Design, synthesis, and optimization of novel PD-L1 inhibitors and the identification of a highly potent and orally bioavailable PD-L1 inhibitor.

In this paper we report the discovery of structurally novel and highly potent programmed cell death-ligand 1 (PD-L1) inhibitors targeting surface and intracellular PD-L1. A ring fusion design utilizing dimethoxyphenyl indazole derivatives was used, followed by structural extension, which further improved potency by inducing the formation of additional symmetrical interactions within the PD-L1 binding site, leading to the discovery of novel and highly active tetra-aryl-scaffold inhibitors. Key optimizations involved polar tail chain modifications that improve potency and minimize cell cytotoxicity. In addition, druggability issues that exist outside the rule-of-five chemical space were addressed. CB31, a representative compound, was found to exhibit outstanding activity in blocking programmed cell death-1 (PD-1)/PD-L1 interactions (IC50 = 0.2 nM) and enhancing T-cell functions, with minimal cell cytotoxicity. CB31 also displayed favorable oral pharmacokinetic properties, consistent with its high passive permeability and insusceptibility to efflux transporters, as well as its high metabolic stability. Additionally, CB31 demonstrated mechanistically differentiated features from monoclonal antibodies by inducing PD-L1 internalization, intracellular retention of PD-L1 with altered glycosylation pattern, and PD-L1 degradation. It also demonstrated greater effects on tumor size reduction and tumor cell killing, with enhanced T-cell infiltration, in a 3D tumor spheroid model. Overall, results show that CB31 is a promising small-molecule PD-L1 inhibitor that can inhibit PD-1/PD-L1 interactions and promote PD-L1 degradation.

Gold Nano Frameworks with Mesopores for Synergistic Immune-Thermal Therapy in Hepatic Carcinoma: A Paradigm Shift in Immune Checkpoint Blockade.

Immune checkpoint blockade (ICB) therapy, while showing promise in various cancers, exhibits limited effectiveness in hepatic carcinoma due to the tumor's immunosuppressive microenvironment (TME) and challenges associated with immune cell infiltration. Efforts to transform the "cold" TME into an "inflamed" state, notably through chemo-immunotherapy, have sparked interest due to their potential to induce immunogenic cell death and augment the infiltration of cytotoxic T lymphocytes (CTLs). Nonetheless, the efficacy of chemo-immunotherapy is often compromised by suboptimal pharmacokinetics, poor tumor accumulation, and off-target toxicity. Herein, in response, we introduce an innovative, milder thermal therapeutic approach leveraging gold nano frameworks with mesopores for the targeted delivery of the immunostimulant imiquimod and NIR-II photothermal therapy. This strategy employs targeted molecule modifications to ensure precise tumor targeting, guided by photoacoustic imaging. Subsequent to mild thermal treatment, there is a release of immunogenic proteins (CRT and HSP90), enhancing tumor immunogenicity. Assisted by imiquimod, substantial CTL infiltration occurs, accompanied by pro-inflammatory factor release (TNF-α, IL-6), transforming M2 macrophages into the M1 phenotype. Ultimately, the proposed strategy combines PD-L1/PD-1 blockade, imiquimod and mild thermal treatment to synergistically enhance tumor immunogenicity, remodel the TME, and restrain hepatic carcinoma, making strides in ICB synergistic immune-thermal therapy.

Achieving Immune Activation by Suppressing the IDO1 Checkpoint with Sono-Targeted Biobromination for Antitumor Combination Immunotherapy.

Indoleamine-2,3-dioxygenase-1 (IDO1) pathogenically suppresses immune cell infiltration and promotes tumor cell immune escape by overmetabolizing tryptophan to N-formyl kynurenine in the tumor microenvironment (TME). However, it remains challenging for IDO1 immune checkpoint inhibitors to achieve a significant potency of progression-free survival. Here, we developed a breakthrough in IDO1 inhibition by sono-targeted biobromination reaction using immunostimulating hypobromic-P-phenylperoxydibenzoic acid-linked metallic organic framework nanomedicine (H-MOF NM) to remodel the TME from debrominated hypoxia into hypobromated normoxia and activate the IDO1 immune pathway with in vitro and in vivo remarkable antitumor efficacy. H-MOF NM contains Br+ and O- active ingredients with an enlarged band gap to deactivate IDO1 through an innovative biochemical mechanism, taking control over brominating IDO1 amino acid residues at the active sites in the remodeled TME and subsequently activating the immune response, including DC maturation, T-cell activation, and macrophage polarization. Importantly, the H-MOF NM achieves multiple immune responses with high tumor regression potency by combination sono-immunotherapy. This study describes an excellent IDO1 inhibition strategy through the development of immune biobrominative H-MOF nanomedicine and highlights efficient combination immunotherapy for tumor treatment.

Discovery of novel thiophene[3,2-d]pyrimidine-based tubulin inhibitors with enhanced antitumor efficacy for combined use with anti-pd-l1 immunotherapy in melanoma.

Herein, we designed and synthesized a series of novel 2-methylthieno [3,2-d]pyrimidine analogues as tubulin inhibitors with antiproliferative activities at low nanomolar levels. Among them, compound DPP-21 displayed the most potent anti-proliferative activity against six cancer cell lines with an average IC50 of ∼6.23 nM, better than that of colchicine (IC50 = 9.26 nM). DPP-21 exerted its anti-cancer activity by suppressing the polymerization of tubulin with an IC50 of 2.4 µM. Furthermore, the crystal structure of DPP-21 in complex with tubulin was solved by X-ray crystallography to 2.94 Å resolution, confirming the direct binding of DPP-21 to the colchicine site. Moreover, DPP-21 arrested the cell cycle in the G2/M phase of mitosis, subsequently inducing tumor cell apoptosis. Additionally, DPP-21 was able to effectively inhibit the migration of cancer cells. Besides, DPP-21 exhibited significant in vivo anti-tumor efficacy in a B16-F10 melanoma tumor model with a TGI of 63.3 % (7 mg/kg) by intraperitoneal (i.p.) injection. Notably, the combination of DPP-21 with NP-19 (a PD-L1-targeting small molecule inhibitor reported by our group before) demonstrated enhanced anti-cancer efficacy in vivo. These results suggest that DPP-21 is a promising lead compound deserving further investigation as a potential anti-cancer agent.

Cryo-Nanocatalyst Enhances Therapeutic Efficacy of Cryo-Immunotherapy through Necroptosis and Local Delivery of Programmed Death-Ligand 1 Inhibitors.

Combining cryoablation and immunotherapy presents a promising approach to revert immunosuppressive responses to solid tumors. However, challenges such as postablated residual tumors and insufficient immune activity contribute to recurrence after cryo-immunotherapy. Herein, we investigated metallic supra-structured cryo-nanocatalyst (MSCN), which features numerous ice nucleation sites and interspace loading of therapeutic agents. MSCN elevates the freezing point and enhances ice nucleation, facilitating effective ice formation during cryotreatment. MSCN-loaded tumor cells showed a 2-fold increase in cryo-cytotoxicity and undergo osmotic-related cell damage, primarily necroptosis rather than other regulated cell death mechanisms. In prostate cancer models, RNA sequencing reveals that MSCN-cryoablation promoted antitumor inflammatory pathways, including necroptosis, compared to cryoablation alone. Additionally, following programmed death-ligand 1 (PD-L1) upregulation postcryoablation, synergistic effects with PD-L1 blockade were confirmed. Given the interspace of MSCN for aPD-L1 loading, we compared the intratumoral delivery of PD-L1 blockade against systemic injection. Enhanced necrosis and necroptosis from MSCN-cryoablation and PD-L1 blockade effectively eradicated tumors and triggered antitumor and memory immune responses locally and systemically. Lastly, a spatial landscape of tumor-infiltrating immune cells was analyzed to gain insight into heterogeneous tumor responses, leading to the limitations of conventional focal ablation techniques. Our findings highlight the potential of advanced cryo-immunotherapy using cryo-nanocatalysis to promote ice formation and necroptosis, stimulating antitumor immunogenic responses.

Combined Effects of Anti-PD-L1 and Nanosonodynamic Therapy on HCC Immune Activation in Mice: An Investigation.

Introduction: Current therapeutic strategies, including immune checkpoint blockade (ICB), exhibit limited efficacy in treating hepatocellular carcinoma (HCC). Nanoparticles, particularly those that can accumulate specifically within tumors and be activated by sonodynamic therapy (SDT), can induce immunogenic cell death (ICD); however, ICD alone has not achieved satisfactory therapeutic effectiveness. This study investigates whether combining ICB with ICD induced by nanoparticle-mediated SDT could enhance anti-tumor immunity and inhibit HCC growth. Methods: We developed an iron-based micelle nanodelivery system encapsulating the Near-Infrared Dye IR-780, which was surface-modified with a cyclic tripeptide composed of arginine-glycine-aspartic acid (cRGD). This led to the synthesis of targeted IR780@FOM-cRGD nanoparticles. These nanoparticles were specifically engineered to kill tumor cells under sonication, activate immunogenic cell death (ICD), and be used in conjunction with immune checkpoint blockade (ICB) for the treatment of hepatocellular carcinoma (HCC). Results: The synthesized IR780@FOM-cRGD nanoparticles had an average diameter of 28.23±1.750 nm and a Zeta potential of -23.95±1.926. Confocal microscopy demonstrated that IR780@FOM-cRGD could target HCC cells while minimizing toxicity to healthy cells. Upon sonodynamic activation, these nanoparticles consumed significant amounts of oxygen and generated substantial reactive oxygen species (ROS), effectively killing tumor cells and inhibiting the proliferation, invasion, and migration of H22 cells. Hemolysis assays confirmed the in vivo safety of the nanoparticles, and in vivo fluorescence imaging revealed significant accumulation in tumor tissues. Mouse model experiments showed that combining ICB(which induced by Anti-PD-L1) with ICD (which induced by IR780@FOM-cRGD), could effectively activated anti-tumor immunity and suppressed tumor growth. Discussion: This study highlights the potential of IR780@FOM-cRGD nanoparticles to facilitate tumor eradication and immune activation when used in conjunction with Anti-PD-L1 therapy. This combination represents a non-invasive, efficient, and targeted approach for the treatment of hepatocellular carcinoma (HCC). By integrating sonodynamic therapy with immunotherapy, this strategy promises to substantially improve the effectiveness of traditional treatments in combating HCC, offering new avenues for clinical application and therapeutic innovation.

Fe3O4 Nanoparticles That Modulate the Polarisation of Tumor-Associated Macrophages Synergize with Photothermal Therapy and Immunotherapy (PD-1/PD-L1 Inhibitors) to Enhance Anti-Tumor Therapy.

Introduction: Traditional surgical resection, radiotherapy, and chemotherapy have been the treatment options for patients with head and neck squamous cell carcinoma (HNSCC) over the past few decades. Nevertheless, the five-year survival rate for patients has remained essentially unchanged, and research into treatments has been relatively stagnant. The combined application of photothermal therapy (PTT) and immunotherapy for treating HNSCC has considerable potential. Methods: Live-dead cell staining and CCK-8 assays proved that Fe3O4 nanoparticles are biocompatible in vitro. In vitro, cellular experiments utilized flow cytometry and immunofluorescence staining to verify the effect of Fe3O4 nanoparticles on the polarisation of tumor-associated macrophages. In vivo, animal experiments were conducted to assess the inhibitory effect of Fe3O4 nanoparticles on tumor proliferation under the photothermal effect in conjunction with BMS-1. Tumour tissue sections were stained to observe the effects of apoptosis and the inhibition of tumor cell proliferation. The histological damage to animal organs was analyzed by hematoxylin and eosin (H&E) staining. Results: The stable photothermal properties of Fe3O4 nanoparticles were validated by in vitro cellular and in vivo animal experiments. Fe3O4 photothermal action not only directly triggered immunogenic cell death (ICD) and enhanced the immunogenicity of the tumor microenvironment but also regulated the expression of tumor-associated macrophages (TAMs), up-regulating CD86 and down-regulating CD206 to inhibit tumor growth. The PD-1/PD-L1 inhibitor promoted tumor suppression, and reduced tumor recurrence and metastasis. In vivo studies demonstrated that the photothermal action exhibited a synergistic effect when combined with immunotherapy, resulting in significant suppression of primary tumors and an extension of survival. Conclusion: In this study, we applied Fe3O4 photothermolysis in a biomedical context, combining photothermolysis with immunotherapy, exploring a novel pathway for treating HNSCC and providing a new strategy for effectively treating HNSCC.

Antibody-Decorated Nanoplatform to Reprogram Macrophage and Block Immune Checkpoint LSECtin for Effective Cancer Immunotherapy.

Repolarizing tumor-associated macrophages (TAMs) into tumor-inhibiting M1 macrophages has been considered a promising strategy for enhanced cancer immunotherapy. However, several immunosuppressive ligands (e.g., LSECtin) can still be highly expressed on M1 macrophages, inducing unsatisfactory therapeutic outcomes. We herein developed an antibody-decorated nanoplatform composed of PEGylated iron oxide nanoparticles (IONPs) and LSECtin antibody conjugated onto the surface of IONPs via the hydrazone bond for enhanced cancer immunotherapy. After intravenous administration, the tumor microenvironment (TME) pH could trigger the hydrazone bond breakage and induce the disassociation of the nanoplatform into free LSECtin antibodies and IONPs. Consequently, the IONPs could repolarize TAMs into M1 macrophages to remodel immunosuppressive TME and provide an additional anticancer effect via secreting tumoricidal factors (e.g., interlukin-12). Meanwhile, the LSECtin antibody could further block the activity of LSECtin expressed on M1 macrophages and relieve its immunosuppressive effect on CD8+ T cells, ultimately leading to significant inhibition of tumor growth.

Injectable Nanocomposite Hydrogels Improve Intraperitoneal Co-delivery of Chemotherapeutics and Immune Checkpoint Inhibitors for Enhanced Peritoneal Metastasis Therapy.

Intraperitoneal co-delivery of chemotherapeutic drugs (CDs) and immune checkpoint inhibitors (ICIs) brings hope to improve treatment outcomes in patients with peritoneal metastasis from ovarian cancer (OC). However, current intraperitoneal drug delivery systems face issues such as rapid drug clearance from lymphatic drainage, heterogeneous drug distribution, and uncontrolled release of therapeutic agents into the peritoneal cavity. Herein, we developed an injectable nanohydrogel by combining carboxymethyl chitosan (CMCS) with bioadhesive nanoparticles (BNPs) based on polylactic acid-hyperbranched polyglycerol. This system enables the codelivery of CD and ICI into the intraperitoneal space to extend drug retention. The nanohydrogel is formed by cross-linking of aldehyde groups on BNPs with amine groups on CMCS via reversible Schiff base bonds, with CD and ICI loaded separately into BNPs and CMCS network. BNP/CMCS nanohydrogel maintained the activity of the biomolecules and released drugs in a sustained manner over a 7 day period. The adhesive property, through the formation of Schiff bases with peritoneal tissues, confers BNPs with an extended residence time in the peritoneal cavity after being released from the nanohydrogel. In a mouse model, BNP/CMCS nanohydrogel loaded with paclitaxel (PTX) and anti-PD-1 antibodies (αPD-1) significantly suppressed peritoneal metastasis of OC compared to all other tested groups. In addition, no systemic toxicity of nanohydrogel-loaded PTX and αPD-1 was observed during the treatment, which supports potential translational applications of this delivery system.

Construction of Hierarchically Biomimetic Iron Oxide Nanosystems for Macrophage Repolarization-Promoted Immune Checkpoint Blockade of Cancer Immunotherapy.

Cancer immunotherapy is developing as the mainstream strategy for treatment of cancer. However, the interaction between the programmed cell death protein-1 (PD-1) and the programmed death ligand 1 (PD-L1) restricts T cell proliferation, resulting in the immune escape of tumor cells. Recently, immune checkpoint inhibitor therapy has achieved clinical success in tumor treatment through blocking the PD-1/PD-L1 checkpoint pathway. However, the presence of M2 tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) will inhibit antitumor immune responses and facilitate tumor growth, which can weaken the effectiveness of immune checkpoint inhibitor therapy. The repolarization of M2 TAMs into M1 TAMs can induce the immune response to secrete proinflammatory factors and active T cells to attack tumor cells. Herein, hollow iron oxide (Fe3O4) nanoparticles (NPs) were prepared for reprogramming M2 TAMs into M1 TAMs. BMS-202, a small-molecule PD-1/PD-L1 inhibitor that has a lower price, higher stability, lower immunogenicity, and higher tumor penetration ability compared with antibodies, was loaded together with pH-sensitive NaHCO3 inside hollow Fe3O4 NPs, followed by wrapping with macrophage membranes. The formed biomimetic FBN@M could produce gaseous carbon dioxide (CO2) from NaHCO3 in response to the acidic TME, breaking up the macrophage membranes to release BMS-202. A series of in vitro and in vivo assessments revealed that FBN@M could reprogram M2 TAMs into M1 TAMs and block the PD-1/PD-L1 pathway, which eventually induced T cell activation and the secretion of TNF-α and IFN-γ to kill the tumor cells. FBN@M has shown a significant immunotherapeutic efficacy for tumor treatment.

Design, synthesis, and evaluation of antitumor activity of 2-arylmethoxy-4-(2-fluoromethyl-biphenyl-3-ylmethoxy) benzylamine derivatives as PD-1/PD-l1 inhibitors.

A series of novel 2-arylmethoxy-4-(2-fluoromethyl-biphenyl-3-ylmethoxy) benzylamine derivatives was designed, synthesized, and evaluated for their antitumor effects as PD-1/PD-L1 inhibitors both in vitro and in vivo. Firstly, the ability of these compounds to block the PD-1/PD-L1 immune checkpoint was assessed using the homogeneous time-resolved fluorescence (HTRF) assay. Two of the compounds can strongly block the PD-1/PD-L1 interaction, with IC50 values of less than 10 nM, notably, compound HD10 exhibited significant clinical potential by inhibiting the PD-1/PD-L1 interaction with an IC50 value of 3.1 nM. Further microscale thermophoresis (MST) analysis demonstrated that HD10 had strong interaction with PD-L1 protein. Co-crystal structure (2.7 Å) analysis of HD10 in complex with the PD-L1 protein revealed a strong affinity between the compound and the target PD-L1 dimer. This provides a solid theoretical basis for further in vitro and in vivo studies. Next, a typical cell-based experiment demonstrated that HD10 could remarkably prevent the interaction of hPD-1 293 T cells from human recombinant PD-L1 protein, effectively restoring T cell function, and promoting IFN-γ secretion in a dose-dependent manner. Moreover, HD10 was effective in suppressing tumor growth (TGI = 57.31 %) in a PD-1/PD-L1 humanized mouse model without obvious toxicity. Flow cytometry, qPCR, and immunohistochemistry data suggested that HD10 inhibits tumor growth by activating the immune system in vivo. Based on these results, it seems likely that HD10 is a promising clinical candidate that should be further investigated.

Multifaceted Carbonized Metal-Organic Frameworks Synergize with Immune Checkpoint Inhibitors for Precision and Augmented Cuproptosis Cancer Therapy.

The discovery of cuproptosis, a copper-dependent mechanism of programmed cell death, has provided a way for cancer treatment. However, cuproptosis has inherent limitations, including potential cellular harm, the lack of targeting, and insufficient efficacy as a standalone treatment. Therefore, exogenously controlled combination treatments have emerged as key strategies for cuproptosis-based oncotherapy. In this study, a Cu2-xSe@cMOF nanoplatform was constructed for combined sonodynamic/cuproptosis/gas therapy. This platform enabled precise cancer cotreatment, with external control allowing the selective induction of cuproptosis in cancer cells. This approach effectively prevented cancer metastasis and recurrence. Furthermore, Cu2-xSe@cMOF was combined with the antiprogrammed cell death protein ligand-1 antibody (aPD-L1), and this combination maximized the advantages of cuproptosis and immune checkpoint therapy. Additionally, under ultrasound irradiation, the H2Se gas generated from Cu2-xSe@cMOF induced cytotoxicity in cancer cells. Further, it generated reactive oxygen species, which hindered cell survival and proliferation. This study reports an externally controlled system for cuproptosis induction that combines a carbonized metal-organic framework with aPD-L1 to enhance cancer treatment. This precision and reinforced cuproptosis cancer therapy platform could be valuable as an effective therapeutic agent to reduce cancer mortality and morbidity in the future.

C2-Symmetrical Terphenyl Derivatives as Small Molecule Inhibitors of Programmed Cell Death 1/Programmed Death Ligand 1 Protein-Protein Interaction.

The PD-1/PD-L1 complex is an immune checkpoint responsible for regulating the natural immune response, but also allows tumors to escape immune surveillance. Inhibition of the PD-1/PD-L1 axis positively contributes to the efficacy of cancer treatment. The only available therapeutics targeting PD-1/PD-L1 are monoclonal antibody-based drugs, which have several limitations. Therefore, small molecule compounds are emerging as an attractive alternative that can potentially overcome the drawbacks of mAb-based therapy. In this article, we present a novel class of small molecule compounds based on the terphenyl scaffold that bind to PD-L1. The general architecture of the presented structures is characterized by axial symmetry and consists of three elements: an m-terphenyl core, an additional aromatic ring, and a solubilizing agent. Using molecular docking, we designed a series of final compounds, which were subsequently synthesized and tested in HTRF assay and NMR binding assay to evaluate their activity. In addition, we performed an in-depth analysis of the mutual arrangement of the phenyl rings of the terphenyl core within the binding pocket of PD-L1 and found several correlations between the plane angle values and the affinity of the compounds towards the protein.

Aptamer-assisted phage display: enhancing checkpoint inhibition with a peptide and an aptamer targeting distinct sites on a single PD-L1 protein.

Utilizing a novel approach known as aptamer-assisted phage display (APD), we identified an anti-PD-L1 peptide, NV Pep, capable of simultaneous binding to PD-L1 alongside the DNA aptamer MJ5C. Combined inhibition using NV Pep and MJ5C demonstrated significant enhancement compared to individual ligands against the PD-1/PD-L1 interaction.

Identification of novel PD-1/PD-L1 small molecule inhibitors: virtual screening, synthesis and in vitro characterisation.

The PD-1/PD-L1 pathway is considered as one of the most promising immune checkpoints in tumour immunotherapy. However, researchers are faced with the inherent limitations of antibodies, driving them to pursue PD-L1 small molecule inhibitors. Virtual screening followed by experimental validation is a proven approach to discover active compounds. In this study, we employed multistage virtual screening methods to screen multiple compound databases to predict new PD-1/PD-L1 ligands. 35 compounds were proposed by combined analysis of fitness scores, interaction pattern and MM-GBSA binding affinities. Enzymatic assay confirmed that 10 out of 35 ligands were potential PD-L1 inhibitors, with inhibitory rate higher than 50% at the concentration of 30 µM. Among them, ZDS20 was identified as the most effective inhibitor with low micromolar activity (IC50 = 3.27 µM). Altogether, ZDS20 carrying novel scaffold was identified and could serve as a lead for the development of new classes of PD-L1 inhibitors.

Discovery of Novel Proteolysis-Targeting Chimera Molecules as Degraders of Programmed Cell Death-Ligand 1 for Breast Cancer Therapy.

The immune checkpoint blockade represents a pivotal strategy for tumor immunotherapy. At present, various programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) monoclonal antibodies have been successfully applied to tumor treatment. Additionally, numerous small molecule inhibitors of the PD-1/PD-L1 interaction have also been developed, with some advancing into clinical trials. Here, a novel PD-L1 proteolysis-targeting chimera (PROTAC) library was designed and synthesized utilizing the PD-L1 inhibitor BMS202 and the E3 ligand PG as foundational components. Among these, we identified a highly potent molecule PA8 for PD-L1 degradation in 4T1 cells (DC50 = 0.609 µM). Significantly, compound PA8 potentially inhibits 4T1 cell growth both in vitro and in vivo. Further mechanistic studies revealed that PA8 effectively promoted the immune activation of model mice. Thus, these results suggest that PA8 could be a novel strategy for cancer immunotherapy in the 4T1 tumor model. Although PA8 exhibits weaker degradation activity in some human cancer cells, it still provides a certain basis for further research on PD-L1 PROTAC.

In Search of Better Peptide-(Derived from PD-L2)-Based Immune Checkpoint Inhibitors.

Current anti-cancer immune checkpoint therapy relies on antibodies that primarily target the PD-1/PD-L1(-L2) negative regulatory pathway. Although very successful in some cases for certain cancers, these antibodies do not help most patients who, presumably, should benefit from this type of therapy. Therefore, an unmet clinical need for novel, more effective drugs targeting immune checkpoints remains. We have developed a series of high-potency peptide inhibitors interfering with PD-1/PD-L1(-L2) protein-protein interaction. Our best peptide inhibitors are 12 and 14 amino acids long and show sub-micromolar IC50 inhibitory activity in the in vitro assay. The positioning of the peptides within the PD-1 binding site is explored by extensive modeling. It is further supported by 2D NMR studies of PD-1/peptide complexes. These results reflect substantial progress in the development of immune checkpoint inhibitors using peptidomimetics.

Based on polydopamine-coated metal organic framework multifunctional nanoplatform for enhanced photothermal/sonodynamicand treatment combined with checkpoint blockade therapy.

To overcome the low efficacy of sonodynamic therapy (SDT) caused by hypoxia in the tumor microenvironment, we developed a multiple anti-tumor nanoplatform with synergistic SDT, photothermal therapy (PTT), and ferroptosis effects. PCN-224@FcCaO2/Mn/dihydroartemisinin/imiquimod/PDA (PFC) was prepared by modified with dihydroartemisinin (DHA), imiquimod (R837), CaO2, ferrocene (Fc) and Mn2+ on the PCN-224 (Cu) to achieve self-replenishment of H2O2/O2 and GSH consumption. FcCaO2 decomposed into H2O2 in the tumor microenvironment, triggering the Fenton effect to produce OH, and Cu2+ reduced the potential loss of OH by the depletion of GSH. Under ultrasonic (US) and laser irradiation, PFC exhibits exciting PTT and SDT effects from polydopamine (PDA) and PCN-224. Mn2+ not only promoted the reaction of H2O2 to produce O2 to effectively enhance SDT but also induced tumor cell apoptosis by Mn2+ combined with DHA. PFC induced ferroptosis via Fe interaction with DHA to produce ROS and reduce the expression of GPX4. The released R837 and tumor-associated antigens from SDT/PTT can produce damage associated molecular patterns (DAMPs), which can initiate adaptive immune responses to kill cancer cells, and released again to promote the tumor immune cycle. What's more, SDT/PTT and ferroptosis combined with aPD-L1 can effectively suppress both primary and distant tumor growth.

Discovery of Small and Bifunctional Molecules Targeting PD-L1/CD73 for Cancer Dual Immunotherapy.

In this work, a series of bifunctional PD-L1/CD73 (cluster of differentiation 73) small-molecule inhibitors were designed and synthesized. Among them, CC-5 showed the strongest PD-L1 inhibitory effects with an IC50 of 6 nM and potent anti-CD73 activity with an IC50 of 0.773 µM. The high PD-L1/CD73 inhibitory activity of CC-5 was further confirmed by SPR assays with KD of 182 nM for human PD-L1 and 101 nM for CD73, respectively. Importantly, CC-5 significantly suppressed tumor growth in a CT26 and B16-F10 tumor model with TGI of 64.3% and 39.6%, respectively. Immunohistochemical (IHC) and flow cytometry analysis of tumor-infiltrating lymphocytes (TILs) indicated that CC-5 exerted anticancer effects via activating the tumor immune microenvironment. Collectively, CC-5 represents the first dual PD-L1/CD73 inhibitor worthy of further research as a bifunctional immunotherapeutic agent.

Discovery of Novel Small-Molecule-Based Potential PD-L1/EGFR Dual Inhibitors with High Druggability for Glioblastoma Immunotherapy.

Based on the close relationship between programmed death protein ligand 1 (PD-L1) and epidermal growth factor receptor (EGFR) in glioblastoma (GBM), we designed and synthesized a series of small molecules as potential dual inhibitors of EGFR and PD-L1. Among them, compound EP26 exhibited the highest inhibitory activity against EGFR (IC50 = 37.5 nM) and PD-1/PD-L1 interaction (IC50 = 1.77 µM). In addition, EP26 displayed superior in vitro antiproliferative activities and in vitro immunomodulatory effects by promoting U87MG cell death in a U87MG/Jurkat cell coculture model. Furthermore, EP26 possessed favorable pharmacokinetic properties (F = 22%) and inhibited tumor growth (TGI = 92.0%) in a GBM mouse model more effectively than Gefitinib (77.2%) and NP19 (82.8%). Moreover, EP26 increased CD4+ cells and CD8+ cells in tumor microenvironment. Collectively, these results suggest that EP26 represents the first small-molecule-based PD-L1/EGFR dual inhibitor deserving further investigation as an immunomodulating agent for cancer treatment.