, and functional subtypes of liver NK cells are not well defined. Hepatocellular carcinoma (HCC) accounts for approximately 80% of primary liver cancer worldwide, yet the biological characteristics of NK cells in the HCC environment are unclear. Therefore, we aimed to determine these cells’ roles in tumorigenesis and prognosis.Methods:We compared the single-cell RNA sequencing profiles of NK cells purified from blood (n = 1), healthy liver tissues (n = 3), HCC tumor tissues (n = 4), and peritumor liver tissues (n = 1) to identify NK cell subsets. Furthermore, we performed bioinformatics analysis by using The Cancer Genome Atlas (TCGA) data to identify prognostic biomarkers simultaneously overexpressed in the blood and tumor tissues of patients with HCC.Results:Transcriptomic analysis revealed 5 NK cell subsets (L1-NK-CD56bright, L2-NK-CD56dim, L3-NK-HLA, L4-LrNK-FCGR3A, and L5-LrNK-XCL1) in the healthy liver tissues. However, the transitional L3 subset and the CXCR6+CD16+ L4 subset with strong anti-tumor activity were absent in the HCC and peritumor liver tissues. Furthermore, 4 common prognosis-associated genes (RHOB, TALDO1, HLA-DPA1, and TKT) were significantly overexpressed in the paired tumor tissue and blood.Conclusions:Our study revealed 5 specific subsets of NK cells in healthy human liver tissues. However, only 3 of the 5 NK cell subsets were present in HCC and peritumor tissues. The cytotoxic NK cell subsets were absent in HCC tissues. Furthermore, we identified 4 potential non-invasive prognostic biomarkers in patients with HCC.

Novel chlorpromazine derivatives as anti-endometrial carcinoma agents with reduced extrapyramidal side effects

As the traditional conservative remedy for endometrial carcinoma (EC), progesterone has great limitations due to its poor performance, and a new strategy is urgently needed. Our previous work revealed that the antipsychotic drug chlorpromazine (CPZ) has stronger antitumor activity on EC than progesterone does, which may provide a promising conservative alternative for EC patients. Unfortunately, the severe extrapyramidal symptoms (EPSs) at concentrations (>5 mg/kg) that are required for anticarcinoma activity limited its repurposing. Therefore, a series of novel CPZ derivatives were designed and synthesized to avoid EPS and retain its antitumor activity. Among them, 11·2HCl and 18 displayed greater inhibitory activity by modulating SOS1. Notably, even at a dose of 100 mg/kg, 11·2HCl/18 had little effect on the extrapyramidal system. In conclusion, 11·2HCl and 18 greatly repressed the malignant features of endometrial carcinoma and decreased extrapyramidal side effects compared with the original drug CPZ.

Combination of T-DM1 and platinum-based chemotherapy in patient-derived xenograft models of muscle-invasive bladder cancer.

Objective(s):To assess the efficacy and safety of T-DM1, as an anti-HER2 antibody-drug conjugate (ADC), alone and in combination with two platinum-based chemotherapy regimens in patient-derived xenografts (PDXs) of muscle-invasive bladder cancer (MIBC) established in immunodeficient mice. Materials and Methods:After treatment initiation, tumor size was measured twice a week. Percent of tumor growth inhibition (TGI) and tumor response rates were calculated as efficacy endpoints. To evaluate treatment toxicity, relative body weight (RBW) was calculated for each group. For comparison of TGIs between treatment groups, the Kruskal-Wallis test was used. Also, the significance of the overall response (OR) rate between placebo groups with treatment groups was analyzed using Fisher’s exact test. Immunohistochemistry and fluorescence in situ hybridization techniques were used to evaluate the level of HER2 expression.Results:Our data showed that T-DM1 alone induced a moderate antitumor activity. While chemotherapy regimens induced a slight TGI when administered alone, interestingly, they showed strong antitumor activity when administered combined with T-DM1. The OR rates were higher when T-DM1 was combined with chemotherapy regimens than T-DM1 alone. When compared with the placebo group, the OR rates of combination groups were statistically significant. Our data also showed that the administered dose of each drug was well tolerated in mice. Conclusion:The combination of T-DM1 and platinum-based chemotherapy may represent a new treatment option for bladder tumors with even low HER2 expression, and could also provide substantial novel insight into tackling the challenges of MIBC management.

Magnetic reduced graphene oxide (MrGO) nanocomposites as nano carries for loading and transferring of 10-hydroxycamptothecin

10-hydroxycamptothecin (HCPT) is a natural alkaloid which has strong antitumor activity by inhibiting the degradation of the cleaved DNA strand. As a rich plasma protein, human serum albumin is a medium for transporting of various drugs and endogenous compounds. Due to its high water dispensability and good biocompatibility, reduced graphene oxide (rGO) is an eminent candidate for delivery of medicinal molecules. In cancer therapy, ferrosoferric oxide (Fe3O4) could be used to improve the therapeutic action and the imaging-guided delivery. In this work, Fe3O4 was anchored onto rGO nanosheets, and the formed Fe3O4/rGO nanocomposite showed efficient tumor targeting. The binding interaction between HCPT with HSA was investigated and the magnetic reduced graphene oxide (MrGO) had strong effect on the binding interaction. The comet assay results showed that MrGO had low toxicity, and the main binding forces between HCPT and HSA or HSA-HCPT were hydrogen bond and van der Waals force. In addition, it was found that the added MrGO greatly enhanced the binding of HCPT with HSA. The results offer some insight on the interaction between nanomaterials loaded with medicinal molecules and serum albumin at a molecular level.

Inhibition of HSP 90 is associated with potent anti-tumor activity in Papillary Renal Cell Carcinoma

BackgroundThere is no universally accepted treatment for patients with advanced papillary renal cell carcinoma (PRCC). The presence of activating mutations in MET, as well as gain of chromosome 7, where the MET gene is located, are the most common genetic alterations associated with PRCC, leading to the clinical evaluation of MET tyrosine kinase inhibitors (TKIs) in this cancer. However, TKIs targeting MET selectively, as well as multitargeted TKIs with activity against MET demonstrate modest efficacy in PRCC and primary and secondary treatment failure is common; other approaches are urgently needed to improve outcomes in these patients.MethodsHigh throughput screening with small molecule libraries identified HSP90 inhibitors as agents of interest based on antitumor activity against patient derived PRCC cell lines. We investigated the activity of the orally available HSP90 inhibitor, SNX2112 in vitro, using 2D/3D PRCC cell culture models and in vivo, in mice tumor xenograft models. The molecular pathways mediating antitumor activity of SNX2112 were assessed by Western blot analysis, Flow cytometry, RNA-seq analysis, Real Time qPCR and imaging approaches.ResultsSNX2112 significantly inhibited cellular proliferation, induced G2/M cell cycle arrest and apoptosis in PRCC lines overexpressing MET. In contrast to TKIs targeting MET, SNX2112 inhibited both MET and known downstream mediators of MET activity (AKT, pAKT1/2 and pERK1/2) in PRCC cell lines. RNAi silencing of AKT1/2 or ERK1/2 expression significantly inhibited growth in PRCC cells. Furthermore, SNX2112 inhibited a unique set of E2F and MYC targets and G2M-associated genes. Interestingly, interrogation of the TCGA papillary RCC cohort revealed that these genes were overexpressed in PRCC and portend a poor prognosis. Finally, SNX-2112 demonstrated strong antitumor activity in vivo and prolonged survival of mice bearing human PRCC xenograft.ConclusionsThese results demonstrate that HSP90 inhibition is associated with potent activity in PRCC, and implicate the PI3K/AKT and MEK/ERK1/2 pathways as important mediators of tumorigenesis. These data also provide the impetus for further clinical evaluation of HSP90, AKT, MEK or E2F pathway inhibitors in PRCC.Graphical

Abstract 3591: First in class drug ZB131 shows efficacy in cholangiocarcinoma models

Abstract Cholangiocarcinoma (CCA) is a lethal cancer with a high unmet need. The survival rate is low (5-year survival &amp;lt;20%), most non-palliative patients relapse within two years, and treatments in the advanced setting are limited. While FGFR2 and IDH1 inhibitors are effective in patients with select genomic alterations, they address only a small fraction (&amp;lt;20%) of biliary tract cancers. We now present the discovery and characterization of ZB131, a first in class humanized monoclonal antibody targeted to cancer specific plectin (CSP). CSP is a pro-tumorigenic protein exclusively expressed on the cancer cell surface. Previously, we demonstrated remarkable tumor regressions in preclinical murine models of pancreatic and ovarian cancer using a tool anti-CSP murine antibody. Here, we show that intra- and extra-hepatic CCA are 92% and 86% positive for membranous plectin staining by IHC, respectively, suggesting that anti-CSP therapy could be broadly effective against CCA. Indeed, in CCA cell lines in vitro, ZB131 (0.4nM binding affinity) arrests cell cycle, inhibits cell migration, and triggers intracellular ROS accumulation. In addition, both ZB131 and its murine version significantly suppressed tumor growth in 83% of the mice in a xenograft model and caused complete regression in the remaining 17%. Previous data from our group and others suggesting that CSP plays a role in chemoresistance led us to evaluate the efficacy of ZB131 in combination with gemcitabine. In vitro, we treated CSP-positive WITT cells with combinations of 0-500nM gemcitabine plus 0-1000nM ZB131 and found pockets of synergy or additivity. In a CCA xenograft model, the combination of 1mg/kg ZB131 and 100mg/kg gemcitabine showed 91% suppression in tumor growth compared with 74% in gemcitabine alone and 77% in huIgG plus gemcitabine at day 32. Collectively, our results suggest that ZB131 renders CCA tumors more chemosensitive and enhances the antitumor effects of gemcitabine. In contrast to the standard-of-care CCA treatment regimen, ZB131 showed remarkably low toxicity, likely because the antibody bypasses any non-malignant cells where plectin remains strictly cytoplasmic. Fc effector functional studies revealed a lack of antibody-dependent cell-mediated and complement-dependent cytotoxicity. Hemolysis and cytokine release studies suggested that ZB131 is compatible with human blood and unlikely to cause adverse cytokine release. Furthermore, in GLP toxicology studies, no signs of toxicity were observed at the highest dose evaluated of 100mg/kg/week, providing a &amp;gt;30-fold safety margin from the estimated human efficacious dose of 3mg/kg/week. In summary, ZB131 is an exciting new avenue for the treatment of CCA and other CSP-positive cancers with an excellent safety profile and strong antitumor activity in vitro and in murine models. Phase I clinical trials of ZB131 have been initiated. Citation Format: Samantha M. Perez, Randall Burton, Denise Krawitz, Christopher Sheth, Pina Cardarelli, Molly Owens, Brian Murphy, Matthew J. Reilley, Lindsey T. Brinton, Kimberly A. Kelly. First in class drug ZB131 shows efficacy in cholangiocarcinoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3591.

Abstract LB508: The development of HK013, a bispecific antibody targeting MSLN and CD137, for the treatment of MSLN+ solid tumors

Abstract Mesothelin (MSLN) is a 70 KDa cell surface glycoprotein that is rarely expressed in normal tissues but overexpressed in a variety of cancers, including mesothelioma, ovarian cancer, pancreatic cancer and breast cancer. Binding of MSLN with CA125/MUC16 promotes cell proliferation, local infiltration and metastasis. CD137 is mainly expressed on the surface of activated T cells, NK cells and some other immune cells, mediating the costimulatory signal to enhance the function of T cells and improve the anti-tumor ability of immune cells. Here, we report the development of a bispecific antibody, HK013, targeting both MSLN and CD137 for the treatment of solid tumors. The bispecific antibody HK013 was generated by introducing an anti-MSLN nanobody to the C-terminus of the heavy chain of an anti-CD137 antibody. Two stages were involved: first, we compared the MSLN nanobodies with different binding epitopes to select the optimal candidate. Two nanobodies, R2G12 and R3C7, with the binding affinity of 10-9M to human MSLN were selected. R3C7 blocks the binding of MORAb-009 to MSLN, while R2G12 does not. However, the bi-specific antibody containing R2G12 exhibited stronger anti-tumor activity than that containing R3C7 in both N87 and H226 mouse xenograft models. We then determined the best isotype and format of the bispecific antibody. While IgG1 or IgG4 (FALA) were selected as the candidate isotypes, the anti-MSLN VHH were linked to the N-terminal or C-terminal of the heavy chain of anti-CD137 antibody. Results showed that in the presence of H226 cells, IFN-γ secretion of CD8+T cells was slightly higher as triggered by IgG1 isotype than that by IgG4. However, IgG1-based molecules were not as potent as those in IgG4 in N87 and H226 xenograft models. Moreover, IgG1-based molecules showed cytotoxicity on CD4+T and CD8+T cells while those in IgG4 did not. In addition, HK013 exhibited the minimal ability of non-specific activation of CD137 signaling pathway by Fc receptor in a NFκB-luciferase reporter assay.These data indicate that our bispecific antibodies containing MSLN nanobodies with different epitopes exhibit varied antitumor activity, and antibodies with similar epitopes to MORAb-009 show poor antitumor activity. Molecules in IgG1 may potentially reduce the antitumor activity due to the cytotoxicity to the effector T cells. The bispecific formats are related to the Fc receptor-mediated non-specific activation of CD137 signal, which may potentially cause safety issue. The strong antitumor activity and the lowest non-specific activation of CD137 signal of HK013 makes it the candidate worthwhile of further evaluation of its safety and efficacy. Citation Format: Xing Xu, Dayan Zhang, Wenting Liu, Guodong Shen, Liansheng Cheng. The development of HK013, a bispecific antibody targeting MSLN and CD137, for the treatment of MSLN+ solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB508.