Research progress of STAT3-based dual inhibitors for cancer therapy

Novel inhibitors of STAT3: an updated patent review (2022-present)

INTRODUCTION

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT protein family, serves as both a signal transducer and a transcription factor. Previous studies have highlighted its pivotal roles in regulating cell proliferation, differentiation, apoptosis, as well as immune and inflammatory responses. Consequently, targeting STAT3 has emerged as a promising therapeutic strategy for addressing related diseases.

AREAS COVERED

This review offers a comprehensive summary of the progress in discovering STAT3 inhibitors, with a focus on their structural diversity and structure-activity relationships as presented in patent literature from 2022 to the present.

EXPERT OPINION

Over the past decades, significant progress has transformed STAT3 into a target of interest for drug development. Despite these advances, no STAT3-targeting drugs have successfully progressed through late-phase clinical trials, largely due to challenges such as limited selectivity and undesirable side effects. These obstacles highlight the inherent complexity of developing safe and effective STAT3 inhibitors. Nevertheless, STAT3 remains a highly promising therapeutic target, and ongoing advancements in this field hold the potential to unlock novel strategies for addressing STAT3-related diseases.

STAT3 Signaling Pathway in Health and Disease

Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor involved in multiple physiological and pathological processes. While STAT3 plays an essential role in homeostasis, its persistent activation has been implicated in the pathogenesis of various diseases, particularly cancer, bone-related diseases, autoimmune disorders, inflammatory diseases, cardiovascular diseases, and neurodegenerative conditions. The interleukin-6/Janus kinase (JAK)/STAT3 signaling axis is central to STAT3 activation, influencing tumor microenvironment remodeling, angiogenesis, immune evasion, and therapy resistance. Despite extensive research, the precise mechanisms underlying dysregulated STAT3 signaling in disease progression remain incompletely understood, and no United States Food and Drug Administration (USFDA)-approved direct STAT3 inhibitors currently exist. This review provides a comprehensive evaluation of STAT3's role in health and disease, emphasizing its involvement in cancer stem cell maintenance, metastasis, inflammation, and drug resistance. We systematically discuss therapeutic strategies, including JAK inhibitors (tofacitinib, ruxolitinib), Src Homology 2 domain inhibitors (S3I-201, STATTIC), antisense oligonucleotides (AZD9150), and nanomedicine-based drug delivery systems, which enhance specificity and bioavailability while reducing toxicity. By integrating molecular mechanisms, disease pathology, and emerging therapeutic interventions, this review fills a critical knowledge gap in STAT3-targeted therapy. Our insights into STAT3 signaling crosstalk, epigenetic regulation, and resistance mechanisms offer a foundation for developing next-generation STAT3 inhibitors with greater clinical efficacy and translational potential.

Filgotinib Improves Experimental Pulmonary Fibrosis by Modulating JAK1/STAT3/SOCS3/IL-17A Signalling

BACKGROUND

Regulatory agencies in Europe and Japan have approved filgotinib, a selective JAK1 inhibitor, for use in treating rheumatoid arthritis, but its effect and mechanism of action in treating pulmonary fibrosis remain unclear.

METHODS

We performed an in vivo investigation in rats on filgotinib's effect on pulmonary fibrosis resulting from the intratracheal infusion of bleomycin (BLM). Then, we focused on the mechanisms by which filgotinib inhibits experimentally induced pulmonary fibrosis in vitro by determining its effect on TGF-β1-induced proliferation of mouse lung fibroblasts.

RESULTS

Continuous gavage of filgotinib at 20 mg/kg for 14 days elicited protective effects in the BLM-induced rat experimental pulmonary fibrosis model, as reflected in changes in Hounsfield units as an indicator of overall pulmonary function and in the lung coefficient and lung microscopic pathology scores as indicators of gross pulmonary pathology. Protein expression levels of IL-17A, phosphorylated tyrosine kinase (p-JAK1), p-STAT3 and cytokine signal transduction inhibitor 3 (SOCS3) were also changed. In in vitro studies, filgotinib at 1 μM reduced TGF-β1-induced fibroblast proliferation and produced lower levels of IL-17A, p-JAK1 and p-STAT3, but higher SOCS3.

CONCLUSIONS

Filgotinib appeared to alleviate experimental pulmonary fibrosis by reducing fibroblast proliferation via inhibition of the JAK1/STAT3/SOCS3/IL-17A pathway.

An allosteric inhibitor targeting the STAT3 coiled-coil domain selectively suppresses proliferation of breast cancer

Signal transducer and activator of transcription 3 (STAT3) remains a challenging and attractive therapeutic target in cancer research. The coiled-coil domain (CCD) of STAT3 represents a novel site for targeted intervention, distinct from the Src-homology 2 domain, and plays a crucial role in regulating the earlier activation and biological function of STAT3 in cell proliferation, survival and invasion of breast cancer cells. We previously reported K116, N'-(1-(2,4-dihydroxyphenyl)ethylidene)thiophene-2-carbohydrazide, as a potent allosteric inhibitor specifically targeting the STAT3 CCD. This study aimed to investigate the antiproliferation effect of K116 on breast cancer cells in vitro and in vivo. The results showed that K116 inhibited the proliferation of breast cancer cell lines in a dose-dependent manner by reducing the phosphorylation of STAT3 Lyr705 and did not inhibit the proliferation of HGC-27 and A549 cells nor their STAT3 Lyr705 phosphorylation. Compared with Stattic (STAT3 SH2 inhibitor), K116 selectively inhibited the proliferation of breast cancer cells. Furthermore, K116 (20 μM) directly monitored STAT3 stabilization and engagement within MDA-MB-468 cells, without affecting STAT1, STAT5, and Akt1. K116 induced apoptosis and inhibited migration as well as pY705STAT3 nuclear translocation and transcriptional activity of STAT3. In addition, K116 (30 mg kg-1) markedly suppressed tumor growth and inhibited STAT3 activity in a 4T1 cell-derived murine breast cancer model. Overall, our results provided pharmacological evidence supporting future clinical investigation of K116 as a promising STAT3 CCD allosteric inhibitor for breast cancer treatment.

Shared molecular, cellular, and environmental hallmarks in cardiovascular disease and cancer: Any place for drug repurposing?

Cancer and cardiovascular disease (CVD) are the 2 biggest killers worldwide. Specific treatments have been developed for the 2 diseases. However, mutual therapeutic targets should be considered because of the overlap of cellular and molecular mechanisms. Cancer research has grown at a fast pace, leading to an increasing number of new mechanistic treatments. Some of these drugs could prove useful for treating CVD, which realizes the concept of cancer drug repurposing. This review provides a comprehensive outline of the shared hallmarks of cancer and CVD, primarily ischemic heart disease and heart failure. We focus on chronic inflammation, altered immune response, stromal and vascular cell activation, and underlying signaling pathways causing pathological tissue remodeling. There is an obvious scope for targeting those shared mechanisms, thereby achieving reciprocal preventive and therapeutic benefits. Major attention is devoted to illustrating the logic, advantages, challenges, and viable examples of drug repurposing and discussing the potential influence of sex, gender, age, and ethnicity in realizing this approach. Artificial intelligence will help to refine the personalized application of drug repurposing for patients with CVD. SIGNIFICANCE STATEMENT: Cancer and cardiovascular disease (CVD), the 2 biggest killers worldwide, share several underlying cellular and molecular mechanisms. So far, specific therapies have been developed to tackle the 2 diseases. However, the development of new cardiovascular drugs has been slow compared with cancer drugs. Understanding the intersection between pathological mechanisms of the 2 diseases provides the basis for repurposing cancer therapeutics for CVD treatment. This approach could allow the rapid development of new drugs for patients with CVDs.

Computational screening and molecular dynamics of natural compounds targeting the SH2 domain of STAT3: a multitarget approach using network pharmacology

SH2 (Src Homology 2) domains play a crucial role in phosphotyrosine-mediated signaling and have emerged as promising drug targets, particularly in cancer therapy. STAT3 (Signal Transducer and Activator of Transcription 3), which contains an SH2 domain, plays a pivotal role in cancer progression and immune evasion because it facilitates the dimerization of STAT3, which is essential for their activation and subsequent nuclear translocation. SH2 domain-mediated STAT3 inhibition disrupts this binding, reduces phosphorylation of STAT3, and impairs dimerization. This study employed an in silico approach to screen potential natural compounds that could target the SH2 domain of STAT3 and inhibit its function. The phytomolecules (182455) were retrieved from the ZINC 15 database and were docked using various modes like HTVS, SP, and XP. The phytomolecules exhibiting higher binding affinity were selected. MM-GBSA was performed to determine binding free energy, and the QikProp tool was utilized to assess the pharmacokinetic properties of potential hit compounds, narrowing down the list of candidates. Molecular dynamics simulations, thermal MM-GBSA, and WaterMap analysis were performed on compounds that exhibited favorable binding affinities and pharmacokinetic characteristics. Based on docking scores and binding interactions, ZINC255200449, ZINC299817570, ZINC31167114, and ZINC67910988 were identified as potential STAT3 inhibitors. ZINC67910988 demonstrated superior stability in molecular dynamics simulation and WaterMap analysis. Furthermore, DFT was performed to determine energetic and electronic properties, and HOMO and LUMO sites were predicted for electronic structure calculation. Additionally, network pharmacology was performed to map the compounds' interactions within biological networks, highlighting their multitarget potential. Compound-target networks elucidate the relationships between compounds and multiple targets, along with their associated pathways and help to minimize off-target effects. The identified lead compound showed strong potential as a STAT3 inhibitor, warranting further validation through in vitro and in vivo studies.

Crosstalk and communication of cancer-associated fibroblasts with natural killer and dendritic cells: New frontiers and unveiled opportunities for cancer immunotherapy

Natural killer (NK) cells and dendritic cells (DCs) are critical mediators of anti-cancer immune responses. In addition to their individual roles, NK cells and DCs are involved in intercellular crosstalk which is essential for the initiation and coordination of adaptive immunity against cancer. However, NK cell and DC activity is often compromised in the tumor microenvironment (TME). Recently, much attention has been paid to one of the major components of the TME, the cancer-associated fibroblasts (CAFs), which not only contribute to extracellular matrix (ECM) deposition and tumor progression but also suppress immune cell functions. It is now well established that CAFs support T cell exclusion from tumor nests and regulate their cytotoxic activity. In contrast, little is currently known about their interaction with NK cells, and DCs. In this review, we describe the interaction of CAFs with NK cells and DCs, by secreting and expressing various mediators in the TME of adult solid tumors. We also provide a detailed overview of ongoing clinical studies evaluating the targeting of stromal factors alone or in combination with immunotherapy based on immune checkpoint inhibitors. Finally, we discuss currently available strategies for the selective depletion of detrimental CAFs and for a better understanding of their interaction with NK cells and DCs.

STAT3: Key targets of growth-promoting receptor positive breast cancer

Breast cancer has become the malignant tumor with the first incidence and the second mortality among female cancers. Most female breast cancers belong to luminal-type breast cancer and HER2-positive breast cancer. These breast cancer cells all have different driving genes, which constantly promote the proliferation and metastasis of breast cancer cells. Signal transducer and activator of transcription 3 (STAT3) is an important breast cancer-related gene, which can promote the progress of breast cancer. It has been proved in clinical and basic research that over-expressed and constitutively activated STAT3 is involved in the progress, proliferation, metastasis and chemotherapy resistance of breast cancer. STAT3 is an important key target in luminal-type breast cancer and HER2-positive cancer, which has an important impact on the curative effect of related treatments. In breast cancer, the activation of STAT3 will change the spatial position of STAT3 protein and cause different phenotypic changes of breast cancer cells. In the current basic research and clinical research, small molecule inhibitors activated by targeting STAT3 can effectively treat breast cancer, and enhance the efficacy level of related treatment methods for luminal-type and HER2-positive breast cancers.

The ubiquitin-specific protease 21 is critical for cancer cell mitochondrial function and regulates proliferation and migration

Ubiquitin-specific proteases (USPs) are the main members of deubiquitinases (DUBs) that catalyze removing ubiquitin chains from target proteins, thereby modulating their half-life and function. Enzymatic activity of USP21 regulates protein degradation which is critical for maintaining cell homeostasis. USP21 determines the stability of oncogenic proteins and therefore is implicated in carcinogenesis. In this study, we investigated the effect of USP21 deletion on cancer cell metabolism. Transcriptomic and proteomic analysis of USP21 KO HAP-1 cells revealed that endogenous USP21 is critical for the expression of genes and proteins involved in mitochondrial function. Additionally, we have found that the deletion of USP21 reduced STAT3 activation and STAT3-dependent gene and protein expression in cancer cells. Genetic deletion of USP21 impaired mitochondrial respiration and disturbed ATP production. This resulted in cellular consequences such as inhibition of cell proliferation and migration. Presented results provide new insights into the biology of USP21, suggesting novel mechanisms for controlling STAT3 activity and mitochondrial function in tumor cells. Taken together, our findings indicate that targeting USP21 dysregulates the energy status of cancer cells offering new perspectives for anticancer therapy.

Targeting the STAT3 pathway with STAT3 degraders

Signal transducer and activator of transcription 3 (STAT3) has been widely considered as a therapeutic target for various diseases, especially tumors. Thus far, several STAT3 inhibitors have been advanced to clinical trials; however, the development of STAT3 inhibitors is hindered by numerous dilemmas. Fortunately, STAT3 degraders represent an alternative and promising strategy to block STAT3, attracting extensive research interest. Here, we analyze the recent advancements of STAT3 degraders, including proteolysis targeting chimeras (PROTACs) and small-molecule natural products, focusing on their structures, mechanisms, and biological activities. We discuss the potential opportunities and challenges for developing STAT3 degraders. It is hoped that this Review will provide insights into the discovery of potent STAT3-targeting drugs.

Novel STAT3 oligonucleotide compounds suppress tumor growth and overcome the acquired resistance to sorafenib in hepatocellular carcinoma

Signal transducer and activator of transcription 3 (STAT3) plays an important role in the occurrence and progression of tumors, leading to resistance and poor prognosis. Activation of STAT3 signaling is frequently detected in hepatocellular carcinoma (HCC), but potent and less toxic STAT3 inhibitors have not been discovered. Here, based on antisense technology, we designed a series of stabilized modified antisense oligonucleotides targeting STAT3 mRNA (STAT3 ASOs). Treatment with STAT3 ASOs decreased the STAT3 mRNA and protein levels in HCC cells. STAT3 ASOs significantly inhibited the proliferation, survival, migration, and invasion of cancer cells by specifically perturbing STAT3 signaling. Treatment with STAT3 ASOs decreased the tumor burden in an HCC xenograft model. Moreover, aberrant STAT3 signaling activation is one of multiple signaling pathways involved in sorafenib resistance in HCC. STAT3 ASOs effectively sensitized resistant HCC cell lines to sorafenib in vitro and improved the inhibitory potency of sorafenib in a resistant HCC xenograft model. The developed STAT3 ASOs enrich the tools capable of targeting STAT3 and modulating STAT3 activity, serve as a promising strategy for treating HCC and other STAT3-addicted tumors, and alleviate the acquired resistance to sorafenib in HCC patients. A series of novel STAT3 antisense oligonucleotide were designed and showed potent anti-cancer efficacy in hepatocellular carcinoma in vitro and in vivo by targeting STAT3 signaling. Moreover, the selected STAT3 ASOs enhance sorafenib sensitivity in resistant cell model and xenograft model.

Colonic Tuft Cells: The Less-Recognized Therapeutic Targets in Inflammatory Bowel Disease and Colorectal Cancer

Tuft cells are more than guardian chemosensory elements of the digestive tract. They produce a variety of immunological effector molecules in response to stimulation; moreover, they are essential for defense against protozoa and nematodes. Beyond the description of their characteristics, this review aims to elucidate the potential pathogenic and therapeutic roles of colonic tuft cells in inflammatory bowel disease and colorectal cancer, focusing on their primarily immunomodulatory action. Regarding inflammatory bowel disease, tuft cells are implicated in both maintaining the integrity of the intestinal epithelial barrier and in tissue repair and regeneration processes. In addition to maintaining intestinal homeostasis, they display complex immune-regulatory functions. During the development of colorectal cancer, tuft cells can promote the epithelial-to-mesenchymal transition, alter the gastrointestinal microenvironment, and modulate both the anti-tumor immune response and the tumor microenvironment. A wide variety of their biological functions can be targeted for anti-inflammatory or anti-tumor therapies; however, the adverse side effects of immunomodulatory actions must be strictly considered.

Development of new thieno[2,3-d]pyrimidines as dual EGFR and STAT3 inhibitors endowed with anticancer and pro-apoptotic activities

In part due to the resilience of cellular feedback pathways that develop therapeutic resistance to targeting the EGFR alone, using EGFR inhibitors alone was demonstrated to be unsuccessful in clinical trials. The over-activation of the signal transducer/activator of transcription 3 (STAT3) during the administration of an EGFR inhibitor is expected to play a substantial part in the failure and resistance of EGFR inhibitor treatment. Therein, we proposed a hypothesis that induced STAT3-mediated resistance to EGFR inhibition therapy could be addressed by a dual inhibition of EGFR and STAT3 method. To this end, we tried to discover new thieno[2,3-d]pyrimidine derivatives "5a-o". Results from the screening on A549 and MCF7 cancer cell lines revealed that compounds 5j and 5k showed two-digit nanomolar with appropriate safety towards the WI-38 cell line. The best molecules, 5j and 5k, were subjected to γ-radiation, and their cytotoxic efficacy didn't change after irradiation, demonstrating that not having to use it avoided its side effects. Compounds 5j and 5k demonstrated the highest inhibition when their potency was tested as dual inhibitors on EGFR 67 and 41 nM, respectively, and STAT3 5.52 and 3.34 nM, respectively, proved with in silico molecular docking and dynamic simulation. In light of the results presented above, the capacity of both powerful compounds to alter the cell cycle and initiate the apoptotic process in breast cancer MCF7 cells was investigated. Caspase-8, Bcl-2, Bax and Caspase-9 apoptotic indicators were studied.