Developments of CRBN-based PROTACs as potential therapeutic agents

Design and synthetic approaches to thalidomide based small molecule degraders

Thalidomide has been used as a repurposed drug for treating multiple myeloma since 1997. Several novel anticancer drugs containing thalidomide active moiety has been discovered since then. Many thalidomide drug candidates with tuned linker size have been instrumental in inhibiting histone deacetylase, kinase, transcription factors etc. and facilitate selective degradation of E3 ligase and other enzymes. Here we are focused on small molecule degraders that are being tailored with tweaking synthetic architectures around thalidomide chemical motif towards the development of promising drug candidates. Interesting biomedical applications of thalidomide-based degraders with recent developments including pharmacokinetic profiles, protein stability, activity studies, degradation assays, and antitumor response are elucidated.

Proteolysis targeting chimera, molecular glue degrader and hydrophobic tag tethering degrader for targeted protein degradation: Mechanisms, strategies and application

Targeted protein degradation (TPD) represents a revolutionary approach to drug discovery, offering a novel mechanism that outperforms traditional inhibitors. This approach employs small molecule drugs to induce the ubiquitination and subsequent degradation of target protein via the proteasome or lysosomal pathways. Key strategies within TPD include proteolysis targeting chimeras (PROTACs), hydrophobic tag tethering degraders (HyTTDs), and molecular glue degraders (MGDs). PROTACs have been undergone clinical evaluations, MGDs have been used in the clinic, and HyTTDs have shown significant progress in cancer treatment. Each of these strategies presents unique advantages and approaches to target protein degradation. This review summarizes five years of research on PROTACs, HyTTDs, and MGDs, highlighting their design principles, advantages, limitations, and future challenges to provide clear guidance and in-depth insights for advancing drug development.

Membrane-Bounded Intracellular E3 Ubiquitin Ligase-Targeting Chimeras (MembTACs) for Targeted Membrane Protein Degradation

Targeted protein degradation (TPD) represents a potent therapeutic strategy aimed at dismantling disease-associated target proteins. PROTAC is the most widely developed technique for intracellular protein degradation, while its degradation ability on membrane proteins has been hindered by the need for complex synthetic processes and limited permeability. In this study, we developed the membrane-bounded intracellular E3 ubiquitin ligase-targeting chimeras (MembTACs) that simultaneously recruit intracellular E3 ubiquitin ligase and bind to the desired membrane proteins for targeted degradation of membrane proteins. We demonstrate that the MembTACs can effectively utilize intracellular E3 ubiquitin ligase to degrade the therapeutically relevant membrane proteins of EpCAM and Met via the proteasome pathway. We anticipate that the new platform will expand the range of PROTAC applications and provide a new dimension for targeted membrane protein degradation.

Reductive C(sp2)-C(sp3) Coupling Protocol to Enable Linker Exploration of Cereblon E3-Ligase BRD4 Proteolysis-Targeting Chimeras

Heterobifunctional degraders (also known as proteolysis-targeting chimeras or PROTACs) have emerged in drug discovery as an alternative therapeutic modality for targeting disease-causing proteins that are challenging to modulate with standard protein inhibitors. Almost all current PROTACs under clinical studies use the E3 ligase cereblon (CRBN) to hijack the ubiquitin-proteasome system. In this study, we used high-throughput experimentation to identify new conditions to access carbon-carbon bonds on our CRBN warheads. These efforts led to the discovery that alkyl-connected CRBN binders demonstrate improved cell permeability and reduced neosubstrate activity when compared with their amide counterparts. To further demonstrate the value of this protocol and the resulting alkyl connection point, these conditions were utilized as a final synthetic step to produce a heterobifunctional BRD4 degrader with an improved CRBN neosubstrate selectivity profile compared to its amide counterpart.

ByeTAC: Bypassing E-Ligase-Targeting Chimeras for Direct Proteasome Degradation

The development of targeted protein degradation by recruiting a protein of interest to a ubiquitin ligase to facilitate its degradation has become a powerful therapeutic tool. The potential of this approach is limited to proteins that can be readily ubiquitinated and relies on having a ligand with the various E3 ligases. Here, we describe a new methodology for targeted protein degradation that directly recruits a protein of interest to the proteasome for degradation. We generated bifunctional molecules that incorporate a small molecule ligand into a subunit on the 26S proteasome that recruits the protein directly for degradation. ByeTAC degradation requires binding to Rpn-13, a nonessential ubiquitin receptor of the 26S proteasome, and the protein of interest and does not have to rely on the E ligase cascade for ubiquitination. The ByeTAC methodology demonstrates the application of directly recruiting a protein to the proteasome via interactions with Rpn-13 for degradation.

Advancing target validation with PROTAC technology

INTRODUCTION

Targeted protein degradation (TPD) is a cutting-edge technology that provides new avenues for drug discovery and development. PROteolysis TArgeting Chimeras (PROTACs) are the most established and advanced TPD strategy, enabling the selective degradation of disease-associated and 'undruggable' proteins of interest (POIs) by leveraging the cell's natural protein degradation machinery. To confirm that PROTAC-induced proximity drives protein degradation, target validation and ternary complex formation must be thoroughly assessed.

AREAS COVERED

In this perspective, the authors detail some of the most widely used in silico, structural, in vitro, and in cellulo methods to validate PROTAC target engagement and ternary complex formation. Additionally, they discuss the growing use of PROTACs as chemical probes for novel target identification and validation.

EXPERT OPINION

Target validation is essential in the PROTAC approach, and ongoing studies should prioritize confirming ternary complex formation using assays conducted under physiologically relevant cellular conditions. Proteomics analyses are among the most valuable tools for elucidating PROTAC mechanisms, selectivity, and outcomes. The authors are optimistic about the future of PROTACs in drug development and their use as probes to confirm target engagement. PROTAC technology holds vast opportunities for future exploration, offering significant potential to further both chemical and biological research.

Advancing brain tumor therapy: unveiling the potential of PROTACs for targeted protein degradation

The long-term treatment of malignancies, particularly brain tumors, is challenged by abnormal protein expression and drug resistance. In terms of potency, selectivity, and overcoming drug resistance, Proteolysis Targeting Chimeras (PROTACs), a cutting-edge method used to selectively degrade target proteins, beats traditional inhibitors. This review summarizes recent research on using PROTACs as a therapeutic strategy for brain tumors, focusing on their mechanism, benefits, limitations, and the need for optimization. The review draws from a comprehensive search of peer-reviewed literature, scientific databases, and clinical trial databases. Articles published up to the knowledge cutoff date up to 14 April 2023 were included. Inclusion criteria covered PROTAC-based brain tumor therapies, including preclinical and early clinical studies, with no restrictions on design or publication type. We included studies using in vitro, in vivo brain tumor models, and human subjects. Eligible treatments involved PROTACs targeting proteins linked to brain tumor progression. We evaluated the selected studies for methodology, including design, sample size, and data analysis techniques. A narrative synthesis summarized key outcomes and trends in PROTAC-based brain tumor therapy. Recent research shows PROTACs selectively degrade brain tumor-related proteins with minimal off-target effects. They offer enhanced potency, selectivity, and the ability to combat resistance compared to traditional inhibitors. PROTACs hold promise for brain tumor treatment offering advantages over traditional inhibitors, but more research is needed to refine their mechanisms, efficacy, and safety. Larger-scale trials and translational studies are essential for assessing their clinical utility.

Rapid and high-throughput screening of proteolysis targeting chimeras using a dual-reporter system expressing fluorescence protein and luciferase

BACKGROUND

Proteolysis targeting chimera (PROTAC), a novel drug discovery strategy, utilizes the ubiquitin-proteasome system to degrade target proteins in cells. While Western blotting, mass spectrometry, and Lumit Immunoassay have been instrumental in determining protein levels, the rapid screening of PROTACs continues to pose challenges, necessitating the development of alternative methodologies.

RESULTS

We herein reported an alternative high-throughput method for screening PROTACs using a dual-reporter system expressing a Renilla luciferase (RLUC)-fused target protein and enhanced green fluorescent protein (EGFP). EGFP served as an internal reference and RLUC as an indicated target protein degradation. Rapid measurement of EGFP or RLUC light signals was achieved using a fluorescence/luminescence plate-based reader in the endpoint mode. The feasibility of the screening model was tested using ARV110, a clinical trial-stage PROTAC targeting the androgen receptor (AR). In EGFP/RLUC-tAR-expressing modal cells treated with varying concentrations of ARV110, normalized RLUC luminescence decreased dose-dependently, as confirmed via western blotting detection of AR expression. Then the platform was used to practically screen Sirtuin 2 (SIRT2) degraders from a small group of PROTACs that we built. Normalized RLUC luminescence changes in model cells expressing EGFP/RLUC-SIRT2 reflected the degradation efficiencies of PROTACs. Compounds 128 and 129 exhibited the highest degradation efficacies, leading to dose-dependent degradation of endogenous SIRT2 protein in the MCF-7 cell line and inducing cell growth arrest.

CONCLUSIONS

The dual-reporter system using both fluorescence and chemiluminescence was successfully constructed. Using this method, we identified effective candidate PROTACs against SIRT2. The dual-reporter system may accelerate drug discovery during PROTAC development.

Development of a versatile system for evaluating the target protein degradation activity of novel ubiquitin ligases utilizing existing PROTACs

Proteolysis-Targeting Chimeras (PROTAC) are a bifunctional molecule that binds to a protein of interest (POI) and a ubiquitin ligase, thereby inducing the ubiquitination and degradation of POI. Many PROTACs currently utilize a limited number of ubiquitin ligases, such as von Hippel-Lindau (VHL) and Cereblon. Because these ubiquitin ligases are widely expressed in normal tissues, unexpected side effects can occur. Therefore, to expand the repertoire of ubiquitin ligases that can be utilized in PROTACs, we aimed to develop a versatile system to identify suitable novel ubiquitin ligases for PROTAC-mediated protein degradation using existing PROTACs. Chimeric ubiquitin ligases are constructed by fusing VHL with the ubiquitin ligase of interest that is stably expressed in cells. An existing PROTAC that binds to VHL was added to the cells, and the POI degradation activity was evaluated. In this study, we showed that epidermal growth factor receptor can be degraded by an existing PROTAC utilizing a chimeric ubiquitin ligase that fuses VHL and endoplasmic reticulum-localized ubiquitin ligase, HRD1. These results demonstrate that this novel approach can be used to identify suitable ubiquitin ligases for PROTAC-mediated degradation using existing PROTACs. Expanding the repertoire of ubiquitin ligases that can be utilized for PROTAC by using this versatile system is expected to enable the development of more effective and specific PROTACs for cancer and other diseases.

An overview of GPX4-targeting TPDs for cancer therapy

Ferroptosis is a newly identified form of regulated, non-apoptotic cell death caused by iron-dependent phospholipid peroxidation. Glutathione peroxidase 4 (GPX4) inactivation-induced ferroptosis is an efficient antitumor treatment. Currently, several GPX4 inhibitors have been identified. However, these inhibitors exhibit low selectivity and poor pharmacokinetic properties that preclude their clinical use. Targeted protein degradation (TPD) is an efficient strategy for discovering drugs and has unique advantages over target protein inhibition. Given GPX4's antitumor effects and the potential of TPD, researchers have explored GPX4-targeting TPDs, which outperform conventional inhibitors in several aspects, such as increased selectivity, strong anti-proliferative effects, overcoming drug resistance, and enhancing drug-like properties. In this review, we comprehensively summarize the progress in GPX4-targeting TPDs. In addition, we reviewed the changes and challenges related to the development of GPX4-targeting TPDs for cancer therapy.

Discovery of a potent PARP1 PROTAC as a chemosensitizer for the treatment of colorectal cancer

Given the vulnerability of colorectal cancer (CRC) patients could not obtain a sustained benefit from chemotherapy, combination therapy is frequently employed as a treatment strategy. Targeting PARP1 blockade exhibit specific toxicity towards tumor cells with BRCA1 or BRCA2 mutations through synthetic lethality. This study focuses on developing a series of potent PROTACs targeting PARP1 in order to enhance the sensitivity of CRC cells with BRCA1 or BRCA2 mutations to chemotherapy. Compound C6, obtained based on precise structural optimization of the linker, has been shown to effectively degrade PARP1 with a DC50 value of 58.14 nM. Furthermore, C6 significantly increased the cytotoxic efficacy of SN-38, an active metabolite of Irinotecan, in BRCA-mutated CRC cells, achieving a favorable combination index (CI) of 0.487. In conclusion, this research underscores the potential benefits of employing a combination therapy that utilizes PAPRP1 degrader C6 alongside Irinotecan for CRC patients harboring BRCA mutations in CRC.

Controllable multivalent LYTACs enhance targeted protein degradation

We present a versatile DNA-based LYTAC framework that allows control over the valency of chimeras and the distance between ligands through DNA self-assembly. By evaluating the degradation capabilities of LYTACs with 1, 3, and 9 valences, we confirm the broad applicability of the multivalent enhancement effect across different lysosome-targeting receptor-mediated degradation pathways. Our findings provide valuable insights into improving the degradation efficiency of LYTACs.

One-Step Regioselective Synthesis of N-1-Substituted Dihydrouracils: A Motif of Growing Popularity in the Targeted Protein Degradation Field

The increasing popularity of the dihydrouracil motif in cereblon (CRBN) recruiting proteolysis-targeting chimeras (PROTACs) has necessitated the development of a facile, cost-effective, and high-yielding method for its introduction into molecules. To that end, we disclose herein an N-1 selective Pd-catalyzed cross-coupling of dihydrouracil with aryl electrophiles to provide access to medicinally relevant scaffolds in a single step. This approach exhibits excellent functional group tolerance and broad applicability to an abundance of (hetero)aryl halides and phenol derivatives and utilizes readily available catalyst/ligand systems. Thus, our strategy should find broad utility in the arena of PROTAC research, as it obviates the drawbacks of previous methodologies that rely on multistep synthetic routes and protecting group strategies to achieve N-1 selectivity.

Aptamer Proteolysis-Targeting Chimeras (PROTACs): A Novel Strategy to Combat Drug Resistance in Estrogen Receptor α-Positive Breast Cancer

Breast cancer with positive expression of estrogen receptor α (ERα+) accounts for 70% of breast cancer cases, whose predominant treatment is currently endocrine therapy. The main strategy of endocrine therapy for ERα+ breast cancer is to inhibit the ERα signaling pathway and downregulate ERα levels, which often results in mutations in the ligand-binding domain (LBD) of ERα, leading to significant resistance to subsequent treatment in patients. To combat drug resistance, we first proposed a novel aptamer PROTAC strategy through specifically targeted degradation of ERα via targeting the DNA-binding domain (DBD) of ERα. We proved that this strategy is capable of targeting ERα for degradation through ubiquitination, leading to the inhibition of proliferation in ERα+ breast cancer cells and tamoxifen-resistant breast cancer cells. Furthermore, we investigated the mechanisms involved in overcoming resistance. By circumventing drug resistance associated with LBD mutations in ERα, our approach provides a promising avenue for the discovery of new therapeutic agents.

Targeted protein degradation: expanding the technology to facilitate the clearance of neurotoxic proteins in neurodegenerative diseases

In neurodegenerative diseases (NDDs), disruptions in protein homeostasis hinder the clearance of misfolded proteins, causing the formation of misfolded protein oligomers and multimers. The accumulation of these abnormal proteins results in the onset and progression of NDDs. Removal of non-native protein is essential for cell to maintain proteostasis. In recent years, targeted protein degradation (TPD) technologies have become a novel means of treating NDDs by removing misfolded proteins through the intracellular protein quality control system. The TPD strategy includes the participation of two primary pathways, namely the ubiquitin-proteasome pathway (for instance, PROTAC, molecular glue and hydrophobic tag), and the autophagy-lysosome pathway (such as LYTAC, AUTAC and ATTEC). In this review, we systematically present the mechanisms of various TPD strategies employed for neurotoxic protein degradation in NDDs. The article provides an overview of the design, in vitro and in vivo anti-NDD activities and pharmacokinetic properties of these small-molecular degraders. Finally, the advantages, challenges and perspectives of these TPD technologies in NDDs therapy are discussed, providing ideas for further development of small molecule degraders in the realm of NDDs.

Session 5: Protein Degraders

The so-called undruggable space is an exciting area of potential growth for drug development. Undruggable proteins are defined as those unable to be targeted via conventional small molecule drugs. New modalities are being developed to potentially target these proteins. Targeted protein degradation (TPD) is one such new modality, which over the last two decades has moved from academia to industry. TPD makes use of the endogenous degradation machinery present in all cells, in which E3 ubiquitin ligases mark proteins for degradation via ubiquitin attachment. This session explored the challenges and perspectives of using protein degraders as novel therapeutic agents. The session began with a general introduction to the modality, followed by considerations in evaluating their on- and off-target toxicities including data from an IQ Consortium working group survey. Unique absorption, distribution, metabolism, and excretion (ADME) properties of degrader molecules were presented in relation to their effect on drug development and nonclinical safety assessment. The role of transgenic models in evaluating hemotoxicity associated with cereblon-based therapies was then discussed. A case study to derisk dose-limiting thrombocytopenia was also presented. Finally, a regulatory perspective on the challenges of having toxicity associated with protein degraders was presented.

Targeting PRMT5 through PROTAC for the treatment of triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is currently the most aggressive subtype of breast cancer, characterized by high heterogeneity and strong invasiveness, and currently lacks effective therapies. PRMT5, a type II protein arginine methyltransferase, is upregulated in numerous cancers, including TNBC, and plays a critical role, marked it as an attractive therapeutic target. PROTAC (Proteolysis Targeting Chimeras) is an innovative drug development technology that utilizes the ubiquitin-proteasome system (UPS) to degrade target proteins, which is characterized by higher activity, enhanced safety, lower resistance, and reduced toxicity, offering significant value for clinical translation.

METHODS

This study utilizes the PROTAC technology to develop potential degraders targeting PRMT5 in vitro and in vivo.

RESULTS

Through the design, synthesis and screening of a series of targeted compounds, we identified YZ-836P as an effective compound that exerted cytotoxic effects and reduced the protein levels of PRMT5 and its key downstream target protein KLF5 in TNBC after 48 h. Its efficacy was significantly superior to the PRMT5 PROTAC degraders that had been reported. YZ-836P induced G1 phase cell cycle arrest and significantly induced apoptosis in TNBC cells. Additionally, we demonstrated that YZ-836P promoted the ubiquitination and degradation of PRMT5 in a cereblon (CRBN)-dependent manner. Notably, YZ-836P exhibited pronounced efficacy in inhibiting the growth of TNBC patient-derived organoids and xenografts in nude mice.

CONCLUSIONS

These findings position YZ-836P as a promising candidate for advancing treatment modalities for TNBC.

TRIAL REGISTRATION

Ethics Committee of Yunnan Cancer Hospital, KYCS2023-078. Registered 7 June 2023.

CRBN-PROTACs in Cancer Therapy: From Mechanistic Insights to Clinical Applications

Cereblon (CRBN), a member of the E3 ubiquitin ligase complex, has gained significant attention as a therapeutic target in cancer. CRBN regulates the degradation of various proteins in cancer progression, including transcription factors and signaling molecules. PROTACs (proteolysis-targeting chimeras) are a novel approach that uses the cell's degradation system to remove disease-causing proteins selectively. CRBN-dependent PROTACs work by tagging harmful proteins for destruction through the ubiquitin-proteasome system. This strategy offers several advantages over traditional protein inhibition methods, including the potential to overcome drug resistance. Recent progress in developing CRBN-based PROTACs has shown promising preclinical results in both hematologic malignancies and solid tumors. Additionally, CRBN-based PROTACs have enhanced our understanding of CRBN's role in cancer, potentially serving as biomarkers for patient stratification and predicting therapeutic responses. In this review, we delineate the mechanisms of action for CRBN-dependent PROTACs (CRBN-PROTACs), summarize recent advances in preclinical and clinical applications, and provide our perspective on future development.

Cullin-RING Ligase 4 in Cancer: Structure, Functions, and Mechanisms

Cullin-RING ligase 4 (CRL4) has attracted enormous attentions because of its extensive regulatory roles in a wide variety of biological and pathological events, especially cancer-associated events. CRL4 exerts pleiotropic effects by targeting various substrates for proteasomal degradation or changes in activity through different internal compositions to regulate diverse events in cancer progression. In this review, we summarize the structure of CRL4 with manifold compositional modes and clarify the emerging functions and molecular mechanisms of CRL4 in a series of cancer-associated events.

Acetyl-CoA Carboxylase Proteolysis-Targeting Chimeras: Conceptual Design and Application as Insecticides

Novel approaches for pest control are essential to ensure a sufficient food supply for the growing global population. The development of new insecticides must meet rigorous regulatory requirements for safety and address the resistance issues of existing insecticides. Proteolysis-targeting chimeras (PROTACs), originally developed for human diseases, show promise in agriculture. They offer innovative insecticides tailored to overcome resistance, opening avenues for agricultural applications. In this study, we developed small-molecule degraders by incorporating pomalidomide as an E3 ligand. These degraders were linked to a ligand (spirotetratmat enol) targeting the ACC protein through a flexible chain, aiming to achieve the efficient control of insects. Compounds 9a-9d were designed, synthesized, and evaluated for biological activities and mechanisms. Among them, 9b exhibited superior potency against Aphis craccivora (LC50 = 107.8 μg mL-1) compared to others and effectively degraded ACC proteins through the ubiquitin-proteasome system. These findings highlight the potential of utilizing PROTAC-based approaches in the development of insecticides for efficient pest control.

Targeted Protein Degradation (TPD) for Immunotherapy: Understanding Proteolysis Targeting Chimera-Driven Ubiquitin-Proteasome Interactions

Targeted protein degradation or TPD, is rapidly emerging as a treatment that utilizes small molecules to degrade proteins that cause diseases. TPD allows for the selective removal of disease-causing proteins, including proteasome-mediated degradation, lysosome-mediated degradation, and autophagy-mediated degradation. This approach has shown great promise in preclinical studies and is now being translated to treat numerous diseases, including neurodegenerative diseases, infectious diseases, and cancer. This review discusses the latest advances in TPD and its potential as a new chemical modality for immunotherapy, with a special focus on the innovative applications and cutting-edge research of PROTACs (Proteolysis TArgeting Chimeras) and their efficient translation from scientific discovery to technological achievements. Our review also addresses the significant obstacles and potential prospects in this domain, while also offering insights into the future of TPD for immunotherapeutic applications.

A Large-Scale Genome-Wide Study of Gene-Sleep Duration Interactions for Blood Pressure in 811,405 Individuals from Diverse Populations

Although both short and long sleep duration are associated with elevated hypertension risk, our understanding of their interplay with biological pathways governing blood pressure remains limited. To address this, we carried out genome-wide cross-population gene-by-short-sleep and long-sleep duration interaction analyses for three blood pressure traits (systolic, diastolic, and pulse pressure) in 811,405 individuals from diverse population groups. We discover 22 novel gene-sleep duration interaction loci for blood pressure, mapped to 23 genes. Investigating these genes' functional implications shed light on neurological, thyroidal, bone metabolism, and hematopoietic pathways that necessitate future investigation for blood pressure management that caters to sleep health lifestyle. Non-overlap between short sleep (12) and long sleep (10) interactions underscores the plausible nature of distinct influences of both sleep duration extremes in cardiovascular health. Several of our loci are specific towards a particular population background or sex, emphasizing the importance of addressing heterogeneity entangled in gene-environment interactions, when considering precision medicine design approaches for blood pressure management.

Development of Degraders of Cyclin-Dependent Kinases and Based on Rational Drug Design

Degradation of target proteins has been considered to be a promising therapeutic approach, but the rational design of compounds for degradation remains a challenge. In this study, we reasonably designed and synthesized only 10 compounds to discover effective CDK4/6 protein degraders. Among the newly synthesized compounds, 7f achieved dual degradation of CDK4/6 protein, with DC50 values of 10.5 and 2.5 nM, respectively. Compound 7f also exhibited inhibitory proliferative activity against Jurkat cells with an IC50 value of 0.18 μM. Furthermore, 7f induced cell apoptosis and G1 phase cell cycle arrest in a dose-dependent manner in Jurkat cells. In conclusion, these findings demonstrate the potential of 7f as a CDK4/6 degrader and a potential therapeutic strategy against cancer, thereby expanding the potential of CDK4/6 dual PROTACs.

Expanding the horizons of targeted protein degradation: A non-small molecule perspective

Targeted protein degradation (TPD) represented by proteolysis targeting chimeras (PROTACs) marks a significant stride in drug discovery. A plethora of innovative technologies inspired by PROTAC have not only revolutionized the landscape of TPD but have the potential to unlock functionalities beyond degradation. Non-small-molecule-based approaches play an irreplaceable role in this field. A wide variety of agents spanning a broad chemical spectrum, including peptides, nucleic acids, antibodies, and even vaccines, which not only prove instrumental in overcoming the constraints of conventional small molecule entities but also provided rapidly renewing paradigms. Herein we summarize the burgeoning non-small molecule technological platforms inspired by PROTACs, including three major trajectories, to provide insights for the design strategies based on novel paradigms.

UNC-45A: A potential therapeutic target for malignant tumors

Uncoordinated mutant number-45 myosin chaperone A (UNC-45A), a protein highly conserved throughout evolution, is ubiquitously expressed in somatic cells. It is correlated with tumorigenesis, proliferation, metastasis, and invasion of multiple malignant tumors. The current understanding of the role of UNC-45A in tumor progression is mainly related to the regulation of non-muscle myosin II (NM-II). However, many studies have suggested that the mechanisms by which UNC-45A is involved in tumor progression are far greater than those of NM-II regulation. UNC-45A can also promote tumor cell proliferation by regulating checkpoint kinase 1 (ChK1) phosphorylation or the transcriptional activity of nuclear receptors, and induces chemoresistance to paclitaxel in tumor cells by destabilizing microtubule activity. In this review, we discuss the recent advances illuminating the role of UNC-45A in tumor progression. We also put forward therapeutic strategies targeting UNC-45A, in the hope of paving the way the development of UNC-45A-targeted therapies for patients with malignant tumors.

Development of Peptide Displacement Assays to Screen for Antagonists of DDB1 Interactions

The DNA damage binding protein 1 (DDB1) is an essential component of protein complexes involved in DNA damage repair and the ubiquitin-proteasome system (UPS) for protein degradation. As an adaptor protein specific to Cullin-RING E3 ligases, DDB1 binds different receptors that poise protein substrates for ubiquitination and subsequent degradation by the 26S proteasome. Examples of DDB1-binding protein receptors are Cereblon (CRBN) and the WD-repeat containing DDB1- and CUL4-associated factors (DCAFs). Cognate substrates of CRBN and DCAFs are involved in cancer-related cellular processes or are mimicked by viruses to reprogram E3 ligases for the ubiquitination of antiviral host factors. Thus, disrupting interactions of DDB1 with receptor proteins might be an effective strategy for anticancer and antiviral drug discovery. Here, we developed fluorescence polarization (FP)-based peptide displacement assays that utilize full-length DDB1 and fluorescein isothiocyanate (FITC)-labeled peptide probes derived from the specific binding motifs of DDB1 interactors. A general FP-based assay condition applicable to diverse peptide probes was determined and optimized. Mutagenesis and biophysical analyses were then employed to identify the most suitable peptide probe. The FITC-DCAF15 L49A peptide binds DDB1 with a dissociation constant of 68 nM and can be displaced competitively by unlabeled peptides at sub-μM to low nM concentrations. These peptide displacement assays can be used to screen small molecule libraries to identify novel modulators that could specifically antagonize DDB1 interactions toward development of antiviral and cancer therapeutics.

New-generation advanced PROTACs as potential therapeutic agents in cancer therapy

Proteolysis-targeting chimeras (PROTACs) technology has garnered significant attention over the last 10 years, representing a burgeoning therapeutic approach with the potential to address pathogenic proteins that have historically posed challenges for traditional small-molecule inhibitors. PROTACs exploit the endogenous E3 ubiquitin ligases to facilitate degradation of the proteins of interest (POIs) through the ubiquitin-proteasome system (UPS) in a cyclic catalytic manner. Despite recent endeavors to advance the utilization of PROTACs in clinical settings, the majority of PROTACs fail to progress beyond the preclinical phase of drug development. There are multiple factors impeding the market entry of PROTACs, with the insufficiently precise degradation of favorable POIs standing out as one of the most formidable obstacles. Recently, there has been exploration of new-generation advanced PROTACs, including small-molecule PROTAC prodrugs, biomacromolecule-PROTAC conjugates, and nano-PROTACs, to improve the in vivo efficacy of PROTACs. These improved PROTACs possess the capability to mitigate undesirable physicochemical characteristics inherent in traditional PROTACs, thereby enhancing their targetability and reducing off-target side effects. The new-generation of advanced PROTACs will mark a pivotal turning point in the realm of targeted protein degradation. In this comprehensive review, we have meticulously summarized the state-of-the-art advancements achieved by these cutting-edge PROTACs, elucidated their underlying design principles, deliberated upon the prevailing challenges encountered, and provided an insightful outlook on future prospects within this burgeoning field.

Hippo pathway in non-small cell lung cancer: mechanisms, potential targets, and biomarkers

Lung cancer is the primary contributor to cancer-related deaths globally, and non-small cell lung cancer (NSCLC) constitutes around 85% of all lung cancer cases. Recently, the emergence of targeted therapy and immunotherapy revolutionized the treatment of NSCLC and greatly improved patients' survival. However, drug resistance is inevitable, and extensive research has demonstrated that the Hippo pathway plays a crucial role in the development of drug resistance in NSCLC. The Hippo pathway is a highly conserved signaling pathway that is essential for various biological processes, including organ development, maintenance of epithelial balance, tissue regeneration, wound healing, and immune regulation. This pathway exerts its effects through two key transcription factors, namely Yes-associated protein (YAP) and transcriptional co-activator PDZ-binding motif (TAZ). They regulate gene expression by interacting with the transcriptional-enhanced associate domain (TEAD) family. In recent years, this pathway has been extensively studied in NSCLC. The review summarizes a comprehensive overview of the involvement of this pathway in NSCLC, and discusses the mechanisms of drug resistance, potential targets, and biomarkers associated with this pathway in NSCLC.

Protein degraders - from thalidomide to new PROTACs

Recently, the development of protein degraders (protein-degrading compounds) has prominently progressed. There are two remarkable classes of protein degraders: proteolysis-targeting chimeras (PROTACs) and molecular glue degraders (MGDs). Almost 70 years have passed since thalidomide was initially developed as a sedative-hypnotic drug, which is currently recognized as one of the most well-known MGDs. During the last two decades, a myriad of PROTACs and MGDs have been developed, and the molecular mechanism of action (MOA) of thalidomide was basically elucidated, including identifying its molecular target cereblon (CRBN). CRBN forms a Cullin Ring Ligase 4 with Cul4 and DDB1, whose substrate specificity is controlled by its binding ligands. Thalidomide, lenalidomide and pomalidomide, three CRBN-binding MGDs, were clinically approved to treat several intractable diseases (including multiple myeloma). Several other MGDs and CRBN-based PROTACs (ARV-110 and AVR-471) are undergoing clinical trials. In addition, several new related technologies regarding PROTACs and MGDs have also been developed, and achievements of protein degraders impact not only therapeutic fields but also basic biological science. In this article, I introduce the history of protein degraders, from the development of thalidomide to the latest PROTACs and related technologies.

Optimization of Potent Ligands for the E3 Ligase DCAF15 and Evaluation of Their Use in Heterobifunctional Degraders

Unlocking novel E3 ligases for use in heterobifunctional PROTAC degraders is of high importance to the pharmaceutical industry. Over-reliance on the current suite of ligands used to recruit E3 ligases could limit the potential of their application. To address this, potent ligands for DCAF15 were optimized using cryo-EM supported, structure-based design to improve on micromolar starting points. A potent binder, compound 24, was identified and subsequently conjugated into PROTACs against multiple targets. Following attempts on degrading a number of proteins using DCAF15 recruiting PROTACs, only degradation of BRD4 was observed. Deconvolution of the mechanism of action showed that this degradation was not mediated by DCAF15, thereby highlighting both the challenges faced when trying to expand the toolbox of validated E3 ligase ligands for use in PROTAC degraders and the pitfalls of using BRD4 as a model substrate.

Breaking Bad Proteins-Discovery Approaches and the Road to Clinic for Degraders

Proteolysis-targeting chimeras (PROTACs) describe compounds that bind to and induce degradation of a target by simultaneously binding to a ubiquitin ligase. More generally referred to as bifunctional degraders, PROTACs have led the way in the field of targeted protein degradation (TPD), with several compounds currently undergoing clinical testing. Alongside bifunctional degraders, single-moiety compounds, or molecular glue degraders (MGDs), are increasingly being considered as a viable approach for development of therapeutics, driven by advances in rational discovery approaches. This review focuses on drug discovery with respect to bifunctional and molecular glue degraders within the ubiquitin proteasome system, including analysis of mechanistic concepts and discovery approaches, with an overview of current clinical and pre-clinical degrader status in oncology, neurodegenerative and inflammatory disease.

What influences the activity of Degrader-Antibody conjugates (DACs)

The targeted protein degradation (TPD) technology employing proteolysis-targeting chimeras (PROTACs) has been widely applied in drug chemistry and chemical biology for the treatment of cancer and other diseases. PROTACs have demonstrated significant advantages in targeting undruggable targets and overcoming drug resistance. However, despite the efficient degradation of targeted proteins achieved by PROTACs, they still face challenges related to selectivity between normal and cancer cells, as well as issues with poor membrane permeability due to their substantial molecular weight. Additionally, the noteworthy toxicity resulting from off-target effects also needs to be addressed. To solve these issues, Degrader-Antibody Conjugates (DACs) have been developed, leveraging the targeting and internalization capabilities of antibodies. In this review, we elucidates the characteristics and distinctions between DACs, and traditional Antibody-drug conjugates (ADCs). Meanwhile, we emphasizes the significance of DACs in facilitating the delivery of PROTACs and delves into the impact of various components on DAC activity. These components include antibody targets, drug-antibody ratio (DAR), linker types, PROTACs targets, PROTACs connections, and E3 ligase ligands. The review also explores the suitability of different targets (antibody targets or PROTACs targets) for DACs, providing insights to guide the design of PROTACs better suited for antibody conjugation.

A Large-Scale Genome-Wide Study of Gene-Sleep Duration Interactions for Blood Pressure in 811,405 Individuals from Diverse Populations

Although both short and long sleep duration are associated with elevated hypertension risk, our understanding of their interplay with biological pathways governing blood pressure remains limited. To address this, we carried out genome-wide cross-population gene-by-short-sleep and long-sleep duration interaction analyses for three blood pressure traits (systolic, diastolic, and pulse pressure) in 811,405 individuals from diverse population groups. We discover 22 novel gene-sleep duration interaction loci for blood pressure, mapped to genes involved in neurological, thyroidal, bone metabolism, and hematopoietic pathways. Non-overlap between short sleep (12) and long sleep (10) interactions underscores the plausibility of distinct influences of both sleep duration extremes in cardiovascular health. With several of our loci reflecting specificity towards population background or sex, our discovery sheds light on the importance of embracing granularity when addressing heterogeneity entangled in gene-environment interactions, and in therapeutic design approaches for blood pressure management.

PROTAC-biomacromolecule conjugates for precise protein degradation in cancer therapy: A review

Proteolysis targeting chimera (PROTAC) technology is a promising new mode of targeted protein degradation with significant transformative implications for the clinical treatment of different diseases. Nevertheless, while this technology offers numerous advantages, on-target off-tumour toxicity in healthy cells remains a major challenge for clinical application in cancer therapy. Strategies are presently being explored to optimize degradation activity with cellular selectivity to minimize undesirable side effects. PROTAC-antibody conjugates and PROTAC-aptamer conjugates are unique innovations that combine PROTACs and biomacromolecules. These novel PROTAC-biomacromolecule conjugates (PBCs) can enhance the targetability of PROTACs and reduce their off-target side-effects. The combination of potent PROTACs and highly safe biomacromolecules will pioneer an emerging trend in targeted protein degradation. In our review, we have summarized recent advances in PBCs, discussed current challenges, and outlooked opportunities for future research in the field.

New generation estrogen receptor-targeted agents in breast cancer: present situation and future prospectives

Endocrine therapy which blocking the signaling of estrogen receptor, has long been effective for decades as a primary treatment choice for breast cancer patients expressing ER. However, the issue of drug resistance poses a significant clinical challenge. It's critically important to create new therapeutic agents that can suppress ERα activity, particularly in cases of ESR1 mutations. This review highlights recent efforts in drug development of next generation ER-targeted agents, including oral selective ER degraders (SERDs), proteolysis targeting chimera (PROTAC) ER degraders, other innovative molecules such as complete estrogen receptor antagonists (CERANs) and selective estrogen receptor covalent antagonists (SERCAs). The drug design, efficacy and clinical trials for each compound were detailed.

Advancing PROTAC Characterization: Structural Insights through Adducts and Multimodal Tandem-MS Strategies

Proteolysis targeting chimeras (PROTACs) are specialized molecules that bind to a target protein and a ubiquitin ligase to facilitate protein degradation. Despite their significance, native PROTACs have not undergone tandem mass spectrometry (MS) analysis. To address this gap, we conducted a pioneering investigation on the fragmentation patterns of two PROTACs in development, dBET1 and VZ185. Employing diverse cations (sodium, lithium, and silver) and multiple tandem-MS techniques, we enhanced their structural characterization. Notably, lithium cations facilitated comprehensive positive-mode coverage for dBET1, while negative polarity mode offered richer insights. Employing de novo structure determination on 2DMS data from degradation studies yielded crucial insights. In the case of VZ185, various charge states were observed, with [M + 2H]2+ revealing fewer moieties than [M + H]+ due to charge-related factors. Augmenting structural details through silver adducts suggested both charge-directed and charge-remote fragmentation. This comprehensive investigation identifies frequently dissociated bonds across multiple fragmentation techniques, pinpointing optimal approaches for elucidating PROTAC structures. The findings contribute to advancing our understanding of PROTACs, pivotal for their continued development as promising therapeutic agents.

CYP1A inhibitors: Recent progress, current challenges, and future perspectives

Mammalian cytochrome P450 1A (CYP1A) are key phase I xenobiotic-metabolizing enzymes that play a distinctive role in metabolic activation or metabolic clearance of a variety of procarcinogens, drugs, and endogenous substances. Human CYP1A subfamily contains two members (hCYP1A1 and hCYP1A2), which are known to catalyze the oxidative activation of some environmental procarcinogens into carcinogenic species. Increasing evidence has demonstrated that CYP1A inhibitor therapies are promising strategies for cancer chemoprevention or overcoming CYP1A-associated drug toxicity and resistance. Herein, we reviewed recent advances in the discovery and characterization of hCYP1A inhibitors, from the discovery approaches to structural features and biomedical applications of hCYP1A inhibitors. The inhibition potentials, inhibition modes, and inhibition constants of all reported hCYP1A inhibitors are comprehensively summarized. Meanwhile, the structural features and structure-activity relationships of different classes of hCYP1A1 and hCYP1A2 inhibitors are analyzed and discussed in depth. Furthermore, the major challenges and future directions for this field are presented and highlighted. Collectively, the information and knowledge presented here will strongly facilitate the researchers to discover and develop more efficacious CYP1A inhibitors for specific purposes, such as chemo-preventive agents or as tool molecules in hCYP1A-related fundamental studies.

Complete elimination of estrogen receptor α by PROTAC estrogen receptor α degrader ERD-148 in breast cancer cells

PURPOSE

Estrogen Receptor α (ERα) is a well-established therapeutic target for Estrogen Receptor (ER)-positive breast cancers. Both Selective Estrogen Receptor Degraders (SERD) and PROTAC ER degraders are synthetic compounds suppressing the ER activity through the degradation of ER. However, the differences between SERD and PROTAC ER degraders are far from clear.

METHODS

The effect of PROTAC ER degrader ERD-148 and SERD fulvestrant on protein degradation was evaluated by western blot analysis. The cell proliferation was tested by WST-8 assays and the gene expressions were assessed by gene microarray and real-time RT-PCR analysis after the compound treatment.

RESULTS

ERD-148 is a potent and selective PROTAC ERα degrader. It degrades not only unphosphorylated ERα but also the phosphorylated ERα in the cells. In contrast, the SERD fulvestrant showed much-reduced degradation potency on the phosphorylated ERα. The more complete degradation of ERα by ERD-148 translates into a greater maximum cell growth inhibition. However, ERD-148 and fulvestrant share a similar gene regulation profile except for the variation of regulation potency. Further studies indicate that ERD-148 degrades the ERα in fulvestrant-resistant cells.

CONCLUSION

PROTAC ER degrader has a different mechanism of action compared to SERD which may be used in treating fulvestrant-resistant cancers.

One-Pot Synthesis of Cereblon Proteolysis Targeting Chimeras via Photoinduced C(sp2)-C(sp3) Cross Coupling and Amide Formation for Proteolysis Targeting Chimera Library Synthesis

In this study, a one-pot synthesis via photoinduced C(sp2)-C(sp3) coupling followed by amide formation to access proteolysis targeting chimeras (PROTACs) was developed. The described protocol was studied on cereblon (CRBN)-based E3-ligase binders and (+)-JQ-1, a bromodomain inhibitor, to generate BET (bromodomain and extra terminal domain) targeting protein degraders. The generated PROTACs were profiled in vitro and tested for their degradation ability with several potent candidates identified. Upfront, the individual reactions of the one-pot transformation were carefully optimized for CRBN binder functionalization and multiple heterobifunctional linker moieties were designed and synthesized. Separate scopes detailing the C(sp2)-C(sp3) coupling and one-pot PROTAC synthesis are described in this report as well as a library miniaturization study showing the high-throughput compatibility. Overall, the developed protocol provides rapid access to PROTACs in a single process, thereby allowing efficient generation of CRBN-based PROTAC libraries.

A Degron Blocking Strategy Towards Improved CRL4CRBN Recruiting PROTAC Selectivity

Small molecules inducing protein degradation are important pharmacological tools to interrogate complex biology and are rapidly translating into clinical agents. However, to fully realise the potential of these molecules, selectivity remains a limiting challenge. Herein, we addressed the issue of selectivity in the design of CRL4CRBN recruiting PROteolysis TArgeting Chimeras (PROTACs). Thalidomide derivatives used to generate CRL4CRBN recruiting PROTACs have well described intrinsic monovalent degradation profiles by inducing the recruitment of neo-substrates, such as GSPT1, Ikaros and Aiolos. We leveraged structural insights from known CRL4CRBN neo-substrates to attenuate and indeed remove this monovalent degradation function in well-known CRL4CRBN molecular glues degraders, namely CC-885 and Pomalidomide. We then applied these design principles on a previously published BRD9 PROTAC (dBRD9-A) and generated an analogue with improved selectivity profile. Finally, we implemented a computational modelling pipeline to show that our degron blocking design does not impact PROTAC-induced ternary complex formation. We believe that the tools and principles presented in this work will be valuable to support the development of targeted protein degradation.

New insights into the suppression of inflammation and lipid accumulation by JAZF1

Atherosclerosis is one of the leading causes of disease and death worldwide. The identification of new therapeutic targets and agents is critical. JAZF1 is expressed in many tissues and is found at particularly high levels in adipose tissue (AT). JAZF1 suppresses inflammation (including IL-1β, IL-4, IL-6, IL-8, IL-10, TNFα, IFN-γ, IAR-20, COL3A1, laminin, and MCP-1) by reducing NF-κB pathway activation and AT immune cell infiltration. JAZF1 reduces lipid accumulation by regulating the liver X receptor response element (LXRE) of the SREBP-1c promoter, the cAMP-response element (CRE) of HMGCR, and the TR4 axis. LXRE and CRE sites are present in many cytokine and lipid metabolism gene promoters, which suggests that JAZF1 regulates these genes through these sites. NF-κB is the center of the JAZF1-mediated inhibition of the inflammatory response. JAZF1 suppresses NF-κB expression by suppressing TAK1 expression. Interestingly, TAK1 inhibition also decreases lipid accumulation. A dual-targeting strategy of NF-κB and TAK1 could inhibit both inflammation and lipid accumulation. Dual-target compounds (including prodrugs) 1-5 exhibit nanomolar inhibition by targeting NF-κB and TAK1, EGFR, or COX-2. However, the NF-κB suppressing activity of these compounds is relatively low (IC50 > 300 nM). Compounds 6-14 suppress NF-κB expression with IC50 values ranging from 1.8 nM to 38.6 nM. HS-276 is a highly selective, orally bioavailable TAK1 inhibitor. Combined structural modifications of compounds using a prodrug strategy may enhance NF-κB inhibition. This review focused on the role and mechanism of JAZF1 in inflammation and lipid accumulation for the identification of new anti-atherosclerotic targets.

Discovery of a SHP2 Degrader with In Vivo Anti-Tumor Activity

Src homology 2 domain-containing phosphatase 2 (SHP2) is an attractive target for cancer therapy due to its multifaceted roles in both tumor and immune cells. Herein, we designed and synthesized a novel series of proteolysis targeting chimeras (PROTACs) using a SHP2 allosteric inhibitor as warhead, with the goal of achieving SHP2 degradation both inside the cell and in vivo. Among these molecules, compound P9 induces efficient degradation of SHP2 (DC50 = 35.2 ± 1.5 nM) in a concentration- and time-dependent manner. Mechanistic investigation illustrates that the P9-mediated SHP2 degradation requires the recruitment of the E3 ligase and is ubiquitination- and proteasome-dependent. P9 shows improved anti-tumor activity in a number of cancer cell lines over its parent allosteric inhibitor. Importantly, administration of P9 leads to a nearly complete tumor regression in a xenograft mouse model, as a result of robust SHP2 depletion and suppression of phospho-ERK1/2 in the tumor. Hence, P9 represents the first SHP2 PROTAC molecule with excellent in vivo efficacy. It is anticipated that P9 could serve not only as a new chemical tool to interrogate SHP2 biology but also as a starting point for the development of novel therapeutics targeting SHP2.

The potential role and mechanism of circRNAs in foam cell formation

Atherosclerosis is a significant risk factor for coronary heart disease (CHD) and myocardial infarction (MI). Atherosclerosis develops during foam cell generation, which is caused by an imbalance in cholesterol uptake, esterification, and efflux. LOX-1, SR-A1, and CD36 all increased cholesterol uptake. ACAT1 and ACAT2 promote free cholesterol (FC) esterification to cholesteryl esters (CE). The hydrolysis of CE to FC was aided by nCEH. FC efflux was promoted by ABCA1, ABCG1, ADAM10, and apoA-I. SR-BI promotes not only cholesterol uptake but also FC efflux. Circular RNAs (circRNAs), which are single-stranded RNAs with a closed covalent circular structure, have emerged as promising biomarkers and therapeutic targets for atherosclerosis due to their highly tissue, cell, and disease state-specific expression profiles. Numerous studies have shown that circRNAs regulate foam cell formation, acting as miRNA sponges to influence atherosclerosis development by regulating the expression of SR-A1, CD36, ACAT2, ABCA1, ABCG1, ADAM10, apoA-I, SR-B1. Several circRNAs, including circ-Wdr91, circ 0004104, circRNA0044073, circRNA_0001805, circDENND1B, circRSF1, circ 0001445, and circRNA 102682, are potential biomarkers for atherosclerosis to better evaluate cardiovascular risk. It is difficult to deliver synthetic therapeutic circRNAs to the desired target tissues. Nanotechnology, such as GA-RM/GZ/PL, may be an important solution to this problem. In this review, we focus on the potential role and mechanism of circRNA/miRNA axis in foam cell formation in the hopes of discovering new targets for the diagnosis, prevention, and treatment of atherosclerosis.

Discovery of , a First-in-Class and Orally Bioavailable PROTAC Degrader of the Androgen Receptor Targeting N-Terminal Domain for the Treatment of Prostate Cancer

We report small molecular PROTAC compounds targeting the androgen receptor N-terminal domain (AR-NTD), which were obtained by tethering AR-NTD antagonists and different classes of E3 ligase ligands through chemical linkers. A representative compound, BWA-522, effectively induces degradation of both AR-FL and AR-V7 and is more potent than the corresponding antagonist against prostate cancer (PC) cells in vitro. We have shown that the degradation of AR-FL and AR-V7 proteins by BWA-522 can suppress the expression of AR downstream proteins and induce PC cell apoptosis. BWA-522 achieves 40.5% oral bioavailability in mice and 69.3% in beagle dogs. In a LNCaP xenograft model study, BWA-522 was also proved to be an efficacious PROTAC degrader, resulting in 76% tumor growth inhibition after oral administration of a dose of 60 mg/kg. This study indicates that BWA-522 is a promising AR-NTD PROTAC for the treatment of AR-FL- and AR-V7-dependent tumors.

Affinity and cooperativity modulate ternary complex formation to drive targeted protein degradation

Targeted protein degradation via "hijacking" of the ubiquitin-proteasome system using proteolysis targeting chimeras (PROTACs) has evolved into a novel therapeutic modality. The design of PROTACs is challenging; multiple steps involved in PROTAC-induced degradation make it difficult to establish coherent structure-activity relationships. Herein, we characterize PROTAC-mediated ternary complex formation and degradation by employing von Hippel-Lindau protein (VHL) recruiting PROTACs for two different target proteins, SMARCA2 and BRD4. Ternary-complex attributes and degradation activity parameters are evaluated by varying components of the PROTAC's architecture. Ternary complex binding affinity and cooperativity correlates well with degradation potency and initial rates of degradation. Additionally, we develop a ternary-complex structure modeling workflow to calculate the total buried surface area at the interface, which is in agreement with the measured ternary complex binding affinity. Our findings establish a predictive framework to guide the design of potent degraders.

Epidermal growth factor receptor PROTACs as an effective strategy for cancer therapy: A review

Epidermal growth factor receptor (EGFR), a transmembrane glycoprotein that mediates cellular signaling pathways involved in cell proliferation, angiogenesis, apoptosis, and metastatic spread, is an important oncogenic drug target. Targeting the intracellular and extracellular domains of the EGFR has been authorized for a number of small-molecule TKIs and mAbs, respectively. However, their clinical application is limited by EGFR catalytic structural domain alterations, cancer heterogeneity, and persistent drug resistance. To bypass these limitations, protease-targeted chimeras (PROTACs) are emerging as an emerging and promising anti-EGFR therapy. PROTACs compensate for the limitations of traditional occupancy-driven small molecules by exploiting intracellular protein destruction processes. Recently, a mushrooming number of heterobifunctional EGFR PROTACs have been created using wild-type (WT) and mutated EGFR TKIs. PROTACs outperformed EGFR TKIs in terms of cellular inhibition, potency, toxicity profiles, and anti-drug resistance. Herein, we present a comprehensive overview of the development of PROTACs targeting EGFR for cancer therapy, while also highlighting the challenges and opportunities associated with the field.

The recent advance of Interleukin-1 receptor associated kinase 4 inhibitors for the treatment of inflammation and related diseases

The interleukin-1 receptor associated kinase 4 (IRAK-4) is a member of serine-threonine kinase family, which plays an important role in the regulation of interleukin-1 receptors (IL-1R) and Toll-like receptors (TLRs) related signaling pathways. At present, the IRAK-4 mediated inflammation and related signaling pathways contribute to inflammation, which are also responsible for other autoimmune diseases and drug resistance in cancers. Therefore, targeting IRAK-4 to develop single-target, multi-target inhibitors and proteolysis-targeting chimera (PROTAC) degraders is an important direction for the treatment of inflammation and related diseases. Moreover, insight into the mechanism of action and structural optimization of the reported IRAK-4 inhibitors will provide the new direction to enrich the clinical therapies for inflammation and related diseases. In this comprehensive review, we introduced the recent advance of IRAK-4 inhibitors and degraders with regards to structural optimization, mechanism of action and clinical application that would be helpful for the development of more potent chemical entities against IRAK-4.

PROTACs: A novel strategy for cancer drug discovery and development

Proteolysis targeting chimera (PROTAC) technology has become a powerful strategy in drug discovery, especially for undruggable targets/proteins. A typical PROTAC degrader consists of three components: a small molecule that binds to a target protein, an E3 ligase ligand (consisting of an E3 ligase and its small molecule recruiter), and a chemical linker that hooks first two components together. In the past 20 years, we have witnessed advancement of multiple PROTAC degraders into the clinical trials for anticancer therapies. However, one of the major challenges of PROTAC technology is that only very limited number of E3 ligase recruiters are currently available as E3 ligand for targeted protein degradation (TPD), although human genome encodes more than 600 E3 ligases. Thus, there is an urgent need to identify additional effective E3 ligase recruiters for TPD applications. In this review, we summarized the existing RING-type E3 ubiquitin ligase and their small molecule recruiters that act as effective E3 ligands of PROTAC degraders and their application in anticancer drug discovery. We believe that this review could serve as a reference in future development of efficient E3 ligands of PROTAC technology for cancer drug discovery and development.

Formation of C(sp2)-C(sp3) Bonds Instead of Amide C-N Bonds from Carboxylic Acid and Amine Substrate Pools by Decarbonylative Cross-Electrophile Coupling

Carbon-heteroatom bonds, most often amide and ester bonds, are the standard method to link together two complex fragments because carboxylic acids, amines, and alcohols are ubiquitous and the reactions are reliable. However, C-N and C-O linkages are often a metabolic liability because they are prone to hydrolysis. While C(sp2)-C(sp3) linkages are preferable in many cases, methods to make them require different starting materials or are less functional-group-compatible. We show here a new, decarbonylative reaction that forms C(sp2)-C(sp3) bonds from the reaction of activated carboxylic acids (via 2-pyridyl esters) with activated alkyl groups derived from amines (via N-alkyl pyridinium salts) and alcohols (via alkyl halides). Key to this process is a remarkably fast, reversible oxidative addition/decarbonylation sequence enabled by pyridone and bipyridine ligands that, under reaction conditions that purge CO(g), lead to a selective reaction. The conditions are mild enough to allow coupling of more complex fragments, such as those used in drug development, and this is demonstrated in the coupling of a typical Proteolysis Targeting Chimera (PROTAC) anchor with common linkers via C-C linkages.

PROTACs: Emerging Targeted Protein Degradation Approaches for Advanced Druggable Strategies

A potential therapeutic strategy to treat conditions brought on by the aberrant production of a disease-causing protein is emerging for targeted protein breakdown using the PROTACs technology. Few medications now in use are tiny, component-based and utilize occupancy-driven pharmacology (MOA), which inhibits protein function for a short period of time to temporarily alter it. By utilizing an event-driven MOA, the proteolysis-targeting chimeras (PROTACs) technology introduces a revolutionary tactic. Small-molecule-based heterobifunctional PROTACs hijack the ubiquitin-proteasome system to trigger the degradation of the target protein. The main challenge PROTAC's development facing now is to find potent, tissue- and cell-specific PROTAC compounds with favorable drug-likeness and standard safety measures. The ways to increase the efficacy and selectivity of PROTACs are the main focus of this review. In this review, we have highlighted the most important discoveries related to the degradation of proteins by PROTACs, new targeted approaches to boost proteolysis' effectiveness and development, and promising future directions in medicine.