Small-molecule agents for cancer immunotherapy

Identification of small molecule activators targeting TYK2 pseudokinase domain

Tyrosine kinase 2 (TYK2) plays a crucial role in both adaptive and innate immune responses. The catalytic activity of the TYK2 JH1 kinase domain is controlled by the TYK2 JH2 pseudokinase domain and stabilized to maintain its inactive state until the upstream receptor activations. Here, we report the discovery of aminopyridine analogs as novel TYK2 activators through structural modification of a known JH2 binder. Compound 16b demonstrated a dose-dependent increase in TYK2 enzymatic activity.

Smart self-transforming nano-systems for overcoming biological barrier and enhancing tumor treatment efficacy

Nanomedicines need to overcome multiple biological barriers in the body to reach the target area. However, traditional nanomedicines with constant physicochemical properties are not sufficient to meet the diverse and sometimes conflicting requirements during in vivo transport, making it difficult to penetrate various biological barriers, resulting in suboptimal drug delivery efficiency. Smart self-transforming nano-systems (SSTNs), capable of altering their own physicochemical properties (including size, charge, hydrophobicity, stiffness, morphology, etc.) under different physiological conditions, hold the potential to break through multiple biological barriers, thereby improving drug delivery efficiency and the efficacy of cancer treatment. In this review, we first summarize the design strategies of five most popular SSTNs (such as size-, charge-, hydrophilicity-, stiffness-, and morphology-self-transforming nano-systems), and then delve into their biomedical applications in enhancing circulation time, tissue penetration, and cellular uptake. Finally, we discuss the opportunities and challenges that SSTNs face in the future for cancer treatment and diagnosis.

Nanomaterials-mediated adenosine pathway inhibition for strengthening cancer immunotherapy

Immunotherapy has developed into an attractive tumor treatment strategy. However, the existence of an immunosuppressive tumor microenvironment (ITME) greatly reduces the efficacy of immunotherapy. Adenosine (ADO) is one of the vital negative feedbacks in ITME, which inhibits antigen presentation and immune cell activation by binding to adenosine receptors (ADORs), thus tremendously suppressing immune response. Currently, the treatment effect of numerous inhibitors targeting the ADO pathway has been demonstrated in early clinical trials of various tumors. Nevertheless, the clinical application of these inhibitors is still plagued by diverse issues, such as short half-life, a single administration route, low bioavailability, etc. With the progress of nanotechnology, the delivery system of ADO inhibitors based on nanomaterials can solve the above problems. This review discusses the utilization of nanomaterials as a prospective method to inhibit ADO pathway and enhance immunotherapy outcomes. Specifically, the immunosuppressive mechanisms of ADO are summarized, and the corresponding intervention strategies are proposed. Then plentiful nanomaterials targeting the ADO pathway are highlighted, including phospholipids and polymers-based nanomaterials, mesoporous nanomaterials, biomimetic nanomaterials and metal-based nanomaterials. Finally, the outlook and challenges about nanomaterials-mediated ADO pathway inhibition were outlined, expecting to promote the clinical application of ADO inhibitor nanomedicines.

Investigating the delivery of PD-L1-targeted immunoliposomes in a dynamic cervical cancer-on-a-chip model

The recent approval of pembrolizumab in recurrent or metastatic cervical cancer warrants further investigations into the usefulness of immunotherapies for more durable and less radical interventions. In this study, the targeting potential of anti-PD-L1-functionalized immunoliposomes was tested in a 3D in vitro cervical cancer-on-a-chip model. Immunolipsomes were synthesized and decorated externally with monovalent anti-PD-L1 Fab' fragments of commercially available atezolizumab. Cervical cancer cell lines with varying levels of PD-L1 expression were cultured as spheroids embedded in a collagen I matrix, and treated under flow of culture media. Flow cytometry and live-cell confocal imaging were used to measure the interactions and uptake of untargeted liposomes and immunoliposomes in this panel of cell lines. The immunoliposomes retained specific functionality regardless of protein corona formation in high serum environments. As such, spheroids expressing high levels of PD-L1 preferentially internalized immunoliposomes in a 3D environment with extracellular matrix present, while low PD-L1-expressing cell lines showed no preference for either formulation. Importantly, treatments performed in monolayer cultures (on plastic) showed no differences between immuno- and untargeted liposome uptake, including the way in which the endocytosed liposomes are trafficked subcellularly. This study demonstrates the importance of both active and passive accumulation strategies to achieve nanoparticle targeting. Immunoliposomes remain a promising platform for the development of targeted nanotherapies against cervical cancers. However, initial functional tests did not translate directly to biological performance and this should be kept in mind for future formulations. Furthermore, the in vitro model developed appeared useful for visualizing liposome uptake in a 3D, live tissue environment and represents a cost-effective and reproducible model for future studies.

The role of tumor-derived exosomal LncRNA in tumor metastasis

Tumor metastasis regulated by multiple complicated pathways is closely related to variations in the tumor microenvironment. Exosomes can regulate the tumor microenvironment through various mechanisms. Exosomes derived from tumor cells carry a variety of substances, including long non-coding RNAs (lncRNAs), play important roles in intercellular communication and act as critical determinants influencing tumor metastasis. In this review, we elaborate on several pivotal processes through which lncRNAs regulate tumor metastasis, including the regulation of epithelial‒mesenchymal transition, promotion of angiogenesis and lymphangiogenesis, enhancement of the stemness of tumor cells, and evasion of immune clearance. Additionally, we comprehensively summarized a diverse array of potential tumor-derived exosomal lncRNA biomarkers to facilitate accurate diagnosis and prognosis in a clinical setting.

Method for Screening Sodium Cyanoborohydride for Free Cyanide Content and Its Impact on Bioconjugation Chemistry

Sodium cyanoborohydride (CBH) is commonly used as a mild reducing agent in the reductive amination of aldehydes and free amines. Within the pharmaceutical industry, this reaction is employed in the bioconjugation of proteins and peptides. Free cyanide species such as HCN and NaCN are known residual impurities in CBH that can contribute to the formation of undesired side products including cyanoamines and cyanohydrins. In commercial processes, the potential for bound cyanated species requires an analytical control strategy to monitor and mitigate any risk to human health. Given these concerns, minimization of cyanated side products is of utmost priority and can be achieved through a robust control strategy of quantitative screening of starting materials for free cyanide. Alternative risk mitigation strategies such as purification of bound cyanide containing species to pure species are less effective due to minor chemical differences between the expected product and bound cyanide species. Herein, we present a simple chromatographic assay for the quantitation of free cyanide in the raw material sodium cyanoborohydride. Method development, robustness evaluation, and scientific soundness assessment are reported with excellent linearity, accuracy, precision, and specificity. Additionally, this method was applied for the evaluation of raw material supplied from 10 commercial sources, none of which report a specification for free cyanide within their certificate of analysis. The measured free cyanide from these vendors ranged from 8 to 80 mM concentration, thereby confirming the value of screening these raw materials. Finally, we demonstrate the impact of free cyanide on a model bioconjugation reaction between ornithine and glyceraldehyde.

Small molecule inhibitors targeting PD-L1, CTLA4, VISTA, TIM-3, and LAG3 for cancer immunotherapy (2020-2024)

Cancer immunotherapy, leveraging antibodies, excels in targeting efficacy but faces hurdles in tissue penetration, oral delivery, and prolonged half-life, with costly production and risk of adverse immunogenic effects. In contrast, small molecule immuno-oncology agents provide favorable pharmacokinetic properties and benign toxicity profiles. These agents are well-positioned to address the limitations of antibody-based immunotherapies, augment existing treatment modalities, and achieve synergistic effects when combined with antibodies. This review, for the first time, summarizes the recent advances (2020-2024) in small molecule inhibitors targeting PD-1/PD-L1, CTLA4, VISTA, TIM-3, and LAG3, highlighting rational design, benefits, and potential limitations. It also outlines the prospects for small-molecule immunotherapy.

Recent advances in reactive oxygen species (ROS)-responsive drug delivery systems for photodynamic therapy of cancer

Reactive oxygen species (ROS)-responsive drug delivery systems (DDSs) have garnered significant attention in cancer research because of their potential for precise spatiotemporal drug release tailored to high ROS levels within tumors. Despite the challenges posed by ROS distribution heterogeneity and endogenous supply constraints, this review highlights the strategic alliance of ROS-responsive DDSs with photodynamic therapy (PDT), enabling selective drug delivery and leveraging PDT-induced ROS for enhanced therapeutic efficacy. This review delves into the biological importance of ROS in cancer progression and treatment. We elucidate in detail the operational mechanisms of ROS-responsive linkers, including thioether, thioketal, selenide, diselencide, telluride and aryl boronic acids/esters, as well as the latest developments in ROS-responsive nanomedicines that integrate with PDT strategies. These insights are intended to inspire the design of innovative ROS-responsive nanocarriers for enhanced cancer PDT.

Photoimmunotherapy for cancer treatment based on organic small molecules: Recent strategies and future directions

Photodynamic therapy (PDT) is considered as a promising anticancer approach, owning to its high efficiency and spatiotemporal selectivity. Ample evidence indicated that PDT can trigger immunogenic cell death by releasing antigens that activate immune cells to promote anti-tumor immunity. Nevertheless, the inherent nature of tumors and their complex heterogeneity often limits the efficiency of PDT, which can be overcome with a novel strategy of photo-immunotherapy (PIT) strategy. By exploring the principles of PDT induction and ICD enhancement, combined with other therapies such as chemotherapy or immune checkpoint blockade, the tailored solutions can be designed to address specific challenges of drug resistance, hypoxic conditions, and tumor immunosuppressive microenvironments (TIMEs), which enables targeted enhancement of systemic immunity to address most distant and recurrent cancers. The present article summarizes the specific strategies of PIT and discusses recent existing limitations. More importantly, we anticipate that the perspectives presented herein will help address the clinical translation challenges associated with PIT.

A systematic review of cardiovascular toxicities induced by cancer immune therapies: Underlying mechanisms, clinical manifestations and therapeutic approaches

Immunotherapy has revolutionized the management of various types of cancers, even those previously deemed untreatable. Nonetheless, these medications have been associated with inflammation and damage across various organs. These challenges are exemplified by the adverse cardiovascular impacts of cancer immunotherapy, which need comprehensive understanding, clarification, and management integrated into the overall care of cancer patients. Numerous anticancer immunotherapies have been linked to the prevalence and severity of cardiovascular toxicity. These challenges emphasize the importance of conducting fundamental and applied research to elucidate disease causes, discover prognostic indicators, enhance diagnostic methods, and create successful therapies. Despite the acknowledged importance of T cells, there remains a knowledge gap regarding the inciting antigens, the reasons for their recognition, and the mechanisms of how they contribute to cardiac cell injury. In this review, we summarize the molecular mechanism, epidemiology, diagnosis, pathophysiology and corresponding treatment of cardiovascular toxicity induced by immunotherapy, including immune checkpoint inhibitors (ICIs), adoptive cell therapies (ACT), and bi-specific T-cell engagers (BiTEs) among others. By elucidating these aspects, we aim to provide a better understanding of immunotherapies in cancer treatment and offer guidance for their clinical application.

PKCα inhibitors promote breast cancer immune evasion by maintaining PD-L1 stability

Protein kinase C α (PKCα) regulates diverse biological functions of cancer cells and is a promising therapeutic target. However, clinical trials of PKC-targeted therapies have not yielded satisfactory results. Recent studies have also indicated a tumor-suppressive role of PKCs via unclear molecular mechanisms. In this study, we found that PKCα inhibition enhances CD8+ T-cell-mediated tumor evasion and abolishes antitumor activity in immunocompetent mice. We further identified PKCα as a critical regulator of programmed cell death-ligand 1 (PD-L1) and found that it enhances T-cell-dependent antitumor immunity in breast cancer by interacting with PD-L1 and suppressing PD-L1 expression. We demonstrated that PKCα-mediated PD-L1 phosphorylation promotes PD-L1 degradation through β transducin repeat-containing protein. Notably, the efficacy of PKCα inhibitors was intensified by synergizing with anti-PD-L1 mAb therapy to boost antitumor T-cell immunity in vivo. Clinical analysis revealed that PKCα expression is positively correlated with T-cell function and the interferon-gamma signature in patients with breast cancer. This study demonstrated the antitumor capability of PKCα, identified potential therapeutic strategies to avoid tumor evasion via PKC-targeted therapies, and provided a proof of concept for targeting PKCα in combination with anti-PD-L1 mAb therapy as a potential therapeutic approach against breast cancer, especially TNBC.

Comprehensive analysis of CXCL10 and MIP-3a reveals their potential clinical application in hepatocellular carcinoma

Chemokines play a crucial role in the pathogenesis of patients with hepatocellular carcinoma (HCC). The expression levels of interferon-γ-induced protein-10 (CXCL10) and macrophage inflammatory protein-3α (MIP-3a) were investigated to clarify their clinical significance in HCC. The protein levels of CXCL10 and MIP-3a in the serum of 105 HBV-associated HCC patients, 50 patients with liver cirrhosis (LC), 50 patients with chronic hepatitis B (CHB) and 50 healthy donors (HC) were detected by liquid chip technology (Luminex) or ELISA. In addition, their mRNA levels were also determined in liver cancer and adjacent cancer tissue (paracancer; ParaCa) from 65 HCC patients. The online database UALCAN was used to analyze the association between CXCL10 and pathological manifestations of liver cancer. In addition, the diagnostic value of CXCL10/MIP-3a and AFP in HCC patients was determined by analyzing the Receiver Operating Characteristic Curve (ROC). The protein concentrations of CXCL10 and MIP-3a were significantly higher in the HCC group than in the LC, CHB and HC groups. CXCL10 in sera and liver cancer tissues is significantly positively correlated with ALT, but no significance between CXCL10 in ParaCa tissues and sera-ALT. Their mRNA is significantly higher in cancer tissues than in ParaCa tissues. The areas under the ROC curve of CXCL10, MIP-3a, CXCL10 and MIP-3a combined and AFP were 0.9169, 0.9261, 0.9299 and 0.7880, respectively. Elevated chemokines CXCL10 and MIP-3a in HCC patients may be associated with the clinical manifestation of HCC and could be a potential molecular marker for prognostic evaluation or a therapeutic target for HCC.

G protein-coupled receptor-mediated signaling of immunomodulation in tumor progression

G protein-coupled receptors (GPCRs) are essential contributors to tumor growth and metastasis due to their roles in immune cell regulation. Therefore, GPCRs are potential targets for cancer immunotherapy. Here, we discuss the current understanding of the roles of GPCRs and their signaling pathways in tumor progression from an immunocellular perspective. Additionally, we focus on the roles of GPCRs in regulating immune checkpoint proteins involved in immune evasion. Finally, we review the progress of clinical trials of GPCR-targeted drugs for cancer treatment, which may be combined with immunotherapy to improve treatment efficacy. This expanded understanding of the role of GPCRs may shed light on the mechanisms underlying tumor progression and provide a novel perspective on cancer immunotherapy.

Nanoparticles targeting the adenosine pathway for cancer immunotherapy

Cancer immunotherapy, as an emerging approach to cancer treatment, has tremendous potential for application. Compared to traditional methods such as surgery, chemotherapy, and radiation therapy, it has the ability to restore the patient's immune system, leading to long-term immune memory with less damage to normal tissues. However, immunotherapy has its limitations, including limited therapeutic efficacy, restricted patient populations, and inconsistent treatment responses. Finding effective immunotherapeutic approaches has become a key focus of its clinical application. The adenosine pathway is a recently discovered tumor immune regulatory signaling pathway. It can influence the metabolism and growth of tumor cells by acting through key enzymes in the adenosine pathway, thereby affecting the development of tumors. Therefore, inhibiting the adenosine pathway is an effective cancer immunotherapy. Common adenosine pathway inhibitors include small molecules and antibody proteins, and extensive preclinical trials have demonstrated their effectiveness in inhibiting tumor growth. The short half-life, low bioavailability, and single administration route of adenosine pathway inhibitors limit their clinical application. With the advent of nanotechnology, nano-delivery of adenosine pathway inhibitors has addressed these issues. Compared to traditional drugs, nano-drugs extend the drug's circulation time and improve its distribution within the body. They also offer targeting capabilities and have low toxic side effects, making them very promising for future applications. In this review, we discuss the mechanism of the adenosine pathway in tumor immune suppression, the clinical applications of adenosine pathway inhibitors, and nano-delivery based on adenosine pathway inhibitors. In the final part of this article, we also briefly discuss the technical issues and challenges currently present in nano-delivery of adenosine pathway inhibitors, with the hope of advancing the progress of adenosine inhibitor nano-drugs in clinical treatment.

Advances in the discovery of activin receptor-like kinase 5 (ALK5) inhibitors

Activin receptor‑like kinase-5 (ALK5) is an outstanding member of the transforming growth factor-β (TGF-β) family. (TGF-β) signaling pathway integrates pleiotropic proteins that regulate various cellular processes such as growth, proliferation, and differentiation. Dysregulation within the signaling pathway can cause variety of diseases, such as fibrosis, cardiovascular disease, and especially cancer, rendering ALK5 a potential drug target. Hence, various small molecules have been designed and synthesized as potent ALK5 inhibitors. In this review, we shed light on the current ATP-competitive inhibitors of ALK5 through diverse heterocyclic based scaffolds that are in clinical or pre-clinical phases of development. Moreover, we focused on the binding interactions of the compounds to the ATP binding site and the structure-activity relationship (SAR) of each scaffold, revealing new scopes for designing novel candidates with enhanced selectivity and metabolic profiles.