Proteolysis-targeting chimera (PROTAC) for targeted protein degradation and cancer therapy

BRD4-targeted photodegradation nanoplatform for light activatable melanoma therapy

The targeted protein degradation (TPD) strategy modulates tumor growth pathways by degrading proteins of interest (POIs) and has reshaped anti-tumor drug research and development. Recently, the emergence of photodegradation-targeting chimeras (PDTACs) and laser irradiation at specific sites enables precise spatiotemporal controllability of TPD. Capitalizing on the advances of PDTACs, herein, we report a nanoplatform for efficiently delivering PDTAC molecule for photodegradation of bromodomain-containing protein 4 (BRD4) proteins, the key activators of oncogenic transcription. The PDTAC molecule, named as PPa-JQ1, is synthesized through the covalent attachment of the BRD4-targeting ligand JQ1-acid, to the photosensitizer pyropheophorbide-a (PPa), utilizing a 1,6-hexanediamine linker. The PPa-JQ1 is further encapsulated by human serum albumin (HSA) to obtain the HSA@PPa-JQ1 nanoplatform, which facilitates targeted and efficacious delivery to melanoma lesions. Both in vitro and in vivo therapeutic outcomes demonstrate that HSA@PPa-JQ1 can efficiently generate reactive oxygen species (ROS) to degrade BRD4 upon light irradiation, which eventually induces tumor death. Our study represents the first case to validate the anti-tumor therapeutic efficacy of PDTACs by systemic administration, providing the foundation for further application of PDTACs.

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.

Recent advances in developing targeted protein degraders

Targeted protein degradation (TPD) represents a promising therapeutic approach, encompassing several innovative strategies, including but not limited to proteolysis targeting chimeras (PROTACs), molecular glues, hydrophobic tag tethering degraders (HyTTD), and lysosome-targeted chimeras (LYTACs). Central to TPD are small molecule ligands, which play a critical role in mediating the degradation of target proteins. This review summarizes the current landscape of small molecule ligands for TPD molecules. These small molecule ligands can utilize the proteasome, lysosome, autophagy, or hydrophobic-tagging system to achieve the degradation of target proteins. The article mainly focuses on introducing their design principles, application advantages, and potential limitations. A brief discussion on the development prospects and future directions of TPD technology was also provided.

Biomolecular condensates: A new lens on cancer biology

Cells are compartmentalized into different organelles to ensure precise spatial temporal control and efficient operation of cellular processes. Membraneless organelles, also known as biomolecular condensates, are emerging as previously underappreciated ways of organizing cellular functions. Condensates allow local concentration of protein, RNA, or DNA molecules with shared functions, thus facilitating spatiotemporal control of biochemical reactions spanning a range of cellular processes. Studies discussed herein have shown that aberrant formation of condensates is associated with various diseases such as cancers. Here, we summarize how condensates mechanistically contribute to malignancy-related cellular processes, including genomic instability, epigenetic rewiring, oncogenic transcriptional activation, and signaling. An improved understanding of condensate formation and dissolution will enable development of new cancer therapies. Finally, we address the remaining challenges in the field and suggest future efforts to better integrate condensates into cancer research.

Strategies for the treatment of acute myeloid leukemia with FLT3 mutations: a patent review

INTRODUCTION

Approximately one-third of all AML patients have a mutation in the Fms-like tyrosine kinase 3 (FLT3) gene, which is associated with a poor prognosis in these individuals. The 2017 approval of midostaurin, the first FLT3 inhibitor, spurred extensive development of more potent and selective inhibitors with an improved safety profile.

AREAS COVERED

This review analyzes patent inventions for the treatment of AML using FLT3 inhibitors, covering developments from the earliest to the most recent, disclosed in 2024. Our search using the global Espacenet database identified numerous compounds with low nanomolar inhibitory concentrations against FLT3-ITD and FLT3-TKD mutants. These compounds have shown promise in preclinical studies. Co-inhibition strategies and combinatorial therapies to overcome resistance and enhance anti-leukemic efficacy are also discussed.

EXPERT OPINION

Recent patents highlight advances in the field of FLT3 inhibitors with a focus on overcoming resistance, improving selectivity and potency. Future strategies may include third-generation inhibitors such as type III allosteric inhibitors, irreversible inhibitors, or PROTACs. Personalized medicine approaches utilizing genetic profiling to tailor therapies are emphasized. Exploration of novel combination regimens with emerging therapies like CAR T-cell therapy, immune checkpoint inhibitors, and small molecules targeting critical AML pathways is ongoing to further enhance anti-leukemic efficacy.

Cancer prognosis using base excision repair genes

The base excision repair (BER) pathway is a critical mechanism in genomic stability. This review investigates the role of the BER pathway in advanced cancer therapies considering the pivotal role of genetic factors in cancer patient responses and prognosis. BER factors significantly influence genetic instability and cancer prognosis, as well as the effectiveness of chemotherapy and radiation therapy. In various cancers such as breast, colon, lung, and bladder, BER factors have shown potential as critical biological markers for predicting cancer outcomes. This study focuses on the polymorphisms and expression levels of key BER genes, including OGG1, XRCC1, APE1, and Polβ. Our findings demonstrate that the expression levels of BER genes and proteins are closely associated with the risk, progression, treatment response, and prognosis of various cancers. These insights could improve cancer treatments and aid in the development of drugs targeting BER proteins. Ongoing research in this field requires extensive statistical analyses and large-scale prospective studies to effectively utilize BER protein levels. Ultimately, these results suggest that the BER pathway represents a potential target for cancer diagnosis, prognostic prediction, and the development of personalized therapeutic strategies. This paves the way for effective cancer treatment in the future.

Macrocyclic peptides as a new class of targeted protein degraders

Targeted protein degraders, in the form of proteolysis targeting chimaeras (PROTACs) and molecular glues, leverage the ubiquitin-proteasome system to catalytically degrade specific target proteins of interest. Because such molecules can be extremely potent, they have attracted considerable attention as a therapeutic modality in recent years. However, while targeted degraders have great potential, they are likely to face many of the same challenges as more traditional small molecules when it comes to their development as therapeutics. In particular, existing targeted degrader design is largely only applicable to the same set of protein targets as traditional small molecules (i.e., ∼15% of the human proteome). Here, we consider the potential of macrocyclic peptides to overcome this limitation. Such molecules possess several features that make them well-suited for the role, including the ability to induce the formation of ternary protein complexes that can involve relatively flat surfaces and their structural commonality with E3 ligase-recruiting peptide degrons. For these reasons, macrocyclic peptides provide the opportunity both to broaden the number of targets accessible to degrader activity and to broaden the number of E3 ligases that can be harnessed to mediate that activity.

Next-generation cancer therapeutics: PROTACs and the role of heterocyclic warheads in targeting resistance

One of the major obstacles to sustained cancer treatment effectiveness is the development of medication resistance. Current therapies that block proteins associated with cancer progression often lose their efficacy due to acquired drug resistance, which is frequently driven by mutated or overexpressed protein targets. Proteolysis-targeting chimeras (PROTACs) offer an alternative therapeutic strategy by hijacking the cell's ubiquitin-proteasome system to degrade disease-causing proteins, presenting several potential advantages. Over the past few years, PROTACs have been developed to target various cancer-related proteins, offering new treatment options for patients with previously untreatable malignancies and serving as a foundation for next-generation therapeutics. One of the notable benefits of PROTACs is their ability to overcome certain resistance mechanisms that limit the effectiveness of conventional targeted therapies, as shown in several recent studies. Additionally, research teams are investigating how PROTACs can selectively degrade mutant proteins responsible for resistance to first-line cancer therapies. In the pursuit of novel and effective treatments, this review highlights recent advancements in the development of PROTACs aimed at overcoming cancer resistance. When it comes to drug design, heterocyclic scaffolds often serve as a foundational framework, offering opportunities for modification and optimization of novel molecules. Researchers are similarly exploring various heterocyclic derivatives as "warheads" in the design of PROTACs has been instrumental in pushing the boundaries of targeted protein degradation. As warheads, these heterocyclic compounds are responsible for recognizing and binding to the target protein, which ultimately leads to its degradation via the ubiquitin-proteasome system. This study aims to provide a comprehensive overview of cutting-edge strategies in PROTAC design, offering detailed insights into key concepts and methodologies for creating effective PROTACs. Special emphasis is placed on structure-based rational design, the development of novel warheads, and their critical in influencing biological activity.

Auto-RapTAC: A Versatile and Sustainable Platform for the Automated Rapid Synthesis and Evaluation of PROTAC

The tedious synthesis and limited throughput biological evaluation remain a great challenge for discovering new proteolysis targeting chimera (PROTAC). To rapidly identify potential PROTAC lead compounds, we report a platform named Auto-RapTAC. Based on the modular characteristic of the PROTAC molecule, a streamlined workflow that integrates lab automation with "click chemistry" joint building-block libraries was constructed. This facilitates the autonomous generation of a variety of PROTACs, each with distinct linkers and E3 ligase ligands, all stored in biocompatible solutions. The ready-for-screening (R4S) approach, when paired with fluorescence-based assays, enables the efficient assessment of the PROTAC degradation activity in a high-throughput manner. To further test the capability of the platform, we identify six new PROTACs that target CDK2, CDK12, and BCL6 within a mere 8-day time frame for each target. In all, this platform could find broad application not only in discovering new PROTACs but also in the rapid development of novel heterobifunctional modalities.

Targeted Degradation of SOS1 Exhibits Potent Anticancer Activity and Overcomes Resistance in KRAS-Mutant Tumors and BCR-ABL-Positive Leukemia

Son of sevenless homolog 1 (SOS1) is an essential guanine nucleotide exchange factor for RAS that also plays a critical role in the activation of the small GTPase RAC mediated by BCR-ABL in leukemogenesis. Despite this, small-molecule inhibitors targeting SOS1 have shown limited efficacy in clinical trials for KRAS-mutant cancers, and their potential as a therapeutic approach for chronic myeloid leukemia (CML) remains largely unexplored. In this study, we developed a potent SOS1 proteolysis targeting chimera (PROTAC) SIAIS562055, which was designed by connecting a CRBN ligand to an analog of the SOS1 inhibitor BI-3406. SIAIS562055 exhibited sustained degradation of SOS1 and inhibition of downstream ERK pathways, resulting in superior antiproliferative activity compared with small-molecule inhibitors. SIAIS562055 also potentiated the activity of both KRAS inhibitors in KRAS-mutant cancers and ABL inhibitors in BCR-ABL-positive CML. In KRAS-mutant xenografts, SIAIS562055 displayed promising antitumor potency as a monotherapy and enhanced ERK inhibition and tumor regression when combined with KRAS inhibitors, overcoming acquired resistance. In CML cells, SIAIS562055 promoted the active uptake of BCR-ABL inhibitors by upregulating the carnitine/organic cation transporter SLC22A4. SIAIS562055 and BCR-ABL inhibitors synergistically enhanced inhibition of ABL phosphorylation and downstream signaling, demonstrating robust antitumor activities in both mouse xenografts and primary samples from patients with CML. In summary, this study suggests that PROTAC-mediated SOS1 degradation represents an effective therapeutic strategy for treating not only KRAS-mutant cancers but also BCR-ABL-harboring leukemia. Significance: The PROTAC SIAIS562055 sustainably degrades SOS1 and inhibits downstream ERK signaling, showing strong antiproliferative activity and synergistic effects with KRAS inhibitors in KRAS-mutant cancers and BCR-ABL inhibitors in chronic myeloid leukemia.

Targeting FMS-like tyrosine kinase 3 (FLT3) in acute myeloid leukemia: Novel molecular approaches and therapeutic challenges

Acute myeloid leukemia (AML), a heterogeneous hematologic malignancy, has generally a poor prognosis despite the recent advancements in diagnostics and treatment. Genetic instability, particularly mutations in the FMS-like tyrosine kinase 3 (FLT3) gene, is associated with severe outcomes. Approximately 30 % of AML patients harbor FLT3 mutations, which have been linked to higher relapse and reduced survival rates. Traditional AML treatments employ cytarabine and anthracyclines drugs. Furthermore, the development of FLT3 inhibitors has significantly improved therapy for FLT3-mutated AML patients. For example, the introduction of midostaurin, the first FLT3 inhibitor, improved patient outcomes. However, resistant AML cell clones continue to pose a challenge to the success of AML treatment. This review discusses FLT3 kinase, mutations, and role in AML pathogenesis. It explores the molecular mechanisms of FLT3 activation, signaling pathways, and the structure and function of the FLT3 receptor. Current and emerging therapeutic approaches are presented, while highlighting the latest FLT3 inhibitors in clinical use, and strategies to overcome drug resistance. Future directions, including personalized therapies and novel drug designs, are examined to provide updated insights into FLT3-targeted treatments. This comprehensive review aims to guide clinicians and researchers in the development of innovative therapies to improve AML patient outcomes.

The recent advance and prospect of poly(ADP-ribose) polymerase inhibitors for the treatment of cancer

Chemotherapies are commonly used in cancer therapy, their applications are limited to low specificity, severe adverse reactions, and long-term medication-induced drug resistance. Poly(ADP-ribose) polymerase (PARP) inhibitors are a novel class of antitumor drugs developed to solve these intractable problems based on the mechanism of DNA damage repair, which have been widely applied in the treatment of ovarian cancer, breast cancer, and other cancers through inducing synthetic lethal effect and trapping PARP-DNA complex in BRCA gene mutated cancer cells. In recent years, PARP inhibitors have been widely used in combination with various first-line chemotherapy drugs, targeted drugs and immune checkpoint inhibitors to expand the scope of clinical application. However, the intricate mechanisms underlying the drug resistance to PARP inhibitors, including the restoration of homologous recombination, stabilization of DNA replication forks, overexpression of drug efflux protein, and epigenetic modifications pose great challenges and desirability in the development of novel PARP inhibitors. In this review, we will focus on the mechanism, structure-activity relationship, and multidrug resistance associated with the representative PARP inhibitors. Furthermore, we aim to provide insights into the development prospects and emerging trends to offer guidance for the clinical application and inspiration for the development of novel PARP inhibitors and degraders.

A novel ROR1-targeting antibody-PROTAC conjugate promotes BRD4 degradation for solid tumor treatment

Rationale: Proteolysis Targeting Chimeras (PROTACs) are bifunctional compounds that have been extensively studied for their role in targeted protein degradation (TPD). The capacity to degrade validated or undruggable targets provides PROTACs with significant potency in cancer therapy. However, the clinical application of PROTACs is limited by their poor in vivo potency and unfavorable pharmacokinetic properties. Methods: In this study, a novel degrader-antibody conjugate (DAC) was developed by conjugating the BRD4-degrading PROTAC with the ROR1 (receptor tyrosine kinase-like orphan receptor 1) antibody. The in vitro affinity, internalization efficacy, degradation, and cytotoxic activity of the ROR1 DAC were assessed. The pharmacokinetics, antitumor activity, and acute toxicity of ROR1 DAC were evaluated in mouse models. RNA sequencing (RNA-seq) and immunohistochemistry were performed to analyze the therapeutic efficacy mediated by the combination of ROR1 DAC and anti-mouse programmed cell death protein 1 (αmPD1) mAb. Results: The ROR1 DAC exhibited strong degradation activity and cytotoxicity following antigen binding and internalization. Compared to unconjugated PROTAC, the ROR1 DAC demonstrated improved pharmacokinetics and potent antitumor efficacy in PC3 and MDA-MB-231 xenograft mouse models. Furthermore, enhanced antitumor activity and immune cell infiltration within solid tumors were observed when combined with αmPD-1 mAb in C57BL/6J mice. RNA sequencing revealed that the enhanced immune response associated with the combination treatment is related to tumor microenvironment modulation, including the upregulation of Th1-biased cytokines. Moreover, the ROR1 DAC exhibited a favorable safety profile in an acute toxicity study. Conclusions: These results indicate that the degrader-antibody conjugate is a promising candidate for tumor-specific degradation and effective cancer therapy.

Discovery of a Novel Non-invasive AR PROTAC Degrader for the Topical Treatment of Androgenetic Alopecia

Elevated expression levels and enhanced activity of androgen receptor (AR) proteins are key factors in the development of androgenetic alopecia (AGA). AR proteolysis-targeting chimera (PROTAC) degraders have shown therapeutic potential, but their poor skin permeability requires invasive delivery methods. In this study, we conducted a structure feature analysis to investigate the effects of different linkers and E3 ligands of AR PROTACs on skin retention properties and degradation potency. Among these, compound C6 was discovered with excellent skin retention properties and nanomolar level AR degradation. By degrading AR, C6 regulated the expression levels of downstream paracrine factors associated with AGA. Additionally, after non-invasive topical application, C6 demonstrated excellent skin accumulation and achieved hair regeneration in an AGA mouse model. Overall, the development of non-invasive C6 offers a promising new strategy for AGA treatment and highlights the potential for using PROTACs in treating other skin diseases.

PTGES3 proteolysis using the liposomal peptide-PROTAC approach

BACKGROUND

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide, and the lack of effective biomarkers for early detection leads to poor therapeutic outcomes. Prostaglandin E Synthase 3 (PTGES3) is a putative prognostic marker in many solid tumors; however, its expression and biological functions in HCC have not been determined. The proteolysis-targeting chimera (PROTAC) is an established technology for targeted protein degradation. Compared to the small-molecule PROTAC, the peptide PROTAC (p-PROTAC) utilizes peptides bound to target proteins to mediate the ubiquitination and degradation of undruggable proteins. This study aimed to use the PROTAC technology to develop a PTGES3 degrader liposome complex containing a PTGES3-binding peptide and the E3 ubiquitin ligase ligand pomalidomide for regulating cell function and provide a novel pathway for treating HCC.

RESULTS

In this study, we demonstrated that PTGES3 is highly expressed in HCC at the transcriptional and protein levels; furthermore, PTGES3 was identified as a novel drug target that could potentially treat HCC. Hence, we developed PTGES3-PROTACs by adjusting the ligand ratio to optimize the efficacy of degradation agents. The results revealed that PTGES3-PROTAC effectively degraded PTGES3 protein and strongly weakened the HCC malignant phenotype in vitro and in vivo.

CONCLUSIONS

Our findings revealed that the highly selective PTGES3 proteolysis is a potential therapeutic strategy for HCC, and PTGES3 degraders PTGES3-PROTACs can be developed as safe and effective drugs for HCC treatment.

Exploring a new chapter in traditional Chinese medicine: The potential of Calculus bovis in liver cancer treatment

In the ongoing quest for new treatments in medicine, traditional Chinese medicine offers unique insights and potential. Recently, studies on the ability of Calculus bovis to inhibit M2-type tumour-associated macrophage polarisation by modulating the Wnt/β-catenin signalling pathway to suppress liver cancer have undoubtedly revealed new benefits and hope for this field of research. The purpose of this article is to comment on this study and explore its strengths and weaknesses, thereby providing ideas for the future treatment of liver cancer.

Dynamic Detection of the E3-PROTAC-Target Protein Ternary Complex In Vitro and In Vivo via Bimolecular Fluorescence Complementation

Proteolysis-targeting chimeras (PROTACs) have played an important role in the development of protein-targeted degradation drugs. However, effective tools are urgently required for the further development and validation of PROTACs. We developed a high-potency reporter (AKT-PROTAC-Reporter; APR) for PROTACs that specifically targets AKT. The APR successfully detected the status and levels of the AKT-PROTAC-CRBN ternary complex in vivo and in vitro. The APR is based on a bimolecular fluorescence complementation system, where EGFP and luciferase were used as reporter signals for in vitro and in vivo experiments, respectively, with remarkable success. The absence of E3 ligase ubiquitin recruitment activity in the APR can significantly improve the reporting performance of the APR; however, this results in difficulties in the detection of the degradation efficiency of PROTAC target proteins. Our results show that the APR can sensitively, quickly, and effectively detect the presence of terpolymers. Furthermore, the APR can determine the specificity and degradation efficiency of the PROTAC via a fluorescence signal or bioluminescence signal intensity and can efficiently screen PROTACs for a certain target protein.

Molecular glue degrader for tumor treatment

Targeted Protein Degradation (TPD) represented by Proteolysis-Targeting Chimeras (PROTAC) is the frontier field in the research and development of antitumor therapy, in which oral drug HP518 Receives FDA Proceed Authorization for its IND Application for Prostate Cancer Treatment. Recently, molecular glue, functioning via degradation of the target protein is emerging as a promising modality for the development of therapeutic agents, while exhibits greater advantages over PROTAC, including improved efficiency, resistance-free properties, and the capacity to selectively target "undruggable" proteins. This marks a revolutionary advancement in the landscape of small molecule drugs. Given that molecular glue research is still in its early stage, we summarized the mechanisms of molecular glue, the promising drugs in clinical trials and diverse feasible design strategies for molecular glue therapeutics.

PROTAC delivery in tumor immunotherapy: Where are we and where are we going?

Immunotherapy has emerged as a pioneering therapeutic modality, particularly within the realm of oncology, where Chimeric Antigen Receptor T-cell (CAR-T) therapy has manifested significant efficacy in the treatment of hematological malignancies. Nonetheless, the extension of immunotherapy to solid tumors poses a considerable challenge. This challenge is largely attributed to the intrinsic "cold" characteristics of certain tumors, which are defined by scant T-cell infiltration and a diminished immune response. Additionally, the impediment is exacerbated by the elusive nature of numerous targets within the tumor microenvironment, notably those deemed "undruggable" by small molecule inhibitors. This scenario underscores an acute necessity for the inception of innovative therapeutic strategies aimed at countering the resistance mechanisms underlying immune evasion in cold tumors, thereby amplifying the efficacy of cancer immunotherapy. Among the promising strategies is the deployment of Proteolysis Targeting Chimeras (PROTACs), which facilitate the targeted degradation of proteins. PROTACs present unique advantages and have become indispensable in oncology. However, they concurrently grapple with challenges such as solubility issues, permeability barriers, and the classical Hook effect. Notably, advanced delivery systems have been instrumental in surmounting these obstacles. This review commences with an analysis of the factors contributing to the suboptimal responses to immunotherapy in cold tumors. Subsequently, it delivers a thorough synthesis of immunotherapeutic concepts tailored for these tumors, clarifying the integral role of PROTACs in their management and delineating the trajectory of PROTAC technology from bench-side investigation to clinical utilization, facilitated by drug delivery systems. Ultimately, the review extrapolates the prospective future of this approach, aspiring to present novel insights that could catalyze progress in immunotherapy for the treatment of cold tumors.

Construction of novel magnetic systems for cancer immunotherapy via cancer-immunity cycle circuits

The tumor microenvironment (TME) is enriched with immunosuppressive factors that inhibit the recruitment and activation of dendritic cells (DCs), thereby reducing the efficacy of tumor immunotherapy. To address this challenge, we propose an innovative strategy involving the sequential administration of MCM magnetic nanoparticles carrying PROTAC drugs (MCM/ARV) and M-BMDCs in the TEM. This approach not only replenishes DCs in the TEM, but also increases antigen uptake through the attraction between the magnetic particles and promotes DC activation and antigen presentation, thus continuously enhancing the tumor immune cycle. MCM nanoparticles (magnetic nanoclusters coated with calcium-doped manganese carbonate) efficiently load the tumor-targeting drug PROTAC (ARV-825), enhancing its bioavailability, leading to specific degradation of BRD4 in tumor cells, and releasing a large number of tumor-associated antigens. These antigens were captured by MCM nanoparticles to construct magnetized tumor vaccines. Magnetic M-BMDCs introduced at the tumor site are attracted to these magnetized vaccines, resulting in a significant increase in antigen uptake and activation of DCs, significantly enhancing the tumor immune cycle. This co-administration strategy of magnetized vaccines and magnetized BMDCs provides a unique combination therapy for reversing immunosuppressive TEM and enhancing the efficacy of tumor immunotherapy.

Exploration of the tunability of BRD4 degradation by DCAF16 trans-labelling covalent glues

Chemically induced proximity modalities such as targeted protein degradation (TPD) hold promise for expanding the number of proteins that can be manipulated pharmacologically. However, current TPD strategies are often limited to proteins with preexisting ligands. Molecular glues (e.g. glutarimide ligands for CUL4CRBN), offer the potential to target undruggable proteins. Yet, their rational design is largely unattainable due to the unpredictability of the 'gain-of-function' nature of the glue interaction upon chemical modification of ligands. We recently reported a covalent trans-labelling glue mechanism which we named 'Template-assisted covalent modification', where an electrophile decorated BRD4 inhibitor was effectively delivered to a cysteine residue on DCAF16 due to an electrophile-induced BRD4-DCAF16 interaction. Herein, we report our efforts to evaluate how various electrophilic modifications to the BRD4 binder, JQ1, affect DCAF16 recruitment and subsequent BRD4 degradation efficiency. We discovered a moderate correlation between the electrophile-induced BRD4-DCAF16 ternary complex formation and BRD4 degradation. Moreover, we show that a more solvent-exposed warhead presentation optimally recruits DCAF16 and promotes BRD4 degradation. The diversity of covalent attachments in this class of BRD4 degraders suggests a high tolerance and tunability for the BRD4-DCAF16 interaction. This offers a new avenue for rational glue design by introducing covalent warheads to known binders.

Recent advances in dual PROTACs degrader strategies for disease treatment

Proteolysis-targeting chimeras (PROTACs) is regarded as an emerging therapeutic strategy with unlimited potential because of its mechanism of inducing target protein degradation though harnessing ubiquitin-proteasome system (UPS). Recently, researchers are combining the advantages of PROTACs and dual-targeted drugs to explore some new types of dual PROTACs degraders. The utilization of dual PROTACs not only enhances the efficiency of selective degradation for two or more distinct proteins, but also facilitates synergistic interactions between target proteins to optimize therapeutic efficacy as well as overcome resistance. In this review, we briefly investigate the innovative strategies of dual degraders based on bivalent or trivalent "Y-type" PROTACs in recent years, outline their design principles, degradation effects, and anticancer activities. Moreover, their advantages and limitations compared with traditional PROTACs will be discussed and provide the outlook on the associated challenges. Meaningfully, the development and application of these dual-targeted PROTACs may point out new directions for replacing numerous combination regimens in the future.

PROTAC unleashed: Unveiling the synthetic approaches and potential therapeutic applications

Proteolysis-Targeting Chimeras (PROTACs) are a novel class of bifunctional small molecules that alter protein levels by targeted degradation. This innovative approach uses the ubiquitin-proteasome system to selectively eradicate disease-associated proteins, providing a novel therapeutic strategy for a wide spectrum of diseases. This review delineates detailed synthetic approaches involved in PROTAC building blocks, including the ligand and protein binding parts, linker attached structural components of PROTACs and the actual PROTAC molecules. Furthermore, the recent advancements in PROTAC-mediated degradation of specific oncogenic and other disease-associated proteins, such as those involved in neurodegenerative, antiviral, and autoimmune diseases, were also discussed. Additionally, we described the current landscape of PROTAC clinical trials and highlighted key studies that underscore the translational potential of this emerging therapeutic modality. These findings demonstrate the versatility of PROTACs in modulating the levels of key proteins involved in various severe diseases.

State-of-the-Art Nrf2 Inhibitors: Therapeutic Opportunities in Non-Cancer Diseases

Nuclear factor erythroid 2-related factor (Nrf2) is a cytoprotective transcription factor that induces the transcription of genes responsible for the cell's response to oxidative stress. While Nrf2 activation has led to the development of clinically relevant therapeutics, the oncogenic role of Nrf2 in the proliferation of cancer cells has underscored the complex nature of Nrf2 and the necessity for the development of Nrf2 inhibitors. Although the application of Nrf2 inhibitors appears limited as anticancer agents, recent studies have begun to pinpoint the impairment of autophagy in diseases as a cellular marker that shifts Nrf2 from a protective to a deleterious state. Therefore, the cytoplasmic accumulation of Nrf2 can lead to the accumulation of lipid hydroperoxides and, ultimately, to ferroptosis. However, some studies aimed at elucidating the role of Nrf2 in non-cancer diseases have yielded conflicting results, attributed to differences in approaches used to inhibit or activate Nrf2, as well as variations in in vitro and/or in vivo disease models. Overall, these results highlight the necessity for a deeper evaluation of Nrf2's role in diseases, especially chronic diseases. In this review, we discuss diseases where Nrf2 inhibition holds potential for beneficial therapeutic effects and summarize recently reported Nrf2 inhibitors exploiting medicinal chemistry approaches suitable for targeting transcription factors like Nrf2.

Chemical proteomics accelerates the target discovery of natural products

More than half of the global novel drugs are directly or indirectly derived from natural products (NPs) because of their better selectivity towards proteins. Traditional medicines perform multiple bioactivities through various NPs binding to drug targets, which highlights the opportunities of target discovery for drug development. However, detecting the binding relationship between NPs and targets remains challenging. Chemical proteomics, an interdisciplinary field of chemistry, proteomics, biology, and bioinformatics, has emerged as a potential approach for uncovering drug-target interactions. This review summarizes the principles and characteristics of the current widely applied chemical proteomic technologies, while delving into their latest applications in the target discovery of natural medicine. These endeavours demonstrate the potential of chemical proteomics for target discovery to supply dependable methodologies for the target elucidation of NPs.

Systemic Administration of Neurotransmitter-Derived Lipidoids-PROTACs-DNA Nanocomplex Promotes Tau Clearance and Cognitive Recovery for Alzheimer's Disease Therapy

Alzheimer's disease (AD) poses a significant burden on the economy and healthcare systems worldwide. Although the pathophysiology of AD remains debatable, its progression is strongly correlated with the accumulation of tau aggregates. Therefore, tau clearance from brain lesions can be a promising strategy for AD therapy. To achieve this, the present study combined proteolysis-targeting chimera (PROTAC), a novel protein-degradation technique that mediates degradation of target proteins via the ubiquitin-proteasome system, and a neurotransmitter-derived lipidoid (NT-lipidoid) nanoparticle delivery system with high blood-brain barrier-penetration activity, to generate a novel nanomedicine named NPD. Peptide 1, a cationic tau-targeting PROTAC is loaded onto the positively charged nanoparticles using DNA-intercalation technology. The resulting nanomedicine displayed good encapsulation efficiency, serum stability, drug release profile, and blood-brain barrier-penetration capability. Furthermore, NPD potently induced tau clearance in both cultured neuronal cells and the brains of AD mice. Moreover, intravenous injection of NPD led to a significant improvement in the cognitive function of the AD mice, without any remarkable abnormalities, thereby supporting its clinical development. Collectively, the novel nanomedicine developed in this study may serve as an innovative strategy for AD therapy, since it effectively and specifically induces tau protein clearance in brain lesions, which in turn enhances cognition.

Therapeutic approaches targeting oncogenic proteins in myeloid leukemia: challenges and perspectives

INTRODUCTION

Leukemia is typically categorized into myeloid leukemia and lymphoblastic leukemia based on the origins of leukemic cells. Myeloid leukemia is a group of clonal malignancies characterized by the presence of increased immature myeloid cells in both the bone marrow and peripheral blood. Of note, the aberrant expression of specific proteins or the generation of fusion proteins due to chromosomal abnormalities are well established drivers in various forms of myeloid leukemia. Therefore, these oncoproteins represent promising targets for drug development.

AREAS COVERED

In this review, we comprehensively discussed the pathogenesis of typical leukemia oncoproteins and the current landscape of small molecule drugs targeting these oncogenic proteins. Additionally, we elucidated novel strategies, including proteolysis-targeting chimeras (PROTACs), hyperthermia, and genomic editing, which specifically degrade oncogenic proteins in myeloid malignancies.

EXPERT OPINION

Although small molecule drugs have significantly improved the prognosis of oncoprotein-driven myeloid leukemia patients, drug resistance due to the mutations in oncoproteins is still a great challenge in the clinic. New approaches such as PROTACs, hyperthermia, and genomic editing are considered promising approaches for the treatment of oncoprotein-driven leukemia, especially for drug-resistant mutants.

Fragment-based approaches to discover ligands for tumor-specific E3 ligases

INTRODUCTION

Targeted protein degradation (TPD) has emerged as an innovative therapeutic strategy through selective degradation of specific proteins by harnessing the cellular ubiquitin-proteasome system (UPS), which involves over 600 E3 ubiquitin ligases. Recent proteome profiling reported tumor-specific E3 ligases in human. Development of those tumor-specific E3 ligase ligands would provide a solution for tumor-specific TPD for effective cancer treatment.

AREAS COVERED

This review provides a comprehensive list of E3 ligases found only in specific types of tumor from public databases and highlights examples of their ligands discovered through fragment-based approaches. It details their discovery process and potential applications for precise TPD and effective cancer treatments.

EXPERT OPINION

Current TPD strategies using proteolysis-targeting chimeras (PROTACs) primarily utilize general E3 ligases, such as CRBN and VHL. Since these E3 ligases demonstrate effective protein degradation activity in most human cell types, CRBN and VHL-based PROTACs can exhibit undesired TPD in off-target tissues, which often leads to the side effects. Therefore, developing tumor-specific E3 ligase ligands can be crucial for effective cancer treatments. Fragment-based ligand discovery (FBLD) approaches would accelerate the identification of these tumor-specific E3 ligase ligands and associated PROTACs, thereby advancing the field of targeted cancer therapies.

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.

Crystal structures of DCAF1-PROTAC-WDR5 ternary complexes provide insight into DCAF1 substrate specificity

Proteolysis-targeting chimeras (PROTACs) have been explored for the degradation of drug targets for more than two decades. However, only a handful of E3 ligase substrate receptors have been efficiently used. Downregulation and mutation of these receptors would reduce the effectiveness of such PROTACs. We recently developed potent ligands for DCAF1, a substrate receptor of EDVP and CUL4 E3 ligases. Here, we focus on DCAF1 toward the development of PROTACs for WDR5, a drug target in various cancers. We report four DCAF1-based PROTACs with endogenous and exogenous WDR5 degradation effects and high-resolution crystal structures of the ternary complexes of DCAF1-PROTAC-WDR5. The structures reveal detailed insights into the interaction of DCAF1 with various WDR5-PROTACs, indicating a significant role of DCAF1 loops in providing needed surface plasticity, and reflecting the mechanism by which DCAF1 functions as a substrate receptor for E3 ligases with diverse sets of substrates.

The Role of HDAC6 in Glioblastoma Multiforme: A New Avenue to Therapeutic Interventions?

Despite the great advances in basic research results, glioblastoma multiforme (GBM) still remains an incurable tumour. To date, a GBM diagnosis is a death sentence within 15-18 months, due to the high recurrence rate and resistance to conventional radio- and chemotherapy approaches. The effort the scientific community is lavishing on the never-ending battle against GBM is reflected by the huge number of clinical trials launched, about 2003 on 10 September 2024. However, we are still far from both an in-depth comprehension of the biological and molecular processes leading to GBM onset and progression and, importantly, a cure. GBM is provided with high intratumoral heterogeneity, immunosuppressive capacity, and infiltrative ability due to neoangiogenesis. These features impact both tumour aggressiveness and therapeutic vulnerability, which is further limited by the presence in the tumour core of niches of glioblastoma stem cells (GSCs) that are responsible for the relapse of this brain neoplasm. Epigenetic alterations may both drive and develop along GBM progression and also rely on changes in the expression of the genes encoding histone-modifying enzymes, including histone deacetylases (HDACs). Among them, HDAC6-a cytoplasmic HDAC-has recently gained attention because of its role in modulating several biological aspects of GBM, including DNA repair ability, massive growth, radio- and chemoresistance, and de-differentiation through primary cilia disruption. In this review article, the available information related to HDAC6 function in GBM will be presented, with the aim of proposing its inhibition as a valuable therapeutic route for this deadly brain tumour.

KLHL20 and its role in cell homeostasis: A new perspective and therapeutic potential

Ubiquitin ligases are proteins with the ability to trigger non-degradative signaling or proteasomal destruction by attracting substrates and facilitating ubiquitin transfer onto target proteins. Over the years, there has been a continuous discovery of new ubiquitin ligases, and Kelch-like protein 20 (KLHL20) is one of the most recent discoveries that have several biological roles which include its role in ubiquitin ligase activities. KLHL20 binds as a substrate component of ubiquitin ligase Cullin3 (Cul3). Several substrates for ubiquitin ligases (KLHL20 based) have been reported, these include Unc-51 Like Autophagy Activating Kinase 1 (ULK1), promyelocytic leukemia (PML), and Death Associated Protein Kinase 1 (DAPK1). KLHL20 shows multiple cell functions linked to several human diseases through ubiquitination of these substrates. Current literature shows that KLHL20 ubiquitin ligase regulates malignancies in humans and also suggests how important it is to develop regulating agents for tumour-suppressive KLHL20 to prevent tumourigenesis, Recent research has highlighted its potential therapeutic implications in several areas. In oncology, KLHL20's regulatory role in protein degradation pathways suggests that its targeting could offer novel strategies for cancer treatment by modulating the stability of proteins involved in tumour growth and survival. In neurodegenerative diseases, KLHL20's function in maintaining protein homeostasis positions it as a potential target for therapies aimed at managing protein aggregation and cellular stress. Here, we review the functions of KLHL20 during the carcinogenesis process, looking at its role in cancer progression, and regulation of ubiquitination events mediated by KLHL20 in human cancers, as well as its potential therapeutic interventions.

Dysregulation of deubiquitinases in gastric cancer progression

Gastric cancer (GC), characterized by a high incidence rate, poses significant clinical challenges owing to its poor prognosis despite advancements in diagnostic and therapeutic approaches. Therefore, a comprehensive understanding of the molecular mechanisms driving GC progression is crucial for identifying predictive markers and defining treatment targets. Deubiquitinating enzymes (DUBs), also called deubiquitinases, function as reverse transcriptases within the ubiquitin-proteasome system to counteract protein degradation. Recent findings suggest that DUB dysregulation could be a crucial factor in GC pathogenesis. In this review, we examined recent research findings on DUBs in the context of GC, elucidating their molecular characteristics, categorizations, and roles while also exploring the potential mechanisms underlying their dysregulation in GC. Furthermore, we assessed the therapeutic efficacy of DUB inhibitors in treating malignancies and evaluated the prevalence of aberrant DUB expression in GC.

DNA Nanotechnology for Application in Targeted Protein Degradation

DNA is a kind of flexible and versatile biomaterial for constructing nanostructures and nanodevices. Due to high biocompatibility and programmability and easy modification and fabrication, DNA nanotechnology has emerged as a powerful tool for application in intracellular targeted protein degradation. In this review, we summarize the recent advances in the design and mechanism of targeted protein degradation technologies such as protein hydrolysis targeted chimeras, lysosomal targeted chimeras, and autophagy based protein degradation. Subsequently, we introduce the DNA nanotechnologies of DNA cascade circuits, DNA nanostructures, and dynamic machines. Moreover, we present the latest developments in DNA nanotechnologies in targeted protein degradation. Finally, the vision and challenges are discussed.

A comprehensive review of new small molecule drugs approved by the FDA in 2022: Advance and prospect

In 2022, the U.S. Food and Drug Administration approved a total of 16 marketing applications for small molecule drugs, which not only provided dominant scaffolds but also introduced novel mechanisms of action and clinical indications. The successful cases provide valuable information for optimizing efficacy and enhancing pharmacokinetic properties through strategies like macrocyclization, bioequivalent group utilization, prodrug synthesis, and conformation restriction. Therefore, gaining an in-depth understanding of the design principles and strategies underlying these drugs will greatly facilitate the development of new therapeutic agents. This review focuses on the research and development process of these newly approved small molecule drugs including drug design, structural modification, and improvement of pharmacokinetic properties to inspire future research in this field.

Recent breakthroughs in innovative elements, multidimensional enhancements, derived technologies, and novel applications of PROTACs

Proteolysis Targeting Chimera (PROTAC) is an emerging and evolving technology based on targeted protein degradation (TPD). Small molecule PROTACs have shown great efficacy in degrading disease-specific proteins in preclinical and clinical studies, but also showed various limitations. In recent years, new technologies and advances in TPD have provided additional optimized strategies based on conventional PROTACs that can overcome the shortcomings of conventional PROTACs in terms of undruggable targets, bioavailability, tissue-specificity, spatiotemporal control, and degradation scope. In addition, some designs of special targeting chimeras and applications based on multidisciplinary science have shed light on novel therapeutic modalities and drug design. However, each improvement has its own advantages, disadvantages and application conditions. In this review, we summarize the exploration of PROTAC elements, depict a landscape of improvements and derived concepts of PROTACs, and expect to provide perspectives for technological innovations, combinations and applications in future targeting chimera design.

Targeting the MET gene: unveiling therapeutic opportunities in immunotherapy within the tumor immune microenvironment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) represents the most prevalent histological subtype of lung cancer. Within this disease, the MET gene emerges as a critical therapeutic target, exhibiting various forms of dysregulation. Although MET tyrosine kinase inhibitors, HGF/c-MET targeting antibodies, and antibody-drug conjugates constitute the primary treatment modalities for patients with MET-altered NSCLC, numerous questions remain regarding their optimal application. The advent of immunotherapy holds promise for enhancing therapeutic outcomes in patients with MET-altered NSCLC. MET mutations can reshape the tumor immune microenvironment of NSCLC by reducing tumor immunogenicity, inducing exhaustion in immune-activated cells, and promoting immune evasion, which are crucial for modulating treatment responses. Furthermore, we emphasize the promising synergy of immunotherapy with emerging treatments and the challenges and opportunities in refining these approaches to improve patient outcomes.

PROTAC technology: From drug development to probe technology for target deconvolution

Drug development remains a critical focus within the global pharmaceutical industry. To date, more than 80 % of disease targets are considered difficult to target. The emergence of PROTAC technology has, to some extent, alleviated this challenge. Since introduction, PROTAC technology has evolved through the peptide E3 ligase ligand phase and the small molecule E3 ligase ligand phase. Currently, multiple PROTAC molecules are in the clinical research phase, showing promising potential for addressing drug resistance, disease recurrence, and intractable targets. Target deconvolution is a crucial step in the drug discovery and development process. Due to the exceptional targeting ability and specificity of PROTAC, it is widely used and promoted as an innovative technology for discovering new drug targets, leading to significant breakthroughs. The use of PROTAC probe requires only a catalytic dose and weak interaction with the target protein to achieve target degradation. Thus, it offers substantial advantages over traditional probes, particularly in identifying new targets that are low-abundance or difficult to target. This review provides a comprehensive overview of the advancements made by PROTAC technology in drug development and drug target discovery, while also systematically reviewing the workflow of PROTAC probe. With the ongoing development of PROTAC technology, PROTAC probe is poised to become a key research area in future drug target deconvolution.

The role of ubiquitination in health and disease

Ubiquitination is an enzymatic process characterized by the covalent attachment of ubiquitin to target proteins, thereby modulating their degradation, transportation, and signal transduction. By precisely regulating protein quality and quantity, ubiquitination is essential for maintaining protein homeostasis, DNA repair, cell cycle regulation, and immune responses. Nevertheless, the diversity of ubiquitin enzymes and their extensive involvement in numerous biological processes contribute to the complexity and variety of diseases resulting from their dysregulation. The ubiquitination process relies on a sophisticated enzymatic system, ubiquitin domains, and ubiquitin receptors, which collectively impart versatility to the ubiquitination pathway. The widespread presence of ubiquitin highlights its potential to induce pathological conditions. Ubiquitinated proteins are predominantly degraded through the proteasomal system, which also plays a key role in regulating protein localization and transport, as well as involvement in inflammatory pathways. This review systematically delineates the roles of ubiquitination in maintaining protein homeostasis, DNA repair, genomic stability, cell cycle regulation, cellular proliferation, and immune and inflammatory responses. Furthermore, the mechanisms by which ubiquitination is implicated in various pathologies, alongside current modulators of ubiquitination are discussed. Enhancing our comprehension of ubiquitination aims to provide novel insights into diseases involving ubiquitination and to propose innovative therapeutic strategies for clinical conditions.

Lysosome-targeting chimeras containing an endocytic signaling motif trigger endocytosis and lysosomal degradation of cell-surface proteins

Lysosome-targeting degradation technologies have emerged as a promising therapeutic strategy for the selective depletion of target extracellular and cell-surface proteins by harnessing a cell-surface effector protein such as lysosome-targeting receptors (LTRs) or transmembrane E3 ligases that direct lysosomal degradation. We recently developed a lysosome-targeting degradation platform termed signal-mediated lysosome-targeting chimeras (SignalTACs) that functions independently of an LTR or E3 ligase; these are engineered fusion proteins comprising a target binder, a cell-penetrating peptide (CPP), and a lysosomal sorting signal motif (P1). Herein, we present the next-generation SignalTACs containing a single endocytic signal that bypasses the need for a CPP. We demonstrate that the fusion with a 10-amino acid endocytic signaling peptide (P3) derived from the cation-independent mannose-6-phosphate receptor (CI-M6PR) induces robust internalization and lysosomal degradation of the target protein. The P3-based SignalTAC exhibited enhanced antitumor efficacy compared to the parent antibody. We envision that the fusion of the endocytic signaling peptide P3 to a target binder may allow the construction of an effective degrader for membrane-associated targets. Furthermore, mechanistic studies identified different drivers for the activities of the P3- and P1-based SignalTACs, which is expected to provide crucial insights toward the harnessing of the intrinsic signaling pathways to direct protein trafficking and degradation.

Characteristic roadmap of linker governs the rational design of PROTACs

Proteolysis targeting chimera (PROTAC) technology represents a groundbreaking development in drug discovery, leveraging the ubiquitin‒proteasome system to specifically degrade proteins responsible for the disease. PROTAC is characterized by its unique heterobifunctional structure, which comprises two functional domains connected by a linker. The linker plays a pivotal role in determining PROTAC's biodegradative efficacy. Advanced and rationally designed functional linkers for PROTAC are under development. Nonetheless, the correlation between linker characteristics and PROTAC efficacy remains under-investigated. Consequently, this study will present a multidisciplinary analysis of PROTAC linkers and their impact on efficacy, thereby guiding the rational design of linkers. We will primarily discuss the structural types and characteristics of PROTAC linkers, and the optimization strategies used for their rational design. Furthermore, we will discuss how factors like linker length, group type, flexibility, and linkage site affect the biodegradation efficiency of PROTACs. We believe that this work will contribute towards the advancement of rational linker design in the PROTAC research area.

Proteolysis-targeting drug delivery system (ProDDS): integrating targeted protein degradation concepts into formulation design

Targeted protein degradation (TPD) has emerged as a revolutionary paradigm in drug discovery and development, offering a promising avenue to tackle challenging therapeutic targets. Unlike traditional drug discovery approaches that focus on inhibiting protein function, TPD aims to eliminate proteins of interest (POIs) using modular chimeric structures. This is achieved through the utilization of proteolysis-targeting chimeras (PROTACs), which redirect POIs to E3 ubiquitin ligases, rendering them for degradation by the cellular ubiquitin-proteasome system (UPS). Additionally, other TPD technologies such as lysosome-targeting chimeras (LYTACs) and autophagy-based protein degraders facilitate the transportation of proteins to  endo-lysosomal or autophagy-lysosomal pathways for degradation, respectively. Despite significant growth in preclinical TPD research, many chimeras fail to progress beyond this stage in the drug development. Various factors contribute to the limited success of TPD agents, including a significant hurdle of inadequate delivery to the target site. Integrating TPD into delivery platforms could surmount the challenges of in vivo applications of TPD strategies by reshaping their pharmacokinetics and pharmacodynamic profiles. These proteolysis-targeting drug delivery systems (ProDDSs) exhibit superior delivery performance, enhanced targetability, and reduced off-tissue side effects. In this review, we will survey the latest progress in TPD-inspired drug delivery systems, highlight the importance of introducing delivery ideas or technologies to the development of protein degraders, outline design principles of protein degrader-inspired delivery systems, discuss the current challenges, and provide an outlook on future opportunities in this field.

Treating ICB-resistant cancer by inhibiting PD-L1 via DHHC3 degradation induced by cell penetrating peptide-induced chimera conjugates

The current selection of ligands for both proteins of interest (POI) and E3 ubiquitin ligase significantly restricts the scope of targeted protein degradation (TPD) technologies. This study introduces cell-penetrating peptide-induced chimera conjugates (cp-PCCs) targeting the DHHC3 enzyme involved in PD-L1 palmitoylation. This approach disrupts PD-L1's immunosuppressive function, enhancing anti-tumor immunity. We developed cp-PCCs to degrade DHHC3, directly linking DHHC3-mediated PD-L1 palmitoylation to PD-L1 stability on tumor cells. Our research utilized both in vitro assays and in vivo experiments in immune checkpoint blockade-resistant mouse models. We focused on a CRBN-based cp-PCC named PCC16, which demonstrated a DC50 of 102 nmol for DHHC3 degradation and significantly reduced PD-L1 levels. In resistant models, PCC16 not only robustly downregulated PD-L1 but also exhibited substantial anti-tumor activity in vivo without significant toxicity. This outperformed traditional inhibitors, showcasing the potential of cp-PCC technology to bypass current PROTAC limitations. Our findings suggest that cp-PCCs offer a promising method for targeting PD-L1 through DHHC3 inhibition and support their continued exploration as a versatile tool in cancer immunotherapy, especially for tumors resistant to standard treatments.

Development of novel antivrial agents that induce the degradation of the main protease of human-infecting coronaviruses

The family of human-infecting coronaviruses (HCoVs) poses a serious threat to global health and includes several highly pathogenic strains that cause severe respiratory illnesses. It is essential that we develop effective broad-spectrum anti-HCoV agents to prepare for future outbreaks. In this study, we used PROteolysis TArgeting Chimera (PROTAC) technology focused on degradation of the HCoV main protease (Mpro), a conserved enzyme essential for viral replication and pathogenicity. By adapting the Mpro inhibitor GC376, we produced two novel PROTACs, P2 and P3, which showed relatively broad-spectrum activity against the human-infecting CoVs HCoV-229E, HCoV-OC43, and SARS-CoV-2. The concentrations of these PROTACs that reduced virus replication by 50 % ranged from 0.71 to 4.6 μM, and neither showed cytotoxicity at 100 μM. Furthermore, mechanistic binding studies demonstrated that P2 and P3 effectively targeted HCoV-229E, HCoV-OC43, and SARS-CoV-2 by degrading Mpro within cells in vitro. This study highlights the potential of PROTAC technology in the development of broad-spectrum anti-HCoVs agents, presenting a novel approach for dealing with future viral outbreaks, particularly those stemming from CoVs.

Discovery of a potent CDKs/FLT3 PROTAC with enhanced differentiation and proliferation inhibition for AML

AML is an aggressive malignancy of immature myeloid progenitor cells. Discovering effective treatments for AML through cell differentiation and anti-proliferation remains a significant challenge. Building on previous studies on CDK2 PROTACs with differentiation-inducing properties, this research aims to enhance CDKs degradation through structural optimization to facilitate the differentiation and inhibit the proliferation of AML cells. Compound C3, featuring a 4-methylpiperidine ring linker, effectively degraded CDK2 with a DC50 value of 18.73 ± 10.78 nM, and stimulated 72.77 ± 3.51 % cell differentiation at 6.25 nM in HL-60 cells. Moreover, C3 exhibited potent anti-proliferative activity against various AML cell types. Degradation selectivity analysis indicated that C3 could be endowed with efficient degradation of CDK2/4/6/9 and FLT3, especially FLT3-ITD in MV4-11 cells. These findings propose that C3 combined targeting CDK2/4/6/9 and FLT3 with enhanced differentiation and proliferation inhibition, which holds promise as a potential treatment for AML.

Recent progress in the development of hypoxia-inducible factor 2α (HIF-2α) modulators: Inhibitors, agonists, and degraders (2009-2024)

Hypoxia-inducible factor 2α (HIF-2α) is a critical transcription factor that regulates cellular responses under hypoxic conditions. In situations of insufficient oxygen supply or patients with Von Hippel-Lindau (VHL) mutations, HIF-2α accumulates and forms a heterodimeric complex with aryl hydrocarbon receptor nuclear translocator (ARNT, or HIF-β). This complex further binds to coactivator p300 and interacts with hypoxia response elements (HREs) on the DNA of downstream target genes, regulating the transcription of a variety of genes (e.g. VEGFA, CCND1, CXCR4, SLC2A1, etc) involved in various processes like angiogenesis, mitochondrial metabolism, cell proliferation, and metastasis. Targeting HIF-2α holds great promise for effectively addressing solid tumors associated with aberrant oxygen-sensing pathways and hypoxia mechanisms, offering broad application prospects. In this review, we provide an overview of recent advancements (2009-2024) in HIF-2α modulators such as inhibitors, agonists, and degraders for cancer therapy. Additionally, we discuss in detail the challenges and future directions regarding HIF-2α modulators.

Liver-targeting chimeras as a potential modality for the treatment of liver diseases

Liver diseases pose significant challenges to global public health. In the realm of drug discovery and development, overcoming 'on-target off-tissue' effects remains a substantial barrier for various diseases. In this study, we have pioneered a Liver-Targeting Chimera (LIVTAC) approach using a proteolysis-targeting chimera (PROTAC) molecule coupled to the liver-specific asialoglycoprotein receptor (ASGPR) through an innovative linker attachment strategy for the precise induction of target protein degradation within the liver. As a proof-of-concept study, we designed XZ1606, a mammalian bromodomain and extra-terminal domain (BET)-targeting LIVTAC agent, which not only demonstrated enduring tumor suppression (over 2 months) in combination with sorafenib but also an improved safety profile, notably ameliorating the incidence of thrombocytopenia, a common and severe on-target dose-limiting toxic effect associated with conventional BET inhibitors. These encouraging results highlight the potential of LIVTAC as a versatile platform for addressing a broad spectrum of liver diseases.

M1/M2 macrophage-targeted nanotechnology and PROTAC for the treatment of atherosclerosis

Macrophages play key roles in atherosclerosis progression, and an imbalance in M1/M2 macrophages leads to unstable plaques; therefore, M1/M2 macrophage polarization-targeted treatments may serve as a new approach in the treatment of atherosclerosis. At present, there is little research on M1/M2 macrophage polarization-targeted nanotechnology. Proteolysis-targeting chimera (PROTAC) technology, a targeted protein degradation technology, mediates the degradation of target proteins and has been widely promoted in preclinical and clinical applications as a novel therapeutic modality. This review summarizes the recent studies on M1/M2 macrophage polarization-targeted nanotechnology, focusing on the mechanism and advantages of PROTACs in M1/M2 macrophage polarization as a new approach for the treatment of atherosclerosis.

The cellular-centered view of hypoxia tumor microenvironment: Molecular mechanisms and therapeutic interventions

Cancer is a profoundly dynamic, heterogeneous and aggressive systemic ailment, with a coordinated evolution of various types of tumor niches. Hypoxia plays an indispensable role in the tumor micro-ecosystem, drastically enhancing the plasticity of cancer cells, fibroblasts and immune cells and orchestrating intercellular communication. Hypoxia-induced signals, particularly hypoxia-inducible factor-1α (HIF-1α), drive the reprogramming of genetic, transcriptional, and proteomic profiles. This leads to a spectrum of interconnected processes, including augmented survival of cancer cells, evasion of immune surveillance, metabolic reprogramming, remodeling of the extracellular matrix, and the development of resistance to conventional therapeutic modalities like radiotherapy and chemotherapy. Here, we summarize the latest research on the multifaceted effects of hypoxia, where a multitude of cellular and non-cellular elements crosstalk with each other and co-evolve in a synergistic manner. Additionally, we investigate therapeutic approaches targeting hypoxic niche, encompassing hypoxia-activated prodrugs, HIF inhibitors, nanomedicines, and combination therapies. Finally, we discuss some of the issues to be addressed and highlight the potential of emerging technologies in the treatment of cancer.

Versatile Split-and-Mix Liposome PROTAC Platform for Efficient Degradation of Target Protein In Vivo

PROTAC (Proteolysis TArgeting Chimeras) is a promising therapeutic approach for targeted protein degradation that recruits an E3 ubiquitin ligase to a specific protein of interest (POI), leading to its degradation by the proteasome. Recently, we developed a novel split-and-mix PROTAC system based on liposome self-assembly (LipoSM-PROTAC) which could achieve target protein degradation at comparable concentrations comparable to small molecules. In this study, we expanded protein targets based on the LipoSM-PROTAC platform and further examined its therapeutic effects in vivo. Notably, this platform could efficiently degrade the protein level of MEK1/2 in A375 cells or Alk in NCI-H2228 cells and display obvious tumor inhibition (60-70% inhibition rate) with negligible toxicity. This study further proved the LipoSM-PROTAC's application potentials.