Discovery of the Highly Selective and Potent STAT3 Inhibitor for Pancreatic Cancer Treatment.

Signal transducer and activator of transcription 3 (STAT3) is an attractive cancer therapeutic target. Unfortunately, targeting STAT3 with small molecules has proven to be very challenging, and for full activation of STAT3, the cooperative phosphorylation of both tyrosine 705 (Tyr705) and serine 727 (Ser727) is needed. Further, a selective inhibitor of STAT3 dual phosphorylation has not been developed. Here, we identified a low nanomolar potency and highly selective small-molecule STAT3 inhibitor that simultaneously inhibits both STAT3 Tyr705 and Ser727 phosphorylation. YY002 potently inhibited STAT3-dependent tumor cell growth in vitro and achieved potent suppression of tumor growth and metastasis in vivo. More importantly, YY002 exhibited favorable pharmacokinetics, an acceptable safety profile, and superior antitumor efficacy compared to BBI608 (STAT3 inhibitor that has advanced into phase III trials). For the mechanism, YY002 is selectively bound to the STAT3 Src Homology 2 (SH2) domain over other STAT members, which strongly suppressed STAT3 nuclear and mitochondrial functions in STAT3-dependent cells. Collectively, this study suggests the potential of small-molecule STAT3 inhibitors as possible anticancer therapeutic agents.

WB518, a novel STAT3 inhibitor, effectively alleviates IMQ and TPA-induced animal psoriasis by inhibiting STAT3 phosphorylation and Keratin 17.

OBJECTIVES: Psoriasis is a prevalent chronic inflammatory skin disease in humans that is characterized by frequent relapses and challenging to cure. WB518 is a novel small molecule compound with an undisclosed structure. Therefore, our study aimed to investigate the therapeutic potential of WB518 in vitro and in vivo for the treatment of psoriasis, specifically targeting the abnormal proliferation, aberrant differentiation of epidermal keratinocytes, and pathogenic inflammatory response. MATERIALS AND METHODS: We employed dual luciferase reporter assay to screen compounds capable of inhibiting STAT3 gene transcription. Flow cytometry was utilized to analyze CD3-positive cells. Protein and mRNA levels were assessed through Western blotting, immunofluorescence, immunohistochemistry, and real-time PCR. Cell viability was measured using the MTS assay, while in vivo models of psoriasis induced by IMQ and TPA were employed to study the anti-psoriasis effect of WB518. RESULTS: WB518 was found to significantly reduce the mRNA and protein levels of Keratin 17 (K17) in HaCaT cells by inhibiting the phosphorylation of STAT3 Tyr705 (Y705). In the IMQ and TPA-induced psoriasis mouse model, WB518 effectively improved scaling, epidermal hyperplasia, and inflammation. WB518 also suppressed the expression of inflammatory cytokines, such as interleukin (IL)-1ß, IL-6, IL-17, and IL-23. Furthermore, WB518 decreased the proportion of CD3-positive cells in the psoriatic skin of mice. CONCLUSIONS: WB518 exhibits promising potential as a treatment candidate for psoriasis.

Selectively Targeting STAT3 Using a Small Molecule Inhibitor is a Potential Therapeutic Strategy for Pancreatic Cancer.

PURPOSE: Pancreatic cancer is the worst prognosis among all human cancers, and novel effective treatments are urgently needed. Signal transducer and activator of transcription 3 (STAT3) has been demonstrated as a promising target for pancreatic cancer. Meanwhile, selectively targeted STAT3 with small molecule remains been challenging. EXPERIMENTAL DESIGN: To specifically identify STAT3 inhibitors, more than 1.3 million compounds were screened by structure-based virtual screening and confirmed with the direct binding assay. The amino acid residues that WB436B bound to were verified by induced-fit molecular docking simulation, RosettaLigand computations, and site-directed mutagenesis. On-target effects of WB436B were examined by microscale thermophoresis, surface plasmon resonance, in vitro kinase assay, RNA sequencing, and selective cell growth inhibition assessment. In vivo studies were performed in four animal models to evaluate effects of WB436B on tumor growth and metastasis. Kaplan-Meier analyses were used to assess survival. RESULTS: WB436B selectively bound to STAT3 over other STAT families protein, and in vitro antitumor activities were improved by 10 to 1,000 fold than the representative STAT3 inhibitors. WB436B selectively inhibits STAT3-Tyr705 phosphorylation, STAT3 target gene expression, and the viability of STAT3-dependent pancreatic cancer cells. WB436B significantly suppresses tumor growth and metastasis in vivo and prolongs survival of tumor-bearing mice. Mechanistic studies showed that WB436B have unique binding sites located in STAT3 Src homology 2 domain. CONCLUSIONS: Our work presents the first-in-class selective STAT3 inhibitor WB436B as a potential therapeutic candidate for the treatment of pancreatic cancer.

Discovery of a Highly Potent and Orally Bioavailable STAT3 Dual Phosphorylation Inhibitor for Pancreatic Cancer Treatment.

Increasing evidence has demonstrated that STAT3 phosphorylation at Tyr705 and Ser727 is closely associated with the progression and poor prognosis of pancreatic cancer. Herein, we report the function-based screening, SAR studies, and biological activity evaluation of a series of novel STAT3 dual phosphorylation inhibitors with an indole-containing tetra-aromatic heterocycle scaffold. Our efforts led to the discovery of optimal compound 4c among the investigated ones, showing desirable ADME properties and highly potent antitumor activities in vitro and in vivo. By targeting the STAT3 SH2 domain, 4c significantly blocked p-Tyr705 and p-Ser727 and caused the abrogation of the corresponding nuclear transcription and mitochondrial oxidative phosphorylation functions of STAT3 in the low nanomolar range. Except for nanomolar antiproliferation activities in vitro, oral treatment of 4c exhibited significant suppressive effects and tolerance in a pancreatic cancer xenograft model, indicating that 4c could be useful for pancreatic cancer treatment as a STAT3 dual phosphorylation inhibitor.

Discovery of a Novel Potent STAT3 Inhibitor HP590 with Dual p-Tyr705/Ser727 Inhibitory Activity for Gastric Cancer Treatment.

Accumulating evidence has documented that STAT3 phosphorylation at Tyr705 and Ser727 jointly promotes the initiation and progression of gastric cancer. However, most reported STAT3 inhibitors have mainly focused on suppressing STAT3 phosphorylation at Tyr705 while ignoring the tumorigenic effects of phosphorylation at Ser727. Herein, we described the design, synthesis, and structure-activity relationship studies on a series of triaromatic heterocyclic derivatives as potent dual phosphorylation STAT3 inhibitors. These efforts led to the discovery of the best compound 3h (HP590) among the investigated ones, a novel, highly potent, and orally bioavailable STAT3 inhibitor possessing lower nanomolar inhibitory activity toward p-Tyr705 and p-Ser727. Target validation revealed that HP590 selectively targets STAT3 to remarkably inhibit its canonical and noncanonical activation and corresponding biological functions, thereby resulting in the growth inhibition of gastric cancer in vitro and in vivo, highlighting the therapeutic potential of dual phosphorylation STAT3 inhibitors for gastric cancer.

A novel small-molecule activator of unfolded protein response suppresses castration-resistant prostate cancer growth.

Androgen receptor-targeted therapy improves survival in castration-resistant prostate cancer (CRPC). However, almost all patients with CRPC eventually develop secondary resistance to these drugs. Therefore, alternative therapeutic approaches for incurable metastatic CRPC are urgently needed. Unfolded protein response (UPR) is regarded as a cytoprotective mechanism that removes misfolded proteins in rapidly proliferating tumor cells. However, acute activation of the UPR directly leads to tumor cell death. This study has shown that WJ-644A, a novel small molecule activator of UPR, potently inhibited the proliferation of prostate cancer cells and caused tumor regression with a good safety profile in multiple animal models. Mechanistically, we have identified that WJ-644A induced cell methuosis and autophagy upon UPR activation. Our study not only identifies the UPR as an actionable target for CRPC treatment, but also establishes WJ-644A as a novel UPR activator that has potential therapeutic value for CRPC.

Targeting STAT3 by a small molecule suppresses pancreatic cancer progression.

Pancreatic cancer is lethal in over 90% of cases since it is resistant to current therapeutic strategies. The key role of STAT3 in promoting pancreatic cancer progression has been proven, but effective interventions that suppress STAT3 activities are limited. The development of novel anticancer agents that directly target STAT3 may have potential clinical benefits for pancreatic cancer treatment. Here, we report a new small-molecule inhibitor (N4) with potent antitumor bioactivity, which inhibits multiple oncogenic processes in pancreatic cancer. N4 blocked STAT3 and phospho-tyrosine (pTyr) peptide interactions in fluorescence polarization (FP) assay, specifically abolished phosphor-STAT3 (Tyr705), and suppressed expression of STAT3 downstream genes. The mechanism involved the direct binding of N4 to the STAT3 SH2 domain, thereby, the STAT3 dimerization, STAT3-EGFR, and STAT3-NF-κB cross-talk were efficiently inhibited. In animal models of pancreatic cancer, N4 was well tolerated, suppressed tumor growth and metastasis, and significantly prolonged survival of tumor-bearing mice. Our results offer a preclinical proof of concept for N4 as a candidate therapeutic compound for pancreatic cancer.

Determining the Drug-Like Properties of Ailanthone, a Novel Chinese Medicine Monomer with Anti-CRPC Activity.

Approximately 40% of compounds with therapeutic potential cannot be successfully developed into drugs owing to their poor pharmaceutical properties, emphasising the need to profile their drug-like properties as early as possible during preclinical development. This study aimed to evaluate the drug-like properties of ailanthone, a novel Chinese medicine monomer that was shown to have activity against castration-resistant prostate cancer tumour growth and metastasis in our previous study. The drug-like properties detected in the present study included effects on permeability, liver microsome stability, plasma protein binding rate, plasma stability, and human ether-à-go-go-related gene inhibition. Additionally, the following results were obtained: the efflux ratio of ailanthone was > 32 during permeability detection; the half-life and intrinsic clearance (Clint) in mouse, rat, and human liver microsomes were > 145 min and < 9.6 µL/min/mg protein, respectively. The Clint(liver) of ailanthone was < 38.0, < 17.3, and < 8.6 mL/min/kg body weight in mice, rats, and humans, respectively. The plasma protein binding percentage of ailanthone was 16.6 ± 4.2% in human plasma, with 62.5% remaining at 120 min after incubation. The IC50 value of ailanthone for the human ether-à-go-go-related gene channels was > 30 µM. Collectively, these results and those from our previous study indicate that the pharmacokinetic properties of ailanthone are suitable for the potential development of this compound as an oral or intravenous drug for the treatment of castration-resistant prostate cancer.

Synthesis and anticancer activity of novel 9,13-disubstituted berberine derivatives.

Novel berberine derivatives with disubstituents on positions C9 and C13 were synthesized and evaluated for antiproliferative activities against human prostate cancer cell lines (PC3 and DU145), breast cancer cell line (MDA-MB-231) and human colon cancer cell lines (HT29 and HCT116). All compounds showed significantly enhanced antiproliferative activities compared with berberine. Notably, compound 18e exhibited the strongest cytotoxicity against PC3 cells with an IC50 value of 0.19 µM, and the highest selectivity index (SIPC3 > 20). Further studies showed that 18e could arrest the cell cycle at G1 phase, and significantly inhibit tumor cell colony forming and migration even at low concentrations. Interestingly, 18e could significantly induce cytoplasmic vacuolation, suggesting a different mode of action from berberine.