Targeted delivery of PROTAC-based prodrug activated by bond-cleavage bioorthogonal chemistry for microneedle-assisted cancer therapy

Drugtamer-PROTAC Conjugation Strategy for Targeted PROTAC Delivery and Synergistic Antitumor Therapy

Proteolysis-targeting chimeras (PROTACs) have emerged as a promising strategy for targeted protein degradation and drug discovery. To overcome the inherent limitations of conventional PROTACs, an innovative drugtamer-PROTAC conjugation approach is developed to enhance tumor targeting and antitumor potency. Specifically, a smart prodrug is designed by conjugating "drugtamer" to a nicotinamide phosphoribosyltransferase (NAMPT) PROTAC using a tumor microenvironment responsible linker. The "drugtamer" consists of fluorouridine nucleotide and DNA-like oligomer. Compared to NAMPT PROTAC and the combination of PROTAC + fluorouracil, the designed prodrug AS-2F-NP demonstrates superior tumor targeting, efficient cellular uptake, improved in vivo potency and reduced side effects. This study provides a promising strategy for the precise delivery of PROTAC and synergistic antitumor agents.

Bromodomain and Extraterminal Domain Protein 2 in Multiple Human Diseases

Bromodomain and extraterminal domain protein 2 (BRD2), a member of the bromodomain and extraterminal domain (BET) protein family, is a crucial epigenetic regulator with significant function in various diseases and cellular processes. The central function of BRD2 is modulating gene transcription by binding to acetylated lysine residues on histones and transcription factors. This review highlights key findings on BRD2 in recent years, emphasizing its roles in maintaining genomic stability, influencing chromatin spatial organization, and participating in transcriptional regulation. BRD2's diverse functions are underscored by its involvement in diseases such as malignant tumors, neurologic disorders, inflammatory conditions, metabolic diseases, and virus infection. Notably, the potential role of BRD2 as a diagnostic marker and therapeutic target is discussed in the context of various diseases. Although pan inhibitors targeting the BET family have shown promise in preclinical studies, a critical need exists for the development of highly selective BRD2 inhibitors. In conclusion, this review offers insights into the multifaceted nature of BRD2 and calls for continued research to unravel its intricate mechanisms and harness its therapeutic potential. SIGNIFICANCE STATEMENT: BRD2 is involved in the occurrence and development of diseases through maintaining genomic stability, influencing chromatin spatial organization, and participating in transcriptional regulation. Targeting BRD2 through protein degradation-targeting complexes technology is emerging as a promising therapeutic approach for malignant cancer and inflammatory diseases.

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

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

Selective Elimination of Senescent Cancer Cells by Galacto-Modified PROTACs

Although the selective and effective clearance of senescent cancer cells can improve cancer treatment, their development is confronted by many challenges. As part of efforts designed to overcome these problems, prodrugs, whose design is based on senescence-associated β-galactosidase (SA-β-gal), have been developed to selectively eliminate senescent cells. However, chemotherapies relying on targeted molecular inhibitors as senolytic drugs can induce drug resistance. In the current investigation, we devised a new strategy for selective degradation of target proteins in senescent cancer cells that utilizes a prodrug composed of the SA-β-gal substrate galactose (galacto) and the proteolysis-targeting chimeras (PROTACs) as senolytic agents. Prodrugs Gal-ARV-771 and Gal-MS99 were found to display senolytic indexes higher than those of ARV-771 and MS99. Significantly, results of in vivo studies utilizing a human lung A549 xenograft mouse model demonstrated that concomitant treatment with etoposide and Gal-ARV-771 leads to a significant inhibition of tumor growth without eliciting significant toxicity.

Targeted Protein Degraders- The Druggability Perspective

Targeted Protein degraders (TPDs) show promise in harnessing cellular machinery to eliminate disease-causing proteins, even those previously considered undruggable. Especially if protein turnover is low, targeted protein removal bestows lasting therapeutic effect over typical inhibition. The demonstrated safety and efficacy profile of clinical candidates has fueled the surge in the number of potential candidates across different therapeutic areas. As TPDs often do not comply with Lipinski's rule of five, developing novel TPDs and unlocking their full potential requires overcoming solubility, permeability and oral bioavailability challenges. Tailored in-vitro assays are key to precise profiling and optimization, propelling breakthroughs in targeted protein degradation.

Nano-PROTACs: state of the art and perspectives

PROteolysis TArgeting Chimeras (PROTACs), as a recently identified technique in the field of new drug development, provide new concepts for disease treatment and are expected to revolutionize drug discovery. With high specificity and flexibility, PROTACs serve as an innovative research tool to target and degrade disease-relevant proteins that are not currently pharmaceutically vulnerable to eliminating their functions by hijacking the ubiquitin-proteasome system. To date, PROTACs still face the challenges of low solubility, poor permeability, off-target effects, and metabolic instability. The combination of nanotechnology and PROTACs has been explored to enhance the in vivo performance of PROTACs regarding overcoming these challenging hurdles. In this review, we summarize the latest advancements in the building-block design of PROTAC prodrug nanoparticles and provide an overview of existing/potential delivery systems and loading approaches for PROTAC drugs. Furthermore, we discuss the current status and prospects of the split-and-mix approach for PROTAC drug optimization. Additionally, the advantages and translational potentials of carrier-free nano-PROTACs and their combinational therapeutic effects are highlighted. This review aims to foster a deeper understanding of this rapidly evolving field and facilitate the progress of nano-PROTACs that will continue to push the boundaries of achieving selectivity and controlled release of PROTAC drugs.

Aggregation-induced emission photosensitizer microneedles for enhanced melanoma photodynamic therapy

The incidence and mortality rates of skin melanoma have been increasing annually. Photodynamic therapy (PDT) enables effective destruction of tumor cells while minimizing harm to normal cells. However, traditional photosensitizers (PSs) suffer from photobleaching, photodegradation and the aggregation-caused quenching (ACQ) effect, and it is challenging for light to reach the deep layers of the skin to maximize the efficacy of PSs. Herein, we developed dissolving microneedles (MNs) loaded with PSs of TPE-EPy@CB[7] through supramolecular assembly. The PSs effectively enhanced the type-I reactive oxygen species (ROS) generation capacity, with a concentration of 2 μM possessing nearly half of the tumor cell-killing ability under 10 min white light irradiation. The MNs were successfully pierced into the targeted site for precise drug delivery. Additionally, the conical structure of the MNs, as well as the lens-like structure after dissolution, facilitated the transmission of light in the subcutaneous tissue, achieving significant inhibition of tumor growth with a tumor suppression rate of 97.8% and no systemic toxicity or side effects in melanoma mice. The results demonstrated the potent melanoma inhibition and biosafety of this treatment approach, exhibiting a new and promising strategy to conquer malignant melanoma.