Small Molecule PD-L1 Research Articles

Preparation and effects of functionalized liposomes targeting breast cancer tumors using chemotherapy, phototherapy, and immunotherapy

Breast cancer therapy has significantly advanced by targeting the programmed cell death-ligand 1/programmed cell death-1 (PD-L1/PD-1) pathway. BMS-202 (a smallmolecule PD-L1 inhibitor) induces PD-L1 dimerization to block PD-1/PD-L1 interactions, allowing the T-cell-mediated immune response to kill tumor cells. However, immunotherapy alone has limited effects. Clinically approved photodynamic therapy (PDT) activates immunity and selectively targets malignant cells. However, PDT aggravates hypoxia, which may compromise its therapeutic efficacy and promote tumor metastasis. We designed a tumor-specific delivery nanoplatform of liposomes that encapsulate the hypoxia-sensitive antitumor drug tirapazamine (TPZ) and the small-molecule immunosuppressant BMS. New indocyanine green (IR820)-loaded polyethylenimine-folic acid (PEI-FA) was complexed with TPZ and BMS-loaded liposomes via electrostatic interactions to form lipid nanocomposites. This nanoplatform can be triggered by near-infrared irradiation to induce PDT, resulting in a hypoxic tumor environment and activation of the prodrug TPZ to achieve efficient chemotherapy. The in vitro and in vivo studies demonstrated excellent combined PDT, chemotherapy, and immunotherapy effects on the regression of distant tumors and lung metastases, providing a reference method for the preparation of targeted agents for treating breast cancer.Graphical abstract

A phase 1 study of the small-molecule PD-L1 inhibitor INCB099280 in select advanced solid tumors: Updated safety, efficacy, and pharmacokinetics (PK) results.

A phase 1 study of the small-molecule PD-L1 inhibitor INCB099280 in select advanced solid tumors: Updated safety, efficacy, and pharmacokinetics (PK) results.

Abstract 2039: Cellular characterization of small molecule PD-L1 inhibitors reveal their novel mechanisms of action

Abstract Introductions: Immune checkpoint inhibitors, including PD-1/L1, are key regulators of immune response and promising targets in cancer immunotherapy. Like anti-PD-1/L1 antibodies, small molecule PD-L1 inhibitors that have been discovered by us and others could also efficiently block PD-1 and PD-L1 interaction and exhibit anti-tumor efficacy in preclinical and clinically settings. In this study, we explore the cellular mechanism of small molecule PD-L1 inhibitors, unveiling their novel mechanisms of action in the regulation of PD-L1 and its functions. Materials and Methods: The cellular effects of the small molecule PD-L1 inhibitor on PD-L1 protein and RNA levels were assessed through Western blot and real-time qPCR experiments. HTRF assay and cellular luciferase reporter assay were used to evaluate the blockade of PD-1 and PD-L1 interaction in vitro and in cells. Flow cytometry and confocal microscopy were used to investigate the internalization of PD-L1 upon treatment with inhibitors. MSD assay was used to evaluate the alteration of soluble PD-L1 proteins. Results: Small molecule PD-L1 inhibitors discovered by Abbisko Therapeutics potently blocked PD-1/PD-L1 interaction in vitro and in cellular system. It could also rapidly and strongly induce PD-L1 internalization in cells. Further profiling suggested that small molecule PD-L1 inhibitors specifically disrupt PD-L1 N-glycosylation, resulting in aberrant PD-L1 glycosylation. This, in turn, may hinder the proper translocation of newly synthesized PD-L1 to the cell surface, thereby abolishing its interaction with PD-1 and functions in immune regulation. Conclusion: Taken together, these results for the first time revealed the distinctive mechanisms of our small molecule PD-L1 inhibitors. With their multi-layer inhibitory effects stemming from various mechanisms, small molecule PD-L1 inhibitors may offer potentially improved activities and an alternative therapeutic treatment for the cancer patients. Citation Format: Weiling Pan, Yongxian Zhang, Fangfei Qi, Wenqun Xin, Zhigang Feng, Zhui Chen, Haiyan Ying. Cellular characterization of small molecule PD-L1 inhibitors reveal their novel mechanisms of action [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 2039.

Abstract 4046: Orally active PD-L1 inhibitor MAX-10181 in combination with temozolomide effectively prolonged survival in GBM animal model study

Abstract Treatment of glioblastoma (GBM) with PD-1/PD-L1 immuno therapy is highly challenging due to the limited brain blood barrier (BBB) penetration of the marketed antibody drugs. During the past several years, we have successfully developed orally active, BBB penetrating, small molecule PD-L1 inhibitor MAX-10181 which is in the phase II clinical development. To demonstrate the utility of PD-1/L1 immuno therapy for the treatment of GBM, we completed the study of MAX-10181 in combination with Temozolomide (TMZ) in GL-261 animal model study. In this study, the combination of MAX-10181 with TMZ effectively prolonged the survival by 50% in comparison with TMZ single therapy. Details of this study will be reported in this meeting. Citation Format: Yuguang Wang, Zhenhua Feng, Qiang Zhao, Wu Zhang, Yiwei Jiang, Yingqi Huang, Chenxing Qi, Cheng Zhang. Orally active PD-L1 inhibitor MAX-10181 in combination with temozolomide effectively prolonged survival in GBM animal model study [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 4046.

Abstract 5522: Elucidating the role of P-selectin/P-selectin ligand-1 axis in lung cancer brain metastasis

Abstract Lung cancer (LC) stands as a prominent cause of cancer-related mortality. Brain metastasis (BM) is a common occurrence in LC, constituting nearly 50% of all BM cases with the brain emerging as the preferred site for LC metastasis. Unfortunately, current LCBM treatment options yield limited success, as reflected in the median survival of BM patients at 7.8 months. Consequently, there is an imperative need for novel and more efficacious therapeutic approaches targeting LCBM. Evidence suggests that brain microenvironment cells, particularly microglia and tumor-associated macrophages (TAMs), play a pivotal role in facilitating the colonization and growth of LCBM. Previous investigations from our lab have identified the involvement of the P-selectin/P-selectin glycoprotein ligand-1 (SELP/PSGL-1) axis in microglia/TAMs immunophenotypes, promoting pro-tumorigenic activity. This led us to explore the role of the SELP/PSGL-1 axis in the interactions between LCBM cells and the brain microenvironment1. Thus, we conducted Immunostaining on human tissue samples, revealing increased expression of SELP, PSGL-1, PD-1, PD-L1, IBA-1, and CD68 in LCBM tissues. Simultaneously, we employed advanced 3D models to investigate the intricate interactions between cancer cells and microglia/TAMs. Actively inhibiting the SELP/PSGL-1 axis with pharmacological agents led to a significant decrease in migration and invasion when LC cells were co-cultured with microglia and TAMs. Moreover, SELP inhibition prompted a shift in microglia/TAMs state towards an M1-like phenotype, enhancing the ability of CD4/CD8 cells to target cancer cells in our unique 3D LCBM models. This effect was further enhanced when co-treated with a PD-1 inhibitor, demonstrating a potential synergistic impact in targeting both pathways for therapeutic intervention. Our results suggest that combining SELP inhibition with other immunomodulators, including a small molecule PD-L1 inhibitor developed in our lab2, could synergistically enhance both innate and adaptive anti-tumor immune responses. Taken together, this study may enhance our understanding of LCBM immunogenicity and contribute to the development of novel immunotherapeutic approaches that can improve patient outcomes.1.Yeini, E., et al. P-selectin axis plays a key role in microglia immunophenotype and glioblastoma progression. Nat Commun 12, 1912 (2021). 2. Acúrcio, R.C., et al. Therapeutic targeting of PD-1/PD-L1 blockade by novel small-molecule inhibitors recruits cytotoxic T cells into solid tumor microenvironment. J Immunother Cancer 10(2022). Citation Format: Koren Salomon, Eilam Yeini, Neta Frommer, Irisi Kamer, Jair Bar, Iris Barshack, Ronit Satchi-Fainaro. Elucidating the role of P-selectin/P-selectin ligand-1 axis in lung cancer brain metastasis [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 5522.

Design, Synthesis, and Evaluation of 8-(o-Tolyl)quinazoline Derivatives as Small-Molecule PD-1/PD-L1 Antagonists.

Small-molecule inhibitors targeting programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) interactions can compensate for the shortcomings of antibody-based inhibitors and have attracted considerable attention, some of which have already entered clinical trials. Herein, based on our previous study on small-molecule PD-L1 inhibitors, we reported a series of 8-(o-tolyl)quinazoline derivatives by the skeleton merging strategy. Homogenous time-resolved fluorescence (HTRF) assay against PD-1/PD-L1 interaction identified compound A5, which showed the most potent inhibition with an IC50 value of 23.78 nM. Meanwhile, based on the results of HTRF assay, the structure-activity relationships (SARs) of the tail were focused on. Cell-based PD-1/PD-L1 blockade assay further revealed that A5 significantly blocked the PD-1/PD-L1 interaction at 1.1 μM in the co-culture system of Jurkat-NFAT-PD-1 cells and Hep3B-OS8-hPD-L1 cells with no significant cytotoxicity on Jurkat cells. Moreover, the proposed binding mode of A5 was investigated by a docking analysis. These results indicate that compound A5 is a promising lead compound that deserves further investigation.

Development and In Vivo Evaluation of Small-Molecule Ligands for Positron Emission Tomography of Immune Checkpoint Modulation Targeting Programmed Cell Death 1 Ligand 1.

A substantial portion of patients do not benefit from programmed cell death protein 1/programmed cell death 1 ligand 1 (PD-1/PD-L1) checkpoint inhibition therapies, necessitating a deeper understanding of predictive biomarkers. Immunohistochemistry (IHC) has played a pivotal role in assessing PD-L1 expression, but small-molecule positron emission tomography (PET) tracers could offer a promising avenue to address IHC-associated limitations, i.e., invasiveness and PD-L1 expression heterogeneity. PET tracers would allow for improved quantification of PD-L1 through noninvasive whole-body imaging, thereby enhancing patient stratification. Here, a large series of PD-L1 targeting small molecules were synthesized, leveraging advantageous substructures to achieve exceptionally low nanomolar affinities. Compound 5c emerged as a promising candidate (IC50 = 10.2 nM) and underwent successful carbon-11 radiolabeling. However, a lack of in vivo tracer uptake in xenografts and notable accumulation in excretory organs was observed, underscoring the challenges encountered in small-molecule PD-L1 PET tracer development. The findings, including structure-activity relationships and in vivo biodistribution data, stand to illuminate the path forward for refining small-molecule PD-L1 PET tracers.

Inhibition of UV-Induced Stress Signaling and Inflammatory Responses in SKH-1 Mouse Skin by Topical Small-Molecule PD-L1 Blockade

The immune checkpoint ligand PD-L1 has emerged as a molecular target for skin cancer therapy and might also hold promise for preventive intervention targeting solar UV light-induced skin damage. In this study, we have explored the role of PD-L1 in acute keratinocytic photodamage testing the effects of small-molecule pharmacological inhibition. Epidermal PD-L1 upregulation in response to chronic photodamage was established using immunohistochemical and proteomic analyses of a human skin cohort, consistent with earlier observations that PD-L1 is upregulated in cutaneous squamous cell carcinoma. Topical application of the small-molecule PD-L1 inhibitor BMS-202 significantly attenuated UV-induced activator protein-1 transcriptional activity in SKH-1 bioluminescent reporter mouse skin, also confirmed in human HaCaT reporter keratinocytes. RT-qPCR analysis revealed that BMS-202 antagonized UV induction of inflammatory gene expression. Likewise, UV-induced cleavage of procaspase-3, a hallmark of acute skin photodamage, was attenuated by topical BMS-202. NanoString nCounter transcriptomic analysis confirmed downregulation of cutaneous innate immunity- and inflammation-related responses, together with upregulation of immune response pathway gene expression. Further mechanistic analysis confirmed that BMS-202 antagonizes UV-induced PD-L1 expression both at the mRNA and protein levels in SKH-1 epidermis. These data suggest that topical pharmacological PD-L1 antagonism using BMS-202 shows promise for skin protection against photodamage.

Assembling Au8 clusters on surfaces of bifunctional nanoimmunomodulators for synergistically enhanced low dose radiotherapy of metastatic tumor

BackgroundRadiotherapy is one of the mainstays of cancer therapy and has been used for treating 65–75% of patients with solid tumors. However, radiotherapy of tumors has two limitations: high-dose X-rays damage adjacent normal tissue and tumor metastases cannot be prevented.ResultsTherefore, to overcome the two limitations of radiotherapy, a multifunctional core–shell R837/BMS@Au8 nanoparticles as a novel radiosensitizer were fabricated by assembling Au8NCs on the surface of a bifunctional nanoimmunomodulator R837/BMS nanocore using nanoprecipitation followed by electrostatic assembly. Formed R837/BMS@Au8 NP composed of R837, BMS-1, and Au8 clusters. Au8NC can enhance X-ray absorption at the tumor site to reduce X-ray dose and releases a large number of tumor-associated antigens under X-ray irradiation. With the help of immune adjuvant R837, dendritic cells can effectively process and present tumor-associated antigens to activate effector T cells, meanwhile, a small-molecule PD-L1 inhibitor BMS-1 can block PD-1/PD-L1 pathway to reactivate cytotoxic T lymphocyte, resulting in a strong systemic antitumor immune response that is beneficial for limiting tumor metastasis. According to in vivo and in vitro experiments, radioimmunotherapy based on R837/BMS@Au8 nanoparticles can increase calreticulin expression on of cancer cells, reactive oxygen species generation, and DNA breakage and decrease colony formation. The results revealed that distant tumors were 78.2% inhibited depending on radioimmunotherapy of primary tumors. Therefore, the use of a novel radiosensitizer R837/BMS@Au8 NPs realizes low-dose radiotherapy combined with immunotherapy against advanced cancer.ConclusionIn conclusion, the multifunctional core–shell R837/BMS@Au8 nanoparticles as a novel radiosensitizer effectively limiting tumor metastasis and decrease X-ray dose to 1 Gy, providing an efective strategy for the construction of nanosystems with radiosensitizing function.

Abstract B151: Discovery and characterization of a novel small molecule brain penetrant PD-L1 inhibitor

Abstract Introduction: Immunotherapy has revolutionized cancer treatment in the last decade. Several monoclonal PD-1 and PD-L1 antibodies have been approved for treating various cancers. Small molecule PD-L1 inhibitors with brain-penetrating ability may have potential to overcome the limitations of antibodies and bring benefit for patients with intracranial tumors. Leveraging advanced computation-aided structural analysis and medicinal chemistry design, we have successfully discovered an innovative orally available small molecule PD-L1 inhibitor ABSK044. In preclinical experiments, this compound demonstrates robust T-cell activating ability, strong anti-tumor efficacy, and brain-penetrating activity. Method: ABSK044's ability to block PD-1-PD-L1 interaction was evaluated by HTRF assay and cellular luciferase reporter assay. Its biological activity was evaluated in vitro in MLR and in vivo in syngeneic tumor models. Results: ABSK044 strongly inhibits PD-1-PD-L1 interaction with an IC50 less than 1nM in vitro and very potently rescues PD-L1-induced suppression of T cell activation signaling in cells. Furthermore, it efficiently rescues cytokine production in CD8+ T cells suppressed by PD-L1, reaching a level comparable to that of PD-L1 antibodies. In in vivo studies, oral administration of ABSK044 strongly inhibits tumor growth to an extent similar to therapeutic anti-PD-L1 antibodies. Notably, ABSK044 demonstrates excellent brain penetration with a Kp value exceeding 0.4. DMPK and safety profiling demonstrate excellent drug-like properties of ABSK044. Conclusion: ABSK044, presented here by Abbisko Therapeutics, is a highly potent and orally available small molecule PD-L1 antagonist with brain-penetrating activity. Its superior profile supports its fast-track preclinical development. Citation Format: Yongxian Zhang, Mingming Zhang, Baowei Zhao, Hongping Yu, Yao-Chang Xu, Zhui Chen, Haiyan Ying. Discovery and characterization of a novel small molecule brain penetrant PD-L1 inhibitor [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 B151.

134P A phase I study exploring the safety and tolerability of the small molecule PD-L1 inhibitor INCB099318 in select advanced solid tumors

134P A phase I study exploring the safety and tolerability of the small molecule PD-L1 inhibitor INCB099318 in select advanced solid tumors

155P A phase I study exploring the safety and tolerability of the small-molecule PD-L1 inhibitor INCB099280 in select advanced solid tumors

155P A phase I study exploring the safety and tolerability of the small-molecule PD-L1 inhibitor INCB099280 in select advanced solid tumors

On the Road towards Small-Molecule Programmed Cell Death 1 Ligand 1 Positron Emission Tomography Tracers: A Ligand-Based Drug Design Approach.

PD-1/PD-L1 immune checkpoint blockade for cancer therapy showed promising results in clinical studies. Further endeavors are required to enhance patient stratification, as, at present, only a small portion of patients with PD-L1-positive tumors (as determined by PD-L1 targeted immunohistochemistry; IHC) benefit from anti-PD-1/PD-L1 immunotherapy. This can be explained by the heterogeneity of tumor lesions and the intrinsic limitation of multiple biopsies. Consequently, non-invasive in vivo quantification of PD-L1 on tumors and metastases throughout the entire body using positron emission tomography (PET) imaging holds the potential to augment patient stratification. Within the scope of this work, six new small molecules were synthesized by following a ligand-based drug design approach supported by computational docking utilizing lead structures based on the (2-methyl-[1,1'-biphenyl]-3-yl)methanol scaffold and evaluated in vitro for potential future use as PD-L1 PET tracers. The results demonstrated binding affinities in the nanomolar to micromolar range for lead structures and newly prepared molecules, respectively. Carbon-11 labeling was successfully and selectively established and optimized with very good radiochemical conversions of up to 57%. The obtained insights into the significance of polar intermolecular interactions, along with the successful radiosyntheses, could contribute substantially to the future development of small-molecule PD-L1 PET tracers.

Vitamin D Receptor Antagonist MeTC7 Inhibits PD-L1.

Small-molecule inhibitors of PD-L1 are postulated to control immune evasion in tumors similar to antibodies that target the PD-L1/PD-1 immune checkpoint axis. However, the identity of targetable PD-L1 inducers is required to develop small-molecule PD-L1 inhibitors. In this study, using chromatin immunoprecipitation (ChIP) assay and siRNA, we demonstrate that vitamin D/VDR regulates PD-L1 expression in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells. We have examined whether a VDR antagonist, MeTC7, can inhibit PD-L1. To ensure that MeTC7 inhibits VDR/PD-L1 without off-target effects, we examined competitive inhibition of VDR by MeTC7, utilizing ligand-dependent dimerization of VDR-RXR, RXR-RXR, and VDR-coactivators in a mammalian 2-hybrid (M2H) assay. MeTC7 inhibits VDR selectively, suppresses PD-L1 expression sparing PD-L2, and inhibits the cell viability, clonogenicity, and xenograft growth of AML cells. MeTC7 blocks AML/mesenchymal stem cells (MSCs) adhesion and increases the efferocytotic efficiency of THP-1 AML cells. Additionally, utilizing a syngeneic colorectal cancer model in which VDR/PD-L1 co-upregulation occurs in vivo under radiation therapy (RT), MeTC7 inhibits PD-L1 and enhances intra-tumoral CD8+T cells expressing lymphoid activation antigen-CD69. Taken together, MeTC7 is a promising small-molecule inhibitor of PD-L1 with clinical potential.

Carbohydrate Strengthens the Immunotherapeutic Effect of Small-Molecule PD-L1 Inhibitors.

PD-1/PD-L1 checkpoint blockade has demonstrated great success in cancer immunotherapy. Small-molecule PD-L1 inhibitors also attract significant research interests but remain challenging in the efficacy and safety. Carbohydrate moiety and carbohydrate-binding proteins (lectins) play important roles in immune modulation including antigen recognition and presenting. Herein, we reported a novel strategy to strengthen the immunotherapeutic effect of small-molecule PD-L1 inhibitors by introducing sugar motifs, which may utilize the carbohydrate-mediated immune enhancement for cancer treatment. The data revealed that glycoside compounds containing mannose or N-acetylglucosamine exhibited the best results in IFN-γ secretion. Moreover, compared to the nonglycosylated compounds, glycosides C3 and C15 demonstrated significant lower cytotoxicity and effective in vivo antitumor potency in the CT26 and melanoma B16-F10 tumor models with good tolerance. Notably, tumor-infiltrating lymphocyte (TIL) analysis validated increased CD3+, CD4+, CD8+, and granzyme B+ T cells after glycoside treatments. This work presents a new concept to improve the immunotherapy.

Discovery of novel benzohydroxamate-based histone deacetylase 6 (HDAC6) inhibitors with the ability to potentiate anti-PD-L1 immunotherapy in melanoma

In this study, a novel series of histone deacetylases 6 (HDAC6) inhibitors containing polycyclic aromatic rings were discovered and evaluated for their pharmacological activities. The most potent compound 10c exhibited high HDAC6 inhibitory activity (IC50 = 261 nM) and excellent HDAC6 selectivity (SI = 109 for HDAC6 over HDAC3). 10c also showed decent antiproliferative activity in vitro with IC50 of 7.37–21.84 μM against four cancer cell lines, comparable to that of tubastatin A (average IC50 = 6.10 μM). Further mechanism studies revealed that 10c efficiently induced apoptosis and S-phase arrest in B16-F10 cells. In addition, 10c markedly increased the expression of acetylated-α-tubulin both in vitro and in vivo, without affecting the levels of acetylated-H3 (marker of HDAC1 inhibition). Furthermore, 10c (80 mg/kg) exhibited moderate antitumor efficacy in a melanoma tumour model with a tumour growth inhibition (TGI) of 32.9%, comparable to that (TGI = 31.3%) of tubastatin A. Importantly, the combination of 10c with NP19 (a small molecule PD-L1 inhibitor discovered by us before) decreased tumour burden substantially (TGI% = 60.1%) as compared to monotherapy groups. Moreover, the combination of 10c with NP19 enhanced the anti-tumour immune response, mediated by a decrease of PD-L1 expression levels and increased infiltration of anti-tumour CD8+ T cells in tumour tissues. Collectively, 10c represents a novel HDAC6 inhibitor deserving further investigation as a potential anti-cancer agent.

Novel PD-L1-Targeted Phenyl-Pyrazolone Derivatives with Antioxidant Properties.

Orally-active anticancer small molecules targeting the PD-1/PD-L1 immune checkpoint are actively searched. Phenyl-pyrazolone derivatives with a high affinity for PD-L1 have been designed and characterized. In addition, the phenyl-pyrazolone unit acts as a scavenger of oxygen free radicals, providing antioxidant effects. The mechanism is known for the drug edaravone (1) which is also an aldehyde-reactive molecule. The present study reports the synthesis and functional characterization of new molecules (2-5) with an improved anti-PD-L1 activity. The leading fluorinated molecule 5 emerges as a potent checkpoint inhibitor, avidly binding to PD-L1, inducing its dimerization, blocking PD-1/PD-L1 signaling mediated by phosphatase SHP-2 and reactivating the proliferation of CTLL-2 cells in the presence of PD-L1. In parallel, the compound maintains a significant antioxidant activity, characterized using electron paramagnetic resonance (EPR)-based free radical scavenging assays with the probes DPPH and DMPO. The aldehyde reactivity of the molecules was investigated using 4-hydroxynonenal (4-HNE), which is a major lipid peroxidation product. The formation of drug-HNE adducts, monitored by high resolution mass spectrometry (HRMS), was clearly identified and compared for each compound. The study leads to the selection of compound 5 and the dichlorophenyl-pyrazolone unit as a scaffold for the design of small molecule PD-L1 inhibitors endowed with antioxidant properties.

Abstract 5254: Topical inhibition of UV-induced PD-L1 expression and inflammatory signaling by the small molecule inhibitor BMS-202

Abstract Immune evasion is a molecular hallmark of cancer, and overexpression of the immune checkpoint protein PD-L1 (CD274) has been documented in several tumors including cutaneous squamous cell carcinoma (cSCC). Notably, while baseline levels of PD-L1 in normal human epidermis are low, acute solar-simulated light (SSL) exposure increases the expression of this protein in epidermal keratinocytes, an effect which can be replicated in cultured keratinocytes and in mouse models. While current immunotherapies targeting the PD-1/PD-L1 axis using monoclonal antibodies are providing therapeutic benefits in many cancers including cSCC, small molecule inhibitors are also being developed to target PD-L1 which may be amenable for topical formulation and therefore early intervention with reduced systemic exposure. We have recently tested one such molecule, BMS-202, in vitro and in vivo. BMS-202 application to keratinocytes in culture inhibits UV-induced PD-L1 RNA and protein expression. Notably, exposure to this inhibitor also reduced UV-induced stress signaling as measured by AP-1 luciferase assay in cultured keratinocytes. Topical application of BMS-202 to immunocompetent SKH-1 mouse skin resulted in significant inhibition of SSL-induced epidermal PD-L1 as determined by immunoblot analysis. NanoString nCounter Pathway™ transcriptomic analysis of full-thickness SKH-1 mouse skin shows strong inhibition of SSL-induced inflammatory responses, chemokine activity, innate immune response and NF-κB activation in BMS-202 treated samples compared to SSL-only controls. Our results indicate that early intervention against PD-L1 expression/activity could be a viable target for skin cancer photochemoprevention. Topical application of small molecule PD-L1 inhibitors such as BMS-202 may provide novel treatment options for populations at high risk for cSCC. Citation Format: Prajakta Vaishampayan, Jana Jandova, Yuchen (Ella) Ai, Viktoria Kirschnerova, Clara Curiel-Lewandrowski, Georg T. Wondrak, Sally E. Dickinson. Topical inhibition of UV-induced PD-L1 expression and inflammatory signaling by the small molecule inhibitor BMS-202. [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 5254.

Novel Small-Molecule PD-L1 Inhibitor Induces PD-L1 Internalization and Optimizes the Immune Microenvironment.

Blocking the PD-1/PD-L1 interaction has become an important strategy for tumor therapy, which has shown outstanding therapeutic effects in clinical settings. However, unsatisfactory response rates and immune-related adverse effects limit the use of anti-PD1/PD-L1 antibodies. Here, we report the discovery and identification of S4-1, an innovative small-molecule inhibitor of PD-L1. In vitro, S4-1 effectively altered the PD-L1/PD-1 interaction, induced PD-L1 dimerization and internalization, improved its localization to endoplasmic reticulum, and thus enhanced the cytotoxicity of peripheral blood mononuclear cells toward tumor cells. In vivo, S4-1 significantly inhibited tumor growth in both lung and colorectal cancer models, particularly in colorectal cancer, where it led to complete clearance of a portion of the tumor cells. Furthermore, S4-1 induced T-cell activation and inversed the inhibitory tumor microenvironment, consistent with the PD-L1/PD-1 pathway blockade. These data support the continued evaluation of S4-1 as an alternative ICB therapeutic strategy.

Discovery of Novel Acridane-Based Tubulin Polymerization Inhibitors with Anticancer and Potential Immunomodulatory Effects.

A series of novel acridane-based tubulin polymerization inhibitors were designed, synthesized, and bioevaluated as anticancer agents. The most potent compound NT-6 exhibited high tubulin polymerization inhibitory activity (IC50 = 1.5 μM) and remarkable antiproliferative potency against four cancer cell lines with an average IC50 of 30 nM, better than colchicine and the hit compound 1f (IC50 of 65 and 126 nM, respectively). In addition, NT-6 (10 mg/kg) exerted excellent antitumor efficacy in a melanoma tumor model with a tumor growth inhibition (TGI) of 65.1% without apparent toxicity. Importantly, the combination of NT-6 with a small-molecule PD-L1 inhibitor NP-19 decreased tumor burden significantly (TGI% = 77.6%). Moreover, the combination of NT-6 with NP-19 enhanced the antitumor immune response, mediated by a decrease of PD-L1 expression levels and increased infiltration of antitumor CD8+ effector T cells in tumor tissues. Collectively, NT-6 represents a novel tubulin polymerization inhibitor with immunopotentiating effects.