Small Molecule Inhibitor Targeting Research Articles

A phase Ib/II study to evaluate surufatinib combined with camrelizumab and chemotherapy in the second-line treatment of advanced colorectal cancer: Phase Ib results.

3555 Background: Surufatinib is a novel small-molecule kinase inhibitor targeting VEGFR1-3, FGFR and CSF-1R with confirmed efficacy in epNET and pNET. Preclinical studies have demonstrated that surufatinib combined with immune checkpoint inhibitors (ICIs) have synergistic antitumor effects by modulating tumor immune microenvironment. Additionally, surufatinib plus toripalimab (anti-PD-1) has showed preliminary anti-tumor activity in multiple solid tumors, including colorectal cancer (CRC). This study aimed to evaluate the efficacy and safety of surufatinib plus camrelizumab (anti-PD-1), irinotecan and GM-CSF as second-line treatment in advanced CRC. Here we reported the results of the phase Ib study. Methods: This ongoing phase Ib/II, open-label trial (NCT04929652) enrolled patients (pts) aged 18-75 years old with pathologically confirmed locally advanced or metastatic CRC who have progressed on/been intolerant to the standard first-line therapy. In the Ib dose escalation/de-escalation phase, pts received surufatinib at 250mg once daily (QD) as starting dose, in combination with fixed dose of camrelizumab (200 mg, d1), irinotecan (200 mg/m2, d1) and GM-CSF (5ug/kg, d2-d7), every 3 weeks (Q3W). Based on DLTs, the dose of surufatinib should escalate to 300 mg or de-escalate to 200 mg. The primary objective of the phase Ib study was to determine the safety and DLT in first treatment cycle defining the recommended phase 2 dose (PR2D). Additional 36 pts were enrolled in the phase II dose expansion stage using RP2D. Primary endpoint of phase II was ORR as per RECIST 1.1. Secondary endpoints included PFS, DCR, OS and safety. Results: Enrollment opened in Nov 2021 and data cutoff in Dec 2022. 12 pts (median age 54) were treated in Phase Ib study (surufatinib 250 mg: N = 6; surufatinib 300 mg: N = 6). 75% were male and 17% had ECOG PS 1. 11/12 (92%) pts were positive for KRAS, NRAS or BRAF mutations. No DLT was observed in the starting dose cohort (surufatinib 250 mg), and one patient in the surufatinib 300 mg cohort experienced DLT (Grade [G] 3 vomiting). Surufatinib 300 mg QD was defined as the RP2D. Other G3 treatment related adverse events (TRAEs) were hypertension (1/12; 8.3%) and diarrhea (1/12; 8.3%). All other TRAEs were grade 1-2, and the most common (≥40%) were diarrhea (75%), fatigue (58%), vomiting (58%), nausea (50%), hypertension (42%), proteinuria (42%) and alopecia (42%). Of the 12 pts evaluable for tumor response, 3 pts achieved PR, 9 pts achieved SD. The ORR was 25% (3/12), the DCR was 100% (12/12) and median PFS was 7.2 months (95%CI 3.7-10.7). Conclusions: Surufatinib plus camrelizumab, irinotecan and GM-CSF was well tolerated, with a manageable safety profile, and showed preliminary anti-tumor activity in patients with advanced CRC. The dose-expansion phase is ongoing. Clinical trial information: NCT04929652 .

Identification of a novel small-molecule inhibitor targeting TIM-3 for cancer immunotherapy

PD-1/PD-L1 blockade has achieved substantial clinical results in cancer treatment. However, the expression of other immune checkpoints leads to resistance and hinders the efficacy of PD-1/PD-L1 blockade. T cell immunoglobulin and mucin domain 3 (TIM-3), a non-redundant immune checkpoint, synergizes with PD-1 to mediate T cell dysfunction in tumor microenvironment. Development of small molecules targeting TIM-3 is a promising strategy for cancer immunotherapy. Here, to identify small molecule inhibitors targeting TIM-3, the docking pocket in TIM-3 was analyzed by Molecular Operating Environment (MOE) and the Chemdiv compound database was screened. The small molecule SMI402 could bind to TIM-3 with high affinity and prevent the ligation of PtdSer, HMGB1, and CEACAM1. SMI402 reinvigorated T cell function in vitro. In the MC38-bearing mouse model, SMI402 inhibited tumor growth by increasing CD8+ T and natural killing (NK) cells infiltration at the tumor site, as well as restoring the function of CD8+ T and NK cells. In conclusions, the small molecule SMI402 shows promise as a leading compound which targets TIM-3 for cancer immunotherapy.

An Artificial Peptide-Based Bifunctional HIV-1 Entry Inhibitor That Interferes with Viral Glycoprotein-41 Six-Helix Bundle Formation and Antagonizes CCR5 on the Host Cell Membrane.

Human immunodeficiency virus type 1 (HIV-1) is characterized by high variability and drug resistance. This has necessitated the development of antivirals with a new chemotype and therapy. We previously identified an artificial peptide with non-native protein sequence, AP3, with the potential to inhibit HIV-1 fusion through targeting hydrophobic grooves on the N-terminal heptad repeat trimer of viral glycoprotein gp41. Here, a small-molecule HIV-1 inhibitor targeting chemokine coreceptor CCR5 on the host cell was integrated into the AP3 peptide, producing a novel dual-target inhibitor with improved activity against multiple HIV-1 strains including those resistant to the currently used anti-HIV-1 drug enfuvirtide. Its superior antiviral potency in comparison with the respective pharmacophoric moieties is in consonance with the dual binding of viral gp41 and host factor CCR5. Therefore, our work provides a potent artificial peptide-based bifunctional HIV-1 entry inhibitor and highlights the multitarget-directed ligands approach in the development of novel therapeutic anti-HIV-1 agents.

The catalytic inhibitor epacadostat can affect the non-enzymatic function of IDO1.

Indoleamine 2,3-dioxygenase 1 (IDO1) is a tryptophan metabolizing enzyme chronically activated in many cancer patients and its expression and activity correlate with a poor prognosis. In fact, it acts as an immune regulator and contributes to tumor-induced immunosuppression by determining tryptophan deprivation and producing immunosuppressive metabolites named kynurenines. These findings made IDO1 an attractive target for cancer immunotherapy and small-molecule inhibitors, such as epacadostat, have been developed to block its enzymatic activity. Although epacadostat was effective in preclinical models and in early phase trials, it gave negative results in a metastatic melanoma randomized phase III study to test the benefit of adding epacadostat to the reference pembrolizumab therapy. However, the reason for the epacadostat failure in this clinical trial has never been understood. Our data suggest that a possible explanation of epacadostat ineffectiveness may rely on the ability of this drug to enhance the other IDO1 immunoregulatory mechanism, involving intracellular signaling function. These findings open up a new perspective for IDO1 inhibitors developed as new anticancer drugs, which should be carefully evaluated for their ability to block not only the catalytic but also the signaling activity of IDO1.

Abstract 1397: Collagen COL26A1 promotes papillary thyroid cancer invasion and metastasis and correlates with poor survival and clinical outcomes

Abstract Papillary thyroid cancer (PTC) is the most common cancer in women under 25 years of age and is increasing in incidence. While PTC is often slow-growing and surgically resectable, recurrence years to decades after initial surgery occurs in ~20% of patients (now only in their 40s/50s), with mortality of 38-69%. The identification of both prognostic biomarkers and actionable therapeutic targets for high-risk PTC at diagnosis is critically important and an unmet need. RNASeq analysis of 45 PTC and matched normal patient tissues from our biobank identified collagen 26A1 (COL26A1) as significantly upregulated in patients with higher risk extrathyroidal extension, lymph node metastasis, and multifocal tumors, compared to those with localized disease. Kaplan Meier survival curves of The Cancer Genome Atlas (TCGA) data confirmed that increased COL26A1 expression significantly decreases survival probability by 25% (p=0.0086). Further analyses of TCGA data indicated that COL26A1 expression significantly correlated with clinical attributes including MACIS score (q=0.001), differentiation score (q=0.025), and tumor stage (q=0.025). Data from our in vitro culture PTC model system indicated that COL26A1 expression was increased 3X in PTC cell line K1, compared to immortalized “normal” thyroid epithelial cells, NThy-ori-3-1. Two CRISPR guides designed to target COL26A1 introduced into K1 resulted in repression of COL26A1 RNA and protein levels by 50% and 70%, respectively. COL26A1 repression decreased critical tumor phenotypes of aggressiveness and metastasis including proliferation (30%), clonogenicity (33%), anchorage-independent growth (37%), cell motility (43%), invasion (30%) and migration (33%). Cell-to-cell adhesion and cell-matrix adhesion also decreased (36% and 25%, respectively). Thus, COL26A1 may have use as a prognostic marker and actionable target for small molecule inhibitors in PTC. Citation Format: Michelle Carnazza, Danielle Quaranto, Nicole DeSouza, Sina Dadafarin, Augustine Moscatello, Jan Geliebter, Raj K. Tiwari. Collagen COL26A1 promotes papillary thyroid cancer invasion and metastasis and correlates with poor survival and clinical outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1397.

Abstract 4941: Development of small molecule RPN13 inhibitors for treatment of glioblastoma

Abstract Glioblastoma (GBM) is an aggressive and deadly brain cancer with a one-year median survival due to the lack of effective targeted treatments. Our goal is to develop a small molecule inhibitor targeting RPN13 protein in the 19S proteasome complex as a new drug for GBM. RPN13 is a proteasome ubiquitin receptor that recognizes ubiquitin-conjugated proteins that are thus tagged for degradation via the 20S proteasome enzymatic complex. GBM is highly sensitive to proteasome inhibition due to its aggressive growth and accumulation of misfolded polyubiquitinated proteins that is insufficiently managed despite increased proteasome levels and enhanced proteasome activity (i.e. proteotoxic stress). Up Therapeutics judiciously designed drug-like RPN13 inhibitors to overcome limitations in the prototype RPN13 inhibitor RA190 identified at Johns Hopkins University. We selected Up284 as lead compound based upon our preliminary studies showing drug-like characteristics, specificity (binding to Cys88 of RPN13), and proteasome inhibition that produces a cytotoxic accumulation of polyUb proteins, ER stress, and reactive oxygen species. Up284 treatment selectively triggers apoptosis in solid tumor types including GBM cell lines and oncospheres. A suitable Up284 formulation was selected by measuring aqueous solubility, stability and on-target activity in mice imaged using a proteasome-dependent in vivo reporter. Up284 can be administered i.v. or orally, and it penetrates through the BBB. As a proof of concept for treatment of GBM, Up284 demonstrated on-target activity in intracranial syngeneic GL261 tumor model by inhibiting proteasome function in tumor tissues. Up284 also well tolerated and regressed tumors in syngeneic, xenograft and spontaneous models of ovarian and breast cancers with acceptable safety profile. Up284 also synergize with current frontline chemotherapeutics and can be used as a single agent or in combination for the treatment of wide range of cancers. Citation Format: Yung-Nien Chang, Ravi K. Anchoori, Alex Shimura Yamashita, Marina da Costa Rosa. Development of small molecule RPN13 inhibitors for treatment of glioblastoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4941.

KW2449 ameliorates collagen-induced arthritis by inhibiting RIPK1-dependent necroptosis.

Necroptosis has recently been found to be associated with the pathogenesis of many autoimmune diseases, including rheumatoid arthritis (RA). This study was undertaken to explore the role of RIPK1-dependent necroptosis in the pathogenesis of RA and the potential new treatment options. The plasma levels of receptor-interacting protein kinase 1 (RIPK1) and mixed lineage kinase domain-like pseudokinase (MLKL) in 23 controls and 42 RA patients were detected by ELISA. Collagen-induced arthritis (CIA) rats were treated with KW2449 by gavage for 28 days. Arthritis index score, H&E staining, and Micro-CT analysis were used to evaluate joint inflammation. The levels of RIPK1-dependent necroptosis related proteins and inflammatory cytokines were detected by qRT-PCR, ELISA and Western blot, and the cell death morphology was detected by flow cytometry analysis and high-content imaging analysis. The plasma levels of RIPK1 and MLKL in RA patients were higher than those in healthy people, and were positively correlated with the severity of RA. KW2449 could reduce joint swelling, joint bone destruction, tissue damage, and the plasma levels of inflammatory cytokines in CIA rats. Lipopolysaccharide combined with zVAD (LZ) could induce necroptosis in RAW 264.7 cells, which could be reduced by KW2449. RIPK1-dependent necroptosis related proteins and inflammatory factors increased after LZ induction and decreased after KW2449 treatment or knockdown of RIPK1. These findings suggest that the overexpression of RIPK1 is positively correlated with the severity of RA. KW2449, as a small molecule inhibitor targeting RIPK1, has the potential to be a therapeutic strategy for RA treatment by inhibiting RIPK1-dependent necroptosis.

Induction of DNMT1-dependent demethylation of SHP-1 by the natural flavonoid compound Baicalein overcame Imatinib-resistance in CML CD34+ cells

BackgroundThe most significant cause of treatment failure in chronic myeloid leukemia (CML) is a persistent population of minimal residual cells. Emerging evidences showed that methylation of SHP-1 contributed to Imatinib (IM) resistance. Baicalein was reported to have an effect on reversal of chemotherapeutic agents resistance. However, the molecular mechanism of Baicalein on JAK2/STAT5 signaling inhibition against drug resistance in bone marrow (BM) microenvironment that had not been clearly revealed.MethodsWe co-cultured hBMSCs and CML CD34+ cells as a model of SFM-DR. Further researches were performed to clarify the reverse mechanisms of Baicalein on SFM-DR model and engraftment model. The apoptosis, cytotoxicity, proliferation, GM-CSF secretion, JAK2/STAT5 activity, the expression of SHP-1 and DNMT1 were analyzed. To validate the role of SHP-1 on the reversal effect of Baicalein, the SHP-1 gene was over-expressed by pCMV6-entry shp-1 and silenced by SHP-1 shRNA, respectively. Meanwhile, the DNMT1 inhibitor decitabine was used. The methylation extent of SHP-1 was evaluated using MSP and BSP. The molecular docking was replenished to further explore the binding possibility of Baicalein and DNMT1.ResultsBCR/ABL-independent activation of JAK2/STAT5 signaling was involved in IM resistance in CML CD34+ subpopulation. Baicalein significantly reversed BM microenvironment-induced IM resistance not through reducing GM-CSF secretion, but interfering DNMT1 expression and activity. Baicalein induced DNMT1-mediated demethylation of the SHP-1 promoter region, and subsequently activated SHP-1 re-expression, which resulted in an inhibition of JAK2/STAT5 signaling in resistant CML CD34+ cells. Molecular docking model indicated that DNMT1 and Baicalein had binding pockets in 3D structures, which further supported Baicalein might be a small-molecule inhibitor targeting DNMT1.ConclusionsThe mechanism of Baicalein on improving the sensitivity of CD34+ cells to IM might be correlated with SHP-1 demethylation by inhibition of DNMT1 expression. These findings suggested that Baicalein could be a promising candidate by targeting DNMT1 to eradicate minimal residual disease in CML patients.95sLX1XYQtwthw7A939XEYVideo

Rational combination of SHP2 and mTOR inhibition for the treatment of hepatocellular carcinoma.

Liver cancer is the fourth most common cause of cancer-related death worldwide, with hepatocellular carcinoma (HCC) being the main primary malignancy affecting the liver. Unfortunately, there are still limited therapeutic options for HCC, and even the latest advances have only increased the overall survival modestly. Thus, new treatment strategies and rational drug combinations are urgently needed. Reactivation of receptor tyrosine kinases (RTK) has been described as a mechanism of intrinsic resistance to targeted therapies in a variety of cancers, including inhibitors of mTOR. The design of rational combination therapies to overcome this type of resistance is complicated by the notion that multiple RTK can be upregulated during the acquisition of resistance. SHP2, encoded by the gene PTPN11, acts downstream of virtually all RTK, and has proven to be a good target for small molecule inhibitors. Here, we report activation of multiple RTK upon mTOR inhibition in HCC which, through SHP2, leads to reactivation of the mTOR pathway. We show that co-inhibition of both mTOR and SHP2 is highly synergistic in vitro by triggering apoptosis. More importantly, the combination is well-tolerated and outperforms the monotherapies in impairing tumor growth in multiple HCC mouse models. Our findings suggest a novel rational combination therapy for the treatment of HCC.

Computational analysis to investigate the anti-rheumatic potential of plant-based small molecule inhibitor targeting tumor necrosis factor α.

Objective: This study aimed to assess the anti-rheumatic potential of Dodonaea viscosa and to evaluate its bioactive small molecules for their beneficial effects in the management of rheumatoid arthritis. Methods: In vitro bioactivity assays were performed to assess the healing potential of D. viscosa and statistical analysis was performed by using the linear regression technique. In silico analysis was performed to identify the key inhibitors of the disease to target TNF-α. The plant extract was prepared using ethanol solvent via the Soxhlet method. Phytochemical and bioactivity testing was performed. Gas chromatography-mass spectrometry (GC-MS) analysis was conducted for bioactive plant compounds. Disease-specific target was shortlisted by HUB gene analysis. Molecular docking and molecular dynamic simulations were run for validation of the results. Results: Phytochemical studies verified the presence of phenols, flavonoids, steroids, sterols, saponins, coumarins, tannins, and terpenoids. The significant antioxidant potential of plant extract was evaluated by the DPPH and Ferric Reducing Antioxidant Power (FRAP) assays, while the anti-inflammatory potential was evaluated by the protein denaturation and Human Red Blood Cell (HRBC) membrane stabilization assays. In silico studies revealed that nine of the 480 compounds found in D. viscosa (ethanol extract) had drug-like properties. Tumor necrosis factor alpha (TNF-α) was selected as a key disease gene through HUB gene analysis. Results of molecular docking and MD simulation analysis demonstrated that 4-(1-hydroxy-3-oxo-1H-isoindol-2-yl) benzoic acid (PubChemID 18873897), had the best binding affinity with TNF-α amongst all nine compounds. Conclusion: 4-(1-hydroxy-3-oxo-1H-isoindol-2-yl) benzoic acid (PubChemID 18873897), have the potential to be a good small molecule inhibitor of TNF-α against rheumatoid arthritis.

Targeting M-Ras and Raf kinases by dual allosteric inhibitors.

We report on a computational design of novel druglike small molecules that could allosterically bind both M-Ras and B/C-Raf kinases. The Ras kinases participate in cellular signal transmission leading to cell growth. Mutations can make Ras kinases continually activated, leading to cancer. Ras proteins activate the Raf kinases, which stimulate MAPK pathways involved in the cell cycle. Many drugs are MAPK inhibitors. However, bypass signaling frequently develops leading to drug resistance. B-Raf kinase inhibitors effectively inhibit the ERK kinase within MAPK in B-Raf-mutant cancers. However, they can also stimulate the C-Raf activation in Ras-mutated cancers. Cancers with Ras mutations can switch their signaling from B-Raf to C-Raf, leading to cancer progression. M-Ras is a non-classical Ras variant, which can compensate for mutated classical Ras kinases (H/K/N), leading to bypass signaling. Thus, M-Ras is a suitable target for small-molecule inhibitors. Most inhibitors bind to the kinases’ catalytic sites, which are similar in various kinases and, thus, difficult to target specifically. Allosteric sites differ in kinases, allowing for selective binding. We analyzed the M-Ras and B/C-Raf allosteric binding sites using the Deep View program. New putative small-molecule inhibitors were designed by systematic alterations of known inhibitors. The druglike properties of the designed molecules were found by the DataWarrior and Molinspiration programs. The molecules with optimal druglike properties and no implied toxicities were docked to M-Ras and B/C-Raf in ArgusLab. Their binding energies were calculated. Two designed molecules were found to bind allosterically to both B/C-Raf and M-Ras with greater binding energies and improved druglike properties than the known single-kinase inhibitors. This study, together with previous experimental findings, suggests that the molecules designed here may be successful allosteric B/C-Raf and M-Ras inhibitors with improved therapeutic results in cancers with mutated Ras or Raf.

Targeted Inhibition of the HGF/c-Met Pathway by Merestinib Augments the Effects of Albumin-Bound Paclitaxel in Gastric Cancer

Background and Hypothesis: Combination chemotherapy regimens are commonly used to treat gastric adenocarcinoma (GAC), but the median survival time remains less than one year. Nab-paclitaxel has demonstrated high antitumor activity in previous GAC studies. Many growth factors and their receptors are overexpressed in GAC and have been implicated in its pathophysiology. We hypothesize that merestinib, a small-molecule inhibitor targeting c-Met, Axl, and DDR1/2 pathways, will have significant antitumor effects and will enhance the response to nab-paclitaxel in GAC preclinical models.
 Project Methods: In vitro proliferation and protein expression were assessed using WST-1 and immunoblot assays. Subcutaneous xenografts of MKN-45 and SNU-1 cell lines were implanted in mice to study tumor growth inhibition. Immunohistochemistry was performed to examine intratumor proliferation and microvessel density.
 Results: In vitro assays showed that nab-paclitaxel and merestinib decreased cell proliferation in all three cell lines, with an additive effect in combination. Reduction in cell proliferation at low doses of nab-paclitaxel (10 nM), merestinib (100 nM), and their combination was 87%, 82%, and 94% (MKN-45 cell line, high phospho-c-Met expression), 59%, 50%, and 82% (SNU-1 cell line, low phospho-c-Met expression), and 53%, 19%, and 66% in gastric fibroblasts. Immunoblot analysis of merestinib treated MKN-45 cells revealed increased expression of apoptotic proteins and decreased expression of phospho-c-Met, phospho-EGFR, phospho-IGF-1R, phospho-ERK, and phospho-AKT. In gastric fibroblasts, merestinib decreased phospho-ERK and increased apoptotic protein expression. Phospho-c-Met and phospho-EGFR were not detected in SNU-1 immunoblots; however, phospho-ERK, phospho-VEGFR, and apoptotic protein expression increased after treatment. In MKN-45 xenografts, net tumor growth in control, nab-paclitaxel, merestinib, and combination groups was 503 mm3, 115 mm3, 91 mm3, and -9.7 mm3. Immunohistochemistry analysis of tumor cell proliferation and microvessel density corroborated tumor growth study results.
 Conclusion: The data suggest that merestinib in combination with nab-paclitaxel carry a promising potential for improving clinical GAC therapy.

Approaching the Dimerization Mechanism of Small Molecule Inhibitors Targeting PD-L1 with Molecular Simulation.

Inhibitors blocking the PD-1/PD-L1 immune checkpoint demonstrate impressive anti-tumor immunity, and small molecule inhibitors disclosed by the Bristol-Myers Squibb (BMS) company have become a hot topic. In this work, by modifying the carbonyl group of BMS-202 into a hydroxyl group to achieve two enantiomers (MS and MR) with a chiral center, we found that this is an effective way to regulate its hydrophobicity and thus to reduce the negative effect of polar solvation free energy, which enhances the stability of PD-L1 dimer/inhibitor complexes. Moreover, we studied the binding modes of BMS-200 and BMS-202-related small molecule inhibitors by molecular dynamics simulation to explore their inhibitory mechanism targeting PD-L1 dimerization. The results showed that the size exclusion effect of the inhibitors triggered the rearrangement of the residue ATyr56, leading to the formation of an axisymmetric tunnel-shaped pocket, which is an important structural basis for improving the binding affinity of symmetric inhibitors with PD-L1. Furthermore, after inhibitor dissociation, the conformation of ATyr123 and BMet115 rearranged, which blocked the entrance of the binding pocket, while the reverse rearrangements of the same residues occurred when the PD-L1 monomer was complexed with the inhibitors, preparing PD-L1 for dimerization. Overall, this study casts a new light on the inhibitory mechanism of BMS inhibitors targeting PD-L1 dimerization and provides an idea for designing novel small molecule inhibitors for future cancer immunotherapy.

Zika virus cleaves GSDMD to disseminate prognosticable and controllable oncolysis in a human glioblastoma cell model

Glioblastoma (GBM) is the most common aggressive malignant brain cancer and is chemo- and radioresistant, with poor therapeutic outcomes. The "double-edged sword" of virus-induced cell death could be a potential solution if the oncolytic virus specifically kills cancer cells but spares normal ones. Zika virus (ZIKV) has been defined as a prospective oncolytic virus by selectively targeting GBM cells, but unclear understanding of how ZIKV kills GBM and the consequences hinders its application. Here, we found that the cellular gasdermin D (GSDMD) is required for the efficient death of a human GBM cell line caused by ZIKV infection. The ZIKV protease specifically cleaves human GSDMD to activate caspase-independent pyroptosis, harming both viral protease-harboring and naive neighboring cells. Analyzing human GSDMD variants showed that most people were susceptible to ZIKV-induced cytotoxicity, except for those with variants that resisted ZIKV cleavage or were defective in oligomerizing the N terminus GSDMD cleavage product. Consistently, ZIKV-induced secretion of the pro-inflammatory cytokine interleukin-1β and cytolytic activity were both stopped by a small-molecule inhibitor targeting GSDMD oligomerization. Thus, potential ZIKV oncolytic therapy for GBM would depend on the patient's GSDMD genetic background and could be abolished by GSDMD inhibitors if required.

Pre-Clinical Investigation of a Novel Small Molecule Inhibitor Targeting YBX1 in AML

Recently, our group identified the pleiotropic DNA and RNA binding protein YBX1 as a specific dependency and therapeutic target in acute myeloid leukemia (AML) that is essential for stabilizing oncogenic transcripts and thereby maintains oncogenic protein expression (Perner et al., 2021). Selective pharmacologic targeting of YBX1 in AML, however, has not been achieved so far. Here, we investigate the functional consequences of a novel small molecule inhibitor (SU056) of YBX1 in AML. We examined the viability of several human AML cell lines (MOLM13, HL60, EOL1, THP1, Kasumi1, ML2, Mv4;11, OCI-AML3, NOMO1) upon SU056 treatment and found significant reduction of cell growth in a concentration dependent manner. Inhibition of cell growth could be mainly attributed to impaired proliferative capacity at nanomolar concentrations. Pharmacologic inhibition of YBX1 resulted in impaired colony formation (mean colony number DMSO: 231.3±13.88 vs. SU056 500nM: 154.7±8.29; p<0.0001), cell cycle arrest (cells in S phase: DMSO: 37.3±2.4 vs. SU056 500nM: 27.2±1.67; p=0.0127) and induction of myeloid differentiation. Consistently, in a xenograft model of human AML, SU056 treatment resulted in prolonged disease latency (MOLM13 diluent: 62 days OS vs. SU056: not reached, p=0.0013; OCI-AML3 diluent: 79 days OS vs. not reached, p=0.0001) and significant reduction of disease penetrance (MOLM13 diluent: 100% vs. SU056: 24,9%; OCI-AML3 diluent: 100% vs. SU056: 9,1%). Consistently, percentage of SU056 treated human leukemic cells in the bone marrow of recipient mice was decreased for both, MOLM13 (mean diluent: 41,3% vs. SU056: 7,6%) and OCI-AML3 (mean diluent: 28,9% vs. SU056: 2,9%). Likewise, pharmacologic inhibition of YBX1 reduced colony formation and total cell numbers of primary human AML cells in a dose-dependent manner. To be clinically relevant, such treatment must have a suitable therapeutic index between human hematopoietic stem- and progenitor cells (HSPCs) and their malignant counterpart. This is particularly important, considering the role of YBX1 in mRNA splicing and processing. Of note, pharmacologic inhibition of YBX1 did not perturb colony formation of normal HSPCs derived from apheresis donors. These findings were confirmed by investigating primary human leukemic cells in a patient-derived xenograft (PDX) model of AML. We aimed to assess whether loss in leukemia cell competition induced by pharmacologic targeting of YBX1 is sufficient for normal hematopoietic cells to outcompete leukemic cells in vivo. 1x106 normal human HSPCs were transplanted along with 2x104 leukemic cells to assess for efficacy of SU056-treatment versus diluent control. In vivo treatment with SU056 (20mg/kg, i.p.) for 3 weeks resulted in a significant decrease in the AML blast number in the PB (mean blast %: diluent: 38.5%; SU056: 2.25%; p<0.0001). This resulted in increased survival of SU056 treated recipients (OS diluent: 83 days vs. SU056: not reached). To confirm the proposed mechanism by which SU056 impairs leukemia growth we performed global transcriptome and proteome analysis following treatment with SU056 (500nM, 96h). Proteome profiling revealed a total of 2641 deregulated proteins. Gene-ontology analysis indicated deregulation of YBX1 targets and proteins associated with cell cycle, DNA repair, mRNA splicing/processing, and transcriptional regulation. Of note, overlap between transcriptional regulation (as determined by mRNA-Seq) and changes in proteome abundance revealed less than 5% target genes/proteins, indicating that SU056 may in fact interfere with binding of oncogenic mRNAs to YBX1 and thereby may reduce translation of oncogenic transcripts. In order to define functional consequences of pharmacologic YBX1 inhibition and explore potential vulnerabilities of drug combinations, we performed a genome-wide CRISPR/Cas9 screen in human AML cells treated with SU056 versus diluent control. Validation experiments are currently ongoing. Taken together, our data confirm the therapeutic potential to target YBX1 using the novel small molecule SU056. Given its broad applicability across genetic subtypes of AML and lack of toxicity on normal HSPCs, SU056 as a single agent or in combination with established targeted therapies may efficiently help to target and outcompete leukemic cells. Experiments to assess for potential synergy with already established targeted therapies will be presented.

EXTH-45. TARGETING GLIOBLASTOMA BY NOVEL INTEGRIN-SPECIFIC CAR T CELLS

Abstract RATIONALE Innovative treatment strategies are urgently needed to improve the prognosis of glioblastoma patients. Chimeric antigen receptor (CAR) T cell therapy has shown great success in hematological malignancies. However, it remains to be shown that CAR T cells are also active against solid tumors. αv integrins are overexpressed in gliomas and have already been used as therapeutic targets for small molecule inhibitors and antibodies. While these approaches were well tolerated, they did not exert meaningful clinical activity in glioblastoma patients. We aimed at exploiting the presence of αv integrins as targets for anti-glioma CAR T cell therapy. METHODS CAR T cells targeting specific integrin heterodimers (αvβ3, αvβ5 or αvβ8) were generated and their anti-glioma activity was determined in co-culture assays with different glioma cells. The efficacy of CAR T cells to control tumor growth in vivo was assessed in clinically relevant orthotopic mouse glioma models. RESULTS All newly generated integrin-targeting CAR T cells exerted strong anti-tumor activity in vitro. The highest lytic activity against glioma cells was observed for αvβ5 and αvβ8 integrin-specific CAR T cells. CAR T cells generated from patient-derived immune cells displayed strong lytic activity when tested against autologous tumors cells. Glioma cells with a CRISPR/Cas9-mediated knockout of the target antigen were resistant to CAR T cell-mediated cytotoxicity demonstrating their specificity. The in vivo activity of integrin-specific CAR T cells was tested in 2 orthotopic glioma models. Intratumoral treatment of glioma-bearing mice with αvβ5 or αvβ8 CAR T cells significantly prolonged their survival and cured a substantial fraction of these animals. CONCLUSION αvβ5- and αvβ8-specific CAR T cells exert strong and target-specific anti-glioma activity in vitro and prolong the survival of glioma-bearing mice. These data form the basis for a clinical evaluation of integrin-specific CAR T cells against glioblastoma.

RF19 | PSUN349 Histone Eraser and Reader Targeting Epigenetic Inhibitors Are Effective in Pancreatic Neuroendocrine Tumours

Abstract Background The 5-year survival for metastatic pancreatic neuroendocrine tumours (PNETs) is &amp;lt;50%, and current therapies are not effective. Thus, there is an unmet clinical need for new therapies for patients with PNETs. PNETs frequently have mutations in chromatin remodelling genes, including in Multiple Endocrine Neoplasia type 1 (MEN1), encoding menin, which is mutated in up to 40% of sporadic PNETs, and is part of multiple histone modifying complexes including the SET1/MLL methyltransferases. Aim To examine multiple classes of epigenetic inhibitors and determine which may be effective in treating PNETs. Methods BON1 and QGP1 PNET cell lines, the bronchial NET cell line H727, and the non-NET cell line HEK293T were utilised to assess &amp;gt;150 small molecule inhibitors targeting: histone deacetylases (HDACs); histone acetyltransferases; histone demethylases (KDMs); histone methyltransferases; bromodomain-containing proteins; menin; and DNA methyltransferases (DNMTs). MTOR inhibitors, already used clinically for PNET patients, as well as drugs targeting other tumorigenic pathways e.g. the proto-oncogene SRC, were used as comparators. Efficacy of compounds was evaluated using the Cell Titer Blue cell viability assay, and the Caspase Glo 3/7 apoptosis assay. Results At a dose of 1mM for 7 days, 26 compounds (including HDAC, KDM, bromodomain and mTOR inhibitors) significantly decreased the viability of both the BON1 and QGP1 cell lines by &amp;gt;50%, compared to DMSO control treated cells. Upon increasing the dose to 10mM for 7 days, 34 additional compounds, making a total of 60 compounds (including inhibitors of menin and DNMTs), decreased viability of both BON1 and QGP1 cells by &amp;gt;50%; and 56 and 46 compounds also reduced viability of H727 and HEK293 cells by &amp;gt;50%, respectively. Apoptosis assays utilising the 60 above compounds, at 10mM for 7 days, revealed that 25, 18, 14, and 9 of them could increase apoptosis by &amp;gt;4-fold of BON1, QGP1, H727 and HEK293 cells, respectively. Ten compounds (2 KDM, 5 HDAC and 3 bromodomain inhibitors) that were effective in reducing viability by &amp;gt;50% as well as increasing apoptosis by &amp;gt;4-fold of NET cells, were selected for further dosing (0.1-10mM) and time course investigations (3-7 days). All 10 compounds significantly reduced viability of BON1 and QGP1 cells (p&amp;lt;0.01) after 3 days of treatment. The KDM and HDAC inhibitors showed the greatest efficacy, by significantly (p&amp;lt;0.05) reducing BON1 and QGP1 cell viability at as low as 25nM treatment for 3 days. The efficacy of bromodomain inhibitors was not attained until 1000nM treatment, however these inhibitors had very little effect on the non-NET HEK293 cells. Conclusions Compounds targeting HDACs, KDMs or bromodomain-containing proteins are effective in reducing viability by &amp;gt;50% and increasing apoptosis by &amp;gt;4-fold of NET cells, and thus provide novel agents for studying anti-cancer mechanisms and potential therapeutic options for PNETs. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 1:12 p.m. - 1:17 p.m.

A Novel Selective Axl/Mer/CSF1R Kinase Inhibitor as a Cancer Immunotherapeutic Agent Targeting Both Immune and Tumor Cells in the Tumor Microenvironment.

Simple SummaryImmune checkpoint blockade has had great success over the past decade, but many patients with cancer do not benefit because most immune checkpoint inhibitors only target T cells. Targeting non-T cell populations in the tumor microenvironment (TME) has been shown to affect responses to them. Simultaneous inhibition of Axl, Mer and CSF1R by a novel receptor tyrosine kinase inhibitor Q702 induces antitumor immunity by reducing the number of M2 macrophages and MDSCs and inducing M1 macrophages and cytotoxic CD8 T cells in the TME, and increasing the expression of MHC-I and E-cadherin in tumor cells. Our data indicate that therapy targeting both immune cells and cancer cells in the TME by Q702 can induce more effective clinical responses in patients with cancer.Although immune checkpoint blockade (ICB) represents a major breakthrough in cancer immunotherapy, only a limited number of patients with cancer benefit from ICB-based immunotherapy because most immune checkpoint inhibitors (ICIs) target only T cell activation. Therefore, targeting non-T cell components in the tumor microenvironment (TME) can help subvert resistance and increase the applications of ICB-based therapy. Axl and Mer are involved in the carcinogenesis of multiple types of cancer by modulating immune and biological behaviors within tumors. Colony stimulating factor 1 receptor (CSF1R) mediates tumorigenesis in the TME by enhancing tumor associated macrophage (TAM) and myeloid-derived suppressor cell (MDSC) infiltration, facilitating immune escape. Therefore, the simultaneous inhibition of Axl, Mer, and CSF1R kinases may improve therapeutic efficacy by targeting non-T cell components in the TME. Here, we present Q702, a selective, potent small molecule inhibitor targeting Axl, Mer, and CSF1R, for oral administration. Q702 induced antitumor activity in syngeneic tumor mouse models by: remodeling the TME toward immune stimulation; expanding M1 macrophage and CD8 T cell populations and decreasing M2 macrophage and MDSC populations in the TME; and increasing MHC class I and E-cadherin expression in tumor cells. Thus, Q702 may have great potential to broaden the coverage of populations benefiting from ICB-based immunotherapy.

317 (PB097) - Identification of novel therapeutic targets to overcome chemoresistance in high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSC) remains a deadly gynecologic malignancy that kills approximately 120 000 women per year worldwide. Despite initial responses to platinum and taxol-based combination therapy in the majority of patients, virtually all HGSC eventually recur as drug resistant disease with very few treatment options. Thus, it is critical to identify novel therapeutic targets and treatment modalities in chemotherapy-resistant HGSC. Here, we describe an approach that combines phenotypic screening in chemoresistant HGSC cell lines with proteome-wide profiling by mass spectrometry in order to deconvolute cellular targets of small molecule inhibitors that can overcome acquired chemotherapy resistance in HGSC.

OS08.8.A Integrin-specific CAR T cells for the treatment of glioblastoma

Abstract Background Current standard of care for glioblastoma patients has limited therapeutic efficacy and novel innovative treatment strategies are urgently needed. One such strategy is chimeric antigen receptor (CAR) T cell therapy that has shown great success in hematological malignancies. αv integrins are overexpressed in several neoplasms and have already been used as therapeutic targets for small molecule inhibitors and antibodies, which did not cause major toxicities. Herein, we propose αv integrins as an ideal target for CAR T cell therapy in glioblastoma. Material and Methods CAR T cells targeting specific heterodimers (αvβ3, αvβ5 or αvβ8) were generated by transducing primary human T cells from healthy donors with a lentiviral vector expressing a second-generation CAR. Activity and specificity of CAR T cells was determined by co-culture assays with different glioma cells. Efficacy of CAR T cells to control tumor growth in vivo was investigated in clinically relevant orthotopic xenograft glioma mouse models. Additionally, we generated CAR T cells from T cells from a glioblastoma patient and measured their activity against the patient’s autologous tumor cells. Results All newly generated integrin-targeting CAR T cells exerted strong anti-glioma activity in vitro. Long-term and repetitive killing assays as well as cytokine-release measurements demonstrated highest activity of αvβ5 and αvβ8 integrin-specific CAR T cells. Antigen specificity of these cells was confirmed, as glioma cells with a CRISPR/Cas9-mediated knockout of the target antigen were resistant to CAR T cell-mediated cytotoxicity. Intratumoral injection of αvβ5 or αvβ8 CAR T cells significantly prolonged the survival and cured a substantial fraction of glioma-bearing mice in two different xenograft models. When used in a patient-derived setting, matched CAR T cells exerted strong anti-glioma activity. Conclusion We show strong and integrin-specific anti-glioma activity of CAR T cells developed from healthy donor T cells and glioblastoma-patient-derived T cells in vitro. αvβ5- and αvβ8-specific CAR T cells exerted the best therapeutic activity in two different xenograft glioma models in vivo. These data support the evaluation of integrin-specific CAR T cells as a therapeutic strategy in clinical neuro-oncology.