Induced protein degradation: an emerging drug discovery paradigm

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.

Liquid Chromatography Combined With Tandem Mass Spectrometry for the Pharmacokinetic and Metabolism Studies of PROTAC ARV-471 in Rats

Proteolysis targeting chimera (PROTAC) is emerging as a promising medicinal modality, which has aroused widespread interest among the field of pharmaceutical manufacturing in the recent years. ARV-471 is an orally active PROTAC estrogen receptor degrader against breast cancer, which leads to the ubiquitylation and subsequent degradation of estrogen receptors via the proteasome. In this study, we developed a highly sensitive liquid chromatography tandem mass spectrometry method (LLOQ = 0.5 ng/mL) for the measurement of ARV-471 in rat plasma. The acetonitrile precipitated sample was separated on ACQUITY BEH C18 column using acetonitrile-0.1% formic acid as mobile phased with gradient elution. Multiple reactions monitoring in positive ESI mode was employed for the quantification of ARV-471 (m/z 724.4 → 396.2). The assay showed good linearity over the concentration range of 0.5-1000 ng/mL with correlation coefficient > 0.996. The assay was validated according to FDA guidance, and all the validation parameters were within the predefined acceptance criteria. After validation, the assay was applied to the pharmacokinetic study of ARV-471 in rats. Additionally, the metabolites in rat plasma were identified using liquid chromatography-high resolution mass spectrometry. Four metabolites were identified and characterized. Hydrolysis, glucuronidation and deamination were the main metabolic pathways of ARV-471 in rats.

Revolutionizing lung cancer treatment: Introducing PROTAC therapy as a novel paradigm in targeted therapeutics

This comprehensive review explores the transformative potential of PROTAC (Proteolysis-Targeting Chimeras) therapy as a groundbreaking approach in the landscape of lung cancer treatment. The introduction provides a succinct overview of current challenges in lung cancer treatment, emphasizing the significance of targeted therapies. Focusing on PROTAC therapy, the article elucidates its mechanism of action, comparing it with traditional targeted therapies and highlighting the key components and design principles of PROTAC molecules. In the context of lung cancer, the review meticulously summarizes preclinical evidence, emphasizing efficacy and specificity gleaned from studies evaluating PROTAC therapy. It delves into the implications of this preclinical data, discussing potential advantages over existing targeted therapies. An update on ongoing clinical trials involving PROTAC therapy for lung cancer offers a snapshot of the current progress, with a summary of key outcomes and advancements in early-phase trials. The mechanistic insights into PROTAC therapy's impact on lung cancer cells are explored, alongside a discussion on potential biomarkers for patient stratification and response prediction. The influence of tumor heterogeneity on PROTAC therapy outcomes is also addressed. Safety and tolerability assessments, encompassing preclinical and clinical studies, are comprehensively evaluated, including a comparative analysis with traditional targeted therapies and strategies to mitigate side effects. Looking forward, the article discusses the future perspectives of PROTAC therapy in lung cancer treatment and addresses ongoing challenges, providing a nuanced exploration of potential combination therapies and synergistic approaches. In conclusion, the review summarizes key findings and insights, underscoring the tremendous potential of PROTAC therapy as a promising and innovative avenue in pursuing more effective lung cancer treatments.

Nanomaterial-enabled metabolic reprogramming strategies for boosting antitumor immunity

Immunotherapy has become a crucial strategy in cancer treatment, but its effectiveness is often constrained. Most cancer immunotherapies focus on stimulating T-cell-mediated immunity by driving the cancer-immunity cycle, which includes tumor antigen release, antigen presentation, T cell activation, infiltration, and tumor cell killing. However, metabolism reprogramming in the tumor microenvironment (TME) supports the viability of cancer cells and inhibits the function of immune cells within this cycle, presenting clinical challenges. The distinct metabolic needs of tumor cells and immune cells require precise and selective metabolic interventions to maximize therapeutic outcomes while minimizing adverse effects. Recent advances in nanotherapeutics offer a promising approach to target tumor metabolism reprogramming and enhance the cancer-immunity cycle through tailored metabolic modulation. In this review, we explore cutting-edge nanomaterial strategies for modulating tumor metabolism to improve therapeutic outcomes. We review the design principles of nanoplatforms for immunometabolic modulation, key metabolic pathways and their regulation, recent advances in targeting these pathways for the cancer-immunity cycle enhancement, and future prospects for next-generation metabolic nanomodulators in cancer immunotherapy. We expect that emerging immunometabolic modulatory nanotechnology will establish a new frontier in cancer immunotherapy in the near future.

MicroRNA-Triggered Programmable DNA-Encoded Pre-PROTACs for Cell-Selective and Controlled Protein Degradation

Proteolysis-targeting chimeras (PROTACs) have accelerated drug development; however, some challenges still exist owing to their lack of tumor selectivity and on-demand protein degradation. Here, we developed a miRNA-initiated assembled pre-PROTAC (miRiaTAC) platform that enables the on-demand activation and termination of target degradation in a cell type-specific manner. Using miRNA-21 as a model, we engineered DNA hairpins labeled with JQ-1 and pomalidomide and facilitated the modular assembly of DNA-encoded pre-PROTACs through a hybridization chain reaction. This configuration promoted the selective polyubiquitination and degradation of BRD4 upon miR-21 initiation, highlighting significant tumor selectivity and minimal systemic toxicity. Furthermore, the platform incorporates photolabile groups, enabling the precise optical control of pre-PROTACs during DNA assembly/disassembly, mitigating the risk of excessive protein degradation. Additionally, by introducing a secondary ligand targeting CDK6, these pre-PROTACs were used as a modular scaffold for the programmable assembly of active miRiaTACs containing two different warheads in exact stoichiometry, enabling orthogonal multitarget degradation. The integration of near-infrared light-mediated photodynamic therapy through an upconversion nanosystem further enhanced the efficacy of the platform with potent in vivo anticancer activity. We anticipate that miRiaTAC represents a significant intersection between dynamic DNA nanotechnology and PROTAC, potentially expanding the versatility of PROTAC toolkit for cancer therapy.

Strategy and Design of In Situ Activated Protein Hydrolysis Targeted Chimeras

Protein hydrolysis targeted chimeras (PROTACs) represent a different therapeutic approach, particularly relevant for overcoming challenges associated with traditional small molecule inhibitors. These challenges include targeting difficult proteins that are often deemed "undruggable" and addressing issues of acquired resistance. PROTACs employ the body's own E3 ubiquitin ligases to induce the degradation of specific proteins of interest (POIs) through the ubiquitin-proteasome pathway. This process is cyclical, allowing for broad applicability, potent protein degradation, and selective targeting. Despite their effectiveness, PROTACs can inadvertently target and degrade nonspecific proteins, potentially resulting in significant side effects and off-target toxicity. To address this concern, researchers have created stimuli-activated PROTACs that enhance targeted protein degradation while minimizing potential harm to healthy cells. These advanced PROTACs aim to improve the precision of degradation in both time and space. This article reviews the strategies for in situ activated PROTACs, highlighting key compounds and research advancements associated with various mechanisms of action. The insights presented here aim to guide further exploration in the field of activated PROTACs.

Discovery of a Selective and Orally Bioavailable RET Degrader with Effectiveness in Various Mutations

The rearranged during transfection (RET) mutation such as the G810C mutation has significantly restricted the clinical application of selective RET inhibitors in the treatment of RET-driven cancers. This study designed and evaluated RET proteolysis targeting chimeras (PROTACs) based on selpercatinib (LOXO-292), identifying RD-23 as a potent and selective RET PROTAC. RD-23 effectively inhibited the proliferation of BaF3 cells with various RET mutations, showing IC50 values of 2.4 to 6.5 nM. It selectively induced degradation of the RETG810C mutation via the ubiquitin-proteasome system, with a DC50 (concentration causing 50% of protein degradation) value of 11.7 nM. Additionally, RD-23 exhibited oral bioavailability and superior antitumor effects compared to LOXO-292 in a Ba/F3-KIF5B-RETG810C xenograft mouse model. These results suggested that RD-23 is a promising candidate for treating RET-driven cancers.

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.

A prospective therapeutic strategy: GPX4-targeted ferroptosis mediators

As a crucial regulator of oxidative homeostasis, seleno-protein glutathione peroxidase 4 (GPX4) represents the primary defense system against ferroptosis, making it a promising target with important clinical application prospects. From the discovery of covalent and allosteric sites in GPX4, substantial advancements in GPX4-targeted small molecules have been made through diverse discovery and design strategies in recent years. Moreover, as an emerging hotspot in drug development, seleno-organic compounds can functionally mimic GPX4 to reduce hydroperoxides. To facilitate the further development of selective ferroptosis mediators as potential pharmaceutical agents, this review comprehensively covers all GPX4-targeted small molecules, including inhibitors, degraders, and activators. In addition, seleno-organic compounds as GPX mimics are also included. We also provide perspectives regarding challenges and future research directions in this field.

Design and optimization strategies of PROTACs and its Application, Comparisons to other targeted protein degradation for multiple oncology therapies

Recent years have witnessed notable breakthroughs in the field of biotherapeutics. Proteolysis Targeting Chimeras (PROTACs) are novel molecules which used to degrade particular proteins despite the blockage by small drug molecules, which leads to a predicted therapeutic activity. This is a unique finding, especially at the cellular level targets degradations. Clinical trials and studies on PROTACs are in progress for oncology indications for demonstration of high potency and activity. PROTAC molecules are having excellent tissue distribution properties and their capacity to mutate the proteins and target overexpressed. This concept has attained wide attention from modern researchers in oncological drug discovery with particular physical qualities not offered by other therapeutic approaches. The modular nature of the PROTACs enables their methodical optimization and logical design. A thorough review was conducted in order to delve deeper into the subject and gain a better understanding of its development, computational supports, important factors for the optimization of developed PROTAC candidates, pharmacokinetic and pharmacodynamic (PK-PD) aspects, safety risks such as the degradation of undesired proteins, and other PROTAC-related issues and their target immunotherapeutic response. Furthermore discussed about the benefits, possible challenges, viewpoints, comparison with other targeted protein degraders (LYTACs, AUTOTACs) and the most current research results of PROTACs technology in multiple oncology therapies. Abbreviations: PROTACs, Proteolysis Targeting Chimeras; PK, Pharmacokinetic; PD, Pharmacodynamic; MetAP-2, (methionine aminopeptidase 2); BCL6, B-cell lymphoma 6; GCN5, General Control Nonderepressible 5; BKT, Bruton's tyrosine kinase; BET, Bromodomain and extra-terminal; AR, Androgen or Androgen receptor; ER, Estrogen or Estrogen receptor; FDA, Food and Drug Administration; mCRPC, Metastatic castration-resistant prostate cancer; STAT3, Signal Transducer and Activator of Transcription 3; FAK, Focal adhesion kinase; POI, Protein of interest; PEG, Polyethylene glycol; UPS, Ubiquitin-Proteasome System; VHL, Von Hippel-Lindau; CRBN, Cereblon; MDM2, Mouse Double Minute 2 homologue; cIAP, Cellular Inhibitor of Apoptosis; RNF, Ring Finger Protein; BRD, Bromodomain; CDK, Cyclin-dependent kinase; PAMPA, Parallel Artificial Membrane Permeability studies; BRET, Bioluminescence Resonance Energy Transfer; MCL, Mantle cell lymphoma; MCL-1, Myeloid Cell Leukemia 1; BCL-XL, B-cell lymphoma extra-large; TRK, Tropomyosin Receptor Kinase; RTKs, Transmembrane Receptor Tyrosine Kinase; NTRK, Neurotrophic Tyrosine Receptor Kinase; DHT, Dihydrotestosterone; EGFR, Epidermal Growth Factor Receptor; EGFR-TKIs, EGFR tyrosine kinase inhibitors; NSCLC, non-small cell lung cancer; BCR, B-cell receptor; CML, Chronic myelogenous leukemia; TKI, Tyrosine kinase inhibitors; MoA, Mechanism of action; TPD, Targetted protein degraders; LYTACs, Lysosome targeting chimeras; ASGPR, Asialoglycoprotein receptor; AUTOTACs, Autophagy-Targeting Chimeras; ATTECs, Autophagy-tethering compounds; CRISPR-Cas9, Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated protein 9; TALEN, Transcription Activator-Like Effector Nuclease; ZFN, Zinc Finger Nuclease.

Development of PROTACs targeting estrogen receptor: an emerging technique for combating endocrine resistance

Despite the success of endocrine therapies in treating ER-positive breast cancer, the development of resistance remains a significant challenge. Estrogen receptor targeting proteolysis-targeting chimeras (ER PROTACs) offer a unique approach by harnessing the ubiquitin-proteasome system to degrade ER, potentially bypassing resistance mechanisms. In this review, we present the drug design, efficacy and early clinical trials of these ER PROTACs. This review underscores the academic and industrial opportunities presented by this emerging technology, as well as the challenges that must be addressed to translate these findings into effective clinical therapies.

Modulating Phosphorylation by Proximity-Inducing Modalities for Cancer Therapy

Abnormal phosphorylation of proteins can lead to various diseases, particularly cancer. Therefore, the development of small molecules for precise regulation of protein phosphorylation holds great potential for drug design. While the traditional kinase/phosphatase small-molecule modulators have shown some success, achieving precise phosphorylation regulation has proven to be challenging. The emergence of heterobifunctional molecules, such as phosphorylation-inducing chimeric small molecules (PHICSs) and phosphatase recruiting chimeras (PHORCs), with proximity-inducing modalities is expected to lead to a breakthrough by specifically recruiting kinase or phosphatase to the protein of interest. Herein, we summarize the drug targets with aberrant phosphorylation in cancer and underscore the potential of correcting phosphorylation in cancer therapy. Through reported cases of heterobifunctional molecules targeting phosphorylation regulation, we highlight the current design strategies and features of these molecules. We also provide a systematic elaboration of the link between aberrantly phosphorylated targets and cancer as well as the existing challenges and future research directions for developing heterobifunctional molecular drugs for phosphorylation regulation.

γ-Secretase Cleaves Bifunctional Fatty Acid-Conjugated Small Molecules with Amide Bonds in Mammalian Cells

Connecting two small molecules, such as ligands, fluorophores, or lipids, together via a linker with amide bonds is a widely used strategy to generate synthetic bifunctional molecules for various biological and biomedical applications. Such bifunctional molecules have been used in live-cell experiments under the assumption that they should be stable in cells. However, we recently found that a membrane-targeting bifunctional molecule, composed of a lipopeptide and the small-molecule ligand trimethoprim, referred to as mgcTMP, underwent amide-bond cleavage in mammalian cells. In this work, we first identified γ-secretase as the major protease degrading mgcTMP in cells. We next investigated the intracellular degradation of several different types of amide-linked bifunctional compounds and found that N-terminally fatty acid-conjugated small molecules are susceptible to γ-secretase-mediated amide-bond cleavage. In contrast, amide-linked bifunctional molecules composed of two small molecules, such as ligands and hydrophobic groups, which lack lipid modification, did not undergo intracellular degradation. These findings highlight a previously overlooked consideration for the development and application of lipid-based bifunctional molecules in chemical biology research.

The PROTAC selectively degrading BCL-XL inhibits the growth of tumors and significantly synergizes with Paclitaxel

B-cell lymphoma extra large (BCL-XL) is an important anti-apoptotic protein of BCL-2 family. It is frequently overexpressed in various hematologic and solid tumors, often positively correlated with chemotherapy resistance in tumors. However, the clinical development of the small molecule BCL-XL inhibitor ABT-263 has been challenged on account of its on-target and dose-limiting toxicity. We have previously reported that SIAIS361034, a Proteolysis Targeting Chimera (PROTAC) specifically targeting BCL-XL to cereblon (CRBN) E3 ligase for degradation, represents a novel Hedgehog (Hh) inhibitor and inhibits tumors addiction to the Hh pathway activity with little influence on platelets. However, the inhibitory effect of SIAIS361034 on tumors independent on Hh pathway remains to be fully elucidated. In the present study, we explored its inhibitory effect on the growth of hematologic malignancies and small cell lung cancer (SCLC). Our results showed that SIAIS361034 selectively and efficiently degraded BCL-XL in tumor cells via a CRBN- and proteasome-dependent manner, with the half-maximal degradation concentration (DC50) of below 10 nM. Moreover, SIAIS361034 effectively killed BCL-XL-dependent MOLT-4 acute lymphoblastic leukemia (ALL) cells in vitro, with the half-maximal effective concentration (EC50) of 16.09 nM, and triggered apoptosis of MOLT-4 cells. SIAIS361034 obviously inhibited the growth of MOLT-4 xenografts with tumor growth inhibition rate (TGI) of 96.1 %, and did not induce acute and severe thrombocytopenia at therapeutic dosages. Furthermore, SIAIS361034 potently boosted the response of SCLC cells to Paclitaxel (PTX) and yielded more apoptosis in vitro by concurrently reduced the expression of BCL-XL and myeloid cell leukemia 1 (MCL-1), respectively. Meanwhile, we observed that SIAIS361034 significantly synergized with PTX to inhibit the growth of SCLC xenografts in vivo, without causing exacerbating PTX-induced neutropenia. Taken together, SIAIS361034, shows great potentiality in killing tumors cells, both as a monotherapy and in combination with PTX.

Role of LEDGF/p75 (PSIP1) in oncogenesis. Insights in molecular mechanism and therapeutic potential

Aberrant gene expression due to dysfunction in proteins involved in transcriptional regulation is a hallmark of tumor development. Indeed, targeting transcriptional regulators represents an emerging approach in cancer therapeutics. Lens epithelium-derived growth factor (LEDGF/p75, PSIP1) is a co-transcriptional activator that tethers several proteins to the chromatin. LEDGF/p75 has been implicated in diseases such as HIV infection and KMT2A-rearranged leukemia. Notably, LEDGF/p75 is upregulated in various human cancers including prostate and breast cancer. In this review, we discuss the essential role of LEDGF/p75 in different malignancies and explore its mechanistic contribution to tumorigenesis revealing its potential as a therapeutic target for chemotherapy.

Targeting GSK-3β for adipose dysfunction and cardiovascular complications of metabolic disease: An entangled WNT/β-catenin question

Individuals with metabolic syndrome have a high risk of developing cardiovascular disorders that is closely tied to visceral adipose tissue dysfunction, as well as an altered interaction between adipose tissue and the cardiovascular system. In metabolic syndrome, adipose tissue dysfunction is associated with increased hypertrophy, reduced vascularization, and hypoxia of adipocytes, leading to a pro-oxidative and pro-inflammatory environment. Among the pathways regulating adipose tissue homeostasis is the wingless-type mammary tumor virus integration site family (Wnt) signaling pathway, with both its canonical and non-canonical arms. Various modulators of the Wnt signaling have been identified to contribute to the development of metabolic diseases and their cardiovascular complications, with a particularly significant role played by Glycogen Synthase Kinase-3β (GSK-3β). GSK-3β levels and activities have various and often contrasting roles in obesity and related metabolic disorders, as well as their cardiovascular sequelae. Here, we explore the possibility that altered Wnt signaling and GSK-3β activities could serve as a connection between adipose tissue dysfunction and the development of cardiovascular disease in individuals with metabolic syndrome. We attempt to define a context-specific approach for intervention, which could possibly serve as a novel disease modifying therapy for the mitigation of such complications.

A new era of cancer phototherapy: mechanisms and applications

The past decades have witnessed great strides in phototherapy as an experimental option or regulation-approved treatment in numerous cancer indications. Of particular interest is nanoscale photosensitizer-based phototherapy, which has been established as a prominent candidate for advanced tumor treatment by virtue of its high efficacy and safety. Despite considerable research progress on materials, methods and devices in nanoscale photosensitizing agent-based phototherapy, their mechanisms of action are not always clear, which impedes their practical application in cancer treatment. Hence, from a new perspective, this review elaborates the working mechanisms, involving impairment and moderation effects, of diverse phototherapies on cells, organelles, organs, and tissues. Furthermore, the most current available phototherapy modalities are categorized as photodynamic, photothermal, photo-immune, photo-gas, and radio therapies in this review. A comprehensive understanding of the inferiority and superiority of various phototherapies will facilitate the advent of a new era of cancer phototherapy.

Exploiting the DCAF16-SPIN4 interaction to identify DCAF16 ligands for PROTAC development

Traditional small molecule drugs often target protein activity directly, but challenges arise when proteins lack suitable functional sites. An alternative approach is targeted protein degradation (TPD), which directs proteins to cellular machinery for proteolytic degradation. Recent studies have identified additional E3 ligases suitable for TPD, expanding the potential of this approach. Among these, DCAF16 has shown promise in facilitating protein degradation through both PROTAC and molecular glue mechanisms. In this study, we developed a homogeneous time resolved fluorescence (HTRF) assay to discover new DCAF16 binders. Using an in-house electrophile library, we identified two diastereomeric compounds, with one engaging DCAF16 at cysteines C177-179 and another reducing its expression. We demonstrated that the compound covalently engaging DCAF16 can be transformed into a PROTAC capable of degrading FKBP12.

New insights into protein-protein interaction modulators in drug discovery and therapeutic advance

Protein-protein interactions (PPIs) are fundamental to cellular signaling and transduction which marks them as attractive therapeutic drug development targets. What were once considered to be undruggable targets have become increasingly feasible due to the progress that has been made over the last two decades and the rapid technological advances. This work explores the influence of technological innovations on PPI research and development. Additionally, the diverse strategies for discovering, modulating, and characterizing PPIs and their corresponding modulators are examined with the aim of presenting a streamlined pipeline for advancing PPI-targeted therapeutics. By showcasing carefully selected case studies in PPI modulator discovery and development, we aim to illustrate the efficacy of various strategies for identifying, optimizing, and overcoming challenges associated with PPI modulator design. The valuable lessons and insights gained from the identification, optimization, and approval of PPI modulators are discussed with the aim of demonstrating that PPI modulators have transitioned beyond early-stage drug discovery and now represent a prime opportunity with significant potential. The selected examples of PPI modulators encompass those developed for cancer, inflammation and immunomodulation, as well as antiviral applications. This perspective aims to establish a foundation for the effective targeting and modulation of PPIs using PPI modulators and pave the way for future drug development.

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.

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.

Decoding β-catenin associated protein-protein interactions: Emerging cancer therapeutic opportunities

The hyperactive Wnt/β-catenin signaling circuit has been proven to be closely related to the progression of various cancers, with β-catenin serving as a central regulator of pro-tumorigenic processes. Preclinical evidences strongly support β-catenin as a promising therapeutic target. However, it has long been considered "undruggable" due to challenges such as the lack of crystal structures for its N- and C-terminal domains, high mutation rates, and limited availability of inhibitors. Notably, the network of β-catenin-associated protein-protein interactions (PPIs) is vital in the progression of multiple diseases. These interactions form a cancer-specific network that participates in all phases of oncogenesis, from cell metastasis to immunosuppressive microenvironment formation. Thus, researches on these PPIs are essential for unraveling the molecular mechanisms behind tumors with aberrant β-catenin activation, as well as for developing new targeted therapies. In this review, we delve into how β-catenin's PPIs orchestrate cancer progression and highlight biological and clinical dilemmas, proposing frontier technologies and potential challenges in targeting β-catenin for cancer therapy.

Development of natural product-based targeted protein degraders as anticancer agents

Targeted protein degradation (TPD) has emerged as a powerful approach for eliminating cancer-causing proteins through an "event-driven" pharmacological mode. Proteolysis-targeting chimeras (PROTACs), molecular glues (MGs), and hydrophobic tagging (HyTing) have evolved into three major classes of TPD technologies. Natural products (NPs) are a primary source of anticancer drugs and have played important roles in the development of TPD technology. NPs potentially expand the toolbox of TPD by providing a variety of E3 ligase ligands, protein of interest (POI) warheads, and hydrophobic tags (HyTs). As a promising direction in the TPD field, NP-based degraders have shown great potential for anticancer therapy. In this review, we summarize recent advances in the development of NP-based degraders (PROTACs, MGs and HyTing) with anticancer applications. Moreover, we put forward the challenges while presenting potential opportunities for the advancement of future targeted protein degraders derived from NPs.

Design, synthesis and biological evaluation of MNK-PROTACs

Mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs) can regulate cellular mRNA translation by controlling the phosphorylation of the eukaryotic translation initiation factor 4E (eIF4E), which plays an important role in tumor initiation, development, and metastasis. Although small-molecule MNK inhibitors have made significant breakthroughs in the treatment of various malignancies, their clinical application can be limited by drug resistance, target selectivity and other factors. The strategy of MNK-PROTACs which selectively degrades MNK kinases provides a new approach for developing small-molecule drugs for related diseases. In this study, DS33059, a small-molecule compound modified based on the ongoing clinical trials drug ETC-206, was chosen as the target protein ligand. A series of novel MNK-PROTACs were designed, synthesized and evaluated biological activity. Several compounds showed good inhibitory activities against MNK1/2. Besides, compounds exhibited moderate to excellent anti-proliferative activity in A549 and TMD-8 cells in vitro. In particular, compound II-5 significantly inhibited A549 (IC50 = 1.79 μM) and TMD-8 (IC50 = 1.07 μM) cells. The protein degradation assay showed that compound II-5 had good capability to degrade MNK1. The MNK-PROTACs strategy represents a new direction in treating tumors and deserves further exploration.

Development of PROTACs using computational approaches

Proteolysis-targeting chimeras (PROTACs) are drugs designed to degrade target proteins via the ubiquitin-proteasome system. With the application of computational biology/chemistry technique in drug design, numerous computer-aided drug design and artificial intelligence (AI)-driven drug design (CADD/AIDD) methods have recently emerged to facilitate the development of PROTAC drugs. We systematically review the role of in silico tools in PROTAC drug design, emphasizing how computational software can model PROTAC action and structure, predict activity, and assist in molecule design. We also discuss current challenges in the rational design of PROTACs from an in silico perspective, such as deviations from small-molecule druggability and the limited availability of training data. We provide an overview of recent discoveries and emerging research in this field, and discuss their potential impact on PROTAC design strategies.

Template-assisted covalent modification underlies activity of covalent molecular glues

Molecular glues are proximity-inducing small molecules that have emerged as an attractive therapeutic approach. However, developing molecular glues remains challenging, requiring innovative mechanistic strategies to stabilize neoprotein interfaces and expedite discovery. Here we unveil a trans-labeling covalent molecular glue mechanism, termed 'template-assisted covalent modification'. We identified a new series of BRD4 molecular glue degraders that recruit CUL4DCAF16 ligase to the second bromodomain of BRD4 (BRD4BD2). Through comprehensive biochemical, structural and mutagenesis analyses, we elucidated how pre-existing structural complementarity between DCAF16 and BRD4BD2 serves as a template to optimally orient the degrader for covalent modification of DCAF16Cys58. This process stabilizes the formation of BRD4-degrader-DCAF16 ternary complex and facilitates BRD4 degradation. Supporting generalizability, we found that a subset of degraders also induces GAK-BRD4BD2 interaction through trans-labeling of GAK. Together, our work establishes 'template-assisted covalent modification' as a mechanism for covalent molecular glues, which opens a new path to proximity-driven pharmacology.

Targeting glucocorticoid receptor signaling pathway for treatment of stress-related brain disorders

The hypothalamic-pituitary-adrenal (HPA) axis plays a central role in governing stress-related disorders such as major depressive disorder (MDD), anxiety, and post-traumatic stress disorder. Chronic stress or early life trauma, known risk factors of disease, alter HPA axis activity and pattern of glucocorticoid (GC) secretion. These changes have consequences for physiological processes controlled by glucocorticoid receptor (GR) signaling, such as immune response and metabolism. In the brain, the aberrant GR signaling translates to altered behavior, making the GR pathway a viable target for therapies of stress-related disorders. One of the crucial elements of the pathway is FKBP5, a regulator of GR sensitivity and feedback control within the HPA axis, in which genetic variants were shown to moderate the risk of developing psychiatric conditions. The difficulty in targeting the GR-FKBP5 pathway stems from tailoring the intervention to specific brain regions and cell types, in the context of personalized genetic variations in GR and GR-associated genes, like FKBP5. The development of selective inhibitors, antagonists, and approaches based on targeted protein degradation offer insights into mechanistic aspects of disease and pave the way for improved therapy. These strategies can be employed either independently or in conjunction with conventional medications. Concomitant advancements in personalized drug screening (e.g. in vitro models exploiting induced pluripotent stem cells, iPSCs) bring the potential for optimization of therapy aiming to rescue central deficits originating from the HPA imbalance. In this mini-review, we discuss potential therapeutic strategies targeting GR signaling in stress-related disorders, with a focus on personalized approaches and advancements in drug development.

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.

A CRISPR activation screen identifies FBXO22 supporting targeted protein degradation

Targeted protein degradation (TPD) represents a potent chemical biology paradigm that leverages the cellular degradation machinery to pharmacologically eliminate specific proteins of interest. Although multiple E3 ligases have been discovered to facilitate TPD, there exists a compelling requirement to diversify the pool of E3 ligases available for such applications. Here we describe a clustered regularly interspaced short palindromic repeats (CRISPR)-based transcriptional activation screen focused on human E3 ligases, with the goal of identifying E3 ligases that can facilitate heterobifunctional compound-mediated target degradation. Through this approach, we identified a candidate proteolysis-targeting chimera (PROTAC), 22-SLF, that induces the degradation of FK506-binding protein 12 when the transcription of FBXO22 gene is activated. Subsequent mechanistic investigations revealed that 22-SLF interacts with C227 and/or C228 in F-box protein 22 (FBXO22) to achieve target degradation. Lastly, we demonstrated the versatility of FBXO22-based PROTACs by effectively degrading additional endogenous proteins, including bromodomain-containing protein 4 and the echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase fusion protein.

Protacs in cancer therapy: mechanisms, design, clinical trials, and future directions

Cancer develops as a result of changes in both genetic and epigenetic mechanisms, which lead to the activation of oncogenes and the suppression of tumor suppressor genes. Despite advancements in cancer treatments, the primary approach still involves a combination of chemotherapy, radiotherapy, and surgery, typically providing a median survival of approximately five years for patients. Unfortunately, these therapeutic interventions often bring about substantial side effects and toxicities, significantly impacting the overall quality of life for individuals undergoing treatment. Therefore, urgent need of research required which comes up with effective treatment of cancer. This review explores the transformative role of Proteolysis-Targeting Chimeras (PROTACs) in cancer therapy. PROTACs, an innovative drug development strategy, utilize the cell's protein degradation machinery to selectively eliminate disease-causing proteins. The review covers the historical background, mechanism of action, design, and structure of PROTACs, emphasizing their precision in targeting oncogenic proteins. The discussion extends to the challenges, nanotechnology applications, and ongoing clinical trials, showcasing promising results and clinical progress. The review concludes with insights into patents, future directions, and the potential impact of PROTACs in addressing dysregulated protein expression across various diseases. Overall, it provides a concise yet comprehensive overview for researchers, clinicians, and industry professionals involved in developing targeted therapies.

Exploring Orodispersible Films Containing the Proteolysis Targeting Chimera ARV-110 in Hot Melt Extrusion and Solvent Casting Using Polyvinyl Alcohol

BACKGROUND/OBJECTIVES

This project aims to provide valuable insights into the formulation of orodispersible films (ODFs) for the delivery of PROTAC ARV-110. The primary objective of this drug delivery formulation is to enhance the solubility of PROTAC ARV-110, which faces significant challenges due to the low solubility of this active pharmaceutical ingredient, as it belongs to a molecular class that is considered to exceed the "Rule of Five".

METHODS

We employed the concept of developing a rapidly disintegrating ODF to enhance the solubility of PROTAC ARV-110, utilizing polyvinyl alcohol as the polymer of choice. Given the high thermal stability of ARV-110, the PROTAC was subjected to two primary ODF manufacturing techniques: Hot melt extrusion (HME) and solvent casting. To establish the HME method, pre-screening through vacuum compression molding was performed. The films were characterized based on their disintegration in artificial saliva, drug release in a physiological environment, and mechanical strength.

RESULTS

All formulations demonstrated enhanced solubility of ARV-110, achieving exceptional results in terms of disintegration times and resistance to applied stress.

CONCLUSIONS

The findings from the experiments outlined herein establish a solid foundation for the successful production of orodispersible films for the delivery of PROTACs.

Cereblon-recruiting proteolysis targeting chimeras (PROTACs) can determine the selective degradation of HDAC1 over HDAC3

Histone deacetylase (HDAC) enzymes 1-3 exist in several corepressor complexes and are viable drug targets. To date, proteolysis targeting chimeras (PROTACs) designed to target HDAC1-3 typically exhibit the selective degradation of HDAC3. Herein, we report cereblon-recruiting PROTACs that degrade HDAC1 with selectivity over HDAC3.

Targeting GOF p53 and c-MYC through LZK Inhibition or Degradation Suppresses Head and Neck Tumor Growth

The worldwide frequency of head and neck squamous cell carcinoma (HNSCC) is approximately 800,000 new cases, with 430,000 deaths annually. We determined that LZK (encoded by MAP3K13) is a therapeutic target in HNSCC and showed that inhibition with small molecule inhibitors decreases the viability of HNSCC cells with amplified MAP3K13. A drug-resistant mutant of LZK blocks decreases in cell viability due to LZK inhibition, indicating on-target activity by two separate small molecules. Inhibition of LZK catalytic activity suppressed tumor growth in HNSCC PDX models with amplified MAP3K13. We found that the kinase activity of LZK stabilized c-MYC and that LZK stabilized gain-of-function (GOF) p53 through a kinase-independent mechanism. Therefore, we designed proteolysis-targeting chimeras (PROTACs) and demonstrate that our lead PROTAC promotes LZK degradation and suppresses expression of GOF p53 and c-MYC leading to impaired viability of HNSCC cell lines. This research provides a strong basis for development of therapeutics targeting LZK in HNSCCs with amplification of the gene.

Conditionally Activatable Chimeras for Tumor-Specific Membrane Protein Degradation

The recent advancements on membrane protein degraders (MPDs) have broadened the applicability of proteolysis-targeting chimeras (PROTACs) beyond intracellular proteins to include the previously "undruggable" cell-surface targets. However, the potential toxicity of MPDs caused by undesired off-target degradation poses a significant challenge to clinical deployment, mirroring concerns associated with PROTACs. Here, we introduce a conditionally activatable membrane protein degrader (Pro-MPD), which leverages the specificity and high affinity of biparatopic nanobodies combined with a tumor microenvironment-activated cell-penetrating peptide (Pro-CPP) to achieve on-target activated internalization and degradation of PD-L1 within tumor sites. This modularly designed Pro-MPD demonstrated a high target degradation efficiency and T cell reactivation, as well as sustained inhibition of tumor growth in xenograft models, highlighting its potential as a safer and highly efficient MPD for in vivo applications. Our work provides a general strategy for the development of conditionally activatable MPDs, which offers a new avenue for reducing the undesired systemic toxicity of MPDs due to the off-tumor degradation.

Androgen receptor inhibitors in treating prostate cancer

ABSTRACT

Androgens play an important role in prostate cancer development and progression. Androgen action is mediated through the androgen receptor (AR), a ligand-dependent DNA-binding transcription factor. AR is arguably the most important target for prostate cancer treatment. Current USA Food and Drug Administration (FDA)-approved AR inhibitors target the ligand-binding domain (LBD) and have exhibited efficacy in prostate cancer patients, particularly when used in combination with androgen deprivation therapy. Unfortunately, patients treated with the currently approved AR-targeting agents develop resistance and relapse with castration-resistant prostate cancer (CRPC). The major mechanism leading to CRPC involves reactivation of AR signaling mainly through AR gene amplification, mutation, and/or splice variants. To effectively inhibit the reactivated AR signaling, new approaches to target AR are being actively explored. These new approaches include novel small molecule inhibitors targeting various domains of AR and agents that can degrade AR. The present review provides a summary of the existing FDA-approved AR antagonists and the current development of some of the AR targeting agents.

Conditional PROTAC: Recent Strategies for Modulating Targeted Protein Degradation

Proteolysis-targeting chimeras (PROTACs) have emerged as a promising technology for inducing targeted protein degradation by leveraging the intrinsic ubiquitin-proteasome system (UPS). While the potential druggability of PROTACs toward undruggable proteins has accelerated their rapid development and the wide-range of applications across diverse disease contexts, off-tissue effects and side-effects of PROTACs have recently received attentions to improve their efficacy. To address these issues, spatial or temporal target protein degradation by PROTACs has been spotlighted. In this review, we explore chemical strategies for modulating protein degradation in a cell type-specific (spatio-) and time-specific (temporal-) manner, thereby offering insights for expanding PROTAC applications to overcome the current limitations of target protein degradation strategy.

Discovery of MD-265: A Potent MDM2 Degrader That Achieves Complete Tumor Regression and Improves Long-Term Survival of Mice with Leukemia

MDM2 has been pursued as an attractive therapeutic target for human cancers. Herein, we describe our discovery of MD-265 as a promising PROTAC MDM2 degrader and extensive in vitro and in vivo evaluations of its therapeutic potential and mechanism of action. MD-265 effectively depleted MDM2 protein in cancer cells at concentrations as low as 1 nM, leading to strong activation of p53 in cancer cells carrying wild-type p53. It selectively inhibited the growth of wild-type p53 leukemia cell lines and showed no activity in mutated p53 lines. MD-265 achieved persistent tumor regression in a leukemia xenograft model without causing any signs of toxicity and dramatically improved survival of mice in a disseminated leukemia model even with a weekly administration. MD-265 displayed an excellent intravenous PK profile in mice, rats, and dogs. MD-265 is a promising MDM2 degrader for advanced preclinical development for the treatment of human cancers.

The Quest for Eternal Youth: Hallmarks of Aging and Rejuvenating Therapeutic Strategies

The impressive achievements made in the last century in extending the lifespan have led to a significant growth rate of elderly individuals in populations across the world and an exponential increase in the incidence of age-related conditions such as cardiovascular diseases, diabetes mellitus type 2, and neurodegenerative diseases. To date, geroscientists have identified 12 hallmarks of aging (genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, impaired macroautophagy, mitochondrial dysfunction, impaired nutrient sensing, cellular senescence, stem cell exhaustion, defective intercellular communication, chronic inflammation, and gut dysbiosis), intricately linked among each other, which can be targeted with senolytic or senomorphic drugs, as well as with more aggressive approaches such as cell-based therapies. To date, side effects seriously limit the use of these drugs. However, since rejuvenation is a dream of mankind, future research is expected to improve the tolerability of the available drugs and highlight novel strategies. In the meantime, the medical community, healthcare providers, and society should decide when to start these treatments and how to tailor them individually.

Targeted protein degradation: advances in drug discovery and clinical practice

Targeted protein degradation (TPD) represents a revolutionary therapeutic strategy in disease management, providing a stark contrast to traditional therapeutic approaches like small molecule inhibitors that primarily focus on inhibiting protein function. This advanced technology capitalizes on the cell's intrinsic proteolytic systems, including the proteasome and lysosomal pathways, to selectively eliminate disease-causing proteins. TPD not only enhances the efficacy of treatments but also expands the scope of protein degradation applications. Despite its considerable potential, TPD faces challenges related to the properties of the drugs and their rational design. This review thoroughly explores the mechanisms and clinical advancements of TPD, from its initial conceptualization to practical implementation, with a particular focus on proteolysis-targeting chimeras and molecular glues. In addition, the review delves into emerging technologies and methodologies aimed at addressing these challenges and enhancing therapeutic efficacy. We also discuss the significant clinical trials and highlight the promising therapeutic outcomes associated with TPD drugs, illustrating their potential to transform the treatment landscape. Furthermore, the review considers the benefits of combining TPD with other therapies to enhance overall treatment effectiveness and overcome drug resistance. The future directions of TPD applications are also explored, presenting an optimistic perspective on further innovations. By offering a comprehensive overview of the current innovations and the challenges faced, this review assesses the transformative potential of TPD in revolutionizing drug development and disease management, setting the stage for a new era in medical therapy.

Design of bifunctional molecules to accelerate post-translational modifications: achievements and challenges

Post-translational modifications (PTMs) of proteins are crucial for regulating biological processes and their dysregulation is linked to various diseases, highlighting PTM regulation as a significant target for drug development. Traditional drug targets often interact with multiple proteins, resulting in lower selectivity and inevitable adverse effects, which limits their clinical applicability. Recent advancements in bifunctional molecules, such as proteolysis-targeting chimeras (PROTACs), have shown promise in targeting PTMs precisely. However, regulatory mechanisms for many of the >600 known PTMs remain underexplored. This review examines current progress and challenges in designing bifunctional molecules for PTM regulation, focusing on effector selection and ligand design strategies, aiming to propel the utilization and advancement of bifunctional molecules to the forefront of PTM research.

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.

PROTACs in gynecological cancers: Current knowledge and future potential as a treatment strategy

Cancer continues to threaten human health regardless of novel therapeutic options. Over the last two decades, targeted therapy has emerged as a significant advancement in treating malignancies, surpassing standard chemoradiotherapy and surgical procedures. Gynecological malignancies, including cervical, endometrial, and ovarian carcinoma, have a bad prognosis in advanced or metastatic stages and are difficult to treat. The advancements in understanding the molecular pathways behind cancer development offer valuable insights into promising targeted medicines, and researchers have always searched for a superior and safe technique to target cancer-related oncoproteins because of the limited therapeutic benefit, drug resistance, and off-target effects of current targeted treatments. Recently, proteolysis-targeting chimeras (PROTACs) have been developed to selectively degrade proteins using the natural ubiquitin-proteasome system (UPS). These approaches have garnered significant attention in the field of cancer research. The rapid progress in PROTACs has also eased the targeting of various oncoproteins in gynecological cancer. Therefore, this review aims to elucidate the mechanism and research advancements of PROTACs and provide a comprehensive overview of their use in gynecological tumors.

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.

Scaffold hopping approaches for dual-target antitumor drug discovery: opportunities and challenges

INTRODUCTION

Scaffold hopping has emerged as a practical tactic to enrich the synthetic bank of small molecule antitumor agents. Specifically, it enables the chemist to refine the lead compound's pharmacodynamic, pharmacokinetic, and physiochemical properties. Scaffold hopping opens up fresh molecular territory beyond established patented chemical domains.

AREA COVERED

The authors present the scaffold hopping-based drug design strategies for dual inhibitory antitumor structural templates in this review. Minor modifications, structure rigidification and simplification (ring-closing and opening), and complete structural overhauls were the strategies employed by the medicinal chemist to generate a library of bifunctional inhibitors. In addition, the review presents an overview of the computational methods of scaffold hopping (software and programs) and organopalladium catalysis leveraged for the synthesis of templates designed via scaffold hopping.

EXPERT OPINION

The medicinal chemist has demonstrated remarkable prowess in furnishing dual inhibitory antitumor chemical architectures. Scaffold hopping-based drug design strategies have yielded a plethora of pharmacodynamically superior dual modulatory antitumor agents. An integrated approach involving computational advancements, synthetic methodology advancements, and conventional drug design strategies is required to increase the number of scaffold-hopping-assisted drug discovery campaigns.

Non-Markovian Dynamic Models Identify Non-Canonical KRAS-VHL Encounter Complex Conformations for Novel PROTAC Design

Targeted protein degradation (TPD) is emerging as a promising therapeutic approach for cancer and other diseases, with an increasing number of programs demonstrating its efficacy in human clinical trials. One notable method for TPD is Proteolysis Targeting Chimeras (PROTACs) that selectively degrade a protein of interest (POI) through E3-ligase induced ubiquitination followed by proteasomal degradation. PROTACs utilize a warhead-linker-ligand architecture to bring the POI (bound to the warhead) and the E3 ligase (bound to the ligand) into proximity. The resulting non-native protein-protein interactions (PPIs) formed between the POI and E3 ligase lead to the formation of a stable ternary complex, enhancing cooperativity for TPD. A significant challenge in PROTAC design is the screening of the linkers to induce favorable non-native PPIs between POI and E3 ligase. Here, we present a physics-based computational protocol to predict noncanonical and metastable PPI interfaces between an E3 ligase and a given POI, aiding in the design of linkers to stabilize the ternary complex and enhance degradation. Specifically, we build the non-Markovian dynamic model using the Integrative Generalized Master equation (IGME) method from ∼1.5 ms all-atom molecular dynamics simulations of linker-less encounter complex, to systematically explore the inherent PPIs between the oncogene homologue protein and the von Hippel-Lindau E3 ligase. Our protocol revealed six metastable states each containing a different PPI interface. We selected three of these metastable states containing promising PPIs for linker design. Our selection criterion included thermodynamic and kinetic stabilities of PPIs and the accessibility between the solvent-exposed sites on the warheads and E3 ligand. One selected PPIs closely matches a recent cocrystal PPI interface structure induced by an experimentally designed PROTAC with potent degradation efficacy. We anticipate that our protocol has significant potential for widespread application in predicting metastable POI-ligase interfaces that can enable rational design of PROTACs.

Advancing Proteolysis Targeting Chimera (PROTAC) Nanotechnology in Protein Homeostasis Reprograming for Disease Treatment

Proteolysis targeting chimeras (PROTACs) represent a transformative class of therapeutic agents that leverage the intrinsic protein degradation machinery to modulate the hemostasis of key disease-associated proteins selectively. Although several PROTACs have been approved for clinical application, suboptimal therapeutic efficacy and potential adverse side effects remain challenging. Benefiting from the enhanced targeted delivery, reduced systemic toxicity, and improved bioavailability, nanomedicines can be tailored with precision to integrate with PROTACs which hold significant potential to facilitate PROTAC nanomedicines (nano-PROTACs) for clinical translation with enhanced efficacy and reduced side effects. In this review, we provide an overview of the recent progress in the convergence of nanotechnology with PROTAC design, leveraging the inherent properties of nanomaterials, such as lipids, polymers, inorganic nanoparticles, nanohydrogels, proteins, and nucleic acids, for precise PROTAC delivery. Additionally, we discuss the various categories of PROTAC targets and provide insights into their clinical translational potential, alongside the challenges that need to be addressed.

Discovery of Novel PROTAC SIRT6 Degraders with Potent Efficacy against Hepatocellular Carcinoma

Sirtuin 6 (SIRT6), a member of the SIRT family, plays essential roles in the regulation of metabolism, inflammation, aging, DNA repair, and cancer development, making it a promising anticancer drug target. Herein, we present our use of proteolysis-targeting chimera (PROTAC) technology to formulate a series of highly potent and selective SIRT6 degraders. One of the degraders, SZU-B6, induced the near-complete degradation of SIRT6 in both SK-HEP-1 and Huh-7 cell lines and more potently inhibited hepatocellular carcinoma (HCC) cell proliferation than the parental inhibitors. In preliminary mechanistic studies, SZU-B6 hampered DNA damage repair, promoting the cellular radiosensitization of cancer cells. Our SIRT6 degrader SZU-B6 displayed promising antitumor activity, particularly when combined with the well-known kinase inhibitor sorafenib or irradiation in an SK-HEP-1 xenograft mouse model. Our results suggest that these PROTACs might constitute a potent therapeutic strategy for HCC.

Toosendanin: upgrade of an old agent in cancer treatment

Toosendanin (TSN), a tetracyclic triterpenoid derived from Melia toosendan and M. azedarach, demonstrates broad application prospects in cancer treatment. Although previously employed as a pesticide, recent studies have revealed its potential therapeutic value in treating various types of cancer. TSN exerts an anticancer effect via mechanisms including proliferation inhibition, apoptosis induction, migration suppression, and angiogenesis inhibition. However, TSN's toxicity, particularly its hepatotoxicity, significantly limits its therapeutic application. This review explored the dual nature of TSN, evaluating both its anticancer potential and toxicological risks, emphasizing the importance of balancing these aspects in therapeutic applications. Furthermore, we investigated the incorporation of TSN into novel therapeutic strategies, such as Proteolysis-targeting chimeras (PROTAC) technology and nanotechnology-based drug delivery systems (DDS), which enhance treatment efficacy while mitigating toxicity in normal tissues.

Penfluridol inhibits melanoma growth and metastasis through enhancing von Hippel‒Lindau tumor suppressor-mediated cancerous inhibitor of protein phosphatase 2A (CIP2A) degradation

Melanoma's high metastatic potential, especially to the brain, poses significant challenges to patient survival. The blood‒brain barrier (BBB) is a major obstacle to the effective treatment of melanoma brain metastases. We screened antipsychotic drugs capable of crossing the BBB and identified penfluridol (PF) as the most active candidate. PF reduced melanoma cell viability and induced apoptosis. In animal models, PF effectively inhibited melanoma growth and metastasis to the lung and brain. Using immunoprecipitation combined with high-resolution mass spectrometry, and other techniques such as drug affinity responsive target stability, we identified CIP2A as a direct binding protein of PF. CIP2A is highly expressed in melanoma and its metastases, and is linked to poor prognosis. PF can restore Protein Phosphatase 2A activity by promoting CIP2A degradation, thereby inhibiting several key oncogenic pathways, including AKT and c-Myc. Additionally, von Hippel‒Lindau (VHL) is the endogenous E3 ligase for CIP2A, and PF enhances the interaction between VHL and CIP2A, promoting the ubiquitin‒proteasome degradation of CIP2A, thereby inhibiting melanoma growth and metastasis. Overall, this study not only suggests PF's potential in treating melanoma and its brain metastases but also highlights CIP2A degradation as a therapeutic strategy for melanoma.