Discovery of the First Subnanomolar PPARα/δ Dual Agonist for the Treatment of Cholestatic Liver Diseases

Targeted Degradation of Bromodomain-Containing Protein 4 Enabled by Reactive Oxygen Species-Activatable NanoPROTACs as an Efficient Strategy to Reverse Liver Fibrosis in Chronic Liver Injury

Liver fibrosis is an inadequate response to tissue stress, with reactive oxygen species (ROS) overproduction in activated hepatic stellate cells (aHSCs). Bromodomain-containing protein 4 (BRD4) was found to be upregulated in aHSCs and has been identified as an effective target for the treatment of liver fibrosis. However, inhibition of BRD4 with traditional kinase inhibitors achieved only limited success because of its low therapeutic efficiency. Furthermore, the exact mechanism by which BRD4 regulates liver fibrosis remains unclear and needs to be elucidated. In this work, we proposed an efficiency strategy, i.e., targeted degradation of BRD4 by ROS-activatable NanoPROTACs, for the treatment of liver fibrosis, both in vitro and in vivo. More importantly, we clarified the mechanism by which BRD4 regulates liver fibrosis. Thus, this strategy may represent an alternative to previously reported strategies and may be extensively applied to the design of ROS-activatable proteolysis-targeting chimeras for the treatment of other organ fibrosis.

Design, synthesis, and biological evaluation of imidazolidinone derivatives as potent PPARα/δ agonists for the treatment of cholestatic liver diseases

Cholestatic liver disease (CLD) represents a significant and growing public health concern, and there is a lack of effective therapeutic drug in clinical practice. Peroxisome proliferator-activator receptors α/δ (PPARα/δ) are regarded as potential therapeutic targets for CLD. In this study, a series of novel imidazolidinone PPARα/δ agonists were developed, and the preferred compound 8 displayed potent and well-balanced agonistic activity. Compound 8 showed high selectivity over other related nuclear receptors and effectively regulated the PPARα/δ target genes expression in mice. Notably, compound 8 demonstrated good pharmacokinetic profiles and potent in vivo anti-CLD effects. Collectively, compound 8 holds promise for developing an anti-CLD agent.

Recent advances in small molecule design strategies against hepatic fibrosis

Hepatic fibrosis, a widespread pathological process observed across various liver diseases, is acknowledged as a potentially reversible condition. In recent years, liver fibrosis has garnered extensive research attention, with a primary emphasis on developing drugs that can directly block or reverse this condition. This paper presents a comprehensive review of the design strategies for various anti-hepatic fibrosis agents that have been many efficacious small-molecule drugs. This review encompasses the synthesis and design of nuclear receptor ligands (such as VDR and Nurr7), kinase inhibitors (including ALK5 and JAK1), selective PDE inhibitors, small-molecule monomers derived from natural products, and other small molecules. The aim of this review is to provide promising avenues and valuable insights for the continued development of anti-hepatic fibrosis drugs.

Drugs targeting peroxisome proliferator-activated receptors

The year 2024 witnessed the accelerated approvals of two peroxisome proliferator-activated receptor (PPAR) agonists for the treatment of primary biliary cholangitis (PBC). PPARs, including three isoforms (PPARα, PPARγ, and PPARδ), are therapeutic targets generating considerable debate yet also seeing significant advances in their successful targeting. Currently, selective PPAR agonists are used to manage hyperlipidemia, type 2 diabetes mellitus (T2DM), and PBC, and dual/pan-PPAR agonists have been developed to address various disorders. In this review, we summarize the PPAR agonists approved globally, and their pros and cons as therapeutic agents for various diseases, with a particular focus on those agonists marketed since 2010.

Bone mesenchymal stem cells improve cholestatic liver fibrosis by targeting ULK1 to regulate autophagy through PI3K/AKT/mTOR pathway

Cholestatic liver disease (CLD) is a severe disease, which can progress to liver cirrhosis, even liver cancer. Hepatic stellate cells (HSCs) activation plays a crucial role in CLD development. Bone mesenchymal stem cells (BMSCs) treatment was demonstrated to be beneficial in liver diseases. However, the therapeutic effect and mechanism of BMSCs on CLD are poorly known. In the present study, we investigated the therapeutic effects and underlying mechanisms of BMSCs transplantation in mouse models of bile duct ligation-induced cholestatic liver fibrosis (CLF). The results revealed that BMSCs significantly improved liver function and reduced the formation of fibrosis after portal vein transplantation. Mechanistically, after coculturing BMSCs and HSCs, we identified that BMSCs alleviated starvation-induced HSCs activation. Further, BMSCs inhibited HSCs activation by decreasing autophagy, and PI3K/AKT/mTOR pathway was involved in the regulation. More importantly, ULK1 is identified as the main autophagy-related gene regulated by BMSCs in HSCs autophagy. Overexpression of ULK1 reversed the suppression of HSCs autophagy by BMSCs. Collectively, our results provide a theoretical basis for BMSCs targeting ULK1 to attenuate HSCs autophagy and activation and suggest that BMSCs or ULK1 may be an alternative therapeutic approach/target for the treatment of CLF.

PPARβ/δ as a promising molecular drug target for liver diseases: A focused review

Various liver diseases pose great threats to humans. Although the etiologies of these liver diseases are quite diverse, they share similar pathologic phenotypes and molecular mechanisms such as oxidative stress, lipid and glucose metabolism disturbance, hepatic Kupffer cell (KC) proinflammatory polarization and inflammation, insulin resistance, and hepatic stellate cell (HSC) activation and proliferation. Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) is expressed in various types of liver cells with relatively higher expression in KCs and HSCs. Accumulating evidence has revealed the versatile functions of PPARβ/δ such as controlling lipid homeostasis, inhibiting inflammation, regulating glucose metabolism, and restoring insulin sensitivity, suggesting that PPARβ/δ may serve as a potential molecular drug target for various liver diseases. This article aims to provide a concise review of the structure, expression pattern and biological functions of PPARβ/δ in the liver and its roles in various liver diseases, and to discuss potential future research perspectives.

Design, synthesis, and biological evaluation of piperazine derivatives as pan-PPARs agonists for the treatment of liver fibrosis

Liver fibrosis is commonly occurred in chronic liver diseases, but there is no approved drug for clinical use. The nuclear receptor peroxisome proliferator-activated receptors (PPARs) could not only regulate metabolic homeostasis but also possess anti-inflammatory and antifibrotic effects, and pan-PPARs agonist was considered as a potential anti-liver fibrosis agent. In this study, a series of novel piperazine pan-PPARs agonists were developed, and the preferred compound 12 displayed potent and well-balanced pan-PPARs agonistic activity. Moreover, compound 12 could dose-dependently stimulate the PPARs target genes expression and showed high selectivity over other related nuclear receptors. Importantly, compound 12 exhibited excellent pharmacokinetic profiles and good anti-liver fibrosis effects in vivo. Collectively, compound 12 holds promise for developing an anti-liver fibrosis agent.

A Tunable Cascade Reaction of Ureidomalonates and Alkenyl Azlactones for the Divergent Synthesis of Hydantoins with Distinct Functional Groups

A tunable cascade reaction of ureidomalonates and alkenyl azlactones was disclosed, which gave rise to the construction of N-aroyl α-amino acid ester and imide-functionalized hydantoins in moderate to good yields and with excellent diastereoselectivities. The reaction pathway was precisely manipulated by organocatalysis and phase-transfer/sunlight relay catalysis, respectively, to realize the divergent synthesis. The successful gram-scale preparation of representative products exhibited the application potential of this protocol. Mechanistic studies indicated that the exchange and phase transfer of ethoxy anion played a key role in altering the reaction pathway, and sunlight might accelerate the oxidation process at the late stage of the reaction triggered by phase-transfer catalysis.

Organophosphorus-Catalyzed Direct Dehydroxylative Thioetherification of Alcohols with Hypervalent Organosulfur Compounds

A metal-free and thiol-free organophosphorus-catalyzed method for forming thioethers was disclosed, driven by PIII/PV═O redox cycling. In this work, one-step dehydroxylative thioetherification of alcohols was fulfilled with various hypervalent organosulfur compounds. This established strategy features an excellent functional group tolerance and broad substrate scope, especially inactivated alcohols. The scale-up reaction and further transformation of the product were also successful. Additionally, this method offers a protecting-group-free and step-efficient approach for synthesizing peroxisome proliferator-activated receptor agonists which exhibited promising potential for treating osteoporosis in mammals.

Peroxisome Proliferator-Activated Receptor agonists and antagonists: an updated patent review (2020-2023)

INTRODUCTION

The search for novel compounds targeting Peroxisome Proliferator-Activated Receptors (PPARs) is currently ongoing, starting from the previous successfully identification of selective, dual or pan agonists. In last years, researchers' efforts are mainly paid to the discovery of PPARγ and δ modulators, both agonists and antagonists, selective or with a dual-multitarget profile. Some of these compounds are currently under clinical trials for the treatment of primary biliary cirrhosis, nonalcoholic fatty liver disease, hepatic, and renal diseases.

AREAS COVERED

A critical analysis of patents deposited in the range 2020-2023 was carried out. The novel compounds discovered were classified as selective PPAR modulators, dual and multitarget PPAR agonists. The use of PPAR ligands in combination with other drugs was also discussed, together with novel therapeutic indications proposed for them.

EXPERT OPINION

From the analysis of the patent literature, the current emerging landscape sees the necessity to obtain PPAR multitarget compounds, with a balanced potency on three subtypes and the ability to modulate different targets. This multitarget action holds great promise as a novel approach to complex disorders, as metabolic, inflammatory diseases, and cancer. The utility of PPAR ligands in the immunotherapy field also opens an innovative scenario, that could deserve further applications.