Discovery of estrogen receptor α targeting caged hypoxia-responsive PROTACs with an inherent bicyclic skeleton for breast cancer treatment.

In view of the potential off-target effects of antitumor drugs, including proteolysis targeting chimera (PROTAC), certain toxic effects may be caused in normal tissues. Herein, based on the characteristics of the tumor microenvironment, we reported the first estrogen receptor α (ERα) targeting hypoxia-responsive PROTACs in order to improve their safety in breast cancer treatment by introducing two hypoxia-activated groups, nitroimidazole and nitrobenzene, into the ER ligand or E3 ligand of an active PROTAC, which has certain cytotoxicity in normal cells. Bioactivity studies showed that these hypoxia-responsive PROTACs exhibited excellent hypoxic responsiveness and ERα degradation activity under hypoxic conditions, and thus improved the toxic effects of the active PROTAC in normal cells. It is expected that our caged compounds provide a new strategy for precise functional control of PROTAC drugs for breast cancer treatment.

Development of Highly Efficient Estrogen Receptor ß-Targeted Near-Infrared Fluorescence Probes Triggered by Endogenous Hydrogen Peroxide for Diagnostic Imaging of Prostate Cancer.

Hydrogen peroxide is one of the most important reactive oxygen species, which plays a vital role in many physiological and pathological processes. A dramatic increase in H2O2 levels is a prominent feature of cancer. Therefore, rapid and sensitive detection of H2O2 in vivo is quite conducive to an early cancer diagnosis. On the other hand, the therapeutic potential of estrogen receptor beta (ERß) has been implicated in many diseases including prostate cancer, and this target has attracted intensive attention recently. In this work, we report the development of the first H2O2-triggered ERß-targeted near-infrared fluorescence (NIR) probe and its application in imaging of prostate cancer both in vitro and in vivo. The probe showed good ERß selective binding affinity, excellent H2O2 responsiveness and near infrared imaging potential. Moreover, in vivo and ex vivo imaging studies indicated that the probe could selectively bind to DU-145 prostate cancer cells and rapidly visualizes H2O2 in DU-145 xenograft tumors. Mechanistic studies such as high-resolution mass spectrometry (HRMS) and density functional theory (DFT) calculations indicated that the borate ester group is vital for the H2O2 response turn-on fluorescence of the probe. Therefore, this probe might be a promising imaging tool for monitoring the H2O2 levels and early diagnosis studies in prostate cancer research.

Discovery of aminothiazole derivatives as novel human enterovirus A71 capsid protein inhibitors.

Enterovirus A71 (EV-A71), one of the major pathogens that causes hand, foot and mouth disease (HFMD), has seriously threatened the health and safety of young children. In this study, aminothiazole derivatives were synthesized and screened against EV-A71 in Rhabdomyosarcoma (RD) cells. The best compound (12s), with a biphenyl group, showed activity against EV-A71 (EC50: 0.27 µM) but also against a series of different human enteroviruses without significant cytotoxicity (CC50 > 56.2 µM). Mechanistic studies including time-of-drug-addition assays, viral entry assays and microscale thermophoresis (MST) experiments, showed that 12s binds to EV-A71 capsid and blocks the binding between the viral protein VP1 and the relevant human scavenger receptor class B member 2 (hSCARB2).

Establishment of evaluation criteria for the development of high quality ERα-targeted fluorescent probes.

ERα-targeted fluorescent probes are important tools for ERα study. In order to develop high quality ERα-targeted probes, a sound and complete evaluation system is essential but has not been established yet. Herein, we set up a series of evaluation criteria for ERα-targeted fluorescent probes including ERα binding affinity, fluorescence quantum yield, cytotoxicity, ERα tracking capacity, ERα selectivity and ERα labeling ability. To verify the practicability of the evaluation criteria, we designed and synthesized two ERα-targeted fluorescent probes and fully characterized their properties based on the proposed evaluation criteria. It showed that the probes exhibited better performance. Moreover, we applied the probes in MCF-7 cells to study the ERα motion characteristics for the first time. We hope that our evaluation criteria could be helpful for the establishment of a complete evaluation system for ERα-targeted fluorescent probes.

One-step pathway to selenoisobenzofuran-1(3H)-imine derivatives through highly selective selenocyclization of olefinic amides with benzeneselenyl chloride.

A 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyzed selenocyclization of olefinic amides was achieved under mild reaction conditions. The reaction formed various benzeneselenyl substituted isobenzofuran-1(3H)-imine derivatives in good yields. The product was determined using single-crystal X-ray analysis. For compound 2u, the relative stereochemistry was established on the basis of NOESY NMR studies.

Enantioselective synthesis of novel pyrano[3,2-c]chromene derivatives as AChE inhibitors via an organocatalytic domino reaction.

A series of optically active pyrano[3,2-c]chromenes have been synthesized through an asymmetric domino reaction of 4-hydroxy-2H-chromen-2-ones with malononitriles. The targeted molecules were obtained in excellent yields and enantioselectivities (up to 94% yield, 99% ee). The AChE inhibitory activity studies revealed that compounds 4n (IC50 = 21.3 µM) and 4p (IC50 = 19.2 µM) displayed potent acetylcholinesterase inhibition. In most cases, the S-enantiomers were superior to the corresponding R-enantiomers. Moreover, molecular modelling provides a practical method for understanding the enantioselective discrimination of AChE with these kinds of compounds.

Predictive features of ligand-specific signaling through the estrogen receptor.

Some estrogen receptor-α (ERα)-targeted breast cancer therapies such as tamoxifen have tissue-selective or cell-specific activities, while others have similar activities in different cell types. To identify biophysical determinants of cell-specific signaling and breast cancer cell proliferation, we synthesized 241 ERα ligands based on 19 chemical scaffolds, and compared ligand response using quantitative bioassays for canonical ERα activities and X-ray crystallography. Ligands that regulate the dynamics and stability of the coactivator-binding site in the C-terminal ligand-binding domain, called activation function-2 (AF-2), showed similar activity profiles in different cell types. Such ligands induced breast cancer cell proliferation in a manner that was predicted by the canonical recruitment of the coactivators NCOA1/2/3 and induction of the GREB1 proliferative gene. For some ligand series, a single inter-atomic distance in the ligand-binding domain predicted their proliferative effects. In contrast, the N-terminal coactivator-binding site, activation function-1 (AF-1), determined cell-specific signaling induced by ligands that used alternate mechanisms to control cell proliferation. Thus, incorporating systems structural analyses with quantitative chemical biology reveals how ligands can achieve distinct allosteric signaling outcomes through ERα.

Dual functional small molecule fluorescent probes for image-guided estrogen receptor-specific targeting coupled potent antiproliferative potency for breast cancer therapy.

A strategy by integrating biological imaging into early stages of the drug discovery process can improve our understanding of drug activity during preclinical and clinical study. In this article, we designed and synthesized coumarin-based nonsteroidal type fluorescence ligands for drug-target binding imaging. Among these synthesized compounds, 3e, 3f and 3h showed potent ER binding affinity and 3e (IC50=0.012µM) exhibited excellent ERα antagonistic activity, its antiproliferative potency in breast cancer MCF-7 cells is equipotent to the approved drug tamoxifen. The fluorescence of compounds 3e and 3f depended on the solvent properties and showed significant changes when mixed with ERα or ERß in vitro. Furthermore, target molecule 3e could cross the cell membrane, localize and image drug-target interaction in real time without cell washing. Thus, the coumarin-based platform represents a promising new ER-targeted delivery vehicle with potential imaging and therapeutic properties.

Applications of Chiral Squaramides: From Asymmetric Organocatalysis to Biologically Active Compounds.

This review seeks to provide coverage on the recent advances in chiral squaramide-catalyzed asymmetric transformations and their applications in the synthesis of a variety of chiral biologically active compounds. It aims to give an overview highlighting the new reaction types and enantioenriched medicinal scaffolds developed in the last few years.

Synthesis and structure-activity relationships of novel hybrid ferrocenyl compounds based on a bicyclic core skeleton for breast cancer therapy.

Breast cancer is the most frequent cancer in women worldwide, and incidence is increasing year by year. Although current selective estrogen receptor modulators (SERMs) have clear advantages in the treatment of hormone-responsive breast cancer, they are ineffective for ER(-). In this study, we describe the design and synthesis of a series of dual-acting estrogen receptor (ER) and histone deacetylase (HDAC) inhibitors with incorporation of the ferrocenyl moiety, leading to novel hybrid ferrocenyl complexes (FcOBHS-HDACis) for breast cancer therapy. It is worth to note that these ferrocenyl conjugates could not only potently inhibit HDACs and the proliferation of ERα positive (ER(+)) breast cancer cells (MCF-7), but also show significant antiproliferative effect on ER(-) breast cancer cells (MDA-MB-231). Thus, the FcOBHS-HDACi conjugates represent a novel approach to the development of efficiently dual-acting agents for treatment of breast cancer.

Synthesis and SARs of indole-based α-amino acids as potent HIV-1 non-nucleoside reverse transcriptase inhibitors.

A series of non-nucleoside reverse transcriptase inhibitors derived from indole-based α-amino acids were designed and synthesized. Their inhibitory activities were detected by a TZM-bl cell assay on HIV virus type HIV-1IIIB. The comprehensive understanding of the SAR was obtained by utilizing the variation of the substituents of the indole-based α-amino acids. From the screened compounds, the novel inhibitors 19 and 29 were identified to be highly potent candidates with EC50 values of 0.060 µM and 0.045 µM respectively (CC50 values of 109.545 µM and 49.295 µM and SI values of 1825.8 and 1095.4). In most cases, the variation of substituents at different positions had a significant effect on the potency of activities. The results also indicate that the indole-based α-amino acids as efficient NNRTIs displayed comparable anti-HIV-1 activities to the reference drug NVP. We hope the identification of these indole-based amino acids as efficient NNRTIs of RT could stimulate researchers to develop more diversified anti-HIV drugs.

Novel estrogen receptor ß/histone deacetylase dual-targeted near-infrared fluorescent probes as theranostic agents for imaging and treatment of prostate cancer.

Estrogen receptor (ER) ß and histone deacetylases (HDACs), when overexpressed, are associated closely with the occurrence and development of prostate cancer and are, therefore, considered important targets and biomarkers used in the clinical treatment of prostate cancer. The present study involved the design and synthesis of the first ERß and HDAC dual-target near-infrared fluorescent probe with both imaging capacity and antitumor activity for prostate cancer. Both P1 and P2 probes exhibited excellent ERß selectivity, with P1 being almost exclusively selective for ERß compared to ERα. In addition, P1 exhibited good optical properties, such as strong near-infrared emission, large Stokes shift, and better anti-interference ability, along with excellent imaging ability for living cells. P1 also exhibited potent inhibitory activity against HDAC6 and DU-145 cells, with IC50 values of 52 nM and 0.96 µM, respectively. Further, P1 was applied successfully for the in vivo imaging of prostate cancer in a mouse model, and significant in vivo antitumor efficacy was achieved. The developed dual-target NIR fluorescent probe is expected to serve as an effective tool in the research on prostate cancer, leading to novel insights for the theranostic study of diseases related to ERß and HDACs.

Fluorescence theranostic PROTACs for real-time visualization of ERα degradation.

Proteolysis targeting chimera (PROTAC) technology, a groundbreaking strategy for degradation of pathogenic proteins by hijacking of the ubiquitin-proteasome-system has become a promising strategy in drug design. However, the real-time monitoring and visualization of protein degradation processes have been long-standing challenges in the realm of drug development. In this research, we sought to amalgamate the highly efficient protein-degrading capabilities of PROTAC technology with the visualization attributes of fluorescent probes, with the potential to pave the path for the design and development of a novel class of visual PROTACs. These novel PROTACs uniquely possess both fluorescence imaging and therapeutic characteristics, all with the goal of enabling real-time observations of protein degradation processes. Our approach involved the utilization of a high ER-targeting fluorescent probe, previously reported in our laboratory, which served as a warhead that specifically binds to the protein of interest (POI). Additionally, a VHL ligand for recruiting E3 ligase and linkers of various lengths were incorporated to synthesize a series of novel ER-inherent fluorescence PROTACs. Among them, compound A3 demonstrated remarkable efficiency in degrading ERα proteins (DC50 = 0.12 µM) and displaying exceptional anti-proliferative activity against MCF-7 cells (IC50 = 0.051 µM). Furthermore, it exhibited impressive fluorescence imaging performance, boasting an emission wavelength of up to 582 nm, a Stokes shift of 116 nm, and consistent optical properties. These attributes make it especially suitable for the real-time, in situ tracking of ERα protein degradation processes, thus may serve as a privileged visual theranostic PROTAC for ERα+ breast cancer. This study not only broadens the application spectrum of PROTAC technology but also introduces a novel approach for real-time visualization of protein degradation processes, ultimately enhancing the diagnostic and treatment efficacy of PROTACs.

Novel Hsp90-Targeting PROTACs: Enhanced synergy with cisplatin in combination therapy of cervical cancer.

The development of effective drugs for cervical cancer is urgently required because of its high mortality rate and the limited treatment options. Herein, we report the design, synthesis, and evaluation of a series of novel and effective Hsp90-targeting PROTACs. These compounds exhibited potent anti-proliferative activity against cervical cancer cells with low IC50 values. Compound lw13 effectively degraded Hsp90 at a concentration of only 0.05 µM. In addition, it can inhibit the metastasis of cancer cells and induce significant cell cycle arrest and apoptosis. Furthermore, lw13 demonstrated remarkable antitumor activity both in vitro and in vivo, and has a synergistic effect in combination with cisplatin. Moreover, lw13 can prevent the activation of the HER2/AKT/mTOR signaling pathway by indirectly reducing the levels of HER2 and AKT. This study paves the way for cancer treatment and provides valuable insights into the combination therapy of cervical cancer.

Discovery of Novel ERα and Aromatase Dual-Targeting PROTAC Degraders to Overcome Endocrine-Resistant Breast Cancer.

Estrogen receptor α (ERα) plays a pivotal role in the proliferation, differentiation, and migration of breast cancer (BC) cells, and aromatase (ARO) is a crucial enzyme in estrogen synthesis. Hence, it is necessary to inhibit estrogen production or the activity of ERα for the treatment of estrogen receptor-positive (ER+) BC. Herein, we present a new category of dual-targeting PROTAC degraders designed to specifically target ERα and ARO. Among them, compound 18c bifunctionally degrades and inhibits ERα/ARO, thus effectively suppressing the proliferation of MCF-7 cells while showing negligible cytotoxicity to normal cells. In vivo, 18c promotes the degradation of ERα and ARO and inhibits the growth of MCF-7 xenograft tumors. Finally, compound 18c demonstrates promising antiproliferative and ERα degradation activity against the ERαMUT cells. These findings suggest that 18c, being the inaugural dual-targeting degrader for ERα and ARO, warrants further advancement for the management of BC and the surmounting of endocrine resistance.

Novel Acyl Thiourea-Based Hydrophobic Tagging Degraders Exert Potent Anti-Influenza Activity through Two Distinct Endonuclease Polymerase Acidic-Targeted Degradation Pathways.

The spread of the influenza virus has caused devastating pandemics and huge economic losses worldwide. Antiviral drugs with diverse action modes are urgently required to overcome the challenges of viral mutation and drug resistance, and targeted protein degradation strategies constitute excellent candidates for this purpose. Herein, the first degradation of the influenza virus polymerase acidic (PA) protein using small-molecule degraders developed by hydrophobic tagging (HyT) technology to effectively combat the influenza virus was reported. The SAR results revealed that compound 19b with Boc2-(L)-Lys demonstrated excellent inhibitory activity against A/WSN/33/H1N1 (EC50 = 0.015 µM) and amantadine-resistant strain (A/PR/8/H1N1), low cytotoxicity, high selectivity, substantial degradation ability, and good drug-like properties. Mechanistic studies demonstrated that the proteasome system and autophagic lysosome pathway were the potential drivers of these HyT degraders. Thus, this study provides a powerful tool for investigating the targeted degradation of influenza virus proteins and for antiviral drug development.

Anticancer or carcinogenic? The role of estrogen receptor ß in breast cancer progression.

Estrogen receptor ß (ERß) is closely related to breast cancer (BC) progression. Traditional concepts regard ERß as a tumor suppressor. As studies show the carcinogenic effect of ERß, some people have come to a new conclusion that ERß serves as a tumor suppressor in estrogen receptor α (ERα)-positive breast cancer, while it is a carcinogen in ERα-negative breast cancer. However, we re-examine the role of ERß and find this conclusion to be misleading based on the last decade's research. A large number of studies have shown that ERß plays an anticancer role in both ERα-positive and ERα-negative breast cancers, and its carcinogenicity does not depend solely on the presence of ERα. Herein, we review the anticancer and oncogenic effects of ERß on breast cancer progression in the past ten years, discuss the mechanism respectively, analyze the main reasons for the inconsistency and update ERß selective ligand library. We believe a detailed and continuously updated review will help correct the one-sided understanding of ERß, promoting ERß-targeted breast cancer therapy.

Antiviral PROTACs: Opportunity borne with challenge.

Proteolysis targeting chimera (PROTAC) degradation of pathogenic proteins by hijacking of the ubiquitin-proteasome-system has become a promising strategy in drug design. The overwhelming advantages of PROTAC technology have ensured a rapid and wide usage, and multiple PROTACs have entered clinical trials. Several antiviral PROTACs have been developed with promising bioactivities against various pathogenic viruses. However, the number of reported antiviral PROTACs is far less than that of other diseases, e.g., cancers, immune disorders, and neurodegenerative diseases, possibly because of the common deficiencies of PROTAC technology (e.g., limited available ligands and poor membrane permeability) plus the complex mechanism involved and the high tendency of viral mutation during transmission and replication, which may challenge the successful development of effective antiviral PROTACs. This review highlights the important advances in this rapidly growing field and critical limitations encountered in developing antiviral PROTACs by analyzing the current status and representative examples of antiviral PROTACs and other PROTAC-like antiviral agents. We also summarize and analyze the general principles and strategies for antiviral PROTAC design and optimization with the intent of indicating the potential strategic directions for future progress.

Rational design and optimization of acylthioureas as novel potent influenza virus non-nucleoside polymerase inhibitors.

Evidence suggests that rapidly evolving virus subvariants risk rendering current vaccines and anti-influenza drugs ineffective. Hence, exploring novel scaffolds or new targets of anti-influenza drugs is of great urgency. Herein, we report the discovery of a series of acylthiourea derivatives produced via a scaffold-hopping strategy as potent antiviral agents against influenza A and B subtypes. The most effective compound 10m displayed subnanomolar activity against H1N1 proliferation (EC50 = 0.8 nM) and exhibited inhibitory activity toward other influenza strains, including influenza B virus and H1N1 variant (H1N1, H274Y). Additionally, druggability evaluation revealed that 10m exhibited favorable pharmacokinetic properties and was metabolically stable in liver microsome preparations from three different species as well as in human plasma. In vitro and in vivo toxicity studies confirmed that 10m demonstrated a high safety profile. Furthermore, 10m exhibited satisfactory antiviral activity in a lethal influenza virus mouse model. Moreover, mechanistic studies indicated that these acylthiourea derivatives inhibited influenza virus proliferation by targeting influenza virus RNA-dependent RNA polymerase. Thus, 10m is a potential lead compound for the further exploration of treatment options for influenza.

Identification of Novel Dual-Target Estrogen Receptor α Degraders with Tubulin Inhibitory Activity for the Treatment of Endocrine-Resistant Breast Cancer.

Endocrine resistance remains a significant problem in the clinical treatment of estrogen receptor α-positive (ERα+) breast cancer (BC). In this study, we developed a series of novel dual-functional ERα degraders based on a bridged bicyclic scaffold with selenocyano (SeCN) side chains. These compounds displayed potent ERα degradation and tubulin depolymerization activity. Among them, compounds 35s and 35t exhibited the most promising antiproliferative and ERα degradation activity in multiple ERα+ BC cell lines bearing either wild-type or mutant ERα. Meanwhile, compounds 35s and 35t disrupted the microtubule network by restraining tubulin polymerization, evidenced by 35t inducing cell cycle arrest in the G2/M phase. In MCF-7 and LCC2 xenograft models, compounds 35s and 35t remarkably suppressed tumor growth without noticeable poisonousness. Finally, this study provided guidance for developing new dual-target antitumor drug candidates for the ERα+ BC therapy, especially for the resistant variant.